What is the effect of wearing a surgical mask or an N95 mask on patients with stable chronic hypercapnic respiratory failure currently using non-invasive ventilation? A randomised cross-over trial

This is a randomised, cross-over design study with 3 experimental arms i) no mask, ii) a surgical mask and iii) an N95 mask. The intervention will be delivered by specialist Respiratory Physiotherapists and participants will be done 1 by 1. Each experimental condition will last a maximum of 20 minutes or as long as tolerated by the participant. A washout period of at least 10 minutes between experimental conditions will also occur with the participant returning to baseline SpO2, RR and mBORG. Prior to the study, demographics of all participants would be recorded including age, gender, primary diagnosis, diagnostic group, mean usage (hours) over the past 28 days and duration of NIV prescription (months). Spirometry in the seated position will be performed, measuring FEV1 and FVC. This will be performed using a mouth piece and nose clip; if there is inadequate lip seal a face mask will be used. Three measurements will be performed with the best effort recorded. Sudden nasal inspiratory pressure (SNIP) will also be measured with the contralateral nostril occluded over 5 trials with the best value used. The Multidimensional Profile (MDP) and mBORG will also be explained to the participant. The participant will then be seated in a comfortable position, with finger oximetry (SpO2) (Radical-97, Masimo, CA) and transcutaneous carbon dioxide (TcCO2) (Sentec, Switzerland) monitoring commenced. An ear probe will be used for TcCO2 monitoring with the temperature probe set to 42 degrees Celsius. Heart rate (HR) will be recorded from the oximeter recording while respiratory rate will be obtained from respiratory bands placed around the participant’s upper chest and abdomen and recorded by a polygraphy (Alice 4 or Alice PDx systems, Philips, PA). All monitoring will be continuous throughout the study. There will be concealed allocation for the randomisation of the test order of mask conditions (no mask, surgical mask (Primagard Procedure Mask with Earloop Blue PM4-306) or N95 mask (3M Aura) will occur, using block randomisation via REDCap (Research Electronic Data Capture). Participants will be fitted with a three-panel flat-fold type N95 mask (3M Aura 1870). A fit check will be performed with the participant asked to rapidly breathe in and then out. If air leaks are obvious after optimisation of nasal wire and head strap position, an alternative N95/P2 mask will be trialled and documented. The protocol will commence with a 10-minute settling period sitting quietly. In the final minute the mBORG score will be recorded along with baseline SpO2, TcCO2, RR and HR. The first experimental condition will then commence with the participant instructed to sit quietly and not talk or sleep. They may however read. mBORG will be recorded at 5-minute intervals and at test cessation if unable to tolerate 20 min. During the final minute of the 20-minute experimental condition (or the longest period the participant can tolerate), the TDI will be administered. During the beginning of the 10-minute recovery period, the MDP will be completed. After a minimum 10-minute recovery period once SpO2, RR and TcCO2 have returned to baseline, the next allocated experimental condition will be undertaken, followed by another recovery period and then the final allocated experimental condition followed by final recovery period. The TDI and MDP will be administered at the end of each experimental condition as outlined above. At the conclusion of the experimental conditions the participant will be asked some simple questions about mask preference, factors contributing to tolerance and current mask practices. These questions are listed in the data collection form.