Cardiovascular autonomic control during short-term thermoneutral and cool head-out immersion.
BACKGROUND
Moderately cold head-out water immersion stimulates both baro- and cold-receptors, and triggers complex and contradictory effects on the cardiovascular system and its autonomic nervous control.


OBJECTIVE
To assess the effects of water immersion and cold on cardiovascular status and related autonomic nervous activity.


METHODS
Hemodynamic variables and indexes of autonomic nervous activity (analysis of heart rate and blood pressure variability) were evaluated in 12 healthy subjects during 3 exposures of 20 min each in the upright position, i.e., in air (AIR, 24-25 degrees C), and during head-out water immersion at 35-36 degrees C (WIn) and 26-27 degrees C (WIc).


RESULTS
Plasma noradrenaline, systolic and diastolic blood pressure, and total peripheral resistances were reduced during WIn compared to AIR (263.9 +/- 39.4 vs. 492.5 +/- 35.7 pg x ml(-1), 116.5 +/- 3.7 and 65.4 +/- 1.7 mmHg vs. 140.8 +/- 4.7 and 89.8 +/- 2.8 mmHg, 14.1 +/- 1.0 vs. 16.3 +/- 0.9 mmHg x L(-1) x min, respectively) while they were increased during WIc (530.8 +/- 84.7 pg ml(-1), 148.0 +/- 7.0 mmHg, 80.8 +/- 3.0 mmHg, and 25.8 +/- 1.9 mmHg x L(-1) x min, respectively). The blood pressure variability was reduced to the same extent during WIc and Win compared to AIR. Heart rate decreased during WIn (67.8 +/- 2.7 vs. 81.2 +/- 2.7 bpm during AIR), in parallel with an increased cardiac parasympathetic activity. This pattern was strengthened during WIc (55.3 +/- 2.2 bpm).


CONCLUSIONS
Thermoneutral WI lowered sympathetic activity and arterial tone, while moderate whole-body skin cooling triggered vascular sympathetic activation. Conversely, both WI and cold triggered cardiac parasympathetic activation, highlighting a complex autonomic control of the cardiovascular system.
Mourot
Laurent
L
Université de Franche Comté, Physiologie, Faculté de Médecine, Besançon, France. mourotlaurent@hotmail.com
Bouhaddi
Malika
M
Gandelin
Emmanuel
E
Cappelle
Sylvie
S
Dumoulin
Gilles
G
Wolf
Jean-Pierre
JP
Rouillon
Jean Denis
JD
Regnard
Jacques
J
D000328:Adult; D000704:Analysis of Variance; D001127:Arginine Vasopressin / Q000097:blood; D009320:Atrial Natriuretic Factor / Q000097:blood; D001341:Autonomic Nervous System / Q000378:metabolism / Q000502:physiology*; D001831:Body Temperature; D002307:Cardiography, Impedance; D002320:Cardiovascular Physiological Phenomena; D002319:Cardiovascular System / Q000294:innervation; D002395:Catecholamines / Q000097:blood; D003080:Cold Temperature; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D007101:Immersion; D008297:Male; D011187:Posture / Q000502:physiology; D013057:Spectrum Analysis; D014867:Water
D002395:Catecholamines; D014867:Water; D001127:Arginine Vasopressin; D009320:Atrial Natriuretic Factor