Thread by @Ben_Kelemen

Cardiac effects of positive pressure ventilation: LV effects. PPV increases intrathoracic pressure and decreases venous return. This will decrease LV filling pressures (preload). Increased intrathoracic pressure decreases the "transmural gradient" for the LV #distancemeded 1

By the law of Laplace a decreased gradient will decrease LV afterload. I think it is easier to imagine PPV squeezing the heart and making it easier to pump. In summary PPV decrease LV preload and LV afterload. #distancemeded 2

Positive pressure ventilation increases intrathoracic pressure and decreases venous return to the RA. So PPV decreases RV preload.

PPV has variable effects on RV afterload. Usually PPV increases PVR and thus and increases RV afterload. The exception is patients breathing at very low lung volumes with atelectasis or hypoxia. To the extent PPV corrects atelectasis or hypoxia it decreases RV afterload.

In summary for the LV positive pressure ventilation decreases preload and afterload. For the RV PPV decreases preload and usually (but not always) increases afterload. #distancemeded

@TedWJamesMD @ElliottMillerMD @Sam_Brusca @david_furfaro @cardionerds
Credit to @ElliottMillerMD, onlinejacc.org/content/72/13/…, Gomez, H., & Pinsky, M. R. (2012). Effects of mechanical ventilation on heart-lung interactions. Principles and Practice of Mechanical Ventilation, 1–31.

^Corrected link to JACC paper:
onlinejacc.org/content/72/13/…