Perry Blake G, Mündel Toby, Cochrane Darryl J, Cotter James D, Lucas Samuel J E
School of Sport and Exercise, Massey University, Palmerston North, New Zealand.
School of Physical Education, Sport and Exercise Sciences, University of Otago, Dunedin, New Zealand.
Physiol Rep. 2014 Feb 10;2(2):e00233. doi: 10.1002/phy2.233. eCollection 2014 Feb 1.
The Valsalva maneuver (VM) produces large and abrupt increases in mean arterial pressure (MAP) at the onset of strain (Phase I), however, hypotension, sufficient to induce syncope, occurs upon VM release (phase III). We examined the effect of VM intensity and duration on middle cerebral artery blood velocity (MCAv) responses. Healthy men (n =10; mean ± SD: 26 ± 4 years) completed 30%, 60%, and 90% of their maximal VM mouth pressure, for 5 and 10 sec (order randomized) while standing. Beat-to-beat MCAv and MAP during phase I (peak), at nadir (phase III), and recovery are reported as the change from standing baseline. During phase I, MCAv rose 15 ± 6 cm·s(-1) (P <0.001), which was not reliably different between intensities (P =0.11), despite graded increases in MAP (P <0.001; e.g., +12 ± 9 mmHg vs. +35 ± 14 for 5 sec 30% and 90% VM, respectively). During Phase III, the MCAv response was duration- (P = 0.045) and intensity dependent (P < 0.001), with the largest decrease observed following the 90% VM (e.g., -19 ± 13 and -15 ± 11 cm·s(-1) for 5 and 10 sec VM, respectively) with a concomitant decrease in MAP (P <0.001, -23 ± 11 and -23 ± 9 mmHg). This asymmetric response may be attributable to the differential modulators of MCAv throughout the VM. The mechanical effects of the elevated intrathoracic pressure during phase I may restrain increases in cerebral perfusion via related increases in intracranial pressure; however, during phase III the decrease in MCAv arises from an abrupt hypotension, the extent of which is dependent upon both the duration and intensity of the VM.
瓦尔萨尔瓦动作（VM）在用力开始时（I期）会使平均动脉压（MAP）大幅且突然升高，然而，在VM释放时（III期）会出现足以诱发晕厥的低血压。我们研究了VM强度和持续时间对大脑中动脉血流速度（MCAv）反应的影响。健康男性（n = 10；平均±标准差：26±4岁）站立时分别以其最大VM口腔压力的30%、60%和90%完成5秒和10秒（顺序随机）的动作。I期（峰值）、最低点（III期）和恢复期间的逐搏MCAv和MAP报告为相对于站立基线的变化。在I期，MCAv升高了15±6 cm·s⁻¹（P < 0.001），尽管MAP分级升高（P < 0.001；例如，5秒30%和90% VM时分别为+12±9 mmHg和+35±14 mmHg），但不同强度之间的MCAv升高并无显著差异（P = 0.11）。在III期，MCAv反应与持续时间有关（P = 0.045）且依赖于强度（P < 0.001），90% VM后观察到的下降最大（例如，5秒和10秒VM时分别为-19±13和-15±11 cm·s⁻¹），同时MAP也下降（P < 0.001，-23±11和-23±9 mmHg）。这种不对称反应可能归因于整个VM过程中MCAv的不同调节因素。I期胸腔内压力升高的机械效应可能通过颅内压的相关升高来抑制脑灌注的增加；然而，在III期，MCAv的下降源于突然的低血压，其程度取决于VM的持续时间和强度。
