Authors: P Delapille E Verin C TournyChollet P Pasquis
Publish Date: 2001/10/03
Volume: 86, Issue: 1, Pages: 97-103
Abstract
The aim of this study was to determine the effects on respiratory drive of two factors one mechanical lung volume and one chemical sensitivity to hypercapnia that are involved in determining the breathhold duration BHD Functional residual capacity was measured by helium dilution with the subject seated in air seated in water and in the prone position in water Hyperoxic hypercapnia rebreathing Reads method was carried out under identical environmental conditions to assess the effects of CO2 pressure on respiratory centre output by measuring ventilation mean inspiratory flow and occlusion pressure Sixteen healthy volunteers were tested 8 trained divers and 8 nondivers Functional residual capacity decreased for the postures seated in water 308–348 and for prone position in water 203–209 when compared to the posture seated in air P00001 all subjects pooled No difference was found between groups The slopes of the linear regression which characterised the sensitivity to CO2 and were determined with the rebreathing tests revealed differences between the two populations ventilation P00001 mean inspiratory flow P005 No difference was found for occlusion pressure or between the different postures These results confirmed a lower sensitivity to CO2 for trained divers This adaptation was shown to decrease respiratory centre activity at the origin of the breathhold breaking point The immersion did not influence respiratory drive despite a decrease in lung volumes The authors suggest that these findings may be explained by a specific apnoea training and a pronounced bradycardia in immersion
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