title: Effect of caffeine on the ventilatory response to inhaled carbon dioxide.
abstract: We investigated the effect of caffeine on the hypercapnic ventilatory response (HCVR) using steady state (SS) and rebreathing (RB) methods in 6 subjects. They received caffeine (5 mg/kg) or saline intravenously in a randomized, double-blind, crossover manner, with measurement of serum caffeine levels. PETCO2 and (VE), normalized for vital capacity (VC), were measured continually during RB and during the last 5 min of SS runs. The slope of the VE-PETCO2 response increased from 0.21 +/- 0.14 to 0.38 +/- 0.14 and from 0.23 +/- 0.12 to 0.59 +/- 0.45 VC.min-1.mmHg-1, measured by RB and SS respectively (P < 0.05). Plotting VT vs PETCO2 revealed a parallel shift (additive effect) in the response measured by RB after caffeine; but an increased slope (multiplicative effect) in the VT-PETCO2 relation measured in SS. We conclude that caffeine acts as a respiratory stimulant and increases the HCVR, but that assessment of the caffeine-CO2 interaction is dependent on the methodology employed.
authors.affiliation: Respiratory Medicine Service, McGill University-Montreal Children's Hospital Research Institute, Quebec, Canada.
authors.forename: P
authors.initials: P
authors.lastname: Pianosi
authors.forename: D
authors.initials: D
authors.lastname: Grondin
authors.forename: K
authors.initials: K
authors.lastname: Desmond
authors.forename: A L
authors.initials: AL
authors.lastname: Coates
authors.forename: J V
authors.initials: JV
authors.lastname: Aranda
mesh_terms: D000280:Administration, Inhalation; D000328:Adult; D001993:Bronchodilator Agents / Q000494:pharmacology; D002110:Caffeine / Q000097:blood / Q000494:pharmacology*; D002245:Carbon Dioxide / Q000008:administration & dosage / Q000494:pharmacology*; D004311:Double-Blind Method; D006801:Humans; D006935:Hypercapnia / Q000503:physiopathology; D008297:Male; D012119:Respiration / Q000187:drug effects*; D013147:Spirometry; D013990:Tidal Volume / Q000187:drug effects
chemical_list: D001993:Bronchodilator Agents; D002245:Carbon Dioxide; D002110:Caffeine