Does a positive end-expiratory pressure-induced reduction in stroke volume indicate preload responsiveness? An...

Area of Science:

• Critical care medicine
• Cardiovascular physiology
• Mechanical ventilation

Background:

• Positive end-expiratory pressure (PEEP) can depress cardiovascular function, often necessitating fluid loading.
• Stroke volume (SV) reduction with PEEP may indicate hypovolemia or preload responsiveness.

Purpose of the Study:

• To evaluate the relationship between cardiovascular response to PEEP and fluid loading.
• To assess if SV reduction by PEEP predicts fluid responsiveness using the Frank-Starling relationship.

Main Methods:

• A porcine model was used to assess cardiovascular responses at varying PEEP levels (0, 10, 20 cm H2O) and fluid volumes (hypovolemia, normovolemia, hypervolemia).
• Measurements included SV, cardiac output, intrathoracic blood volume, and various pressure and diameter variations.

Main Results:

• A 10 cm H2O PEEP significantly decreased SV in hypovolemic and normovolemic states, but not in hypervolemia.
• SV increased with fluid administration from hypovolemia to normovolemia and 10% hypervolemia.
• The predictive value of SV decrease by PEEP for fluid responsiveness varied (60-88% sensitivity, 67% specificity) based on volemic status.

Conclusions:

• Changes in SV due to PEEP may predict preload responsiveness.
• The individual response of SV to PEEP and fluid administration depends on the heart's position on the Frank-Starling curve.