Intrathoracic pressure measurement in cattle: standardized procedure.

A procedure to standardize the position of an esophageal catheter (eso-cat) tip, used to measure intrathoracic pressure, was tested in ten healthy Dutch Friesians. The cattle were in normal condition with body weights (BW) between 52 and 670 kg and thoracic perimeters (TP) between 80 and 210 cm. The position of the neck and head was standardized. The eso-cat was introduced via the nose into the thoracic portion of the esophagus. The distance between the nares and the eso-cat tip (Lcat), which was positioned between the crossing point with the aorta and the caudal mediastinal lymph nodes, was measured for each animal. The regression equation, calculated between the Lcat and the BW and TP was, respectively: Lcat (cm) = 65 + 0.115 x BW (kg) (r2 = 0.99) and Lcat (cm) = 22 + 0.535 x TP (cm) (r2 = 0.97). The corresponding residual standard deviations were respectively 2.52 and 4.37 cm. The multiple and curvi-linear regression equation did not give a significantly better fit of the data.