CHANGES IN VENTILATORY PATTERNS DURING HALOTHANE ANAESTHESIA IN CHILDREN

Halothane is the most commonly used anaesthetic agent in paediatric anaesthesia (Reynolds, 1962; Krivosic-Horber, Sauvage and Calmes, 1973; Gov-aerts and Sanders, 1975) and, like all halogenated hydrocarbon anaesthetics, depresses ventilation (Munson, 1972) — an effect dependent on the age of the patient (Lindahl, Olsson and Thomson, 1981) and on the alveolar concentration of the anaesthetic (Munson et al., 1966). However, few studies are available which detail the changes in ventilatory pat-terns during halothane anaesthesia in children (Wil-son and Harrison, 1964). This paper describes measurements of minute ventilation (VE), tidal volume (VT), respiratory frequency (/), mean inspiratory flow (VT/7I), inspiratory timing (T\IVot) and end-tidal carbon dioxide tension (PE'CO) m 12 children weighing between 10 and 20 kg. The measurements were made at increasing inspired concentrations of halothane. PATIENTS AND METHODS Twelve children, scheduled for elective minor surgi-cal procedures, were studied. Mean ( ± SD) age was 39 ± 17 months (range 20-68 months), weight 15 ± 2.9 kg (range 10.5-20 kg) and height 96 ± 11.5 cm (range 77-111 cm). All patients were healthy, were taking no medication and had normal cardiopulmonary function. Parental consent was obtained after full explanation before anaesthesia. None of the children included in this study was pre-medicated. The study was performed either immediately before surgery (eight children), or dur-ing the period after operation (four children) if n