title: Effects of repeated Valsalva maneuver straining on cardiac and vasoconstrictive baroreflex responses.
abstract: BACKGROUND
  We hypothesized that repeated respiratory straining maneuvers (repeated SM) designed to elevate arterial BPs (arterial baroreceptor loading) would acutely increase baroreflex responses.
  
  
  METHODS
  We tested this hypothesis by measuring cardiac baroreflex responses to carotid baroreceptor stimulation (neck pressures), and changes in heart rate and diastolic BP after reductions in BP induced by a 15-s Valsalva maneuver in 10 female and 10 male subjects at 1, 3, 6, and 24 h after performing repeated SM. Baroreflex responses were also measured in each subject at 1, 3, 6, and 24 h at the same time on a separate day without repeated SM (control) in a randomized, counter-balanced cross-over experimental design.
  
  
  RESULTS
  There was no statistical difference in carotid-cardiac and peripheral vascular baroreflex responses measured across time following repeated SM compared with the control condition. Integrated cardiac baroreflex response (deltaHR/ deltaSBP) measured during performance of a Valsalva maneuver was increased by approximately 50% to 1.1 +/- 0.2 bpm x mm Hg(-1) at 1 h and 1.0 +/- 0.1 bpm x mm Hg(-1) at 3 h following repeated SM compared with the control condition (0.7 +/- 0.1 bpm x mm Hg(-1) at both 1 and 3 h, respectively). However, integrated cardiac baroreflex response after repeated SM returned to control levels at 6 and 24 h after training. These responses did not differ between men and women.
  
  
  CONCLUSIONS
  Our results are consistent with the notion that arterial baroreceptor loading induced by repeated SM increased aortic, but not carotid, cardiac baroreflex responses for as long as 3 h after repeated SM. We conclude that repeated SM increases cardiac baroreflex responsiveness which may provide patients, astronauts, and high-performance aircraft pilots with protection from development of orthostatic hypotension.
authors.affiliation: U.S. Army Institute of Surgical Research, Ft. Sam Houston, TX 78234-6315, USA. victor.convertino@cen.amedd.army.mil
authors.forename: Victor A
authors.initials: VA
authors.lastname: Convertino
authors.forename: Duane A
authors.initials: DA
authors.lastname: Ratliff
authors.forename: Donald F
authors.initials: DF
authors.lastname: Doerr
authors.forename: David A
authors.initials: DA
authors.lastname: Ludwig
authors.forename: Gary W
authors.initials: GW
authors.lastname: Muniz
authors.forename: Erik
authors.initials: E
authors.lastname: Benedetti
authors.forename: Jose
authors.initials: J
authors.lastname: Chavarria
authors.forename: Susan
authors.initials: S
authors.lastname: Koreen
authors.forename: Claude
authors.initials: C
authors.lastname: Nguyen
authors.forename: Jeff
authors.initials: J
authors.lastname: Wang
mesh_terms: D000328:Adult; D000337:Aerospace Medicine; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure; D005260:Female; D006339:Heart Rate; D006801:Humans; D007024:Hypotension, Orthostatic / Q000517:prevention & control; D008297:Male; D011311:Pressoreceptors / Q000502:physiology; D013026:Space Flight; D014636:Valsalva Maneuver