COVID-19 and other respiratory disease transmission during oxygen-therapy

We discuss effect of mitigation strategies on pathogen-laden aerosol transmissibility with experiments amenable to statistical analysis. For many patients with COVID-19, primary oxygen therapy is provided by either a nasal cannula (a tube with two prongs inserted into each nostril) or a simple O2 mask (a mask that fits over the lower half of a patients face). However, these devices produce exhalation jets and therefore can spread infection. Nonetheless, patients receiving oxygen by either of these methods rarely use further mitigation to prevent the spread of exhaled aerosols and droplets while being transported or treated in a healthcare facility. Our research team combined the expertise at the nonlinear physics research lab at Clark University with the knowledge and experience of respiratory therapists at Baystate Medical Center to produce visualizations of the exhalation patterns of a therapy-quality respiratory manikin with and without masks under a range of oxygen treatment conditions. Placing a surgical facemask loosely over the oxygenation device is demonstrated to deflect the direction of the exhalation jet downwards, although leaks can be observed from the bridge of the nose and from gaps between the face and mask sides. The primary method by which exposure is alleviated is by defecting the exhalation jets downward, away from the face of a clinician, and by preventing the exhalations from being launched directly over the patient and higher into the room. Less than 12% of the exhaled breath is observed to reach above the masked plane of a supine patient where a caregiver would be present, independent of oxygen flow rates. Our data can be used to calibrate models of respiratory disease spread including COVID-19, seasonal flu and tuberculosis.