Use of alveolar carbon monoxide measurements to assess red blood cell survival in hemodialysis patients

We recently described a simple technique for measuring RBC survival based on measurements of the concentration of carbon monoxide (CO) in alveolar air, corrected for environmental CO using a device that equilibrates with atmospheric CO at the same rate as does the patient. The purpose of the present report is to demonstrate the clinical utility of this method via measurements of RBC turnover in hemodialysis patients. Prior to dialysis, the mean RBC survival of 9 chronic dialysis patients was 70 +/- 9 days, about 50% shorter than that of 32 healthy subjects. During the dialysis, the endogenous PCO increased by 14% (P < 0.05) while subjects not undergoing dialysis had a 6% fall in endogenous PCO over this same time period. Thus, this technique demonstrated that the hemodialysis procedure resulted in about a 20% increase in RBC destruction. This increased RBC destruction has not been detectable with previous methodologies (including conventional measurements of CO production) due to the insensitivity and lack of reproducibility of conventional techniques. We conclude that the simple, non-invasive measurement of endogenous PCO provides the most accurate available means of assessing the influence of a variety of acute manipulations on RBC survival.