The clinical usefulness of a screening test to detect static pulmonary blood using a multiple-breath analysis of diffusing capacity.
We devised a screening test to detect static blood in the lungs (e.g., with pulmonary vascular obstruction or pulmonary hemorrhage). A back pressure to CO will develop in static blood as the concentration of carboxyhemoglobin increases with time, and diffusing capacity (DLCO) will decrease. Instead of obtaining a single value for DLCO, we calculated DLCO over small decrements of the exhaled vital capacity during 4 sequential breaths using a modification of a method developed in our laboratory. In each of 5 healthy subjects there was no difference in DLCO during the 4 sequential breaths in the sitting, supine, or lateral decubitus positions. However, in a patient with a proved pulmonary embolus, DLCO decreased with sequential breaths, expecially at low lung volumes. In a patient with angiographic evidence of kinking of the left pulmonary artery when he assumed the right lateral decubitus position, DLCO showed a sequential decrease in this position only. Three patients with pulmonary hemorrhage also showed decreases in DLCO during sequential breaths during episodes of active bleeding.
D000328:Adult; D002248:Carbon Monoxide / Q000032:analysis; D002263:Carboxyhemoglobin / Q000032:analysis; D006470:Hemorrhage / Q000175:diagnosis* / Q000503:physiopathology; D006801:Humans; D008171:Lung Diseases / Q000175:diagnosis* / Q000503:physiopathology; D013058:Mass Spectrometry; D011655:Pulmonary Embolism / Q000175:diagnosis* / Q000503:physiopathology; D012044:Regression Analysis; D012129:Respiratory Function Tests / Q000295:instrumentation; D014109:Total Lung Capacity; D014797:Vital Capacity
D002248:Carbon Monoxide; D002263:Carboxyhemoglobin