Introduction
After appearing in Wuhan, China in December 2019, coronavirus disease
(COVID-19) spread rapidly around the world, with over 3 million
confirmed cases by the end of April 2020. In the majority of infected
patients, COVID-19 is either asymptomatic or presents with mild symptoms
such as loss of taste and smell, sore throat, fatigue, and joint pain.
However, it can have a much more severe course in older people, patients
with hypertension (HT), and conditions that can impair immunity such as
diabetes mellitus (DM), HIV, long-term immunosuppressive therapy, and
pregnancy 1.
While many comorbidities have been associated with COVID-19 mortality,
there are also laboratory diagnostic tests associated with early poor
prognosis. Of these, the most frequently used parameters are D-dimer,
ferritin, leukopenia, fibrinogen, prothrombin time, and IL-6 level.
These parameters alone are not effective in directing treatment, but
evaluation of correlation with clinical condition revealed a
relationship with macrophage activation syndrome (MAS), which is among
the most important causes of mortality. This led to the investigation of
parameters that can be associated with mortality in this emerging
disease 2,3.
Carbon monoxide (CO) is naturally synthesized in the body and plays an
important role in the regulation of physiological functions such as
vasodilation, angiogenesis, vascular remodeling, protection against
tissue damage, and modulation of the inflammatory response.
Approximately 85% of CO is produced by heme oxygenase and is excreted
from the body through the respiratory system 4,5. In
critical diseases such as acute respiratory failure, chronic obstructive
pulmonary disease, acute pulmonary embolism, and acute myocardial
infarction, low initial endogenous carboxyhemoglobin (COHb) level has
been associated with high mortality and poor prognosis . The leading
causes of morbidity and mortality in COVID-19 are acute respiratory
failure, microthombi, and cardiac involvement 5-8.
COVID-19 is a new disease that does not have specific laboratory
findings as in other known diseases, and as such is the focus of intense
research. The aim of the present study was to determine the value of
COHb levels measured at admission and follow-up in the prediction of
clinical course and prognosis in COVID-19 patients who develop MAS and
acute respiratory failure.