title: Valsalva maneuver: shortest optimal expiratory strain duration.
abstract: OBJECTIVE
  To quantitate the level of difficulty and determine consistency of hemodynamic responses with various expiratory strain (ES) durations.
  
  
  METHODS
  Thirty-four healthy subjects performed the Valsalva maneuver (VM) with an ES duration of 10, 12, and 15 seconds in random order. Level of difficulty after each trial was rated 1 to 10, with 10 being the most difficult. Blood pressure and heart rate (HR) were recorded continuously and non-invasively. Parameters studied were Valsalva ratio (VR), early phase II (IIE), late phase II (IIL), tachycardia latency (TL), bradycardia latency (BL), and overshoot latency (OV-L). Consistency of responses was calculated.
  
  
  RESULTS
  DIFFICULTY INCREASED SIGNIFICANTLY WITH INCREASED ES DURATION: 5.1±0.1 (mean±SEM) at 10 seconds, 5.9±0.1 at 12 seconds, and 6.8±0.1 at 15 seconds (p<0.001). Phase IIE, TL, BL, OV-L, and VR response did not differ statistically with increasing ES durations, and there were no differences in variability. Phase IIL response increased significantly with increasing ES duration. Phase IIL was poorly delineated in 14 of 102 trials with 10 seconds ES duration.
  
  
  CONCLUSIONS
  ES duration of 10 seconds created a low level of difficulty in healthy individuals. This strain duration produced consistent hemodynamic response for all parameters tested except IIL phase. The absence of IIL phase with 10 seconds ES should not be interpreted as an indicator of sympathetic vasoconstrictor failure.
authors.affiliation: Department of Medicine, Union Memorial Hospital, Baltimore, MD, USA.
authors.forename: Ramesh K
authors.initials: RK
authors.lastname: Khurana
authors.forename: Deepika
authors.initials: D
authors.lastname: Mittal
authors.forename: Norman H
authors.initials: NH
authors.lastname: Dubin
keywords: Valsalva maneuver; Valsalva ratio; blood pressure; expiratory strain; heart rate