Influence of upper body position on middle cerebral artery blood velocity during continuous positive airway pressure breathing

TY - JOUR

T1 - Influence of upper body position on middle cerebral artery blood velocity during continuous positive airway pressure breathing

AU - Højlund Rasmussen, J

AU - Mantoni, T

AU - Belhage, B

AU - Pott, F C

N1 - Keywords: Adult; Blood Flow Velocity; Continuous Positive Airway Pressure; Female; Humans; Male; Middle Cerebral Artery; Posture; Respiration; Respiratory Function Tests

PY - 2007

Y1 - 2007

N2 - Continuous positive airway pressure (CPAP) is a treatment modality for pulmonary oxygenation difficulties. CPAP impairs venous return to the heart and, in turn, affects cerebral blood flow (CBF) and augments cerebral blood volume (CBV). We considered that during CPAP, elevation of the upper body would prevent a rise in CBV, while orthostasis would challenge CBF. To determine the body position least affecting indices of CBF and CBV, the middle cerebral artery mean blood velocity (MCA V(mean)) and the near-infrared spectroscopy determined frontal cerebral hemoglobin content (cHbT) were evaluated in 11 healthy subjects during CPAP at different body positions (15 degrees head-down tilt, supine, 15 degrees, 30 degrees and 45 degrees upper body elevation). In the supine position, 10 cmH(2)O of CPAP reduced MCA V(mean) by 9 +/- 3% and increased cHbT by 4 +/- 2 micromol/L (mean +/- SEM); (P <0.05). In the head-down position, CPAP increased cHbT to 13 +/- 2 micromol/L but left MCA V(mean) unchanged. Upper body elevation by 15 degrees attenuated the CPAP associated reduction in MCA V(mean) (-7 +/- 2%), while cHbT returned to baseline (1 +/- 2 micromol/L). With larger elevation of the upper body MCA V(mean) decreased progressively to -17 +/- 3%, while cHbT remained unchanged from baseline. These results suggest that upper body elevation by approximately 15 degrees during 10 cmH(2)O CPAP prevents an increase in cerebral blood volume with minimal effect on cerebral blood flow.

AB - Continuous positive airway pressure (CPAP) is a treatment modality for pulmonary oxygenation difficulties. CPAP impairs venous return to the heart and, in turn, affects cerebral blood flow (CBF) and augments cerebral blood volume (CBV). We considered that during CPAP, elevation of the upper body would prevent a rise in CBV, while orthostasis would challenge CBF. To determine the body position least affecting indices of CBF and CBV, the middle cerebral artery mean blood velocity (MCA V(mean)) and the near-infrared spectroscopy determined frontal cerebral hemoglobin content (cHbT) were evaluated in 11 healthy subjects during CPAP at different body positions (15 degrees head-down tilt, supine, 15 degrees, 30 degrees and 45 degrees upper body elevation). In the supine position, 10 cmH(2)O of CPAP reduced MCA V(mean) by 9 +/- 3% and increased cHbT by 4 +/- 2 micromol/L (mean +/- SEM); (P <0.05). In the head-down position, CPAP increased cHbT to 13 +/- 2 micromol/L but left MCA V(mean) unchanged. Upper body elevation by 15 degrees attenuated the CPAP associated reduction in MCA V(mean) (-7 +/- 2%), while cHbT returned to baseline (1 +/- 2 micromol/L). With larger elevation of the upper body MCA V(mean) decreased progressively to -17 +/- 3%, while cHbT remained unchanged from baseline. These results suggest that upper body elevation by approximately 15 degrees during 10 cmH(2)O CPAP prevents an increase in cerebral blood volume with minimal effect on cerebral blood flow.

U2 - 10.1007/s00421-007-0513-9

DO - 10.1007/s00421-007-0513-9

M3 - Journal article

C2 - 17638008

SN - 1439-6319

VL - 101

SP - 369

EP - 375

JO - European Journal of Applied Physiology

JF - European Journal of Applied Physiology

IS - 3

ER -