Jet Health

Once onboard a commercial jet aircraft headed to destination, the traveler faces the novel environment of the airplane cabin, in which a passenger's health may be impacted by the air quality and pressurization, among other prevailing conditions. Chronic health concerns may be exacerbated and new health issues may arise after spending hours sitting with limited mobility in the company of strangers and in contact with potentially contaminated surfaces and furnishings. Trauma associated with air turbulence, and syncope due to medication effects or other factors may lead to serious sequelae among aircraft passengers. Mental health issues may arise due to confined surroundings, overindulgence in alcoholic beverages, or taking new travel medications. The purpose of this chapter is to identify potential health risks associated with air travel and to discuss guidelines and optimal approaches to prevention. Over the past decade, enhanced emergency medical kits and automatic external defibrillators (AEDs) onboard some commercial airlines have allowed for successful resuscitation in cases of sudden cardiac death and other in-flight emergencies.

Cabin Air Quality

Regarding cabin air quality, there exist several well-known myths that supposedly contribute to poor air quality, including the beliefs that aircraft ventilation systems cause build-up of contaminants and pathogens and that decreased O ₂ levels and increased CO ₂ levels in the cabin result in adverse symptoms. These beliefs will be shown to be untrue as the determinants of cabin air quality are reviewed in detail below. Table 4.1 shows the five variables contributing to cabin air quality. Cabin air quality turns out to be relatively good when aircraft cabin ventilation systems are operating as designed and passengers have no cardiopulmonary co-morbidities.

TABLE 4.1

Variables Contributing to Cabin Air Quality

Pressurization Ventilation Contamination Humidity Temperature

Pressurization

Without major exception, the cabin environment is kept pressurized to 8000 ft (2400 m) above sea level. This is not an arbitrary flight level. It was chosen through research performed on pilots in early NASA (National Aeronautical and Space Agency, U.S.A.) studies and is felt to be the altitude that most of the general public can tolerate without exhibiting signs or symptoms of altitude sickness. This altitude maintains the average individual on the upper flat part of the oxygen dissociation curve ( Fig. 4.1 ).

Most healthy individuals will tolerate this altitude very well. However, literature on altitude sickness reveals a subset of the population who will be symptomatic. While the percentage of O ₂ remains the same at normal flight altitude as it does at sea level (21%), the partial pressure of O ₂ decreases from 103 mmHg to 69 mmHg at 8000 ft. This pressure will ensure that about 90% of all hemoglobin will be saturated in the healthy individual.

Despite that, those individuals with significant pathology such as chronic obstructive pulmonary disease (COPD), recent myocardial infarction (MI), or unstable angina might suffer significant decompensation from even minor alterations in their O ₂ dissociation curve. It is important for clinicians to consider this before allowing their patients to embark on a long voyage without supplemental oxygen. See the section below “ Supplemental Oxygen during Air Travel .” It is interesting to note that some of the next generation passenger aircraft, such as the Boeing 787 Dreamliner, are able to operate at the lower cabin altitude of 6000 ft due to the extensive use of composite materials in the fuselage, which are able to tolerate the higher pressurization.

Ventilation

The myth that aircraft ventilation contributes to poor quality of cabin air is completely unfounded. Depending on the type of aircraft, about half of the cabin air is recirculated. The other half is fresh air that is supplied by engine compressors, cooled by air-conditioning packs, and then blended with recirculated air. As a reference point, an office building may recirculate between 65 and 95% of its air. Older aircraft such as the Boeing 727 and McDonald-Douglas DC-9 do not recirculate air. It is only with the fuel crisis in the 1970s that modifications were made to newer aircraft to decrease the amount of fresh air brought into the cabin by the engines, thereby decreasing fuel consumption. It is of note that the fresh air brought into the cabin is virtually sterile.

Despite these modifications to newer aircraft, cabin air is exchanged in its entirety quite frequently. Consider the Boeing 767 used in both domestic and long-haul international versions. The cabin air is exchanged entirely every 2-3 minutes. Thus cabin air is exchanged approximately 20-30 times per hour. Compare that with the average household, which exchanges its volume only about five times per hour.

Clearly a very large volume of air enters and exits the cabin in a very short time. Without very precise modifications, passengers would experience severe drafts. Engineering modifications have reduced this “wind tunnel effect” by using laminar flow. Cabin air enters from air ducts running the length of the cabin overhead. Air supplied then exits at approximately the same row, thereby reducing airflow in fore and aft directions. This effectively limits the spread of passenger-generated contaminants ( Fig. 4.2 ).

Contamination

While the laminar flow serves to minimize spread of passenger-generated contaminants, the major barrier to particulate matter on all modern aircraft is the high-efficiency particulate air (HEPA) filter. This is the standard filter used in most hospital intensive care units, operating rooms, and industrial clean rooms. A rating is given on efficiency based on the ability of the filter to remove particles greater than 0.3 microns. For reference, bacteria and fungi are on the order of greater than 1 micron in size. Viruses, however, may range on the order of 0.003-0.05 microns. Less data exist on these organisms, but it is known that clumping of virus particles facilitates their removal via HEPA filters.

Studies have been done collecting air samples from various locations and assaying for microorganisms. Locations included municipal buses, shopping malls, sidewalks, downtown streets, and airport departure lounges. It was found that microbial aerosols in the aircraft cabin were much less than in other public locations. While there does exist a risk of disease transmission simply based on the number of passengers and the close proximity, it does not appear to be any greater aboard aircraft than that for any of the other modes of public transportation. Interestingly, aircraft cabin microbial aerosols were reported lower during night flights when presumably there was less passenger activity and were higher during daytime flights when passengers were more likely to get out of their seats to walk up and down the airplane aisle.

In addition to pathogenic organisms, the concern over other contaminants exists as well, including carbon dioxide, carbon monoxide, and ozone. Carbon dioxide levels have been equated with poor air quality in buildings and other public spaces. However, data collected on 92 different US flights found carbon dioxide, carbon monoxide, and ozone levels well below maximum Federal Aviation Administration (FAA) and Occupational Safety and Health Administration standards. Thus passenger symptoms of fatigue, headache, nausea, and upper respiratory tract irritation are likely to stem from other factors, including flight duration, noise levels, dehydration, and circadian dysrhythmia. The American Society of Heating Refrigeration and Air Conditioning Engineers has recently proposed Standard 161P, which makes recommendations for cabin air quality for all commercial passenger aircraft carrying 20 or more passengers.

You're Reading a Preview

Become a Clinical Tree membership for Full access and enjoy Unlimited articles

Become membership

If you are a member. Log in here