Effect of mechanical power on intensive care mortality in ARDS patients

Abstract

Background: In ARDS patients, mechanical ventilation should minimize ventilator-induced lung injury. The mechanical power which is the energy per unit time released to the respiratory system according to the applied tidal volume, PEEP, respiratory rate, and flow should reflect the ventilator-induced lung injury. However, similar levels of mechanical power applied in different lung sizes could be associated to different effects. The aim of this study was to assess the role both of the mechanical power and of the transpulmonary mechanical power, normalized to predicted body weight, respiratory system compliance, lung volume, and amount of aerated tissue on intensive care mortality. Methods: Retrospective analysis of ARDS patients previously enrolled in seven published studies. All patients were sedated, paralyzed, and mechanically ventilated. After 20 min from a recruitment maneuver, partitioned respiratory mechanics measurements and blood gas analyses were performed with a PEEP of 5 cmH 2 O while the remaining setting was maintained unchanged from the baseline. A whole lung CT scan at 5 cmH 2 O of PEEP was performed to estimate the lung gas volume and the amount of well-inflated tissue. Univariate and multivariable Poisson regression models with robust standard error were used to calculate risk ratios and 95% confidence intervals of ICU mortality. Results: Two hundred twenty-two ARDS patients were included; 88 (40%) died in ICU. Mechanical power was not different between survivors and non-survivors 14.97 [11.51-18.44] vs. 15.46 [12.33-21.45] J/min and did not affect intensive care mortality. The multivariable robust regression models showed that the mechanical power normalized to well-inflated tissue (RR 2.69 [95% CI 1.10-6.56], p = 0.029) and the mechanical power normalized to respiratory system compliance (RR 1.79 [95% CI 1.16-2.76], p = 0.008) were independently associated with intensive care mortality after adjusting for age, SAPS II, and ARDS severity. Also, transpulmonary mechanical power normalized to respiratory system compliance and to well-inflated tissue significantly increased intensive care mortality (RR 1.74 [1.11-2.70], p = 0.015; RR 3.01 [1.15-7.91], p = 0.025).

Body mass index and acute respiratory distress severity in patients with and without SARS-CoV-2 infection

“…We compared C-ARDS patients with 247 consecutive ‘other ARDS’ patients enrolled in previous and ongoing studies (NCT03920189). 8 The Institutional Ethics Board of ASST Santi Paolo e Carlo, San Paolo University Hospital, Milan, Italy approved the study, and the Institutional Ethics Board of Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milan, Italy approved this study for Maggiore Hospital, Lodi, Italy. The datasets used, analysed, or both during the current study are available from the corresponding author upon reasonable request.…”

Mechanical Power During Extracorporeal Membrane Oxygenation and Hospital Mortality in Patients With Acute Respiratory Distress Syndrome

“…Zhang et al reported that MP normalized to PBW was far more accurate than the absolute value of MP in predicting mortality [6]. Coppola et al reported no causal relationship between MP alone and mortality, whereas both MP and transpulmonary MP normalized to respiratory system compliance or to the amount of well-aerated tissue were independently associated with ICU mortality [7]. However, the above studies were predicated on baseline MP values, they did not account for serial changes in MP during the ICU stay and did not seek to determine whether the link between MP and mortality was independent from other ventilator settings.…”

“…This indicated that those patients were not fully sedated and paralyzed, and neuromuscular blocking agents were used in only 41 % of cases [15]. In estimating MP values, patients should be completely relaxed; i.e., without any active inspiratory efforts [7]. In our study, the median spontaneous RR before ECMO was 0 (0-7) breaths/minute and 1 (0-4) breath/minute during the rst 3 days of ECMO, indicating that our patients were nearly total sedated and paralyzed.…”

“…VILI originates from the interaction between the energy load (i.e., MP) and the pathophysiological characteristics of the lungs (size, homogeneity and recruitability) [4,5]. Therefore, the same MP may have different impact on respiratory system depending on the applied conditions of lungs, and MP should be normalized at least to the functional lung size in order to accurately re ect the actual amount of energy applied to the lungs [6,7].…”

“…However, MP alone does not have better predictive value for patients with ARDS, and it is preferable to normalize MP to predicted body weight (PBW) [6] or respiratory system compliance in terms of wellaerated tissue [7].…”