Ph. Johnson et al., EVALUATION OF THE THRESHOLD(R) TRAINER FOR INSPIRATORY MUSCLE ENDURANCE TRAINING - COMPARISON WITH THE WEIGHTED PLUNGER METHOD, The European respiratory journal, 9(12), 1996, pp. 2681-2684
Inspiratory muscle training (IMT) has been shown to enhance exercise p
erformance. The weighted plunger (WP) system of inspiratory threshold
loading is the most commonly used method of IMT, but is expensive and
cumbersome. We have evaluated a commercially available portable spring
-loaded IMT device, the THRESHOLD(R) trainer. The WP and THRESHOLD(R)
trainer devices were evaluated with their opening pressures set, in ra
ndom order, at 10, 20, 30 and 40 cmH(2)O. Using an air-pump, pressure
at the valve inlet was recorded at the point at which the valve opened
, and at airflow rates of 20, 40, 60, 80 and 100 L . min(-1). Ten THRE
SHOLD(R) trainers were then compared using the same opening pressures
and airflow rates, Finally, 10 patients with stable chronic heart fail
ure (CHF) inspired, in random order, through the WP and THRESHOLD(R) t
rainer for 4 min each. The pressure-time product (PTP) was calculated
for each 4 min period, to compare the work performed on inspiring thro
ugh each device. The mean measured opening pressures for the WP set at
10, 20, 30 and 40 cmH(2)O, were 9.0, 19.3, 27.9 and 39.2 cmH(2)O, res
pectively, and there was little change over the range of flow tested.
Corresponding values for the THRESHOLD(R) trainer were 7.5, 16.9, 26.2
and 39.1 cmH(2)O, with the pressure being closer to the set pressure
as now increased to that seen in clinical practice. The 10 different t
rainers tested performed very similarly to one another. Work performed
(as measured by PTP) on inspiring through the WP and THRESHOLD(R) tra
iner was not significantly different. Although less accurate than the
weighted plunger, the THRESHOLD(R) trainer is an inexpensive device of
consistent quality. In a clinical setting it would be a satisfactory
option for inspiratory muscle training in most patients, but less so i
n patients with very low inspiratory flow rates.