This study is a prospective randomized cross-over trial. Eligible, consenting participants will undergo 4 strategies of respiratory support: high-flow nasal cannula (HFNC) only, HFNC + continuous negative external pressure (CNEP) of 10 cmH2O, HFNC + CNEP of 20 cmH2O, HFNC + CNEP of 30 cmH2O. Throughout the study period, HFNC will be managed at a constant flow rate with fraction of inspired oxygen (FiO2) titrated to achieve goal oxygen saturation (SpO2) of 92-96%, measured via continuous pulse-oximetry. Each of the 4 strategies will be performed for 1 hour per strategy, interspersed with a 20-minute washout period of HFNC only. Participants will be randomized to the sequence of strategies for respiratory support.~A summary of the sequence of trial procedures is as follows:~Perform baseline measures.~Wait 5-10 minutes for recovery.~Initiate first random treatment assignment for up to 1 hour.~HFNC-only washout for 20 minutes~Initiate second random treatment assignment for up to 1 hour.~HFNC-only washout for 20 minutes~Initiate third random treatment assignment for up to 1 hour.~HFNC-only washout for 20 minutes~Initiate fourth random treatment assignment for up to 1 hour.~Return to usual care (HFNC only)~If a participant does not tolerate a given level of CNEP, the patient will be returned to HFNC for 5 minutes and then given the option to attempt that CNEP level again. If the patient declines reattempt or does not tolerate that CNEP level on reattempt, the HFNC-only washout will be instituted for 20 minutes before proceeding to the next protocol step.
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).