Heart rate and blood pressure time courses during prolonged dry apnoea in breath-hold divers.
To define the dynamics of cardiovascular adjustments to apnoea, beat-to-beat heart rate (HR) and blood pressure and arterial oxygen saturation (SaO(2)) were recorded during prolonged breath-holding in air in 20 divers. Apnoea had a mean duration of 210 +/- 70 s. In all subjects, HR attained a value 14 beats min(-1) lower than control within the initial 30 s (phase I). HR did not change for the following 2-2.5 min (phase II). Then, nine subjects interrupted the apnoea (group A), whereas 11 subjects (group B) could prolong the breath-holding for about 100 s, during which HR continuously decreased (phase III). In both groups, mean blood pressure was 8 mmHg above control at the end of phase I; it then further increased by additional 12 mmHg at the end of the apnoea. In both groups, SaO(2) did not change in the initial 100-140 s of apnoea; then, it decreased to 95% at the end of phase II. In group B, SaO(2) further diminished to 84% at the end of phase III. A typical pattern of cardiovascular readjustments was identified during dry apnoea. This pattern was not compatible with a role for baroreflexes in phase I and phase II. Further readjustment in group B may imply a role for both baroreflexes and chemoreflexes. Hypothesis has been made that the end of phase II corresponds to physiological breakpoint.
Perini
Renza
R
Dipartimento di Scienze Biomediche e Biotecnologie, Sezione di Fisiologia Umana, Università di Brescia, viale Europa 11, Brescia, Italy. perini@med.unibs.it
Tironi
Adelaide
A
Gheza
Alberto
A
Butti
Ferdinando
F
Moia
Christian
C
Ferretti
Guido
G
D000222:Adaptation, Physiological; D000328:Adult; D001049:Apnea / Q000378:metabolism / Q000503:physiopathology*; D001341:Autonomic Nervous System / Q000503:physiopathology; D017704:Baroreflex; D001794:Blood Pressure; D001919:Bradycardia / Q000503:physiopathology; D004242:Diving; D005260:Female; D006339:Heart Rate; D006801:Humans; D006973:Hypertension / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D015656:Respiratory Mechanics; D013997:Time Factors
D010100:Oxygen