[Recommendations for respiratory muscle testing]

Based on the tremendous impact of impaired respiratory muscle function, tests on their function play a significant role in respiratory and intensive care medicine. Besides differential diagnosing e.g. during prolonged weaning and quantification of impaired respiratory muscle function, e.g. in COPD, neuro-muscular diseases or ventilator-induced diaphragmatic dysfunction, those tests qualify for follow-up assessment, e.g. phrenic nerve lesions or specific respiratory muscle training. In general, (simple) volitional and (complex) non-volitional tests are available. Volitional tests aim at screening for potential respiratory muscle impairment, while non-volitional tests - including ultrasound application - are used to further specify low values assessed by volitional tests and to assess complex clinical conditions (e.g. intubated, sedated patients). Several tests are complementary or additive to each other. Complete assessment for respiratory muscle function, therefore, frequently requires the combination of different test regimes. The current recommendations include in-depth description and practical guidelines for the different tests and approaches to assess respiratory muscle function.