The ventilator of the future: key principles and unmet needs.

Persistent shortcomings of invasive positive pressure ventilation make it less than an ideal intervention. Over the course of more than seven decades, clinical experience and scientific investigation have helped define its range of hazards and limitations. Apart from compromised airway clearance and lower airway contamination imposed by endotracheal intubation, the primary hazards inherent to positive pressure ventilation may be considered in three broad categories: hemodynamic impairment, potential for ventilation-induced lung injury, and impairment of the respiratory muscle pump. To optimize care delivery, it is crucial for monitoring and machine outputs to integrate information with the potential to impact the underlying requirements of the patient and/or responses of the cardiopulmonary system to ventilatory interventions. Trending analysis, timely interventions, and closer communication with the caregiver would limit adverse clinical trajectories. Judging from the rapid progress of recent years, we are encouraged to think that insights from physiologic research and emerging technological capability may eventually address important aspects of current deficiencies.

Perioperative Pulmonary Atelectasis: Part II. Clinical Implications.

The development of pulmonary atelectasis is common in the surgical patient. Pulmonary atelectasis can cause various degrees of gas exchange and respiratory mechanics impairment during and after surgery. In its most serious presentations, lung collapse could contribute to postoperative respiratory insufficiency, pneumonia, and worse overall clinical outcomes. A specific risk assessment is critical to allow clinicians to optimally choose the anesthetic technique, prepare appropriate monitoring, adapt the perioperative plan, and ensure the patient's safety. Bedside diagnosis and management have benefited from recent imaging advancements such as lung ultrasound and electrical impedance tomography, and monitoring such as esophageal manometry. Therapeutic management includes a broad range of interventions aimed at promoting lung recruitment. During general anesthesia, these strategies have consistently demonstrated their effectiveness in improving intraoperative oxygenation and respiratory compliance. Yet these same intraoperative strategies may fail to affect additional postoperative pulmonary outcomes. Specific attention to the postoperative period may be key for such outcome impact of lung expansion. Interventions such as noninvasive positive pressure ventilatory support may be beneficial in specific patients at high risk for pulmonary atelectasis (e.g., obese) or those with clinical presentations consistent with lung collapse (e.g., postoperative hypoxemia after abdominal and cardiothoracic surgeries). Preoperative interventions may open new opportunities to minimize perioperative lung collapse and prevent pulmonary complications. Knowledge of pathophysiologic mechanisms of atelectasis and their consequences in the healthy and diseased lung should provide the basis for current practice and help to stratify and match the intensity of selected interventions to clinical conditions.

Association between hospital mortality and inspiratory airway pressures in mechanically ventilated patients without acute respiratory distress syndrome: a prospective cohort study.

BACKGROUND: Higher inspiratory airway pressures are associated with worse outcomes in mechanically ventilated patients with the acute respiratory distress syndrome (ARDS). This relationship, however, has not been well investigated in patients without ARDS. We hypothesized that higher driving pressures (ΔP) and plateau pressures (Pplat) are associated with worse patient-centered outcomes in mechanically ventilated patients without ARDS as well as those with ARDS. METHODS: Using data collected during a prospective, observational cohort study of 6179 critically ill participants enrolled in 59 ICUs across the USA, we used multivariable logistic regression to determine whether ΔP and Pplat at enrollment were associated with hospital mortality among 1132 mechanically ventilated participants. We stratified analyses by ARDS status. RESULTS: Participants without ARDS (n = 822) had lower average severity of illness scores and lower hospital mortality (27.3% vs. 38.7%; p <  0.001) than those with ARDS (n = 310). Average Pplat (20.6 vs. 23.9 cm H2O; p <  0.001), ΔP (14.3 vs. 16.0 cm H2O; p <  0.001), and positive end-expiratory pressure (6.3 vs. 7.9 cm H2O; p <  0.001) were lower in participants without ARDS, whereas average tidal volumes (7.2 vs. 6.8 mL/kg PBW; p <  0.001) were higher. Among those without ARDS, higher ΔP (adjusted OR = 1.36 per 7 cm H2O, 95% CI 1.14-1.62) and Pplat (adjusted OR = 1.42 per 8 cm H2O, 95% CI 1.17-1.73) were associated with higher mortality. We found similar relationships with mortality among those participants with ARDS. CONCLUSIONS: Higher ΔP and Pplat are associated with increased mortality for participants without ARDS. ΔP may be a viable target for lung-protective ventilation in all mechanically ventilated patients.

Positive End-expiratory Pressure Alone Minimizes Atelectasis Formation in Nonabdominal Surgery: A Randomized Controlled Trial.

BACKGROUND: Various methods for protective ventilation are increasingly being recommended for patients undergoing general anesthesia. However, the importance of each individual component is still unclear. In particular, the perioperative use of positive end-expiratory pressure (PEEP) remains controversial. The authors tested the hypothesis that PEEP alone would be sufficient to limit atelectasis formation during nonabdominal surgery. METHODS: This was a randomized controlled evaluator-blinded study. Twenty-four healthy patients undergoing general anesthesia were randomized to receive either mechanical ventilation with PEEP 7 or 9 cm H2O depending on body mass index (n = 12) or zero PEEP (n = 12). No recruitment maneuvers were used. The primary outcome was atelectasis area as studied by computed tomography in a transverse scan near the diaphragm, at the end of surgery, before emergence. Oxygenation was evaluated by measuring blood gases and calculating the ratio of arterial oxygen partial pressure to inspired oxygen fraction (PaO2/FIO2 ratio). RESULTS: At the end of surgery, the median (range) atelectasis area, expressed as percentage of the total lung area, was 1.8 (0.3 to 9.9) in the PEEP group and 4.6 (1.0 to 10.2) in the zero PEEP group. The difference in medians was 2.8% (95% CI, 1.7 to 5.7%; P = 0.002). Oxygenation and carbon dioxide elimination were maintained in the PEEP group, but both deteriorated in the zero PEEP group. CONCLUSIONS: During nonabdominal surgery, adequate PEEP is sufficient to minimize atelectasis in healthy lungs and thereby maintain oxygenation. Thus, routine recruitment maneuvers seem unnecessary, and the authors suggest that they should only be utilized when clearly indicated. VISUAL ABSTRACT: An online visual overview is available for this article at http://links.lww.com/ALN/B728.

Variable Ventilation Associated With Recruitment Maneuver Minimizes Tissue Damage and Pulmonary Inflammation in Anesthetized Lung-Healthy Rats.

BACKGROUND: Recruitment maneuver and positive end-expiratory pressure (PEEP) can be used to counteract intraoperative anesthesia-induced atelectasis. Variable ventilation can stabilize lung mechanics by avoiding the monotonic tidal volume and protect lung parenchyma as tidal recruitment is encompassed within the tidal volume variability. METHODS: Forty-nine (7 per group) male Wistar rats were anesthetized, paralyzed, and mechanically ventilated. A recruitment maneuver followed by stepwise decremental PEEP titration was performed while continuously estimating respiratory system mechanics using recursive least squares. After a new recruitment, animals were ventilated for 2 hours in volume-control with monotonic (VCV) or variable (VV) tidal volumes. PEEP was adjusted at a level corresponding to the minimum elastance or 2 cm H2O above or below this level. Lungs were harvested for histologic analysis (left lung) and cytokines measurement (right lung). Seven animals were euthanized before the first recruitment as controls. RESULTS: A time-dependent increase in respiratory system elastance was observed and significantly minimized by PEEP (P < .001). Variable ventilation attenuated the amount of concentrations of proinflammatory mediators in lung homogenate: neutrophil cytokine-induced neutrophil chemoattractant 1 (VV = 40 ± 5 and VCV = 57 ± 8 pg/mg; P < .0001) and interleukin-1ß (VV = 59 ± 25 and VCV = 261 ± 113 pg/mg; P < .0001). Variable ventilation was also associated with lower structural lung parenchyma damage. Significant reductions in air fraction at dorsal and caudal lung regions were observed in all ventilated animals (P < .001). CONCLUSIONS: Variable ventilation was more protective than conventional ventilation within the applied PEEP levels.

Variability in the Use of Protective Mechanical Ventilation During General Anesthesia.

BACKGROUND: The purpose of this study was to determine whether significant variation exists in the use of protective ventilation across individual anesthesia providers and whether this difference can be explained by patient, procedure, and provider-related characteristics. METHODS: The cohort consisted of 262 anesthesia providers treating 57,372 patients at a tertiary care hospital between 2007 and 2014. Protective ventilation was defined as a median positive end-expiratory pressure of 5 cm H2O or more, tidal volume of <10 mL/kg of predicted body weight and plateau pressure of <30 cm H2O. Analysis was performed using mixed-effects logistic regression models with propensity scores to adjust for covariates. The definition of protective ventilation was modified in sensitivity analyses. RESULTS: In unadjusted analysis, the mean probability of administering protective ventilation was 53.8% (2.5th percentile of provider 19.9%, 97.5th percentile 80.8%). After adjustment for a large number of covariates, there was little change in the results with a mean probability of 51.1% (2.5th percentile 24.7%, 97.5th percentile 77.2%). The variations persisted when the thresholds for protective ventilation were changed. CONCLUSIONS: There was significant variability across individual anesthesia providers in the use of intraoperative protective mechanical ventilation. Our data suggest that this variability is highly driven by individual preference, rather than patient, procedure, or provider-related characteristics.

Higher PEEP improves outcomes in ARDS patients with clinically objective positive oxygenation response to PEEP: a systematic review and meta-analysis.

BACKGROUND: Mortality in patients with acute respiratory distress syndrome (ARDS) remains high. These patients require mechanical ventilation strategies that include high positive end-expiratory pressure (PEEP). It remains controversial whether high PEEP can improve outcomes for ARDS patients, especially patients who show improvement in oxygenation in response to PEEP. In this meta-analysis, we aimed to evaluate the effects of high PEEP on ARDS patients. METHODS: We electronically searched randomized controlled trials (RCTs) reported in the MEDLINE, CENTRAL, EMBASE, CINAHL and Web of Science databases from January 1990 to December 2017. Meta-analyses of the effects of PEEP on survival in adults with ARDS were conducted using the methods recommended by the Cochrane Collaboration. RESULTS: A total of 3612 patients from nine randomized controlled trials (RCTs) were included. There were 1794 and 1818 patients in the high and low PEEP groups, respectively. Hospital mortality showed no significant difference between the high and low PEEP groups (RR = 0.92; 95% CI, 0.79 to 1.07; P = 0.26). Similar results were found for 28-d mortality (RR = 0.88; 95% CI, 0.72 to 1.07; P = 0.19) and ICU mortality (RR = 0.83; 95% CI, 0.65 to 1.07; P = 0.15). The risk of clinically objectified barotrauma was not significantly different between the high and low PEEP groups (RR = 1.24; 95% CI, 0.74 to 2.09, P = 0.41). In the subgroup of ARDS patients who responded to increased PEEP by improved oxygenation (from 6 RCTs), high PEEP significantly reduced hospital mortality (RR = 0.83; 95% CI 0.69 to 0.98; P = 0.03), ICU mortality (RR = 0.74; 95% CI, 0.56 to 0.98; P = 0.04),but the 28-d mortality was not decreased(RR = 0.83; 95% CI, 0.67 to 1.01; P = 0.07). For ARDS patients in the low PEEP group who received a PEEP level lower than 10 cmH2O (from 6 RCTs), ICU mortality was lower in the high PEEP group than the low PEEP group (RR = 0.65; 95% CI, 0.45 to 0.94; P = 0.02). CONCLUSIONS: For ARDS patients who responded to increased PEEP by improved oxygenation, high PEEP could reduce hospital mortality, ICU mortality and 28-d mortality. High PEEP does not increase the risk of clinically objectified barotrauma.

The Effects of an Open-Lung Approach During One-Lung Ventilation on Postoperative Pulmonary Complications and Driving Pressure: A Descriptive, Multicenter National Study.

OBJECTIVE: Thoracic surgical procedures are associated with an increased risk of postoperative pulmonary complications (PPCs), which seem to be related directly to intraoperative driving pressure. The authors conducted this study to describe the incidence of PPCs in patients in whom an individualized open-lung approach was applied during one-lung ventilation. DESIGN: This was a prospective, multicenter, national descriptive study. SETTING: Thoracic surgery patients undergoing one-lung ventilation. PARTICIPANTS: Eligible participants were included consecutively from October 1, 2016, to September 30, 2017. A total of 690 patients were included. INTERVENTIONS: An individualized open-lung approach that consisted of an alveolar recruitment maneuver followed by a positive end-expiratory pressure adjusted to best respiratory system compliance was performed in all patients. MEASUREMENTS AND MAIN RESULTS: Preoperative and intraoperative data were recorded; the primary outcome was a description of the incidence of PPCs in these patients during the first 7 postoperative days. The patients were mainly male, and half of them had a high risk of PPCs (ARISCAT score exceeding 44). Eleven percent of participants developed a PPC within the first postoperative week. The mean open lung positive end-expiratory pressure was 8 ± 3 cmH2O. When compared with pre-open lung approach values, the open-lung approach significantly decreased the driving pressure (14 ± 4 cmH2O v 11 ± 3 cmH2O; p < 0.001) and increased dynamic compliance (30 ± 10 mL/cmH2O v 43 ±15 mL/cmH2O; p < 0.001). CONCLUSIONS: The low incidence of PPCs in patients who underwent an open-lung approach during one-lung ventilation compared with that reported for other thoracic surgery series and the decrease in the driving pressure in these patients justify an additional randomized controlled trial to compare the open-lung approach with the standard protective strategy of low tidal volume and low positive end-expiratory pressure.

Improved lung recruitment and oxygenation during mandatory ventilation with a new expiratory ventilation assistance device: A controlled interventional trial in healthy pigs.

BACKGROUND: In contrast to conventional mandatory ventilation, a new ventilation mode, expiratory ventilation assistance (EVA), linearises the expiratory tracheal pressure decline. OBJECTIVE: We hypothesised that due to a recruiting effect, linearised expiration oxygenates better than volume controlled ventilation (VCV). We compared the EVA with VCV mode with regard to gas exchange, ventilation volumes and pressures and lung aeration in a model of peri-operative mandatory ventilation in healthy pigs. DESIGN: Controlled interventional trial. SETTING: Animal operating facility at a university medical centre. ANIMALS: A total of 16 German Landrace hybrid pigs. INTERVENTION: The lungs of anaesthetised pigs were ventilated with the EVA mode (n=9) or VCV (control, n=7) for 5 h with positive end-expiratory pressure of 5 cmH2O and tidal volume of 8 ml kg. The respiratory rate was adjusted for a target end-tidal CO2 of 4.7 to 6 kPa. MAIN OUTCOME MEASURES: Tracheal pressure, minute volume and arterial blood gases were recorded repeatedly. Computed thoracic tomography was performed to quantify the percentages of normally and poorly aerated lung tissue. RESULTS: Two animals in the EVA group were excluded due to unstable ventilation (n=1) or unstable FiO2 delivery (n=1). Mean tracheal pressure and PaO2 were higher in the EVA group compared with control (mean tracheal pressure: 11.6 ±â€Š0.4 versus 9.0 ±â€Š0.3 cmH2O, P < 0.001 and PaO2: 19.2 ±â€Š0.7 versus 17.5 ±â€Š0.4 kPa, P = 0.002) with comparable peak inspiratory tracheal pressure (18.3 ±â€Š0.9 versus 18.0 ±â€Š1.2 cmH2O, P > 0.99). Minute volume was lower in the EVA group compared with control (5.5 ±â€Š0.2 versus 7.0 ±â€Š1.0 l min, P = 0.02) with normoventilation in both groups (PaCO2 5.4 ±â€Š0.3 versus 5.5 ±â€Š0.3 kPa, P > 0.99). In the EVA group, the percentage of normally aerated lung tissue was higher (81.0 ±â€Š3.6 versus 75.8 ±â€Š3.0%, P = 0.017) and of poorly aerated lung tissue lower (9.5 ±â€Š3.3 versus 15.7 ±â€Š3.5%, P = 0.002) compared with control. CONCLUSION: EVA ventilation improves lung aeration via elevated mean tracheal pressure and consequently improves arterial oxygenation at unaltered positive end-expiratory pressure (PEEP) and peak inspiratory pressure (PIP). These findings suggest the EVA mode is a new approach for protective lung ventilation.

Association between pre-operative biological phenotypes and postoperative pulmonary complications: An unbiased cluster analysis.

BACKGROUND: Biological phenotypes have been identified within several heterogeneous pulmonary diseases, with potential therapeutic consequences. OBJECTIVE: To assess whether distinct biological phenotypes exist within surgical patients, and whether development of postoperative pulmonary complications (PPCs) and subsequent dependence of intra-operative positive end-expiratory pressure (PEEP) differ between such phenotypes. SETTING: Operating rooms of six hospitals in Europe and USA. DESIGN: Secondary analysis of the 'PROtective Ventilation with HIgh or LOw PEEP' trial. PATIENTS: Adult patients scheduled for abdominal surgery who are at risk of PPCs. INTERVENTIONS: Measurement of pre-operative concentrations of seven plasma biomarkers associated with inflammation and lung injury. MAIN OUTCOME MEASURES: We applied unbiased cluster analysis to identify biological phenotypes. We then compared the proportion of patients developing PPCs within each phenotype, and associations between intra-operative PEEP levels and development of PPCs among phenotypes. RESULTS: In total, 242 patients were included. Unbiased cluster analysis clustered the patients within two biological phenotypes. Patients with phenotype 1 had lower plasma concentrations of TNF-α (3.8 [2.4 to 5.9] vs. 10.2 [8.0 to 12.1] pg ml; P < 0.001), IL-6 (2.3 [1.5 to 4.0] vs. 4.0 [2.9 to 6.5] pg ml; P < 0.001) and IL-8 (4.7 [3.1 to 8.1] vs. 8.1 [6.0 to 13.9] pg ml; P < 0.001). Phenotype 2 patients had the highest incidence of PPC (69.8 vs. 34.2% in type 1; P < 0.001). There was no interaction between phenotype and PEEP level for the development of PPCs (43.2% in high PEEP vs. 25.6% in low PEEP in phenotype 1, and 73.6% in high PEEP and 65.7% in low PEEP in phenotype 2; P for interaction = 0.503). CONCLUSION: Patients at risk of PPCs and undergoing open abdominal surgery can be clustered based on pre-operative plasma biomarker concentrations. The two identified phenotypes have different incidences of PPCs. Biologic phenotyping could be useful in future randomised controlled trials of intra-operative ventilation. TRIAL REGISTRATION: The PROtective Ventilation with HIgh or LOw PEEP trial, including the substudy from which data were used for the present analysis, was registered at ClinicalTrials.gov (NCT01441791).

Effects of pressure support ventilation on ventilator-induced lung injury in mild acute respiratory distress syndrome depend on level of positive end-expiratory pressure: A randomised animal study.

BACKGROUND: Harmful effects of spontaneous breathing have been shown in experimental severe acute respiratory distress syndrome (ARDS). However, in the clinical setting, spontaneous respiration has been indicated only in mild ARDS. To date, no study has compared the effects of spontaneous assisted breathing with those of fully controlled mechanical ventilation at different levels of positive end-expiratory pressure (PEEP) on lung injury in ARDS. OBJECTIVE: To compare the effects of assisted pressure support ventilation (PSV) with pressure-controlled ventilation (PCV) on lung function, histology and biological markers at two different PEEP levels in mild ARDS in rats. DESIGN: Randomised controlled experimental study. SETTING: Basic science laboratory. PARTICIPANTS: Thirty-five Wistar rats (weight ±â€ŠSD, 310 ±â€Š19) g received Escherichia coli lipopolysaccharide (LPS) intratracheally. After 24 h, the animals were anaesthetised and randomly allocated to either PCV (n=14) or PSV (n=14) groups. Each group was further assigned to PEEP = 2 cmH2O or PEEP = 5 cmH2O. Tidal volume was kept constant (≈6 ml kg). Additional nonventilated animals (n=7) were used as a control for postmortem analysis. MAIN OUTCOME MEASURES: Ventilatory and mechanical parameters, arterial blood gases, diffuse alveolar damage score, epithelial integrity measured by E-cadherin tissue expression, and biological markers associated with inflammation (IL-6 and cytokine-induced neutrophil chemoattractant, CINC-1) and type II epithelial cell damage (surfactant protein-B) were evaluated. RESULTS: In both PCV and PSV, peak transpulmonary pressure was lower, whereas E-cadherin tissue expression, which is related to epithelial integrity, was higher at PEEP = 5 cmH2O than at PEEP = 2 cmH2O. In PSV, PEEP = 5 cmH2O compared with PEEP = 2 cmH2O was associated with significantly reduced diffuse alveolar damage score [median (interquartile range), 11 (8.5 to 13.5) vs. 23 (19 to 26), P = 0.005] and expressions of IL-6 and CINC-1 (P = 0.02 for both), whereas surfactant protein-B mRNA expression increased (P = 0.03). These changes suggested less type II epithelial cell damage at a PEEP of 5 cmH2O. Peak transpulmonary pressure correlated positively with IL-6 [Spearman's rho (ρ) = 0.62, P = 0.0007] and CINC-1 expressions (ρ = 0.50, P = 0.01) and negatively with E-cadherin expression (ρ = -0.67, P = 0.0002). CONCLUSION: During PSV, PEEP of 5 cmH2O, but not a PEEP of 2 cmH2O, reduced lung damage and inflammatory markers while maintaining epithelial cell integrity.

Effect of pressure-controlled inverse ratio ventilation on dead space during robot-assisted laparoscopic radical prostatectomy: A randomised crossover study of three different ventilator modes.

BACKGROUND: Pressure-controlled inverse inspiratory to expiratory ratio ventilation (PC-IRV) is thought to be beneficial for reducing the dead space volume. OBJECTIVE: To investigate the effects of PC-IRV on the components of dead space during robot-assisted laparoscopic radical prostatectomy (RLRP). DESIGN: A randomised crossover study of three different ventilator modes. SETTING: A single university hospital from September 2014 to April 2015. PATIENTS: Twenty consecutive study participants undergoing RLRP. INTERVENTIONS: Patients were ventilated sequentially with three different modes in random order for 30 min: volume control ventilation (VCV; inspiratory to expiratory ratio 0.5), pressure control ventilation (PCV; inspiratory to expiratory ratio 0.5) and PC-IRV. Inverse inspiratory to expiratory ratio was adjusted individually by observing the expiratory flow-time wave to prevent the risk of dynamic pulmonary hyperinflation. MAIN OUTCOME MEASURES: The primary outcome included physiological dead space (VDphys), airway dead space (VDaw), alveolar dead space (VDalv) and shunt dead space (VDshunt). VDphys was calculated by Enghoff's method. We also analysed respiratory dead space (VDresp) and VDaw using a novel analytical method. Then, VDalv and VDshunt were calculated by VDalv = VDresp - VDaw and VDshunt = VDphys - VDresp, respectively. RESULTS: The VDphys/expired tidal volume (VTE) ratio in PC-IRV (29.2 ±â€Š4.7%) was significantly reduced compared with that in VCV (43 ±â€Š8.5%) and in PCV (35.9 ±â€Š3.9%). The VDshunt/VTE in PC-IRV was significantly smaller than that in VCV and PCV. VDaw/VTE in PC-IRV was also significantly smaller than that in VCV but not that in PCV. There was no significant change in VDalv/VTE. CONCLUSION: PC-IRV with the inspiratory to expiratory ratio individually adjusted by the expiratory flow-time wave decreased VDphys/VTE in patients undergoing RLRP. TRIAL REGISTRATION: University Hospital Medical Information Network in Japan 000014004.

Preoperative Treatment of Obstructive Sleep Apnea With Positive Airway Pressure is Associated With Decreased Incidence of Atrial Fibrillation After Cardiac Surgery.

OBJECTIVE: Based on clinical studies in the nonsurgical population that positive airway pressure (PAP) therapy for patients with obstructive sleep apnea (OSA) provides benefits for those with atrial fibrillation, the authors tested the hypothesis that PAP in patients with OSA reduces the incidence of postoperative atrial fibrillation (POAF) after cardiac surgery. DESIGN: Retrospective analysis. SETTING: Single-center university hospital. PARTICIPANTS: The study comprised 192 patients in sinus rhythm preoperatively who were undergoing nontransplantation or ventricular assist device implantation cardiac surgery requiring cardiopulmonary bypass but not requiring systemic circulatory arrest, with documented PAP adherence from January 2008 to October 2015. INTERVENTIONS: Retrospective review of medical records. MEASUREMENTS AND MAIN RESULTS: POAF was defined as atrial fibrillation requiring therapeutic intervention. Of the 192 patients with OSA, 104 (54%) were documented to be PAP-adherent and 88 (46%) were reported to be PAP-nonadherent. Among PAP users, 49 (47%) developed POAF; among PAP nonusers, 59 (66%) developed POAF. The adjusted hazard ratio was 0.59 (95% confidence interval 0.40-0.86, p<0.01). No differences were observed in intensive care unit length of stay (4.0±3.4 days for PAP-adherent group v 5.0±6.2 days for PAP-nonadherent group; p = 0.22) or hospital length of stay (10.7±6.6 days for PAP-adherent group v 10.9±7.3 days for PAP nonadherent group; p = 0.56). A lower median postoperative creatinine rise was observed in PAP-adherent patients (18.2% [8.3%-37.5%) v 31.3% [13.3%-50%]; p< 0.01). CONCLUSION: Preoperative PAP use in patients with OSA was associated with a decreased rate of POAF after cardiac surgery.

Kinetics of plasma biomarkers of inflammation and lung injury in surgical patients with or without postoperative pulmonary complications.

BACKGROUND: Postoperative pulmonary complications (PPCs) are common after major abdominal surgery. The kinetics of plasma biomarkers could improve identification of patients developing PPCs, but the kinetics may depend on intraoperative ventilator settings. OBJECTIVE: To test whether the kinetics of plasma biomarkers are capable of identifying patients who will develop PPCs, and whether the kinetics depend on the intraoperative level of positive end-expiratory pressure (PEEP). DESIGN: A preplanned substudy of a randomised controlled trial. SETTING: Operation room of five centres. PATIENTS: Two hundred and forty-two adult patients scheduled for abdominal surgery at risk of developing PPCs. INTERVENTIONS: High (12 cmH2O) versus low (≤2 cmH2O) levels of PEEP. MAIN OUTCOME MEASURES: Individual PPCs were combined as a composite endpoint. Plasma samples were collected before surgery, directly after surgery and on the fifth postoperative day. The levels of the following were measured: tumour necrosis factor (TNF)-α, interleukin (IL)-6 and IL-8, the soluble form of the Receptor for Advanced Glycation End-products (sRAGE), Surfactant Protein (SP)-D, Clara Cell protein (CC)-16 and Krebs von den Lungen 6 (KL6). RESULTS: Blood sampling was complete in 242 patients: 120 patients in the high PEEP group and 122 patients in the low PEEP group. Increases in plasma levels of TNF- IL-6, IL-8 and CC-16, and a decrease in plasma levels of SP-D were greater in patients who developed PPCs; however, the area under the receiver operating characteristic curve was low for all biomarkers. CC-16 was the only biomarker whose level increased more in patients who had received high levels of PEEP. CONCLUSION: In patients undergoing abdominal surgery and at risk of developing PPCs, plasma levels of biomarkers for inflammation or lung injury showed distinct kinetics with development of PPCs, but none of the biomarkers showed sufficient prognostic value. The use of high levels of PEEP was associated with increased levels of CC-16, suggesting lung overdistension. TRIAL REGISTRATION: The PROVHILO trial, including this substudy, was registered at clinicaltrials.gov (NCT01441791).

Lung recruitment improves right ventricular performance after cardiopulmonary bypass: A randomised controlled trial.

BACKGROUND: Atelectasis after cardiopulmonary bypass (CPB) can affect right ventricular (RV) performance by increasing its outflow impedance. OBJECTIVE: The aim of this study was to determine whether a lung recruitment manoeuvre improves RV function by re-aerating the lung after CPB. DESIGN: Randomised controlled study. SETTING: Single-institution study, community hospital, Córdoba, Argentina. PATIENTS: Forty anaesthetised patients with New York Heart Association class I or II, preoperative left ventricular ejection fraction at least 50% and Euroscore 6 or less scheduled for cardiac surgery with CPB. INTERVENTIONS: Patients were assigned to receive either standard ventilation with 6 cmH2O of positive end-expiratory pressure (PEEP; group C, n = 20) or standard ventilation with a recruitment manoeuvre and 10 cmH2O of PEEP after surgery (group RM, n = 20). RV function, left ventricular cardiac index (CI) and lung aeration were assessed by transoesophageal echocardiography (TOE) before, at the end of surgery and 30 min after surgery. MAIN OUTCOME MEASURES: RV function parameters and atelectasis assessed by TOE. RESULTS: Haemodynamic data and atelectasis were similar between groups before surgery. At the end of surgery, CI had decreased from 2.9 ±â€Š1.1 to 2.6 ±â€Š0.9 l min m in group C (P = 0.24) and from 2.8 ±â€Š1.0 to 2.6 ±â€Š0.8 l min m in group RM (P = 0.32). TOE-derived RV function parameters confirmed a mild decrease in RV performance in 95% of patients, without significant differences between groups (multivariate Hotelling t-test P = 0.16). Atelectasis was present in 18 patients in group C and 19 patients in group RM (P = 0.88). After surgery, CI decreased further from 2.6 to 2.4 l min m in group C (P = 0.17) but increased from 2.6 to 3.7 l min m in group RM (P < 0.001). TOE-derived RV function parameters improved only in group RM (Hotelling t-test P < 0.001). Atelectasis was present in 100% of patients in group C but only in 10% of those in group RM (P < 0.001). CONCLUSION: Atelectasis after CPB impairs RV function but this can be resolved by lung recruitment using 10 cmH2O of PEEP. TRIAL REGISTRATION: Protocol started on October 2014.

Magnesium sulphate improves pulmonary function after video-assisted thoracoscopic surgery: A randomised double-blind placebo-controlled study.

BACKGROUND: Reduced lung volumes are unavoidable after lung resection surgery. Magnesium sulphate (MgSO4) administration has been reported to reduce the requirement for neuromuscular blocking drugs and postoperative analgesics in surgical patients. OBJECTIVE: To investigate the effect of MgSO4 on pulmonary function after video-assisted thoracoscopic surgery (VATS). DESIGN: A randomised, double-blind, placebo-controlled trial. SETTING: A university tertiary care centre. PATIENTS: Sixty-six patients scheduled for pulmonary lobectomy or segmentectomy via VATS. INTERVENTION: Patients were allocated to one of two groups: the Mg (MgSO4 50 mg kg intravenously for 10 min, followed by a continuous infusion of 15 mg kg h during surgery) or the control (same volume of 0.9% saline). MAIN OUTCOME MEASURES: Pulmonary function tests [forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC) and peak expiratory flow rate] were measured before surgery and at three time points after surgery (2, 24 and 48 h postoperatively) using a portable spirometer. Twelve months after surgery, pulmonary function test values were repeated at a regular outpatient follow-up visit. RESULTS: FEV1 at 24 (1.7 ±â€Š0.6 vs. 1.3 ±â€Š0.5 l, P = 0.033) and 48 h (1.7 ±â€Š0.6 vs. 1.4 ±â€Š0.5 l, P = 0.021) and FVC at 24 (2.0 ±â€Š0.8 vs. 1.6 ±â€Š0.6 l, P = 0.038) and 48 h (2.2 ±â€Š0.8 vs. 1.7 ±â€Š0.7 l, P = 0.008) after surgery were significantly greater in the Mg group. Patients in the Mg group required less rocuronium than those in the control group (64.2 ±â€Š19.9 vs. 74.9 ±â€Š20.3 mg, respectively; P = 0.041). Consumption of postoperative patient-controlled analgesia was also significantly less at 24 and 48 h after surgery in the Mg group (P = 0.022 and 0.015, respectively), although pain scores and rescue analgesics were comparable. Five patients in the control group were diagnosed with postoperative pneumonia using clinical and radiological criteria before discharge. FEV1 and FVC at 12 months after surgery were not different between the two groups. CONCLUSION: Intraoperative administration of MgSO4 improved pulmonary function and reduced the need for rocuronium and postoperative analgesics in patients who underwent VATS. TRIAL REGISTRATION: cris.nih.go.kr identifier: KCT0001410.

Spontaneous breathing trial and post-extubation work of breathing in morbidly obese critically ill patients.

BACKGROUND: Predicting whether an obese critically ill patient can be successfully extubated may be specially challenging. Several weaning tests have been described but no physiological study has evaluated the weaning test that would best reflect the post-extubation inspiratory effort. METHODS: This was a physiological randomized crossover study in a medical and surgical single-center Intensive Care Unit, in patients with body mass index (BMI) >35 kg/m2 who were mechanically ventilated for more than 24 h and underwent a weaning test. After randomization, 17 patients were explored using five settings : pressure support ventilation (PSV) 7 and positive end-expiratory pressure (PEEP) 7 cmH2O; PSV 0 and PEEP 7cmH2O; PSV 7 and PEEP 0 cmH2O; PSV 0 and PEEP 0 cmH2O; and a T piece, and after extubation. To further minimize interaction between each setting, a period of baseline ventilation was performed between each step of the study. We hypothesized that the post-extubation work of breathing (WOB) would be similar to the T-tube WOB. RESULTS: Respiratory variables and esophageal and gastric pressure were recorded. Inspiratory muscle effort was calculated as the esophageal and trans-diaphragmatic pressure time products and WOB. Sixteen obese patients (BMI 44 kg/m2 ± 8) were included and successfully extubated. Post-extubation inspiratory effort, calculated by WOB, was 1.56 J/L ± 0.50, not statistically different from the T piece (1.57 J/L ± 0.56) or PSV 0 and PEEP 0 cmH2O (1.58 J/L ± 0.57), whatever the index of inspiratory effort. The three tests that maintained pressure support statistically underestimated post-extubation inspiratory effort (WOB 0.69 J/L ± 0.31, 1.15 J/L ± 0.39 and 1.09 J/L ± 0.49, respectively, p < 0.001). Respiratory mechanics and arterial blood gases did not differ between the five tests and the post-extubation condition. CONCLUSIONS: In obese patients, inspiratory effort measured during weaning tests with either a T-piece or a PSV 0 and PEEP 0 was not different to post-extubation inspiratory effort. In contrast, weaning tests with positive pressure overestimated post-extubation inspiratory effort. TRIAL REGISTRATION: Clinical trial.gov (reference NCT01616901 ), 2012, June 4th.

[Nasal Highflow (NHF): A New Therapeutic Option for the Treatment of Respiratory Failure]. / Nasaler Highflow (NHF): Eine neue Therapiealternative zur Behandlung der respiratorischen Insuffizienz.

The therapy of choice in hypoxemic respiratory failure (type 1) is the application of supplemental oxygen at flow rates of 1 to 15 l/min via nasal prongs or mask. Non-invasive or invasive positive pressure ventilation will be initiated when the oxygen therapy effects are not sufficient or if hypercapnic respiratory failure (type 2) is the underlying problem. Recently, an alternative therapy option is available, from the pathophysiology it can be classified between oxygen therapy and positive pressure ventilation. The therapy called Nasal High Flow (NHF) is based on the nasal application of a heated and humidified air oxygen mixture with a flow range of up to 60 l/min. The precise pathophysiological principles of NHF are only partly understood, yet various aspects are well studied already: it is possible to deliver high oxygen concentrations, airway dryness can be avoided, dead space ventilation reduced and clearance of nasal dead space is achieved. Additionally, an end expiratory positive pressure is built up, which helps to prevent airway collapse, thus resulting in an improvement of respiratory efficiency and reduction of breathing work. Current studies demonstrate improvement in gas exchange and reduction of reintubation rate when applying the NHF treatment in acute respiratory failure. Thus the NHF therapy attracts attention in intensive care medicine. The application in other fields like chronic respiratory insufficiency is less well clarified. The objectives of this review are to present the pathophysiological effects and mechanisms of NHF, as far as understood, and to give an overview over the current state of relevant studies.

Intraoperative Lung-Protective Ventilation Trends and Practice Patterns: A Report from the Multicenter Perioperative Outcomes Group.

BACKGROUND: The use of an intraoperative lung-protective ventilation strategy through tidal volume (TV) size reduction and positive end-expiratory pressure (PEEP) has been increasingly investigated. In this article, we describe the current intraoperative lung-protective ventilation practice patterns and trends. METHODS: By using the Multicenter Perioperative Outcomes Group database, we identified all general endotracheal anesthetics from January 2008 through December 2013 at 10 institutions. The following data were calculated: (1) percentage of patients receiving TV > 10 mL/kg predicted body weight (PBW); (2) median initial and overall TV in mL/kg PBW and; (3) percentage of patients receiving PEEP ≥ 5 cm H2O. The data were analyzed at 3-month intervals. Interinstitutional variability was assessed. RESULTS: A total of 330,823 patients met our inclusion criteria for this study. During the study period, the percentage of patients receiving TV > 10 mL/kg PBW was reduced for all patients (26% to 14%) and in the subpopulations of obese (41% to 25%), short stature (52% to 36%), and females (39% to 24%; all P values <0.001). There was a significant reduction in TV size (8.90-8.20 mL/kg PBW, P < 0.001). There was also a statistically significant but clinically irrelevant difference between initial and overall TV size (8.65 vs 8.63 mL/kg PBW, P < 0.001). Use of PEEP ≥ 5 cm H2O increased during the study period (25%-45%, P < 0.001). TV usage showed significant interinstitutional variability (P < 0.001). CONCLUSIONS: Although decreasing, a significant percentage of patients are ventilated with TV > 10 mL/kg PBW, especially if they are female, obese, or of short stature. The use of PEEP ≥ 5 cm H2O has increased significantly. Creating awareness of contemporary practice patterns and demonstrating the efficacy of lung-protective ventilation are still needed to optimize intraoperative ventilation.