Inspiratory muscle weakness is associated with autonomic cardiovascular dysfunction in patients with type 2 diabetes mellitus.

INTRODUCTION: Diabetic autonomic neuropathy is a complication of diabetes mellitus (DM) that can cause cardiovascular and respiratory abnormalities. The association between respiratory muscle weakness and autonomic cardiovascular neuropathy has not yet been studied. The aims of the present study were to assess respiratory muscle strength, pulmonary function, and heart rate (HR) variability in diabetic patients with and without diabetic autonomic neuropathy.
MATERIALS AND METHODS: Twenty-four patients with type 2 DM were divided into two groups: those without diabetic autonomic neuropathy (C group, n = 12); and those with diabetic autonomic neuropathy (DAN group, n = 12). We evaluated pulmonary function, maximum static inspiratory pressure (PImax), maximum static expiratory pressure (PEmax), and HR variability.
RESULTS: The results of the pulmonary function tests were similar in both the groups. PImax was lower in the DAN group (80 ± 24 vs. 102 ± 24 cmH(2)O, p = 0.03), but PEmax was similar in both the groups. RR intervals (878 ± 122 vs. 743 ± 88 ms; p < 0.01), standard deviation of RR intervals (28 ± 11 vs. 14 ± 4 ms; p < 0.01) and squared root of the sum of successive differences of squared RR intervals (15 ± 6 vs. 8 ± 5 ms; p < 0.01) were higher in the C group. In the DAN group, resting HR was higher (82 ± 10 vs. 69 ± 9 bpm; p = 0.01) than in the C group. There was a positive correlation between PImax and RR intervals (r = 0.452, p = 0.02) and a negative correlation between PImax and resting HR (r = -0.482, p = 0.01), and PImax and DM duration (r = -0.463, p = 0.02).
CONCLUSION: Patients with type 2 DM and autonomic neuropathy showed reduced respiratory muscle strength and less HR variability. Respiratory muscle weakness may be associated with autonomic dysfunction in these patients.