Feasibility of Transvenous Phrenic Nerve Stimulation for Diaphragm Protection in Acute Respiratory Failure

Group 1: Acute hypoxemic respiratory failure (AHRF) Inclusion Criteria: * Age ≥18 years old, and, * Invasive mechanical ventilation for ≤ 7 days, and, * Have hypoxemia as defined by one of: * A PaO2:FiO2 ratio \< 300 and PEEP ≥ 5 cm H2O, or * SpO2:FiO2 \< 315% on PEEP ≥ 5 cm H2O in absence of an available arterial blood gas, and in the presence of a reliable Sp)2 trace and a SpO2 \< 97%, or * Are receiving inhaled nitric oxide for acute hypoxemia, or * Require extracorporeal membrane oxygenation, and, * Are on controlled mechanical ventilation with no patient-triggered ventilator-delivered breaths with no imminent plan to transition to assisted ventilation within 6 hours, and, * Are not expected to be liberated from mechanical ventilation within the next 48 hours (from time of enrollment) Group 2: Pulmonary endarterectomy Inclusion Criteria: * Age 18 to 65 years old * Are listed for pulmonary thromboendarterectomy * Have pulmonary vascular resistance \< 1000 dynes.sec.cm-5 Group 3: Lung transplant Inclusion Criteria: * Age 18 years or older * Are listed for bilateral lung transplant for a primary indication of idiopathic pulmonary fibrosis with no plan for concomitant transplant of other solid organs All groups Exclusion Criteria: * Pregnant or lactating * Previously diagnosed neuromuscular disorder or known phrenic nerve injury * BMI \>70kg/m2 * Implanted electronic cardiac or neurostimulation device in situ * Contraindications to left internal jugular or subclavi…