Sigh in Acute Respiratory Distress Syndrome

TLDR

Mechanical ventilation using plateau pressures below 35 cm H₂O and high PEEP is recommended as a lung‑protective strategy for ARDS. In a 4‑hour protocol, ten ARDS patients received 2 h of lung‑protective ventilation, 1 h of the same strategy with three sighs per minute at 45 cm H₂O, and a final 1 h of lung‑protective ventilation, while minute ventilation, PEEP, FiO₂, and mean airway pressure were held constant. Sighs markedly improved oxygenation (PaO₂ rose from 92.8 ± 18.6 to 137.6 ± 23.9 mm Hg), reduced venous admixture and PaCO₂, increased end‑expiratory lung volume (correlated with oxygenation and elastance), were more effective in extrapulmonary ARDS, and all gains reversed after sigh interruption, indicating that sighs enhance recruitment and oxygenation beyond the lung‑protective strategy alone.

Abstract

Mechanical ventilation with plateau pressure lower than 35 cm H2O and high positive end-expiratory pressure (PEEP) has been recommended as lung protective strategy. Ten patients with ARDS (five from pulmonary [p] and five from extrapulmonary [exp] origin), underwent 2 h of lung protective strategy, 1 h of lung protective strategy with three consecutive sighs/min at 45 cm H2O plateau pressure, and 1 h of lung protective strategy. Total minute ventilation, PEEP (14.0 ± 2.2 cm H2O), inspiratory oxygen fraction, and mean airway pressure were kept constant. After 1 h of sigh we found that: (1) PaO2 increased (from 92.8 ± 18.6 to 137.6 ± 23.9 mm Hg, p < 0.01), venous admixture and PaCO2 decreased (from 38 ± 12 to 28 ± 14%, p < 0.01; and from 52.7 ± 19.4 to 49.1 ± 18.4 mm Hg, p < 0.05, respectively); (2) end-expiratory lung volume increased (from 1.49 ± 0.58 to 1.91 ± 0.67 L, p < 0.01), and was significantly correlated with the oxygenation (r = 0.82, p < 0.01) and lung elastance (r = 0.76, p < 0.01) improvement. Sigh was more effective in ARDSexp than in ARDSp. After 1 h of sigh interruption, all the physiologic variables returned to baseline. The derecruitment was correlated with PaCO2 (r = 0.86, p < 0.01). We conclude that: (1) lung protective strategy alone at the PEEP level used in this study may not provide full lung recruitment and best oxygenation; (2) application of sigh during lung protective strategy may improve recruitment and oxygenation.