Study objectives: To examine clinicians' approaches to mechanical ventilati
on in patients with acute lung injury (ALI; Pao(2)/fraction of inspired oxy
gen [FIO2] less than or equal to 300) and compare ventilator settings in pa
tients with ARDS (Pao(2)/FIO2 less than or equal to 200) to settings in pat
ients with milder oxygenation impairment (Pao(2)/FIO2 of 201 to 300).
Design: Retrospective analysis of baseline data from prospective randomized
trials conducted by the National Institutes of Health ARDS Network between
1996 and 1999.
Setting: Ten clinical centers comprising 24 hospitals and 74 medical and su
rgical ICUs of the ARDS Network.
Measurements and results: The most common mode of mechanical ventilation in
both groups was volume-assist control (56%). Synchronized intermittent man
datory ventilation (SIMV) or SIMV with pressure support was used more often
in patients with Pao(2)/FIO2 of 201 to 300 than in patients with ARDS. The
use of pressure-control ventilation was uncommon (10% overall), as was the
use of permissive hypercapnia (6% of patients with ARDS and 3% of patients
with Pao(2)/FIO2 of 201 to 300). The mean +/- SD tidal volume was 10.3 +/-
2 mL/kg of predicted body weight or 8.6 +/- 2 mL/kg of measured weight for
patients with ARDS, and was not significantly different for patients with
Pao(2)/FIO2 of 201 to 300. Plateau pressures (Pplats) were lower in the Pao
(2)/FIO2 of 201 to 300 group (27 +/- 7 vs 31 +/- 8 for the ARDS group; p =
0.0003) and were > 35 cm H2O in 26% of patients. Seventy-eight percent of p
atients with ARDS received less than or equal to 10 cm H2O of positive end-
expiratory pressure.
Conclusions: Physicians in ARDS Network centers caring for patients early i
n the course of ALI/ARDS used volume-targeted ventilation and selected tida
l volumes that resulted in Pplats generally < 35 cm H2O. The average tidal
volume was similar for patients with ARDS vs those with milder oxygenation
deficits.