Jean-Jacques Moraine

Effects of High Altitude Exposure on Cerebral Hemodynamics in Normal Subjects

Background and Purpose— Acute mountain sickness (AMS) may be an early stage of high altitude cerebral edema. If so, AMS could result from an alteration of dynamic autoregulation of cerebral blood flow resulting in overperfusion of capillaries and vasogenic cerebral edema. Methods— We measured middle cerebral artery blood flow velocity (Vmca) by transcranial Doppler and arterial blood pressure by finger plethysmography at 490 m and 20 hours after arrival at 4559 m in 35 volunteers who had been randomized to tadalafil, dexamethasone, or placebo in a study on the pharmacological prevention of high altitude pulmonary edema. A dynamic cerebral autoregulation index (ARI) was calculated from continuous recordings of Vmca and blood pressure during transiently induced hypotension. Results— Altitude was associated with an increase in a cerebral-sensible AMS (AMS-C) score (P<0.001) and with a decrease in arterial oxygen saturation (Sao2), whereas average Vmca or ARI did not change. However, at altitude, the subjects with the lowest ARI combined with the lowest Sao2 presented with the highest AMS-C score (P<0.03). In addition, a stepwise multiple linear regression analysis on arterial Pco2, Sao2, and baseline or altitude ARI identified altitude ARI as the only significant predictor of the AMS-C score (P=0.01). The AMS-C score was lower in dexamethasone-treated subjects compared with high altitude pulmonary edema–susceptible untreated subjects. Neither tadalafil nor dexamethasone had any significant effect on Vmca or ARI. Conclusions— High altitude hypoxia is associated with impairment in the regulation of the cerebral circulation that might play a role in AMS pathogenesis.

Relationship of middle cerebral artery blood flow velocity to intensity during dynamic exercise in normal subjects

SummaryCerebral blood flow has been reported to increase during dynamic exercise, but whether this occurs in proportion to the intensity remains unsettled. We measured middle cerebral artery blood flow velocity (νm) by transcranial Doppler ultrasound in 14 healthy young adults, at rest and during dynamic exercise performed on a cycle ergometer at a intensity progressively increasing, by 50 W every 4 min until exhaustion. Arterial blood pressure, heart rate, end-tidal, partial pressure of carbon dioxide (PETCO2), oxygen uptake (

Doppler assessment of hypoxic pulmonary vasoconstriction and susceptibility to high altitude pulmonary oedema.

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Dobutamine increases cerebral blood flow velocity and jugular bulb hemoglobin saturation in septic patients.

O2) and carbon dioxide output were determined at exercise intensity. Mean vM increased from 53 (SEM 2) cm · s−1 at rest to a maximum of 75 (SEM 4) cm · s−1 at 57% of the maximal attained

Near-Infrared Fluorescence Lymphatic Imaging to Reconsider Occlusion Pressure of Superficial Lymphatic Collectors in Upper Extremities of Healthy Volunteers

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Cerebral CO2 vasoreactivity evaluation with and without changes in intrathoracic pressure in comatose patients

O2(