The arterial pressure waveform during acute ventricular failure and synchronized external chest compression

Area of Science:

• Cardiology
• Critical Care Medicine
• Biomedical Engineering

Background:

• Mechanical ventilation and intrathoracic pressure modulation are used for cardiac support.
• Acute ventricular failure (AVF) presents challenges in hemodynamic management.
• Systolic pressure variation (SPV) is a potential indicator of fluid responsiveness and cardiac function.

Purpose of the Study:

• To evaluate the effects of mechanical ventilation with and without synchronized external chest compression (SEC) on arterial pressure waveforms in AVF.
• To analyze the components of SPV (delta up and delta down) in response to ventilation and SEC.
• To determine if SPV analysis can differentiate the effects of increased intrathoracic pressure in cardiac failure.

Main Methods:

• Measurement of systolic pressure variation (SPV) during intermittent positive pressure ventilation (IPPV) in the presence of AVF.
• Evaluation of SPV changes with and without SEC.
• Assessment of SPV components (delta up, delta down) relative to baseline systolic pressure during apnea.
• Inclusion of volume loading conditions to simulate different physiological states.

Main Results:

• AVF significantly decreased SPV during IPPV alone, primarily due to a reduction in the delta down component.
• Volume loading further decreased SPV in AVF.
• SEC significantly increased overall SPV, delta up, and delta down during AVF without volume loading.
• During AVF with volume loading, SEC primarily increased the delta up component, indicating transient increases in left ventricular stroke output.

Conclusions:

• The disappearance of the delta down component of SPV is characteristic of congestive heart failure.
• Analysis of the arterial waveform, specifically SPV, is a valuable monitoring tool.
• This method can help differentiate the hemodynamic effects of increased intrathoracic pressure in patients with cardiac compromise.