Tolerable Maximum Positive End Expiratory Pressure in Mechanically Ventilated Patients and Its Impact on Blood Flow across Cardiac Valves: Index Case Report of a Physiology Study

Introduction: Positive end expiratory pressure (PEEP) exerts variable effects on preload, pulmonary vascular flow, and afterload. Lung recruitment with gradual increase in PEEP improves oxygenation, but it may have variable cardiovascular effects. Method: A patient with respiratory failure from tetanus was recruited after informed consent. The sedated and paralyzed patient was subjected to sequential increase in PEEP with measurement of hemodynamics, ventilator parameters, and echocardiographic parameters (Doppler flow across tricuspid, pulmonic, and mitral valves at end inspiration and end expiration, in addition to blood volume flowing across RVOT and mitral valve). Results: We observed an initial rise in pulmonic and mitral blood flows, followed by a decline back to baseline around PEEP of 20, with an eventual decline associated with a drop in mean MAP