Measuring Inspiratory Muscle Strength in Neuromuscular Disease: One Test or Two?

¹ Services de Réanimation Médicale, Physiologie - Explorations Fonctionnelles, and Centre d'Innovations Technologiques, Hôpital Raymond Poincaré, AP-HP, 92380 Garches, France
² Service de Pédiatrie Pneumologique et INSERM UMR-S 719, Université Pierre et Marie Curie Paris 6, Hôpital Armand Trousseau, 75000 Paris, France
³ Services de Réanimation Médicale, Physiologie - Explorations Fonctionnelles, and Centre d'Innovations Technologiques, Hôpital Raymond Poincaré, AP-HP, 92380 Garches, France; and Inserm U 651, 94000 Créteil, France

^* To whom correspondence should be addressed. E-mail: f.lofaso{at}rpc.ap-hop-paris.fr.

	Abstract

Inspiratory muscle strength monitoring is crucial in patients with neuromuscular disorders. The sniff nasal inspiratory pressure (SNIP) and maximal inspiratory pressure (MIP) are usually measured. We investigated whether the test yielding the best value at baseline continued to yield the best value during follow-up.

We studied 25 patients with Duchenne muscular dystrophy (DMD) and 61 with myotonic muscular dystrophy (MMD). SNIP and MIP were measured at baseline then annually.

At baseline, SNIP was less than MIP in 20 DMD patients (80%) and 32 MMD patients (52%). During follow-up in DMD patients, changes in the best method always occurred from SNIP to MIP. In MMD patients, when SNIP was better than MIP at baseline, SNIP was usually better during follow-up (88%), whereas better MIP than SNIP at baseline was frequently followed by shift to SNIP (50%).

MIP may be sufficient for monitoring inspiratory muscle function in DMD adults. In MMD, the marked variability in the test yielding the best value at baseline indicates a need for performing both tests at baseline; however, when SNIP yields the best value at baseline, using SNIP alone during follow-up may be appropriate.