title: Worsening Hypoxemia in the Face of Increasing PEEP: A Case of Large Pulmonary Embolism in the Setting of Intracardiac Shunt.
abstract: BACKGROUND Patent foramen ovale (PFO) are common, normally resulting in a left-to-right shunt or no net shunting. Pulmonary embolism (PE) can cause sustained increased pulmonary vascular resistance (PVR) and right atrial pressure. Increasing positive end-expiratory pressure (PEEP) improves oxygenation at the expense of increasing intrathoracic pressures (ITP). Airway pressure release ventilation (APRV) decreases shunt fraction, improves ventilation/perfusion (V/Q) matching, increases cardiac output, and decreases right atrial pressure by facilitating low airway pressure. CASE REPORT A 40-year-old man presented with dyspnea and hemoptysis. Oxygen saturation (SaO2) 80% on room air with A-a gradient of 633 mmHg. Post-intubation SaO2 dropped to 71% on assist control, FiO2 100%, and PEEP of 5 cmH20. Successive PEEP dropped SaO2 to 60-70% and blood pressure plummeted. APRV was initaiated with improvement in SaO2 to 95% and improvement in blood pressure. Hemiparesis developed and CT head showed infarction. CT pulmonary angiogram found a large pulmonary embolism. Transthoracic echocardiogram detected right-to left intracardiac shunt, with large PFO. CONCLUSIONS There should be suspicion for a PFO when severe hypoxemia paradoxically worsens in response to increasing airway pressures. Concomitant venous and arterial thromboemboli should prompt evaluation for intra-cardiac shunt. Patients with PFO and hypoxemia should be evaluated for causes of sustained right-to-left pressure gradient, such as PE. Management should aim to decrease PVR and optimize V/Q matching by treating the inciting incident (e.g., thrombolytics in PE) and by minimizing ITP. APRV can minimize PVR and maximize V/Q ratios and should be considered in treating patients similar to the one whose case is presented here.
authors.affiliation: Department of Internal Medicine, Health Science Center, Stony Brook University Hopsital, Stony Brook, NY, USA.
authors.forename: Glen T
authors.initials: GT
authors.lastname: Granati
authors.affiliation: Department of Internal Medicine, Health Science Center, Stony Brook University Hopsital, Stony Brook, NY, USA.
authors.forename: Getu
authors.initials: G
authors.lastname: Teressa
mesh_terms: D000328:Adult; D006348:Cardiac Surgical Procedures; D000072226:Computed Tomography Angiography; D018450:Disease Progression; D017548:Echocardiography, Transesophageal; D054092:Foramen Ovale, Patent / Q000150:complications / Q000175:diagnosis / Q000601:surgery; D006801:Humans; D000860:Hypoxia / Q000097:blood / Q000175:diagnosis / Q000209:etiology*; D008297:Male; D010100:Oxygen / Q000097:blood*; D011175:Positive-Pressure Respiration / Q000009:adverse effects*; D011655:Pulmonary Embolism / Q000097:blood / Q000150:complications* / Q000175:diagnosis
chemical_list: D010100:Oxygen