MadSci Network: Medicine

Re: Can positive air pressure have a negative effect on humans?

Date: Mon Jun 11 15:35:36 2001
Posted By: Bernadette Baca, Health Physicist, Division of Reactor Safety
Area of science: Medicine
ID: 991422140.Me

To simply answer your question: yes, positive pressures can have a negative 
effect on humans.  However, the pressures necessary to do this are several 
times greater than that experienced in your facility.  These pressures are 
basically encountered during deep sea diving.  During a dive, a diver 
breathes air at the same pressure as the environment.  At a depth of 30 m 
(90 feet) the pressure placed on his body is 4 bar, whereas at the pressure 
at the surface is 1 bar.  This drastic change in positive pressure has the 
following effects on the body.

A common experience with respect to positive pressures exerted on the human 
body, or more specifically changes in pressure, is decompression sickness 
or " the bends".  During normal breathing, nitrogen, one of the main 
components of air (78%), is dissolved in the blood and body tissue.  When a 
diver starts breathing air under pressure, more nitrogen will dissolve 
until a new, higher nitrogen level is established.  At this level the 
partial nitrogen pressure in the blood and tissue is the same as the 
partial nitrogen pressure in the air - equilibrium.  When a diver surfaces, 
the depth equilibrium needs to be re-established with respect to the new 
depth.  The surplus of nitrogen in the blood and tissue has to be removed.  
Normally when a diver surfaces slowly, the nitrogen is transported by the 
blood to the lungs and is expelled during exhaling.  However, when there is 
to much nitrogen and the diver surfaces to quickly, nitrogen is forming 
small bubbles in the blood and in the tissue.  These small bubbles tend to 
stick together forming larger bubbles.  These bubbles can block veins, 
depriving the body parts from the necessary oxygen.  The symptoms the diver 
feels ranges from itchy skin and fatigue to serious mental problems as 
numbness, inability to speak, and even death.

Lung problems can also occur when a diver ascends while holding his breath.  
Since the air in his lungs was breathed at depth, the pressure is the same 
as the surrounding (water) pressure. When the diver ascends, the 
surrounding pressure decreases. When holding his breath, the air pressure 
in the divers lungs become larger with respect to the surrounding pressure 
and start to expand. Lungs cannot take to much pressure so they start to 
tear up. Air can enter tissue or the bloodstream. Over pressurizing can 
easily happen: ascending as low as 1 to 1.5 meter with full lungs can give 
rise to lung injuries. Especially in shallow water, the pressure drop 
(respective volume increase) per ascended meter is largest. 

A good site to offer more explanation on the physiological effects of 
positive pressure and significant changes in pressure on the human body is 
located at :

Despite there being actual negative effects on humans from positive 
pressures, they are typically encountered under more extreme circumstances 
rather than from increased building ventilation. 

There may be other factors which could contribute to the "irritability" 
experienced by you and your coworkers.  Other sources and factors could 
range from inadequate air quality, inadequate lighting, worker fatigue, 
stress, low morale, and possibly many other sources I can't think of.  With 
poor or inadequate air quality, despite excellent ventilation turn over you 
mentioned, if the air cleaning system does not work properly, health 
problems can still occur.  You can change over the air at increased rates 
but if a contaminant or irritant is recirculated through, it will continue 
to affect workers and other individuals until fully removed.  Stress is 
another factor we are only starting to learn of it's full range of effects.  
Even though the stress may not be physical in nature, mental stress can be 
overwhelming and possibly be passed on through negative attitudes, 
behaviors, and so on.  And one knows there is plenty of stress in a 
healthcare facility.  So not only can stress physically affect a person 
(high blood pressure, etc.), but the manner in which they cope may affect 
their coworkers as well. 

My suggestion is if the problem is significant, ask your supervisor to 
consider a study to help identify the problem - whether if it's poor air 
quality, poor morale, stress, or some other cause.

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