Cardiovascular changes induced by cold water immersion during hyperbaric hyperoxic exposure.
The present study was designed to assess the cardiac changes induced by cold water immersion compared with dry conditions during a prolonged hyperbaric and hyperoxic exposure (ambient pressure between 1.6 and 3 ATA and PiO(2) between 1.2 and 2.8 ATA). Ten healthy volunteers were studied during a 6 h compression in a hyperbaric chamber with immersion up to the neck in cold water while wearing wet suits. Results were compared with measurements obtained in dry conditions. Echocardiography and Doppler examinations were performed after 15 min and 5 h. Stroke volume, left atrial and left ventricular (LV) diameters remained unchanged during immersion, whereas they significantly fell during the dry session. As an index of LV contractility, percentage fractional shortening remained unchanged, in contrast to a decrease during dry experiment. Heart rate (HR) significantly decreased after 5 h, although it had not changed during the dry session. The changes in the total arterial compliance were similar during the immersed and dry sessions, with a significant decrease after 5 h. In immersed and dry conditions, cardiac output was unchanged after 15 min but decreased by almost 20% after 5 h. This decrease was related to a decrease in HR during immersion and to a decrease in stroke volume in dry conditions. The hydrostatic pressure exerted by water immersion on the systemic vessels could explain these differences. Indeed, the redistribution of blood volume towards the compliant thoracic bed may conceal a part of hypovolaemia that developed in the course of the session.
Boussuges
Alain
A
Institut de Médecine Navale du Service de Santé des Armées, Boulevard de Saint-Anne, 83800 Toulon Armées, France. alainboussuges@libertysurf.fr
Molenat
Florence
F
Grandfond
Aliocha
A
Regnard
Jacques
J
Wolf
Jean-Pierre
JP
Galland
François
F
Robinet
Claude
C
D000328:Adult; D001158:Arteries / Q000503:physiopathology; D001794:Blood Pressure; D001810:Blood Volume; D002302:Cardiac Output; D002319:Cardiovascular System / Q000000981:diagnostic imaging / Q000503:physiopathology*; D003080:Cold Temperature; D003187:Compliance; D004242:Diving; D018619:Echocardiography, Doppler, Pulsed; D006339:Heart Rate; D006801:Humans; D006931:Hyperbaric Oxygenation; D018496:Hyperoxia / Q000000981:diagnostic imaging / Q000503:physiopathology*; D007101:Immersion; D008297:Male; D009200:Myocardial Contraction; D013318:Stroke Volume; D013997:Time Factors; D016277:Ventricular Function, Left; D014867:Water
D014867:Water