Correlation Between Blood Carboxyhemoglobin Levels and Smoking

Introduction: Carbon monoxide (CO) competes with oxygen (O2) for the same hemoglobin binding points. This substance has 210 times greater affinity than that of O2. CO poisoning is a frequent cause of death in many cases of individuals with intoxication. Chronic inhalation even at low concentrations can cause health issues as cardiological and neurological problems. Carboxyhemoglobin (COHb) levels in the blood should be less than 2.5%, but in smokers it can increase to 10%. In addition to tobacco, CO inhalation in the home or other environments can be a reason for its elevation. Our objective is to evaluate the relationship between COHb levels and tobacco consumption. Material and methods A cross-sectional, descriptive study, evaluating arterial blood gases (ABG) results performed during june and july 2021 in a lung function lab of a tertiary university hospital. Patients with respiratory failure (pO2 < 60mmHg) and using home oxygen therapy were excluded. Results: Total sample size was 86 patients, mean age of 71.7 years (+/−14) and 59.3% male. Based on tobacco history 41.9% were non-smokers, 10.5% were active smokers, and 47.7% were ex-smokers. COHb levels between these groups was analyzed, establishing 2.5% COHb in arterial blood as the cut-off point, based on previous studies. Thus, it was possible to objectify how blood COHb levels are higher among smokers (89%) than among non-smokers (13,9%), being this difference statistically significant (p<0.01). Conclusions: COHb levels were higher among subjects with a smoking habit. This results can alter interpretation of the lung diffusion measurement among smokers, so measuring these levels can help improve the interpretation of this test.