Anyone who flies, even as a passenger, can benefit from a basic knowledge of aviation physiology. It can be life-saving, as I hope to show.  A detailed topic, but I will try to keep it short, sweet and practical. For those who want more details, a simple Google or Wikipedia search on the specific topic will provide it.
Understand that the usual study of physiology concerns itself with abnormal physiology in a “normal” environment. Aviation physiology is about normal physiology in an “abnormal” environment. In order to understand it, we need to understand that environment, i.e. the atmosphere.

Most flight takes place in 3 layers or “strata” of the earth’s atmosphere. The Troposhere extends from the surface of the earth to about 35000 feet over the poles, and 65000 feet over the equator (i.e. it is not uniform). It is very important in aviation because weather happens here. It is characterized by decreasing temperature at a rate of about 2 degrees C for every thousand feet of altitude until it reaches a low of about  -55 degrees C. At the top is a thin layer called the Tropopause which traps water vapour in the lower level.  The Stratosphere extends upward from the tropopause about 22 miles. It is characterized by a constant temperature of – 55 degrees C and no moisture (water vapour).

The first BLOG in this series was titled "The Checklist". It discussed how pilots were the first to recognize the importance of checklists and develop them for aviation. Checklists were soon developed for all phases of flight as well as for mechanical and technical aircraft procedures. They have proven invaluable and have prevented countless accidents and deaths. They have also been adopted by many other disciplines (such as medicine) due to their utility and effectiveness in preventing errors and ensuring the best possible outcomes in almost any given situation or set of circumstances.

More recently, a checklist has been developed for a vital aircraft operating component...the pilot. This checklist is as important and valuable as any of the other checklists. It should be used by the pilot for each and every flight. It is referred to as the "I'M SAFE" checklist and is generally introduced in the early portion of most flight training programs. The mnemonic stands for:
I: Illness
M: Medication
S: Stress
A: Alcohol
F: Fatigue
E: Eating and Emotion (The FAA defines "E" as Eating - to include proper nutrition and hydration) Some other international aviation authorities define "E" as Emotion - referring to emotional and psychological state.

For further information check out the excellent article by Sarina Houston, aviation contributor for about.com, The I'm SAFE Checklist, Pilot Risk Management:There's a Checklist for That  click hiere    

Sleep apnea refers to a condition in which a sleeping individual stops breathing. Eventually, due to physiologic factors such as a drop in the oxygen saturation of the blood, the brain rouses the individual (usually only partially) and breathing resumes. The severity of the sleep apnea is gauged by how often these episodes occur, how long each one lasts, how much the blood oxygen level drops and other factors. In severe cases, this may occur hundreds of times per night leading to extremely fragmented and abnormal, non-restorative sleep. This results in a state of chronic fatigue along with all the medical issues described in part 1.

There are 3 types of sleep apnea: OBSTRUCTIVE, CENTRAL AND COMPLEX.

OBSTRUCTIVE SLEEP APNEA (OSA) is the most common type of sleep apnea.  It describes the obstruction of the airway by the tongue and soft palate during the deeper stages of sleep in susceptible individuals.

CENTRAL SLEEP APNEA is due to the brain failing to signal breathing, even though the airway is open.

COMPLEX SLEEP APNEA is a combination of the above types.

The following signs and symptoms may be related to non-restorative sleep due to sleep apnea. Anyone displaying one or more to any significant degree should have a sleep study.

Although being overweight or obese (BMI over 35), or having a large neck circumference (16” or more in females and 17” or more in males) do not predict sleep apnea in and of themselves, they are often associated with sleep apnea particularly in individuals with any of the above listed signs or symptoms.

There are several methods available to successfully treat sleep apnea. Not all are effective in every individual. These include oral appliances, CPAP (continuous positive airway pressure) machines, Surgery and others. In all cases, weight loss is important if the individual is overweight. In many cases, no other treatment is required.

Any individual who has suffered significant sleep apnea and been successfully treated will describe how good it was to once again feel “normal” and energetic. In addition, many medical problems such as high blood pressure resolve with no further need for medication.

All of us want to sleep well, feel well, and function at our best. Individuals who have safety-sensitive occupations upon which the welfare of others depends (such as pilots, air traffic controllers, etc.) have a moral, ethical and legal obligation to ensure they are fit to perform their duties. This concept is often referred to as "Self-assessment". I would urge any individual who believes they may suffer from sleep apnea to seek the advice of a sleep specialist.

For further information click here.

Sleep well, be well.

E.A. Mastrangelo, M.D.

We need to sleep. Everyone knows this instinctively. It is important to everyone and is critical for people in safety sensitive occupations....such as pilots.

It has been relatively recent that medical science has begun to study sleep in an in-depth fashion. This may be in part due to the fact that few adequate research tools were available to do this type of research. Most studies were of an observational nature or studied changes in blood chemistry. New tools are now available (such as neuro-imaging) and hold promise with respect to enhancing our knowledge in this area.

Numerous questions still exist. Why is sleep important? What function(s) does sleep serve? What ill effects will occur as a result of sleep deprivation? Why do some individuals tolerate sleep deprivation better than others? How do medications and what we eat and drink affect sleep architecture? And many more.

I suppose the place to start is with the basic question "Why do we need to sleep"? The following is taken from an article of the same title found in the MedSleep newsletter,  "Sleep Matters" (Volume 4.1) 

The multiple Hypotheses proposed to explain the function of sleep reflect our incomplete understanding. It is likely that sleep evolved to fulfill some sort of primitive function and has taken on multiple functions over time. Animals are most vulnerable when they are asleep. Evolution moves to minimize vulnerability. This would argue that sleep remains an essential physiologic process across all species.

 These hypotheses include:

GROWTH AND RESTORATION (bodily growth and development in children, and tissue repair and restoration in adults) 
ONTOGENESIS (development of an organism from the earliest stage to maturity)
MEMORY PROCESSING (allows solidification of knowledge and memory)
WASTE CLEARANCE (clearance of metabolic waste products produced by neural activity of the awake brain).

For further reading and information about MedSleep click here 

Normal sleep is divided into 2 main stages--NREM (non rapid eye movement) and REM (rapid eye movement) sleep. NREM sleep is further divided into 4 stages--stages 1 through 4, each being a progressively deeper state of sleep such that progressively stronger stimuli is needed to wake someone from each stage. The stages are defined based primarily on the appearance of the EEG (electroencephalogram) in each stage.

Normally, NREM sleep occurs first, progressing through stages 1 to 4, and REM sleep follows. This cycle repeats itself 4 or 5 times during an 8-hour sleep period. With each cycle, the amount of time spent in REM sleep increases from perhaps 10 minutes or so in the first cycle to 60 minutes or more in the last cycle.

Sleep is a state of unconsciousness in which the brain is relatively more responsive to internal than external stimuli. It was once thought to be a passive state, but we now know (thanks to neuro-imaging technology) that it is a very active and vital state, absolutely necessary for the maintenance of health in every sense of the word.

This is an area of intense clinical research with numerous published studies. Sleep deprivation is not only detrimental to health, it can be fatal. Studies with rats have shown that total sleep deprivation resulted in death in a matter of weeks or months. The rats also lost weight despite eating more than the control group. They developed sores on their tails and paws indicating a failure of the immune system. (Sleep 1989 Feb:12(1):13-21). True, people are not rats. But numerous human studies have demonstrated a plethora of adverse effects associated with sleep deprivation in all areas: physical, mental and emotional.

In Part 2, I will discuss sleep apnea. In recent years this condition has received much attention in both the medical literature and the lay press....with good reason. It has been linked to all the adverse health conditions associated with sleep deprivation mentioned above. In addition, it has been implicated as the cause of numerous accidents...in the air, on the road, and in the workplace.

Sleep well.....Be well.
Armando

I selected "The Checklist" as the title of this blog because I value checklists. To be embarrassingly honest, I am a bit of an obsessive compulsive. I believe that, to a certain degree, this is a good thing in many fields. We all hope that any individual we put our trust in (pilot, doctor, design engineer, etc.) pays close attention to details. An oversight, even a seemingly insignificant oversight, can have disastrous consequences. Checklists have been shown in numerous studies to greatly reduce the risk of “accidents”. They have proven invaluable in many fields including medicine, but were initially developed for use in aviation by pilots. Checklists enhance safety in a simple manner. They do not add complexity.

The following is a description of the birth of the checklist, adapted from chapter 2 of Atul Gawande’s New York Times Bestseller, The Checklist Manifesto. How to Get Things Right. It will also be found in numerous historical accounts of the event.

On October 30, 1935 at Wright Air Field in Dayton Ohio, the U.S. Army Air Corps held a flight competition for manufacturers vying to build the military’s next-generation long range bomber. Many felt it was only a formality. The Boeing Corporation’s model 299 was the superior aircraft. It could fly faster and farther than previous bombers with 5 times the bomb capacity requested by the military.

With a small group of Army brass and corporation executives observing, the sleek and impressive model 299 test plane with a 103 foot wingspan and 4 engines (versus the usual 2), taxied into position. It roared down the runway, smoothly lifted off and sharply climbed to three hundred feet. Then it stalled, turned on one wing and crashed. Two of the five member crew were killed, including the pilot, Major Ployer P. Hill.

The accident investigation concluded there was no mechanical failure. The crash was attributed to “pilot error”. This new plane was more complex than previous aircraft. The pilot was required to attend to multiple tasks including each of the four engines, retractable landing gear, wing flaps, electric trim tabs requiring adjustment to maintain stability at different airspeeds, constant speed propellers requiring their pitch be regulated with hydraulic controls, and more. While performing all these tasks, Major Hill forgot to release a new locking mechanism on the elevator and rudder controls. The model was deemed by many as “too much airplane for one man to fly”.

Even so, the army purchased a few from Boeing. Some insiders remained convinced that the airplane was flyable. A group of test pilots set about the task of finding a solution.

What they decided against doing is almost as interesting as the solution they came up with. They decided against longer pilot training. They reasoned that few pilots, if any, had more experience and expertise than Major Hill, the air corps’ chief of flight testing. But this new plane was too complicated to be left to the memory of any one person, regardless of experience or expertise.

The simple, yet ingenious, solution they did come up with was……the pilot’s checklist! They designed checklists for each phase of flight….take off, flight, landing and taxiing. They were simple, brief, to the point and short enough to fit on an index card.

As aircraft (and spacecraft) have become more complex, the checklists have become even more important. 

For those readers interested in a more detailed and in depth study of the impact checklists have had in all areas of human endeavour, I strongly recommend The Checklist Manifesto--How to Get Things Right (2009) by Atul Gawande.

Everyone has personal experiences and everyone has a story to tell. We learn from experience. When it comes to bad experiences, it is wise to learn from the experience of those who have gone before us and heed their advice. This is why pilots have adopted the use of checklists and others have wisely followed.

 If you would like to share your knowledge and experience with the community in general, and the aviation community in particular, I welcome your contributions.  

Stay well. Stay safe.

Armando

This platform is intended to provide interesting and important information on various medical topics with particular emphasis on topics related to pilots and aviation medicine.

Today I would like to inform those of you who may not be aware, of the availability of free aeromedical training programs for general aviation pilots.

The FAA offers free aviation safety and physiology training courses to any person 18 years of age and over with a valid Class 1, 2, or 3 medical certificate. U.S. citizenship or residency is NOT a requirement. It is being graciously and generously offered to anyone wishing to attend. Security clearance must be obtained prior to arrival for the program. The only costs to the applicant are transportation and accommodation.

The programs are given at the Civil Aerospace Medical Institute (CAMI) located in the Mike Monroney Aeronautical Center in Oklahoma City, Oklahoma.

I had the pleasure and privilege of spending a day at CAMI during a recent Aviation Medical Examiners seminar in Oklahoma City. The educational staff was very knowledgeable and experienced with an obvious passion for their important work. There is no doubt in my mind that the existence of this program has prevented numerous aviation incidents and accidents and saved lives.

To the best of my knowledge, no similar program for general aviation civilian pilots exists in Canada. In my opinion, every pilot or student pilot would benefit greatly from such training.

For details on the program and application procedure click on the following links:

http://www.faa.gov/pilots/safety/pilotsafetybrochures/media/physiologc.pdf

http://www.faa.gov/pilots/training/airman_education/aerospace_physiology/cami_enrollment/how_to/
 

I have selected “THE CHECKLIST” as the title for this platform. The reason for this choice will be described in a future post.

Constructive comments and criticism regarding any posts are welcome. I will also consider posting suggestions or articles you might wish to provide. Simply e-mail me at

[email protected]

 

Stay well. Stay safe.

Armando

E. A. Mastrangelo M.D., CAME, AME