Feasibility and safety of ultra-low tidal volume ventilation without extracorporeal circulation in moderately severe and severe ARDS patients.

Abstract

Mechanical ventilation with ultra-low tidal volume (VT) during ARDS may reduce alveolar strain, driving pressure and hence ventilator-induced lung injury, with the main drawback of worsening respiratory acidosis. We hypothesized that VT could be reduced down to 4 ml/kg, with clinically significant decrease in driving pressure, without the need for extracorporeal CO₂ removal, while maintaining pH > 7.20. We conducted a non-experimental before-and-after multicenter study on 35 ARDS patients with PaO₂/FiO₂ ≤ 150 mmHg, within 24 h of ARDS diagnosis. After inclusion, VT was reduced to 4 ml/kg and further adjusted to maintain pH ≥ 7.20, respiratory rate was increased up to 40 min^-1 and PEEP was set using a PEEP-FiO₂ table. The primary judgment criterion was driving pressure on day 2 of the study, as compared to inclusion. From inclusion to day 2, driving pressure decreased significantly from 12 [9-15]  to 8 [6-11] cmH₂O, while VT decreased from 6.0 [5.9-6.1] to 4.1 [4.0-4.7] ml/kg. On day 2, VT was below 4.2 ml/kg in 65% [CI_95% 48%-79%], and below 5.25 ml/kg in 88% [CI_95% 74%-95%] of the patients. 2 patients (6%) developed acute cor pulmonale after inclusion. Eleven patients (32%) developed transient severe acidosis with pH < 7.15. Fourteen patients (41%) died before day 90. Ultra-low tidal volume ventilation may be applied in approximately 2/3 of moderately severe-to-severe ARDS patients, with a 4 cmH₂O median reduction in driving pressure, at the price of transient episodes of severe acidosis in approximately 1/3 of the patients.