Mean Airway Pressure As a Predictor of 90-Day Mortality in Mechanically Ventilated Patients.

OBJECTIVES: To determine the association between mean airway pressure and 90-day mortality in patients with acute respiratory failure requiring mechanical ventilation and to compare the predictive ability of mean airway pressure compared with inspiratory plateau pressure and driving pressure. DESIGN: Prospective observational cohort. SETTING: Five ICUs in Lima, Peru. SUBJECTS: Adults requiring invasive mechanical ventilation via endotracheal tube for acute respiratory failure. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Of potentially eligible participants (n = 1,500), 65 (4%) were missing baseline mean airway pressure, while 352 (23.5%) were missing baseline plateau pressure and driving pressure. Ultimately, 1,429 participants were included in the analysis with an average age of 59 ± 19 years, 45% female, and a mean PaO2/FIO2 ratio of 248 ± 147 mm Hg at baseline. Overall, 90-day mortality was 50.4%. Median baseline mean airway pressure was 13 cm H2O (interquartile range, 10-16 cm H2O) in participants who died compared to a median mean airway pressure of 12 cm H2O (interquartile range, 10-14 cm H2O) in participants who survived greater than 90 days (p < 0.001). Mean airway pressure was independently associated with 90-day mortality (odds ratio, 1.38 for difference comparing the 75th to the 25th percentile for mean airway pressure; 95% CI, 1.10-1.74) after adjusting for age, sex, baseline Acute Physiology and Chronic Health Evaluation III, baseline PaO2/FIO2 (modeled with restricted cubic spline), baseline positive end-expiratory pressure, baseline tidal volume, and hospital site. In predicting 90-day mortality, baseline mean airway pressure demonstrated similar discriminative ability (adjusted area under the curve = 0.69) and calibration characteristics as baseline plateau pressure and driving pressure. CONCLUSIONS: In a multicenter prospective cohort, baseline mean airway pressure was independently associated with 90-day mortality in mechanically ventilated participants and predicts mortality similarly to plateau pressure and driving pressure. Because mean airway pressure is readily available on all mechanically ventilated patients and all ventilator modes, it is a potentially more useful predictor of mortality in acute respiratory failure.

Intrinsic Dynamic Positive End-Expiratory Pressure in Stable Patients with Chronic Obstructive Pulmonary Disease.

BACKGROUND: Assessment of intrinsic dynamic positive end-expiratory pressure (PEEPi,dyn) may be clinically important in stable patients with chronic obstructive pulmonary disease (COPD), but epidemiological data are scant. OBJECTIVES: The aim of our study was (i) to assess the PEEPi,dyn in a large population of stable patients with COPD and (ii) to evaluate the correlations with some noninvasive measurements routinely assessed. METHOD: Retrospective analysis of lung mechanics, dynamic volumes, arterial blood gases, dyspnoea by means of the Medical Research Council (MRC) scale, the COPD Assessment Test score, and maximal inspiratory/expiratory pressures in 87 hypercapnic and 62 normocapnic patients. RESULTS: The mean PEEPi,dyn was significantly higher in hypercapnic than normocapnic patients (2.8 ± 2.2 vs. 1.9 ± 1.6 cm H2O, respectively, p = 0.0094). PEEPi,dyn did not differ according to Global Initiative for Chronic Obstructive Lung Disease stage, MRC score, or use or not of long-term oxygen therapy. There were significant although weak correlations between PEEPi,dyn and airway obstruction, hyperinflation, respiratory muscle function, arterial CO2 tension, and number of exacerbations/year. The transdiaphragmatic pressure was the strongest variable associated to PEEPi,dyn (R = 0.5713, p = 0.001). CONCLUSION: In stable patients with COPD, PEEPi,dyn is higher in hypercapnic patients and weakly correlated to noninvasive measures of lung and respiratory muscle function.

Exploring a social work lead mindfulness-based intervention to address burnout among inpatient psychiatric nurses: a pilot study.

Acute psychiatric nurses experience workplace stressors related to organizational factors including staffing shortages, along with interpersonal conflict with patients and colleagues. The pilot study examined the experience of burnout among acute care psychiatric nurses and the usefulness of a social work lead mindfulness-based intervention for reducing burnout elements. Findings indicated participants experienced emotional exhaustion associated with their work, but also a significant degree of personal accomplishment. Nurses identified the intervention as having the potential to promote better emotional regulation in the workplace and beyond. Social worker education on mindfulness techniques may represent an untapped resource for improving the emotional wellness and effective patient care.

Continuous monitoring of intrinsic PEEP based on expired CO2 kinetics: an experimental validation study.

BACKGROUND: Quantification of intrinsic PEEP (PEEPi) has important implications for patients subjected to invasive mechanical ventilation. A new non-invasive breath-by-breath method (etCO2D) for determination of PEEPi is evaluated. METHODS: In 12 mechanically ventilated pigs, dynamic hyperinflation was induced by interposing a resistance in the endotracheal tube. Airway pressure, flow, and exhaled CO2 were measured at the airway opening. Combining different I:E ratios, respiratory rates, and tidal volumes, 52 different levels of PEEPi (range 1.8-11.7 cmH2O; mean 8.45 ± 0.32 cmH2O) were studied. The etCO2D is based on the detection of the end-tidal dilution of the capnogram. This is measured at the airway opening by means of a CO2 sensor in which a 2-mm leak is added to the sensing chamber. This allows to detect a capnogram dilution with fresh air when the pressure coming from the ventilator exceeds the PEEPi. This method was compared with the occlusion method. RESULTS: The etCO2D method detected PEEPi step changes of 0.2 cmH2O. Reference and etCO2D PEEPi presented a good correlation (R2 0.80, P < 0.0001) and good agreement, bias - 0.26, and limits of agreement ± 1.96 SD (2.23, - 2.74) (P < 0.0001). CONCLUSIONS: The etCO2D method is a promising accurate simple way of continuously measure and monitor PEEPi. Its clinical validity needs, however, to be confirmed in clinical studies and in conditions with heterogeneous lung diseases.

[Effect of neurally adjusted ventilatory assist on trigger of mechanical ventilation in acute exacerbation of chronic obstructive pulmonary disease patients with intrinsic positive end-expiratory pressure].

Objective: To compare the trigger delay and work of trigger between neurally adjusted ventilatory assist (NAVA) and pressure support ventilation (PSV) in acute exacerbation of chronic obstructive pulmonary disease (AECOPD) patients with intrinsic positive end-expiratory pressure (PEEP) during mechanical ventilation. Methods: AECOPD patients with intrinsic PEEP (PEEPi) greater than or equal to 3 cmH(2)O (1 cmH(2)O=0.098 kPa) were enrolled during invasive mechanical ventilation. Subjects were ventilated with low, medium and high pressure under either NAVA or PSV mode. Servo Tracker software continuously recorded the waveform of ventilator and respiratory mechanics indexes (including respiratory frequency, inspiratory tidal volume (Vti), minute ventilation volume (VE), peak airway pressure (PIP), inspiratory time), and calculated trigger and expiratory conversion delay time, work of trigger and total work of breath. Results: A total of 14 AECOPD patients were enrolled with the average PEEPi (4.3±1.3) cmH(2)O. PSV inspiratory trigger delay time was positively correlated with PEEPi (r=0.913, P<0.05). Compared with PSV, NAVA significantly decreased trigger delay time in low, medium and high pressure level groups [(48±17) ms vs. (167±86) ms, (63±65) ms vs. (247±240) ms, (63±49) ms vs. (342±192) ms,respectively all P<0.05]. Similar results were shown as to work of trigger [(0.92±0.36) µV∙s vs. (1.22±0.70) µV∙s, (1.08±0.51) µV∙s vs. (1.62±1.25) µV∙s, (1.20±0.96) µV∙s vs. (2.29±1.02) µV∙s, all P<0.05]. Trigger delay time increased according to the increase of pressure level in PSV mode. Conclusion: The presence of PEEPi in AECOPD patients leads to obvious trigger delay under PSV mode, which is positively correlated with PEEPi level. NAVA significantly reduces trigger delay time and work of trigger compared with PSV mode.

Transpulmonary Pressure Describes Lung Morphology During Decremental Positive End-Expiratory Pressure Trials in Obesity.

OBJECTIVES: Atelectasis develops in critically ill obese patients when undergoing mechanical ventilation due to increased pleural pressure. The current study aimed to determine the relationship between transpulmonary pressure, lung mechanics, and lung morphology and to quantify the benefits of a decremental positive end-expiratory pressure trial preceded by a recruitment maneuver. DESIGN: Prospective, crossover, nonrandomized interventional study. SETTING: Medical and Surgical Intensive Care Units at Massachusetts General Hospital (Boston, MA) and University Animal Research Laboratory (São Paulo, Brazil). PATIENTS/SUBJECTS: Critically ill obese patients with acute respiratory failure and anesthetized swine. INTERVENTIONS: Clinical data from 16 mechanically ventilated critically ill obese patients were analyzed. An animal model of obesity with reversible atelectasis was developed by placing fluid filled bags on the abdomen to describe changes of lung mechanics, lung morphology, and pulmonary hemodynamics in 10 swine. MEASUREMENTS AND MAIN RESULTS: In obese patients (body mass index, 48 ± 11 kg/m), 21.7 ± 3.7 cm H2O of positive end-expiratory pressure resulted in the lowest elastance of the respiratory system (18.6 ± 6.1 cm H2O/L) after a recruitment maneuver and decremental positive end-expiratory pressure and corresponded to a positive (2.1 ± 2.2 cm H2O) end-expiratory transpulmonary pressure. Ventilation at lowest elastance positive end-expiratory pressure preceded by a recruitment maneuver restored end-expiratory lung volume (30.4 ± 9.1 mL/kg ideal body weight) and oxygenation (273.4 ± 72.1 mm Hg). In the swine model, lung collapse and intratidal recruitment/derecruitment occurred when the positive end-expiratory transpulmonary pressure decreased below 2-4 cm H2O. After the development of atelectasis, a decremental positive end-expiratory pressure trial preceded by lung recruitment identified the positive end-expiratory pressure level (17.4 ± 2.1 cm H2O) needed to restore poorly and nonaerated lung tissue, reestablishing lung elastance and oxygenation while avoiding increased pulmonary vascular resistance. CONCLUSIONS: In obesity, low-to-negative values of transpulmonary pressure predict lung collapse and intratidal recruitment/derecruitment. A decremental positive end-expiratory pressure trial preceded by a recruitment maneuver reverses atelectasis, improves lung mechanics, distribution of ventilation and oxygenation, and does not increase pulmonary vascular resistance.

Typical patterns of expiratory flow and carbon dioxide in mechanically ventilated patients with spontaneous breathing.

Incomplete expiration of tidal volume can lead to dynamic hyperinflation and auto-PEEP. Methods are available for assessing these, but are not appropriate for patients with respiratory muscle activity, as occurs in pressure support. Information may exist in expiratory flow and carbon dioxide measurements, which, when taken together, may help characterize dynamic hyperinflation. This paper postulates such patterns and investigates whether these can be seen systematically in data. Two variables are proposed summarizing the number of incomplete expirations quantified as a lack of return to zero flow in expiration (IncExp), and the end tidal CO2 variability (varETCO2), over 20 breaths. Using these variables, three patterns of ventilation are postulated: (a) few incomplete expirations (IncExp < 2) and small varETCO2; (b) a variable number of incomplete expirations (2 ≤ IncExp ≤ 18) and large varETCO2; and (c) a large number of incomplete expirations (IncExp > 18) and small varETCO2. IncExp and varETCO2 were calculated from data describing respiratory flow and CO2 signals in 11 patients mechanically ventilated at 5 levels of pressure support. Data analysis showed that the three patterns presented systematically in the data, with periods of IncExp < 2 or IncExp > 18 having significantly lower variability in end-tidal CO2 than periods with 2 ≤ IncExp ≤ 18 (p < 0.05). It was also shown that sudden change in IncExp from either IncExp < 2 or IncExp > 18 to 2 ≤ IncExp ≤ 18 results in significant, rapid, change in the variability of end-tidal CO2 p < 0.05. This study illustrates that systematic patterns of expiratory flow and end-tidal CO2 are present in patients in supported mechanical ventilation, and that changes between these patterns can be identified. Further studies are required to see if these patterns characterize dynamic hyperinflation. If so, then their combination may provide a useful addition to understanding the patient at the bedside.

Controlled mechanical ventilation with constant positive end-expiratory pressure and alveolar recruitment manoeuvres during anaesthesia in laterally or dorsally recumbent horses.

OBJECTIVE: To compare the effects of controlled mechanical ventilation (CMV) and constant positive end-expiratory pressure (PEEP) and interposed recruitment manoeuvres (RMs) with those of CMV without PEEP on gas exchange during general anaesthesia and the early recovery period. STUDY DESIGN: Prospective, randomized clinical trial. ANIMALS: A total of 48 Warmblood horses undergoing elective surgery in lateral (Lat) (n = 24) or dorsal (Dors) (n = 24) recumbency. METHODS: Premedication (romifidine), induction (diazepam and ketamine) and maintenance (isoflurane in oxygen) were identical in all horses. Groups Lat- CMV and Dors-CMV (each n = 12) were ventilated using CMV. Groups Lat-RM and Dors-RM (each n = 12) were ventilated using CMV with constant PEEP (10 cmH2O) and intermittent RMs (three consecutive breaths with peak inspiratory pressure of 60 cmH2O, 80 cmH2O and 60 cmH2O, respectively). RMs were applied as required to maintain PaO2 at > 400 mmHg (> 53.3 kPa). Dobutamine was given to maintain mean arterial blood pressure at > 60 mmHg. Physiological parameters were recorded every 10 minutes. Arterial blood gases were measured intra- and postoperatively. Statistical analyses were conducted using analyses of variance (anova),t tests and the Mann-Whitney U-test. RESULTS: Horses in Dors-RM had higher PaO2 values [478 ± 35 mmHg (63.7 ± 4.6 kPa)] than horses in Dors-CMV [324 ± 45 mmHg (43.2 ± 6 kPa)] during anaesthesia and the early recovery period. There were no differences between horses in groups Lat-CMV and Lat-RM. Other measured parameters did not differ between groups. CONCLUSIONS AND CLINICAL RELEVANCE: Ventilation with CMV, constant PEEP and interposed RM provided improved arterial oxygenation in horses in dorsal recumbency that lasted into the early recovery period, but had no benefit in horses in lateral recumbency. This mode of ventilation may provide a clinically practicable method of improving oxygenation in anaesthetized horses, especially in dorsal recumbency.

Age, PaO2/FIO2, and Plateau Pressure Score: A Proposal for a Simple Outcome Score in Patients With the Acute Respiratory Distress Syndrome.

OBJECTIVES: Although there is general agreement on the characteristic features of the acute respiratory distress syndrome, we lack a scoring system that predicts acute respiratory distress syndrome outcome with high probability. Our objective was to develop an outcome score that clinicians could easily calculate at the bedside to predict the risk of death of acute respiratory distress syndrome patients 24 hours after diagnosis. DESIGN: A prospective, multicenter, observational, descriptive, and validation study. SETTING: A network of multidisciplinary ICUs. PATIENTS: Six-hundred patients meeting Berlin criteria for moderate and severe acute respiratory distress syndrome enrolled in two independent cohorts treated with lung-protective ventilation. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Using individual demographic, pulmonary, and systemic data at 24 hours after acute respiratory distress syndrome diagnosis, we derived our prediction score in 300 acute respiratory distress syndrome patients based on stratification of variable values into tertiles, and validated in an independent cohort of 300 acute respiratory distress syndrome patients. Primary outcome was in-hospital mortality. We found that a 9-point score based on patient's age, PaO2/FIO2 ratio, and plateau pressure at 24 hours after acute respiratory distress syndrome diagnosis was associated with death. Patients with a score greater than 7 had a mortality of 83.3% (relative risk, 5.7; 95% CI, 3.0-11.0), whereas patients with scores less than 5 had a mortality of 14.5% (p < 0.0000001). We confirmed the predictive validity of the score in a validation cohort. CONCLUSIONS: A simple 9-point score based on the values of age, PaO2/FIO2 ratio, and plateau pressure calculated at 24 hours on protective ventilation after acute respiratory distress syndrome diagnosis could be used in real time for rating prognosis of acute respiratory distress syndrome patients with high probability.

Role of nasal positive end expiratory pressure valve as an alternative treatment for obstructive sleep apnoea in Chinese patients.

BACKGROUND AND OBJECTIVE: As compliance of continuous positive airway pressure (CPAP) for treatment of obstructive sleep apnoea (OSA) is often suboptimal, a less cumbersome treatment is desirable. We explored the clinical usefulness of nasal positive end expiratory pressure (nPEEP) valves. METHODS: Symptomatic OSA patients (apnoea hypopnea index (AHI) >5/h by polysomnography (PSG) or >10/h by type III devices), who declined CPAP, were recruited. A nPEEP valve was attached to each nostril before bed. After successful acclimatization for 1 week, treatment was continued for 4 weeks. The nPEEP valves provided expiratory resistance to build up PEEP. PSG was performed at week 4. RESULTS: Among 196 subjects, 46 (23%) failed acclimatization and 14 (7%) withdrew. Among the 120 patients with a valid PSG, 72 (60%) and 75 (63%) had >50% reduction in mean (standard deviation) overall AHI 26 (16)/h to 18 (18)/h and mean supine AHI 31 (19)/h to 11(16)/h, respectively, P < 0.001. Compared with responders, patients with <50% reduction in AHI had a higher mean overall AHI (30/h vs 23/h, P = 0.03), higher mean supine AHI (35/h vs 26/h, P = 0.04), more severe mean oxygen desaturation nadir (76.7% vs 82.7%, P < 0.01) and longer mean period of desaturation <90% SaO2 (7.7 vs 2.4, P = 0.02). Breathing discomfort and dry mouth were the most common side effects. Compared with a dental device, there was a larger mean reduction in supine AHI using nPEEP (29 (14)/h vs 16 (17)/h). CONCLUSION: nPEEP valves were useful in selected patients with mild or positional-related OSA.

Recruitment manoeuvres for adults with acute respiratory distress syndrome receiving mechanical ventilation.

BACKGROUND: Recruitment manoeuvres involve transient elevations in airway pressure applied during mechanical ventilation to open ('recruit') collapsed lung units and increase the number of alveoli participating in tidal ventilation. Recruitment manoeuvres are often used to treat patients in intensive care who have acute respiratory distress syndrome (ARDS), but the effect of this treatment on clinical outcomes has not been well established. This systematic review is an update of a Cochrane review originally published in 2009. OBJECTIVES: Our primary objective was to determine the effects of recruitment manoeuvres on mortality in adults with acute respiratory distress syndrome.Our secondary objective was to determine, in the same population, the effects of recruitment manoeuvres on oxygenation and adverse events (e.g. rate of barotrauma). SEARCH METHODS: For this updated review, we searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (OVID), Embase (OVID), the Cumulative Index to Nursing and Allied Health Literature (CINAHL, EBSCO), Latin American and Caribbean Health Sciences (LILACS) and the International Standard Randomized Controlled Trial Number (ISRCTN) registry from inception to August 2016. SELECTION CRITERIA: We included randomized controlled trials (RCTs) of adults who were mechanically ventilated that compared recruitment manoeuvres versus standard care for patients given a diagnosis of ARDS. DATA COLLECTION AND ANALYSIS: Two review authors independently assessed trial quality and extracted data. We contacted study authors for additional information. MAIN RESULTS: Ten trials met the inclusion criteria for this review (n = 1658 participants). We found five trials to be at low risk of bias and five to be at moderate risk of bias. Six of the trials included recruitment manoeuvres as part of an open lung ventilation strategy that was different from control ventilation in aspects other than the recruitment manoeuvre (such as mode of ventilation, higher positive end-expiratory pressure (PEEP) titration and lower tidal volume or plateau pressure). Six studies reported mortality outcomes. Pooled data from five trials (1370 participants) showed a reduction in intensive care unit (ICU) mortality (risk ratio (RR) 0.83, 95% confidence interval (CI) 0.72 to 0.97, P = 0.02, low-quality evidence), pooled data from five trials (1450 participants) showed no difference in 28-day mortality (RR 0.86, 95% CI 0.74 to 1.01, P = 0.06, low-quality evidence) and pooled data from four trials (1313 participants) showed no difference in in-hospital mortality (RR 0.88, 95% CI 0.77 to 1.01, P = 0.07, low-quality evidence). Data revealed no differences in risk of barotrauma (RR 1.09, 95% CI 0.78 to 1.53, P = 0.60, seven studies, 1508 participants, moderate-quality evidence). AUTHORS' CONCLUSIONS: We identified significant clinical heterogeneity in the 10 included trials. Results are based upon the findings of several (five) trials that included an "open lung ventilation strategy", whereby the intervention group differed from the control group in aspects other than the recruitment manoeuvre (including co-interventions such as higher PEEP, different modes of ventilation and higher plateau pressure), making interpretation of the results difficult. A ventilation strategy that included recruitment manoeuvres in participants with ARDS reduced intensive care unit mortality without increasing the risk of barotrauma but had no effect on 28-day and hospital mortality. We downgraded the quality of the evidence to low, as most of the included trials provided co-interventions as part of an open lung ventilation strategy, and this might have influenced results of the outcome.

Dynamic laryngeal narrowing during exercise: a mechanism for generating intrinsic PEEP in COPD?

INTRODUCTION: Patients with COPD commonly exhibit pursed-lip breathing during exercise, a strategy that, by increasing intrinsic positive end-expiratory pressure, may optimise lung mechanics and exercise tolerance. A similar role for laryngeal narrowing in modulating exercise airways resistance and the respiratory cycle volume-time course is postulated, yet remains unstudied in COPD. The aim of this study was to assess the characteristics of laryngeal narrowing and its role in exercise intolerance and dynamic hyperinflation in COPD. METHODS: We studied 19 patients (n=8 mild-moderate; n=11 severe COPD) and healthy age and sex matched controls (n=11). Baseline physiological characteristics and clinical status were assessed prior to an incremental maximal cardiopulmonary exercise test with continuous laryngoscopy. Laryngeal narrowing measures were calculated at the glottic and supra-glottic aperture at rest and peak exercise. RESULTS: At rest, expiratory laryngeal narrowing was pronounced at the glottic level in patients and related to FEV1 in the whole cohort (r=-0.71, p<0.001) and patients alone (r=-0.53, p=0.018). During exercise, glottic narrowing was inversely related to peak ventilation in all subjects (r=-0.55, p=0.0015) and patients (r=-0.71, p<0.001) and peak exercise tidal volume (r=-0.58, p=0.0062 and r=-0.55, p=0.0076, respectively). Exercise glottic narrowing was also inversely related to peak oxygen uptake (% predicted) in all subjects (r=-0.65, p<0.001) and patients considered alone (r=-0.58, p=0.014). Exercise inspiratory duty cycle was related to exercise glottic narrowing for all subjects (r=-0.69, p<0.001) and patients (r=-0.62, p<0.001). CONCLUSIONS: Dynamic laryngeal narrowing during expiration is prevalent in patients with COPD and is related to disease severity, respiratory duty cycle and exercise capacity.

Selecting the 'right' positive end-expiratory pressure level.

PURPOSE OF REVIEW: To compare the positive end-expiratory pressure selection aiming either to oxygenation or to the full lung opening. RECENT FINDINGS: Increasing positive end-expiratory pressure in patients with severe hypoxemia is associated with better outcome if the oxygenation response is greater and positive end-expiratory pressure tests may be performed in a few minutes. The oxygenation response to recruitment maneuvers was associated with better outcome in patients with acute respiratory distress syndrome from influenza A (H1N1). If, after recruitment maneuver, the recruitment is not sustained by sufficient positive end-expiratory pressure, the lung will unavoidably collapse. Several papers investigated the positive end-expiratory pressure selection according to the deflation limb of the pressure-volume curve. It is still questionable whether to consider oxygenation or respiratory mechanics change as the best marker for adequate selection. A growing interest is paid to the estimate of transpulmonary pressure, although no consensus is available on which methodology is preferable. Finally, the positive end-expiratory pressure adequate for full lung opening may be computed combining the computed tomography scan variables and the chest wall elastance. SUMMARY: When compared, most of the methods give the same positive end-expiratory pressure values in patients with higher and lower recruitability. The positive end-expiratory pressure/inspiratory oxygen fraction tables are the only methods providing lower positive end-expiratory pressure in lower recruiters and higher positive end-expiratory pressure in higher recruiters.

Hemodynamic consequences of auto-PEEP.

Auto-positive end-expiratory pressure (PEEP) is a common but frequently unrecognized problem in critically ill patients. It has important physiologic consequences and can cause shock and cardiac arrest. Treatment consists of relieving expiratory airflow obstruction and reducing minute ventilation delivered by positive pressure ventilation. Sedation and fluid management are important adjunctive therapies. This analytic review discusses the prevalence, pathophysiology, and hemodynamic consequences of auto-PEEP and an approach to its treatment.

Ventilation strategies in obese patients undergoing surgery: a quantitative systematic review and meta-analysis.

BACKGROUND: Pathophysiological changes due to obesity may complicate mechanical ventilation during general anaesthesia. The ideal ventilation strategy is expected to optimize gas exchange and pulmonary mechanics and to reduce the risk of respiratory complications. METHODS: Systematic search (databases, bibliographies, to March 2012, all languages) was performed for randomized trials testing intraoperative ventilation strategies in obese patients (BMI ≥ 30 kg m(-2)), and reporting on gas exchange, pulmonary mechanics, or pulmonary complications. Meta-analyses were performed when data from at least three studies or 100 patients could be combined. RESULTS: Thirteen studies (505 obese surgical patients) reported on a variety of ventilation strategies: pressure- or volume-controlled ventilation (PCV, VCV), various tidal volumes, and different PEEP or recruitment manoeuvres (RM), and combinations thereof. Definitions and reporting of endpoints were inconsistent. In five trials (182 patients), RM added to PEEP compared with PEEP alone improved intraoperative PaO2/FIO2 ratio [weighted mean difference (WMD), 16.2 kPa; 95% confidence interval (CI), 8.0-24.4] and increased respiratory system compliance (WMD, 14 ml cm H(2)O(-1); 95% CI, 8-20). Arterial pressure remained unchanged. In four trials (100 patients) comparing PCV with VCV, there was no difference in PaO2/FIO2 ratio, tidal volume, or arterial pressure. Comparison of further ventilation strategies or combination of other outcomes was not feasible. Data on postoperative complications were seldom reported. CONCLUSIONS: The ideal intraoperative ventilation strategy in obese patients remains obscure. There is some evidence that RM added to PEEP compared with PEEP alone improves intraoperative oxygenation and compliance without adverse effects. There is no evidence of any difference between PCV and VCV.

Dynamic hyperinflation and auto-positive end-expiratory pressure: lessons learned over 30 years.

Auto-positive end-expiratory pressure (auto-PEEP; AP) and dynamic hyperinflation (DH) may affect hemodynamics, predispose to barotrauma, increase work of breathing, cause dyspnea, disrupt patient-ventilator synchrony, confuse monitoring of hemodynamics and respiratory system mechanics, and interfere with the effectiveness of pressure-regulated ventilation. Although basic knowledge regarding the clinical physiology and management of AP during mechanical ventilation has evolved impressively over the 30 years since DH and AP were first brought to clinical attention, novel and clinically relevant characteristics of this complex phenomenon continue to be described. This discussion reviews some of the more important aspects of AP that bear on the care of the ventilated patient with critical illness.

[Acute oxygen desaturation following peritonectomy and hyperthermic intraperitoneal chemotherapy]. / Akuter Sättigungsabfall nach Peritonektomie und hyperthermer intraperitonealer Chemotherapie.

Intraoperative hyperthermic intraperitoneal chemotherapy (HIPEC) may have a significant impact on physiological functions and is therefore a special challenge for anesthetists. In the presented case after opening the parietal pleura during subphrenical peritonectomy the HIPEC solution accidentally leaked into the right hemithorax with subsequent pleural effusion of more than 2,000 ml. After extubation the patient presented with acute oxygen desaturation and orthopnea. Following pleural sonography and chest X-ray in the operating theatre and recovery area, a thorax drainage was inserted into the pleural space and ventilation support was provided by non-invasive continuous positive air pressure (CPAP) ventilation. With reference to recent publications the anesthesiological management of patients undergoing HIPEC is presented.