A fast responding intra-arterial pH electrode for use in the peripheral artery of adult humans and large mammals: a technical development for use in research

A rapidly responding intra-arterial pH electrode has been developed to provide a continuous record of arterial pH (pHa) in the radial artery of adult humans and large mammals. The current method for measuring pHa is discontinuous and is achieved by taking blood samples and subsequently measuring pHa in a blood gas analyser. The development of an intravascular electrode is needed for studies on the chemical control of pulmonary ventilation when a continuous record of pHa is required. It will be particularly useful in rapidly changing circumstances such as at the onset and termination of exercise and at sleep onset and arousal. The sensor of the electrode system described here consists of a pH sensitive plastic membrane adherent to the tip of a catheter. This catheter is threaded down a radial artery catheter and protrudes 2-3 mm into the arterial lumen. The electrode system has been used in patients in an intensive care unit and in patients undergoing sleep studies. No adverse complications have occurred. The records obtained showed that arterial pH faithfully followed changes in pulmonary ventilation.