TY - JOUR T1 - Alveolar carbon monoxide: a comparison of methods of measurement and a study of the effect of change in body posture. AU - Kirkham,A J, AU - Guyatt,A R, AU - Cumming,G, PY - 1988/1/1/pubmed PY - 1988/1/1/medline PY - 1988/1/1/entrez SP - 23 EP - 8 JF - Clinical science (London, England : 1979) JO - Clin Sci (Lond) VL - 74 IS - 1 N2 - 1. We have compared rebreathing, breath-hold and mean alveolar methods of measuring alveolar carbon monoxide (CO), at levels similar to those found in smokers, as a preliminary to using them as indirect measures of carboxyhaemoglobin levels. In the present study alveolar CO levels were raised by rebreathing a 2% CO mixture. 2. Breath-hold CO was measured after breath-hold times of 0-35 s in 5 s increments. Using generalized linear models, the maximum value for breath-hold CO was estimated to occur at 23 s. Breath-hold CO after a 20 and 25 s breath-hold were similar to and significantly greater than those of less than 20 s or greater than 25 s. 3. As expired CO increased, the difference between breath-hold and mean alveolar CO became proportionally larger. On average, breath-hold CO was 24% larger than mean alveolar CO. 4. Rebreathing, breath-hold and mean alveolar CO were compared at four different inspired oxygen concentrations. Expired CO increased significantly with increasing oxygen for all three methods. At end-tidal oxygen levels of less than 25%, breath-hold and rebreathing CO were similar, however, the overall mean difference between the three methods was significant. 5. While rebreathing CO was unaffected by changes in ventilation/perfusion of the lung, induced by change in body posture, both breath-hold and mean alveolar CO showed a significant fall with change from the supine to erect posture.(ABSTRACT TRUNCATED AT 250 WORDS) SN - 0143-5221 UR - https://www.unboundmedicine.com/medline/citation/3338251/Alveolar_carbon_monoxide:_a_comparison_of_methods_of_measurement_and_a_study_of_the_effect_of_change_in_body_posture_ DB - PRIME DP - Unbound Medicine ER -