Measurement of gastric P-CO2 as an index of tissue hypoxia during obstructive sleep apnea

Background: Gastric mucosal ischemia develops in critically ill patients in a number of clinical settings due to diversion of blood flow from the spla nchnic bed to more vital organs, and can be detected by the measurement of gastric intramucosal pH (pHi). Study Objective: We hypothesized that simila r changes would occur during obstructive sleep apnea (OSA) due to increased respiratory work during the periods of apnea. Methods: Gastric P-CO2, pHi and arterial blood gases were measured during 3 conditions in 8 patients wi th severe OSA: at baseline awake, while asleep with greater than or equal t o 30 obstructive apneas or hypopneas per hour, and asleep after elimination of apneas with continuous positive airway pressure (CPAP). Results: Signif icant changes between the baseline and apnea conditions were detected using ANOVA for repeated measures for gastric P-CO2, 40.2 +/- 5.3 vs. 85.4 +/- 3 4.0 (p < 0.001), pHi, 7.41 +/- 0.06 vs. 7.11 +/- 0.17 (p < 0.005), and the gastric-arterial P-CO2 difference (D-CO2), -2.3 +/- 5.5 vs. 44.3 +/- 36.21 (p < 0.006). Nasal CPAP returned all measures back to baseline values. Conc lusions: Gastric tissue hypoxia develops in patients with severe OSA and ma y be a marker of disease severity. Treatment of OSA with CPAP eliminates th e regional tissue hypoxia. Copyright(C)2001 S. Karger AG,Basel.