Middle cerebral artery blood velocity during intense static exercise is dominated by a Valsalva maneuver

Abstract

Lifting of a heavy weight may lead to "blackout" and occasionally also to cerebral hemorrhage, indicating pronounced consequences for the blood flow through the brain. We hypothesized that especially strenuous respiratory straining (a Valsalva-like maneuver) associated with intense static exercise would lead to a precipitous rise in mean arterial and central venous pressures and, in turn, influence the middle cerebral artery blood velocity (MCA V(mean)) as a noninvasive indicator of changes in cerebral blood flow. In 10 healthy subjects, MCA V(mean) was evaluated in response to maximal static two-legged exercise performed either with a concomitantly performed Valsalva maneuver or with continued ventilation and also during a Valsalva maneuver without associated exercise (n = 6). During static two-legged exercise, the largest rise for mean arterial pressure and MCA V(mean) was established at the onset of exercise performed with a Valsalva-like maneuver (by 42 +/- 5 mmHg and 31 +/- 3% vs. 22 +/- 6 mmHg and 25 +/- 6% with continued ventilation; P < 0.05). Profound reductions in MCA V(mean) were observed both after exercise with continued ventilation (-29 +/- 4% together with a reduction in the arterial CO(2) tension by -5 +/- 1 Torr) and during the maintained Valsalva maneuver (-21 +/- 3% together with an elevation in central venous pressure to 40 +/- 7 mmHg). Responses to performance of the Valsalva maneuver with and without exercise were similar, reflecting the deterministic importance of the Valsalva maneuver for the central and cerebral hemodynamic response to intense static exercise. Continued ventilation during intense static exercise may limit the initial rise in arterial pressure and may in turn reduce the risk of hemorrhage. On the other hand, blackout during and after intense static exercise may reflect a reduction in cerebral blood flow due to expiratory straining and/or hyperventilation.

Inconsistent detection of changes in cerebral blood volume by near infrared spectroscopy in standard clinical tests

“…In fact, it is interesting to observe that, while TOIe was significantly increased (cheek level), TOIi consistently decreased at intracranial level. This is at variance with other studies (34,36) in which a paradoxical increase in cerebral oxygenation was detected by BL-based NIRS. The VM-induced increase in central venous and intracranial pressures produces a decrease in cerebral perfusion pressure that impairs cerebral blood flow (10,46).…”

“…In fact, cerebral blood volume can increase only if cerebrospinal fluid volume decreases (total volume of the cranium cannot change); however, both central venous pressure and central spinal fluid pressure are increased during the maneuver (22,24,33). A number of studies, employing BL-based NIRS, report increased cerebral blood volume and oxygenation during VM (34,36,49). We also consistently observed an increase in tHbi (100% of cases); however, THIi decreased in 46% of subjects.…”

Trigger Factors and Their Attributable Risk for Rupture of Intracranial Aneurysms

“…[19][20][21][22][23][24]. Результаты насто-ящего исследования подтверждают мнение, что вне-запное и кратковременное повышение артериально-го давления в результате повседневной деятельности является характерным патофизиологическим меха-низмом разрыва аневризмы.…”

Application of near-infrared spectroscopy in clinical neurology

“…[23][24][25][26] Many studies have investigated the use of NIRS to reveal the pathophysiology of patients with OI. [27][28][29][30][31] NIRS offers an alternative solution for understanding the effects of a dysregulated autonomic nervous system on the delivery of blood to the brain. In addition, NIRS can potentially be used to monitor patients with inconclusive blood-pressure or heart-rate readings.…”