Typically affects only a segment of the hemidiaphragm

Is due to incomplete muscularisation of the diaphragm with a thin membranous sheet replacing the normal diaphragmatic muscle.

Over time this region stretches and on inspiration does not contract normally.

Sudden rupture can occur with increase in intra-abdominal pressure (e.g. coughing, straining during light anesthesia or extubation etc)

True rupture (if it happens) – Effects:

Mass effect of the abdominal viscera–>direct compression of the heart, mediastinal shift

Compression of vena cava and pulmonary veins–> impairs venous return, decreased cardiac output.

So we should maintain adequate depth of anaesthesia

Avoid Nitrous oxide (expansion of intra-abdominal viscera can impair the circulation and respiration)

Reference: Anaesthetic Management of an Adult Patient with Diaphragmatic Eventration
Azhar Rehman*, Zafar Ali Mirza, Saad Yousuf and Asma Abdus Salam