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The literature supporting the use of noninvasive ventilatory support (NIV) in acute respiratory failure has markedly increased over the last 20 years.[1][1]–[3][2] Most would now consider NIV as first line therapy in the treatment of COPD exacerbations, cardiogenic pulmonary edema, and acute

Purpose Ineffective respiratory efforts during expiration (IEE) are a problem during mechanical ventilation (MV). The goal of this study is to validate mathematical algorithms that automatically detect IEE in a computerized (Better Care®) system that obtains and processes data from intensive care unit (ICU) ventilators in real time. Methods The Better Care® system, integrated with ICU health information systems, synchronizes and processes data from bedside technology. Algorithms were developed to analyze airflow waveforms during expiration to determine IEE. Data from 2,608,800 breaths from eight patients were recorded. From these breaths 1,024 were randomly selected. Five experts independently analyzed the selected breaths and classified them as IEE or not IEE. Better Care® evaluated the same 1,024 breaths and assigned a score to each one. The IEE score cutoff point was determined based on the experts’ analysis. The IEE algorithm was subsequently validated using the electrical activity of the diaphragm (EAdi) signal to analyze 9,600 breaths in eight additional patients. Results Optimal sensitivity and specificity were achieved by setting the cutoff point for IEE by Better Care® at 42%. A score >42% was classified as an IEE with 91.5% sensitivity, 91.7% specificity, 80.3% positive predictive value (PPV), 96.7% negative predictive value (NPV), and 79.7% Kappa index [confidence interval (CI) (95%) = (75.6%; 83.8%)]. Compared with the EAdi, the IEE algorithm had 65.2% sensitivity, 99.3% specificity, 90.8% PPV, 96.5% NPV, and 73.9% Kappa index [CI (95%) = (71.3%; 76.3%)]. Conclusions In this pilot, Better Care® classified breaths as IEE in close agreement with experts and the EAdi signal.

Manual ventilators (resuscitators) are used primarily to ventilate the lungs of patients lacking spontaneous ventilatory effort. However, in many settings patients are allowed to breathe through the manual ventilator. Although many aspects of manual ventilator function have been studied, very little has been reported on the use of manual ventilators during spontaneous breathing. The purpose of this study was to evaluate inspiratory and expiratory imposed work of breathing and oxygen delivery during spontaneous breathing through disposable manual ventilators.Simulated spontaneous breathing was established with a two-chambered test lung, with one chamber serving as the test chamber and the other as the driving chamber. Imposed work of breathing was evaluated with decelerating inspiratory flow at a rate of 20 breaths/min at tidal volume (VT) 0.25 1 and peak flow 40 l/min, at VT 0.5 l and peak flow 80 l/min, and VT 0.81 and peak flow 120 l/min. Flow (integrated to volume) and pressure were measured between the manual ventilator and test lung, and inspiratory and expiratory imposed work of breathing were calculated by integration of the volume-pressure curve. Oxygen concentration was measured with an oxygen analyzer placed between the manual ventilator and the test lung at 20 breaths/min, VT 0.5 l, and flow 45 l/min. An oxygen flow of 15 l/min was added to the device for all evaluations. Two of the manual ventilators had built-in positive end-expiratory pressure valves, and imposed work was evaluated at 10 cmH2O with these.There were significant differences in imposed work between inspiration and expiration (P0.001) and among the three levels of ventilatory demand (P0.001). For each ventilatory demand, there was a significant difference in work between manual ventilator brands for inspiratory work and expiratory work (P0.001). At a VT of 0.5 l and peak flow of 80 l/min, the pooled inspiratory imposed work for all manual ventilators was 0.44 +/- 0.12 J/l, and the pooled expiratory imposed work was 0.29 +/- 0.05 J/l. With 10 cmH2O positive end-expiratory pressure, the inspiratory imposed work was very high (1 J/l). Four of the devices were unable to deliver more than 0.85 oxygen concentration at the spontaneous ventilatory pattern evaluated.Adult disposable manual ventilators produce a substantial imposed work of spontaneous breathing, which is increased with the addition of positive end-expiratory pressure. With some manual ventilators, a high oxygen concentration may not be delivered during spontaneous breathing. We recommend that patients not be allowed to spontaneously breathe through disposable manual ventilators.

OBJECTIVE To determine which of a series of disposable or interchangeable positive end-expiratory pressure (PEEP) devices functions with the least imposition of inspiratory and expiratory work during continuous positive airway pressure. DESIGN Prospective laboratory evaluation performed on a lung model. SETTING Research laboratory at a university medical center. INTERVENTIONS A spontaneously breathing lung model, created from a training test lung and a volume ventilator, were used to simulate a patient spontaneously breathing at a tidal volume of 0.4 L, peak inspiratory flow of 40 L/min, an inspiration/expiration ratio of 1:2, and a respiratory rate of 20 breaths/min. Ten PEEP valves attached to a continuous high-flow system were evaluated. MEASUREMENTS AND MAIN RESULTS All of the PEEP valves studied imposed high levels of both inspiratory and expiratory work of breathing. The BE-171 and BE-142 valves (Instrumentation Industries) imposed the least amount of inspiratory work. In general, imposed inspiratory work accounted for approximately 70% to 80% of total imposed work of breathing. CONCLUSIONS All of the disposable/interchangeable PEEP valves that were studied imposed a considerable amount of both inspiratory and expiratory work, even when the continuous flow provided exceeded the peak inspiratory flow demands of the lung model. The primary reason for the high imposed work levels is the high gas-flow resistance of all of the valves studied.

OBJECTIVES Flow-triggered continuous positive airway pressure decreases the inspiratory work of breathing in adults when compared with pressure-triggered continuous positive airway pressure. However, the effect of flow-triggered continuous positive airway pressure on work of breathing in neonates is not known. Our objective was to determine if flow-triggering was superior to pressure triggering in the presence of narrow endotracheal tubes, such as those tubes used in neonates. DESIGN Prospective evaluation using within-animal comparison of flow-triggering and pressure-triggering demand flow systems. SETTING The animal laboratory in a university hospital. SUBJECTS Six spontaneously breathing white rabbits, tracheostomized and intubated with 3- and 4-mm inner diameter endotracheal tubes. INTERVENTIONS The animals were connected to a ventilator through a standard respiratory circuit. The ventilator was randomly operated in the following modes: flow-triggered continuous positive airway pressure, pressure-triggered continuous positive airway pressure, flow-triggered with 5 cm H2O pressure support ventilation, and pressure-triggered with 5 cm H2O pressure support ventilation. MEASUREMENTS AND MAIN RESULTS Esophageal pressure, airway pressure, and flow signals were monitored. Control data were obtained while the rabbits were breathing room air through the endotracheal tube. With 3-mm inner diameter endotracheal tubes, the negative deflection of esophageal pressure during flow-triggered continuous positive airway pressure was significantly less than control; however, negative deflection of esophageal pressure during pressure-triggered continuous positive airway pressure did not significantly differ from control. The application of 5 cm H2O pressure support ventilation with flow-triggering decreased negative deflection of esophageal pressure significantly compared with flow-triggered continuous positive airway pressure, pressure-triggered continuous positive airway pressure, and control. With endotracheal tube inner diameter of 4 mm, flow-triggered continuous positive airway pressure and pressure-triggered continuous positive airway pressure did not show any differences compared to control. Negative deflection of esophageal pressure differed under all conditions except control when results with the 3-mm inner diameter endotracheal tube were compared with the 4-mm inner diameter endotracheal tube. CONCLUSIONS Flow-triggering is superior to pressure-triggering in the presence of a 3-mm inner diameter endotracheal tube. This difference was not clear with a 4-mm inner diameter endotracheal tube. The size of the endotracheal tube may be the most important variable in evaluating the approach used to ventilate small neonates.

Background Nitric oxide (NO) inhalation selectively decreases pulmonary artery hypertension and improves arterial oxygenation in patients with the adult respiratory distress syndrome (ARDS). In this study of patients with severe ARDS, we sought to determine the effect of inhaled NO dose and time on pulmonary artery pressure and oxygen exchange and to determine which patients with ARDS are most likely to show this response. Methods Thirteen patients with severe ARDS (hospital mortality 67%) inhaled 0-40 parts per million (ppm) NO. Seven of these patients continued to breathe 2-20 ppm NO for 2-27 days. Results Inhaling 5-40 ppm NO decreased mean pulmonary artery pressure in a dose-related fashion (from 34 +/- 7 to 30 +/- 7 mmHg at 20 ppm NO). Systemic arterial pressure did not change. The ratio of arterial oxygen tension to inspired oxygen fraction increased (from 126 +/- 36 to 149 +/- 38 mmHg) and the venous admixture decreased (from 31.2 +/- 5.5 to 28.2 +/- 5.2%) without a clear dose-response effect. During prolonged NO inhalation, 2-20 ppm NO effectively reduced mean pulmonary artery pressure (38 +/- 7 vs. 31 +/- 6 mmHg) and increased arterial oxygen tension (79 +/- 10 vs. 114 +/- 27 mmHg) without evidence of tachyphylaxis. The decrease of pulmonary vascular resistance during NO inhalation correlated with the level of pulmonary vascular resistance without NO (r = -0.72). The reduction of venous admixture correlated with the level of venous admixture without NO (r = -0.78). Conclusions Long-term NO inhalation at low concentrations selectively decreases mean pulmonary artery pressure and improves arterial oxygen tension in patients with ARDS. The selective pulmonary vasodilation effect is most pronounced in ARDS patients with the greatest degree of pulmonary vasoconstriction.

Information and opinions were sought on the need for graduating and practicing respiratory therapists to obtain 66 competencies necessary for practice in 2015 and beyond, the required length of respiratory care programs, the educational needs of practicing therapists, current and future workforce positions, and the appropriate credential needed by graduating therapists.Survey responses from respiratory therapy department directors or managers are the basis of this report. After pilot testing and refining the questions, a self-administered, Internet based, American Association for Respiratory Care (AARC) endorsed survey was used to gather information from 2,368 individuals designated as respiratory therapy department directors or managers in the AARC membership list as of May 2010.A total of 663 valid survey responses (28.0%) were received. On average, the vacancy rate of surveyed hospitals was only 0.81 full-time equivalents (FTEs). Responses by directors on 66 competencies described in the second 2015 conference as needed by graduate and practicing respiratory therapists indicated 90% agreement on 37, between 50% and 90% agreement on 25, and50% agreement on 4 competencies. There was no consensus among directors on the academic preparation of new graduates, with 245 (36.8%) indicating a preference for a baccalaureate or master's degree, 243 (36.7%) indicating a preference for an associate degree, and 176 (26.5%) indicating no preference. There were 270 (41.8%) respondents who indicated that a baccalaureate or master's degree in respiratory therapy should be required to qualify for a license to deliver respiratory care. The survey indicated that 523 (81.2%) of directors are in favor of the RRT credential being required to practice in 2015 and beyond.There was good agreement that graduate and practicing therapists should obtain the vast majority of the 66 competencies surveyed and that the entry level credential should be the RRT. Similar numbers of managers favored an entry level baccalaureate degree as favored an associate degree.

Background Mechanical ventilation (MV) with high tidal volumes (VT) can cause or aggravate lung damage, so-called ventilator induced lung injury (VILI). The relationship between specific mechanical events in the lung and the cellular responses that result in VILI remains incomplete. Since activation of Wnt/β-catenin signaling has been suggested to be central to mechanisms of lung healing and fibrosis, we hypothesized that the Wnt/β-catenin signaling plays a role during VILI. Methodology/Principal Findings Prospective, randomized, controlled animal study using adult, healthy, male Sprague-Dawley rats. Animals (n = 6/group) were randomized to spontaneous breathing or two strategies of MV for 4 hours: low tidal volume (VT) (6 mL/kg) or high VT (20 mL/kg). Histological evaluation of lung tissue, measurements of WNT5A, total β-catenin, non-phospho (Ser33/37/Thr41) β-catenin, matrix metalloproteinase-7 (MMP-7), cyclin D1, vascular endothelial growth factor (VEGF), and axis inhibition protein 2 (AXIN2) protein levels by Western blot, and WNT5A, non-phospho (Ser33/37/Thr41) β-catenin, MMP-7, and AXIN2 immunohistochemical localization in the lungs were analyzed. High-VT MV caused lung inflammation and perivascular edema with cellular infiltrates and collagen deposition. Protein levels of WNT5A, non-phospho (Ser33/37/Thr41) β-catenin, MMP-7, cyclin D1, VEGF, and AXIN2 in the lungs were increased in all ventilated animals although high-VT MV was associated with significantly higher levels of WNT5A, non-phospho (Ser33/37/Thr41) β-catenin, MMP-7, cyclin D1, VEGF, and AXIN2 levels. Conclusions/Significance Our findings demonstrate that the Wnt/β-catenin signaling pathway is modulated very early by MV in lungs without preexistent lung disease, suggesting that activation of this pathway could play an important role in both VILI and lung repair. Modulation of this pathway might represent a therapeutic option for prevention and/or management of VILI.

Our aim was to compare adaptive support ventilation with and without closed loop control by end tidal CO2 (ASVCO2, ASV) with pressure (PC) and volume control ventilation (VC) during simulated clinical scenarios [normal lungs (N), COPD, ARDS, brain injury (BI)].A lung model was used to simulate representative compliance (mL/cmH2O): resistance (cmH2O/L/s) combinations, 45:5 for N and BI, 60:7.7 for COPD, 15:7.7 and 35:7.7 for ARDS. Two levels of PEEP (cmH2O) were used for each scenario, 12/16 for ARDS, and 5/10 for others. The CO2 productions of 2, 3, 4 and 5 mL/kg predicted body weight/min were simulated. Tidal volume was set to 6 mL/kg during VC and PC. Outcomes of interest were end tidal CO2 (etCO2) and plateau pressure (P Plat).EtCO2 levels in N and BI and COPD were similar for all modes. In ARDS, etCO2 was higher in ASVCO2 than in other modes (p0.001). Under all mechanical conditions ASVCO2 revealed a narrower range of etCO2. P Plat was similar for all modes in all scenarios but ARDS where P Plat in ASV and ASVCO2 were lower than in VC (p = 0.001). When P Plat was ≥ 28 cmH2O, P plat in ASV and ASVCO2 were lower than in VC and PC (p = 0.024).All modes performed similarly in most cases. Minor differences observed were in favor of the closed loop modes. Overall, ASVCO2 maintained tighter CO2 control. The ASVCO2 had the greatest impact during ARDS allowing etCO2 to increase and protecting against hypocapnia evident with other modes while ensuring lower P plat and tidal volumes.

As background for the American Association for Respiratory Care (AARC) third 2015 and Beyond conference, we sought information and opinions on the ability of the current respiratory therapy education infrastructure to make changes that would assure competent respiratory therapists in the envisioned healthcare future.After pilot testing and refining the questions, we invited the directors of 435 respiratory therapy programs (based in 411 colleges) that were fully accredited or in the process of being accredited by the Commission on Accreditation for Respiratory Care as of May, 2010, to participate in the survey.Three-hundred forty-eight program directors (80%) provided valid survey responses. Three of the 5 competencies related to evidence-based medicine and respiratory care protocols were taught less often in the associate-degree programs than in the baccalaureate-degree programs. Eighty percent of the baccalaureate-degree programs, compared to 42% of the associate-degree programs, instruct students how to critique published research (P.001). Only 34% of the associate-degree programs teach students the general meaning of statistical tests, compared to 78% of the baccalaureate-degree programs (P.001). Ninety-four percent of the baccalaureate-degree programs, versus 81% of the associate-degree programs, teach the students to apply evidence-based medicine to clinical practice (P = .01). Teaching students how to describe healthcare and financial reimbursement systems and the need to reduce the cost of delivering respiratory care (a leadership competency identified by the second 2015 and Beyond conference) was significantly more common in the baccalaureate-degree programs (72%) than in the associate-degree programs (56%) (P = .03). Other competencies showed trends toward differences, and the baccalaureate-degree programs reported higher percentages of success than the associate-degree programs.There are important differences between the baccalaureate-degree and associate-degree programs.

BACKGROUND: Intensive-care mechanical ventilators regularly enter the market, but the gas-delivery capabilities of many have never been assessed. METHODS: We evaluated 6 intensive-care ventilators in the pressure support (PS), pressure assist/control (PA/C), and volume assist/control (VA/C) modes, with lung-model mechanics combinations of compliance and resistance of 60 mL/cm H2O and 10 cm H2O/L/s, 60 mL/cm H2O and 5 cm H2O/L/s, and 30 mL/cm H2O and 10 cm H2O/L/s, and inspiratory muscle effort of 5 and 10 cm H2O. PS and PA/C were set to 15 cm H2O, and PEEP to 5 and 15 cm H2O in all modes. During VA/C, tidal volume was set at 500 mL and inspiratory time was set at 0.8 second. Rise time and termination criteria were set at the manufacturers9 defaults, and to an optimal level during PS and PA/C. RESULTS: There were marked differences in ventilator performance in all 3 modes. VA/C had the greatest difficulty meeting lung model demand and the greatest variability across all tested scenarios and ventilators. From high to low inspiratory muscle effort, pressure-to-trigger, time for pressure to return to baseline, and triggering pressure-time product decreased in all modes. With increasing resistance and decreasing compliance, tidal volume, pressure-to-trigger, time-to-trigger, time for pressure to return to baseline, time to 90% of peak pressure, and pressure-time product decreased. There were large differences between the default and optimal settings for all the variables in PS and PA/C. Performance was not affected by PEEP. CONCLUSIONS: Most of the tested ventilators performed at an acceptable level during the majority of evaluations, but some ventilators performed inadequately during specific settings. Bedside clinical evaluation is needed.

The American Association for Respiratory Care established a task force in late 2007 to identify likely new roles and responsibilities of respiratory therapists (RTs) in the year 2015 and beyond. A series of 3 conferences was held between 2008 and 2010. The first task force conference affirmed that the healthcare system is in the process of dramatic change, driven by the need to improve health while decreasing costs and improving quality. This will be facilitated by application of evidence-based care, prevention and management of disease, and closely integrated interdisciplinary care teams. The second task force conference identified specific competencies needed to assure safe and effective execution of RT roles and responsibilities in the future. The third task force conference was charged with creating plans to change the professional education process so that RTs are able to achieve the needed skills, attitudes, and competencies identified in the previous conferences. Transition plans were developed by participants after review and discussion of the outcomes of the first two conferences and 1,011 survey responses from RT department managers and RT education program directors. This is a report of the recommendations of the third task force conference held July 12-14, 2010, on Marco Island, Florida. The participants, who represented groups concerned with RT education, licensure, and practice, proposed, discussed, and accepted that to be successful in the future a baccalaureate degree must be the minimum entry level for respiratory care practice. Also accepted was the recommendation that the Certified Respiratory Therapist examination be retired, and instead, passing of the Registered Respiratory Therapist examination will be required for beginning clinical practice. A date of 2020 for achieving these changes was proposed, debated, and accepted. Recommendations were approved requesting resources be provided to help RT education programs, existing RT workforce, and state societies work through the issues raised by these changes.

BACKGROUND: Predicting mortality has become a necessary step for selecting patients for clinical trials and defining outcomes. We examined whether stratification by tertiles of respiratory and ventilatory variables at the onset of acute respiratory distress syndrome (ARDS) identifies patients with different risks of death in the intensive care unit. METHODS: We performed a secondary analysis of data from 220 patients included in 2 multicenter prospective independent trials of ARDS patients mechanically ventilated with a lung-protective strategy. Using demographic, pulmonary, and ventilation data collected at ARDS onset, we derived and validated a simple prediction model based on a population-based stratification of variable values into low, middle, and high tertiles. The derivation cohort included 170 patients (all from one trial) and the validation cohort included 50 patients (all from a second trial). RESULTS: Tertile distribution for age, plateau airway pressure (Pplat), and PaO2/FIO2 at ARDS onset identified subgroups with different mortalities, particularly for the highest-risk tertiles: age (> 62 years), Pplat (> 29 cm H2O), and PaO2/FIO2 (< 112 mm Hg). Risk was defined by the number of coexisting high-risk tertiles: patients with no high-risk tertiles had a mortality of 12%, whereas patients with 3 high-risk tertiles had 90% mortality ( P < .001). CONCLUSIONS: A prediction model based on tertiles of patient age, Pplat, and PaO2/FIO2 at the time the patient meets ARDS criteria identifies patients with the lowest and highest risk of intensive care unit death.

Since the first description of the acute respiratory distress syndrome (ARDS) in 1967, no specific clinical sign or diagnostic test has yet been described that identifies ARDS. Its diagnosis is based on a combination of clinical, hemodynamic, and oxygenation criteria. The purpose of this review is to examine the current definition for ARDS and to discuss why this definition may not be the most appropriate definition for this syndrome.We will briefly review our current understanding of ARDS, discuss the problems with its current diagnosis, and present clinical, pathological, and biochemical evidences supporting a more appropriate definition for ARDS. In addition, we will discuss recent efforts to identify biological markers for lung injury in pulmonary edema fluid and blood collected from critically ill patients.On the basis of current evidence, it is time for a change in the ARDS definition. A newer classification system that recognizes different severities of pulmonary dysfunction is needed. Such a system should be able to identify patients that would be most responsive to supportive therapies and those unlikely to benefit because of the severity of their disease.

Mechanical ventilation is the most important aspect of supportive care of patients with severe acute respiratory failure. Most research directed to improving the prognosis of these patients has focused on improving support of the injured lung. In this report, current knowledge on innovative ways to manage refractory hypoxemia and ventilation without further damaging the injured lung is briefly discussed.

The mechanisms involved in lung injury progression during acute lung injury (ALI) are still poorly understood. Because WNT/β-catenin signaling has been shown to be involved in epithelial cell injury and hyperplasia during inflammation and sepsis, we hypothesized that it would be modulated by mechanical ventilation (MV) in an experimental model of sepsis-induced ALI.This study was a prospective, randomized, controlled animal study performed using adult male Sprague-Dawley rats. Sepsis was induced by cecal ligation and perforation. At 18 h, surviving animals were randomized to spontaneous breathing or two strategies of MV for 4 h: low tidal volume (V (T)) (6 ml/kg) plus 10 cmH2O of positive end-expiratory pressure (PEEP) versus high (20 ml/kg) tidal volume (V (T)) with zero PEEP. Histological evaluation, measurements of WNT5A, total β-catenin, and matrix metalloproteinase-7 (MMP7) protein levels by Western blot, and their immunohistochemical localization in the lungs were analyzed.Sepsis and high-V (T) MV caused lung inflammation and perivascular edema with cellular infiltrates and collagen deposition. Protein levels of WNT5A, β-catenin, and MMP7 in the lungs were increased in animals with sepsis-induced ALI. High-V (T) MV was associated with higher levels of WNT5A, β-catenin, and MMP7 protein levels (p0.001), compared to healthy control animals. By contrast, low-V (T) MV markedly reduced WNT5A, β-catenin, and MMP7 protein levels (p0.001).Our findings demonstrate that the WNT/β-catenin signaling pathway is modulated early during sepsis and ventilator-induced lung injury, suggesting that activation of this pathway could play an important role in both lung injury progression and repair.

The American Association for Respiratory Care has established a task force to identify potential new roles and responsibilities of respiratory therapists (RTs) in 2015 and beyond. The first task force conference confirmed that the healthcare system in the United States is on the verge of dramatic change, driven by the need to decrease costs and improve quality. Use of evidence-based protocols that follow a nationally accepted standard of practice, and application of biomedical innovation continue to be important competency areas for RTs. The goal of the second task force conference was to identify specific competencies needed to assure safe and effective execution of RT roles and responsibilities in the future. The education needed by the workforce to assume the new responsibilities emerging as the healthcare system changes starts with a close look at the competencies that will be needed by graduate RTs upon entry into practice. Future specialty practice areas for experienced RTs are identified without defining specific competencies. We present the findings of the task force on the competencies needed by graduate RTs upon entry into practice in 2015.

Aminophylline has been reported to augment diaphragmatic contraction, although this remains a controversial finding. We studied the effect of aminophylline on regional diaphragmatic shortening, changes in transdiaphragmatic pressure (delta Pdi), and integrated regional electromyographic (EMG) activity of the diaphragm (Edi) after a right thoracotomy in nine lambs using sonomicrometry, esophageal and gastric balloons, and EMG. Sonomicrometer crystals and EMG leads were implanted into the costal and crural regions of the diaphragm through a right thoracotomy, and a tracheostomy was performed. The animals were studied while awake within 4 days after surgery. Fractional costal and crural diaphragmatic shortening was measured using the sonomicrometer; delta Pdi was calculated from esophageal and gastric pressures. Respiratory variables were measured through the tracheostomy. Data were collected during quiet breathing and during CO2 rebreathing. After control measurements, aminophylline (10 mg/kg) was administered intravenously, producing a serum concentration of 17.7 +/- 1.5 micrograms/ml. Aminophylline did not augment shortening, increase delta Pdi, or overcome postoperative diaphragmatic inhibition acutely in the awake sheep after a right lateral thoracotomy. A small decrease of end-tidal CO2, from 5.2% to 4.9%, was measured at rest during aminophylline infusion, but Edi was unchanged. Although during CO2 rebreathing diaphragmatic shortening increased, the addition of aminophylline did not further augment shortening. Our data in awake lambs suggest that aminophylline does not improve diaphragmatic contraction in the acute postoperative period.

The use of home mechanical ventilation has increasingly become commonplace in the management of patients with chronic neuromuscular ventilatory failure. Numerous approaches to the application of ventilatory support, both invasive and noninvasive, are currently available. These range from providing standard invasive intermittent positive pressure mechanical ventilation (IPPV) via an indwelling tracheostomy tube to the use of negative pressure body ventilators (NPBVs), intermittent abdominal pressure ventilators (IAPVs), rocking beds, and noninvasive IPPV techniques. This paper discusses the technical operation and limitations of current positive pressure ventilators. Additionally, clinical application methodology in various settings is detailed.

BackgroundThere is a need for biomarkers insuring identification of septic patients at high-risk for death. We performed a prospective, multicenter, observational study to investigate the time-course of lipopolysaccharide binding protein (LBP) serum levels in patients with severe sepsis and examined whether serial serum levels of LBP could be used as a marker of outcome.Methodology/principal findingsLBP serum levels at study entry, at 48 hours and at day-7 were measured in 180 patients with severe sepsis. Data regarding the nature of infections, disease severity, development of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS), and intensive care unit (ICU) outcome were recorded. LBP serum levels were similar in survivors and non-survivors at study entry (117.4+/-75.7 microg/mL vs. 129.8+/-71.3 microg/mL, P = 0.249) but there were significant differences at 48 hours (77.2+/-57.0 vs. 121.2+/-73.4 microg/mL, PConclusions/significanceSerial LBP serum measurements may offer a clinically useful biomarker for identification of patients with severe sepsis having the worst outcomes and the highest probability of developing sepsis-induced ARDS.

Noninvasive positive-pressure ventilation (NPPV) modes are currently available on bilevel and ICU ventilators. However, little data comparing the performance of the NPPV modes on these ventilators are available.In an experimental bench study, the ability of nine ICU ventilators to function in the presence of leaks was compared with a bilevel ventilator using the IngMar ASL5000 lung simulator (IngMar Medical; Pittsburgh, PA) set at a compliance of 60 mL/cm H(2)O, an inspiratory resistance of 10 cm H(2)O/L/s, an expiratory resistance of 20 cm H(2)O/ L/s, and a respiratory rate of 15 breaths/min. All of the ventilators were set at 12 cm H(2)O pressure support and 5 cm H(2)O positive end-expiratory pressure. The data were collected at baseline and at three customized leaks.At baseline, all of the ventilators were able to deliver adequate tidal volumes, to maintain airway pressure, and to synchronize with the simulator, without missed efforts or auto-triggering. As the leak was increased, all of the ventilators (except the Vision [Respironics; Murrysville, PA] and Servo I [Maquet; Solna, Sweden]) needed adjustment of sensitivity or cycling criteria to maintain adequate ventilation, and some transitioned to backup ventilation. Significant differences in triggering and cycling were observed between the Servo I and the Vision ventilators.The Vision and Servo I were the only ventilators that required no adjustments as they adapted to increasing leaks. There were differences in performance between these two ventilators, although the clinical significance of these differences is unclear. Clinicians should be aware that in the presence of leaks, most ICU ventilators require adjustments to maintain an adequate tidal volume.

Previous experimental studies of ventilator-induced lung injury have shown that positive end-expiratory pressure (PEEP) is protective. The authors hypothesized that the application of PEEP during volume-controlled ventilation with a moderately high tidal volume (VT) in previously healthy in vivo rats does not attenuate ventilator-induced lung injury if the peak airway pressure markedly increases during the application of PEEP.Sixty healthy, male Sprague-Dawley rats were anesthetized and randomized to be mechanically ventilated for 4 h at (1) VT of 6 ml/kg, (2) VT of 20 ml/kg, or (3) VT of 20 ml/kg plus 10 cm H2O of PEEP. Peak airway pressures, gas exchange, histologic evaluation, mortality, total lung tissue cytokine gene expression, and serum cytokine concentrations were analyzed.Peak airway pressures exceeded 30 cm H2O with high VT plus PEEP. All lungs ventilated with high VT had perivascular edema and inflammatory infiltrates. In addition, those ventilated with PEEP had small hemorrhages foci. Five animals from the high VT plus PEEP group died (P = 0.020). Animals ventilated with high VT (with or without PEEP) had a substantial increase in serum interleukin-6 (P = 0.0002), and those ventilated with high VT plus PEEP had a 5.5-fold increase in systemic levels of tumor necrosis factor-alpha (P = 0.007).In contrast to previous reports, PEEP exacerbated lung damage and contributed to fatal outcome in an in vivo, mild overdistension model of ventilator-induced lung injury in previously healthy rats. That is, the addition of high PEEP to a constant large VT causes injury in previously healthy animals.

The respiratory care profession is over 60 years old. Throughout its short history, change and innovation have been the terms that best describe the development of the profession. The respiratory therapist (RT) of today barely resembles the clinicians of 60 years ago, and the future role of the RT is clearly open to debate. Medicine is continually changing, with new approaches to disease management emerging almost daily. Third-party payers are challenging payment for iatrogenic injury, manpower issues are affecting all disciplines in medicine, and the nonphysician and physician work force is aging. These factors make us question what the respiratory care profession will look like in the year 2015. To address this issue the American Association for Respiratory Care established a task force to envision the RT of the future. The goal is to identify potential new roles and responsibilities of RTs in 2015 and beyond, and to suggest the elements of education, training, and competency-documentation needed to assure safe and effective execution of those roles and responsibilities. We present the initial findings of that task force.

Most of the large quantity of data on noninvasive ventilation (NIV) in acute respiratory failure is from patients who want all possible treatments and life-support. Few data are available on NIV in patients who have elected specific limits on life support and treatments (eg, patients with do-not-intubate [DNI] orders) and patients who are near the end of life and will receive comfort measures only (CMO). The most critical issue regarding NIV in DNI and CMO patients is informed consent. The patient must be informed of the risks and potential benefits of NIV, and must consent to NIV. We have few data on patients' attitudes about NIV at end of life. Data from cancer patients at end of life suggest that they want to maintain control over care decisions and may want treatment that delays death long enough that they can put their affairs in order. If informed consent and control of care decisions are assured, then NIV can be appropriate in DNI and CMO patients to reverse an acute respiratory failure that is not necessarily life-terminating, or to improve patient comfort, or to delay death.

To correlate wheeze detection in the pediatric intensive care unit among staff members (a physician, nurses, and respiratory therapists [RTs]) and digital recordings from a computerized respiratory sound monitor (PulmoTrack).We prospectively studied 11 patients in the pediatric intensive care unit. A physician, nurses, and RTs auscultated the patients and recorded their opinions about the presence of wheeze at baseline and then every hour for 6 hours. The clinician auscultated while the PulmoTrack recorded the lung sounds. The data were analyzed by a technician trained in interpretation of acoustic data and by a panel of experts blinded to the source of the recorded data, who scored all tracks for the presence or absence of wheeze. The degree of correlation among the expert panel, the staff, and the PulmoTrack was evaluated with the Kappa coefficient and McNemar's test. The determinations of the expert panel were taken as the true state (accepted standard).The PulmoTrack and expert panel were in agreement on detection of wheeze during inspiration, expiration, and the whole breath cycle; in all cases the Kappa coefficients were 0.54, 0.42, and 0.50 respectively. The PulmoTrack was significantly more sensitive than the physician (P = .002), nurses (P.001), or RTs (P = .001). However, the specificity of the PulmoTrack was not significantly different from that of the physician, nurses, or RTs.Between the physician, RTs, and nurses there was agreement about the presence of wheeze in critically ill patients in the pediatric intensive care unit. Compared to the objective acoustic measurements from the PulmoTrack, the intensive care unit staff was similar in their ability to detect the absence of wheeze. The PulmoTrack was better than the staff in detecting wheeze.

Upper airway unidirectional breathing, nose in and mouth out, is used by panting dogs to facilitate heat removal via water evaporation from the respiratory system. Why some humans instinctively employ the same breathing pattern during respiratory distress is still open to question. We hypothesized that 1) humans unconsciously perform unidirectional breathing because it improves breathing efficiency, 2) such an improvement is achieved by bypassing upper airway dead space, and 3) the magnitude of the improvement is inversely proportional to the tidal volume. Four breathing patterns were performed in random order in 10 healthy volunteers first with normal breathing effort, then with variable tidal volumes: mouth in and mouth out (MMB); nose in and nose out (NNB); nose in and mouth out (NMB); and mouth in and nose out (MNB). We found that unidirectional breathing bypasses anatomical dead space and improves breathing efficiency. At tidal volumes of ∼380 ml, the functional anatomical dead space during NMB (81 ± 31 ml) or MNB (101 ± 20 ml) was significantly lower than that during MMB (148 ± 15 ml) or NNB (130 ± 13 ml) (all P < 0.001), and the breathing efficiency obtained with NMB (78 ± 9%) or MNB (73 ± 6%) was significantly higher than that with MMB (61 ± 6%) or NNB (66 ± 3%) (all P < 0.001). The improvement in breathing efficiency increased as tidal volume decreased. Unidirectional breathing results in a significant reduction in functional anatomical dead space and improvement in breathing efficiency. We suggest this may be the reason that such a breathing pattern is preferred during respiratory distress.

This article review available strategies for mechanically ventilating patients with the adult respiratory distress syndrome. The authors first present the conventional strategies of mechanical ventilation: volume-limited mechanical ventilation with positive end-expiratory pressure (PEEP) at normal inspiratory-expiratory ratios, the approach that has been the mainstay of ventilatory support since the initial description of PEEP. This discussion attempts to summarize the rationale and goals of treatment in a practical, clinically useful manner. The second section of the article reviews less conventional ventilatory approaches, including inverse ratio ventilation, extracorporeal techniques, high-frequency ventilation, prone position, and fluctuating PEEP, and attempts to review critically the available literature regarding their application.

The newest generation of mechanical ventilators has allowed increased flexibility and enhanced mechanical performance. Primary advantages of these units are improved interfacing during spontaneous breathing, improved monitoring capabilities, and increased safety by the addition of apnea/back-up ventilation during all spontaneous breathing modes. The major drawbacks of these units are their operational complexity and the inclusion of a large number of highly sensitive alarms. Finally, in spite of the scope and capabilities of these ventilators, the vast majority of patients can be very capably managed with the "mid-range" ventilators discussed as well as the majority of well maintained older generation ventilators. All the bells and whistles available on top-of-the-line units do not necessarily constitute an improvement in patient care.

Noninvasive positive-pressure ventilation (NPPV) has been shown to be effective in select patients enrolled in clinical trials. However, few data are available on the use of NPPV as routine standard medical care for patients with respiratory failure outside of controlled trials.All patients receiving NPPV for a 1-yr period for acute or acute on chronic respiratory failure who did not select do not intubate/resuscitate status were evaluated. Demographic, physiological, and laboratory data were collected for as long as NPPV was provided. Data were recorded on 449 patients. Intubation rate was 18%, 24%, 38%, 40%, and 60%, respectively, for patients with cardiogenic pulmonary edema (n = 97), acute exacerbation of chronic obstructive pulmonary disease (n = 87), non-chronic obstructive pulmonary disease acute hypercapnic respiratory failure (n = 35), postextubation respiratory failure patients (n = 95), and acute hypoxemic respiratory failure (n = 144). The hospital mortality for patients with acute hypoxemic respiratory failure who failed NPPV was 64%. A logistic regression showed that baseline Simplified Acute Physiology Score II (odds ratio [OR], 1.07; 95% confidence interval [CI], 1.05-1.10; p.0001), Glasgow Coma Scale (OR, 0.76; 95% CI, 0.66-0.87; p.0001), PaO2/FIO2 ratio (OR, 0.98; 95% CI, 0.93-0.99; p = .02), and serum albumin (OR, 0.30; 95% CI, 0.16-0.57; p.001) were the variables associated with NPPV failure.NPPV as routine standard medical care resulted in the intubation of a similar percentage of patients with respiratory failure due to cardiogenic pulmonary edema and chronic obstructive pulmonary disease exacerbation as shown in randomized controlled trials but in a higher percent of patients with hypoxemic respiratory failure than reported in these trials. NPPV failure was associated with high hospital mortality for patients with hypoxemic respiratory failure.

Mechanical ventilation is frequently required to maintain gas exchange in patients with severe acute respiratory failure. Evidence suggests that lung heterogeneity may contribute to major shear forces within the lung parenchyma, leading many intensivists to use the strategy of open lung protective ventilation (i.e., “open the lung and keep it open”) to promote homogeneity. Thus, there has been considerable interest in the impact of various interventions on lung recruitment and alveolar collapse, particularly when surface tension is high. Disconnecting the endotracheal tube from the ventilator circuit may cause substantial loss of lung volume, which is further exacerbated by suctioning. In-line closed suction systems have the advantage over open suctioning in maintaining lung volume. However, there are risks associated with closed suction: generation of large negative airway pressures and auto-cycling of the ventilator (1). Fernandez et al. (2) demonstrated reductions in lung volume during both quasi-closed and closed system suctioning but significantly greater loss of lung volume with the open system. In addition, open suctioning may lead to a marked decrease in arterial oxygen tension and increase in arterial carbon dioxide tension (3). During open suctioning, there is still controversy over the impact of the duration of suctioning on gas exchange. During bronchoscopy, suctioning is frequently applied to remove secretions and lavage fluid. In addition, gas exchange is relatively ineffective during the procedure (4). Ongoing blood flow to the lung further diminishes lung volume due to oxygen absorption. During such a “breath hold,” the majority of CO2 is buffered in the periphery and not removed by the lung. As a result, end-expiratory lung volume would be predicted to diminish substantially as a result of gas suctioning through the bronchoscope as well as gas absorption through the circulation during the procedure. However, minimal data are available regarding how the duration of bronchoscopy influences the resulting gas exchange abnormalities. Moreover, the majority of studies were not performed using protective mechanical ventilator strategies, such as permissive hypercapnia. Previously, we have shown (5) marked increases of PaCO2 10 mins following suctioning during lung-protective ventilation. The goal of this physiologic study was to determine whether baseline PaCO2 or duration of suctioning influenced the degree of gas exchange abnormality that occurred following open suctioning in acute respiratory distress syndrome (ARDS).

To understand the reported practices of and adherence to evidence-based guidelines for the prevention of ventilator-associated pneumonia (VAP) among respiratory therapists (RTs) and registered nurses (RNs) in academic and nonacademic intensive care units.We conducted a multicenter, cross-sectional survey. We first obtained demographic information about health care professionals in a nonidentifiable method. We next questioned the practice patterns of RTs and RNs for preventing VAP based on evidence-supported guidelines. The participants were RTs and RNs working in academic and nonacademic intensive care units; 278 respondents participated in this study (172 RTs and 106 RNs). There were no interventions.The 3 major findings were: (1) both the RTs and the RNs reported that they frequently practice VAP-prevention measures, (2) the rate of adherence to ineffective measures (eg, routine changes of the ventilator circuit, disposable catheters) is also relatively high, which suggests that the evidence is not translated into bedside practice, (3) a substantial proportion of participants did not know the VAP rate in their institution, which might make it difficult to convince bedside practitioners to apply evidence-based practice, and might reflect a lack of infection-control/surveillance programs at hospitals.Consumers, the Centers for Disease Control and Prevention, and other organizations are currently trying to implement mandatory reporting of hospital infections, including VAP rate. Without a definition of VAP suited to individual institutions, an organized data-collection and reporting method, and team-based approaches to preventing and treating VAP, hospitals may not be able to meet these requests and track improvement efforts. Prevention measures need to be translated to bedside practice to improve the outcomes of critically ill patients.

To compare the triggering performance of mid-level ICU mechanical ventilators with a standard ICU mechanical ventilator. Experimental bench study. The respiratory care laboratory of a university-affiliated teaching hospital. A computerized mechanical lung model, the IngMar ASL5000. Ten mid-level ICU ventilators were compared to an ICU ventilator at two levels of lung model effort, three combinations of respiratory mechanics (normal, COPD and ARDS) and two modes of ventilation, volume and pressure assist/control. A total of 12 conditions were compared. Performance varied widely among ventilators. Mean inspiratory trigger time was

Over the last 2 decades, it has become clear that mechanical ventilation itself can cause lung injury and affect outcome. The development of ventilator-induced lung injury is strongly associated with overdistension of lung parenchyma, and limiting lung stretch saves lives in patients with acute lung injury. The debate in this paper is whether all patients on mechanical ventilation should be managed with a tidal volume (V(T)) of 6 mL/kg predicted body weight. Current data indicate that reducing lung stretch should be the standard for all patients with acute lung injury and acute respiratory distress syndrome who require ventilatory support. However, insufficient data exist to indicate that a V(T) of 6 mL/kg predicted body weight should be the standard for all patients who require mechanical ventilation. Whether V(T) is the correct target for therapeutic interventions is debatable. Plateau pressure may be a better target for assessing and preventing alveolar over-distension. As the data evolve, it is conceivable that the actual V(T) used should be based on the individual patient's lung mechanics rather than assuming that one V(T) will suit all patients. Consensus at this time is not possible, and this paper presents the arguments on both sides of the controversy.

Lung recruitment maneuvers are being used in the management of acute lung injury and acute respiratory distress syndrome, but recruitment maneuvers are controversial. The proponents argue that when properly applied to appropriately selected patients, they are effective and can be safely applied. The expectation is that the recruitment maneuver will change the course of ARDS and improve outcomes. Those opposed to recruitment maneuvers argue that no data indicate better outcomes with recruitment maneuvers and that they are potentially unsafe. Outcome data are clearly needed before recruitment maneuvers can be fully incorporated into clinical practice. If a recruitment maneuver is conducted, a decremental positive end-expiratory pressure (PEEP) trial must be done to determine the minimum PEEP that sustains the benefits of the recruitment maneuver. We explore both sides of the lung recruitment controversy.

To the Editor: We read with interest the comments and suggestions of Dr Sangwan; however, a number of the issues he raised need to be clarified. A fiberoptic bronchoscope is commonly used during percutaneous dilatational tracheostomy (PDT) throughout Europe.[1][1] Recent surveys performed in