Inspiratory muscle training improves respiratory muscle function and may improve weaning
outcomes in patients with weaning difficulties. Compared to the commonly used pressure
threshold loading, tapered flow resistive loading better accommodates pressure–volume
relationships of the respiratory muscles, which might help to facilitate application
of external loads and optimise training responses.
The objective of this study was to compare acute breathing pattern responses and perceived
symptoms during an inspiratory muscle training session performed against identical
external loading provided as pressure threshold loading or as tapered flow resistive
loading. We hypothesised that for a given loading, tapered flow resistive loading
would allow larger volume expansion and higher inspiratory flow responses and consequently
higher external work of breathing and power than pressure threshold loading and that
subsequently patients perceived fewer symptoms during tapered flow resistive loading
than during pressure threshold loading.
In this exploratory study, 21 patients (maximal inspiratory pressure: 35 ± 14 cmH2O and vital capacity:0.85 L±0.37 L) performed two training sessions against external
loads equalling 42 ± 15% of maximal inspiratory pressure provided either as pressure
threshold loading or as tapered flow resistive loading. During these training sessions,
breath-by-breath data of breathing parameters were collected, and patients rated their
perceived breathing effort, dyspnoea, and unpleasantness.
Compared to pressure threshold loading, tapered flow resistive loading allowed significantly
larger volume expansion (0.53 ± 0.28 L versus 0.41 ± 0.20 L, p < 0.01) and inspiratory
flow responses (0.43 ± 0.20 L/s versus 0.33 ± 0.16 L/s, p = 0.01). Tapered flow resistive
loading was perceived as less unpleasant (3.1 ± 1.9 versus 3.8 ± 2.4, p = 0.048).
No significant differences in breathing effort, dyspnoea, work of breathing, and power
For a given loading, inspiratory muscle training with tapered flow resistive loading
allowed larger volume expansion and higher inspiratory flow responses than pressure
threshold loading, which led patients to perceive tapered flow resistive loading as
less unpleasant. This might help us to facilitate early implementation of inspiratory
muscle training in patients with weaning difficulties.
Clinical trial registration number
Clinicaltrials.gov identifier: NCT03240263