Evaluation of Respiratory Muscle Strength and Diaphragm Ultrasound: Normative Values, Theoretical Considerations, and Practical Recommendations.

Background: Reference values derived from existing diaphragm ultrasound protocols are inconsistent, and the association between sonographic measures of diaphragm function and volitional tests of respiratory muscle strength is still ambiguous.

Objective: To propose a standardized and comprehensive protocol for diaphragm ultrasound in order to determine lower limits of normal (LLN) for both diaphragm excursion and thickness in healthy subjects and to explore the association between volitional tests of respiratory muscle strength and diaphragm ultrasound parameters.

Methods: Seventy healthy adult subjects (25 men, 45 women; age 34 ± 13 years) underwent spirometric lung function testing, determination of maximal inspiratory and expiratory pressure along with ultrasound evaluation of diaphragm excursion and thickness during tidal breathing, deep breathing, and maximum voluntary sniff.

Electrophysiological Properties of the Human Diaphragm Assessed by Magnetic Phrenic Nerve Stimulation: Normal Values and Theoretical Considerations in Healthy Adults.

Purpose: This study determined normal values for motor evoked potentials (MEPs) and compound muscle action potentials (CMAPs) of the diaphragm following cortical and cervical magnetic stimulation (COMS and CEMS) of the phrenic nerves in healthy adults.

Methods: Using surface electrodes, diaphragmatic MEP and CMAP were recorded in 70 subjects (34 ± 13 years, 25 men) following supramaximal cortical magnetic stimulation and CEMS at functional residual capacity and using a standardized inspiratory pressure trigger (-0.5 kPa).