Rib cage contribution to resting and carbon dioxide stimulated ventilation during 1 MAC isoflurane anaesthesia.
Using respiratory inductive plethysmography, we have measured rib cage and abdominal motion during isoflurane anaesthesia in 16 healthy day-surgery patients. Anaesthesia was induced with propofol and maintained with 1 MAC isoflurane in air-oxygen via a laryngeal mask. Measurements were taken during both resting ventilation and hyperpnoea induced by rebreathing carbon dioxide. For resting ventilation, the rib cage contributed a mean (SD) of 33 (15)% of the total ventilation whilst awake, and 39 (12)% during anaesthesia (ns). With increasing end-tidal carbon dioxide whilst awake, the subjects showed a mean increase in the percentage rib cage contribution of 7.1 (12.5)%/kPa of carbon dioxide. With isoflurane anaesthesia, there was significant depression of this rib cage recruitment with the mean contribution decreasing by 3.6 (7.4)% kPa-1 (P less than 0.05). These results indicate that 1 MAC of isoflurane does not selectively depress rib cage motion, except during carbon dioxide stimulated hyperpnoea.
Lumb
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Division of Anaesthesia, Clinical Research Centre, Harrow, Middlesex.
Petros
A J
AJ
Nunn
J F
JF
D000009:Abdominal Muscles / Q000502:physiology; D000293:Adolescent; D000328:Adult; D000769:Anesthesia, Inhalation; D015992:Body Mass Index; D002245:Carbon Dioxide / Q000502:physiology; D006801:Humans; D007530:Isoflurane / Q000494:pharmacology; D009068:Movement / Q000187:drug effects; D012119:Respiration / Q000502:physiology*; D015656:Respiratory Mechanics / Q000187:drug effects; D012272:Ribs / Q000502:physiology*; D013990:Tidal Volume / Q000502:physiology; D014797:Vital Capacity
D002245:Carbon Dioxide; D007530:Isoflurane