Safety of regadenoson, a selective adenosine A2A agonist, in patients with chronic obstructive pulmonary disease: A randomized, double-blind, placebo-controlled trial (RegCOPD trial).

BACKGROUND: Patients with reactive airways are at risk for adenosine-induced bronchoconstriction, mediated via A(2B) and/or A(3) adenosine receptors. METHODS AND RESULTS: In this randomized, double-blind, placebo-controlled crossover trial, we examined the safety of regadenoson, a selective adenosine A(2A) receptor agonist, in patients with moderate chronic obstructive pulmonary disease (COPD) (n = 38) and patients with severe COPD (n = 11) with a baseline mean forced expiratory volume in 1 second (FEV(1)) of 1.74 +/- 0.50 L and 1.0 +/- 0.35 L, respectively, 37% of whom had dyspnea during activities of daily living. Patients receiving glucocorticoids or oxygen and those with pretreatment wheezing were included. Short-acting bronchodilators were withheld for at least 8 hours before treatment. No differences emerged between regadenoson and placebo on multiple lung function parameters, including repeated FEV(1) and forced vital capacity, respiratory rate, pulmonary examinations, and oxygen saturation. The mean maximum decline in FEV(1) was 0.11 +/- 0.02 L and 0.12 +/- 0.02 L (P = .55) in patients after regadenoson and placebo, respectively, and new-onset wheezing was observed in 6% and 12%, respectively (P = .33). No patient required acute treatment with bronchodilators or oxygen. CONCLUSIONS: This pilot study showed the overall safety of regadenoson in 49 compromised outpatients with clinically stable moderate and severe chronic obstructive pulmonary disease.

Voluntary hyperventilation into a simple mixing chamber relieves high altitude hypoxia.

Involuntary hyperventilation is a critical factor in acclimatization to a high altitude. Unacclimatized subjects do poorly when acutely exposed to high altitude. This may not be due to hypocapnia itself, but rather an associated symptom which inhibits hypoxic respiratory stimulation. In an unacclimatized individual, voluntary hyperventilation may greatly relieve hypoxia and may be an alternative to involuntary hyperventilation. However, subjects voluntarily hyperventilating may overventilate and become disabled from severe hypocapnia. A simple mixing chamber is described which makes voluntary hyperventilation easier, safer, and possibly more effective. A subject breathing into a mixing chamber was able to maintain an SaO2 of 90% at 20,000 ft.