Diaphragm
Strength in ALS Assessed by Magnetic Stimulation of the Phrenic Nerve Roots
Gary Mills, Michael I. Polkey,
Catherine Lloyd, Malcolm Green, John Moxham, P.N. Leigh
Tuesday April 15 3:00 pm / Exhibit Hall A
OBJECTIVE:
Assessment of inspiratory muscle strength is of prognostic value in ALS, but traditional
measures (the vital capacity or static inspiratory pressure) are volitional; i.e. they
depend on patient aptitude and motivation. Additionally they are difficult to perform
maximally in the presence of bulbar or facial muscle weakness. Measurement of
transdiaphragmatic pressure during cervical magnetic stimulation of the phrenic nerve
roots (Tw Pdi) is a recently described method of measuring diaphragm strength which is
acceptable to patients. We therefore used this technique to assess the prevalence of
diaphragm weakness in ALS. With this technique the lower limit of normal for Tw Pdi is 19
cm H20 (Hamnegård et al Am J Respir Crit Care Med 1996;153;A785).
DESIGN/METHODS:
The patients were 28 consecutive referrals to a regional ALS centre, who received an El
Escorial diagnosis of definite or probable ALS. They presented between 9 months and 5
years after the onset of symptoms.
RESULTS:
Tw Pdi proved acceptable to the 26 of the 28 patients able to swallow balloon catheters. 5
patients were in ventilatory failure (i.e. PaCO2 > 6kPa). 19 patients had definite
diaphragm weakness
CONCLUSIONS:
Diaphragm weakness is common in ALS even in the initial stages. Measurement of Tw Pdi may
be of potential value both in the clinical management of ALS and in clinical trials of new
treatments Sponsored by: MNDA, Great Britain. |