Invasive Mechanical Ventilation.

Invasive mechanical ventilation allows clinicians to support gas exchange and work of breathing in patients with respiratory failure. However, there is also potential for iatrogenesis. By understanding the benefits and limitations of different modes of ventilation and goals for gas exchange, clinicians can choose a strategy that provides appropriate support while minimizing harm. The ventilator can also provide crucial diagnostic information in the form of respiratory mechanics. These, and the mechanical ventilation strategy, should be regularly reassessed.

Correlations between APACHE-II score and pressure parameters of mechanical ventilation in patients with ARDS and their value in prognostic evaluation.

Objective: To investigate the correlations between APACHE-II score and pressure parameters of mechanical ventilation in patients with acute respiratory distress syndrome (ARDS) and their value in prognostic evaluation. Methods: This was a retrospective study. The clinical data of 79 patients with ARDS treated in Shengzhou Hospital of Traditional Chinese Medicine from April 2020 to April 2022 were analyzed retrospectively. According to whether their APACHE-II scores were higher than 15, they were divided into low score group (n= 20) and high score group (n= 59). The plateau pressure (Pplat), driving pressure(ΔP) and mean airway pressure (Pmean) were compared. The correlation between APACHE-II score and pressure parameters of mechanical ventilation was analyzed. Based on the follow-up of 28-d survival, their Pplat, ΔP, Pmean and APACHE-II scores were compared. The value of APACHE-II score and pressure parameters in the prognostic evaluation of ARDS patients was analyzed. Results: Pplat, ΔP and Pmean in the low score group were significantly lower than those in the high score group(P<0.05). Pplat, ΔP, Pmean and APACHE-II score in the survival group were significantly lower than those in the control group(P<0.05). APACHE-II score showed significantly positive correlations with Pplat, ΔP and Pmean. The AUC of Pmean, Pplat, ΔP and APACHE-II score in predicting the prognosis and diagnosis of ARDS patients was 0.761, 0.833, 0.754 and 0.832, respectively. Conclusion: APACHE-II score of ARDS patients shows significantly positive correlations with pressure parameters of mechanical ventilation, and has diagnostic value for the prognosis of ARDS patients.

Intraoperative lung-protective ventilation adjusting tidal volume to a plateau pressure restriction in elderly patients: A randomized controlled clinical trial.

BACKGROUND: Lung-protective ventilation (LPV) strategies have been considered as best practice in the care of critically patients. OBJECTIVE: This study aimed to investigate the effects individualized perioperative LPV with a positive end-expiratory pressure (PEEP) and low tidal volumes (VT) based on a target airway plateau pressure (Pplat) in patients during and after an operation compared with conventional ventilation in elderly patients during abdominal surgery. METHODS: Sixty-one elderly patients with American Society of Anesthesiologists (ASA) I to III undergoing open abdominal surgery received either conventional ventilation (8 ml/kg-1VT; CV group) or LPV (VT was adjusted to a target Pplat [⩽ 20 cm H2O]) in the volume-controlled mode with PEEP (9 cm H2O; LPV group) ventilation. RESULTS: Patients in the LPV group showed significantly lower pH values (7.30 ± 0.07 vs. 7.38 ± 0.05, P< 0.001) and respiratory indexes than that of CV group (0.806 ± 0.339 vs. 0.919 ± 0.300, P= 0.043) at the end of surgery. Compared with the CV group, the dynamic lung compliance (33.39 ± 3.163 vs. 30.15 ± 2.572, P< 0.001) was significantly higher, and the body temperature remained significantly more favorable in the LPV group (35.9 ± 0.3 vs. 35.1 ± 0.4, P< 0.001). Patients in the LPV group had significantly faster postoperative recovery than that of the CV group (P< 0.001). CONCLUSIONS: The study showed that LPV could be beneficial for ventilation, core body temperature, and postoperative recovery in elderly patients with healthy lungs.

Interpretation and use of intraoperative protective ventilation parameters: a scoping review.

Thirty years ago, the traditional approach to mechanical ventilation consisted of the normalization of PaCO2 and pH at the expense of using a tidal volume (VT) of 10-15 mL kg-1. But then, the use of 6-8 mL kg-1 became a dogma for ventilating patients either with acute respiratory distress syndrome (ARDS) or without lung disease in the operating theatre. It is currently recognized that even low tidal volumes may be excessive for some patients and insufficient for others, depending on its distribution in the aerated lung parenchyma. To carry out intraoperative protective mechanical ventilation, medical literature has focused on positive end expiratory pressure (PEEP), plateau pressure (Paw plateau), and airway driving pressure (ΔPaw). However, considering its limitations, other parameters have emerged that represent a better reflection of isolated lung stress, such as transpulmonary pressure (PL) and transpulmonary driving pressure (ΔPL). These parameters are less generalized in clinical practice due to the requirement of an oeso-phageal balloon for their measurement and therefore their cumbersome application in the operating theatre. However, its study helps in the interpretation of the rest of the ventilator pressures to optimize intraoperative mechanical ventilation. This article defines and develops protective ventilation parameters, breaks down their determinants, mentions their limitations, and offers recommendations for their use intraoperatively.

Immediate changes in intra-abdominal pressure and lung indicators in patients undergoing complex ventral hernia repair with the transversus abdominis muscle release, with and without preoperative botulinum toxin.

PURPOSE: The current treatment of complex ventral hernias involves muscle closure with components separation techniques and mesh placement. The purpose of this study is to evaluate the immediate postoperative changes in the intra-abdominal pressure (IAP), and lung indicators after treatment of complex ventral hernias with the transversus abdominis reléase (TAR) technique. METHODS: All patients with complex ventral hernias treated between November 28th, 2016 and October 6th, 2021 were initially included. We excluded patients with lung and/or heart comorbidities. A total of 43 patients were studied, measuring IAP, lung compliance, pulmonary plateau pressure (PPP), and end-tidal CO2 before and after surgical treatment. RESULTS: Median IAP increased from 5 to 9 mmHg (p < 0.0001), and PPP from 11 to 12 mmHg (p = 0.004). Increased body mass index (BMI) was associated to a PPP increase above normal values. Postoperative changes were not different in patients receiving preoperative preparation with botulinum toxin. CONCLUSION: After complex ventral hernia closure, there is an immediate impact on IAP and PPP, the latter more frequent in patients with the highest BMI, and this may not be prevented by the preoperative administration of botulinum toxin.

Static and Dynamic Measurements of Compliance and Driving Pressure: A Pilot Study.

RATIONALE: Monitoring tidal cycle mechanics is key to lung protection. For this purpose, compliance and driving pressure of the respiratory system are often measured clinically using the plateau pressure, obtained after imposing an extended end-inspiratory pause, which allows for relaxation of the respiratory system and redistribution of inflation volume (method A). Alternative methods for estimating compliance and driving pressure utilize the measured pressure at the earliest instance of zero flow (method B), the inspiratory slope of the pressure-time tracing during inflation with constant flow (method C), and the expiratory time constant (method D). METHODS: Ten passive mechanically ventilated subjects, at a large tertiary referral center, underwent measurements of compliance and driving pressure using the four different methods. The inspiratory tidal volume, inspiratory to expiratory ratio, and positive end expiratory pressures were then adjusted from baseline and the measurements re-obtained. RESULTS: Method A yielded consistently higher compliance and lower driving pressure calculations compared to methods B and C. Methods B and C most closely approximated one another. Method D did not yield a consistent reliable pattern. CONCLUSION: Static measurements of compliance and driving pressure using the plateau pressure may underestimate the maximum pressure experienced by the most vulnerable lung units during dynamic inflation. Utilizing the pressure at zero flow as a static measurement, or the inspiratory slope as a dynamic measurement, may calculate a truer estimate of the maximum alveolar pressure that generates stress upon compromised lung units.

Reliability of plateau pressure during patient-triggered assisted ventilation. Analysis of a multicentre database.

PURPOSE: An inspiratory hold during patient-triggered assisted ventilation potentially allows to measure driving pressure and inspiratory effort. However, muscular activity can make this measurement unreliable. We aim to define the criteria for inspiratory holds reliability during patient-triggered breaths. MATERIAL AND METHODS: Flow, airway and esophageal pressure recordings during patient-triggered breaths from a multicentre observational study (BEARDS, NCT03447288) were evaluated by six independent raters, to determine plateau pressure readability. Features of "readable" and "unreadable" holds were compared. Muscle pressure estimate from the hold was validated against other measures of inspiratory effort. RESULTS: Ninety-two percent of the recordings were consistently judged as readable or unreadable by at least four raters. Plateau measurement showed a high consistency among raters. A short time from airway peak to plateau pressure and a stable and longer plateau characterized readable holds. Unreadable plateaus were associated with higher indexes of inspiratory effort. Muscular pressure computed from the hold showed a strong correlation with independent indexes of inspiratory effort. CONCLUSION: The definition of objective parameters of plateau reliability during assisted-breath provides the clinician with a tool to target a safer assisted-ventilation and to detect the presence of high inspiratory effort.

Aplicaciones e implicaciones de la pausa al final de la inspiración en ventilación mecánica / Applications and implications of end-inspiratory pause in mechanical ventilation / Aplicações e implicações da pausa ao final da inspiração na ventilação mecânica

Resumen: El uso de la pausa al final de la inspiración (PFI) en ventilación mecánica data de hace más de 50 años y con mayor impulso en la década de los 70, se le atribuye una mejoría en la presión parcial de oxígeno arterial (PaO2) al incrementar la presión media de la vía aérea (Pma), mayor aclaramiento de la presión parcial de dióxido de carbono arterial (PaCO2) y permite la monitorización de la presión meseta (Pmeseta) en la mecánica ventilatoria; sin embargo, los estudios clínicos sobre su uso son escasos y controversiales. En este artículo se abordan los mecanismos fisiológicos, fisiopatológicos y la evidencia sobre el uso de la PFI en ventilación mecánica (VM).

Abstract: The use of the end inspiratory pause (EIP) in mechanical ventilation has been going on for more than 50 years and with greater momentum in the 1970s, an improvement in the partial pressure of arterial oxygen (PaO2) is attributed to the increase mean airway pressure, greater clearance of partial pressure of arterial carbon dioxide and allows monitoring of plateau pressure in ventilatory mechanics; However, the Clinical studies on its use are few and controversial. This article addresses the physiological and pathophysiological mechanisms and the evidence on the use of EIP in mechanical ventilation.

Resumo: A utilização da pausa ao final da inspiração (PFI) na ventilação mecânica remonta a mais de 50 anos e com maior impulso na década de 70, atribui-se uma melhora na pressão parcial de oxigênio arterial (PaO2) pelo aumento da pressão média das vias aéreas (Pma), uma maior depuração da pressão parcial de dióxido de carbono arterial (PaCO2) e permite a monitorização da pressão de platô (Pplateau) na mecânica ventilatória, porém estudos Os dados clínicos sobre seu uso são escassos e controversos. Este artigo aborda os mecanismos fisiológicos e fisiopatológicos e as evidências sobre o uso do PFI na ventilação mecânica (VM).

Respiratory Pathophysiology of Mechanically Ventilated COVID-19 Patients.

Background and objectives Coronavirus disease 2019 (COVID-19) is mainly a disease of the respiratory system that can lead to acute respiratory distress syndrome (ARDS). The pathophysiology of COVID-19 ARDS and consequently its management is a disputable subject. Early COVID-19 investigators hypothesized that the pathogenesis of COVID-19 ARDS is different from the usual ARDS. The aim of this study was to describe the lung mechanics in mechanically ventilated COVID-19 patients with ARDS. Methodology An observational retrospective cohort study was conducted on adult COVID-19 patients with ARDS who needed mechanical ventilation in the ICU of Ohoud Hospital, Madinah, KSA, from June to September 2020. Data were collected from the patients' medical charts and electronic medical records and analyzed using Statistical Package for the Social Sciences (SPSS) software package version 22 (IBM Corp., Armonk, NY) for descriptive statistical analysis. Measurements and main results A total of 52 patients were analyzed: on intubation, the median positive end-expiratory pressure (PEEP) was 10 cm H2O (IQR, 2.3-16), the median plateau pressure was 27 cm H2O (IQR, 12-40), and the median driving pressure was 17 cm H2O (IQR, 3-30). The median static compliance of the respiratory system was 24.7 mL/cm H2O (IQR, 12.8-153.3). 59.5% had severe ARDS (the PaO2/FiO2 ratio was less than 100 mmHg), and 33% had moderate ARDS (the PaO2/FiO2 ratio ranged from 100 to 200 mmHg). Conclusion Our results suggest that the lung mechanics in COVID-19 ARDS patients who need mechanical ventilation do not differ from non-COVID-19 patients.

Evaluation of a novel endotracheal tube suctioning system incorporating an inflatable sweeper.

INTRODUCTION: Accumulation of secretions in an endotracheal tube can increase the resistance to flow resulting in an increased patient work of breathing when the patient is interacting with the ventilator. Retained secretions can also serve as an infection risk. Standard suction catheters are limited in their ability to keep the lumen of the endotracheal tube clear. A novel closed-suction catheter has been introduced that incorporates a balloon at its distal end that, when inflated, physically scrapes secretions out of the endotracheal tube (CleanSweep catheter (CSC), Teleflex, Morrisville NC). We hypothesized that the CSC would be more efficient at removing secretions from inside the endotracheal tube than a standard suction catheter (SSC). METHODS: We performed a bench study examining resistive pressures across different sizes of endotracheal tubes when cleaned by the CSC as compared with an SSC. This study was followed by a prospective crossover study again comparing the CSC with an SSC in intubated intensive care unit patients receiving mechanical ventilation and requiring frequent suctioning. RESULTS: For the bench study the CSC was significantly better in reducing airway resistive pressures (P < 0.001). In the prospective crossover study the CSC over 2 h also removed significantly more secretions than the SSC (P < 0.05). CONCLUSION: Both our bench and crossover clinical study demonstrated improved clearance of secretions with the CSC vs an SSC. Further research is needed to ascertain the clinical outcome benefits of enhanced secretion removal.

Do ventilatory parameters influence outcome in patients with severe acute respiratory infection? Secondary analysis of an international, multicentre14-day inception cohort study.

PURPOSE: To investigate the possible association between ventilatory settings on the first day of invasive mechanical ventilation (IMV) and mortality in patients admitted to the intensive care unit (ICU) with severe acute respiratory infection (SARI). MATERIALS AND METHODS: In this pre-planned sub-study of a prospective, multicentre observational study, 441 patients with SARI who received controlled IMV during the ICU stay were included in the analysis. RESULTS: ICU and hospital mortality rates were 23.1 and 28.1%, respectively. In multivariable analysis, tidal volume and respiratory rate on the first day of IMV were not associated with an increased risk of death; however, higher driving pressure (DP: odds ratio (OR) 1.05; 95% confidence interval (CI): 1.01-1.1, p = 0.011), plateau pressure (Pplat) (OR 1.08; 95% CI: 1.04-1.13, p < 0.001) and positive end-expiratory pressure (PEEP) (OR 1.13; 95% CI: 1.03-1.24, p = 0.006) were independently associated with in-hospital mortality. In subgroup analysis, in hypoxemic patients and in patients with acute respiratory distress syndrome (ARDS), higher DP, Pplat, and PEEP were associated with increased risk of in-hospital death. CONCLUSIONS: In patients with SARI receiving IMV, higher DP, Pplat and PEEP, and not tidal volume, were associated with a higher risk of in-hospital death, especially in those with hypoxemia or ARDS.

Evolution of practice patterns in the management of acute respiratory distress syndrome: A secondary analysis of two successive randomized controlled trials.

PURPOSE: We sought to examine changes in acute respiratory distress syndrome (ARDS) management over a 12-year period of two successive randomized trials. METHODS: Analyses included baseline data, from eligible patients, prior to influence of trial protocols, and daily study data, from randomized patients, of variables not determined by trial protocols. Mixed linear regressions examined changes in practice year-on-year. RESULTS: A total of 2376 patients met the inclusion criteria. Over the 12-year period, baseline tidal volume index decreased (9.0 to 7.0 ml/kg, p < 0.001), plateau pressures decreased (30.8 to 29.0 cmH2O, p < 0.05), and baseline positive end-expiratory pressures increased (10.8 to 13.2 cmH2O, p < 0.001). Volume-controlled ventilation declined from 29.4 to 14.0% (p < 0.01). Use of corticosteroids increased (baseline: 7.7 to 30.3%; on study: 32.6 to 61.2%; both p < 0.001), as did neuromuscular blockade (baseline: 12.3 to 24.5%; on study: 55.5 to 70.0%; both p < 0.01). Inhaled nitric oxide use increased (24.9 to 65.8%, p < 0.05). We observed no significant change in prone positioning (16.2 to 18.9%, p = 0.70). CONCLUSIONS: Clear trends were apparent in tidal volume, airway pressures, ventilator modes, adjuncts and rescue therapies. With the exception of prone positioning, and outside the context of rescue therapy, these trends appear consistent with the evolving literature on ARDS management.

The effect of driving pressures in COVID-19 ARDS: Lower may still be better as in classic ARDS.

BACKGROUND: The respiratory dynamics of coronavirus disease 2019 (COVID-19) patients under invasive ventilation are still not well known. In this prospective cohort, we aimed to assess the characteristics of the respiratory system in COVID-19 patients under invasive mechanical ventilation and evaluate their relationship with mortality. METHODS: Fifty-eight COVID-19 patients who underwent invasive mechanical ventilation between March 11, 2020 and September 1, 2020 were enrolled for the present study. Demographics and laboratory values at baseline were recorded. Respiratory variables such as tidal volume, plateau pressure, positive end expiratory pressure, static compliance, and driving pressure were recorded daily under passive conditions. Further, the median values were analyzed. RESULTS: Median age of the patients was 64 years (58-72). Mortality was 60% on day 28. Plateau pressure, driving pressure, and static compliance significantly differ between the survivors and non-survivors. When patients were categorized into two groups based on the median driving pressure (Pdrive) of ≤15 cmH2O or >15 cmH2O during their invasive mechanical ventilation period, there was significantly better survival on day 28 in patients having a Pdrive ≤ 15 cmH2O [28 days (95% CI = 19-28) vs 16 days (95% CI = 6-25), (log-rank p = 0.026). CONCLUSION: COVID-19 related acute respiratory distress syndrome (ARDS) seemed to have similar characteristics as other forms of ARDS. Lung protective ventilation with low plateau and driving pressures might be related to lower mortality.

Product of driving pressure and respiratory rate for predicting weaning outcomes.

OBJECTIVE: Clinicians cannot precisely determine the time for withdrawal of ventilation. We aimed to evaluate the performance of driving pressure (DP)×respiratory rate (RR) to predict the outcome of weaning. METHODS: Plateau pressure (Pplat) and total positive end-expiratory pressure (PEEPtot) were measured during mechanical ventilation with brief deep sedation and on volume-controlled mechanical ventilation with a tidal volume of 6 mL/kg and a PEEP of 0 cmH2O. Pplat and PEEPtot were measured by patients holding their breath for 2 s after inhalation and exhalation, respectively. DP was determined as Pplat minus PEEPtot. The rapid shallow breathing index was measured from the ventilator. The highest RR was recorded within 3 minutes during a spontaneous breathing trial. Patients who tolerated a spontaneous breathing trial for 1 hour were extubated. RESULTS: Among the 105 patients studied, 44 failed weaning. During ventilation withdrawal, DP×RR was 136.7±35.2 cmH2O breaths/minute in the success group and 230.2±52.2 cmH2O breaths/minute in the failure group. A DP×RR index >170.8 cmH2O breaths/minute had a sensitivity of 93.2% and specificity of 88.5% to predict failure of weaning. CONCLUSIONS: Measurement of DP×RR during withdrawal of ventilation may help predict the weaning outcome. A high DP×RR increases the likelihood of weaning failure.Statement: This manuscript was previously posted as a preprint on Research Square with the following link: https://www.researchsquare.com/article/rs-15065/v3 and DOI: 10.21203/rs.2.24506/v3.

The influence of Transversus Abdominis Muscle Release (TAR) for complex incisional hernia repair on the intraabdominal pressure and pulmonary function.

INTRODUCTION: Among many other techniques for Abdominal Wall Reconstruction (AWR), posterior component separation with Transversus Abdominis Release (TAR), continues to gain popularity and it is increasingly used with promising long-term results. Our goal was to evaluate the influence of TAR with mesh retromuscular reinforcement on the intra-abdominal pressure (IAP) and respiratory function in a series of patients with complex incisional hernias (IH). METHODS: Since November 2014 through February 2019, patients with TAR were identified in the Clinical Department of Surgery database and were retrospectively reviewed. Outcome measures include: demographics, pre- and perioperative details, preoperative and postoperative IAP and plateau pressure (PP). RESULTS: One-hundred-and-one consecutive TAR procedures (19.7% from all incisional hernia repairs) were analyzed. Mean age was 63 years with a mean Body Mass Index (BMI) of 31.85 kg/m2 (25-51). Diabetes and Chronic Obstructive Pulmonary Disease (COPD) were the main major comorbidities. Mean hernia defect area was 247 cm2 (104-528 cm2). CONCLUSION: TAR is a safe and sound procedure with acceptable modifications of the IAP morbidity and recurrence rate when correctly performed on the right patient.

Static compliance of the respiratory system in COVID-19 related ARDS: an international multicenter study.

BACKGROUND: Controversies exist on the nature of COVID-19 related acute respiratory distress syndrome (ARDS) in particular on the static compliance of the respiratory system (Crs). We aimed to analyze the association of Crs with outcome in COVID-19-associated ARDS, to ascertain its determinants and to describe its evolution at day-14. METHODS: In this observational multicenter cohort of patients with moderate to severe Covid-19 ARDS, Crs was measured at day-1 and day-14. Association between Crs or Crs/ideal body weight (IBW) and breathing without assistance at day-28 was analyzed with multivariable logistic regression. Determinants were ascertained by multivariable linear regression. Day-14 Crs was compared to day-1 Crs with paired t-test in patients still under controlled mechanical ventilation. RESULTS: The mean Crs in 372 patients was 37.6 ± 13 mL/cmH2O, similar to as in ARDS of other causes. Multivariate linear regression identified chronic hypertension, low PaO2/FiO2 ratio, low PEEP, and low tidal volume as associated with lower Crs/IBW. After adjustment on confounders, nor Crs [OR 1.0 (CI 95% 0.98-1.02)] neither Crs/IBW [OR 0.63 (CI 95% 0.13-3.1)] were associated with the chance of breathing without assistance at day-28 whereas plateau pressure was [OR 0.93 (CI 95% 0.88-0.99)]. In a subset of 108 patients, day-14 Crs decreased compared to day-1 Crs (31.2 ± 14.4 mL/cmH2O vs 37.8 ± 11.4 mL/cmH2O, p < 0.001). The decrease in Crs was not associated with day-28 outcome. CONCLUSION: In a large multicenter cohort of moderate to severe COVID-19 ARDS, mean Crs was decreased below 40 mL/cmH2O and was not associated with day-28 outcome. Crs decreased between day-1 and day-14 but the decrease was not associated with day-28 outcome.

Optimal Upper Limits of Plateau Pressure for Patients With Acute Respiratory Distress Syndrome During the First Seven Days: A Meta-Regression Analysis.

BACKGROUND: The effects of plateau pressure during the initial days of mechanical ventilation on outcomes for patients with acute respiratory distress syndrome have not been fully examined. We conducted meta-regression analysis of plateau pressure during the first 7 days using randomized control trials to investigate the optimal upper limits of plateau pressure on different days of mechanical ventilation. METHODS: Randomized controlled trials comparing two mechanical ventilation strategies with lower and higher plateau pressures in patients with acute respiratory distress syndrome were included. Meta-regression analysis was performed to determine the association of plateau pressure with mortality on days 1, 3, and 7 of mechanical ventilation. RESULTS: After evaluation of 2,975 citations from a comprehensive search across electronic databases, 14 studies were included in the final qualitative analysis. A total of 4,984 patients were included in the quantitative analysis. As a result of the pairwise comparison, overall short-term mortality was significantly higher for patients with plateau pressures over 32 cm H2O during the first 3 days after intensive care unit (ICU) admission (day 1: relative risk (RR), 0.77; 95% confidence interval (CI), 0.66 - 0.89; I2 = 0%; day 3: RR, 0.76; 95% CI, 0.64 - 0.90; I2 = 0%), but not on day 7 (RR, 0.82; 95% CI, 0.65 - 1.04; I2 = 16%). Plateau pressures below 27 cm H2O and 30 cm H2O were not associated with an absolute risk reduction of short-term mortality. According to univariable meta-regression analysis, mortality was significantly associated with plateau pressure on day 1 (ß = 0.01 (95% CI, 0.002 - 0.024), P = 0.02). On days 3 and 7, however, no significant difference was detected. When the cutoffs were set at 27, 30 and 32 cm H2O on day 1, which showed a significant difference, plateau pressure tended to be associated with increased mortality at pressures above the cut-off values, and there were no significant differences at pressures below the cut-off values, regardless of the cutoff used. CONCLUSIONS: This study suggests that the optimal cut-off value for plateau pressure may be 27 cm H2O especially during the initial period of mechanical ventilation, although this association may not continue during the latter period of mechanical ventilation.

The Nature of Recruitment and De-Recruitment and Its Implications for Management of ARDS.

Recruitment maneuvers in ARDS are used to improve oxygenation and lung mechanics by applying high airway pressures to reopen collapsed or obstructed peripheral airways and alveoli. In the early 1990s, recruitment maneuvers became a central feature of a variant form of lung-protective ventilation known as open-lung ventilation. This strategy is based on the belief that repetitive opening and closing of distal airspaces induces shear injury and therefore contributes both to ventilator-induced lung injury and ARDS-associated mortality. However, the largest multi-center randomized controlled trial of open-lung ventilation in moderate to severe ARDS reported that recruitment maneuver plateau pressures of 50-60 cm H2O were associated with significantly higher mortality compared to traditional lung-protective ventilation. Despite being based on well conducted preclinical and clinical recruitment maneuver studies, the higher mortality associated with the open-lung ventilation strategy requires re-examining the assumptions and conclusions drawn from those previous studies. This narrative review examines the evidence used to design recruitment maneuver strategies. We also review the radiologic, rheologic, and histopathologic evidence regarding the nature of lung injury and the phenomena of recruitment and de-recruitment as it informs our perceptions of recruitment potential in ARDS. Major lung-protective ventilation clinical trial data and other clinical data are also examined to assess the practical necessity of recruitment maneuvers in ARDS and whether a subset of cases might benefit from pursuing recruitment maneuver therapy. Finally, a less a radical approach to recruitment maneuvers is offered that might achieve the goals of recruitment maneuvers with less risk of harm.

The Association Between the Mechanical Ventilator Pressures and Outcomes in a Cohort of Patients with Acute Respiratory Failure.

BACKGROUND: Pressures measured during mechanical ventilation provide important information about the respiratory system mechanics and can help predict outcomes. METHODS: The electronic medical records of patients hospitalized between 2010 and 2016 with sepsis who required mechanical ventilation were reviewed to collect demographic information, clinical information, management requirements, and outcomes, such as mortality, ICU length of stay, and hospital length of stay. Mechanical ventilation pressures were recorded on the second full day of hospitalization. RESULTS: This study included 312 adult patients. The mean age is 59.1 ± 16.3 years; 57.4% were men. The mean BMI was 29.3 ± 10.7. Some patients had pulmonary infections (46.2%), and some patients had extrapulmonary infections (34.9%). The overall mortality was 42.6%. In a multi-variable model that included age, gender, number of comorbidities, APACHE 2 score, and PaO2/FiO2 ratio, peak pressure, plateau pressure, driving pressure, and PEEP all predicted mortality when entered into the model separately. There was an increase in peak pressure, plateau pressure, and driving pressure across BMI categories ranging from underweight to obese. CONCLUSIONS: This study demonstrates that ventilator pressure measurements made early during the management of patients with acute respiratory failure requiring mechanical ventilation provide prognostic information regarding outcomes, including mortality. Patients with high mechanical ventilator pressures during the early course of their acute respiratory failure require more attention to identify reversible disease processes when possible. In addition, increased BMIs are associated with increased ventilator pressures, and this increases the complexity of the clinical evaluation in the management of obese patients.

Respiratory Mechanics and Outcomes in Immunocompromised Patients With ARDS: A Secondary Analysis of the EFRAIM Study.

BACKGROUND: In view of the high mortality rate of immunocompromised patients with ARDS, it is important to identify targets for improvement. RESEARCH QUESTION: This study investigated factors associated with mortality in this specific ARDS population, including factors related to respiratory mechanics (plateau pressure [Pplat,rs], compliance [Crs], and driving pressure [ΔPrs]). STUDY DESIGN AND METHODS: This study consisted of a predefined secondary analysis of the EFRAIM data. Overall, 789 of 1,611 patients met the Berlin criteria for ARDS, and Pplat,rs, ΔPrs, and Crs were available for 494 patients. A hierarchical model was used to assess factors at ARDS onset independently associated with hospital mortality. RESULTS: Hospital mortality was 56.3%. After adjustment, variables independently associated with hospital mortality included ARDS of undetermined etiology (OR, 1.66; 95% CI, 1.01-2.72), need for vasopressors (OR, 1.91; 95% CI, 1.27-2.88), and need for renal replacement therapy (OR, 2.02; 95% CI, 1.37-2.97). ARDS severity according to the Berlin definition, neutropenia on admission, and the type of underlying disease were not significantly associated with mortality. Before adjustment, higher Pplat,rs, higher ΔPrs, and lower Crs were associated with higher mortality. Addition of each of these individual variables to the final hierarchical model revealed a significant association with mortality: ΔPrs (OR, 1.08; 95% CI, 1.05-1.12), Pplat,rs (OR, 1.07; 95% CI, 1.04-1.11), and Crs (OR, 0.97; 95% CI, 0.95-0.98). Tidal volume was not associated with mortality. INTERPRETATION: In immunocompromised patients with ARDS, respiratory mechanics provide additional prognostic information to predictors of hospital mortality. Studies designed to define lung-protective ventilation guided by these physiological variables may be warranted in this specific population.