Endogenous Carboxyhemoglobin Concentrations in Predicting Prognosis of Patients with COVID-19 Pneumonia

The coronavirus disease 2019 (COVID-19) outbreak has caused great difficulties in providing healthcare services worldwide. Accurate and useful indicators are needed for the effective use of resources. Carbon monoxide (CO) is also produced endogenously without exogenous exposure. Studies confirm that endogenous CO increases in conditions such as pneumonia, sepsis, and trauma. This study aimed to compare patients diagnosed with COVID-19 pneumonia and healthy people to reveal whether endogenous carboxyhemoglobin (COHb) levels differ. It was also to determine whether it could be a helpful indicator for the clinician in predicting disease severity in combating the COVID-19 pandemic.

The study included 72 patients admitted to the hospital during the COVID-19 pandemic and diagnosed with COVID-19 pneumonia and a control group of 75 healthy people. The research data was collected retrospectively in a tertiary emergency department. The patients' demographic data, pneumonia severity index (PSI) score, CURB-65 score, 30-day mortality, hospitalization, need for mechanical ventilation (MV), and COHb levels were recorded.

While the COHb level was 0.9% (min-max, 0.1 - 4.0) in patients with COVID-19 pneumonia, it was 1% (min-max, 0.1 - 2.6) in the control group. No significant difference was found between the patients and the control group in terms of COHb levels (p = 0.341). Also, there was no correlation between COHb levels and PSI and CURB-65 scores. No significant difference was detected between COHb levels and patients diagnosed with COVID-19 pneumonia in terms of mortality, need for MV, or hospitalization (p > 0.05).

We concluded that COHb levels alone could not be used to diagnose COVID-19 pneumonia or predict disease severity. Besides, in COVID-19 pneumonia, the COHb level was not a useful indicator of mortality, need for MV, or hospitalization decision. Further studies are needed to find useful indicators to assist clinicians in their decision-making process in tackling the COVID-19 pandemic.