Study of diffusion capacity of lung for carbon monoxide (DLCO) in chronic obstructive pulmonary disease

 

Mamata Heda¹, Shivam Puniani², Pankaj Wagh², Jigneshkumar Patel^2*

 

Abstract              Background:  The most useful test of the gas exchange capacity of the lung that correlates with the total functioning surface area of alveolar capillary interface is the DLCO. Aims and Objectives: To Study Diffusing Capacity of Lung for Carbon Monoxide (DLCO) in Patients with COPD. Material and Methods: A study was done with 115 patients in the Department of Respiratory Medicine in a tertiary care centre. Results: Majority of the patients (39.9%) were in the age group of 61-70 years with male pre-ponderance(71.3%). It was observed that 50.4% patients had COPD Gold Grade III followed by 26.1% patients were COPD Gold Grade II, 20.9% patients with COPD Gold Grade IV and 2.6% with COPD Gold Grade I. Majority of the patients (18.8%) had ≥20 pack-year history and DLCO 40-60%. Conclusion: We concluded that as the COPD severity advances there was significant decline in  DLco.

Key Words: COPD, Spirometry, DLco.

 

INTRODUCTION

Chronic obstructive pulmonary disease (COPD) is a major cause of morbidity and mortality across the globe. According to World Health Organization estimates, 65 million people have moderate to severe COPD. More than 3 million people died of COPD in 2005 corresponding to 5% of all deaths globally and it is estimated to be the third leading cause of death by 2030 ¹. In India NCDs were estimated to have accounted for 53% of all deaths and 44% of disability-adjusted life-years (DALYs) lost in 2005. Of these chronic respiratory disease accounted for 7% deaths and 3% DALYs lost². Crude estimates suggest there are 30 million COPD patients in India³.India contributes a significant and growing percentage of COPD mortality which is estimated to be amongst the highest in the world; i.e. more than 64.7 estimated age standardized death rate per 100,000 amongst both sexes. This would translate to about 556,000 in case of India (>20%) out of a world total of 2,748,000 annually. The reported prevalence estimates have ranged from 2 to 22% in men and from 1.2 to 19% in women^4.Smoking is by far recognized to be the most important risk factor for development of COPD. Smoking behaviors in India are also peculiar with a large number of people using nonconventional form of tobacco in hookah, bidi, or chillum^5-6. More than one-half of the world's households uses biomass fuels and a significant proportion of this activity takes place in conditions where much of the effluent is released into the indoor living area⁷. To evaluate the severity of chronic obstructive pulmonary disease (COPD), a number of measurements are required. These include spirometry, including forced expiratory volume during the first second (FEV1), forced vital capacity (FVC), and the ratio between these two measurements (FEV1/FVC)⁸. Spirometry measures are supplemented by evaluation of dyspnea using, for example, the modified Medical Research Council (mMRC) score⁹ and considerations of the number of exacerbations in the preceding year. These figures allow stratification of the patient using the combined risk assessment score for COPD (GOLD score) as recommended by the Global Initiative for Chronic Obstructive Lung Disease (GOLD)¹⁰. The most useful test of the gas exchange capacity of the lung that also correlates with the total functioning surface area of alveolar capillary interface is the DLCO. Hence the present observational study is done to observe that DLco being a good additional parameter to conventional spirometry but not much has been studied according to the severity of COPD patients which will ultimately be useful in defining the Prognosis and treatment of the disease.

 

AIMS AND OBJECTIVES

1. To study Diffusing Capacity of Lung For Carbon Monoxide (DLCO) in Patients with Chronic Obstructive Pulmonary Disease
2. The correlation of DLCO with severity of airway obstruction according to GOLD guidelines.

 

MATERIAL AND METHODS

An institutional based observational study was undertaken with 115 patients in the Department of Respiratory Medicine in a tertiary care centre of a Medical College. The study duration was 1 ½ year. Considering the Prevalence of COPD as 7.7% with Absolute precession 5%, Power 80% calculated Sample Size was 115¹¹. All Patients of Chronic Obstructive Pulmonary Disease according to GOLD (Global Initiative for chronic Obstructive Lung Diseases) Criteria visiting OPD/IPD of Dept of Respiratory Diseases of our tertiary centre were included in the study. All patients with Pulmonary Tuberculosis, patients with chest x-ray showing parenchymal lesion, patients with recent Myocardial Infarction, hemoptysis of unknown origin, patient with recent eye surgery were excluded from the study. The clinical symptom consisted of breathlessness. The enrolled patients were subjected to a protocol, which included detailed recording of history regarding mode of onset and duration of illness, complete physical examination, routine investigations like CBC, ESR, RBS, HIV, Hbs Ag, ECG and chest x ray.

 

OBSERVATIONS AND RESULTS

The mean age of the patients was 60.57±8.78 years. There was male preponderance (71.3%) in the study while 60% of patients were smokers while 40% patients were non-smokers. There was no significant association of DLCO with Smoking Pack Years as per Chi-Square test (p>0.05). There was no significant difference in the post vital capacity parameters of patients as per Student t-test (p>0.05) in relation to DLco(Table 1) and also no significant difference was found in post (MEF 25–75) parameters of patients as per Student t-test (p>0.05)(Table 4). There was significant difference seen in the post FEV1 parameters as per Student t-test (p<0.05) (Table 2) and post FEV1/FVC parameters of patients in relation to DLCO as per Student t-test (p<0.05) (Table 3). In the present study, higher Residual Volume (RV) and Residual Volume/Total Lung Capacity (RV/TLC) was observed.

 

 

 

 

 

 

 

 

 

 

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