Key Points
- To assess the independent effects of phase-specific negative intrathoracic pressure on left ventricular filling during diastole and emptying during systole.
- Evaluated six anesthetized closed-chest dogs (N=6) using electrocardiogram-triggered phrenic nerve stimulation to isolate negative intrathoracic pressure to either diastole or systole.
- Tested hemodynamic responses under conditions where lung volume was maintained through complete airway obstruction or allowed to expand during nerve stimulation.
- Diastolic negative intrathoracic pressure during airway obstruction decreased left ventricular filling volume by -37 ± 6.1% and subsequent stroke volume by -30.8 ± 5.9%, with right atrial pressure increasing significantly more than left atrial pressure.
- Systolic negative intrathoracic pressure at constant preload decreased left ventricular stroke volume by -12.9 ± 2.5%, driven by elevated left ventricular systolic pressure relative to esophageal pressure.
Structured PICO
PPopulationSix anesthetized closed-chest dogs
IInterventionNegative intrathoracic pressure (NITP) confined to either diastole or systole using electrocardiogram (ECG)-triggered phrenic nerve stimulation
OOutcomeLeft ventricular filling volume (integrated mitral flow) and LV stroke volume (integrated ascending aortic flow)surrogate
Negative intrathoracic pressure independently decreases left ventricular filling during diastole (likely via ventricular interdependence) and stroke volume during systole (by increasing afterload).