Positive End-expiratory Pressure In Patients Research Articles

Correlation between normally aerated lung and respiratory system compliance at clinical high positive end-expiratory pressure in patients with COVID-19

Normally aerated lung tissue on computed tomography (CT) is correlated with static respiratory system compliance (Crs) at zero end-expiratory pressure. In clinical practice, however, patients with acute respiratory failure are often managed using elevated PEEP levels. No study has validated the relationship between lung volume and tissue and Crs at the applied positive end-expiratory pressure (PEEP). Therefore, this study aimed to demonstrate the relationship between lung volume and tissue on CT and Crs during the application of PEEP for the clinical management of patients with acute respiratory distress syndrome due to COVID-19. Additionally, as a secondary outcome, the study aimed to evaluate the relationship between CT characteristics and Crs, considering recruitability using the recruitment-to-inflation ratio (R/I ratio). We analyzed the CT and respiratory mechanics data of 30 patients with COVID-19 who were mechanically ventilated. The CT images were acquired during mechanical ventilation at PEEP level of 15 cmH2O and were quantitatively analyzed using Synapse Vincent system version 6.4 (Fujifilm Corporation, Tokyo, Japan). Recruitability was stratified into two groups, high and low recruitability, based on the median R/I ratio of our study population. Thirty patients were included in the analysis with the median R/I ratio of 0.71. A significant correlation was observed between Crs at the applied PEEP (median 15 [interquartile range (IQR) 12.2, 15.8]) and the normally aerated lung volume (r = 0.70 [95% CI 0.46–0.85], P < 0.001) and tissue (r = 0.70 [95% CI 0.46–0.85], P < 0.001). Multivariable linear regression revealed that recruitability (Coefficient = − 390.9 [95% CI − 725.0 to − 56.8], P = 0.024) and Crs (Coefficient = 48.9 [95% CI 32.6–65.2], P < 0.001) were significantly associated with normally aerated lung volume (R-squared: 0.58). In this study, Crs at the applied PEEP was significantly correlated with normally aerated lung volume and tissue on CT. Moreover, recruitability indicated by the R/I ratio and Crs were significantly associated with the normally aerated lung volume. This research underscores the significance of Crs at the applied PEEP as a bedside-measurable parameter and sheds new light on the link between recruitability and normally aerated lung.

Phenotypes of esophageal pressure response to the change of positive end-expiratory pressure in patients with moderate acute respiratory distress syndrome.

Esophageal pressure (Pes) has been used as a surrogate of pleural pressure (Ppl) to titrate positive end-expiratory pressure (PEEP) in acute respiratory distress syndrome (ARDS) patients. The relationship between Pes and PEEP remains undetermined. A gastric tube with a balloon catheter was inserted to monitor Pes in moderate to severe ARDS patients who underwent invasive mechanical ventilation. To assess the end-expiratory Pes response (ΔPes) to PEEP changes (ΔPEEP), the PEEP level was decreased and increased subsequently (with an average change of 3 cmH2O). The patients underwent the following two series of PEEP adjustment: (I) from PEEP-3 cmH2O to PEEPbaseline; and (II) from PEEPbaseline to PEEP+3 cmH2O. The patients were classified as "PEEP-dependent type" if they had ΔPes ≥30% ΔPEEP and were otherwise classified as "PEEP-independent type" (ΔPes <30% ΔPEEP in any series). In total, 54 series of PEEP adjustments were performed in 18 ARDS patients. Of these patients, 12 were classified as PEEP-dependent type, and six were classified as PEEP-independent type. During the PEEP adjustment, end-expiratory Pes changed significantly in the PEEP-dependent patients, who had a Pes of 10.8 (7.9, 12.3), 12.5 (10.5, 14.9), and 14.5 (13.1, 18.3) cmH2O at PEEP-3 cmH2O, PEEPbaseline, and PEEP+3 cmH2O, respectively (median and quartiles; P<0.0001), while end-expiratory transpulmonary pressure (PL) was maintained at an optimal range [-0.1 (-0.7, 0.4), 0.1 (-0.6, 0.5), and 0.3 (-0.3, 0.7) cmH2O, respectively]. In the PEEP-independent patients, the Pes remained unchanged, with a Pes of 15.4 (11.4, 17.8), 15.5 (11.6, 17.8), and 15.4 (11.7, 18.30) cmH2O at each of the three PEEP levels, respectively. Meanwhile, end-expiratory PL significantly improved [from -5.5 (-8.5, -3.4) at PEEP-3 cmH2O to -2.5 (-5.0, -1.6) at PEEPbaseline to -0.5 (-1.8, 0.3) at PEEP+3 cmH2O; P<0.01]. Two types of Pes phenotypes were identified according to the ΔPes to ΔPEEP. The underlying mechanisms and implications for clinical practice require further exploration.

Myocardial Function during Ventilation with Lower versus Higher Positive End-Expiratory Pressure in Patients without ARDS.

The aim of this study was to investigate whether lower PEEP (positive end-expiratory pressure) had beneficial effects on myocardial function among intensive care unit (ICU) patients without acute respiratory distress syndrome (ARDS) compared to higher PEEP. In this pre-planned substudy of a randomized controlled trial (RELAx), comparing lower to higher PEEP, 44 patients underwent transthoracic echocardiography. The exclusion criteria were known poor left ventricular function and severe shock requiring high dosages of norepinephrine. To create contrast, we also excluded patients who received PEEP between 2 cmH2O and 7 cmH2O in the two randomization arms of the study. The primary outcome was the right ventricular myocardial performance index (MPI), a measure of systolic and diastolic function. The secondary outcomes included systolic and diastolic function parameters. A total of 20 patients were ventilated with lower PEEP (mean ± SD, 0 ± 1 cmH2O), and 24 patients, with higher PEEP (8 ± 1 cmH2O) (mean difference, −8 cmH2O; 95% CI: −8.1 to −7.9 cmH2O; p = 0.01). The tidal volume size was low in both groups (median (IQR), 7.2 (6.3 to 8.1) versus 7.0 (5.3 to 9.1) ml/kg PBW; p = 0.97). The median right ventricular MPI was 0.32 (IQR, 0.26 to 0.39) in the lower-PEEP group versus 0.38 (0.32 to 0.41) in the higher-PEEP group; the median difference was –0.03; 95% CI: −0.11 to 0.03; p = 0.33. The other systolic and diastolic parameters were similar. In patients without ARDS ventilated with a low tidal volume, a lower PEEP had no beneficial effects on the right ventricular MPI.

The critical care literature 2020.

Given the dramatic increase in critically ill patients who present to the emergency department for care, along with the persistence of boarding of critically ill patients, it is imperative for the emergency physician to be knowledgeable about recent developments in resuscitation and critical care medicine. This review summarizes important articles published in 2020 that pertain to the resuscitation and care of select critically ill patients. These articles have been selected based on the authors annual review of key critical care, emergency medicine and medicine journals and their opinion of the importance of study findings as it pertains to the care of critically ill ED patients. Several key findings from the studies discussed in this paper include the administration of dexamethasone to patients with COVID-19 infection who require mechanical ventilation or supplemental oxygen, the use of lower levels of positive end-expiratory pressure for patients without acute respiratory distress syndrome, and early initiation of extracorporeal membrane oxygenation for out-of-hospital cardiac arrest patients with refractory ventricular fibrillation if resources are available. Furthermore, the emergency physician should not administer tranexamic acid to patients with acute gastrointestinal bleeding or administer the combination of vitamin C, thiamine, and hydrocortisone for patients with septic shock. Finally, the emergency physician should titrate vasopressor medications to more closely match a patient's chronic perfusion pressure rather than target a mean arterial blood pressure of 65 mmHg for all critically ill patients.

Higher versus lower positive end-expiratory pressure in patients without acute respiratory distress syndrome: a meta-analysis of randomized controlled trials

BackgroundWe conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) to assess the association of higher positive end-expiratory pressure (PEEP), as opposed to lower PEEP, with hospital mortality in adult intensive care unit (ICU) patients undergoing invasive mechanical ventilation for reasons other than acute respiratory distress syndrome (ARDS).MethodsWe performed an electronic search of MEDLINE, EMBASE, Scopus, Cochrane Central Register of Controlled Trials, CINAHL, and Web of Science from inception until June 16, 2021 with no language restrictions. In addition, a research-in-progress database and grey literature were searched.ResultsWe identified 22 RCTs (2225 patients) comparing higher PEEP (1007 patients) with lower PEEP (991 patients). No statistically significant association between higher PEEP and hospital mortality was observed (risk ratio 1.02, 95% confidence interval 0.89–1.16; I2 = 0%, p = 0.62; low certainty of evidence). Among secondary outcomes, higher PEEP was associated with better oxygenation, higher respiratory system compliance, and lower risk of hypoxemia and ARDS occurrence. Furthermore, barotrauma, hypotension, duration of ventilation, lengths of stay, and ICU mortality were similar between the two groups.ConclusionsIn our meta-analysis of RCTs, higher PEEP, compared with lower PEEP, was not associated with mortality in patients without ARDS receiving invasive mechanical ventilation. Further large high-quality RCTs are required to confirm these findings.

Traumatic brain injury in children with thoracic injury: clinical significance and impact on ventilatory management.

PurposeThis study aims to describe the epidemiology and management of chest trauma in our center, and to compare patterns of mechanical ventilation in patients with or without associated moderate-to-severe traumatic brain injury (TBI).MethodsAll children admitted to our level-1 trauma center from February 2012 to December 2018 following chest trauma were included in this retrospective study.ResultsA total of 75 patients with a median age of 11 [6–13] years, with thoracic injuries were included. Most patients also had extra-thoracic injuries (n = 71, 95%) and 59 (79%) had TBI. A total of 52 patients (69%) were admitted to intensive care and 31 (41%) were mechanically ventilated. In patients requiring mechanical ventilation, there was no difference in tidal volume or positive end-expiratory pressure in patients with moderate-to-severe TBI when compared with those with no-or-mild TBI. Only one patient developed Acute Respiratory Distress Syndrome. A total of 6 patients (8%) died and all had moderate-to-severe TBI.ConclusionIn this small retrospective series, most patients requiring mechanical ventilation following chest trauma had associated moderate-to-severe TBI. Mechanical ventilation to manage TBI does not seem to be associated with more acute respiratory distress syndrome occurrence.

Assessment of Lung Reaeration at 2 Levels of Positive End-expiratory Pressure in Patients With Early and Late COVID-19-related Acute Respiratory Distress Syndrome.

Patients with novel coronavirus disease (COVID-19) frequently develop acute respiratory distress syndrome (ARDS) and need invasive ventilation. The potential to reaerate consolidated lung tissue in COVID-19-related ARDS is heavily debated. This study assessed the potential to reaerate lung consolidations in patients with COVID-19-related ARDS under invasive ventilation. This was a retrospective analysis of patients with COVID-19-related ARDS who underwent chest computed tomography (CT) at low positive end-expiratory pressure (PEEP) and after a recruitment maneuver at high PEEP of 20 cm H2O. Lung reaeration, volume, and weight were calculated using both CT scans. CT scans were performed after intubation and start of ventilation (early CT), or after several days of intensive care unit admission (late CT). Twenty-eight patients were analyzed. The median percentages of reaerated and nonaerated lung tissue were 19% [interquartile range, IQR: 10 to 33] and 11% [IQR: 4 to 15] for patients with early and late CT scans, respectively (P=0.049). End-expiratory lung volume showed a median increase of 663 mL [IQR: 483 to 865] and 574 mL [IQR: 292 to 670] after recruitment for patients with early and late CT scans, respectively (P=0.43). The median decrease in lung weight attributed to nonaerated lung tissue was 229 g [IQR: 165 to 376] and 171 g [IQR: 81 to 229] after recruitment for patients with early and late CT scans, respectively (P=0.16). The majority of patients with COVID-19-related ARDS undergoing invasive ventilation had substantial reaeration of lung consolidations after recruitment and ventilation at high PEEP. Higher PEEP can be considered in patients with reaerated lung consolidations when accompanied by improvement in compliance and gas exchange.

Individualized positive end-expiratory pressure in patients undergoing thoracoscopic lobectomy: a randomized controlled trial

Background and objectivesWith the intensive study of lung protective ventilation strategies, people begin to advocate the individualized application of positive end-expiratory pressure (PEEP). This study investigated the optimal PEEP in patients during one-lung ventilation (OLV) and its effects on pulmonary mechanics and oxygenation. MethodsFifty-eight patients who underwent elective thoracoscopic lobectomy were randomly divided into two groups. Both groups received an alveolar recruitment maneuver (ARM) after OLV. Patients in Group A received optimal PEEP followed by PEEP decremental titration, while Group B received standard 5 cmH2O PEEP until the end of OLV. Relevant indexes of respiratory mechanics, pulmonary oxygenation and hemodynamics were recorded after entering the operating room (T0), 10 minutes after intubation (T1), pre-ARM (T2), 20 minutes after the application of optimal PEEP (T3), at the end of OLV (T4) and at the end of surgery (T5). Postoperative outcomes were also assessed. ResultsThe optimal PEEP obtained in Group A was 8.8 ± 2.4 cmH2O, which positively correlated with BMI and forced vital capacity (FVC). Group A had a higher CPAT than Group B at T3, T4, T5 (p < 0.05) and a smaller ΔP than Group B at T3, T4 (p < 0.01). At T4, PaO2 was significantly higher in Group A (p < 0.01). At T3, stroke volume variation was higher in Group A (p < 0.01). Postoperative outcomes did not differ between the two groups. ConclusionsOur findings suggest that the individualized PEEP can increase lung compliance, reduce driving pressure, and improve pulmonary oxygenation in patients undergoing thoracoscopic lobectomy, with little effect on hemodynamics.

Critically Ill Adults With Coronavirus Disease 2019 in New Orleans and Care With an Evidence-Based Protocol

BackgroundCharacteristics of critically ill adults with coronavirus disease 2019 (COVID-19) in an academic safety net hospital and the effect of evidence-based practices in these patients are unknown.Research QuestionWhat are the outcomes of critically ill adults with COVID-19 admitted to a network of hospitals in New Orleans, Louisiana, and what is an evidence-based protocol for care associated with improved outcomes?Study Design and MethodsIn this multi-center, retrospective, observational cohort study of ICUs in four hospitals in New Orleans, Louisiana, we collected data on adults admitted to an ICU and tested for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) between March 9, 2020 and April 14, 2020. The exposure of interest was admission to an ICU that implemented an evidence-based protocol for COVID-19 care. The primary outcome was ventilator-free days.ResultsThe initial 147 patients admitted to any ICU and tested positive for SARS-CoV-2 constituted the cohort for this study. In the entire network, exposure to an evidence-based protocol was associated with more ventilator-free days (25 days; 0-28) compared with non-protocolized ICUs (0 days; 0-23, P = .005), including in adjusted analyses (P = .02). Twenty patients (37%) admitted to protocolized ICUs died compared with 51 (56%; P = .02) in non-protocolized ICUs. Among 82 patients admitted to the academic safety net hospital’s ICUs, the median number of ventilator-free days was 22 (interquartile range, 0-27) and mortality rate was 39%.InterpretationCare of critically ill COVID-19 patients with an evidence-based protocol is associated with increased time alive and free of invasive mechanical ventilation. In-hospital survival occurred in most critically ill adults with COVID-19 admitted to an academic safety net hospital’s ICUs despite a high rate of comorbidities.

Individualized positive end-expiratory pressure setting in patients with severe acute respiratory distress syndrome supported with veno-venous extracorporeal membrane oxygenation.

Patients with acute respiratory distress syndrome supported with veno-venous extracorporeal membrane oxygenation benefit from higher positive end-expiratory pressure combined with conventional ventilation during the early extracorporeal membrane oxygenation period. The role of incremental positive end-expiratory pressure titration in patients with severe acute respiratory distress syndrome supported with veno-venous extracorporeal membrane oxygenation remains unclear. This study aimed to determine the preferred method for setting positive end-expiratory pressure in patients with severe acute respiratory distress syndrome on veno-venous extracorporeal membrane oxygenation support. We retrospectively reviewed all subjects supported with veno-venous extracorporeal membrane oxygenation for severe acute respiratory distress syndrome from 2009 to 2019 in the intensive care units in Tianjin Third Central Hospital. Subjects were divided into two groups according to the positive end-expiratory pressure titration method used: P-V curve (quasi-static pressure-volume curve-guided positive end-expiratory pressure setting) group or Crs (respiratory system compliance-guided positive end-expiratory pressure setting) group. Forty-three subjects were included in the clinical outcome analysis: 20 in the P-V curve group and 23 in the Crs group. Initial positive end-expiratory pressure levels during veno-venous extracorporeal membrane oxygenation were similar in both groups. Incidence rates of barotrauma and hemodynamic events were significantly lower in the Crs group (all p < 0.05). Mechanical ventilation duration, intensive care unit length of stay, and hospital length of stay were significantly shorter in the Crs group than the P-V curve group (all p < 0.05). Subjects in the Crs group showed non-significant improvements in the duration of extracorporeal membrane oxygenation support and 28-day mortality (p > 0.05). Respiratory system compliance-guided positive end-expiratory pressure setting may lead to more optimal clinical outcomes for patients with severe acute respiratory distress syndrome supported by veno-venous extracorporeal membrane oxygenation. Moreover, the operation is simple, safe, and convenient in clinical practice.

Mortality in COVID-19 is not merely a question of resource availability

Mortality in COVID-19 is not merely a question of resource availability

Personalised mechanical ventilation tailored to lung morphology versus low positive end-expiratory pressure for patients with acute respiratory distress syndrome in France (the LIVE study): a multicentre, single-blind, randomised controlled trial

The effect of personalised mechanical ventilation on clinical outcomes in patients with acute respiratory distress syndrome (ARDS) remains uncertain and needs to be evaluated. We aimed to test whether a mechanical ventilation strategy that was personalised to individual patients' lung morphology would improve the survival of patients with ARDS when compared with standard of care. We designed a multicentre, single-blind, stratified, parallel-group, randomised controlled trial enrolling patients with moderate-to-severe ARDS in 20 university or non-university intensive care units in France. Patients older than 18 years with early ARDS for less than 12 h were randomly assigned (1:1) to either the control group or the personalised group using a minimisation algorithm and stratified according to the study site, lung morphology, and duration of mechanical ventilation. Only the patients were masked to allocation. In the control group, patients received a tidal volume of 6 mL/kg per predicted bodyweight and positive end-expiratory pressure (PEEP) was selected according to a low PEEP and fraction of inspired oxygen table, and early prone position was encouraged. In the personalised group, the treatment approach was based on lung morphology; patients with focal ARDS received a tidal volume of 8 mL/kg, low PEEP, and prone position. Patients with non-focal ARDS received a tidal volume of 6 mL/kg, along with recruitment manoeuvres and high PEEP. The primary outcome was 90-day mortality as established by intention-to-treat analysis. This study is registered online with ClinicalTrials.gov, NCT02149589. From June 12, 2014, to Feb 2, 2017, 420 patients were randomly assigned to treatment. 11 patients were excluded in the personalised group and nine patients were excluded in the control group; 196 patients in the personalised group and 204 in the control group were included in the analysis. In a multivariate analysis, there was no difference in 90-day mortality between the group treated with personalised ventilation and the control group in the intention-to-treat analysis (hazard ratio [HR] 1·01; 95% CI 0·61-1·66; p=0·98). However, misclassification of patients as having focal or non-focal ARDS by the investigators was observed in 85 (21%) of 400 patients. We found a significant interaction between misclassification and randomised group allocation with respect to the primary outcome (p<0·001). In the subgroup analysis, the 90-day mortality of the misclassified patients was higher in the personalised group (26 [65%] of 40 patients) than in the control group (18 [32%] of 57 patients; HR 2·8; 95% CI 1·5-5·1; p=0·012. Personalisation of mechanical ventilation did not decrease mortality in patients with ARDS, possibly because of the misclassification of 21% of patients. A ventilator strategy misaligned with lung morphology substantially increases mortality. Whether improvement in ARDS phenotyping can decrease mortality should be assessed in a future clinical trial. French Ministry of Health (Programme Hospitalier de Recherche Clinique InterRégional 2013).

Effects of Hemodynamic Factors and Oxygenation on the Incidence of Pressure Ulcers in the ICU.

To investigate the roles of hemodynamic factors and oxygenation on the incidence of pressure ulcers in patients in the ICU on mechanical ventilation. This prospective analytical cross-sectional study was performed in several ICUs for a period of 8 months in Iran. Researchers checked patients for pressure ulcers on a daily basis. They collected demographic, hemodynamic, and oxygenation data until a pressure ulcer occurred, the patient's artificial airway was removed, the patient died, or the patient was discharged. From August 2017 to February 2018, a total of 2,581 patients were admitted to the study ICUs; of these, 133 patients were eligible for the study. The results indicated that 41.4% (n = 55) of the patients ended up with pressure ulcers. Investigation of the variables using a Cox regression model showed that, among other variables considered in this study, age, mean arterial pressure, and positive end-expiratory pressure in the mechanical ventilator can contribute to the risk of pressure ulcers. Providers should pay attention to changes in hemodynamic parameters, especially mean arterial pressure; carefully determine the most appropriate positive end-expiratory pressure for patients connected to mechanical ventilation; and take special care of susceptible groups such as older adults and hospitalized patients to decrease the incidence of pressure ulcers.

The effects of recruitment maneuver during noninvasive ventilation after coronary bypass grafting: A randomized trial

ObjectivePulmonary impairment is a common complication after coronary artery bypass graft procedure and may be prevented or treated by noninvasive ventilation. Recruitment maneuvers include sustained airway pressure with high levels of positive end-expiratory pressure in patients with hypoxemia, favoring homogeneous pulmonary ventilation and oxygenation. This study aimed to evaluate whether noninvasive ventilation with recruitment maneuver could safely improve oxygenation in patients with atelectasis and hypoxemia who underwent a coronary artery bypass grafting procedure. MethodsThirty-four patients admitted to our intensive care unit undergoing mechanical ventilation after surgery, with ratio of arterial oxygen partial pressure to fraction of inspired oxygen < 300 and radiologic atelectasis score ≥2, were included. The control group consisted of 16 randomized patients and the recruitment group consisted of 18 patients. After extubation, noninvasive ventilation was applied for 30 minutes 3 times a day with positive end-expiratory pressure of 8 cm H2O. The recruitment group received recruitment maneuver with positive end-expiratory pressure of 15 cm H2O and 20 cm H2O for 2 minutes each during noninvasive ventilation. We analyzed the arterial oxygen partial pressure in room air, radiologic atelectasis score, hemodynamic stability, and adverse events from extubation until discharge. ResultsArterial oxygen partial pressure increased 12.6% ± 6.8% in the control group and 23.3% ± 8.5% in the recruitment group (P < .001). The radiologic atelectasis score was completely improved for 94.4% of the recruitment group with no adverse events, whereas 87.5% of the control group presented some atelectasis (P < .001). ConclusionsNoninvasive ventilation with recruitment maneuvers is safe, improves oxygenation, and reduces atelectasis in patients undergoing coronary artery bypass.

RELAx \u2013 REstricted versus Liberal positive end-expiratory pressure in patients without ARDS: protocol for a randomized controlled trial

BackgroundEvidence for benefit of high positive end-expiratory pressure (PEEP) is largely lacking for invasively ventilated, critically ill patients with uninjured lungs. We hypothesize that ventilation with low PEEP is noninferior to ventilation with high PEEP with regard to the number of ventilator-free days and being alive at day 28 in this population. Methods/DesignThe “REstricted versus Liberal positive end-expiratory pressure in patients without ARDS” trial (RELAx) is a national, multicenter, randomized controlled, noninferiority trial in adult intensive care unit (ICU) patients with uninjured lungs who are expected not to be extubated within 24 h. RELAx will run in 13 ICUs in the Netherlands to enroll 980 patients under invasive ventilation. In all patients, low tidal volumes are used. Patients assigned to ventilation with low PEEP will receive the lowest possible PEEP between 0 and 5 cm H2O, while patients assigned to ventilation with high PEEP will receive PEEP of 8 cm H2O. The primary endpoint is the number of ventilator-free days and being alive at day 28, a composite endpoint for liberation from the ventilator and mortality until day 28, with a noninferiority margin for a difference between groups of 0.5 days. Secondary endpoints are length of stay (LOS), mortality, and occurrence of pulmonary complications, including severe hypoxemia, major atelectasis, need for rescue therapies, pneumonia, pneumothorax, and development of acute respiratory distress syndrome (ARDS). Hemodynamic support and sedation needs will be collected and compared.DiscussionRELAx will be the first sufficiently sized randomized controlled trial in invasively ventilated, critically ill patients with uninjured lungs using a clinically relevant and objective endpoint to determine whether invasive, low-tidal-volume ventilation with low PEEP is noninferior to ventilation with high PEEP.Trial registrationClinicalTrials.gov, ID:NCT03167580. Registered on 23 May 2017.

Compliance-guided versus FiO2-driven positive-end expiratory pressure in patients with moderate or severe acute respiratory distress syndrome according to the Berlin definition

ObjectiveTo study the effect of setting positive end-expiratory pressure (PEEP) in an individualized manner (based on highest static compliance) compared to setting PEEP according to FiO2 upon mortality at 28 and 90 days, in patients with different severity acute respiratory distress syndrome (ARDS). SettingA Spanish medical–surgical ICU. DesignA post hoc analysis of a randomized controlled pilot study. PatientsPatients with ARDS. InterventionsVentilation with low tidal volumes and pressure limitation at 30cmH2O, randomized in two groups according to the method used to set PEEP: FiO2-guided PEEP group according to FiO2 applied and compliance-guided group according to the highest compliance. Primary variables of interestDemographic data, risk factors and severity of ARDS, APACHE II and SOFA scores, daily Lung Injury Score, ventilatory measurements, ICU and hospital stay, organ failure and mortality at day 28 and 90 after inclusion. ResultsA total of 159 patients with ARDS were evaluated, but just 70 patients were included. Severe ARDS patients showed more organ dysfunction-free days at 28 days (12.83±10.70 versus 3.09±7.23; p=0.04) and at 90 days (6.73±22.31 vs. 54.17±42.14, p=0.03), and a trend toward lower 90-days mortality (33.3% vs. 90.9%, p=0.02), when PEEP was applied according to the best static compliance. Patients with moderate ARDS did not show these effects. ConclusionsIn patients with severe ARDS, individualized PEEP selection based on the best static compliance was associated to lower mortality at 90 days, with an increase in organ dysfunction-free days at 28 and 90 days.

Volume capnography: A narrative review

Volume capnography is the graph of expired carbon dioxide concentration against the expired volume. It often requires special and bulky equipment to be recorded. It can be used to estimate the dead space with fair amount of precision. Various formulae and equations have been described to estimate the dead space. While the Bohr formula is likely the most accurate for measurement of dead space, the Enghoff's equation is likely the most popular and convenient to use. Volume capnography has found uses in both the operating room (OR) and the Intensive Care Unit setting. It can be used to identify the optimal level of positive end-expiratory pressure in patients suffering from the acute respiratory distress syndrome as well as to identify its effect on the ventilation. In the OR, it can be invaluable to monitor ventilation and alveolar recruitment in the obese population. It is also a useful diagnostic adjunct in medical emergencies like pulmonary embolism. In the pediatric population, it finds uses in the monitoring of infants suffering from bronchiolitis. In spite of its multiple and diverse uses, it remains an underutilized technology; the main reasons for this being lack of experience of the providers with volume capnography and the expensive and bulky equipment that is often required. However, volume capnography has a great deal of potential and with further advances in technology, is likely to gain popularity.

Compliance-guided versus FiO2-driven positive-end expiratory pressure in patients with moderate or severe acute respiratory distress syndrome according to the Berlin definition

ObjectiveTo study the effect of setting positive end-expiratory pressure (PEEP) in an individualized manner (based on highest static compliance) compared to setting PEEP according to FiO2 upon mortality at 28 and 90 days, in patients with different severity acute respiratory distress syndrome (ARDS). SettingA Spanish medical–surgical ICU. DesignA post hoc analysis of a randomized controlled pilot study. PatientsPatients with ARDS. InterventionsVentilation with low tidal volumes and pressure limitation at 30cmH2O, randomized in two groups according to the method used to set PEEP: FiO2-guided PEEP group according to FiO2 applied and compliance-guided group according to the highest compliance. Primary variables of interestDemographic data, risk factors and severity of ARDS, APACHE II and SOFA scores, daily Lung Injury Score, ventilatory measurements, ICU and hospital stay, organ failure and mortality at day 28 and 90 after inclusion. ResultsA total of 159 patients with ARDS were evaluated, but just 70 patients were included. Severe ARDS patients showed more organ dysfunction-free days at 28 days (12.83±10.70 versus 3.09±7.23; p=0.04) and at 90 days (6.73±22.31 vs. 54.17±42.14, p=0.03), and a trend toward lower 90-days mortality (33.3% vs. 90.9%, p=0.02), when PEEP was applied according to the best static compliance. Patients with moderate ARDS did not show these effects. ConclusionsIn patients with severe ARDS, individualized PEEP selection based on the best static compliance was associated to lower mortality at 90 days, with an increase in organ dysfunction-free days at 28 and 90 days.

The study of fluid responsiveness predicted by adjustion of positive end-expiratory pressure in patients with septic shock

The study of fluid responsiveness predicted by adjustion of positive end-expiratory pressure in patients with septic shock

Lung Ultrasonography for the Detection of Anesthesia-induced Lung Atelectasis

We have read with great interest the article by Acosta et al.1 exploring the use of lung ultrasound as a mean to detect intraoperative atelectasis. However, despite their statement to the contrary, the occurrence of B lines in the setting of atelectasis has already been described by others. Although B lines were initially thought to originate from the interaction of the ultrasound beam with thickened subpleural interlobular septa found in alveolar-interstitial pathologies,2 recent work has challenged this hypothesis. In an elegant series of experiments, Soldati et al.3–5 have shown that B lines are observed when the ultrasound beam interacts at the pleural surface with lung tissue of a specific density. Although this can occur with the replacement of subpleural air by an ultrasound-conductive substance (e.g., water, pus, blood, and fibrous tissue), the withdrawal of air (e.g., resorption atelectasis) will also lead to the genesis of B lines. Demonstrating this last point, in an ex vivo animal model of graded atelectasis, B lines were observed in increasing numbers with increasing atelectasis. Pathologic examination of the excised lungs showed diffusely compressed alveoli mixed with sporadic areas of normally expanded distal air spaces.5The study by Acosta et al. comes at an interesting moment. The recent publication of two randomized controlled trials6,7 exploring the impact of intraoperative mechanical ventilation parameters on postoperative pulmonary complications has generated much interest.8 Although some have linked the negative results of the PROVHILO (PROtective Ventilation using HIgh versus LOw positive end-expiratory pressure) trial to a lack of regular recruitment maneuvers and a positive end-expiratory pressure set too high,9 others blame the use of inappropriately high tidal volumes in the control group for the positive results in the IMPROVE (Intraoperative PROtective VEntilation) trial.10 In the absence of imagery supporting claims of atelectasis or overdistention, the culprits usually blamed for the development of postoperative pulmonary complications, it is unlikely this question will be resolved before more data becomes available. Interestingly, recent anesthesiology literature has demonstrated the advantage of hemodynamic optimization11 championing the concept that individualization is preferable to a “one size fits all” approach. Likewise, individualization of mechanical ventilation parameters might be an interesting avenue to explore if we wish to decrease the occurrence of postoperative respiratory complications. This hypothesis is supported by spiral computed tomography studies reporting significant interpatient variability in the amount of atelectasis induced by general anesthesia.12,13 Therefore, we believe that bedside monitoring to detect lung atelectasis or overdistention is needed. Although magnetic resonance imaging and computed tomography fulfill this requirement, they cannot be used in an intraoperative setting except in specially designed operating rooms and could not realistically be repeated throughout a procedure. Because lung ultrasonography can be performed at the bedside and is devoid of any ionizing radiation, the present study by Acosta et al., although interesting in and of itself, is an important milestone toward establishing lung ultrasonography as a tool to optimize intraoperative mechanical ventilation parameters. Other investigators have described loss of aeration scales that have allowed the study of the therapeutic effects of antibiotics in ventilator-associated pneumonia,14 the effect of different levels of positive end-expiratory pressure in patients with acute respiratory distress syndrome on lung reexpansion15 and the detection of patients likely to fail extubation after a successful spontaneous breathing trial.16 Although not developed specifically for the diagnosis and monitoring of anesthesia-induced atelectasis, the use of these scales would have been an interesting addition to the study by Acosta et al. Whether to optimize intraoperative mechanical ventilation parameters or to assist anesthesiologists in the care of hypoxemic patients, lung ultrasonography is likely to have a bright future in our operating rooms.Supported by Grant of the Fondation 2013, Fondation d’anesthésiologie et réanimation du Québec; Grant of the Fonds de développement 2014, Département d’anesthésiologie, Université de Montréal.The authors declare no competing interests.