Thursday, July 14, 2005

Surgical masks - More Comfortable, Only Problem Is, They Don't Work

Finally, vindication for BrooklynDodger's dentist. For years we have argued about the worthless surigical masks worn by BD's D and staff; dentist maintains a filtering facepiece respirator makes him short of breath. The Dodger scoffed. Now comes a study showing actually heart rate effects comparing "N95 respirators" to "surgical masks." And it shows that surgical masks - which permit the wearer to inhale and exhale through the leaks - are less demanding and more comfortable than an N95.

The Dodger couldn't get the full text, and so can't figure what a "nanotreated" surgical mask [whatever that is] might be - let's assume it's a surgical mask with some kind of effective filter media. The Dodger also couldn't confirm whether or not the N95's had exhalation valves, although the Dodger suspects more not than likely. For all the inside out sampling, the investigators neglected to mention effectiveness in the abstract; the Dodger suspects it's not in the paper either

Infection control folks still don't get it that the main problem is fit, not filtration. Personally, BrooklynDodger doubts that microbes are riding on fine particles, although it would be nice to see some data on what's floating in the isolation unit.

On another matter, the Dodger is pleased that colleagues in the offshore world are making up for the declining output of American occupational health and safety science. The International Archives are making up for the near disappearance of the combined AIHA-ACGIH journal.

International Archives of Occupational and Environmental Health
Volume 78, Number 6
July 2005
Pages: 501 - 509
Short Communication

Effects of wearing N95 and surgical facemasks on heart rate, thermal stress and subjective sensations
Y. Li1 , H. Tokura1, Y.P. Guo1, A.S.W. Wong1, T. Wong2, J. Chung2 and E. Newton1
Institute of Textiles and Clothing, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
School of Nursing, The Hong Kong Polytechnic University, Kowloon, Hong Kong

Five healthy male and five healthy female participants performed intermittent exercise on a treadmill while wearing the protective facemasks in a climate chamber controlled at an air temperature of 25°C and a relative humidity of 70%. The subjects had significantly lower average heart rates when wearing nano-treated and untreated surgical facemasks than when wearing nano-treated and untreated N95 facemasks, ...the outer surface temperature of both surgical facemasks was significantly higher ... the microclimate and skin temperatures inside the facemask were significantly lower than those in both N95 facemasks... significantly higher absolute humidity outside the surface...... The absolute humidity inside the surgical facemask was significantly,... rated significantly lower for perception of humidity, heat, breath resistance and overall discomfort than both N95 facemasks. The ratings for other sensations, including feeling unfit, tight, itchy, fatigued, odorous and salty, that were obtained while the subjects were wearing the surgical facemasks were significantly lower...

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