Helium/oxygen mixture reduces the work of breathing at the end of the weaning process in patients with severe chronic obstructive pulmonary disease

Abstract

Objective: To test the hypothesis that helium/oxygen mixture can reduce the work of breathing at the end of the weaning process in patients with chronic obstructive pulmonary disease.

Design: Prospective, randomized, crossover study.

Setting: Two medical intensive care units at two university tertiary care centers.

Patients: Thirteen patients with chronic obstructive pulmonary disease evaluated just before and after extubation.

Interventions: Helium/oxygen and air/oxygen mixtures were administered sequentially, for 20 mins each, in a randomized order, just before extubation. It was possible to repeat the study after extubation in five patients.

Measurements and main results: Before extubation, the helium/oxygen mixture induced no significant variation in the breathing pattern. By contrast, it reduced the work of breathing from 1.442 +/- 0.718 J/L (mean +/- sd) to 1.133 +/- 0.500 J/L (p <.05). This reduction was explained mainly by a reduction in the resistive component of the work of breathing from 0.662 +/- 0.376 to 0.459 +/- 0.256 J/L (p <.01). We also observed a slight reduction in the intrinsic positive end-expiratory pressure from 2.9 +/- 2.1 cm H(2)O to 2.1 +/- 1.8 cm H(2)O (p <.05). Similar results were also observed after extubation in five patients in whom the repetition of the study was possible.

Conclusions: In spontaneously breathing intubated patients with chronic obstructive pulmonary disease recovering from an acute exacerbation, helium/oxygen mixture reduces the work of breathing as well as intrinsic positive end-expiratory pressure without modifying the breathing pattern.