Diagnostic sonography SCRS: Diaphragm thickness assessment via ultrasound

Diaphragm Thickness Assessment via Ultrasound

Purpose:

Assess diaphragm function and muscle atrophy.

Monitor changes during mechanical ventilation.

Evaluate neuromuscular diseases affecting the diaphragm.

Measurements:

Diaphragm Thickness (Tdi) at end-expiration and end-inspiration.

Thickening Fraction (TF):

Diaphragm Thickening Fraction (TF) Calculator

Thickness at Expiration (mm): Thickness at Inspiration (mm):

Normal Values:

Thickness at end-expiration: >1.5–2.0 mm.

Thickening fraction: >20–30% suggests good function.

Patient Preparation:

Position: Supine or semi-recumbent (30–45° angle).

Breathing: Normal tidal breathing, ideally at rest.

Cooperation: Ask patient to breathe normally. For intubated patients, coordinate with ventilator settings.

Equipment Setup:

Ultrasound Mode: B-mode (2D imaging) and optionally M-mode.

Probe: High-frequency linear transducer (7–15 MHz) (use curvilinear if depth is an issue in obese patients)

Probe Placement and Imaging:

Preferred Site:

Zone of Apposition: Where the diaphragm lies against the rib cage.

Typically in the 8th to 10th intercostal space, mid-axillary to anterior axillary line (right side often clearer due to liver window).

Steps:
1. Place the probe perpendicular to the chest wall, in a longitudinal orientation between ribs (intercostal)
2. Identify:

Diaphragm as a three-layered structure:

Hypoechoic (muscle) band between two hyperechoic lines (pleura and peritoneum).

3. Use B-mode to measure diaphragm thickness during:

End-expiration (Tdi_exp)

End-inspiration (Tdi_insp)

4. Optional: Switch to M-mode to visualize and measure thickness over time for better temporal accuracy.
Interpretation:

Diaphragm TF Table

Diaphragm Thickness & Thickening Fraction (TF) Table

Clinical Relevance:

Ventilated Patients: Detect diaphragm atrophy over time.

Neuromuscular Disorders: Track progressive dysfunction.

Weaning from Ventilation: TF >30% often predicts success.