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Articles in PresS, published online ahead of print September 13, 2002
J Appl Physiol, 10.1152/jap.01258.2001
Submitted on December 26, 2001
Accepted on September 3, 2002
1 Department of Anesthesiology, University Medical Center, Regensburg, Regensburg, Germany
2 Department of Physiological Sciences, Universidad Cayetano Heredia, Lima, Peru
3 Institute of Respiratory Diseases, University of Catania, Catania, Italy
4 Department of Internal Medicine and Institute of Hematology, University of Pavia and Istituto di Ricovero e Cura a Carattere Scientifico S. Matteo, Pavia, Italy
5 Department of Pathology, University of Pavia and Istituto di Ricovero e Cura a Carattere Scientifico S. Matteo, Pavia, Italy
* To whom correspondence should be addressed. E-mail: keyl{at}rkananw1.ngate.uni-regensburg.de.
We evaluated whether subjects with polycythemia and chronic mountain sickness (CMS) suffer from an impaired autonomic cardiovascular regulation, and tested the hypothesis that an increase in arterial oxygen saturation (SaO2), either by a slow-frequency breathing pattern or by oxygen administration, has a beneficial effect on arterial baroreflex sensitivity in subjects with CMS. Ten Andean natives with an hematocrit (Hct) >65%, and 10 natives with an Hct <60%, all living permanently at an altitude of 4300 m, were included in the study. Cardiovascular autonomic regulation was evaluated by spectral analysis of hemodynamic parameters and by computation of the spontaneous baroreflex sensitivity, while subjects breathed spontaneously or frequency-controlled at 0.1 Hz and 0.25 Hz, respectively. The recordings were repeated after a one-hour administration of supplemental oxygen, and after frequency-controlled breathing at 6 breaths/min for one hour, respectively. Subjects with Hct >65% showed an increased incidence of CMS compared to subjects with Hct <60%. Spontaneous baroreflex sensitivity was lower in subjects with high Hct compared to the control group, (repeated measurements on 2 subsequent days: 3.9 ± 2.1 ms/mm Hg and 5.9 ± 2.2 ms/mm Hg vs. 11.2 ± 8.5 ms/mm Hg and 11.1 ± 5.5 ms/mm Hg, p<0.05 between groups). The effects of supplemental oxygen or modification of the breathing pattern were: 1) Endexpiratory carbon dioxide decreased and SaO2 increased in all subjects after the administration of oxygen. 2) Heart rate decreased significantly after both maneuvers in both groups. 3) Spontaneous baroreflex sensitivity increased significantly in subjects with high Hct and did not differ from subjects with low Hct after the administration of oxygen, as well as after low-frequency breathing. Temporary slow-frequency breathing may provide a beneficial effect on the autonomic cardiovascular function in high-altitude natives with polycythemia and CMS.
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