Nitric oxide (NO) and carbon monoxide (CO) are synthesized at high levels in asthmatic airways. NO can oxidize hemoglobin (Hb) to methemoglobin (MetHb). CO binds to heme to produce carboxyhemoglobin (COHb). We hypothesized that MetHb and COHb may be increased in asthma. COHb, MetHb, and Hb were measured in venous blood of healthy controls (n = 32) and asthmatics (n = 31). Arterial COHb and oxyhemoglobin were measured by pulse CO-oximeter. Hb, oxyhemoglobin, and deoxyhemoglobin were similar among groups, but arterial COHb was higher in asthmatics than controls (p = 0.04). Venous COHb was similar among groups, and thus, arteriovenous COHb (a-v COHb) concentration difference was greater in asthma compared with controls. Venous MetHb was lower in asthma compared to controls (p = 0.01) and correlated to venous NO (p = 0.009). The greater a-v COHb in asthma suggests CO offloading to tissues, but lower than normal MetHb suggests countermeasures to avoid adverse effects of high NO on gas transfer.
This is a preview of subscription content, log in to check access.
We would like to thank Masimo for providing us with the loan of their equipment. This work is supported by HL099303, HL081064, HL103453, HL109250, and UL1 RR024989 from the National Center for Research Resources.
Conflict of interests
Nadeem A, Chhabra SK, Masood A et al (2003) Increased oxidative stress and altered levels of antioxidants in asthma. J Allergy Clin Immunol 111:72–78CrossRefPubMedGoogle Scholar
Brooks J (1937) The action of nitrite on haemoglobin in the absence of oxygen. Proc Royal Soc Lond B Biol Sci 123:368–382CrossRefGoogle Scholar
Maines MD (1997) The heme oxygenase system: a regulator of second messenger gases. Annu Rev Pharmacol Toxicol 37:517–554CrossRefPubMedGoogle Scholar
Zayasu K, Sekizawa K, Okinaga S et al (1997) Increased carbon monoxide in exhaled air of asthmatic patients. Am J Respir Crit Care Med 156:1140–1143CrossRefPubMedGoogle Scholar
Horvath I, Loukides S, Wodehouse T et al (1998) Raised levels of exhaled carbon monoxide are associated with an increased expression of heme oxygenase-1 in airway macrophages in asthma: a new marker of oxidative stress. Thorax 53:668–672CrossRefPubMedCentralPubMedGoogle Scholar
Yasuda H, Sasaki T, Yamaya M et al (2004) Increased arteriovenous carboxyhemoglobin differences in patients with inflammatory pulmonary diseases. Chest 125:2160–2168CrossRefPubMedGoogle Scholar
Otterbein LE, Choi AM (2000) Heme oxygenase: colors of defence against cellular stress. Am J Physiol Lung Cell Mol Physiol 279:L1029–L1037PubMedGoogle Scholar
Ryter S, Alam J, Choi AM (2006) Heme oxygenase/carbon monoxide: from basic science to therapeutic applications. Physiol Rev 86:583–650CrossRefPubMedGoogle Scholar
Antonini E, Brunori M (1971) Hemoglobin and myoglobin in their reactions with ligands. North-Holland, AmsterdamGoogle Scholar
Kaneko FT, Arroliga AC, Dweik RA et al (1998) Biochemical reaction products of nitric oxide as quantitative markers of primary pulmonary hypertension. Am J Respir Crit Care Med 158:917–923CrossRefPubMedGoogle Scholar