Pulmonary gas exchange during apnoea in exercising men

Abstract

There is indirect evidence that cardiovascular responses to apnoea result in a temporary slowing of the O(2) uptake in the lungs in exercising humans. The present study was undertaken in an attempt to determine directly to what extent this occurs, and whether the magnitude of this slowing is such that it must be the result of concomitant cardiovascular readjustments and not merely a result of an isolated apnoea-induced fall in the arterial O(2) saturation ( S(a)O(2)). Eight men performed 120 W leg exercise and performed repeated apnoeas of 10-40 s duration. Heart rate, S(a)O(2), and breath-by-breath gas exchange were determined. Pulmonary O(2) uptake fell gradually as breath-holds proceeded by [mean (SEM)] 74 (3)% of the pre-apnoea O(2) uptake. This decrease was significantly larger than could be accounted for by the fall in S(a)O(2) alone [ S(a)O(2) fall -30 (3)%], which it is estimated would have resulted in a fall of pulmonary O(2) uptake of -54 (5)%. We conclude that cardiovascular responses to apnoea contribute significantly to reducing pulmonary O(2) uptake during apnoea in exercising men.

Studies on inspiratory and expiratory glossopharyngeal breathing in breath-hold divers employing magnetic resonance imaging and spirometry

“…A standard helium dilution procedure (5% He; 95% O 2 ) was employed to obtain measurements of RV and RV À GE has been described previously (Lindholm and Linnarsson 2002). Briefly, the system utilized rebreathing of preset volumes of gas from a bag and analysis of gases using a mass spectrometer (QMG 420, Balzer, Lichtenstein) modified for respiratory measurements (Innovision AS, Odense, Denmark).…”

Cardiac and ventilatory responses to apneic exercise

“…So far, all studies investigating apneas under exercise conditions, except one study by Butler and Woakes (1987), focussed on steady-state exercise (Andersson et al 2002(Andersson et al , 2004Bjertnaes et al 1984;Lindholm and Linnarsson 2002), with the subject exercising for a certain amount of time before holding his breath. This is all the more surprising since this is not the way breath-hold diving is performed in real-life situations.…”

Relationships between the extent of apnea-induced bradycardia and the vascular response in the arm and leg during dynamic two-legged knee extension exercise

“…Some diving animals, such as seals, show remarkable bradycardia during voluntary diving (36). In humans, the bradycardic response seen during apnea or diving is smaller than in diving animals and varies a great deal from individual to individual (5,21,24,31,32).Acute apnea-induced bradycardia is observed in humans during exercise on land (3,4,6,7,22,25,26,27,30,33). Bjertnaes et al (7) reported that during exercise, the decrease in cardiac output (CO) induced by apnea was nearly paralleled by a reduction in heart rate (HR).…”

“…Acute apnea-induced bradycardia is observed in humans during exercise on land (3,4,6,7,22,25,26,27,30,33). Bjertnaes et al (7) reported that during exercise, the decrease in cardiac output (CO) induced by apnea was nearly paralleled by a reduction in heart rate (HR).…”