PULMONARY-ARTERY PRESSURE RESPONSE TO HYPOXIA IN SLEEP-APNEA

The pulmonary artery pressure (Ppa) responses to short runs of acute h ypoxia at two different levels of end-tidal CO2 were measured in nine normal subjects and in 20 patients with moderate to severe obstructive sleep apnea (OSA). in normal subjects the mean increase in Ppa in res ponse to eucapnic hypoxia was 8 +/- 2 mm Hg (SEM) and was not differen t from the response to hypercapnic hypoxia (9 +/- 2 mm Hg, p > 0.2). I n patients with OSA, the mean increase of Ppa was 8 +/- 1 mm Hg to euc apnic hypoxia, and the response to hypercapnic hypoxia was higher at 1 0 +/- 1 mm Hg (p = 0.01). Pulmonary presser response to hypoxia was au gmented (> 10 mm Hg) by hypercapnia in four of 20 patients with OSA bu t in none of the normal subjects. Normoxic hypercapnia alone was a wea k stimulus, increasing Ppa by > 5 mm Hg in only two of nine patients w ith OSA studied. In conclusion, Ppa increases in both normal subjects and patients with OSA exposed to a ramp of acute isocapnic hypoxia. Th ere were clear interindividual differences in pulmonary artery respons e. Hypercapnia did not produce clinical significant changes in Ppa in either group.