In the 1970s, coronary care units (CCU) were created to provide a central location for patients with acute myocardial infarction to be treated where they could be rapidly defibrillated in case of an arrest. In the ensuing decades, the population of cardiology patients requiring CCU care has become considerably more complex, leading to an evolution from a limited CCU (focused only on cardiac dysfunction) to the modern cardiology intensive care unit (CICU) capable of treating the multi-organ dysfunction that so often afflicts our sickest patients.
Data from the Cardiac Critical Care Trials Network has shown that respiratory insufficiency is the most common indication for CICU admission and over half of all patients with cardiogenic shock require invasive mechanical ventilation.1,2 Given the large number of patients who experience respiratory failure, it is essential for all those who practice in a CICU to be comfortable managing respiratory support. At the University of Minnesota Critical Care Cardiology Education Summit, Dr. Carlos Alviar of New York University recently discussed management of positive pressure ventilation in the cardiovascular patient.
Positive pressure ventilation has significant effects on cardiac function and hemodynamics, effects which can differ depending on the underlying physiology of the patient.3 Positive pressure, most notably positive end-expiratory pressure (PEEP), acts to decrease venous return (left and right ventricular preload) and decrease LV afterload. PEEP generally increases pulmonary vascular resistance (PVR) and RV afterload through alveolar distension and vascular compression, although in patients with significant atelectasis and/or hypoxia, PEEP may improve V/Q matching and decrease PVR. Overall, PEEP may decrease cardiac output (CO) in patient who are preload-dependent (RV failure or tamponade), while in patients who are afterload-dependent (isolated LV failure), high PEEP may increase CO.
Randomized data regarding ventilator management in the CICU is lacking. Hyperoxemia has been shown to be detrimental in multiple settings, including in patients with acute MI.4 Low tidal volume ventilation reduces mortality in ARDS, although the PReVENT trial did not reproduce this among patients without ARDS.5 No specific mode of ventilation has been associated with improved outcomes.
Respiratory failure is one of the most common yet also most complex problems we encounter in the CICU. Successfully treating patients with respiratory failure in the CICU requires a deep understanding of both cardiopulmonary interactions and critical care fundamentals (such as sedation management) paired with frequent reassessment at the bedside. Ultimately, a tailored approach individualized for each patient is essential.
Dr. Eric Hall is a cardiology fellow at the University of Texas Southwestern and served as the CardioNerds Conference Scholar for the University of Minnesota Critical Care Cardiology Education Summit 2023.
To learn more about the complex interplay between mechanical ventilation and cardiopulmonary mechanics, please enjoy