To begin, position the patient in a semi recumbent position on their back. Cover the tip of the linear array transducer with ultrasound gel. After ensuring the ultrasound is in B mode for positioning, hold the probe by enclosing the tip of the probe with the thumb and index finger.
Palpate the chest wall surface to locate the right eighth, ninth, or 10th intercostal spaces between mid and anterior axillary lines. Then place the probe within the zone of apposition, making sure it's entirely situated between the ribs. If a rib appears in the image, adjust the angle of the probe by tilting it up and down until only the diaphragm is visible.
On the ultrasound monitor, identify two bright white parallel lines above the liver indicating the pleural and peritoneal membranes. Adjust the depth of the image by clicking on the increase or decrease depth button to maximize the size of the diaphragm. Ensure the diaphragm is visualized in the middle of the monitor.
This ensures maximum resolution of the pleural and peritoneal lines from surrounding structures. Next, to optimize image quality, open the ultrasound unit software. Then click the gain button to adjust the image brightness.
Increase the gain by clicking the increase button to brighten the image. Conversely, click the decrease button to darken the image. Upon optimizing image quality, click the M mode button to place the ultrasound in the M mode.
Position the single vertical scan line between the sections where the pleural and peritoneal lines are the clearest. Run M mode over a full cycle of inspiration and expiration during tidal breathing. Then click on the freeze to capture the actual state and save to save the image.
Next, with a skin safe marker, mark the probe's location on the patient's body. Once the examination is complete, click the End Exam button. Next, for image analysis, start the DICOM viewer software and open the necessary DICOM files.
Then click on the distance tool and draw a straight line from the inner edge of the pleural membrane to the inner edge of the peritoneal membrane at end expiration. Record this value as diaphragm thickness. Repeat similar measurements at peak inspiration of the same breath to obtain the diaphragm thickness at peak inspiration.
Analyze diaphragm thickness at end expiration and peak inspiration from the same breath to assess the diaphragm thickening fraction. Then using the given equation, calculate the diaphragm thickening fraction for each breath. In healthy adults, resting end expiratory diaphragm thickness ranges from 1.5 to 5.0 millimeters, while tidal diaphragm thickening fraction falls between 15 to 30%
