Togores B, Bosch M, Agustí A G
Servei Pneumologá, Hospital Universitari Soil Dureta, Palma, Mallorca.
Eur Respir J. 2000 Jan;15(1):177-80. doi: 10.1183/09031936.00.15117700.
The concentration of carboxyhaemoglobin (COHb) is often estimated from measurements of carbon monoxide in the exhaled air (COexh). This study investigates whether the presence of airflow obstruction significantly alters the relationship between COexh and COHb. Eighty-one regular smokers were prospectively studied and divided in four groups according to the presence and severity of airflow obstruction (none, mild, moderate, severe). In each subject, the authors measured in this order: 1) arterial blood gases; 2) haemoglobin concentration and COHb (by co-oxymetry); 3) COexh; 4) lung volumes; and 5) forced spirometry. The size of the measurement error (deltaCO) was calculated from the difference between COHb and COexh. Neither the smoking history nor COexh were different in the four groups of subjects studied. In contrast, deltaCO increased in parallel to the degree of airflow obstruction. DeltaCO was >2% (a threshold value normally used in the clinic to separate smokers from nonsmokers) only in patients with severe airflow obstruction. A stepwise multivariate analysis showed that both forced expiratory volume in one second (FEV1) (percentage reference) and COHb contributed significantly (p<0.0001) to predict deltaCO. This study shows that the estimation of carboxyhaemoglobin from exhaled carbon monoxide measurements can be inaccurate in patients with severe airflow obstruction. In these patients, the direct measurement of carboxyhaemoglobin seems advisable in clinical practice.
碳氧血红蛋白（COHb）的浓度通常通过测量呼出气体中的一氧化碳（COexh）来估算。本研究调查气流阻塞的存在是否会显著改变COexh与COHb之间的关系。对81名经常吸烟的人进行了前瞻性研究，并根据气流阻塞的存在情况和严重程度分为四组（无、轻度、中度、重度）。在每个受试者中，作者按此顺序进行测量：1）动脉血气；2）血红蛋白浓度和COHb（通过共血氧测定法）；3）COexh；4）肺容积；5）用力肺活量测定。测量误差大小（deltaCO）通过COHb与COexh之间的差值计算得出。在研究的四组受试者中，吸烟史和COexh均无差异。相比之下，deltaCO随着气流阻塞程度的增加而平行升高。仅在严重气流阻塞的患者中，deltaCO>2%（临床上通常用于区分吸烟者与非吸烟者的阈值）。逐步多变量分析表明，一秒用力呼气量（FEV1）（占预计值百分比）和COHb均对预测deltaCO有显著贡献（p<0.0001）。本研究表明，在严重气流阻塞的患者中，通过测量呼出一氧化碳来估算碳氧血红蛋白可能不准确。在这些患者中，临床实践中直接测量碳氧血红蛋白似乎是可取的。
