Comparative study on cardiac autonomic modulation during deep breathing test and diaphragmatic breathing in type 2...

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.

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.

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.

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.