In situ isolated perfused and innervated left hemidiaphragm preparation

Abstract

We developed a vascularly isolated in situ preparation of the left hemidiaphragm in which arterial blood was only provided through the left phrenic artery and the venous blood only drained through the phrenic vein. The costal margins were secured and connected to three force transducers. Muscle shortening was measured by sonomicrometry. The presence of aterial collaterals between the left hemidiaphragm and the systemic circulation was excluded by the systemic injection of a vital dye (Lissamine Green), a neuromuscular blocking agent (succinylcholine), and by the injection of epinephrine. Left phrenic nerve stimulation produced homogeneous shortening and tension. The degree of shortening in the isolated and intact left diaphragm at the same resting length was similar. The preparation was stable for 2 h with < 10% decline in maximum tension. Two advantages of this preparation are particularly important. 1) Diaphragmatic energetics can be studied independently of systemic factors, and 2) the role of phrenic nerve afferents in the control of breathing and systemic circulation can easily be assessed without activating nonphrenic nerve afferents.