Implications of Using Diffusing Capacity for Carbon Monoxide Correction with Haemoglobin Value for Evaluation of Severity Impairment of Stable Obese and Non-Obese Copd Patients

Abstract

We study the implication of using diffusing capacity for carbon monoxide (DLCO) measured to a standard haemoglobin concentration (14.6 g/dl for men and 13.6 g/dl for women) versus DLCO corrected by haemoglobin concentration for diffusion severity impairment in stable COPD (Chronic Obstructive Pulmonary Disease) patients. Subjects and methods: 187 patients with stable COPD (87.7% males) age 61± 5 years (mean ± standard deviation), underwent during 2002-2006 to: spirometry, bodypletismography, electrocardiography, DLCO measurement. We use BMI (body mass index) in order to classify patients in four groups according to BMI: 1. underweight (< 20, n = 25), 2. normal weight (20-24, n = 74), 3. overweight (25-29.9, n = 37), 4. obese (greater than or equal with 30, n = 51), n = number of patients. We used the equations of Cotes and co-workers to correct DLCO for haemoglobin concentration (Hb) for men and women. We consider DLCO < 40 percent of predicted value as cut-off for severity impairment. We found that DLCO in obese and anaemic COPD patients is underestimating without adjusting DLCO for Hb value. There was a significant difference for DLCO impairment using standard versus corrected values for Hb in groups 2, 3, 4 (p<0.0001). Even we found severe decreased in DLCO values (39.3+/-5.7) for underweight patients, there was no significant difference for evaluate DLCO severity using corrected and uncorrected for Hb level in this group. Corrected DLCO value for Hb provides better assessment of severity impairment for DLCO than DLCO for standard Hb value in COPD patients with different nutritional status.