PURPOSE: Myotonic Dystrophy (MD) is a multisystem neuromuscular disease that affects the respiratory muscles and cardiac function. Progressive respiratory muscle weakness has been detected in this group of patients. The effects of partial home respiratory muscle training program on respiratory muscle strength and heart rate variability in MD have not been studied yet.
METHODS: Six patients(3m) (age 37.3 13 years;BMI 25.5 6.7 kg/m2 ) were studied in an crossover study following an A-B-A design (phase A control time,phase B training time and phase A control time). Spirometry and respiratory pressures were assessed beforeand after three study phases. HRV was evaluated before and after phase B.Patients performed the trainingthree times/week, once at the outpatient clinic and twice at home.The pressure load progressed from 20%-70% of PImax and PEmax.The training was performed during 8 weeks and consisted of 2 sets of 15 breathing(first week), 2 sets of 20 breathing(second week), 3 sets of 20 breathing (third week), 4 sets 20 breathing on the remaining weeks.
RESULTS: There was significant improvement in PImax and PEmax afterphase B(TMR) that was maintained after the end of phase A. PImax values in cmH2O were: 53.3±13.2, 54.6±12.7, 65.1±11.5 and 67±10.1. PEmax values in cmH2O were:60.5±10.5, 63±9.5, 81.8±20.2 and 76.8± 20.HRV analysis of frequency-domain parameters demonstrated no statistical difference in High frequency(163± 70,5 ms vs 480,4#177; 266 ms), Low frequency(264,5± 51 ms vs 535± 152,5 ms) and LF/HF ratio(2,8± 0,84 vs 2,2± 0,68) after 8 week of training; however, we found a trend to increased sympathetic drive after training.
CONCLUSION: Our preliminary results demonstrate that a partial home program of RMT is feasible and improves respiratory strength in MD patients.Further studies must be done to evaluate the effects of respiratory muscle training on autonomic heart modulation.
CLINICAL IMPLICATIONS: Fifteen per cent of the MD patients die due respiratory complications. The most frequent cause is the pneumonias and respiratory insufficiency that are related to respiratory muscle weakness. The respiratory muscle training would help to prevent respiratory complications.
DISCLOSURE: Guilherme de Freitas Fregonezi, No Financial Disclosure Information; No Product/Research Disclosure Information