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

ABSTRACT

OBJECTIVE: To test the hypothesis that, in decompensated chronic obstructive pulmonary disease (COPD), noninvasive pressure support ventilation using 7030 heliumoxygen instead of 7030 airoxygen could reduce dyspnea and improve 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 volume of 0.83+/-0.3 l) hospitalized in the intensive care unit for noninvasive pressure support ventilation after initial stabilization with noninvasive pressure support for no more than 24 hrs after intensive care unit admission. INTERVENTIONS: Noninvasive pressure support ventilation was administered in the following randomized crossover design: a) 45 min with airoxygen or heliumoxygen; b) no ventilation for 45 min; and c) 45 min with airoxygen or heliumoxygen. MEASUREMENTS AND MAIN RESULTS: Airoxygen and heliumoxygen decreased respiratory rate and increased tidal volume and minute ventilation. Heliumoxygen decreased inspiratory time. Both gases increased total respiratory cycle time and decreased the inspiratory/total time ratio, the reduction in the latter being significantly greater with heliumoxygen. Peak inspiratory flow rate increased more with heliumoxygen. PaO2 increased with both gases, whereas PaCO2 decreased more with heliumoxygen (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 airoxygen and heliumoxygen, respectively; p<.05). When hypercapnia was severe (PaCO2 >56 torr [7.5 kPa]), PaCO2 decreased by > or =7.5 torr (1 kPa) in six of seven patients with heliumoxygen and in four of seven patients with airoxygen (p<.01). Dyspnea score (Borg scale) decreased more with heliumoxygen than with airoxygen (3.7+/-1.6 vs. 4.5+/-1.4 and 2.8+/-1.6 vs. 4.6+/-1.5 for airoxygen and heliumoxygen, respectively; p<.05). Mean arterial blood pressure decreased with airoxygen (76+/-12 vs. 82+/-14 mm Hg; p<.05) but remained unchanged with heliumoxygen. CONCLUSION: In decompensated COPD patients, noninvasive pressure support ventilation with heliumoxygen reduced dyspnea and PaCO2 more than airoxygen, modified respiratory cycle times, and did not modify systemic blood pressure. These effects could prove beneficial in COPD patients with severe acute respiratory failure and might reduce the need for endotracheal intubation.