Beneficial effects of helium : oxygen versus air : oxygen noninvasive pressure support in patients with decompensated chronic obstructive pulmonary disease

Objective: To test the hypothesis that, in decompensated chronic obstructiv e pulmonary disease (COPD), noninvasive pressure support ventilation using 70:30 helium:oxygen instead of 70:30 air:oxygen could reduce dyspnea and im prove ventilatory variables, gas exchange, and hemodynamic tolerance. Design: Prospective, randomized, crossover study. Setting: Medical intensive care unit, university tertiary care center. Patients: Nineteen patients with severe COPD (forced 1-sec expiratory volum e of 0.83 +/- 0.3 I) hospitalized in the intensive care unit for noninvasiv e pressure support ventilation after initial stabilization with noninvasive pressure support for no more than 24 hrs after intensive care unit admissi on. Interventions: Noninvasive pressure support ventilation was administered in the following randomized crossover design: a) 45 min with air:oxygen or he lium:oxygen; b) no ventilation for 45 min; and c) 45 min with air:oxygen or helium:oxygen. Measurements and Main Results: Air:oxygen and helium:oxygen decreased respi ratory rate and increased tidal volume and minute ventilation. Helium:oxyge n decreased inspiratory time. Both gases increased total respiratory cycle time and decreased the inspiratory/total time ratio, the reduction in the l atter being significantly greater with helium:oxygen. Peak inspiratory flow rate increased more with helium:oxygen. PaO2 increased with both gases, wh ereas Pace, decreased more with helium:oxygen (values shown are mean +/- SD ) (52 +/- 6 torr [6.9 +/- 0.8 kPa] vs. 55 +/- 8 torr [7.3 +/- 1.1 kPa] and 48 +/- 6 torr [6.4 +/- 0.8 kPa] vs. 54 +/- 7 torr [7.2 +/- 0.9 kPa] for air :oxygen and helium:oxygen, respectively; p < .05). When hypercapnia was sev ere (PaCO2 > 56 torr [7.5 kPa]), Pace, decreased by greater than or equal t o 7.5 torr (1 kPa) in six of seven patients with helium:oxygen and in four of seven patients with air:oxygen (p < .01). Dyspnea score (Borg scale) dec reased more with helium:oxygen than with air:oxygen (3.7 +/- 1.6 vs. 4.5 +/ - 1.4 and 2.8 +/-1.6 vs. 4.6 +/- 1.5 for air:oxygen and helium:oxygen, resp ectively; p < .05). Mean arterial blood pressure decreased with air:oxygen (76 +/- 12 vs. 82 +/- 14 mm Hg; p < .05) but remained unchanged with helium :oxygen. Conclusion: In decompensated COPD patients, noninvasive pressure support ve ntilation with helium:oxygen reduced dyspnea and Pace, more than air:oxygen , modified respiratory cycle times, and did not modify systemic blood press ure. These effects could prove beneficial in COPD patients with severe acut e respiratory failure and might reduce the need far endotracheal intubation .