Cardiovascular changes from expiration to inspiration during IPPV

Area of Science:

• Cardiovascular Physiology
• Respiratory Physiology
• Ventricular Mechanics

Background:

• In vitro studies suggest that the ventricles influence each other's diastolic and systolic function.
• Ventricular interdependence is a known phenomenon, but its role during positive-pressure ventilation requires further in vivo investigation.

Purpose of the Study:

• To investigate ventricular interdependence in vivo using an animal model.
• To assess the impact of intermittent positive-pressure ventilation (IPPV) on right ventricular (RV) and left ventricular (LV) diastolic and systolic function.

Main Methods:

• Simultaneous measurement of RV and LV volumes and pressures, and esophageal pressure (EP) in 12 anesthetized dogs.
• Ventricular volumes were calculated using cineradiographic analysis of endocardial markers.
• Measurements were taken during intermittent positive-pressure ventilation (IPPV) at zero end-expiratory pressure, comparing end-expiration and peak inspiration phases.

Main Results:

• IPPV led to decreased EP, increased RV end-diastolic volume, and decreased LV end-diastolic volume, indicating reduced LV distensibility.
• RV ejection fraction and stroke volume increased during IPPV.
• LV ejection fraction and stroke volume decreased during IPPV, suggesting systolic interaction between the ventricles.

Conclusions:

• Ventricular interdependence plays a significant role in the cardiovascular response to intermittent positive-pressure ventilation.
• Increased RV diastolic volume negatively affects LV diastolic distensibility and systolic function.
• The findings highlight the complex interplay between the ventricles during positive-pressure ventilation.