AN OBJECTIVE METHOD FOR DETERMINING CIRCULATION TIME FROM PULMONARY TO SYSTEMIC CAPILLARIES BY THE USE OF THE OXIMETER

Abstract

Use of the oximeter for noting instantaneous changes in the arterial O2 saturation in the fully flushed human ear has made possible the direct detn. of lung to ear circulation time. A single deep inhalation of N displaces sufficient O2 from the alveolar air to interfere momentarily with O2 uptake by the blood passing through the lung. When this unsaturated blood reaches the ear the oximeter galvanometer is deflected. The circulation time is taken as the interval between the sharp inspiration of N and the galvanometer deflection. Cooperation of the subject is necessary only to the extent of his taking a deep breath following a maximum expiration. A single breath of 100% N has produced no untoward reaction in more than 100 subjects. In 35 subjects without known heart or lung disease the circulation time varied from 4.1-7.0 secs., for an avg. value of 5.2 sec. The values for 23 subjects (66%) were in the range of 4.6-5.5 sec. Repeated trials in one individual varied by 0.1 sec. in the least variable individual and by 1.8 sec. in the most variable one. The lung to ear circulation time by this method is shorter and less variable than when estimated by subtraction of arm to lung circulation time (ether, paralde-hyde) from arm to head circulation time (decholin, calcium, cyanide).