This study is being conducted to evaluate if wearing a non-invasive breathing support device over the chest/abdomen improves markers of breathing in patients with lung injury requiring high-flow oxygen. The breathing support device consists of a plastic shell that sits over the chest and abdomen and connects to a vacuum that helps the chest expand with breathing. This breathing support is known as continuous negative external pressure (CNEP). Study findings will help determine if this breathing support device might be useful for patients with acute hypoxemic respiratory failure (AHRF).
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)
Do-not-intubate order
Anatomical factor predisposing to poor fit of cuirass (e.g. severe kyphosis or scoliosis)
Clinically prescribed prone positioning
Tense ascites
Crossover
HFNC only
DeviceHFNC for 45 minutes, with FiO2 titrated to SpO2 of 90-97%
HFNC + CNEP10
DeviceHFNC with CNEP of 10 cmH2O for 45 minutes, with FiO2 titrated to SpO2 of 90-97%
HFNC + CNEP20
DeviceHFNC with CNEP of 20 cmH2O for 45 minutes, with FiO2 titrated to SpO2 of 90-97%
HFNC + CNEP30
DeviceHFNC with CNEP of 30 cmH2O for 45 minutes, with FiO2 titrated to SpO2 of 90-97%
Change from baseline in SpO2/FiO2
The change in SpO2/FiO2 within each participant as measured at baseline and at the end of each treatment assignment period. The average SpO2/FiO2 over the last five minutes of the treatment period will be used.
Change from baseline in Respiratory Rate
The change in Respiratory Rate within each participant as measured at baseline and at the end of each treatment assignment period. The average Respiratory Rate over the last five minutes of the treatment period will be used.
Change from baseline in ROX Index
The change in ROX index within each participant as measured at baseline and at the end of each treatment assignment period. ROX index is calculated as SpO2/FiO2 divided by the Respiratory Rate. The average ROX index over the last five minutes of the treatment period will be used.
Change from baseline in Transcutaneous Carbon Dioxide (CO2)
The change in Transcutaneous Carbon Dioxide within each participant as measured at baseline and at the end of each treatment assignment period. The average Transcutaneous Carbon Dioxide over the last five minutes of the treatment period will be used.
Change from baseline in Heart Rate
The change in Heart Rate within each participant as measured at baseline and at the end of each treatment assignment period. The average Heart Rate over the last five minutes of the treatment period will be used.
Change from baseline in other components of the Multidimensional Dyspnea Profile
The change in other components of the Multidimensional Dyspnea Profile within each participant as measured at baseline and at the end of the study. At end of study, participants will be instructed to consider their breathing on average during CNEP to obtain the post-baseline measure.
Change from baseline in Tidal Volume
The change in Tidal Volume within each participant as measured at baseline and at the end of each treatment assignment period, estimated from lung electrical impedance tomography. The average Tidal Volume over the last five minutes of the treatment period will be used.
Change from baseline in End-Expiratory Lung Volume
The change in End-Expiratory Lung Volume within each participant as estimated from end-expiratory lung impedance measured at baseline and at the end of each treatment assignment period. The average End-Expiratory Lung Impedance over the last five minutes of the treatment period will be used to derive change in end-expiratory lung volume.
Change from baseline in Minute Ventilation
The change in Minute Ventilation within each participant as measured at baseline and at the end of each treatment assignment period, estimated from lung electrical impedance tomography. The average Minute Ventilation over the last five minutes of the treatment period will be used.
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