title: Haemodynamic effects of hyperbaric hyperoxia in healthy volunteers: an echocardiographic and Doppler study.
abstract: In the present study, we observed the haemodynamic changes, using echocardiography and Doppler, in ten healthy volunteers during 6 h of compression in a hyperbaric chamber with a protocol designed to reproduce the conditions as near as possible to a real dive. Ambient pressure varied from 1.6 to 3 atm (1 atm=101.325 kPa) and partial pressure of inspired O2 from 1.2 to 2.8 atm. Subjects performed periods of exercise with breathing through a closed-circuit self-contained underwater breathing apparatus (SCUBA). Subjects did not eat or drink during the study. Examinations were performed after 15 min and 5 h. After 15 min, stroke volume (SV), left atrial (LA) diameter and left ventricular (LV) end-diastolic diameter (LVEDD) decreased. Heart rate (HR) and cardiac output (CO) did not vary, but indices of the LV systolic performance decreased by 10% and the LV meridional wall stress increased by 17%. After 5 h, although weight decreased, the serum protein concentration increased. Compared with values obtained after 15 min, SV and CO decreased, but LV systolic performance, LA diameter, LVEDD and LV meridional wall stress remained unchanged. Compared with the reference values obtained at sea level, total arterial compliance decreased, HR remained unchanged and CO decreased. In conclusion, hyperbaric hyperoxia results in significant haemodynamic changes. Initially, hyperoxia and the SCUBA system are responsible for reducing LV preload, increasing LV afterload and decreasing LV systolic performance, although CO did not change. Prolonged exposure resulted in a further decrease in LV preload, because of dehydration, and in a further increase in LV afterload, due to systemic vasoconstriction, with the consequence of decreasing CO.
authors.affiliation: Service de Réanimation Médico-Chirurgicale et de Surveillance Continue, Centre Hospitalier du pays d'Aix, Aix en Provence, France. fmolena@ch-aix.fr
authors.forename: Florence
authors.initials: F
authors.lastname: Molénat
authors.forename: Alain
authors.initials: A
authors.lastname: Boussuges
authors.forename: Aliocha
authors.initials: A
authors.lastname: Grandfond
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Rostain
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Sainty
authors.forename: Claude
authors.initials: C
authors.lastname: Robinet
authors.forename: François
authors.initials: F
authors.lastname: Galland
authors.forename: Jean Louis
authors.initials: JL
authors.lastname: Meliet
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D002248:Carbon Monoxide / Q000378:metabolism; D004242:Diving / Q000502:physiology*; D015150:Echocardiography, Doppler; D005500:Follow-Up Studies; D006801:Humans; D006931:Hyperbaric Oxygenation; D018496:Hyperoxia / Q000097:blood*; D006973:Hypertension / Q000503:physiopathology; D008297:Male; D013318:Stroke Volume; D013599:Systole; D013997:Time Factors; D014655:Vascular Resistance; D014661:Vasoconstriction; D016277:Ventricular Function, Left / Q000502:physiology
chemical_list: D002248:Carbon Monoxide