Technique

 

Before fluoroscopy, we have the patient practice deep breathing (with the mouth open) and sniffing. For sniffing, we tell the patient to first take in a deep breath, then breathe all the way out, and finally (with the mouth closed) to breathe in as hard, fast, and deeply as possible. 

 

With the fluoroscopy table vertical, we have the patient stand on the platform with his or her back against the table. We center the x-ray beam at the level of the diaphragm and collimate from the sides. However, we include the upper chest so that we can observe the motion of the anterior chest wall.

 

We observe and record two or three quiet (spontaneous and uninstructed) breaths and then two or three deep breaths and finally two or three sniffs. Then we have the patient rotate into the lateral position with arms raised or folded on top of the head and repeat the sequence of quiet breaths, deep breaths, and sniffs. Imaging in the lateral position shows the motion of the posterior hemidiaphragms, which may move differently from the anterior hemidiaphragms. It also shows the motion of the sternum and anterior chest wall.

 

With each breath and sniff, we observe the direction of motion and the extent of excursion of each hemidiaphragm relative to the contralateral hemidiaphragm and rib cage. 

 

Normal Findings

 

On quiet and deep inspiration, both hemidiaphragms move downward as the anterior chest wall moves upward. On deep inspiration, normal excursion is at least one rib interspace in adults. The excursion may be somewhat asymmetric and there may be a slight delay or lag on one side, typically the right. In the lateral projection, the excursion of the posterior part of the hemidiaphragm may be greater than that of the anterior part, especially on the right.

 

Abnormal Findings

 

In paralysis of one hemidiaphragm, orthograde excursion is absent and there may be paradoxical motion even on quiet and deep inspiration. On sniffing, there is usually paradoxical motion.

In paralysis of both hemidiaphragms, the two may move paradoxically together if anterior chest wall motion is vigorous enough. This symmetric motion of the two hemidiaphragms may at first appear to be normal until the radiologist recognizes that the hemidiaphragms are passively following the anterior ribs upward on inspiration, rather than moving in the opposite direction, as is normal.

 

In weakness of one or both hemidiaphragms, excursion is reduced or delayed on quiet and deep inspiration. If weakness is more severe, motion may be paradoxical on deep breathing and even on quiet breathing, especially anteriorly. On sniffing, motion is usually paradoxical. However, if there is any orthograde motion on quiet or deep inspiration, then the hemidiaphragm is merely weak, but not paralyzed.

 

Eventration of the hemidiaphragm is a special case of weakness in which only a segment of the hemidiaphragm (typically the anterior aspect on the right) moves abnormally. 

 

 

Reference

Imaging of the Diaphragm: Anatomy and Function

Laura K. Nason, Christopher M. Walker, Michael F. McNeeley, Wanaporn Burivong, Corinne L. Fligner, and J. David Godwin

RadioGraphics 2012 32:2, E51-E70