The modern CICU has evolved to include patients with complex pulmonary mechanics requiring more non-invasive and mechanical ventilation. Series co-chairs Dr. Eunice Dugan and Dr. Karan Desai along with CardioNerds Co-founder Dr. Amit Goyal were joined by FIT lead, Dr. Sam Brusca, who has completed his NIH Critical Care and UCSF Cardiology fellow and currently faculty at USCF. We were fortunate enough to have two expert discussants: Dr. Burton Lee, Head of Medical Education and Global Critical Care within the National Institutes of Health Critical Care Medicine Department and master clinician educator with the ATS Scholar’s Critical Care for Non-Intensivists program, and Dr. Chris Barnett, ACC Critical Care Cardiology council member and Section Chair of Critical Care Cardiology at UCSF. In this episode, these experts discuss the basics of mechanical ventilation, including the physiology/pathophysiology of negative and positive pressure breathing, a review of ventilator modes, and a framework for outlining the goals of mechanical ventilation. They proceed to apply these principles to patients in the CICU, specifically focusing on patients with RV predominant failure due to pulmonary hypertension and patients with LV predominant failure. Audio editing by CardioNerds Academy Intern, student doctor, Shivani Reddy.
The CardioNerds Cardiac Critical Care Series is a multi-institutional collaboration made possible by contributions of stellar fellow leads and expert faculty from several programs, led by series co-chairs, Dr. Mark Belkin, Dr. Eunice Dugan, Dr. Karan Desai, and Dr. Yoav Karpenshif.
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Pearls and Quotes - Positive Pressure Ventilation in the CICU
Respiratory distress, during spontaneous negative pressure breathing can lead to high transpulmonary pressures and potentially large tidal volumes. This will increase both RV afterload (by increasing pulmonary vascular resistance) and LV afterload (by increasing LV wall stress).
An analogy for the impact of negative pleural pressure during spontaneous respiration on LV function is that of a person jumping over a hurdle. The height of the hurdle does not increase, but the ground starts to sink, so it is still harder to jump over.
Intubation in patients with right ventricular failure is a tenuous situation, especially in patients with chronic RV failure and remodeling (increased RV thickness, perfusion predominantly during diastole, RV pressure near or higher than systemic pressure). The key tenant to safe intubation is avoiding hypotension, utilizing induction agents such as ketamine or etomidate, infusing pressors, and potentially even performing awake intubations.
Non-invasive positive pressure ventilation in HFrEF has hemodynamic effects similar to a cocktail of IV inotropes, dilators, and diuretics. CPAP decreases pulmonary capillary wedge pressure (LV preload), decreases systemic vascular resistance (afterload), and increases cardiac output.
Airway pressure during mechanical ventilation is based on the “equation of motion”: Pressure = Volume/Compliance + Flow*Resistance + PEEP.
Our goals of oxygenation on mechanical ventilation include achieving acceptable PaO2/Sat with the lowest FiO2 possible (avoiding oxygen toxicity) and optimal PEEP (which increases oxygenation but can have detrimental impact on cardiac output)
Our goals of ventilation on mechanical ventilation include achieving acceptable pH and PaCO2 while preventing ventilator induced lung injury and avoiding auto-PEEP. We prevent lung injury by reducing tidal volume (ideally <8cc/kg, plateau pressure < 30 cmH20, driving pressure < 15 cmH20) and auto-peep by reducing respiratory rate (and allowin...
