Does it make difference to measure diaphragm function with M mode (MM) or B mode (BM)?

Area of Science:

• Critical Care Medicine
• Pulmonology
• Medical Imaging

Background:

• Diaphragm dysfunction is common in mechanically ventilated patients.
• Diaphragm thickening fraction (DTF) via ultrasound shows promise for predicting ventilator weaning success.
• Standardized ultrasound measurement techniques for diaphragm thickness (DT) are lacking, with limited comparison between M-mode (MM) and B-mode (BM).

Purpose of the Study:

• To compare M-mode (MM) and B-mode (BM) ultrasound measurements of diaphragm thickness (DT) and excursion in intensive care unit (ICU) subjects.
• To evaluate the agreement and bias between MM and BM for diaphragm measurements.

Main Methods:

• Sixty-two ICU subjects were enrolled, including invasively and non-invasively ventilated patients.
• Diaphragm thickness (DT) and excursion were measured using both MM and BM during tidal and maximal inspiratory breathing.
• Measurements were repeated three times for each mode, and mean values were calculated. Bland-Altman analysis assessed agreement between MM and BM.

Main Results:

• No significant differences were found between MM and BM measurements for expiratory DT, tidal DTF, and diaphragm excursion.
• Tidal inspiratory DT measurements showed a statistically significant difference between MM and BM (P=0.022).
• Overall, MM and BM demonstrated high compatibility for most diaphragm thickness and excursion measurements.

Conclusions:

• Ultrasound M-mode and B-mode measurements are largely compatible for assessing diaphragm thickness and excursion in ICU patients.
• Except for tidal inspiratory thickness, both methods provide similar results, supporting their use in clinical practice.
• Further research is needed to standardize diaphragm ultrasound measurements and confirm these findings.