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The most beneficial effect of corticosteroid therapy in COVID-19 patients has been shown in subjects receiving invasive mechanical ventilation (IMV), corresponding to a score of 6 on the World Health Organization (WHO) COVID-19 Ordinal Scale for Clinical Improvement (OSCI). The aim of this observational, single-center, prospective study was to assess the association between corticosteroids and hospital mortality in coronavirus disease 2019 (COVID-19) patients who did not receive IMV (OSCI 3-5). Included were 1,311 COVID-19 patients admitted to nonintensive care wards, and they were divided in two cohorts: (i) 480 patients who received corticosteroid therapy and (ii) 831 patients who did not. The median daily dose was of 8 mg of dexamethasone or equivalent, with a mean therapy duration of 5 (3-9) days. The indication to administer or withhold corticosteroids was given by the treating physician. In-hospital mortality was similar between the two cohorts after adjusting for possible confounders (adjusted odds ratio (ORadj) 1.04, 95% confidence interval (CI), 0.81-1.34, P = 0.74). There was also no difference in Intensive Care Unit (ICU) admission (ORadj 0.81, 95% CI, 0.56-1.17, P = 0.26). COVID-19 patients with noninvasive mechanical ventilation (NIMV) had a lower risk for ICU admission if they received steroid therapy (ORadj 0.58, 95% CI, 0.35-0.94, P = 0.03). In conclusion, corticosteroids were overall not associated with a difference in hospital mortality for patients with COVID-19 with OSCI 3-5. In the subgroup of patients with NIMV (OSCI 5), corticosteroids reduced ICU admission, whereas the effect on mortality requires further studies.

BACKGROUND: The ratio of dead space to tidal volume (VD/VT) is associated with mortality in patients with ARDS. Corrected minute ventilation ([Formula: see text]) is a simple surrogate of dead space, but, despite its increasing use, its association with mortality has not been proven. The aim of our study was to assess the association between [Formula: see text] and hospital mortality. We also compared the strength of this association with that of estimated VD/VT and ventilatory ratio.METHODS: We performed a retrospective study with prospectively collected data. We evaluated 187 consecutive mechanically ventilated subjects with ARDS caused by novel coronavirus disease (COVID-19). The association between [Formula: see text] and hospital mortality was assessed in multivariable logistic models. The same was done for estimated VD/VT and ventilatory ratio.RESULTS: Mean ± SD [Formula: see text] was 11.8 ± 3.3 L/min in survivors and 14.5 ± 3.9 L/min in nonsurvivors (P < .001) and was independently associated with mortality (adjusted odds ratio 1.15, P = .01). The strength of association of [Formula: see text] with mortality was similar to that of VD/VT and ventilatory ratio.CONCLUSIONS: [Formula: see text] was independently associated with hospital mortality in subjects with ARDS caused by COVID-19. [Formula: see text] could be used at the patient's bedside for outcome prediction and severity stratification, due to the simplicity of its calculation. These findings need to be confirmed in subjects with ARDS without viral pneumonia and when lung-protective mechanical ventilation is not rigorously applied.

BACKGROUND: ARDS in patients with coronavirus disease 2019 (COVID-19) is characterized by microcirculatory alterations in the pulmonary vascular bed, which could increase dead-space ventilation more than in non-COVID-19 ARDS. We aimed to establish if dead-space ventilation is different in patients with COVID-19 ARDS when compared with patients with non-COVID-19 ARDS.METHODS: A total of 187 subjects with COVID-19 ARDS and 178 subjects with non-COVID-19 ARDS who were undergoing invasive mechanical ventilation were included in the study. The association between the ARDS types and dead-space ventilation, compliance of the respiratory system, subjects' characteristics, organ failures, and mechanical ventilation was evaluated by using data collected in the first 24 h of mechanical ventilation.RESULTS: Corrected minute ventilation (V˙E), a dead-space ventilation surrogate, was higher in the subjects with COVID-19 ARDS versus in those with non-COVID-19 ARDS (median [interquartile range] 12.6 [10.2-15.8] L/min vs 9.4 [7.5-11.6] L/min; P < .001). Increased corrected V˙E was independently associated with COVID-19 ARDS (odds ratio 1.24, 95% CI 1.07-1.47; P = .007). The best compliance of the respiratory system, obtained after testing different PEEPs, was similar between the subjects with COVID-19 ARDS and the subjects with non-COVID-19 ARDS (mean ± SD 38 ± 11 mL/cm H2O vs 37 ± 11 mL/cm H2O, respectively; P = .61). The subjects with COVID-19 ARDS received higher median (interquartile range) PEEP (12 [10-14] cm H2O vs 8 [5-9] cm H2O; P < .001) and lower median (interquartile range) tidal volume (5.8 [5.5-6.3] mL/kg vs 6.6 [6.1-7.3] mL/kg; P < .001) than the subjects with non-COVID-19 ARDS, being these differences maintained at multivariable analysis. In the multivariable analysis, the subjects with COVID-19 ARDS showed a lower risk of anamnestic arterial hypertension (odds ratio 0.18, 95% CI 0.07-0.45; P < .001) and lower neurologic sequential organ failure assessment score (odds ratio 0.16, 95% CI 0.09-0.27; P < .001) than the subjects with non-COVID-19 ARDS.CONCLUSIONS: Indirect measurements of dead space were higher in subjects with COVID-19 ARDS compared with subjects with non-COVID-19 ARDS. The best compliance of the respiratory system was similar in both ARDS forms provided that different PEEPs were applied. A wide range of compliance is present in every ARDS type; therefore, the setting of mechanical ventilation should be individualized patient by patient and not based on the etiology of ARDS.

OBJECTIVES: Early tracheotomy, defined as a procedure performed within 10 days from intubation, is associated with more ventilator free days, shorter ICU stay, and lower mortality than late tracheotomy. During the coronavirus disease 2019 pandemic, it was especially important to save operating room resources and to have a shorter ICU stay for patients, when ICUs had insufficient beds. In this context of limited resources, early percutaneous tracheostomy could be an effective way to manage mechanically ventilated patients. Nevertheless, current recommendations suggest delaying or avoiding the tracheotomy in coronavirus disease 2019 patients. Aim of the study was to analyze the hospital mortality of coronavirus disease 2019 patients who had received early percutaneous tracheostomy and factors associated with removal of tracheostomy cannula at ICU discharge.DESIGN: Cohort study.SETTING: Coronavirus disease 2019 ICU.PATIENTS: Adult patients with coronavirus disease 2019 3 days after ICU admission.INTERVENTIONS: None.MEASUREMENTS AND MAIN RESULTS: Three days after ICU admission, 164 patients were present in ICU and included in the analysis. One-hundred and twenty-one patients (74%) were tracheostomized, whereas the other 43 (26%) were managed with translaryngeal intubation only. In multivariable analysis, early percutaneous tracheostomy was associated with lower hospital mortality. Sixty-six of tracheostomized patients (55%) were discharged alive from the hospital. Age and male sex were the only characteristics that were independently associated with mortality in the tracheostomized patients (45.5% and 62.8% in tracheostomized and nontracheostomized patients, respectively; p = 0.009). Tracheostomy tube was removed in 47 of the tracheostomized patients (71%). The only variable independently associated with weaning from tracheostomy at ICU discharge was a faster start of spontaneous breathing after tracheotomy was performed.CONCLUSIONS: Early percutaneous tracheostomy was safe and effective in coronavirus disease 2019 patients, giving a good chance of survival and of weaning from tracheostomy cannula at ICU discharge.

BackgroundIn mechanically ventilated acute respiratory distress syndrome (ARDS) patients infected with the novel coronavirus disease (COVID-19), we frequently recognised the development of pneumomediastinum and/or subcutaneous emphysema despite employing a protective mechanical ventilation strategy. The purpose of this study was to determine if the incidence of pneumomediastinum/subcutaneous emphysema in COVID-19 patients was higher than in ARDS patients without COVID-19 and if this difference could be attributed to barotrauma or to lung frailty.MethodsWe identified both a cohort of patients with ARDS and COVID-19 (CoV-ARDS), and a cohort of patients with ARDS from other causes (noCoV-ARDS).Patients with CoV-ARDS were admitted to an intensive care unit (ICU) during the COVID-19 pandemic and had microbiologically confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. NoCoV-ARDS was identified by an ARDS diagnosis in the 5 years before the COVID-19 pandemic period.ResultsPneumomediastinum/subcutaneous emphysema occurred in 23 out of 169 (13.6%) patients with CoV-ARDS and in three out of 163 (1.9%) patients with noCoV-ARDS (pCoV-ARDS patients had a high incidence of pneumomediastinum/subcutaneous emphysema despite the use of low tidal volume (5.9±0.8 mL·kg−1 ideal body weight) and low airway pressure (plateau pressure 23±4 cmH2O).ConclusionsWe observed a seven-fold increase in pneumomediastinum/subcutaneous emphysema in CoV-ARDS. An increased lung frailty in CoV-ARDS could explain this finding more than barotrauma, which, according to its etymology, refers to high transpulmonary pressure.

The purpose of this review is to summarize the pathophysiology of complex regional pain syndrome (CRPS), the underlying molecular mechanisms, and potential treatment options for its management. CRPS is a multifactorial pain condition. CRPS is characterized by prolonged or excessive pain and changes in skin color and temperature, and/or swelling in the affected area, and is generally caused by stimuli that lead to tissue damage. An inflammatory response involving various cytokines and autoantibodies is generated in response to acute trauma/stress. Chronic phase pathophysiology is more complex, involving the central and peripheral nervous systems. Various genetic factors involved in the chronicity of pain have been identified in CRPS patients. As with other diseases of complex pathology, CRPS is difficult to treat and no single treatment regimen is the same for two patients. Stimulation of the vagus nerve is a promising technique being tested for different gastrointestinal and inflammatory diseases. CRPS is more frequent in individuals of 61–70 years of age with a female to male ratio of 3 : 1. Menopause, migraine, osteoporosis, and asthma all represent risk factors for CRPS and in smokers the prognosis appears to be more severe. The pathophysiological mechanisms underlying CRPS involve both inflammatory and neurological pathways. Understanding the molecular basis of CRPS is important for its diagnosis, management, and treatment. For instance, vagal nerve stimulation might have the potential for treating CRPS through the cholinergic anti-inflammatory pathway.

Objective The aim of our study was to determine the incidence, characteristics, and clinical outcomes of patients with the novel coronavirus (COVID-19) infection who had presented with and been treated for acute limb ischemia (ALI) during the 2020 coronavirus pandemic. Methods We performed a single-center, observational cohort study. The data from all patients who had tested positive for COVID-19 and had presented with ALI requiring urgent operative treatment were collected in a prospectively maintained database. For the present series, successful revascularization of the treated arterial segment was defined as the absence of early ( Results We evaluated the data from 20 patients with ALI who were positive for COVID-19. For the period from January to March, the incidence rate of patients presenting with ALI in 2020 was significantly greater than that for the same months in 2019 (23 of 141 [16.3%] vs 3 of 163 [1.8%]; P Conclusions In our preliminary experience, the incidence of ALI has significantly increased during the COVID-19 pandemic in the Italian Lombardy region. Successful revascularization was lower than expected, which we believed was due to a virus-related hypercoagulable state. The use of prolonged systemic heparin might improve surgical treatment efficacy, limb salvage, and overall survival.

The purpose of this study was to evaluate early and midterm results of tibial bypasses comparing precuffed expanded polytetrafluoroethylene (PTFE) graft (Distaflo) and heparin-bonded PTFE graft (Propaten) with a distal vein patch.This is a retrospective cohort analysis evaluating patients who underwent PTFE femorocrural bypasses between April 2004 and December 2010 at the Vascular Surgery Division of the Poliambulanza Foundation Hospital (Brescia, Italy). Results were analyzed in terms of primary and secondary graft patency, limb salvage, and survival with univariate (Kaplan-Meier curves and log-rank test) and multivariate (Cox regression) analyses.After analyzing many patients, we found 79 femorotibial bypass PTFE grafts. We used a Propaten graft and vein patch in 40 patients and a Distaflo graft in 39 patients. The two groups were comparable for main risk factors, except for age. Indication for surgical revascularization was critical limb ischemia in all patients. In 54 cases (68%), it was a redo bypass because of a previously failed revascularization. Perioperative mortality within 30 days from intervention was 2.5%, whereas overall mortality during follow-up was 29%, with a 36-month survival rate of 58% (95% confidence interval [CI]: 0.44-0.77) on life table analysis. We observed a significant difference between two groups in terms of survival at 36 months (Propaten: 0.84 [95% CI: 0.69-1]; Distaflo: 0.21 [95% CI: 0.07-0.63]; P0.001; 95% CI: 0.07-0.63; odds ratio [OR]: 0.21). At 24 months, the two groups (Propaten vs. Distaflo) were equivalent in terms of primary patency (Propaten: 0.33 [95% CI: 0.21-0.53]; Distaflo: 0.47 [95% CI: 0.32-0.70]; P = 0.793), secondary patency (Propaten: 0.36 [95% CI: 0.23-0.57]; Distaflo: 0.49 [95% CI: 0.33-0.72]; P = 0.855), and limb salvage (Propaten: 0.65 [95% CI: 0.51-0.84]; Distaflo: 0.57 [95% CI: 0.41-0.79]; P = 0.18). At Cox regression analysis, age of80 years (P0.04; 95% CI: 0.23-0.95; OR: 0.47), peroneal artery distal anastomosis (P0.04; 95% CI: 1.04-5.62; OR: 2.42), simultaneous adjunctive procedures (P0.02; 95% CI: 1.21-17.74; OR: 4.64), and redo bypass (P0.05; 95% CI: 1-6.26; OR: 2.5) were associated with long-term poorer primary patency rates. Postoperative treatment with warfarin therapy compared with antiplatelet therapy was independently associated with better secondary patency (P0.04; 95% CI: 0.20-0.95; OR: 0.44) and limb salvage (P0.03; 95% CI: 0.11-0.87; OR: 0.32) rates.Distaflo and Propaten with a distal vein patch in our experience have similar patency and limb salvage results, although further randomized and larger studies are necessary. Postoperative anticoagulation therapy seems better than antiplatelet therapy in terms of patency and limb salvage rate.

We compared the risk of pulmonary aspiration in patients whose lungs were mechanically ventilated through a laryngeal mask airway (35 630 procedures) or tracheal tube (30 082 procedures). Three cases of pulmonary aspiration occurred with the laryngeal mask airway and seven with the tracheal tube. There were no deaths related to pulmonary aspiration. The incidence and outcome of pulmonary aspiration detected in this study were similar to those previously reported. The adjusted odds ratio (OR) for pulmonary aspiration with the laryngeal mask airway was 1.06 (95% CI 0.20-5.62). Unplanned surgery (OR 30.5, 95% CI 8.6-108.9) and male sex (OR 8.6, 95% CI 1.1-68) were associated with an increased risk of aspiration and age < 14 years with a reduced risk (OR 0.21, 95% CI 0.07-0.64). There were contraindications and exclusions to the use of the laryngeal mask airway but in this selected population the use of an laryngeal mask airway was not associated with an increased risk of pulmonary aspiration compared with a tracheal tube.

We analyzed ventilation-induced changes in arterial blood pressure and photoplethysmography from waveforms obtained by monitoring 57 patients in the operating room and intensive care unit. Analysis of systolic and pulse pressure variations during positive pressure ventilation, DeltaUp, DeltaDown, and changes in the preejection period on both arterial and photoplethysmographic waveforms were possible in 49 (86%) patients. The pulse pressure variation and preejection period were similar when calculated using both arterial blood pressure and photoplethysmography, whereas the other variables were different. Photoplethysmographic pulse variation >9% identified patients with arterial pulse pressure variation >13% (area under ROC curve = 0.85) or DeltaDown >5 mm Hg (area under ROC curve = 0.85). In hypotensive patients, photoplethysmographic pulse variation >9% remained the best threshold value (pulse pressure variation >13%: area under ROC curve = 0.90; DeltaDown >5 mm Hg: area under ROC curve = 0.93) for predicting fluid responsiveness. In conclusion, this study showed that pulse variations observed in the arterial pressure waveform and photoplethysmogram are similiar in response to positive pressure ventilation. Furthermore, photoplethysmographic pulse variation > 9% identifies patients with ventilation-induced arterial blood pressure variation that is likely to respond to fluid administration.

To compare the effects of norepinephrine and metaraminol on hemodynamics in septic shock patients.Open-label, controlled clinical trial in the general intensive care unit of a university-affiliated hospital.Ten consecutive septic shock patients receiving norepinephrine to maintain the mean arterial pressure higher than 65 mmHg.Patients were monitored with pulmonary artery catheter and indirect calorimetry. At the baseline hemodynamic variables were obtained during norepinephrine infusion. Subsequently norepinephrine was replaced by metaraminol infusion in a dose sufficient to keep mean arterial pressure constant. After 20 min of stable arterial pressure a new set of measurement was repeated.Mean arterial pressure did not differ significantly with norepinephrine or metaraminol; there was no relationship between the norepinephrine and metaraminol doses. Replacement norepinephrine with metaraminol did not modify hemodynamic variables; in particular there were no changes in heart rate, stroke volume index, pulmonary artery occlusion pressure, or oxygen consumption index.This study shows that metaraminol increases arterial pressure as does norepinephrine in septic shock patients. Despite similar effects of norepinephrine and metaraminol, there was no relationship between the dose of the two drugs.

Background: The ProSeal Laryngeal Mask Airway (PLMA) ventilation tube is narrower and shorter than the standard Laryngeal Mask Airway (LMA) and is without the vertical bars at the end of the tube. In this randomized, crossover study, PLMA and LMA resistances were compared. Methods: Respiratory mechanics was calculated in 26 anesthetized, mechanically ventilated patients with both LMA and PLMA. The laryngeal mask positioning was fiberoptically evaluated. Differences in the respiratory mechanics of the LMA and the PLMA were attributed to the differences between the laryngeal masks. Results: In the total study population the airway resistance was 1.5 ± 2.6 hPa.l−1.s−1 (P = 0.005) higher with the PLMA than with the LMA. During the PLMA use, the peak expiratory flow reduced by 0.02 ± 0.05 l min−1 (P = 0.046), the expiratory resistance increased by 0.6 ± 1.3 hPa.l−1.s−1 (P = 0.022), and the time constant of respiratory system lengthened by 0.09 ± 0.18 s (P = 0.023). These differences doubled when the LMA was better positioned than the PLMA, whereas they disappeared when the PLMA was positioned better than the LMA. Conclusions: The standard LMA offers a lower resistive load than the PLMA. Moreover, the fitting between the laryngeal masks and the larynx, as fiberoptically evaluated, plays a major role in determining the resistive properties of these devices.

Background The ProSeal™ laryngeal mask airway (PLMA) may have advantages over the laryngeal mask airway (LMA† †LMA® is the property of Intavent Limited.) in obese patients. We tested this hypothesis in a clinical setting. Methods Sixty obese patients (BMI >30) were randomized to receive mechanical ventilation (tidal volume 7 ml kg−1, PEEP 10 cm H2O), through either the PLMA or the LMA. A gastric tube was used in all patients. Cuff pressure was set at 60 cm H2O and increased progressively until excessive leak occurred. The incidence of sore throat was assessed at recovery and after 1 week. Results The mean leak fraction was 6.1 (sd 2.9)% with the LMA and 6.4 (3.5)% with the PLMA (P=0.721). With the PLMA, with no sign of ventilation problems, the drainage tube was not patent in three patients. The cuff pressure was >100 cm H2O in 38% of the LMA group and 7% of the PLMA group (P=0.05). The incidence of sore throat was similar in both groups and it was similarly scored in the recovery room and 1 week after surgery. Conclusions Both the PLMA and the LMA can be used for mechanical ventilation of obese patients. The patency of the PLMA drainage tube needs to be checked constantly even when an optimal airtight seal is present. In obese patients the LMA requires a greater cuff pressure than the PLMA, but sore throat is not related to the cuff pressure. Sore throat assessment in the recovery room appears as reliable as assessment later.

Background The tracheal tube (TT) produces reversible bronchoconstriction and increases pulmonary airway resistance compared to the laryngeal mask airway (LMA). The possible persistence of this effect in the postoperative period has not been studied. The aim of this study was to compare the early postoperative pulmonary function in healthy patients undergoing minor surgical procedures with the LMA or with the TT. Methods Sixty patients scheduled for saphenous vein stripping under general anaesthesia were randomised to receive the LMA or the TT. Before anaesthesia and 20 min after LMA or TT removal, pulse oxymetry values (SpO(2)) were recorded and patients performed forced spirometry in the supine position. Results Preoperative pulmonary function was normal in both groups. There were no differences between groups in the preoperative respiratory function test and SpO(2). Following surgery SpO(2), forced expiratory volume in the first second (FEV1), forced vital capacity (FVC) and peak expiratory flow (PEF) decreased in both groups. The FEV1/FVC did not change in either of the groups. In the TT group, compared to patients using the LMA, there was a greater relative decrease of SpO(2) (2.7 +/- 2.7% vs. 1.3 +/- 2.2%, P=0.017), FEV1 (17.6 +/- 12.2% vs. 8 +/- 17.4%, P=0.008), FVC (15.8 +/- 12.4% vs. 9 +/- 13.4%, P=0.023) and PEF (20.6% +/- 15.3% vs. 8.1 +/- 33.3%, P=0.033). Conclusions This study demonstrates greater early postoperative respiratory restrictive syndrome and lower arterial oxygen saturation following tracheal intubation compared to LMA use in patients without respiratory disease.

To quantify the impact on peak airway pressure of pressure-controlled and volume-controlled ventilation during Laryngeal Mask Airway (LMA) use.Prospective, crossover clinical study.University-affiliated hospital.32 ASA physical status I and II patients undergoing general anesthesia with the LMA.Patients were ventilated for three minutes both with pressure-controlled and volume-controlled ventilation, provided that tidal volume (V(T) ) and inspiratory time (It) were constant.The monitored parameters were electrocardiography, arterial blood pressure, pulse oximetry, capnography, neuromuscular transmission, airway pressure and flow, and concentration of ventilated vapors and gases. The actually delivered V(T) was similar with both types of ventilation (volume-controlled = 0.67 +/- 0.13 lt, pressure-controlled = 0.67 +/- 0.14 lt; p = 0.688). Peak airway pressure was lower during pressure-controlled ventilation (14.6 +/- 3.5 cmH(2)O) than during volume-controlled ventilation (16 +/- 4 cmH(2)O) (p0.001). Furthermore, we noted that the higher the airway pressure with volume-controlled ventilation, the greater was the reduction in airway pressure during pressure-controlled ventilation.Pressure-controlled rather than volume-controlled ventilation can improve the effectiveness of mechanical ventilation in patients with high airway pressure.

Study objectives To compare the effectiveness of two modalities of external ventilation during rigid bronchoscopy: intermittent negative pressure ventilation (INPV) and external high-frequency oscillation (EHFO). Design Prospective, controlled, randomized, nonblinded study. Setting University-affiliated hospital. Patients Seventy patients undergoing interventional rigid bronchoscopy for tracheobronchial lesions were enrolled into the study. Interventions Mechanical ventilation was performed by INPV or EHFO. When pulse oximetry was Measurements and results Arterial blood gases were sampled preoperatively and intraoperatively. Most patients in both groups had normal intraoperative Pa co 2 (mean, 43.6 ± 11.8 mm Hg under EHFO and 37.4 ± 8.2 mm Hg under INPV; p = 0.012), and acidemia occurred in 9 of 35 patients of EHFO group and in 2 of 35 patients of INPV group (p = 0.049). Hypercapnia (Pa co 2 > 50 mm Hg) was observed in 10 patients under EHFO and in 2 with INPV (p = 0.026). Intraoperative mean Pa o 2 was similar (101.4 ± 52.9 mm Hg with EHFO and 124.2 ± 50.3 mm Hg with INPV; p = 0.07), but O 2 supply was different (3.5 ± 2.3 L/min during INPV and 8.5 ± 6.2 L/min during EHFO; p o 2 Conclusions External negative pressure ventilation appears to be a suitable choice during rigid bronchoscopy: both EHFO and INPV ensure effective ventilation and comfortable operating conditions in the majority of patients. Some patients may receive inadequate ventilation with EHFO, developing respiratory acidosis and requiring manually assisted ventilation. In comparison with INPV, EHFO requires a higher fraction of inspired oxygen.

Objective. Work of breathing (WoB) is currently employed to assess the afterload on the respiratory muscles and to estimate the energy expenditure for breathing. Since WoB depends on the ventilated tidal volume (TV), WoB*L-1, the indicized form of WoB has been employed as a measure of WoB which is independent of TV. Actually, the independence of WoB*L-1 from the ventilated TV has never been demonstrated. The aim of this study was to verify the predicted TV-independence of WoB*L-1 on an in vitro model. Methods. Our experimental model was constituted as follows: two endotracheal tubes, with internal diameter measuring respectively 6.5 and 8.5 mm, were alternatively connected with two rubber balloons whose compliance was respectively 0.02 and 0.06 L/hPa; the system was mechanically ventilated at ten different tidal volumes, ranging from 0.3–1 l. Flow rate was kept constant (35 l/m) during the whole experiment. Results. Both elastic components of the model showed a static volume–pressure relationship which was linear in the experimental range of TV. In all combinations of resistance and compliance WoB increased quadratically whereas WoB*L-1 increased linearly with the growing TV (p < 0.001). Conclusions. These results demonstrate the TV-dependence of WoB*L-1 and suggest that WoB*L-1, if TV changes, cannot be considered as an index of respiratoy muscle afterload and should not be used as a guide for weaning patients from the mechanical ventilation. Finally, we introduced a new parameter (WoB1L) which seems to be a more TV-independent measure of respiratory work.

Study objective To evaluate the efficacy of negative pressure ventilation (NPV) in avoiding or reducing apneas and related hypoxemia and respiratory acidosis during laser therapy (LT) of endobronchial lesions. Design A prospective, controlled, randomized study. Setting An operating theater of a respiratory endoscopy and laser therapy unit. Population and intervention Twenty-seven consecutive patients referred to LT were entered into the study. Fourteen patients were randomly assigned to LT under general anesthesia and spontaneous assisted ventilation (control group) whereas in 13 cases, NPV by a poncho-wrap ventilator (NPV group) was added to the procedure. Measurements and results The prevalence and the duration of apnea/hypopnea periods assessed by respiratory inductive plethysmography during LT were significantly reduced under NPV, compared to the control group. As compared to baseline, during LT, all control patients developed mild to severe hypercapnia (PaCO2 ranging from 55 to 76 mm Hg) and respiratory acidosis (pH from 7.33 to 7.19), whereas only three patients undergoing NPV (23%) developed hypercapnia (PaCO2 from 52 to 68 mm Hg) and related acidosis (pH from 7.29 to 7.21). Optimal oxygenation was achieved in all of the patients; nevertheless, patients under NPV needed a lower mean oxygen supply; five of them (38%) could be treated at a fraction of inspired oxygen of 0.21 for the whole procedure. Conclusion NPV may be useful in reducing apneas during laser therapy under general anesthesia, thus reducing hypercapnia, related acidosis, and need of oxygen supplementation.

In reply: We are grateful to Dr Appendini and colleagues for their comment and appreciation. The similar expiratory time used in patients with high and low auto-PEEP levels does not diminish the lack of relationship between auto-PEEP and expiratory time (if anything, it made the statistical

Study objective To compare the frequency of airway seal and sore throat with the LMA-ProSeal™ (PLMA) and the standard Laryngeal Mask Airway™ (LMA) during laparoscopic surgery. Design Prospective, controlled, randomized, nonblinded clinical study. Setting University-affiliated hospital. Patients 60 adult, ASA physical status I, II, and III patients undergoing laparoscopic surgery with general anesthesia, without contraindication to the use of the laryngeal mask. Inteventions Patients were randomized to receive mechanical ventilation [tidal volume ( V T ) 7 mL/kg -1 ; positive end-expiratory pressure (PEEP) 10 cmH 2 O] through the PLMA or the standard LMA, both equipped with a gastric tube. Measurements Heart rate, arterial pressure, inspiratory and expiratory V T , airway pressure, end-tidal CO 2 partial pressure, and pulse oximetry were recorded. The leak fraction was calculated as the difference between the inspiratory and expiratory V T divided by the inspiratory V T . Postoperative sore throat frequency was scored in the recovery room ("early") and 1 week after surgery ("late"). Main results All patients were successfully ventilated through the assigned laryngeal mask. The leak fraction was 7 ± 3% with the LMA and 7 ± 4% with the PLMA ( p = 0.731). In one patient, the PLMA drainage tube was not patent despite a leak fraction of 5%, and there was no clinically detectable air leak. During the recovery room stay, the frequency of sore throat was scored as mild in 13% and 10% of patients with the standard LMA and the PLMA, respectively, and was absent in the remaining patients ( p = 0.99, between groups). There were no differences in the frequency of sore throat between the "early" and "late" evaluations ( p = 0.99). Conclusions The PLMA and the LMA show similar airtight efficiency during laparoscopy. The patency of the PLMA drainage tube should always be confirmed. The sore throat evaluation performed in recovery room appears as reliable as later evaluations.

BACKGROUND Ventilation during interventional rigid bronchoscopy (IRB) under general anaesthesia (jet ventilation, positive pressure ventilation and spontaneous assisted ventilation) may offer some difficulties. This study compares the effectiveness during IRB of intermittent negative pressure ventilation (INPV) and spontaneous assisted ventilation (SAV). METHODS Thirty-eight patients submitted to IRB were randomised into two groups: SAV or INPV. All patients received a total intravenous anaesthesia; INPV patients were paralysed. Pre- and intra-operative arterial blood gases and O2 flow through a rigid bronchoscope were assessed. The endoscopist applying a subjective score evaluated the operating conditions. RESULTS Patients of the INPV group, as compared to the SAV group, required a lower dosage of fentanyl (2.6 +/- 1.8 micrograms.kg-1.h-1 vs. 6.6 +/- 4.8 micrograms.kg-1.h-1), a lower O2 supply (3.3 +/- 2.8 l/min vs. 11.6 +/- 3.4 l/min), a shorter recovery time (5.4 +/- 2.9 min vs. 9.8 +/- 7.1 min) and no manually assisted ventilation (0 +/- 0 vs. 1 +/- 1.1 n degree/procedure). Intraoperative PaCO2 was higher in the SAV (8.1 +/- 1.3 kPa) than in the INPV group (5.0 +/- 1.6 kPa) and intraoperative pH differed in the two groups (7.26 +/- 0.05, SAV vs. 7.47 +/- 0.08, INPV). Operating conditions, as assessed by a subjective score, were considered better with INPV than with SAV (4.9 vs. 4.3). CONCLUSIONS As compared to SAV, INPV in paralysed patients during IRB reduces administration of opioids, shortens recovery time, prevents respiratory acidosis, excludes the need for manually assisted ventilation, reduces O2 need and affords optimal surgical conditions. INPV appears a safe, non-invasive and effective ventilatory management during IRB.

The treatment of tracheo-bronchial diseases with rigid bronchoscopy requires general anaesthesia without tracheal intubation. Spontaneous assisted ventilation is a safe modality of ventilation. In this study the use of remifentanil and fentanyl is compared during rigid bronchoscopy with spontaneous assisted ventilation. Ninety high-risk patients received fentanyl or remifentanil with propofol for general anaesthesia. During the maintenance fentanyl was delivered at 6.1 +/- 4.6 micrograms kg-1 h-1 and remifentanil at 0.15 +/- 0.07 microgram kg-1 min-1. The same degree of intra-operative respiratory acidosis with similar good operating conditions resulted in both groups. Patients treated with remifentanil recovered more quickly compared with those in the fentanyl group (3.8 +/- 2 vs. 10.4 +/- 9.2 min, P < 0.001). In conclusion, the use of remifentanil during rigid bronchoscopy under general anaesthesia with spontaneous assisted ventilation is safe and assures good operating conditions. Moreover, remifentanil permits a more rapid recovery than fentanyl. The dose of remifentanil is higher than previously described for spontaneously breathing patients.