Arterial, Cerebrospinal and Venous Pressures in Man during Cough and Strain1

It has been shown in scattered reports (1, 2, 3, 4) from this laboratory that sudden changes of intrathoracic and abdominal pressure such as occur in coughing and straining produce simultaneous changes in the arterial pressure and in cerebrospinal pressure. It was argued that whereas these pressure changes may strain the arteries of the arms, legs and skin, the more vital arteries of the thoracic and abdominal organs and of the central nervous system are protected against the extra strain made when the intrathoracic pressure goes up during a cough or strain. The use of the differential manometer (5) has enabled us to show in a simple graphic form the differences in pressure which bear upon the peripheral and vital arteries and to differentiate the effects of direct pressure propagation from the secondary pressure changes resulting from the effects of intrathoracic pressure upon blood flow. Technical difficulties make it hard to use the intrathoracic pressure itself to work a differential manometer. It is therefore assumed that the gross changes in the intrathoracic pressure are the same as those in the mouth when the lips and nose are closed and the glottis open. A sudden expulsive effort under these circumstances is thought to have the same effect on buccal and intrathoracic pressure and to simulate the effects of a cough upon the hemodynamics. A prolonged expiratory effort against the mouthpiece is proposed as having similar effects to a strain against a closed glottis as in a difficult bowel movement and breathing deeply through the mouthpiece against heavy resistance is thought to illustrate an exaggeration of the effects of breathing upon the blood pressure. On these assumptions the pressure relationships were recorded as follows. The manometer is of the usual differential type as described elsewhere (5). It is a simple hypodermic manometer (1) whose moving parts are enclosed in an air tight chamber fronted with an optically plane glass plate. The manometer is thus constructed to measure the difference between pressures rather than pressure per se. The buccal pressure is led from a mouthpiece to the front chamber and the arterial pressure is led in the usual way to the manometer itself. The upper record in figures 1, 2 and 3 is from the differential manometer and measures roughly the excess of the arterial pressure over the intrathoracic pressure. That is to say it measures the pressure which strains on the walls of the intrathoracic and intra-abdominal arteries. The middle record is made by a manometer which is connected by a leaden T tube to the same arterial needle