A beat-by-beat analysis of cardiovascular responses to dry resting and exercise apnoeas in elite divers

Abstract

The lack of steady phase during exercise apnoeas suggests that the conditions determining R3 were already attained at the end of E1. This being so, E2 would correspond to R3.

Cardiovascular responses to dry resting apnoeas in elite divers while breathing pure oxygen

“…In that study, we used exercise as a stimulus and we found not only reduction, but even disappearance of 2 (Sivieri et al, 2015), suggesting the possibility that exercise apnoeas be characterised by different dynamic cardiovascular responses from those of resting apnoeas. In the present study, we conversely analysed the other corollary of our hypothesis, namely the direct effects of increased pulmonary oxygen stores on the duration of 2, by comparing resting apnoeas in air and in oxygen.…”

“…An automated procedure implemented under Matlab (version 7.6.0.324, MathWorks, Natick, MA, USA) was used to this aim (Sivieri et al, 2015). The procedure was based on linear regression analysis, allowing detection of changes in slope between successive phases.…”

“…The procedure was based on linear regression analysis, allowing detection of changes in slope between successive phases. Linear regression was also used (i) to analyse the rate of changes of SBP and f H during 3, (ii) to calculate dynamic baroreflex sensitivity in 1 (Adami et al, 2013;Sivieri et al, 2015), and (iii) to verify steady state of investigated variables in 2 (slope of regression equation significantly equal to zero).…”

“…Ceteris paribus, the time necessary to reach that alveolar gas composition is directly proportional to the body oxygen stores at the beginning of the apnoea and inversely proportional to the body metabolic rate during apnoea. In fact, a beat-by-beat analysis of the cardiovascular responses to apnoeas carried out during light exercise demonstrated not only a reduction, but even a disappearance of 2, with remarkable shortening of 3 (Sivieri et al, 2015).…”

“…In recent years, changes in blood pressure, heart rate (f H ), stroke volume (SV), cardiac output (Q ) and total peripheral resistance (TPR) in response to apnoea (cardiovascular response to apnoea) were determined beat-by-beat on elite divers during apnoeas prolonged to the volitional breaking point (Costalat et al, 2013;Lemaître et al, 2008;Perini et al, 2008Perini et al, , 2010Sivieri et al, 2015). These studies described the cardiovascular response to apnoea as consisting of three distinct phases: (i) a short dynamic phase ( 1), that lasts less than 30 s, characterised by rapid changes in blood Abbreviation: DBP, diastolic blood pressure; fH, heart rate; FIO2, inspired oxygen fraction; MBP, mean blood pressure;Q , cardiac output; SaO2, arterial oxygen saturation; SBP, systolic blood pressure; SV, stroke volume; TPR, total peripheral resistance;V O2, oxygen uptake; 1, first, dynamic phase of the cardiovascular response to apnoea; 2, second, steady-state phase of the cardiovascular response to apnoea; 3, third, dynamic phase of the cardiovascular response to apnoea.pressure and f H ; (ii) a steady state phase ( 2), of about 2 min, in which the values attained by each variable at the end of 1 are maintained invariant; and (iii) a further subsequent dynamic phase ( 3), lasting about 1.5 min, characterised by a continuous decrease in f H and increase in blood pressure, until the volitional breaking point was reached.…”