The decrease of cardiac chamber volumes and output during positive-pressure ventilation

Abstract

Positive-pressure ventilation (PPV) is widely used for treatment of acute cardiorespiratory failure, occasionally at the expense of compromised cardiac function and arterial blood pressure. The explanation why has largely rested on interpretation of intracardiac pressure changes. We evaluated the effect of PPV on the central circulation by studying cardiac chamber volumes with cardiac magnetic resonance imaging (CMR). We hypothesized that PPV lowers cardiac output (CO) mainly via the Frank-Starling relationship. In 18 healthy volunteers, cardiac chamber volumes and flow in aorta and the pulmonary artery were measured by CMR during PPV levels of 0, 10, and 20 cmH2O applied via a respirator and a face mask. All cardiac chamber volumes decreased in proportion to the level of PPV. Following 20-cmH2O PPV, the total diastolic and systolic cardiac volumes (±SE) decreased from 605 (±29) ml to 446 (±29) ml (P < 0.001) and from 265 (±17) ml to 212 (±16) ml (P < 0.001). Left ventricular stroke volume decreased by 27 (±4) ml/beat; heart rate increased by 7 (±2) beats/min; and CO decreased by 1.0 (±0.4) l/min (P < 0.001). From 0 to 20 cmH2O, right and left ventricular peak filling rates decreased by -146 (±32) and -187 (±64) ml/s (P < 0.05) but maximal emptying rates were unchanged. Cardiac filling and output decrease with increasing PPV in healthy volunteers. The decrease is seen even at low levels of PPV and should be taken into account when submitting patients to mechanical ventilation with positive pressures. The decrease in CO is fully explained by the Frank-Starling mechanism.

Pulmonary hypertension in the intensive care unit. Expert consensus statement on the diagnosis and treatment of paediatric pulmonary hypertension. The European Paediatric Pulmonary Vascular Disease Network, endorsed by ISHLT and DGPK

“…Manoeuvres triggering pulmonary hypertensive crises such as insufficient sedation, rise of pCO 2 or suctioning should be avoided. Moreover, positive pressure ventilation impairs cardiac filling and output22 especially in the failing RV. Normoventilation (pCO 2 -levels 35–40 mm Hg) and long expiratory times are recommended.…”

Optimal perioperative management of arterial blood pressure

“…Mechanical ventilation, especially positive end-expiratory pressure, decreases the blood volume in the intrathoracic vascular bed and heart, and decreases cardiac filling and cardiac output via the Franck-Starling relationship 64,65. In fact, mechanical ventilation decreases right ventricular preload (venous return), and increases right ventricular afterload (pulmonary vascular resistance) and left ventricular afterload.…”

Role of cardiovascular imaging in selection of donor hearts

“…In a small study done in infants on highfrequency oscillatory ventilation showed no adverse effects as compared to controls [27] . The effect of positive pressure ventilation on the cardiac output and cardiac volumes have been found to be significant in agreement with the FrankStarling law [28] and this must be taken into consideration while evaluating donor hearts by cardiac MRI. Considering the versatility of cardiac magnetic resonance imaging (CMRI) in assessing cardiac function and its feasibility in mechanically ventilated patients cardiac MRI protocols need to be instituted and actively used in evaluating donor hearts.…”