Lack of Benefit of Heliox During Mechanical Ventilation of Subjects With Severe Air-Flow Obstruction.

BACKGROUND: The value of heliox (helium-oxygen mixture) for patients with severe air-flow obstruction is uncertain. The purpose of this study was to determine whether heliox could reduce the degree of hyperinflation and hypercapnia in mechanically ventilated patients with severe air-flow obstruction.

METHODS: This was a single-center, prospective observational study conducted in a medical ICU of an academic medical center. We assessed the impact of heliox (65-70% helium, 30-35% oxygen) on airway pressures and arterial blood gases of 13 subjects undergoing mechanical ventilation for severe asthma ( n = 8) or exacerbation of COPD ( n = 5).

RESULTS: As compared with ventilation with air-O2 , heliox resulted in a reduction in peak airway pressure (54.1 ± 12.6 cm H2 O vs 47.9 ± 10.8 cm H2 O, P < .001) and PaCO2 (64.3 ± 14.9 mm Hg vs 62.3 + 15.1 mm Hg, P = .01). In contrast, there was no change in plateau pressure (25.3 ± 5.5 cm H2 O vs 25.8 ± 5.6 cm H2 O, P = .14) or total PEEP (13.4 ± 3.8 cm H2 O vs 13.3 ± 4.1 cm H2 O, P = .79) in response to heliox.

CONCLUSIONS: In mechanically ventilated subjects with severe air-flow obstruction, administration of heliox had no effect on indices of dynamic hyperinflation (plateau pressure and total PEEP) and resulted in only a small reduction in PaCO2 .