Respiration Physiology (1987) 70, 121-130 121 Elsevier RSP 01328 Respiratory drive during sudden cold water immersion Igor B. Mekjavi61, Andr6 La Prairie ~, Wendy Burke 1 and Bertil Lindborg 2 tSchool of Kinesiology, Simon Fraser University. Burnaby, British Columbia, Canada VSA 1S6, and 2Department of Environmental Medicine, Karolinska Institute, Stockholm, Sweden (Accepted for publication 5 May 1987) Abstract. Sudden decreases in cutaneous temperature induce an immediate ventilatory response, which has been termed the inspiratory or 'gasp' reflex. This respiratory response has been implicated as a contributing factor to cold water immersion drowning. In the present study, five subjects wearing either shorts or a variety of thermal protective apparel were immersed on separate occasions in 10 ° C water. The observed peak mean skin temperature cooling rates (dTs/dt) for the different conditions varied from 6.9 + 2.1 °C/min for the shorts condition to 1.8 + 0.3 ° C/rain for a helicopter pilot suit made of cotton ventile material. During the immersion, recordings were made of respiratory drive, as indicated by the mouth occlusion pressure at 100 msec following the onset of inspiration (Po.1). The respiratory drive, an indicator of central inspiratory activity, correlated well with peak dTs/dt. The slope Po.1/(dTs/dt) was subject dependent and did not appear to be related to body composition. The substantial intersubject variability in the respiratory response is suggested to result from differences in the central integration of thermoafferent information. It is concluded that the inspiratory reflex is the result of cutaneous thermoreceptor activity. Cold; Control of breathing; Gasp; Human; Skin; Temperature Stimulation of cutaneous cold receptors in humans has been observed to instigate sudden deep inspiration (Keatinge and McCance, 1957). Head-out immersion in cold water induces a fourfold increase in ventilation (Martin and Cooper, 1978; Hayward and Eckerson, 1984), characterized by a doubling of frequency and a tripling of tidal volume (Hayward and Eckerson, 1984). The immediate increase in ventilation peaks in the first minute and declines to approximately twice normal values by the fifth minute of immersion (Keatinge and Evans, 1961; Martin et al., 1978; H ayward and Eckerson, 1984). The marked hyperpnea with initial immersion, termed the inspiratory or 'gasp' reflex, has been implicated as one of the major causes of cold water immersion drowning (Keatinge et al., 1969; Goode et aL, 1975). Direct stimulation of afferent fibers in somatic nerves of rabbits has been shown to enhance inspiratory amplitude; the subsequent hyperpnea is proportional to the inten- Correspondence address: Dr. Igor B. Mekjavir, School of Kinesiology, Simon Fraser University, Bumaby, British Columbia, Canada V5A 1S6. 0034-5687/87/$03.50 © 1987 Elsevier Science Publishers B.V. (Biomedical Division)