Continuous monitoring of haemodynamic parameters in humans during the early phase of simulated diving with and without breathholding

Abstract

This study examined the integrative changes of blood pressure (BP) and stroke volume (SV) leading to the initial biphasic heart rate (fc) response (first 15 s) in simulated diving manoeuvres with and without breathholding (BH). Simulated diving was studied in ten young healthy volunteers by application of a gel-filled pack at 0 degree C and 18 degrees C on the forehead with and without BH. Beat-by-beat and second-to-second fc, BP, SV, and total peripheral vascular resistance (TPR) were followed by continuous non-invasive monitoring. In all conditions (BH with forehead cooling at 0 degree and 18 degrees C) there was an early rise in BP triggering the first tachycardial response (fc acceleration) which was immediately counteracted by the concurrent further increase of SV leading to the second phase of early bradycardic response (fc deceleration). Furthermore, the continuous beat-by-beat and second-to-second monitoring allowed the documentation of a highly significant increase of TPR within the first few seconds of the manoeuvres. Our data further indicated that the differences in haemodynamics observed during the stimuli at different temperatures was overruled by BH. Detailed comparisons of the beat-by-beat and second-to-second analyses were unable to show that one method was better than the other. Using continuous non-invasive monitoring of haemodynamic variables during simulated diving manoeuvres it was possible to provide better insights into the physiological principles and meaning of the diving reflex in humans.

Effects of depth and chest volume on cardiac function during breath-hold diving

“…This, however, has long been hampered by technical diYculties in studying fully immersed, free-diving subjects. Most of the knowledge on human diving physiology has been extrapolated either from data obtained in dry apnea in subjects with or without face immersion (Andersson et al 2004;Brick 1966;Duprez et al 2000) in studies of head-out immersed subjects (Dahlback et al 1978;Shiraki et al 1986), or during simulated dives in the pressure chamber (Ferrigno et al 1987). More recently, direct heart exploration using underwater Doppler-echocardiography has documented a reduction of cardiac output during breath-hold diving, due to a decrease of both heart rate and ventricular stroke volume .…”

Cardiac changes induced by immersion and breath-hold diving in humans

“…For years, however, technical difficulties have prevented a comprehensive assessment of cardiovascular changes during breath-hold diving in humans. Most of the knowledge on human diving physiology has been obtained from the study of head-out immersed subjects (9,27), or extrapolated from the results obtained in breath-holding subjects, either with or without face immersion (2,8,10). The recent wide diffusion of recreational and competitive breath-hold diving (with a progressive increase of attained depths) highlighted the presence of serious divingrelated pathologies, like syncope (ascent blackout), decompression illness, hemoptysis, and pulmonary edema, whose pathophysiology is not yet completely understood (13,31).…”

Cold Pressor Stress Cardiac Magnetic Resonance Myocardial Flow Reserve Is Not Useful for Detection of Coronary Endothelial Dysfunction in Women with Signs and Symptoms of Ischemia and No Obstructive CAD

“…This difference may be due to in unintentional provocation of the diving reflex, which stimulates both the sympathetic and parasympathetic nervous system. [34, 35] Lastly response to CPT is heterogeneous, generally causing a relatively small increase in coronary flow compared to what is expected with pharmacological stress, and CMRI MPRI may not be sensitive enough to detect this smaller level of response.…”