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BACKGROUND: The first aim of this study was to evaluate the capacity of electrical impedance tomography (EIT) to identify the effect of PEEP on regional ventilation distribution and the regional risk of collapse, overdistention, hypoventilation, and pendelluft in mechanically ventilated patients. The second aim was to evaluate the feasibility of EIT for estimating airway opening pressure (AOP). METHODS: The EIT signal was recorded both during baseline cyclic ventilation and slow insufflation for one breath for 9 subjects with moderate-to-severe ARDS. From these data, the AOP and volumes insufflated to lung regions with or without the risk of either collapse, overdistention, hypoventilation, or pendelluft were assessed at 3 PEEP levels (5, 10, and 15 cm H2O). PEEP levels were compared by Friedman analysis of variance and the AOP measured by EIT evaluated using an F-test and the Bland and Altman method. RESULTS: The volume for which there was no specific risk significantly decreased at the highest PEEP from 55 ± 31% tidal volume (VT) at PEEP = or 82 ± 18% VT at PEEP 10 to 10 ± 30% VT at PEEP 15 (P = .038 between PEEP 5 vs PEEP 15; P = .01 between PEEP 10 vs PEEP 15). The volume associated with overdistention significantly increased with increasing PEEP, whereas that associated with atelec-trauma significantly decreased. Pendelluft significantly decreased with increasing PEEP: VT of 8.9 ± 18.6%, 3.6 ± 7.0%, and 3.2 ± 7.1% for PEEP 5, PEEP 10, and PEEP 15, respectively. The center of ventilation tended to increase in the dependent direction with higher PEEP. The AOPs assessed by EIT and from the pressure-volume curve were in good agreement (bias 0.48 cm H2O). CONCLUSIONS: Our results suggest that EIT could aid clinicians in making personalized and reasoned choices in setting the PEEP for subjects with ARDS. [ABSTRACT FROM AUTHOR]

BACKGROUND: The spontaneous breathing trial (SBT) is the final step of weaning from invasive mechanical ventilation. An SBT is aimed at predicting work of breathing (WOB) after extubation and, most importantly, a patient's eligibility for extubation. The optimal SBT modality remains debated. A high-flow oxygen (HFO) has been tested during SBT in clinical study only, which is why no definite conclusion can be drawn on its physiologic effects on the endotracheal tube. Our objective was to assess, on a bench, inspiratory tidal volume (VT), total PEEP, and WOB across 3 different SBT modalities: T-piece, 40 L/min HFO, and 60 L/min HFO. METHODS: A test lung model was set with 3 conditions of resistance and linear compliance, 3 inspiratory efforts (low, normal, and high), each at 2 breathing frequencies (low and high for 20 and 30 breaths/min, respectively). Pairwise comparisons and a quasi-Poisson generalized linear model that compared SBT modalities were performed. RESULTS: Inspiratory VT, total PEEP, and WOB differed from one SBT modality to another. Inspiratory VT remained higher with the T-piece than in the HFO independent of the mechanical condition, effort intensity, and breathing frequency (P < .001 in each comparison). WOB adjusted by the inspiratory VT was significantly lower during SBT performed with an HFO than when performed with the T-piece (P < .001 in each comparison). The total PEEP was significantly higher in the HFO at 60 L/min than in the other modalities (P < .001). The end points were significantly influenced by breathing frequency, effort intensity, and mechanical condition. CONCLUSIONS: With the same effort intensity and breathing frequency, inspiratory VT was higher in the T-piece than in the other modalities. Compared with the T-piece, WOB was significantly lower in the HFO condition and higher flow was a benefit. Based on the results of the present study, the HFO as an SBT modality would seem to require clinical testing. [ABSTRACT FROM AUTHOR]

BACKGROUND: Mechanical insufflation-exsufflation (MI-E) devices are used to improve airway clearance in individuals with acute respiratory failure. Some MI-E devices measure cough peak flow (CPF) during MI-E to optimize pressure adjustments. The aim was to compare CPF and effective cough volume (ECV: volume expired/coughed > 3 L/s) measurements between 4 MI-E devices under simulated conditions of stable versus collapsed airway. METHODS: Four MI-E devices were tested on the bench. Each device was connected via a standard circuit to a collapsible tube placed in an airtight chamber that was attached to a lung model with adjustable compliance and resistance. Pressure was measured upstream and downstream the collapsing tube; air flow was measured between the chamber and the lung model. Each device was tested in 2 conditions: collapse condition (0 cm H2O) and no-collapse condition (-70 cm H2O). For each condition, 6 combinations of inspiratory/expiratory pressures were applied. CPF was measured at the "mouth level" by the device built-in flow meter and at the "tracheal level" by a dedicated pneumotachograph. Comparisons were performed with non-parametric tests. RESULTS: CPF values measured at the tracheal level and ECV values differed between devices for each inspiratory/ expiratory pressure in the collapse and no-collapse conditions (P < .001). CPF values were significantly lower at the tracheal level in the collapse as compared with the no-collapse condition (P < .001 for each device), whereas they were higher at the mouth level (P < .05) for 3 of the 4 devices. CONCLUSIONS: CPF values differed significantly across MI-E devices, highlighting limitation(s) of using only CPF values to determine cough effectiveness. In simulated of airway collapse, CPF increased at the mouth, whereas it decreased at the tracheal level. [ABSTRACT FROM AUTHOR]

BACKGROUND: Automatic tube compensation (ATC) is an option available in any ICU ventilator that compensates for the resistive pressure drop due to the endotracheal tube by providing flow assistance. The goal of the present study was to compare ATC to other patient triggered modes of support in terms of spontaneous breathing trial (SBT) and extubation success. METHODS: Two authors (JB and PCF), independently and blinded to each other, searched through PubMed, Web of Science, and Cochrane from inception--May 26, 2021, with the following search terms entered as MeSH terms in all fields: "Automatic Tube Compensation." Inclusion criteria: randomized studies that included subjects > 16 y old undergoing an SBT. Exclusion criteria: crossover studies, pediatric studies, animal studies, or experimental studies on test lungs or on computer simulation; other languages than French, Spanish, or English; studies not published in a full-text format (eg, abstract or letter); and reviews. A frequentist network meta-analysis was conducted with the aim to investigate the effectiveness of ATC on SBT and extubation outcomes. SBT was defined as successful if patients could tolerate the SBT based on predetermined criteria, whether it was followed by extubation. Successful extubation was defined as the absence of re-intubation, noninvasive ventilation, or signs of respiratory distress within the 48 h after extubation. The pooled analyses used random-effect models, and the effect size was expressed as relative risk or mean difference for categorical and continuous variables, respectively. P-scores were used to rank all treatments and to identify the intervention with the highest probability of being the best. RESULTS: Of the 234 retrieved papers, 7 met the inclusion criteria. In terms of SBT success, ATC100+PEEP < 7.5 and PS10+PEEP < 7.5 were superior to T-piece. Likewise, PS10+PEEP < 7.5 was the intervention with the highest probability of being the best (P-score: 0.90). In terms of extubation success, ATC100+PEEP < 7.5 cm H2O was significantly better than PEEP < 7.5 and T-piece. Likewise, it had the highest probability of being the best (P-score= 0.90). CONCLUSIONS: ATC is the modality with the highest probability of being the best in terms of extubation success but not in terms of SBT success. [ABSTRACT FROM AUTHOR]

The article considers a study which evaluated lightweight ventilatory assist device as a step forward to help patients with chronic obstructive pulmonary disease (COPD) to perform ambulatory exercises. It suggests a personalized medicine approach to identify patients most likely to benefit from treatment, including those with physical limitations. Emphasis is given on the importance of assessing results of the therapy on longer periods.

BACKGROUND: Oxygen therapy via high-flow nasal cannula (HFNC) has been extensively used during the COVID-19 pandemic. The number of devices has also increased. We conducted this study to answer the following questions: Do HFNC devices differ from the original device for work of breathing (WOB) and generated PEEP? METHODS: Seven devices were tested on ASL 5000 lung model. Compliance was set to 40 mL/cm H2O and resistance to 10 cm H2O/L/s. The devices were connected to a manikin head via a nasal cannula with F... set at 0.21. The measurements were performed at baseline (manikin head free of nasal cannula) and then with the cannula and the device attached with oxygen flow set at 20, 40, and 60 L/min. WOB and PEEP were assessed at 3 simulated inspiratory efforts (-5, -10, -15 cm H2O muscular pressure) and at 2 breathing frequencies (20 and 30 breaths/min). Data were expressed as median (first-third quartiles) and compared with nonparametric tests to the Optiflow device taken as reference. RESULTS: Baseline WOB and PEEP were comparable between devices. Over all the conditions tested, WOB was 4.2 (1.0-9.4) J/min with the reference device, and the relative variations from it were 0, -3 (2-4), 1 (0-1), -2 (1-2), -1 (1-2), and -1 (1-2)% with Airvo 2, G5, HM80, T60, V500, and V60 Plus devices, respectively, (P < .05 Kruskal-Wallis test). PEEP was 0.9 (0.3-1.5) cm H2O with Optiflow, and the relative differences were -28 (22-33), -41 (38-46), -30 (26-36), -31 (28-34), -37 (32-42), and -24 (21-34)% with Airvo 2, G5, HM80, T60, V500, and V60 Plus devices, respectively, (P < .05 Kruskal-Wallis test). CONCLUSIONS: WOB was marginally higher and PEEP marginally lower with devices as compared to the reference device. [ABSTRACT FROM AUTHOR]

BACKGROUND: Patients with neuromuscular disorders (NMD) share the risk of acute respiratory failure (ARF) leading to ICU admissions. Noninvasive ventilation (NIV) is often proposed as an alternative to invasive ventilation. This study describes clinical features, ventilation management, and outcomes of subjects with NMD admitted to ICU and managed for ARF. METHODS: We performed a multicenter retrospective study in 7 adult ICUs in the Auvergne-Rhone-Alpes area in France involving subjects with NMD admitted to the ICU for ARF. The primary end point was ICU mortality. Secondary end points were NIV failure, weaning from invasive ventilation, and long-term mortality. We hypothesized a poorer outcome in the case of bulbar musculature involvement. RESULTS: A total of 242 subjects were included; 142 subjects had nonhereditary NMD (58.7%), and 100 had hereditary NMD (41.3%). Eleven subjects had home ventilation through a tracheostomy. While 112 were intubated at admission, 119 initially underwent NIV. NIV was successful in avoiding orotracheal intubation in 78 subjects (65.5%). ICU mortality was 13.6%. Factors associated with ICU mortality were nonhereditary NMD and requirement for invasive ventilation. The involvement of bulbar musculature in ARF and hereditary NMD were associated with NIV failure. After a median follow-up of 1.2 y, 53 of 209 subjects had died. CONCLUSIONS: The ICU mortality of NMD subjects with ARF was low, with no impact of bulbar muscles involvement. NIV was proposed for approximately half of the subjects, and it was more effective when ARF was not attributed to bulbar musculature involvement. The long-term outcome was good. [ABSTRACT FROM AUTHOR]

BACKGROUND: We hypothesized that the lack of benefit of setting a low versus a high PEEP in patients with ARDS may be due in part to differences in the dynamic behavior of the expiratory valve in ventilators. We tested this hypothesis by conducting a bench comparison of the dynamic behavior of expiratory valves on ICU ventilators currently in use. METHODS: We attached 7 ICU ventilators (C5, C6, Carescape, PB980, ServoU, V500, and V680) to the ASL 5000 lung model (passive condition with compliance 20 mL/cm H2O and resistance 5 cm H2O/L/s) and set in volume controlled mode (tidal volume 0.8 L, breathing frequency 10 breaths/min). Flow and pressure were measured just before the exhalation valve. At PEEP of 5, 10, and 15 cm H2O, the median instantaneous expiratory resistance, the time to valve opening, and the pressure time products above or below the values of PEEP (expressed in cm H2O x s) were determined. RESULTS: Median instantaneous expiratory resistance values differed between the ventilators and PEEP settings with a significant interaction: at PEEP 5 cm H2O, the median (interquartile range) expiratory resistance values were 3.9 (3.5-4.7), 3.0 (3.0-3.1), 20.9 (15.8-24.9), 27.4 (26.5-43.2), 13.8 (13.6-13.9), 4.4 (4.0-4.6), and 34.3 (33.7-33.8) cm H2O/L/s, for the C5, C6, Carescape, PB980, ServoU, V500, and V680, respectively. For all the PEEP settings, the corresponding times to valve opening were 0.080 (0.077-0.082), 0.082 (0.080-0.085), 0.110 (0.105-0.110), 0.100 (0.085-1.05), 0.072 (0.062-0.072), 0.145 (0.115-0.150), and 0.075 (0.070-0.080) s, respectively, and pressure-time products were 2.8 (2.1-7.4), 6.8 (6.7-7.3), 2.4 (2.1-2.4), 3.5 (2.7-3.6), 1.8 (1.8-2.1), 2.8 (2.7-2.9), and 5.7 (5.4-5.9) cm H2O x s, respectively. CONCLUSIONS: The resistance of active expiratory valves differed significantly between the 7 ICU ventilators tested. [ABSTRACT FROM AUTHOR]

BACKGROUND: Automatic tube compensation (ATC) unloads endotracheal tube (ETT) resistance. We conducted a bench assessment of ATC functionality in ICU ventilators to improve clinical management. METHODS: This study had 2 phases. First, we performed an international survey on the use of ATC in clinical practice, hypothesizing a rate of ATC use of 25%. Second, we tested 7 modern ICU ventilators in a lung model mimicking a normal subject (Normal), a subject with ARDS, and a subject with COPD. Inspiratory effort consisted of esophageal pressure over 30 consecutive breaths obtained in a real patient under weaning. A brand new 8-mm inner diameter ETT was attached to the lung model, and ATC was set at 100% compensation for the ETT. The 30 breaths were first run with ATC off and no ETT (ie, reference period), and then with ATC on and ETT (ie, active period). The primary end point was the difference in tidal volume (VT) between reference and active periods. We hypothesized that the VT difference should be equal to 0 in an ideally functioning ATC. VT difference was compared across ventilators and respiratory mechanics conditions using a linear mixed-effects model. RESULTS: The clinical use of ATC was 64% according to 644 individuals who responded to the international survey. The VT difference varied significantly across ventilators in all respiratory mechanics configurations. The divergence between VT difference and 0 was small but significant: the extreme median (interquartile range) values were -0.013 L (-0.019 to -0.002) in the COPD model and 0.056 L (0.051-0.06) in the Normal model. VT difference for all ventilators was 0.015 L (95% CI 0.013-0.018) in the ARDS model, which was significantly different from 0.021 L (95% CI 0.018-0.024) in the Normal model (P < .001) and 0.010 L (0.007-0.012) in the COPD model (P = .003). CONCLUSIONS: ATC is used more frequently in clinical practice than expected. In addition, VT delivery by ATC differed slightly though significantly between ventilators. [ABSTRACT FROM AUTHOR]

BACKGROUND: Obesity-hypoventilation syndrome (OHS) is defined as the combination of obesity (body mass index ≥ 30 kg/m²) and daytime arterial hypercapnia (PaCO2 > 45 mm Hg) in the absence of other causes of hypoventilation, and can lead to acute hypercapnic respiratory failure in the ICU. Our objective was to describe the ventilatory management and outcomes of subjects with OHS who were admitted to the ICU for acute hypercapnic respiratory failure. METHODS: We retrospectively built a cohort of subjects with OHS who were admitted for acute hypercapnic respiratory failure in 4 ICUs of the university teaching hospital in Lyon, France, between 2013 and 2017. The main end point was the rate of success of noninvasive ventilation (NIV). Secondary end points were survival from OHS diagnosis to the last follow-up and risk factors for ICU admission and long-term survival. RESULTS: One hundred fifteen subjects with OHS were included. Thirty- seven subjects (32.1%) were admitted to the ICU for acute hypercapnic respiratory failure. Con- gestive heart failure was the leading cause of acute hypercapnic respiratory failure (54%). At ICU admission, pH before NIV use was median (range) 7.26 (7.22-7.31) and ... was 70 (61-76) mm Hg. NIV was used as first-line ventilatory support in 36 subjects (97.2%) and was successful in 33 subjects (91.7%). ICU mortality was low (2.7%). The subjects admitted to the ICU were significantly older and had a lower FEV1 and vital capacity at the time of an OHS diagnosis. The difference in the restricted mean survival time was 663 d in favor of subjects not admitted to the ICU. Multivariate analysis showed that lower vital capacity at an OHS diagnosis was significantly associated with a higher risk of ICU admission. No factor was independently associated with long-term overall mortality in multivariate analysis. CONCLUSIONS: Acute hypercapnic respiratory failure in subjects with OHS was generally responsive to NIV and was frequently associated with congestive heart failure. [ABSTRACT FROM AUTHOR]

BACKGROUND: Collapsibility of upper airways may impair the efficacy of mechanical insufflation-exsufflation (MI-E) devices. The aim of this study was to determine the effect of a collapsible tube on peak expiratory flow (PEF) when using an MI-E device. METHODS: An MI-E device was attached to a lung simulator. Resistance was set at 5 and 20 cm H2O/L/s (R5, R20) for compliance settings of 20, 40, and 60 mL/cm H2O (C20, C40, C60). A series of 5 cycles were delivered at 3 pressures in the following order: +30/-30, +40/-40, and +50/-50 cm H2O for each compliance/resistance combination with and without the collapsible tube. Each respiratory mechanics profile was tested in random order. Pressure and flow were measured upstream of the MI-E device, and the primary outcome measure was PEF. The relationships of PEF to maximum expiratory pressure were compared with and without the collapsible tube using a linear regression model. RESULTS: For the C20-R5 condition, the effect of the collapsible tube on the intercept (-0.35 cm H2O) was not significant, but this was offset by a significant (and the largest) increase in slope (+0.12 L/s/cm H2O). For the C60-R20 condition, the effect of the collapsible tube on the slope (-0.003 L/s/cm H2O) was not significant, but this was offset by a significant (and the largest) increase of the intercept (+3.16 cm H2O) at 30 cm H2O expiratory pressure. For the other conditions, the collapsible tube significantly increased PEF at 30 cm H2O expiratory pressure, and the gap further increased above this pressure as the slope increased with the collapsible tube. CONCLUSIONS: The collapsible tube resulted in a higher PEF for all respiratory mechanics profiles tested. [ABSTRACT FROM AUTHOR]

BACKGROUND: Remote monitoring is increasingly used in patients who receive home mechanical ventilation. The average volume assured pressure support mode is a target volume pressure preset mode that delivers a given tidal volume (VT) within a range of controlled inspiratory pressures. In a mode such as this, it is important to verify that the VT value retrieved from the ventilator SD card is accurate. METHODS: A lung model was set with C (Compliance) 0.075 L/cm H2O and RI (Inspiratory resistance)-RE (Expiratory resistance) 15-25 cmH2O/L/s (model 1) or with C0.050 L/cm H2O and RI 6 cm H2O/L/s (model 2) and 6 cm H2O effort. Three home-care ventilators (A40, PrismaST30, and Vivo40) were set to average volume assured pressure support mode with 0.3 and 0.6 L VT each at PEEP 5 and 10 cm H2O, and were connected to the lung model with and without nonintentional leak. The reference airway pressure and flow were measured by a data logger. VT was expressed in body temperature and pressure saturated. We assessed the difference in VT between the ventilator SD card and a data logger relative to set VT and factors associated with its magnitude. RESULTS: For A40, PrismaST30, and Vivo40, the adjusted mean VT differences between the ventilator SD card and the data logger were -0.053 L (95% CI -0.067 to -0.039 L) (P < .001), -0.002 L (95%CI -0.022 to 0.019 L) (P = .86), and -0.067 L (95% CI -0.007 to 0.127 L) (P = .03), respectively. The partial Spearman correlation coefficients between the ventilator SD card and a data logger were 0.89 (P < .001), 0.59 (P < .001), and 0.78 (P < .001), respectively to the ventilators. The relative variations in measured VT from the set VT were 16.0, -12.0, and 6.7% for the ventilator SD card, and were -2.5, -7.5, and -27.2% for the data logger, respectively. The discrepancy in ventilator between SD card and data logger were influenced by PEEP for the PrismaST30 ventilator, nonintentional leak for the Vivo40 ventilator and PEEP, nonintentional leak, and underlying disease, the effect of each depending on the levels of the other factors, for the A40 ventilator. CONCLUSIONS: In the 3 home-care ventilators, the ventilator SD card underestimated VT. Factors involved in this difference differed among the ventilators. [ABSTRACT FROM AUTHOR]

BACKGROUND: Successful weaning from mechanical ventilation depends on the patient's ability to cough efficiently. Cough peak flow (CPF) could predict extubation success using a dedicated flow meter but required patient disconnection. We aimed to predict extubation outcome using an overall model, including cough performance assessed by a ventilator flow meter. METHODS: This was a prospective observational study conducted from November 2014 to October 2015. Before and after a spontaneous breathing trial, subjects were encouraged to cough as strongly as possible before freezing the ventilator screen to assess CPF and tidal volume (VT) in the preceding inspiration. Early extubation success rate was defined as the proportion of subjects not re-intubated 48 h after extubation. Diagnostic performance of CPF and VT was assessed by using the area under the curve of the receiver operating characteristic curve. Cut-off values for CPF and VT were defined according to median values and used to describe the performance of a predictive test combining them with risk factors of early extubation failure. RESULTS: Among 673 subjects admitted, 92 had a cough assessment before extubation. For the 81 subjects with early extubation success, the median CPF was -67.7 L/min, and median VT was 0.646 L. For the 11 subjects with early extubation failure, the median CPF was -57.3 L/min, and median VT was 0.448 L. Area under the curve was 0.61 (95% CI 0.37-0.83) for CPF and 0.64 (95% CI 0.42-0.84) for CPF/VT combined. After dichotomization (CPF < -60 L/min or VT > 0.55 L), there was a synergistic effect to predict early extubation success (P < .001). The predictive value of success reached 94.2% for CPF/V T combined. The overall model including pH before extubation < 7.45 reached a 66.7% predictive value of failure. CONCLUSIONS: CPF measured using the flow meter of an ICU ventilator was able to predict extubation success and to build a composite score to predict extubation failure. The results were close to that found in previous studies that used a dedicated flow meter. This could help to identify high-risk subjects to prevent extubation failure. [ABSTRACT FROM AUTHOR]

BACKGROUND: Limiting tidal volume (VT) in patients with ARDS may not be achieved once patient-triggered breaths occur. Furthermore, ICU ventilators offer numerous patient-triggered modes that work differently across brands. We systematically investigated, using a bench model, the effect of patient-triggered modes on the size and variability of VT at different breathing frequencies (f), patient effort, and ARDS severity. METHODS: We used a V500 Infinity ICU ventilator connected to an ASL 5000 lung model whose compliance was mimicking mild, moderate, and severe ARDS. Thirteen patient-triggered modes were tested, falling into 3 categories, namely volume control ventilation with mandatory minute ventilation; pressure control ventilation, including airway pressure release ventilation (APRV); and pressure support ventilation. Two levels of f and effort were tested for each ARDS severity in each mode. Median (first-third quartiles) VT was compared across modes using non-parametric tests. The probability of VT > 6 mL/kg ideal body weight was assessed by binomial regression and expressed as the odds ratio (OR) with 95% CI. VT variability was measured from the coefficient of variation. RESULTS: VT distribution over all f, effort, and ARDS categories significantly differed across modes (P < .001, Kruskal-Wallis test). VT was significantly greater with pressure support (OR 420 mL, 95% CI 332-527 mL) than with any other mode except for variable pressure support level. Risk for VT to be > 6 mL/kg was significantly increased with spontaneous breaths patient-triggered by pressure support (OR 19.36, 95% CI 12.37-30.65) and significantly reduced in APRV (OR 0.44, 95% CI 0.26-0.72) and pressure support with guaranteed volume mode. The risk increased with increasing effort and decreasing f. Coefficient of variation of VT was greater for low f and volume control-mandatory minute ventilation and pressure control modes. APRV had the greatest within-mode variability. CONCLUSIONS: Risk of VT > 6 mL/kg was significantly reduced in APRV and pressure support with guaranteed volume mode. APRV had the highest variability. Pressure support with guaranteed volume could be tested in patients with ARDS. [ABSTRACT FROM AUTHOR]

BACKGROUND: The present study explored the role of closing volume as a determinant of orthopnea in stable obese subjects. We hypothesized that: (1) increase in closing volume in supine position would be greater in orthopneic than in non-orthopneic subjects, and (2) the relationship of change in closing volume to change in dyspnea with position would be dependent on expiratory flow limitation in the sitting position. METHODS: In stable obese subjects, in sitting and supine positions, we measured the Borg dyspnea score, static lung volumes, expiratory flow limitation during tidal breathing, and single-breath nitrogen expiration test. From the latter, we determined closing volume and closing capacity, slope of phase III, and opening capacity. Orthopnea was defined as any increase in the Borg score in the supine position from its value in the sitting position. RESULTS: Twenty-one subjects (13 women), median age (interquartile range) 55 (49-57) y and with body mass index of 39 (38-42) kg/m² were included, of whom 12 were orthopneic and 11 had expiratory flow limitation while seated. In the sitting position, orthopneic and non-orthopneic subjects were similar for age, body mass index, and pulmonary function tests, including single-breath nitrogen expiration test-derived variables. In the orthopneic subjects, there were no changes in any respiratory variable between positions. In the non-orthopneic subjects, there was a significant decrease in slope of phase III in the supine position from 1.67 (1.33-3.60) to 1.40 (1.25-1.66)%/L (P = .008). Overall, the subjects' Borg score significantly correlated with the slope of phase III (r = 0.63, P = .002) and opening capacity (r = -0.47, P = .03). In 10 subjects without expiratory flow limitation, it correlated with slope of phase III (r = 0.68, P = .03). CONCLUSIONS: In stable obese subjects, magnitude of orthopnea correlated with an increase in the slope of phase III in subjects without expiratory flow limitation. Expiratory flow limitation should be taken into account in obese patients. [ABSTRACT FROM AUTHOR]

BACKGROUND: Previous bench studies suggest that dynamic hyperinflation may occur if intrapulmonary percussive ventilation (IPV) is superimposed on mechanical ventilation in volume controlled continuous mandatory ventilation (VC-CMV) mode. We tested the hypothesis that pressure controlled continuous mandatory ventilation (PC-CMV) can protect against this risk. METHODS: An ICU ventilator was connected to an IPV device cone adapter that was attached to a lung model (compliance 30 mL/cm H2O, resistance 20 cm H2O/L/s). We measured inspired tidal volume (VTI) and lung pressure (Plung). Measurements were first taken with IPV off and the ICU ventilator set to VC-CMV or PC-CMV mode with a targeted VTI of 500 mL. For each mode, an inspiratory time (TI of 0.8 or 1.5 s and PEEP 7 or 15 cm H2O were selected. The experiments were repeated with the IPV set to either 20 or 30 psi. The dependent variables were differences in VTI (ΔVTI) and Plung with IPV off or on. The effect of VC-CMV or PC-CMV mode was tested with the ICU ventilators for TI, PEEP, and IPV working pressure using repeated measures of analysis of variance. RESULTS: At TI 0.8 s and 20 psi, ΔVTI was significantly higher in VC-CMV than in PC-CMV. PEEP had no effect on ΔVTI. At TI 1.5 s and 20 psi and at both TI values at each psi, mode and PEEP had a significant effect on ΔVTI. With the ICU ventilators at TI 1.5 s, PEEP 7 cm H2O, and 30 psi, ΔVTI (mean ± SD) ranged from -2 7 ± 25 to -176 ± 6 mL in PC-CMV and from 258 ± 369 to 369 ± 16 mL in VC-CMV. The corresponding ranges were -15 ± 17 to -62 ± 68 mL in PC-CMV and 26 ± 21 to 102 ± 95 mL in VC-CMV at TI 0.8 s, PEEP 7 cm H2O , and 20 psi. Similar findings pertained to Plung. CONCLUSIONS: When IPV is added to mechanical ventilation, the risk of hyperinflation is greater with VC-CMV than with PC-CMV. We recommend using PC-CMV to deliver IPV and adjusting the trigger variable to avoid autotriggering. [ABSTRACT FROM AUTHOR]

BACKGROUND: The Nippy Clearway is a new mechanical insufflation-exsufflation device used to assist cough. METHODS: We compared the peak expiratory flow (PEF) with the Nippy Clearway versus the CoughAssist in a bench experiment. The relationship between PEF and pressure at the airway opening during exsufflation (minimum expiratory PAO) was investigated under 6 combinations of compliance (30 or 60 mL/cm H2O) (C30 and C60) and resistance (0, 5, or 20 cm H2O/L/s) (R0, R5, and R20) over a 25-50 cm H2O range of set PAO. The intercepts and slopes of the linear regression performed over PEF and PAO relationships were compared for both devices. RESULTS: For the C30R0, C30R5, and C60R5 conditions, the change in both the intercepts and slopes was significant with the Nippy Clearway, compared to the CoughAssist, averaging -2.96 L/s and -0.03 L/s/cm H2O, -1.46 L/s and 0.02 L/s/cm H2O, and -1.02 L/s and -0.04 L/s/cm H2O, respectively. As a result, at any minimum expiratory PAO, PEF was significantly greater with the Nippy Clearway. For C30R20 and C60R20, the regression lines were similar for the Nippy Clearway and CoughAssist. CONCLUSIONS: In this bench study, PEF with the Nippy Clearway was greater than with the CoughAssist at low respiratory-system compliance. [ABSTRACT FROM AUTHOR]

OBJECTIVE: To assess factors that predict good tolerance of noninvasive ventilation (NIV), in order to improve survival and quality of life in subjects with amyotrophic lateral sclerosis. METHODS: We conducted a prospective study in subjects with amyotrophic lateral sclerosis and requiring NIV. The primary end point was NIV tolerance at 1 month. Subjects, several of whom failed to complete the study, were classified as "tolerant" or "poorly tolerant," according to the number of hours of NIV use (more or less than 4 h per night, respectively). RESULTS: Eighty-one subjects, 73 of whom also attended the 1-month follow-up visit, participated over 34 months. NIV tolerance after the first day of utilization predicted tolerance at 1 month (77.6% and 75.3% of subjects, respectively). Multivariate analysis disclosed 3 factors predicting good NIV tolerance: absence of airway secretions accumulation prior to NIV onset (odds ratio 11.5); normal bulbar function at initiation of NIV (odds ratio 8.5); and older age (weakly significant, odds ratio 1.1). CONCLUSION: Our study reveals 3 factors that are predictive of good NIV tolerance, in particular the absence of airway secretion accumulation, which should prompt NIV initiation before its appearance. [ABSTRACT FROM AUTHOR]

BACKGROUND: We wanted to assess whether there was a significant relationship between recruited lung volume (Vrec) and change in density on digital processed chest x-ray measured at 2 different levels of inspiratory plateau pressure corresponding to 2 PEEP levels in patients with acute lung injury or ARDS. METHODS: In 14 subjects, PEEP 5 cm H2O and 15 cm H2O were prospectively applied in a random order for 10 min. At the end of each period, chest x-ray was taken using a digital portable device, and a pressure-volume curve of the respiratory system was performed. We also assessed PaO2 , and the static and the dynamic (Cdyn,rs) compliance of the respiratory system. Change in end-expiratory lung volume between tidal breath and relaxation volume of the respiratory system was determined. Radiological attenuation was measured on chest x-rays in 4 regions of interest in the right lung, and in 3 regions of interest in the left lung, drawn in posterior intercostal spaces from top to bottom, by using dedicated software. The ratio of lung density in each region between PEEP 15 and PEEP 5 (rP15/P5) and their arithmetic mean (μP15/P5) were computed. Vrec was determined from the pressure-volume curves. RESULTS: The median value of rP15/P5 in the 98 lung levels was 0.91 (0.80 -1.01), which was significantly different from 1 (P<.001). The values of rP15/P5 were not significantly different between the lung levels. The median values of Vrec and μP15/P5 were 288 (173- 402) mL and 0.90 (0.80-0.97), respectively. There was a significant negative correlation between Vrec and μP15/P5 (R = -0.77, P = .01). The reduction in μP15/P5 tended to correlate with the increase in Cdyn,rs (R= -0.49, P=.077) or in PaO2 (R= -0.53, P = .05) between PEEP 15 cm H2O and PEEP 5 cm H2O. CONCLUSIONS: Digital chest x-ray done at the bedside in acute lung injury/ARDS subjects was able to detect a reduction in density between PEEP 5 cm H2O and PEEP 15 cm H2O, which correlated with Vrec. [ABSTRACT FROM AUTHOR]

BACKGROUND: Intermittent positive pressure breathing (IPPB) is used in non-intubated patients to increase lung volume and to enhance coughing. Alpha 200 (Salvia Lifetec, Kronberg, Germany) is a specific IPPB device. CoughAssist (Respironics France, Carquefou, France) is a mechanical insufflator-exsufflator used to remove secretions in patients with inefficient cough. Both can also be used for intubated or tracheotomized patients. We assessed the impact of various artificial airways on the ability of the Alpha 200 and CoughAssist to generate insufflated volume. METHODS: We measured the insufflated volume and pressure at the airway opening in a lung model under 2 conditions of compliance (30 or 60 mL/cm H2O) at single resistance of 5 cm H2O/L/s. The devices were used at 2 set pressures: 30 and 40 cm H2O. The Alpha 200 was set at 2 inflation flows: 0.5 and 1 L/s, whereas CoughAssist was set at its highest value of 10 L/s. Measurements were done without (control) and with different size endotracheal tubes and tracheostomy cannulae. The relationships between insufflated volume and measured pressure were analyzed using linear regressions. RESULTS: The slopes and intercepts of the control relationship between insufflated volume and pressure were significantly greater with Alpha 200 at each set flow than with CoughAssist. As artificial airways were used, the insufflated volume did not differ from the control with CoughAssist, while with Alpha 200 it increased at each flow setting and for all mechanical conditions. The largest differences in insufflated volume between the 2 devices were observed for the largest endotracheal tubes and tracheostomy cannulas and for the lowest inflation flow setting in Alpha 200. These results can be explained in terms of how the devices function, as CoughAssist adapts by increasing flow, while Alpha 200 adapts by increasing inspiratory time. CONCLUSIONS: This bench study has shown that in the presence of artificial airways the value of the insufflated volume generated by the CoughAssist device was significantly lower than that generated by the Alpha 200 device. [ABSTRACT FROM AUTHOR]

BACKGROUND: The CoughAssist is a mechanical insufflator-exsufflator designed to assist airway secretion clearance in patients with ineffective cough. The device may benefit intubated and tracheotomized patients. We assessed the impact of various artificial airways on peak expiratory flow (PEF) with the CoughAssist. METHODS: We measured PEF and pressure at the airway opening in a lung model during insufflation-exsufflation with the CoughAssist, at 3 set pressures: 30/-30, 40/-40, and 50/-50 cm H2O, first without (control), and then with different sizes (6.5 to 8.5 mm inner diameter) of endotracheal tube (ETT) and tracheostomy tube (6, 7, and 8 mm inner diameter), compliance settings of 30 and 60 mL/cm H2O, and resistance settings of 0 and 5 cm H2O/L/s). We analyzed the relationship between PEF and pressure with linear regression. RESULTS: With compliance of 30 mL/cm H2O and 0 resistance the slope of the control relationship between PEF and pressure was statistically significantly greater than during any conditions with ETT or tracheostomy tube. Therefore, in comparison to the control, the relationship of PEF to pressure significantly went in the direction from top to bottom as the ETT or tracheostomy tube became narrower. The findings were the same with compliance of 30 mL/cmH2O and resistance of 5 cmH2O/L/s. With compliance of 60 mL/cm H2O the highest set pressure values were not achieved and some relationships departed from linearity. The control slope of the relationship between PEF and pressure with compliance of 60 mL/cm H2O and 0 resistance did not significantly differ with any ETT or tracheostomy tube. CONCLUSIONS. The artificial airways significantly reduced PEF during insufflation-exsufflation with CoughAssist; the narrower the inner diameter of the artificial airway, the lower the PEF for a given expiratory pressure. [ABSTRACT FROM AUTHOR]

BACKGROUND: Patients with chronic neuromuscular disease represent less than 10% of those receiving mechanical ventilation in the intensive care unit (ICU). Little has been reported regarding either ICU management of acute respiratory failure (ARF) in the era of noninvasive mechanical ventilation (NIV) or long-term outcomes. OBJECTIVE: To describe the respiratory management of patients with chronic neuromuscular diseases admitted to our university hospital ICU for ARF, and the long-term outcomes. METHODS: We retrospectively analyzed patients with chronic neuromuscular diseases admitted to our ICU for a first episode of ARF between January 1, 1996, and February 27, 2007. We assessed severity of illness on ICU admission, respiratory management during ICU stay, and outcomes on June 15, 2008. RESULTS: During the study period, 87 patients (44 with hereditary and 43 with acquired neuromuscular diseases) had their first ARF episode that required ICU admission. In the hereditary-diseases group and the acquired-diseases group, respectively, the rates of NIV use during the ICU stay were 82% and 63% (P = .040), the intubation rates were 30% and 56% (P = .02), and the tracheotomy rates were 9% and 12% (difference not significant). At the final assessment (median 3 years) the mortality rate was 58%, and mortality was not significantly related to the type of neuromuscular disease. At final assessment, 46% of the patients were on NIV and 29% had tracheotomy. CONCLUSIONS: In our ICU, chronic neuromuscular disease is an uncommon cause of ARF, for which we often use NIV. These patients had a low probability of death in the ICU. Long-term outcome was independent of the type of neuromuscular disease. [ABSTRACT FROM AUTHOR]

BACKGROUND: The Stewart approach theorizes that plasma pH depends on PaCO2, the strong ion difference, and the plasma total concentration of non-volatile weak acids (Atot). The conventional approach measures standardized base excess, bicarbonate (HCO3‾), and the anion gap. OBJECTIVE: To describe acid-base disorders with the Stewart approach and the conventional approach in patients with chronic respiratory failure. METHODS: This was an observational prospective study in a medical intensive care unit and a pneumology ward of a university hospital. There were 128 patients included in the study, of which 14 had more than one admission, resulting in 145 admissions. These were allocated to 4 groups: stable respiratory condition and elevated HCO3‾ (Group 1, n = 23), stable respiratory condition and non-elevated HCO3‾ (Group 2, n = 41), unstable respiratory condition and elevated HCO3‾ (Group 3, n = 44), and unstable respiratory condition and non-elevated HCO3‾ (Group 4, n = 37). Elevated HCO3‾ was defined as ≥ 3 standard deviations higher than the mean value we found in 8 healthy volunteers. Measurements were taken on admission. RESULTS: In groups 1, 2, 3, and 4, the respective mean ± SD values were: HCO3‾ 33 ± 3 mM, 26 ± 3 mM, 37 ± 4 mM, and 27 ± 3 mM (P < .001); strong ion difference 45 ± 3 mM, 38 ± 4 mM, 46 ± 4 mM, and 36 ± 4 mM (P < .001); and Atot 12 ± 1 mM, 12 ± 1 mM, 10 ± 1 mM, 10 ± 2 mM (P < .001). Non-respiratory disorders related to high strong ion difference were observed in 12% of patients with elevated HCO3‾, and in none of those with non-elevated HCO3‾ (P = .003). Non-respiratory disorders related to low strong ion difference were observed in 9% of patients with non-elevated HCO3‾, and in none of those with elevated HCO3‾ (P = .02). Hypoalbuminemia was common, especially in unstable patients (group 3, 66%; group 4, 65%). Normal standardized base excess (16%), HCO3‾ (28%), and anion gap (30%) values were common. The Stewart approach detected high effective strong ion difference in 13% of normal standardized base excess, and in 20% of normal anion gap corrected for albuminemia, and low effective strong ion difference in 22% of non-elevated HCO3‾. CONCLUSIONS: In patients with chronic respiratory failure the acid-base pattern is complex, metabolic alkalosis is present in some patients with elevated HCO3‾, and metabolic acidosis is present in some with non-elevated HCO3‾. The diagnostic performance of the Stewart approach was better than that of the conventional approach, even when corrected anion gap was taken into account. [ABSTRACT FROM AUTHOR]

BACKGROUND: The effects of intermittent positive-pressure breathing (IPPB) and abdominal belt on regional lung ventilation in neuromuscular patients are unknown. We conducted a prospective physiologic short-term study in stable neuromuscular patients to determine the effects of IPBB, with and without abdominal belt, on regional lung ventilation. METHODS: IPPB was performed as 30 consecutive deep breaths up to 30 cm H(2)O face-mask pressure each: 10 in supine position, 10 in left-lateral position, and 10 in right-lateral position. Each patient received IPPB sessions with and without an abdominal belt, in a random order, at one-day intervals. Patients were then followed-up to 3 hours after IPPB. Lung ventilation was measured via electrical-impedance tomography (tidal volume via electrical-impedance tomography [electrical-impedance V(T)], which is reported in arbitrary units) in 4 lung quadrants. Baseline V(T) and exhaled V(T) after each deep breath were also measured. The primary outcome was maintenance of regional ventilation after 3 hours. RESULTS: Global electrical-impedance V(T) remained significantly higher than at baseline as long as 3 hours after the IPPB sessions. Global and regional electrical-impedance V(T) at the end of the 3-hour study period was significantly higher with the abdominal belt in place. Regional ventilation did not change significantly. With IPPB in the supine position, electrical-impedance V(T) was significantly greater in the anterior than the posterior lung regions (P < .001). With IPPB in supine position, median and interquartile range V(T) values increased from 0.25 L (0.20-0.30) to the exhaled V(T) of 1.50 L (1.08-1.96) (P < .001). There were no differences in regional ventilation. CONCLUSIONS: In patients with neuromuscular disease, supine IPPB treatments, with or without abdominal belt, increased ventilation to anterior lungs regions, compared to the left-lateral and right-lateral positions. Global ventilation 3 hours after IPPB treatments remained higher than at baseline and was best preserved with the use of an abdominal belt. [ABSTRACT FROM AUTHOR]

BACKGROUND: The effects of intermittent positive-pressure breathing (IPPB) and abdominal belt on regional lung ventilation in neuromuscular patients are unknown. We conducted a prospective physiologic short-term study in stable neuromuscular patients to determine the effects of IPBB, with and without abdominal belt, on regional lung ventilation. METHODS: IPPB was performed as 30 consecutive deep breaths up to 30 cm H2O face-mask pressure each: 10 in supine position, 10 in left-lateral position, and 10 in right-lateral position. Each patient received IPPB sessions with and without an abdominal belt, in a random order, at one-day intervals. Patients were then followed-up to 3 hours after IPPB. Lung ventilation was measured via electrical-impedance tomography (tidal volume via electrical-impedance tomography [electrical-impedance VT], which is reported in arbitrary units) in 4 lung quadrants. Baseline VT and exhaled VT after each deep breath were also measured. The primary outcome was maintenance of regional ventilation after 3 hours. RESULTS: Global electrical-impedance VT remained significantly higher than at baseline as long as 3 hours after the IPPB sessions. Global and regional electrical-impedance VT at the end of the 3-hour study period was significantly higher with the abdominal belt in place. Regional ventilation did not change significantly. With IPPB in the supine position, electrical-impedance VT was significantly greater in the anterior than the posterior lung regions (P < .001). With IPPB in supine position, median and interquartile range VT values increased from 0.25 L (0.20-0.30) to the exhaled VT of 1.50 L (1.08 -1.96) (P < .001). There were no differences in regional ventilation. CONCLUSIONS: In patients with neuromuscular disease, supine IPPB treatments, with or without abdominal belt, increased ventilation to anterior lungs regions, compared to the left-lateral and rightlateral positions. Global ventilation 3 hours after IPPB treatments remained higher than at baseline and was best preserved with the use of an abdominal belt. [ABSTRACT FROM AUTHOR]

During mechanical ventilation for acute respiratory distress syndrome, tidal volume (V(T)) must be reduced. Once switched to pressure-support ventilation, there is a risk that uncontrolled large V(T) may be delivered. A 63-year-old man with community-acquired pneumonia required tracheal intubation and mechanical ventilation, with a V(T) of 6 mL/kg predicted body weight, PEEP of 10 cm H2O, a respiratory rate of 30 breaths/min, and FIO2 of 0.60. Plateau pressure was 22 cm H2O. He improved and received pressure-support. Twelve days later a chest radiograph showed suspected air leaks, confirmed via computed tomogram (CT), which showed anterior pneumomediastinum. V(T) received over the previous 3 days had averaged 14 mL/kg predicted body weight. The patient was put back onto volume-controlled mode, and 2 days later there were no air leaks. In pressure-support ventilation, V(T) must be closely monitored to ensure lung-protective mechanical ventilation. [ABSTRACT FROM AUTHOR]

During mechanical ventilation for acute respiratory distress syndrome, tidal volume (VT) must be reduced. Once switched to pressure-support ventilation, there is a risk that uncontrolled large VT may be delivered. A 63-year-old man with community-acquired pneumonia required tracheal intubation and mechanical ventilation, with a VT of 6 mL/kg predicted body weight, PEEP of 10 cm H2O, a respiratory rate of 30 breaths/min, and FIO2 of 0.60. Plateau pressure was 22 cm H2O. He improved and received pressure-support. Twelve days later a chest radiograph showed suspected air leaks, confirmed via computed tomogram (CT), which showed anterior pneumomediastinum. VT received over the previous 3 days had averaged 14 mL/kg predicted body weight. The patient was put back onto volume-controlled mode, and 2 days later there were no air leaks. In pressure-support ventilation, VT must be closely monitored to ensure lung-protective mechanical ventilation. [ABSTRACT FROM AUTHOR]

BACKGROUND: Prolonged immobilization may harm intensive care unit (ICU) patients, and early mobilization has been proposed to counteract that process. We describe our experience in early rehabilitation of ICU patients, and its effects on physiologic outcomes. METHODS: We included all patients who stayed in our 14-bed medical ICU for >/= 7 days and received invasive mechanical ventilation for >/= 2 days. The rehabilitation program included chair-sitting, tilting-up (with arms supported or unsupported), and walking. We collected vital signs before and after each intervention. RESULTS: Over a 5-month period we studied 20 patients, after a median ICU stay of 5 days. A contraindication to the intervention was present on 230 days (43%). Sedation (15%), shock (11%), and renal support (9%) were the most frequent contraindications. We obtained complete data from 275 of 424 interventions, 33% of which were performed during mechanical ventilation. The chair-sitting intervention was the most frequent (56%), followed by the tilting-up-with-arms-unsupported intervention (25%), the walking intervention (11%), and the tilting-up arms-supported intervention (8%). The chair-sitting intervention was associated with a significant (P = .03) decline in both heart rate (mean -3.5 beats/min, 95% confidence interval [CI] -6.5 to -0.4 beats/min) and respiratory rate (-1.4 breaths/min, 95% CI -2.6 to 0.1 breaths/min), whereas blood oxygen saturation (measured via pulse oximetry [S(pO(2))]) and mean arterial blood pressure did not change significantly. Heart rate and respiratory rate similarly increased with tilting-up: 14.6 beats/min, 95% CI 10.8 to 18.4 beats/min, and 5.5 breaths/min, 95% CI 3.6 to 7.3 breaths/min with arms unsupported, and 12.4 beats/min, 95% CI 7.0 to 17.9 beats/min and 2.6 breaths/min, 95% CI -0.4 to 5.7 breaths/min with arms supported). Heart rate and respiratory rate also increased with the walking intervention: 6.9 beats/min, 95% CI 2.6 to 11.1 beats/min, and 5.9 breaths/min, 95% CI 3.8 to 8.0 breaths/min. The walking intervention significantly decreased S(pO(2)). An adverse event occurred in 13 (3%) of 424 interventions, but none had harmful consequences. CONCLUSIONS: Early rehabilitation is feasible and safe in patients in the ICU for longer than 1 week. The chair-sitting intervention was associated with nonsignificant oxygenation improvement. The tilting-up intervention was an effort as intense as walking. [ABSTRACT FROM AUTHOR]

BACKGROUND: Prolonged immobilization may harm intensive care unit (ICU) patients, and early mobilization has been proposed to counteract that process. We describe our experience in early rehabilitation of ICU patients, and its effects on physiologic outcomes. METHODS: We included all patients who stayed in our 14-bed medical ICU for > 7 days and received invasive mechanical ventilation for > 2 days. The rehabilitation program included chair-sitting, tilting-up (with arms supported or unsupported), and walking. We collected vital signs before and after each intervention. RESULTS: Over a 5-month period we studied 20 patients, after a median ICU stay of 5 days. A contraindication to the intervention was present on 230 days (43%). Sedation (15%), shock (11%), and renal support (9%) were the most frequent contraindications. We obtained complete data from 275 of 424 interventions, 33% of which were performed during mechanical ventilation. The chair-sitting intervention was the most frequent (56%), followed by the tilting-upwith-arms-unsupported intervention (25%), the walking intervention (11%), and the tilting-up arms-supported intervention (8%). The chair-sitting intervention was associated with a significant (P = .03) decline in both heart rate (mean -3.5 beats/min, 95% confidence interval [CI] -6.5 to -0.4 beats/min) and respiratory rate (-1.4 breaths/min, 95% CI -2.6 to 0.1 breaths/min), whereas blood oxygen saturation (measured via pulse oximetry [SpO2 ]) and mean arterial blood pressure did not change significantly. Heart rate and respiratory rate similarly increased with tilting-up: 14.6 beats/ min, 95% CI 10.8 to 18.4 beats/min, and 5.5 breaths/min, 95% CI 3.6 to 7.3 breaths/min with arms unsupported, and 12.4 beats/min, 95% CI 7.0 to 17.9 beats/min and 2.6 breaths/min, 95% CI -0.4 to 5.7 breaths/min with arms supported). Heart rate and respiratory rate also increased with the walking intervention: 6.9 beats/min, 95% CI 2.6 to 11.1 beats/min, and 5.9 breaths/min, 95% CI 3.8 to 8.0 breaths/min. The walking intervention significantly decreased SpO2 . An adverse event occurred in 13 (3%) of 424 interventions, but none had harmful consequences. CONCLUSIONS: Early rehabilitation is feasible and safe in patients in the ICU for longer than 1 week. The chairsitting intervention was associated with nonsignificant oxygenation improvement. The tilting-up intervention was an effort as intense as walking. [ABSTRACT FROM AUTHOR]

BACKGROUND: In patients with acute lung injury (ALI)/acute respiratory distress syndrome (ARDS), the use of alveolar-recruitment maneuvers to improve oxygenation is controversial. There is lack of standardization and lack of clinical studies to compare various recruitment maneuvers. Recruitment maneuvers are closely linked to the selection of positive end-expiratory pressure (PEEP), which is also a subject of debate. METHODS: With 12 intubated and mechanically ventilated patients with early ALI/ARDS we conducted a recruitment maneuver (sustained inflation at 40 cm H(2)O for 30 s), then set PEEP at 24 cm H(2)O, and then we reduced PEEP stepwise, by 4 cm H(2)O every 10 min. We kept the fraction of inspired oxygen (F(IO(2))) at 0.8. After each PEEP decrement step we measured P(aO(2)). We defined the 'optimal' PEEP as the PEEP step above which P(aO(2)) decreased by >/= 20%. All the patients then underwent a period of ventilation on the same settings: tidal volume 6 mL/kg, PEEP at the level set by the physician before the experiment, plateau pressure < 30 cm H(2)O. Then each patient underwent 3 ventilation strategies, each applied for one hour: optimal PEEP alone; optimal PEEP plus one sustained inflation (40 cm H(2)O for 30 s); and optimal PEEP plus sigh breaths (ie, twice the baseline tidal volume, plateau pressure < 40 cm H(2)O) every 25 breaths. After the application of each PEEP strategy we measured arterial blood gas values and the static compliance of the respiratory system. RESULTS: The mean +/- SD optimal PEEP was 12 +/- 4 cm H(2)O. The measurements from the standardization periods were comparable between the 3 PEEP groups. In the optimal-PEEP-plus-sighs group the changes in P(aO(2)) (85 +/- 96%) and static compliance (14 +/- 20%) were significantly greater than in the 2 other groups. CONCLUSIONS: Sighs superimposed on lung-protective mechanical ventilation with optimal PEEP improved oxygenation and static compliance in patients with early ALI/ARDS. [ABSTRACT FROM AUTHOR]

BACKGROUND: In patients with acute lung injury (ALI)/acute respiratory distress syndrome (ARDS), the use of alveolar-recruitment maneuvers to improve oxygenation is controversial. There is lack of standardization and lack of clinical studies to compare various recruitment maneuvers. Recruitment maneuvers are closely linked to the selection of positive end-expiratory pressure (PEEP), which is also a subject of debate. METHODS: With 12 intubated and mechanically ventilated patients with early ALI/ARDS we conducted a recruitment maneuver (sustained inflation at 40 cm H2O for 30 s), then set PEEP at 24 cm H2O, and then we reduced PEEP stepwise, by 4 cm H2O every 10 min. We kept the fraction of inspired oxygen (FIO2 ) at 0.8. After each PEEP decrement step we measured Pao2 . We defined the "optimal" PEEP as the PEEP step above which Pao2 decreased by ≥ 20%. All the patients then underwent a period of ventilation on the same settings: tidal volume 6 mL/kg, PEEP at the level set by the physician before the experiment, plateau pressure < 30 cm H2O. Then each patient underwent 3 ventilation strategies, each applied for one hour: optimal PEEP alone; optimal PEEP plus one sustained inflation (40 cm H2O for 30 s); and optimal PEEP plus sigh breaths (ie, twice the baseline tidal volume, plateau pressure < 40 cm H2O) every 25 breaths. After the application of each PEEP strategy we measured arterial blood gas values and the static compliance of the respiratory system. RESULTS: The mean ± SD optimal PEEP was 12 ± 4 cmH2O. The measurements from the standardization periods were comparable between the 3 PEEP groups. In the optimal-PEEP-plus-sighs group the changes in Pao2 (85 ± 96%) and static compliance (14 ± 20%) were significantly greater than in the 2 other groups. CONCLUSIONS: Sighs superimposed on lung-protective mechanical ventilation with optimal PEEP improved oxygenation and static compliance in patients with early ALI/ARDS. [ABSTRACT FROM AUTHOR]

BACKGROUND: In patients with restrictive thoracic disease, little is known about changes in sleep andbreathing if the patient stops using nocturnal noninvasive ventilation (NIV). Better understanding ofthose changes may affect NIV management and improve our understanding of the relationship ofnight-to-night variability of respiratory and sleep variables and morning gas exchange. METHODS:With 6 stable patients with restrictive chronic respiratory failure who were being treated with homeNIV we conducted a 5-step study: (1) The subject underwent an in-hospital baseline sleep study whileon NIV, then next-morning pulmonary function tests. (2) At home, on consecutive nights, the subjectunderwent the same sleep-study measurements while not using NIV, until the patient had what wedefined as respiratory decompensation (oxygen saturation measured via pulse oximetry [SpO.J < 88%or end-tidal CO2 pressure [PETCO.J > 50 mm Hg, with or without headaches, fatigue, or worseningdyspnea). Each morning after each home sleep-study night otT NIV, we also measured Spoz and PETCOz'(3) The patient returned to the hospital for a second overnight assessment, the same as the baseline assessment except without NIV. (4) The patient went home and restarted using NIV with his or her pre-study NIVsettings. (5) After the numberofnights backonhome NIV matchedthenumberofnights the patient had been otT NIV, the patient returned to the hospital for a third in-hospital assessment. We measured static lung volumes, maximum inspiratory and expiratory static mouth pressure, breathing pattern, arterial blood gases, SpOz' PETCOz' and full overnight polysomnography values. RESULTS: Respiratory decompensation occurred 4-15 days after NIV discontinuation (mean 6.8 d). On the first and second in-hospital assessment nights, respectively, the mean nadir nocturnal SpOz values were 84 ± 2% and 64 ± 4%, the total apnea-hypopnea index values were 0 ::t 0 and 9 ± 2, and the obstructive hypopnea index values were 0 :!: 0 and 7 ::t 1 episodes per total sleep hour. Respiratory events started on the fll'St night off NIV. Spirometry, muscle strength, and sleep architecture did not change significantly. With resumption ofNIV, baseline conditions were recovered. CONCLUSIONS: NIV discontinuation in patients with restrictive chronic respiratory failure previously stabilized on NIV promptly leads to nocturnal respiratory failure and within days to diurnal respiratory failure. Stopping NIV for more than a day or two is not recommended. [ABSTRACT FROM AUTHOR]

BACKGROUND: In patients with restrictive thoracic disease, little is known about changes in sleep and breathing if the patient stops using nocturnal noninvasive ventilation (NIV). Better understanding of those changes may affect NIV management and improve our understanding of the relationship of night-to-night variability of respiratory and sleep variables and morning gas exchange. METHODS: With 6 stable patients with restrictive chronic respiratory failure who were being treated with home NIV we conducted a 5-step study: (1) The subject underwent an in-hospital baseline sleep study while on NIV, then next-morning pulmonary function tests. (2) At home, on consecutive nights, the subject underwent the same sleep-study measurements while not using NIV. until the patient had what we defined as respiratory decompensation (oxygen saturation measured via pulse oximetry [SpO2] < 88% or end-tidal CO2 pressure [PETCO2] > 50 mm Hg, with or without headaches, fatigue, or worsening dyspnea). Each morning after each home sleep-study night off NIV, we also measured SpO2 and [PETCO2]. (3) The patient returned to the hospital for a second overnight assessment, the same as the baseline assessment except without NIV. (4) The patient went home and restarted using NIV with his or her pre-study NIV settings (5) After the number of nights back on home NIV matched the number of nights the patient had been off NIV. the patient returned to the hospital for a third in-hospital assessment. We measured static lung volumes, maximum inspiratory and expiratory static mouth pressure, breathing pattern, arterial blood gases, SpO2, [PETCO2], and full overnight polysomnograpby values. RESULTS: Respiratory decompensation occurred 4-15 days after NIV discontinuation (mean 6.8 d). On the first and second in-hospital assessment nights, respectively, the mean nadir nocturnal SpO2 values were 84 ± 2% and 64 ± 4%, the total apnea-hypopnea index values were 0 ± 0 and 9 ± 2, and the obstructive hypopnea index values were 0 ± 0 and 7 ± 1 episodes per total sleep hour. Respiratory events started on the first night off NIV. Spirometry, muscle strength, and sleep architecture did not change significantly. With resumption of NIV, baseline conditions were recovered. CONCLUSIONS: NIV discontinuation in patients with restrictive chronic respiratory failure previously stabilized on NIV promptly leads to nocturnal respiratory failure and within days to diurnal respiratory failure. Stopping NIV for more than a day or two is not recommended. [ABSTRACT FROM AUTHOR]

Several letters to the editor and a reply are presented in response to the article "Quantitative analysis of acid-base disorders in patients with chronic respiratory failure in stable or unstable respiratory condition," by C. Guérin and colleagues.

The author discusses an in vitro study that examines the movement of mucus over a tube actuated with a mechanical insufflation-exsufflation device set at different combinations of flow and pressure. The reproducibility to achieve the low insufflation flow manually has not been evaluated. The flow is said to be clearly correlated to the shear stress in a given geometry. It is said that a viscoelastic and a shear-thinning behavior with some thixotropy are often evoked.

A letter to the editor and a reply are presented in response to the article "Quantitative analysis of acid-base disorders in patients with chronic respiratory failure in stable or unstable respiratory condition," by C. Guérin and colleagues in the November 2010 issue of the journal "Respiratory Care."