Heart-lung interactions during positive pressure ventilation:: left ventricular pressure-volume momentary response to airway pressure elevation

Left ventricular (LV) pressure and volume changes are known to occur in response to positive airway pressure (PAP). We aimed to further describe the immediate LV response to increased PAP as demonstrated in successive heart cycles with LV pressure and volume alterations. We postulated that these acute systematic LV events during institution of PAP can follow a distinct pattern that would allow calculation of parameters of systolic function, including end-systolic elastance (E-es) and preload recruitable stroke work (PRSW). We also aimed to examine the relationship of PAP-derived E-es and PRSW to the same parameters derived from vascular occlusion. Methods: Eight anesthetized adult pigs were studied with invasive circulatory measurements including LV pressure and volume (conductance). The PAP intervention was an airway pressure plateau of 15 cm H2O for 6 s (APP). Venous occlusion was performed by transient balloon inflation in the inferior vena cava (IVCO). E-es and PRSW were derived for each APT and NCO intervention. Results: Central circulatory variables during APP and IVCO are reported. LV systolic function parameters could be derived from each of the heart-lung interactions during APP sequences. E-es and PRSW derived from APP showed a significant positive bias in relation to those derived from the IVCO sequence. Conclusions: We conclude that the heart-lung interactions during APP of the magnitude and duration shown hero can allow derivation of E-es and PRSW. These parameters are not interchangeable with E-es and PRSW derived from IVCO.