Heart–Lung Interaction

Abstract

Mechanical interplay between respiratory and cardiac systems was first recognized about 300 years ago when an English physiologist Stephen Hales observed that the level of the blood column in a glass tube inserted into the carotid artery of a horse varied cyclically with respiration.Heart and lung share the same intrathoracic space, and mechanically this configuration is akin to pump within a pump. As a result, intrathoracic pressure (ITP) and volume changes during respiratory cycle affect the performance of heart. Besides direct mechanical effects, lung and heart interplay also involves certain neurally and humorally mediated phenomena. Taken together, these dynamics constitute heart–lung interaction. Knowledge of heart–lung interaction is especially useful while dealing with critically sick patients on ventilator, because not only are such patients more vulnerable to hemodynamic instability induced by ventilator, but it also forms the basis of functional hemodynamic monitoring.