Effects of oral ethanol on end-tidal CO₂tension in patients misusing alcohol

This study examines the effect of oral ethanol ingestion on P(et)CO₂ and other respiratory variables in alcohol-misusing subjects. Twelve patients were given a loading dose of alcohol (0.270 g/kg) followed by a second dose (0.135 g/kg) half an hour later, increasing blood alcohol to a mean of 82.0 +/- 10.3 (SEM) mg/100 ml at 1 hour. Five patients were classified as hazardous drinkers with evidence of mild alcohol dependence but no toxicity (Severity of Alcohol Dependency (SADQ) score < 15/60; serum carbohydrate-deficient transferrin < 6%). These patients showed a significant fall in mean end-tidal PCO² (P(et)CO₂) on alcohol (2.08 +/- 0.61 mm Hg; p = 0.027) with slightly increased ventilation (1.76 +/- 0.94 1 min(-1), p = 0.14); responses similar to those previously reported for normal subjects. Seven patients had evidence of moderate alcohol dependency and/or recent use (SADQ > 15/60; CDT > 6%). In these patients P et CO₂ did not fall after alcohol challenge (mean change + 0.61 mm Hg; p > 0.30). There were significant correlations between the changes in P et CO₂ and CDT (n = 12; r(s)= 0.66, p = 0.019) and SADQ (n = 11; r(s)= 0.688, p = 0.019). The results show that P(et)CO₂ control is abnormal in the alcohol dependency syndrome.