Abstract
Abstract
Purpose
We analysed the characteristics of arterial baroreflexes during the first phase of apnoea (φ1).
Methods
12 divers performed rest and exercise (30 W) apnoeas (air and oxygen). We measured beat-by-beat R-to-R interval (RRi) and mean arterial pressure (MAP). Mean RRi and MAP values defined the operating point (OP) before (PRE-ss) and in the second phase (φ2) of apnoea. Baroreflex sensitivity (BRS, ms·mmHg−1) was calculated with the sequence method.
Results
In PRE-ss, BRS was (median [IQR]): at rest, 20.3 [10.0–28.6] in air and 18.8 [13.8–25.2] in O2; at exercise 9.2[8.4–13.2] in air and 10.1[8.4–13.6] in O2. In φ1, during MAP decrease, BRS was lower than in PRE-ss at rest (6.6 [5.3–11.4] in air and 7.7 [4.9–14.3] in O2, p < 0.05). At exercise, BRS in φ1 was 6.4 [3.9–13.1] in air and 6.7 [4.1–9.5] in O2. After attainment of minimum MAP (MAPmin), baroreflex resetting started. After attainment of minimum RRi, baroreflex sequences reappeared. In φ2, BRS at rest was 12.1 [9.6–16.2] in air, 12.9 [9.2–15.8] in O2. At exercise (no φ2 in air), it was 7.9 [5.4–10.7] in O2. In φ2, OP acts at higher MAP values.
Conclusion
In apnoea φ1, there is a sudden correction of MAP fall via baroreflex. The lower BRS in the earliest φ1 suggests a possible parasympathetic mechanism underpinning this reduction. After MAPmin, baroreflex resets, displacing its OP at higher MAP level; thus, resetting may not be due to central command. After resetting, restoration of BRS suggests re-establishment of vagal drive.
Funder
Swiss National Science Foundation
University of Geneva
Publisher
Springer Science and Business Media LLC
Subject
Physiology (medical),Public Health, Environmental and Occupational Health,Orthopedics and Sports Medicine,General Medicine,Public Health, Environmental and Occupational Health,Physiology
Cited by
8 articles.
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