Comparative study on cardiac autonomic modulation during deep breathing test and diaphragmatic breathing in type 2 diabetes and healthy subjects

AIMS/INTRODUCTION Diaphragmatic breathing is known to have a beneficial effect on the cardiopulmonary system, and enhances parasympathetic activation. We evaluated the influence of diaphragmatic breathing on time domain measures of heart rate variability in diabetics and healthy subjects. MATERIALS AND METHODS A total of 122 type 2 diabetics and 94 healthy subjects (controls) were randomly allocated to a deep breathing test and diaphragmatic breathing (61 diabetics and 47 controls in each group). Heart rate variability parameters; namely, expiratory:inspiratory ratio (E:I ratio), root mean square of successive N-N interval difference (r-MSSD) and standard deviation of all the N-N intervals (SDNN), were quantified from 1-min supine electrocardiogram obtained while subjects carried out the deep breathing test/diaphragmatic breathing at six respiratory cycles per min. Data analysis was carried out by Student's unpaired t-test. A P-value <0.05 was taken as significant. RESULTS E:I ratio, SDNN and r-MSSD of type 2 diabetics was significantly lower compared with controls in the diaphragmatic group (P < 0.001). E:I ratio and SDNN were significantly lower in type 2 diabetics compared with controls in the deep breathing group (P < 0.0001, P < 0.019, respectively). In controls, E:I ratio, r-MSSD and SDNN of the diaphragmatic breathing group were significantly higher compared with the deep breathing group (P < 0.01). In diabetics, none of the measured heart rate variability parameters varied between diaphragmatic breathing and deep breathing. CONCLUSIONS Subclinical cardiac autonomic neuropathy persists in type 2 diabetics. In type 2 diabetics, diaphragmatic breathing quantifies certain aspects of parasympathetic dysfunction, which is not shown by the deep breathing test. Diaphragmatic breathing induces greater cardiac autonomic modulation in healthy subjects.