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Incremental threshold loading: a standard protocol and establishment of a reference range in naive normal subjects
P H Johnson1, A J Cowley, W J Kinnear
1University Hospital, Queens Medical Centre, Nottingham, UK.
The European Respiratory Journal
|March 11, 1998
Summary
This study standardized Incremental Threshold Loading (ITL) for assessing inspiratory muscle strength. A new protocol and reference range were established, showing ITL is reproducible and reliable for measuring lung function.
Area of Science:
- Respiratory Physiology
- Pulmonary Function Testing
Background:
- Incremental Threshold Loading (ITL) is a proposed measure of inspiratory muscle strength and endurance.
- Existing ITL protocols lack standardization and reference ranges, hindering consistent application.
Purpose of the Study:
- To develop a standardized Incremental Threshold Loading (ITL) test protocol.
- To establish reference ranges for ITL based on a large cohort of healthy volunteers.
- To assess the reproducibility and repeatability of the standardized ITL test.
Main Methods:
- Developed an ITL test protocol using a weighted plunger (WP) with standard pressure increments.
- Subjects inspired through the WP, starting at 10 cmH2O, increasing by 5 cmH2O every 2 minutes until failure.
- Tested 60 healthy volunteers (aged 20-80) and reassessed 12 for reproducibility.
Main Results:
- Established regression equations for maximum threshold pressure (Pmax) based on age: Males: Pmax = 103.8 - (1.0 x age); Females: Pmax = 93.7 - (1.0 x age).
- Pmax significantly correlated with age but not height or weight.
- Within-subject standard deviation for reproducibility was 5.4 cmH2O.
Conclusions:
- Incremental Threshold Loading (ITL) is a simple, reproducible technique for assessing inspiratory muscle function.
- The developed standardized protocol and reference range provide a reliable tool for clinical and research applications.
- ITL is easily performed by naive subjects, making it widely applicable.