Pulmonary function tests in type 2 diabetes mellitus and their association with glycemic control and duration of the disease

Background: Pulmonary complications of diabetes mellitus (DM) have been poorly characterized. Some authors have reported normal pulmonary functions and even concluded that spirometry is not at all necessary in diabetic patients. Some studies have shown abnormal respiratory parameters in patients of DM. Moreover, the duration of DM and glycemic control have varied impact on the pulmonary functions.

Aims and objectives: The study was undertaken to analyze the pulmonary function parameters in diabetic patients and compare them with age and gender matched healthy subjects. We correlated forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) in diabetic patients with duration of the disease and glycosylated hemoglobin (HbA1c).

Materials and methods: Pulmonary function tests (PFTs) were recorded in 60 type 2 diabetic male patients and 60 normal healthy male controls aged 40-60 years by using Helios 702 spirometer. The PFTs recorded were - FVC, FEV1, FEV1/FVC, FEF25, FEF50, FEF75, FEF25-75, FEF0.2-1.2, and peak expiratory flow rate (PEFR). HbA1c of all the patients was estimated by ion exchange resin method, which is a very standard method of estimation. PFTs of diabetic patients and controls were compared by applying Student's unpaired t test. Associations between FVC and FEV1 and HbA1c and duration of illness in diabetic patients were analyzed by applying Pearson's coefficient.

Results: The PFTs were significantly decreased in diabetic patients compared with the healthy controls except FEV1/FVC. There was no correlation found between FVC and FEV1 and duration of illness as well as HbA1c.

Conclusion: DM being a systemic disease, which also affects lungs causing restrictive type of ventilatory changes probably because of glycosylation of connective tissues, reduced pulmonary elastic recoil and inflammatory changes in lungs. We found glycemic levels and duration of disease are probably not the major determinants of lung pathology, which requires further research.