Table 1 Summary of the clinical tests used in the assessment of respiratory muscle strength [63]
Test | Threshold values | Advantages | Disadvantages | |
|---|---|---|---|---|
Volitional Tests | Maximum static inspiratory pressure (PImax) | Male < − 45 cm H2O Female < − 30 cm H2O | Easy to perform. Normal values are available | Difficult interpretation. Lack of specificity |
Maximum static transdiaphragmatic pressure (PI,di,max) | Male < 40 cm H2O (2) Female < 30 cm H2O | Easy to perform. Well tolerated by patients. | Wide normal range. Limited usefulness in clinical practice. Limited normal data | |
Sniff transdiaphragmatic pressure (Sniff Pdi) | Male < 100 cm H2O (2) Female < 70 cm H2O | Requires little practice. It is relatively reproducible. Range of normal values | Technical limitations Variability. | |
Maximum sniff pressures (nasal) | Male < 50 cm H2O Female < 45 cm H2O | |||
Maximum cough pressure | Male < 130 cm H2O Female < 95 cm H2O | Normal ranges available | Limited validation in critically ill patient. | |
Nonvolitional tests | Twitch transdiaphragmatic pressure (PdiTw) | Male and female < 18 cm H2O | Measurement specific for the diaphragm and is not influenced by the central nervous system | Requires considerable skill. Uncomfortable for patients |
Diaphragm excursion (DE) | < 10 cm | Provides both morphological and functional information in real time. Allows repeated measurements over time and monitoring recovery | Learning curve. Inter-observer variations. Availability. Reproducibility | |
Inspiratory diaphragm thickening fraction (TFdi) | < 20% |