Exhaled air dispersion distances during noninvasive ventilation via different Respironics face masks.
BACKGROUND
As part of our influenza pandemic preparedness, we studied the exhaled air dispersion distances and directions through two different face masks (Respironics; Murrysville, PA) attached to a human-patient simulator (HPS) during noninvasive positive-pressure ventilation (NPPV) in an isolation room with pressure of -5 Pa.


METHODS
The HPS was positioned at 45 degrees on the bed and programmed to mimic mild lung injury (oxygen consumption, 300 mL/min; lung compliance, 35 mL/cm H(2)O). Airflow was marked with intrapulmonary smoke for visualization. Inspiratory positive airway pressure (IPAP) started at 10 cm H(2)O and gradually increased to 18 cm H(2)O, whereas expiratory pressure was maintained at 4 cm H(2)O. A leakage jet plume was revealed by a laser light sheet, and images were captured by high definition video. Normalized exhaled air concentration in the plume was estimated from the light scattered by the smoke particles.


RESULTS
As IPAP increased from 10 to 18 cm H(2)O, the exhaled air of a low normalized concentration through the ComfortFull 2 mask (Respironics) increased from 0.65 to 0.85 m at a direction perpendicular to the head of the HPS along the median sagittal plane. When the IPAP of 10 cm H(2)O was applied via the Image 3 mask (Respironics) connected to the whisper swivel, the exhaled air dispersed to 0.95 m toward the end of the bed along the median sagittal plane, whereas higher IPAP resulted in wider spread of a higher concentration of smoke.


CONCLUSIONS
Substantial exposure to exhaled air occurs within a 1-m region, from patients receiving NPPV via the ComfortFull 2 mask and the Image 3 mask, with more diffuse leakage from the latter, especially at higher IPAP.
Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Hong Kong, People's Republic of China. Electronic address: dschui@cuhk.edu.hk.
David S
DS
Hui
Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Hong Kong, People's Republic of China; Center for Housing Innovations, The Chinese University of Hong Kong, Hong Kong, People's Republic of China.
Benny K
BK
Chow
Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Hong Kong, People's Republic of China.
Susanna S
SS
Ng
Institute of Space and Earth Information Science, and the Department of Anesthesia and Intensive Care, The Chinese University of Hong Kong, Hong Kong, People's Republic of China.
Leo C Y
LCY
Chu
School of Mechanical Engineering, The University of New South Wales, Sydney, NSW, Australia.
Stephen D
SD
Hall
Institute of Space and Earth Information Science, and the Department of Anesthesia and Intensive Care, The Chinese University of Hong Kong, Hong Kong, People's Republic of China.
Tony
T
Gin
Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Hong Kong, People's Republic of China.
Joseph J Y
JJY
Sung
Institute of Space and Earth Information Science, and the Department of Anesthesia and Intensive Care, The Chinese University of Hong Kong, Hong Kong, People's Republic of China.
Matthew T V
MTV
Chan
D000388:Air; D016902:Air Pollution, Indoor; D004867:Equipment Design; D045853:Exhalation; D006801:Humans; D007251:Influenza, Human / Q000635:transmission; D008397:Masks; D016544:Patient Simulation