Capnography Is Not as Sensitive as Pulmonary Artery Pressure Monitoring in Detecting Marrow Microembolism

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Abstract
We studied several methods for detecting pulmonary embolic events in a model of fat and marrow microembolism during canine cemented arthroplasty procedures. The cardiopulmonary effects of bilateral cemented arthroplasty in this model include increased pulmonary artery pressure and pulmonary vascular resistance accompanying a decrease in arterial oxygen tension. We documented significant fat and marrow microembolism by postmortem quantitative morphometry of lung sections. Vessels occluded ranged in diameter from 0.5 to 190 microns. The acute increases in pulmonary artery pressure (PAP) (to 6.28 .+-. 4.4 mm Hg from 15.3 .+-. 3.3 mm Hg) after cemented arthroplasty were not detected by changes in continuously monitored end-tidal CO2 or in right atrial or arterial blood pressures. Although capnography is a useful intra-operative monitor, in this model it is less sensitive than PAP monitoring in detection of fat and marrow microemboli.