Dive response of children in relation to cold-water near-drowning.
The strength of the dive response, as judged by the combination of breath-hold duration (BHD) and bradycardia, was compared in 87 children (4-13 yr old) and 68 adults (20-68 yr old) during simulated dives in 29 degrees C water. Mean BHD in children (16.1 s) was only 37.4% (P less than 0.001) of adult BHD (43.0 s). Within children, BHD was significantly (P less than 0.001) dependent on age (A in yr) according to the regression BHD = -1.46 + 2.27A. No age dependency of BHD occurred in adults. Due to the low BHD of children, only 14/87 (16.1%) were able to breath hold for the 25 s necessary to develop full diving bradycardia. For these 14 children, their bradycardia (36.1% reduction) was insignificantly different (P greater than 0.50) from that of adults (36.4%). These experimental findings demonstrate that the dive response of children is extremely weak, due mainly to their very low BHD. Since lower water temperature would probably accentuate the shortness of BHD (according to previous findings for adults), it is concluded that the dive response is unlikely to make a significant contribution to the prolonged resuscitatibility of children who are victims of cold-water near-drowning.
Ramey
C A
CA
Department of Biology, University of Victoria, British Columbia, Canada.
Ramey
D N
DN
Hayward
J S
JS
D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology; D002648:Child; D002675:Child, Preschool; D003080:Cold Temperature; D004242:Diving; D004332:Drowning; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D012119:Respiration; D013997:Time Factors