Physiological Effects of Continuous Negative External Pressure for Acute Hypoxemic Respiratory Failure

Inclusion Criteria:

* Age 18 years or older
* Acute hypoxemic respiratory failure
* Non-cardiogenic airspace opacities on chest radiograph or computed tomography (CT) scan
* High-flow nasal cannula (flow ≥ 30 LPM) initiated within last 96 hours (4 days)
* FiO2 ≥ 40%
* SpO2 ≥ 92%

Exclusion Criteria:

* Do-not-intubate order
* Anatomical factor predisposing to poor fit of cuirass (e.g. severe kyphosis or scoliosis)
* Use of cuirass precluded, e.g. due to:

  * Clinically prescribed prone positioning
  * Tense ascites
  * Severe abdominal pain
  * Abdominal wound or surgery
  * Pregnancy
  * Agitated delirium
* Prior intubation during hospital stay
* Cardiogenic pulmonary edema
* Exacerbation of asthma or COPD
* Chronic lung disease, including:

  * Interstitial lung disease
  * Cystic fibrosis
  * Lung mass, lung cancer, or metastasis to the lung
  * Lung transplant recipient
  * Any disease that requires home oxygen
* Glasgow coma score \< 15
* Chest tube, pneumothorax, or pneumomediastinum
* Hemodynamic instability (mean arterial pressure \< 55 mmHg or norepinephrine-equivalent vasopressor requirement \> 0.1mcg/kg/min)
* Implantable electrical device (e.g. pacemaker, defibrillator, neurostimulator)
* Unreliable pulse-oximetry tracing
* Imminent intubation
* Anticipated lack of patient availability to complete study procedures (e.g. due to planned clinical procedure such as CT scan or dialysis during potential time of study)
* Attending physician refusal