Lung function quality in patients with myotonic dystrophia type 1

Introduction All patients (pts) with myotonic dystrophia type 1 (DM1) are at risk for respiratory failure (RF), which has been found responsible for 40% mortality in this population. Results from respiratory screening in other neuromuscular diseases have lead in the DM1 population to expert opinion based advice to evaluate lung function (LF) to identify patients at risk of RF. Objective To assess lung function (LF) quality in DM1 pts referred for respiratory evaluation. Methods Retrospectively data analysis from June 2008 until January 2014. LF was performed according to ERS/ATS guidelines, by experienced analysts, with emphasis on the difference of sitting and supine testing (ΔFVCin). Results 114 pts were eligible for evaluation. 37 (32.5%) two were unable to perform the LF, in 35 the LF was of poor quality. Several causes were reported: insufficient reproducibility of LF (19), inability to hold mouthpiece (8), insufficient hand function (8), fatigue during function testing (3), fear of orthopnea in supine position (2). In several pts we found combined problems and 5 pts could not be instructed on how to perform the LF test. 77 pts were evaluated: age 45.3 (+ 12.2)years), 31 pts (40.3%) were male, BMI 26 kg/m 2 (15.3-45.4). Pimax 44.7 (3.3-124) % pred. FVCin (sit) 72.3 (+ 19.9)%pred, was significantly higher than FVCin (sup) 66.6% (+18.8) pred (p Conclusion In nearly one third of this population LF could not be performed adequately. In the remaining pts there was a significant difference between sitting and supping LF. Though sequential LF testing is advised to identify patients with NMD at risk for RF, this test is not usable as a standard screening tool in the entire DM1 population.