Carl-Hugo Hamnegård | PubMed Health

PubMed2006

Diaphragmatic function in advanced Duchenne muscular dystrophy.

The aim of this study was to assess diaphragm electrical activation and diaphragm strength in patients with advanced Duchenne muscular dystrophy during resting conditions. Eight patients with advanced Duchenne muscular dystrophy (age of 25 +/- 2 years) were studied during tidal breathing, maximal inspiratory capacity, maximal sniff inhalations, and magnetic stimulation of the phrenic nerves. Six patients were prescribed home mechanical ventilation (five non-invasive and one tracheotomy). Transdiaphragmatic pressure and diaphragm electrical activation were measured using an esophageal catheter. During tidal breathing (tidal volume 198 +/- 83 ml, breathing frequency 25 +/- 7), inspiratory diaphragm electrical activation was clearly detectable in seven out of eight patients and was 12 +/- 7 times above the noise level, and represented 45 +/- 19% of the maximum diaphragm electrical activation. Mean inspiratory transdiaphragmatic pressure during tidal breathing was 1.5 +/- 1.2 cmH2O, and during maximal sniff was 7.6 +/- 3.6 cmH2O. Twitch transdiaphragmatic pressure deflections could not be detected. This study shows that despite near complete loss of diaphragm strength in advanced Duchenne muscular dystrophy, diaphragm electrical activation measured with an esophageal electrode array remains clearly detectable in all but one patient.

Action Potentials↗

PubMed2004

Quadriceps strength assessed by magnetic stimulation of the femoral nerve in normal subjects.

Magnetic stimulation of the femoral nerve is a new technique for assessment of quadriceps strength by measurement of twitch tension (TwQ), a test that is independent of subject motivation. In this study, we sought to establish better define normal values by measurement of TwQ in 45 normal subjects. Supramaximal stimulation, as judged by TwQ, was achieved in 43 of 45 subjects at a mean of 90% of maximum stimulator output. The mean TwQ was 7.3 kilograms force (kgf) (SD 2.3) for women and 9.8 kgf (SD 2.5) for men. The mean maximal voluntary contraction (MVC) force was 48.0 kgf (SD 9.2) for women and 70.1 kgf (15.2) for men. The mean TwQ/MVC ratio was 0.15 for both women and men. Significant correlations were observed between TwQ and weight (r = 0.33, P<0.03) and height (r = 0.32, P<0.03) but these were weak and only partially explained observed variance. Our data confirm that magnetic femoral nerve stimulation is generally acceptable to naive subjects. Values are provided as a function of weight in normal subjects.

Adult↗