Do Saliva-Saturated Spit Hoods Interfere With Ventilation?

Spit hoods are used by law enforcement, officers in correctional facilities, and medical personnel during the restraint of agitated subjects that are actively spitting to prevent the transmission of droplet-transmitted pathogens. We could find no studies reporting on the time course of normal breathing to clear saliva from such a saturated spit hood. We purchased samples of 3 popular spit hood models and applied a section over the output of a pneumatic test system. We used a digital anemometer, digital manometer, and an inline controllable fan for back pressure and flow. The pressure was 3 mm Hg to match quiet breathing. The tested area was saturated with artificial saliva, and air pressure was applied while we recorded the pressure and airflow. Within 5 seconds, the spit hoods all cleared sufficient artificial saliva to allow 1 m/s of airflow, which exceeds that of an N95 mask with similar pressure. Commonly used spit hoods offer very low resistance to breathing even after being initially saturated with artificial saliva. Our results do not support the hypothesis that a saliva-filled spit hood might contribute to death.