Effects of lung volume and chemoreceptor activity on blood pressure and R-R interval during the Valsalva maneuver.
OBJECTIVE
The purpose of the present investigation was to examine the effect of lung volume and inspiration of 100% oxygen on blood pressure and R-R interval responses during the Valsalva maneuver.


METHODS
Fourteen healthy subjects completed eight Valsalva maneuvers. Four of the maneuvers were completed after inspiring to total lung capacity while the remaining maneuvers were completed at end-expiratory lung volume. Two maneuvers completed at a given lung volume were performed under hyperoxic conditions while the remaining maneuvers were completed under normoxic conditions.


RESULTS
Overall, a significant increase in blood pressure and decrease in R-R interval occurred throughout phases I-IV of the Valsalva maneuvers that were initiated from end-expiratory lung volume as compared to total lung capacity. These changes were accompanied by a concomitant increase in baroreflex sensitivity during phase IV. Furthermore, independent of lung volume the baroreflex response was attenuated under hyperoxic conditions.


CONCLUSIONS
We conclude that the lung volume that exists prior to the onset of the maneuver alters the blood pressure and R-R interval response during phases I-IV of the Valsalva maneuver. Furthermore, we suggest that these responses are mediated in part by changes in chemoreceptor activity since the baroreflex was reset and the sensitivity was reduced under hyperoxic conditions. Given these findings, we recommend that lung volume be controlled when patients are completing a Valsalva maneuver to obtain reliable and reproducible measures of blood pressure, R-R interval duration and baroreflex sensitivity.
Mateika
Jason H
JH
John D. Dingell Veterans Affairs Medical Center, Detroit, MI 48201, USA. jmateika@intmed.wayne.edn
Demeersman
Ronald E
RE
Kim
Jaehee
J
D000280:Administration, Inhalation; D000328:Adult; D017704:Baroreflex / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology*; D002245:Carbon Dioxide / Q000097:blood; D002628:Chemoreceptor Cells / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008168:Lung / Q000033:anatomy & histology / Q000502:physiology*; D008176:Lung Volume Measurements; D008297:Male; D010100:Oxygen; D010101:Oxygen Consumption / Q000502:physiology; D010275:Parasympathetic Nervous System / Q000502:physiology; D013564:Sympathetic Nervous System / Q000502:physiology; D013990:Tidal Volume / Q000502:physiology; D014636:Valsalva Maneuver / Q000502:physiology*
D002245:Carbon Dioxide; D010100:Oxygen