Carotid blood velocity during cough studies in man.

Utilizing a Doppler ultrasonic flowmeter catheter, right carotid artery blood velocity was measured during 91 coughing episodes in 16 patients. Such coughing reduced carotid blood velocity by 40 +/- 22% (control = 34 +/- 8 cm per second, cough = 20 +/- 9 cm per second, p less than 0.001). There was an insignificant low degree of corrleation between the level of simultaneously recorded mean right pressure and the percent decline of peak carotid blood velocity, suggesting that impaired venous return was not the only factor responsible for the observed changes. It is concluded that (1)coughing diminishes phasic carotid blood velocity and (2)reduced cerebral perfusion may play a role in the pathogenesis of cough syncope.