Muscle Ultrasound Study in Shock Patients

DUS assessments of diaphragmatic thickness (TDI), thickness fraction (TFDI) and shear modulus (SMDI), this last measured by shear-wave elastography (SWE), will be performed for both right and left hemi-diaphragms.

A landmark between the 8th and 10th intercostal space in the mid-axillary or antero-axillary line, 0.5-2 cm below the costophrenic sinus, will be used. Here, the diaphragm can be seen as the less echogenic structure between two echogenic lines; TDI (cm) will be the calculated as the distance between the two lines at the end of expiration and TFDI as the rate of change between end-expiration and end-inspiration thicknesses (TFDI = "thickness at end inspiration" - "thickness at end-expiration" / "thickness at end-expiration", %).

SMDI will assess muscle's stiffness. For each image, a region of interest covering the widest possible surface of diaphragm and allowing an acquisition frequency of 2Hz will be set; results will be retrieved in kilopascals (kPa).

PMUS assessments of quadriceps rectus femoris (RF) muscle cross-sectional area (CSARF), echogenicity (ECHORF) and shear modulus (SMRF), this last measured by shear-wave elastography (SWE), will be performed.

Probe will be placed perpendicularly to the anterior plane of the thigh, in 2 anatomical points, as follows:

(i) in the midpoint between the anterior superior iliac spine and the upper pole of the patella and (ii) the border of the lower 1/3 and upper 2/3 between the anterior superior iliac spine and the upper pole of the patella.

CSARF (cm2) will be calculated by outlining the area under the muscle hyperechoic line (aponeurosis). For ECHORF (differences in grey-scale images), the analysis of a region of interest (ROI) of 2cm x 2cm will be performed.

For SMRF (kPa), a ROI covering the widest possible area of the RF and allowing an acquisition frequency of 2Hz will be set for analysis.

All assessments will be performed with minimal compression and a copious amount of water-gel.

P0.1 is "the pressure developed in the occluded airway 100 milliseconds after the onset of inspiration". Its use doesn't require any additional equipment since it can be easy measured by using patient's ventilator.

For the measurement itself, patients will be in semi-recumbent position (head elevation between 30° and 45°) with knee extended in neutral position and will be asked to stay as relaxed as possible. After 5 minutes breathing without any interruption or disturbance, 4 measurements will be observed and recorded as displayed on the ventilator screen.

This is a manual muscle strength testing tool, used very often in the ICU setting. It's based on the assessment of the following muscle groups: shoulder abduction, elbow flexion, wrist extension, hip flexion, knee extension, and dorsiflexion of the ankle, all scored bilaterally. Muscle strength is graded as follows: 0, "no visible/palpable contraction"; 1, "visible/palpable contraction without movement of the limb"; 2, "movement of the limb, but not against gravity"; 3, "movement against gravity"; 4, "movement against gravity and some resistance"; 5, "normal".

The sum score ranges between 0 and 60 (between 0 and 5, in 12 muscle groups), with a score <48 indicating the presence of weakness.