Rates of carbon monoxide elimination in males and females

Abstract

The purpose of this study was to verify the previously reported shorter half‐time of elimination (t½) of carbon monoxide (CO) in females compared to males. Seventeen healthy subjects (nine men) completed three sessions each, on separate days. For each session, subjects were exposed to CO to raise the carboxyhemoglobin percentage (COHb) to ~10%; then breathed in random order, either (a) 100% O2 at poikilocapnia (no CO2 added), or (b) hyperoxia while maintaining normocapnia using sequential gas delivery, or (c) voluntary hyperpnea at~4x the resting minute ventilation. We measured minute ventilation, hemoglobin concentration [Hb] and COHb at 5 min intervals. The half‐time of reduction of COHb (t½) was calculated from serial blood samples. The total hemoglobin mass (HbTOT) was calculated from [Hb] and estimated blood volume from a nomogram based on gender, height, and weight. The t½ in the females was consistently shorter than in males in all protocols. This relationship was sustained even after controlling for alveolar ventilation (P <0.05), with the largest differences in t½ between the genders occurring at low alveolar ventilation rates. However, when t½ was further normalized for HbTOT, there was no significant difference in t½ between genders at alveolar ventilation rates between 4 and 40 L/min (P =0.24). We conclude that alveolar ventilation and HbTOT are sufficient to account for a major difference in CO clearance between genders under resting (nonexercising) conditions.

Replicating measurements of total hemoglobin mass (tHb-mass) within a single day: precision of measurement; feasibility and safety of using oxygen to expedite carbon monoxide clearance

“…In a study examining this gender differences in CO t 1/2 disappeared when tHb‐mass was normalized suggesting that CO storage explained much of the difference (Zavorsky et al. ). Due to the low number of female subjects within the study it is impossible to conclude further than this.…”

Factors Contributing to CO Uptake and Elimination in the Body: A Critical Review

“…The results showed that women had a shorter half-life of CO elimination than men. The factors found to influence the rate of CO elimination were V A and total haemoglobin mass [20].…”

“…In many disease-related studies, we could find demographic factors that may be relevant to the disease [17,18]. In some studies, age and sex were reported to relate to the rate of CO uptake and elimination [19,20].…”

“…However, a high ventilation rate can also exhale more CO than a low ventilation rate over the same duration [1,13]. In a study by Zavorsky et al (2014), the results showed that men have a more prolonged washout time of CO than women, and the authors tried to explain the result. After they tested different factors in the subjects, they found that the alveolar ventilation and total haemoglobin mass may be the reasons that explain the difference in the CO half-life.…”

“…After they tested different factors in the subjects, they found that the alveolar ventilation and total haemoglobin mass may be the reasons that explain the difference in the CO half-life. When people have increased alveolar ventilation, the CO elimination time decreases [20].…”