A study of correlation of pulmonary function test with BMI in the patients with coronary artery disease

 

Prashant D Purkar¹, Mohd Amir Khan^2*, S T Nabar³, Ashana Rafique Parbalkar⁴

 

¹Associate Professor, ²Sr. Resident, ³Professor, ⁴Intern, Department of Medicine, Dr. D Y Patil Medical College, Navi Mumbai, Maharashtra, INDIA.

Email: prashpurkar@gmail.com

 

Abstract              Background: Coronary Artery Disease (CAD), also well-known as ischemic heart disease (IHD) is one of the types of heart disease which is caused by inadequate supply of oxygen and blood toa portion of myocardium. The current World Health Organization (WHO) report, predicted around 7.4 million people to die due to CAD. Obesity (raised BMI- Body Mass Index) is a risk factor for CHD both directly and indirectly. Aim and Objectives: To study correlation of pulmonary function test with BMI in the patients with CAD. Material and Methods: It’s a prospective study conducted in Department of General Medicine after obtaining permission from the Institutional Ethics Committee. The duration of study was 2 years i.e. from January 2015 to December 2016. Inclusion and exclusion criteri as were adequately defined. Pulmonary Function Test was performed in the morning. Daily calibration of the machine using manual calibration syringe as per ATS specification is done. Results: A total of 117 patients were recruited in this study, out of which 64 were males and 53 were females. Females are commonly affected in 40-50 years of age while, for >50 year ages, males are more commonly affected. Out of the total patients evaluated, 54 had abnormal PFT‘s whereas 63 had normal. Average BMI for males was 23.8 whereas average BMI for females was 25.68.Conclusions: It was apparent from the study that pulmonary function is negatively correlated with BMI, as BMI increases pulmonary function decreases. As the mortality of CAD and obstructive/ restrictive disease is rising in India, along with the current practices of prevention and management of CAD patient serial PFT‘s can be a feature to be included in the follow up of these patients.

Key Words: Body mass index, Coronary Artery Disease.

 

INTRODUCTION

Cardiovascular diseases (CVDs) are a group of disorders of the heart and blood vessels and comprise CAD. CVDs are the number one cause of death globally. CAD is a leading cause of death in India and the burden of mortality due to CAD is rising and was projected to have doubled in 2015 compared to 1985.¹The risk of developing CAD has been estimated to be 3 to 4 times higher in south Asians compared tow hite Americans and almost 20 times higher compared to people of Japanese descent.² CAD risk factors fall into modifiable and non-modifiable categories. Non-modifiable risk factors such as age, family history, ethnic origin, gender cannot be altered. Modifiable risk factors can be altered by changing behaviour patterns or lifestyle, and through the administration of prescribed drugs. CAD risk factors include elevated serum total and low density lipoprotein cholesterol (LDL-C), low high-density lipoprotein cholesterol [HDL-C], diabetes mellitus (DM), low level of physical activity, smoking, obesity, sedentary lifestyle, dyslipidaemia and systemic arterial hypertension.³ ‘Obesity’ is defined as BMI≥ 30Kg/m² by National institutes of health; Obesity is arisk factor for CHD both directly and indirectly as obesity itself is a risk factor for type II diabetes mellitus, hypertension, adverse lipid profile, increased pro-inflammatorycytokines especially IL-6 all of which are independent risk factors for CHD.⁴ Adiposity was seen to be strongly and positively associated with CHD and stroke incidence. Underweight men were found to have lower incidence of intracerebral infarction and CHD when compared with normal weight men.⁵ However despite all this over weight and obese CHD patients show lower mortality, this may seem paradoxical; however better cardio respiratory fitness CRF is associated with better prognosis in all patients, therefore improving CRF is more important than improving the BMI of the patients.⁶

 

MATERIAL AND METHODS

It’s a prospective study conducted in Department of General Medicine, D Y Patil University School of Medicine, Nerul, Navi Mumbai, Maharashtra. The study began after obtaining permission from the Institutional Ethics Committee. All patients included in the study with stable CAD i.e. 117, were explained the purpose and rational of the study as well as their role as participants in the study. The duration of study was 2 years i.e. from January 2015 to December 2016. Written informed consent was obtained from all the patients prior to enrolling them in the study.

Inclusion Criteria

Patients with following criteria were selected for this study

1. Established adult CAD cases. (Past or present ECG changes/ stress test proved/2-D Echo/Angiographically proved)
2. Stable CAD for the last 2-6 years.
3. Controlled hypertension

Exclusion Criteria

Patients with following criteria were excluded from study

1. Patients having any attack of angina or MI in the recent past (within 3 months).
2. Patients having any previous history of asthma, COPD, tuberculosis,ILD
3. Patients having any history of smoking.
4. Patients having CCF/LVF.
5. Patients having uncontrolled hypertension.
6. Patients have occupational or environmental lung disease.
7. Patients who had prior lung surgery, bronchiectasis.

A predesigned and pretested proforma was filled from all patients and the information collected from each patient enrolled in the study recorded on a Case Record Form (CRF).Haematological investigations like Complete blood count was done. Also, X-Ray chest, ECG and 2D-echo were performed.Pulmonary Function Test was performed in the morning. Prediction equations for spirometry in adults of Indian origin using the 2005 American Thoracic Society/European Respiratory Society (ATS/ERS) was used. Daily calibration of the machine using manual calibration syringe as per ATS specification is done. FVC, FEV1, FEV1/FVC, FEF25, FEF50, FEF75, FEF25-75 and PEFR were recorded in patients with stable CAD. All data were collected in a Data Collection Form and then transferred to an Excel sheet. The SPSS-version 16 software (SPSS Inc., Chicago, IL, USA) was used for data entry and analysis.

 

RESULTS AND OBSERVATIONS

 

Tables 1: Age wise and gender wise distribution of study participants with CAD

Using Chi Square test, P value- <0.0001

A total of 117 patients were recruited in this study, out of which 64 were males and 53 were females. Since p value is<0.05, there is significant difference between proportion of subjects in different age groups. Females are commonly affected in 40-50 years of age while, for >50 year ages, males are more commonly affected. Overall there is no difference between proportion of total male and female.

 

Table 2: Comparison of demographics among study participants with CAD

Using unpaired t test, for height and BMI, P value is <0.05 i.e. males having significantly more height and lower BMI as compared to females. Average BMI for males was 23.8 whereas average BMI for females was 25.68. It was apparent from the study that pulmonary function is negatively correlated with BMI, as BMI increases pulmonary function decreases.

 

 

 

 

 

Table 3: Correlation of Pulmonary Function Tests with BMI:

Calculated using Pearson‘s correlation coefficient (R). When R is….>0.75: Good correlation; 0.25-0.75: Intermediate correlation; <0.25: Weak correlation Since p value is <0.05, there is significant negative correlation between PFT values and BMI. Overall it is apparent that pulmonary function is negatively correlated with BMI, as BMI increases pulmonary function decreases.

 

Table 4: Pulmonary function test results among study participants with CAD

Out of 117 patients evaluated, 54 had abnormal PFT‘s whereas 63 had normal. These patients had no prior pulmonary risk factors, hence such a high proportion of abnormal PFT in these patients was significant. Using Sign and Binomial Test, out of 117 stable CAD patients with no prior pulmonary risk factor 46.15% patients had abnormal PFT, which is significant.

 

Figure 1: Correlation of PFT with BMI

 

DISCUSSION

Lung function has been correlated with quality of life, with most studies emphasizing its role in patients with chronic obstructive pulmonary disease.⁷Pulmonaryfunction tests measure lung capacity and reveal patterns characteristic of particular diseases. The tests also determine whether the deficit in lung function is mild, moderate or severe. The pulmonary function tests that arecustomarily used for diagnosis include spirometry, lung volume tests and diffusing capacity tests.⁸ In spirometry, a person breathes out into a tube attached to a spirometer, which measures how much air is being exhaled and how quickly. The two most important values are the forced expiratory volume in one second (FEV1) and the forced vital capacity (FVC). FEV1 measures the amount of air expelled from the lungs in the firsts econd of a forced exhalation, while FVC is a measure of the total volume of air exhaled. The spirometer calculates these values automatically, along with the ratio between them, FEV1/FVC.⁹ In the present study, there were a total 117 patients were recruited in this study, out of which 64 were males and 53 females and a significantly more number of patients have restrictive pattern (29.06%) of pulmonary function as compared to obstructive pattern (17.09) of pulmonary function. Males had a lower BMI compared to that of the females. Average BMI for males was 23.8 whereas average BMI for females was 25.68. It was apparent from the study that pulmonary function is negatively correlated with BMI, as BMI increases pulmonary function decreases. Statistically significant reduction in FVC, FEV1, PEFR, and MVV indicate that a combination of restrictive (stiff lungs) and obstructive (cardiac asthma) derangements in lung function occur in CAD patients even after medication and stable for 2-6 years.¹⁰Additional PFT abnormality will enhance the morbidity and mortality in these patients. Hence over attempt was to exclude occupational, post-tuberculous, smoker or any form of pulmonary health hazard and our intention was to see whether deteriorated cardiac function is in some way responsible for PFTabnormalities.¹¹

 

CONCLUSIONS

Study included 117 patients who had no established pulmonary pathology but had established CAD. PFT‘s was performed in each of these patients. Females were commonly affected with IHD in 40-50 years of age; whereas males were more commonly affected when age was >50.Average BMI for males was 23.8 whereas average BMI for females was 25.68. It was apparent from the study that pulmonary function is negatively correlated with BMI, as BMI increases pulmonary function decreases. As the mortality of CAD and obstructive/ restrictive disease is rising in India, along with the current practices of prevention and management of CAD patient serial PFT‘s can be a feature to be included in the follow up of these patients.

 

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