Can End-tidal Carbon Dioxide Levels Be Used for Determining Tissue Oxygen Saturation in Smokers and Nonsmokers?

J Clin Exp Invest 2019;10(1):em00720.


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Objectives: End-tidal carbon dioxide (EtCO2) monitoring has been used in a range areas, such as invasive sedation procedures, during cardiopulmonary resuscitation, ventilation monitoring of patients with altered mental status, trauma and respiratory system diseases in emergency departments. Near-infrared spectroscopy (NIRS) allows continuous, noninvasive measurement of tissue hemoglobin oxygen saturation (StO2) in muscle and has been studied for a wide range of conditions.
In this study we aim to determine the levels of EtCO2 and StO2 in smokers and nonsmokers and the relationship between these two parameters.
Methods: We examined 201 healthy volunteers including 156 smokers and 45 nonsmokers. We measured thenar muscle StO2 via NIRS device. The EtCO2 was determined by a capnograph. Baseline measurements were obtained from all participants after not-smoking for two h. Second measurements were taken 5 min after smoking was finished.
Results: The mean baseline EtCO2 of the smoker group was 42.61±4,94 (min:31, max:54) mmHg and mean baseline StO2 for this group was 77.81±4.71% (min:69, max:86). In smokers, mean baseline EtCO2 (p:0.00), baseline StO2 (p:0.001), fifth min EtCO2 (p:0.00), fifth min StO2 (p:0.02) levels, and pack*year (p:0.00) were significantly different between males and females. In nonsmokers baseline EtCO2 and baseline StO2 levels were correlated (p:0.035,r:0.315). But we couldn’t find significance between females and males for mean baseline EtCO2 (p:0,246) and baseline StO2 (p:0.264) levels in this group.
Conclusion: Smoking affects tissue oxygenation. In nonsmokers baseline EtCO2 and baseline STO2 levels were correlated, but there was no correlation for these two parameters in smokers. Clinicians may use EtCO2 levels for predicting the tissue oxygenation in nonsmoker patients.


end-tidal carbon dioxide, near-infrared spectroscopy, tissue hemoglobin oxygen saturation, smoker, nonsmoker


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Yolcu S, Kaya A. Can End-tidal Carbon Dioxide Levels Be Used for Determining Tissue Oxygen Saturation in Smokers and Nonsmokers?. J Clin Exp Invest. 2019;10(1):em00720.