1. Identity the level of the diaphragm. In the absence of pulmonary disease the diaphragm should be at the ninth thoracic vertebrae during the inspiratory phase of respiration This may be elevated in cases of obstruction with distention or free air in the abdomen. Look at the bony structures, which include the vertebral column, lower ribs, and pelvis. Note any asymmetry. The placement of catheters, if any, in abdominal vessels should be noted.