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Air Quality and Infection Rate

Is there a relationship between the level of indoor air contamination and patient infection rate in healthcare facilities?

That seems to be a reasonable question. For many of us who are (or have been) closely associated with healthcare facilities and thus have developed an opinion on the subject, it may be an intensely important question. We want to know. We think we need to know. For some of us, such a relationship, if proven, could increase demand for our products and services.

As a result, when asked to write an article on the subject, I approached it with considerable enthusiasm. Although I had some understanding of the subject and thus have formed some strong opinions, I looked forward to contacting others in the field to update my beliefs with current research and findings.

I contacted a number of friends who are in a position to have opinions ranging from informed to expert on the subject. Each was asked the question at the beginning of this article. They were then asked to cite evidence supporting their answer. The answers ranged from: ‘There is no relationship whatsoever’ to ‘The higher the level of biologicals in the air the greater will be the number and severity of infections.’ Interestingly, in each case, the source given for the position taken was the experience and observations of the individual and/or that of others whom that individual respected. Not one individual was able to cite research or a study that supported his or her opinion. That is a common situation with issues around IAQ. Those in the field tend to have strongly held opinions but they tend to rise from personal observation and experience rather than research findings.

Infection Control History

Most experts on infection control will point to the work of Florence Nightingale during the Crimean War as the most significant research ever done on the causes and prevention of infections in health care facilities. At that time horrible infections and resulting high death rates were the norm rather than the exception. Any surgical procedure, no matter how minor, was life threatening. Nurse Nightingale had the radical (for the time) idea that a cleaner environment might result in an improved outcome for her patients. She urged those she worked with to clean themselves, the instruments they worked with and their surroundings between contacts with their patients. What resulted was a dramatic improvement in survival for the patients.

For the next half century, cleaning and scrubbing was virtually the total infection control strategy for healthcare facilities. Although cleanliness in healthcare is still emphasized, the development of broad-spectrum antibiotics during and following the Second World War brought a powerful new weapon to the fight against the spread of infections. It became possible to quickly halt the progress of an infection by administering antibiotics. Germs that once were a threat to life came to be regarded as minor inconveniences. When a patient was especially at risk or scheduled for surgery, they would be given a preventative dose of these new wonder drugs that would prevent most infections.

Infection Control Concerns Increasing Today

Unfortunately, bacteria and fungi appear to have an ability to adapt their genetic structure and evolve to slightly different forms from generation to generation. These new/old organisms are often resistant to the antibiotics that previously controlled them easily. Medical science has dealt with this by constantly developing new and more powerful antibiotics that can handle the new strains. In recent years, the evolving microbes have begun to win over science. Strains of certain organisms have been identified that appear able to continue to grow in human tissue no matter what drug or drug combination is administered.

As a result of this resistance, there has been a new interest in other factors that influence infection spread. Infection control practitioners tend to concentrate on hand washing. This is because person- to-person contact is believed to be the most common route of infection spread. Considerable attention has also been given to cleaning and disinfecting medical devices that come into direct patient contact or are introduced into the body. A number of studies have demonstrated that when strict hand washing and device reprocessing routines are followed, infection rates tend to be low. It takes constant education and close supervision, however, to enforce consistent compliance with procedures that result in the lowest infection rate. Most facilities feel that they can still make improvements in their level of compliance with such policies. As a result, the usual infection control improvement strategy centers around more frequent hand washing and improved handling of medical devices. Although a clean environment is considered important, environmental issues have not received high priority from the infection control community. Due to the limited available resources, only the highest priority issues receive a great deal of attention.

How Important is the Environment?

Does this mean that environmental factors are considered unimportant in healthcare? Not at all. Virtually all hospitals have policies that require cleaning and disinfecting of operating rooms between procedures, sleeping rooms between occupants, and examination rooms between patients. Terminal HEPA filtration is commonly used in HVAC systems supplying surgical and laboratory suites. Even in dentistry where infections are not normally a high concern, most offices have in recent years adopted policies of disinfecting both tools and environmental surfaces between patients. Given all of this evidence that healthcare providers are concerned about the potential of the environment to contribute to infection spread, it is puzzling that highly regarded authorities would hold the opinion that air quality has no relationship with infection rate.

It is helpful to bear in mind that such authorities are scientists. Their beliefs and opinions are driven by data. What to many may seem common sense or a prudent precaution will not hold weight with such individuals. Unless they have been shown evidence through a well-controlled study, they are trained to remain skeptical. Unfortunately, the relationship between environmental factors (including both air contamination and contamination of environmental surfaces) and infection rate has not been studied in a controlled manner. I recently asked Walter Bond of the Hospitals Infections Branch of CDC if he was aware of any such studies. He responded that such a study would be extremely difficult and expensive. There would be possibly hundreds of variables that would have to be measured and accounted for. He ventured an opinion that even if such a study were undertaken right now, it would be so complex that meaningful data would not start to be available for decades. It is doubtful that any study sponsor would be so patient. In addition, there would be serious ethical issues related to knowingly allowing patients to be exposed to an environment that is known to be contaminated in order to see if such exposure led to a greater infection rate.

Air Contamination is as Important as Surface Contamination

A study of the impact of indoor air quality on infection rate would be at least as complex as the above study. So it is unlikely that we will have scientifically developed data on the impact (or lack of it) of air on infection rate in the foreseeable future. How then do we answer the question that started this article? ‘Does contaminated air have an impact on infection rate in healthcare facilities?’ The common sense answer is that the impact of contamination in air is at least as important as contamination on environmental surfaces. So, if we are going to take precautions to clean and disinfect exam tables, chairs, patient rooms, and operating theaters, we should also take precautions to assure that the air is also clean and reasonably free from pathogens.

Naturally, there are some complications in attempting to apply the same standards to air cleanliness that we apply to environmental surfaces:

  • Soil on surfaces is easy to see. Untrained individuals will notice and have a negative reaction to environmental surfaces that are not clean. Air contamination is not visible to casual observers. The portions of an HVAC system that are likely to contain visible contamination are in mechanical rooms, above ceilings, or behind walls. Such contamination is not apparent on casual inspection. A healthcare administrator who would not tolerate any visible soil on surfaces may be totally unaware of the quality of air in the facility.
  • The standards for cleanliness of environmental surfaces were developed during the late nineteenth and early to mid twentieth centuries. At that time, forced air HVAC systems were just beginning to come on the scene. Few healthcare facilities had air conditioning. Natural ventilation was used extensively.
  • Proven and accepted procedures are available for quantifying the level of bacterial and fungal contamination on environmental surfaces. Testing for biologicals in air is much more difficult. Standardized procedures that yield consistent results are not yet in place.
  • How clean is clean enough? This is not yet defined for air. When an environmental surface is cleaned and disinfected, it is close to totally free of microbes. Achieving this level is not overly costly. Reducing the biological content of air to a like level could be quite costly. For air, the question of, ‘How clean is clean enough?’ becomes a much more important issue from a cost standpoint.

The above facts are unlikely to change in the near future. Therefore, it is incumbent on all of us who believe that good air quality is important to a well-rounded infection control program to accept responsibility for educating those who are not aware of the possibility of air as a source of contamination. At the same time, it is important that we use arguments that are reasonable and logical, acknowledging that our present knowledge is incomplete. Otherwise, we will be rightly accused of ‘scare mongering’ rather than providing information and services. We can not expect the infection control community to be either as knowledgeable or excited about air quality as we are until they become more knowledgeable. We must develop relationships with that community, share our knowledge, beliefs, and experiences and learn about their needs and concerns. Only then can we find common ground where we can develop useful standards for air quality in healthcare facilities that have broad support in the healthcare community.

Bob Baker is a member of ASHRAE and Chairman and CEO of BBJ Environmental Solutions, Inc., a manufacturing company specializing in providing clean air through environmentally responsible products.