Carbon monoxide in exhaled breath testing and therapeutics

Abstract

Carbon monoxide (CO), a low molecular weight gas, is a ubiquitous environmental product of organic combustion, which is also produced endogenously in the body, as the byproduct of heme metabolism. CO binds to hemoglobin, resulting in decreased oxygen delivery to bodily tissues at toxicological concentrations. At physiological concentrations, CO may have endogenous roles as a potential signaling mediator in vascular function and cellular homeostasis. Exhaled CO (eCO), similar to exhaled nitric oxide (eNO), has been evaluated as a candidate breath biomarker of pathophysiological states, including smoking status, and inflammatory diseases of the lung and other organs. eCO values have been evaluated as potential indicators of inflammation in asthma, stable COPD and exacerbations, cystic fibrosis, lung cancer, or during surgery or critical care. The utility of eCO as a marker of inflammation, and potential diagnostic value remains incompletely characterized. Among other candidate “medicinal gases” with therapeutic potential, (e.g., NO and H2S), CO has been shown to act as an effective anti-inflammatory agent in preclinical animal models of inflammatory disease, acute lung injury, sepsis, ischemia/reperfusion injury and organ graft rejection. Current and future clinical trials will evaluate the clinical applicability of this gas as a biomarker and/or therapeutic in human disease.

Real-time breath gas analysis of CO and CO2 using an EC-QCL

“…Endogenous carbon monoxide (CO) is a by-product of systemic heme oxygenase and thus considered a potential marker for oxidative stress, inflammation and respiratory diseases [28]. Most of the CO is bound to blood hemoglobin and released via the breath following gas exchange at the alveolar interface.…”

Assessment of exhaled carbon monoxide in exacerbations of chronic obstructive pulmonary disease

“…In our study, smokers had slightly lower eCO levels than these values, which could be explained by reduced smoking frequency of the patients prior hospitalization due to their poor clinical status and severe dyspnea. Endogenously produced CO diffuses to the blood where it is transported by hemoglobin in the form of HbCO and is released to the alveolar space during gas exchange (9,25). Therefore, the measurement of blood HbCO concentration may also be a marker to monitor the severity of local and/or systemic oxidative stress in a wide variety of pulmonary and extrapulmonary diseases.…”

“…One of the simple gases present in the exhaled breath that has been suggested to reflect ongoing oxidative stress and/or airway inflammation is carbon monoxide (CO) (9,25). The measurement of exhaled CO (eCO) is a brief non-invasive procedure that provides immediate results, and is most commonly measured with electrochemical technology.…”

Does the Finding of Small Airway Obstruction in Pulmonary Function Tests Effect End-Expiratory Carbonmonoxide Level?

“…CO is absorbed through smoking or can be produced endogenously in alveolar macrophages, endothelial cells, and other lung cells as a product of local inflammation and oxidative stress in individuals with airway diseases (1). In many studies, it was revealed that the end-expiratory CO (exhaled CO) level was higher in patients with severe asthma and lower in asthma patients receiving inhaled steroid therapy than in those not having therapy (2)(3)(4).…”

“…In many studies, it was revealed that the end-expiratory CO (exhaled CO) level was higher in patients with severe asthma and lower in asthma patients receiving inhaled steroid therapy than in those not having therapy (2)(3)(4). Therefore, the exhaled CO level has recently begun to be used as an inflammatory biomarker in airway diseases such as asthma, chronic obstructive pulmonary disease (COPD), cystic fibrosis, and bronchiectasis (1,5). However, it was concluded in some studies that the exhaled CO level could not be used routinely as a biomarker in patients with asthma and cystic fibrosis because no relationship was found between the exhaled CO level and airflow limitations (6,7).…”