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COMBINED INFLUENCE OF POSTURE AND ISOMETRIC HANDGRIP ON PHASE IIA RESPONSES TO THE VALSALVA MANEUVER

Abstract

Barry Faulkner, Marshall Dearmon, Kenneth R. Ladner, Ta’Quoris Newsome, Ryan Aultman, Jon Stavres. University of Southern Mississippi, Hattiesburg, MS.

BACKGROUND: The Valsalva maneuver (VL) is a well-documented assessment of autonomic function, and is characterized by 5 distinct blood pressure phases (Phases I, IIa, IIb, III, and IV). While body position is known to influence the early phase II (a.k.a. “phase IIa”) blood pressure responses, the influence of sympathoexcitation is less clear. The aim of this study was to examine the independent and combined effects of sympathoexcitation (via isometric handgrip) and body position on the phase IIa blood pressure responses to VLs in young healthy adults. METHODS: Seventeen subjects (9 male) participated in 4 separate experimental trials (T1-T4) repeated across 2 different conditions (supine and seated). Trials were conducted in sequential order, and included VLs performed without handgrip (Trials 1 [T1] and 4 [T4]), five minutes of isometric handgrip (HG; 35% MVC; Trial 2 [T2]), and VLs performed with superimposed HG (Trial 3 [T3]). Cardiac rhythm (electrocardiography) and beat-by-beat blood pressure data were collected continuously during each trial, and the relative changes in heart rate (ΔHR), mean arterial pressure (ΔMAP), systolic blood pressure (ΔSBP), and diastolic blood pressure (ΔDBP) were compared between conditions and across trials using analyses of variance with repeated measures. RESULTS: Phase IIa ΔSBP responses were significantly blunted during T3 compared to T1 in the supine condition (+6 ± 3 ΔmmHg, P=0.03), and ΔMAP, ΔSBP, and ΔDBP responses were significantly augmented during T1 in the seated condition compared to T1 in the supine condition (-9 ± 2 ΔmmHg, -15 ± 4 ΔmmHg, -8 ± 2 ΔmmHg, respectively, all P<0.01). However, no significant differences were observed for ΔMAP, ΔSBP, or ΔDBP between T3 in the seated condition compared to T1 in the supine condition (-6 ± 3 ΔmmHg, -8 ± 4 ΔmmHg, and -3 ± 2 ΔmmHg, respectively, all P>0.10), suggesting that handgrip mitigated the influence of orthostasis. No significant differences were observed for ΔHR responses during phase IIa for any comparison (all P>0.40). CONCLUSIONS: Handgrip blunts the phase IIa blood pressure responses to VLs performed in the supine condition, and also appears to mitigate the exaggerated phase IIa responses observed during orthostasis. This information has important implications for understanding the physiological factors contributing to abnormal VL responses in young healthy adults.

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