Conventional mechanical ventilation can injury intact lungs in severe trauma patients

Introduction

Conventional mechanical ventilation (MV) may cause additional lung injury in ALI/ARDS due to overdistention of aerated lung regions (high Vt) and cyclic lung reopening (low PEEP level). Hyperproduction of inflammatory mediators is one of the side effects in these cases. This factor could delay or prevent resolution of respiratory failure [1, 2]. However, it is not clear whether conventional mechanical ventilation damages intact lungs. The aim of this study was to evaluate the effects of conventional and protective mechanical ventilation on intact lungs in patients with severe trauma.

Methods

A prospective, randomized controlled trial in trauma patients with mechanical ventilation for extrapulmonary indications. The protocol was approved by the local ethics committee. Seventy-eight patients were randomized to conventional (Vt 10 to 12 ml/kg IBW, PEEP 5 cmH₂O - n = 39) or protective (Vt 5 to 6 ml/kg IBW, PEEP 10 cmH₂O - n = 39) mechanical ventilation. TNFα, IL-1β and IL-6 levels in plasma and BAL fluids were measured on 1, 2, 3, 5 and 7 days of MV. Frequency of ALI (AECC criteria) and VAP were evaluated. The endpoints of this study were the length of MV, LOS in ICU and outcome on 28 days.

Results

In first 3 days ALI was revealed in 26 patients (66.6%) in the conventional and 10 patients (26.5%) in the protective MV groups (P = 0.001; OR 4.375, 95% CI 2.227 to 8.189). ARDS occurred in four patients (10,2%) of the conventional MV group (LIS >2) and no one in the protective MV group (P < 0.0001). Levels of TNFα, IL-1β and IL-6 in BAL fluids were significantly higher in the conventional MV group from 1 to 7 days with maximal increase on day 3 (542 ± 44/91 ± 11; 315 ± 35/86 ± 10; 1,092 ± 160/111 ± 18, P < 0.0001). No differences were found in levels of TNFα, IL-1β and IL-6 in plasma samples. VAP occurred in 31 patients (83.7%) of the conventional and nine patients (23%) of the protective MV groups (P = 0.0001; OR 17.2, 95% CI 5.5 to 54.3). The length of MV was 17.4 ± 6 vs 12.8 ± 3 (P = 0.0001; OR 4.2, 95% CI 1.5 to 11.5), LOS in the ICU was 21.9 ± 5.6 vs 15.75 ± 2.9 (P = 0.0002; OR 2.0, 95% CI 0.18 to 23.6). The 28-day mortality was not significantly different in the groups.

Conclusions

Conventional MV for more than 72 hours in patients with severe trauma and intact lungs can cause lung injury, and increase duration of MV and LOS in the ICU.