Acute Respiratory Distress Syndrome Caused by Pulmonary and Extrapulmonary Disease

TLDR

The study aimed to compare respiratory mechanics in ARDS arising from pulmonary versus extrapulmonary disease. They measured total respiratory system, chest wall, and lung elastance, intra‑abdominal pressure, and end‑expiratory lung volume at 0, 5, 10, and 15 cm H₂O PEEP in 12 pulmonary‑ARDS and 9 extrapulmonary‑ARDS patients. At zero PEEP, total system elastance and EELV were similar, but lung elastance was higher in pulmonary‑ARDS and chest‑wall elastance and intra‑abdominal pressure were higher in extrapulmonary‑ARDS; increasing PEEP to 15 cm H₂O raised system elastance in pulmonary‑ARDS and lowered it in extrapulmonary‑ARDS, with recruitment favoring extrapulmonary‑ARDS, reflecting consolidation in pulmonary‑ARDS versus edema and collapse in extrapulmonary‑ARDS.

Abstract

To assess the possible differences in respiratory mechanics between the acute respiratory distress syndrome (ARDS) originating from pulmonary disease (ARDSp) and that originating from extrapulmonary disease (ARDSexp) we measured the total respiratory system (Est,rs), chest wall (Est,w) and lung (Est,L) elastance, the intra-abdominal pressure (IAP), and the end-expiratory lung volume (EELV) at 0, 5, 10, and 15 cm H2O positive end-expiratory pressure (PEEP) in 12 patients with ARDSp and nine with ARDSexp. At zero end-expiratory pressure (ZEEP), Est,rs and EELV were similar in both groups of patients. The Est,L, however, was markedly higher in the ARDSp group than in the ARDSexp group (20.2 ± 5.4 versus 13.8 ± 5.0 cm H2O/L, p < 0.05), whereas Est,w was abnormally increased in the ARDSexp group (12.1 ± 3.8 versus 5.2 ± 1.9 cm H2O/L, p < 0.05). The IAP was higher in ARDSexp than in ARDSp (22.2 ± 6.0 versus 8.5 ± 2.9 cm H2O, p < 0.01), and it significantly correlated with Est,w (p < 0.01). Increasing PEEP to 15 cm H2O caused an increase of Est,rs in ARDSp (from 25.4 ± 6.2 to 31.2 ± 11.3 cm H2O/L, p < 0.01) and a decrease in ARDSexp (from 25.9 ± 5.4 to 21.4 ± 55.5 cm H2O/L, p < 0.01). The estimated recruitment at 15 cm H2O PEEP was − 0.031 ± 0.092 versus 0.293 ± 0.241 L in ARDSp and ARDSexp, respectively (p < 0.01). The different respiratory mechanics and response to PEEP observed are consistent with a prevalence of consolidation in ARDSp as opposed to prevalent edema and alveolar collapse in ARDSexp.