THE EFFECTS OF ALTITUDE ON HUMAN PHYSIOLOGY Essay Example

system is responsible for bringing oxygen into the body and transferring it to the cells where it can be utilized for cellular activities. It also removes carbon dioxide from the body. The respiratory system draws air initially either through the mouth or nasal passages, which join behind the hard palate to form the pharynx. At the base of the pharynx are two openings - one leading to the digestive system (esophagus) and another leading to the lungs (glottis). The glottis is covered by the epiglottis when swallowing, preventing food from entering the lungs. When not covered, air freely passes into and out ofthe trachea.

The trachea, commonly referred to as the "windpipe", splits into two bronchi that subsequently branch out into the lungs. Inside the lung, the bronchi continue dividing and give rise to smaller bronchioles, which eventually culminate in tiny sacs called alveoli.

The alveoli are the site where oxygen is transferred to the blood.

The alveoli are sacs that resemble inflated sacs and perform gas exchange through a membrane. The exchange of oxygen into the blood and carbon dioxide out of the blood depends on three main factors: 1) the partial pressure of the gases, 2) the area of the pulmonary surface, and 3) the thickness of the membrane (Gerking, 1969). The alveoli contain membranes that provide a sizable surface area for efficient gas exchange. The thickness of the pulmonary membrane is typically thinner than a red blood cell. Changes in altitude do not directly impact the pulmonary surface or the thickness of alveolar membranes. However, altitude does directly affect the partial pressure of oxygen, which then influences gas transfer within the alveoli.

GAS TRANSFER
To

comprehend gas transfer, it is crucial to initially comprehend the behavior of gases. Each gas in our atmosphere exerts its own pressure and functions autonomously from the rest. As a result, the term partial pressure indicates the contribution of each gas to the overall atmospheric pressure. The average pressure of the atmosphere at sea level is approximately 760 mmHg.

The pressure is sufficient to uphold a 760 mm high column of mercury (Hg). To determine the oxygen's partial pressure, begin with the atmospheric oxygen percentage, approximately 20%. Hence, oxygen will account for 20% of the overall atmospheric pressure at any given level. At sea level, the total atmospheric pressure is 760 mmHg, resulting in an approximate partial pressure of O2 of 152 mmHg.

760 mmHg multiplied by 0.20 equals 152 mmHg.
A similar calculation can be done for CO2 if the concentration is estimated to be around 4%. The partial pressure of CO2 would then be approximately 0.304 mmHg at sea level.

The process of gas transfer in the alveoli is governed by simple diffusion, which refers to the movement of molecules along a concentration gradient, from areas of higher concentration to areas of lower concentration. This movement is a result of collisions between molecules, with higher concentration areas experiencing more collisions. As a net effect, molecules move towards areas of lower concentration.

Table 1 demonstrates that the concentration gradient facilitates the diffusion of oxygen into the blood and carbon dioxide out of the blood (Gerking, 1969). Table 2 illustrates the decline in partial pressure of oxygen with increasing altitudes (Guyton, 1979).

Table 1

ATMOSPHERIC AIRALVEOLUSVENOUS BLOOD

OXYGEN152 mmHg (20%)104 mmHg (13.6%) 40 mmHg

CARBON

DIOXIDE 0.304 mmHg (0.04%)40 mmHg (5.3%) 45 mmHg

Table 2

ALTITUDE (ft.) BAROMETRIC PRESSURE (mmHg)Po2 IN AIR (mmHg)Po2 IN ALVEOLI

(mmHg) ARTERIAL OXYGEN SATURATION (%)

0 760159*104 97


10,00052311067 90


20,000349734070


30,000226472120


40,0001412985


50,000871811

*this value differs from table 1 because the author used the value for the concentration of O2 as21%.

The value chosen for table 1 by the author is 20%.

CELLULAR RESPIRATION

In a normal, non-stressed state, the respiratory system transports oxygen
from the lungs to the cells of the body where it is used in the process of
cellular respiration. Under normal conditions this transport of oxygen is
sufficient for the needs of cellular respiration. Cellular respiration
converts the energy in chemical bonds into energy that can be used to power
body processes. Glucose is the molecule most often used to fuel this process
although the body is capable of using other organic molecules for energy.

Internal respiration, also referred to as the transfer of oxygen to body tissues, is a complex chemical process that enables the breakdown of glucose into usable energy known as ATP (adenosine triphosphate) (Grollman, 1978). The three primary steps involved in this process include: 1) glycolysis, 2) Krebs cycle, and 3) electron transport system. The efficient functioning of these steps necessitates the presence of oxygen. In the absence of oxygen, energy production must occur anaerobically through lactic acid fermentation. This alternative pathway produces significantly less ATP (2 instead of 36/38). However, relying on this inefficient pathway rapidly depletes the available glucose supply and is not a sustainable long-term solution for providing energy to the body without sufficient oxygen.

The supply of oxygen to the tissues relies

on three factors: 1) the lung's ability to efficiently oxygenate blood, 2) the efficient delivery of oxygen by blood to the tissues, and 3) the efficient transfer of hydrogen to molecular oxygen by respiratory enzymes within cells (Grollman, 1978). Inadequacy in any of these areas can result in insufficient oxygen supply to body cells. Insufficient oxygen supply poses challenges for the body at higher altitudes.

Anoxia is a condition where cells lack enough oxygen. It can also be referred to as hypoxia, which indicates an oxygen debt. Anoxic anoxia specifically relates to the inadequate oxygenation of blood in the lungs, which becomes a concern at higher altitudes with decreased O2 pressure. Other types of oxygen deficiencies include anemic anoxia (insufficient transportation of oxygen by the blood), stagnant anoxia (slowing down of the circulatory system), and histotoxic anoxia (impaired function of respiratory enzymes).

Anoxia can occur temporarily during normal respiratory system regulation of changing cellular needs, such as when climbing a flight of stairs. The increased oxygen demand of the cells in providing the mechanical energy required to climb ultimately results in a local hypoxia in the muscle cell. The first noticeable response to this external stress is typically an increase in breathing rate, known as increased alveolar ventilation.

The rate of our breathing is determined by the need for O2 in the cells, and it is also the first response to hypoxic conditions.

BODY RESPONSE TO ANOXIA

When the rate of alveolar respiration is insufficient to meet the cells' oxygen requirements, the respiratory system reacts by inducing overall vasodilation. This leads to an increased blood flow within the circulatory system.

The sympathetic nervous system causes vasodilation in the skeletal

muscle, leading to increased blood flow. This happens when the precapillary sphincters open at the capillary level. Moreover, both heart rate and stroke volume rise, although the latter does not significantly increase in non-athletes. Regular exercise and physical conditioning have notable advantages, particularly for individuals exposed to high altitudes. The adrenal medulla releases catecholamines, which directly enhance myocardial contraction and raise heart rate. The kidneys release renin, resulting in angiotensin production, which elevates blood pressure and pushes more blood into the capillaries. These responses are a normal reaction to external stressors; however, if the body's normal responses cannot meet cells' oxygen demand, it can lead to Acute Mountain Sickness (AMS). AMS is commonly experienced at high altitudes.According to Princeton (1995), individuals at elevations above 10,000 feet may experience mild symptoms. The occurrence of acute mountain sickness (AMS) depends on factors such as elevation, ascent rate, and individual susceptibility.

Acute Mountain Sickness (AMS) can be classified into three categories: mild, moderate, or severe, depending on the symptoms that are experienced. When people acclimatize to higher altitudes, they may experience mild AMS. In these cases, AMS symptoms typically start 12-24 hours after reaching higher altitudes and gradually improve by the third day. Symptoms of mild AMS include headaches, dizziness, fatigue, shortness of breath, loss of appetite, nausea, disrupted sleep patterns, and a general feeling of unease (Princeton University Press, 1995). These symptoms often worsen at night when breathing slows down during sleep.

Mild AMS does not hamper regular activities and symptoms typically diminish on their own as the body adjusts to the higher altitude.

Moderate Acute Mountain Sickness (AMS) comprises of a severe headache that is not alleviated by

medication,

nausea and vomiting, increasing weakness and fatigue, shortness of breath,

and decreased coordination known as ataxia (Princeton, 1995). Engaging in normal activities

becomes challenging during this stage of AMS, although the person may still be capable

of walking on their own. To determine moderate AMS, a test involves asking the individual

to walk in a straight line heel to toe. If they have ataxia, they will be

unable to complete this task. Immediate descent is necessary if ataxia is observed. In hiking or climbing scenarios, it is

essential to ensure that the affected individual descends before their ataxia worsens

to the point where independent walking becomes impossible.

Severe Acute Mountain Sickness (AMS) presents intensified symptoms compared to mild and moderate AMS. It includes severe difficulty in breathing at rest, inability to walk, decreased mental alertness, and potential accumulation of fluids in the lungs.

ACCLIMATIZATION
There is no real cure for Acute Mountain Sickness other than
acclimatization or
descending to a lower altitude. Acclimatization is the process, over time, in which
the body adapts to the decrease in oxygen molecules' partial pressure at a
higher altitude. The main cause of altitude illnesses is a sudden increase in
elevation without sufficient time for acclimatization. The acclimatization process typically takes 1-3 days at the new altitude. It involves several changes in the body's structure and function. Some of
these changes occur immediately as a response to decreased oxygen levels,
while others are slower adaptations. Some of the most significant changes
include:
- The chemoreceptor mechanism increasing the depth of alveolar ventilation. This
allows for a 60% increase in ventilation (Guyton, 1969). This is an
immediate response to oxygen debt. Over several weeks, the capacity to increase alveolar ventilation may increase by

600-700%.

When at sea level, the pressure in the pulmonary arteries is elevated, causing blood to be directed into areas of the lungs that are typically not utilized for breathing.

The bone marrow generates extra red blood cells for the purpose of carrying oxygen throughout the body.

It may take a few weeks for this process. People living at higher altitudes usually have a red blood cell count that is 50% higher than the average.

According to Tortora (1993), the body produces more of the enzyme 2,3-biphosphoglycerate. This enzyme aids in releasing oxygen from hemoglobin to the body tissues.

Dehydration, over-exertion, alcohol, and the consumption of other depressant drugs can impede the acclimatization process. Furthermore, there may be long-term changes that result in alveoli enlargement and thinning of alveoli membranes. These changes improve gas transfer.

To alleviate mild symptoms of AMS, headache pain medications can be used for treatment.

Some doctors may suggest using Diamox (Acetazolamide) medication. Both Diamox

and headache medicine seem to lessen symptoms' severity but do not

treat the underlying issue of oxygen shortage. However, Diamox might enable the

individual to metabolize more oxygen by increasing their breathing rate. This is particularly

beneficial at night when their respiratory drive decreases. To allow for the medication to take effect, it is advisable to start taking it 24 hours

before reaching high altitudes. The Himalayan Rescue

Association Medical Clinic recommends a dosage of 125 mg.

According to a 1995 study from Princeton, the recommended dosage for this medication is 250 mg twice daily. The effectiveness of the lower dose, 125 mg, is found to be similar. However, both doses may have potential side effects including tingling of the lips and fingertips, blurring of vision, and changes in taste.

It is believed that these side effects can be reduced by taking the 125 mg dose.

When the drug is stopped, the side effects go away. If a person is allergic to sulfa drugs like penicillin, they should not take Diamox, which is a sulfonamide drug. People who have never had an allergy to Diamox or sulfa may still have severe allergic reactions to it. Before going to a remote area where it may be difficult to manage a severe allergic reaction, it is common practice to try taking the drug first. Recent data from the University of Iowa in 1995 suggests that combining Diamox with Dexamethasone medication can help reduce the risk of mountain sickness.

Moderate acute mountain sickness (AMS) can be treated with advanced medications or by descending to a lower altitude. Even a small decrease in elevation may offer some relief, but greater improvement can be achieved by descending 1,000-2,000 feet. Spending 24 hours at the lower altitude will lead to significant improvements. It is recommended that the individual stay at a lower altitude until symptoms have completely resolved, which may take up to 3 days.

Once acclimatized to a specific altitude, individuals can proceed with their ascent. However, if severe acute mountain sickness (AMS) occurs, they must immediately descend to lower altitudes (2,000 - 4,000 feet). While supplemental oxygen can aid in alleviating altitude sickness symptoms, it does not completely eliminate the challenges caused by decreased barometric pressure.

The Gamow bag is a portable sealed chamber with a pump that has revolutionized field treatment of high altitude illnesses.

The operation principle is the same as the hyperbaric chambers used in deep sea diving. The person is

placed inside the bag and it is inflated.

Pumping air into the bag effectively increases the concentration of oxygen molecules, simulating a descent to lower altitude. Within just 10 minutes, the bag creates an atmosphere equivalent to being 3,000-5,000 feet lower. After spending 1-2 hours in the bag, the individual's body chemistry adjusts to the lower altitude. This adaptation lasts for up to 12 hours after leaving the bag, providing sufficient time for traveling to a lower altitude and further acclimatization. The bag and pump together weigh approximately 14 pounds and are now commonly carried on major high altitude expeditions.

The gamow bag is crucial in situations where it is impossible to descend immediately.

OTHER FORMS OF ALTITUDE ILLNESS

Less common, but still serious, are two other forms of altitude illness. These typically occur among individuals who have properly acclimatized, but can happen when there is a sudden increase in elevation that the body cannot adjust to effectively. The exact reasons for this occurrence are not completely understood. However, the combination of low oxygen levels and reduced pressure often leads to fluid leakage through capillary walls into either the lungs or the brain. Going to higher altitudes without proper acclimatization can result in potentially severe and life-threatening illnesses.

High altitude pulmonary edema (HAPE) is when fluid accumulates in the lungs, disrupting oxygen exchange. As HAPE worsens, blood oxygen levels decrease, leading to cyanosis, impaired brain function, and potential fatality. Symptoms of HAPE include shortness of breath at rest, chest tightness, extreme fatigue, feeling suffocated at night, weakness, and a persistent cough with white or frothy fluid. Confusion and irrational behavior indicate insufficient brain oxygenation. One way to diagnose HAPE is

by assessing how long it takes for physical exertion recovery; extended recovery time suggests lung fluid buildup. For patients suspected of having HAPE as a life-saving measure immediate descent (2,000 - 4,000 feet) is crucial. Evacuation to a medical facility is necessary for proper follow-up treatment. Initial findings suggest that nifedipine may provide protective effects against high altitude pulmonary edema (University of Iowa, 1995).

High altitude cerebral edema, also called HACE, is a condition characterized by the swelling of brain tissue caused by fluid leakage. Symptoms of HACE include headache, ataxia (loss of coordination), weakness, and decreased levels of consciousness such as disorientation, memory loss, hallucinations, psychotic behavior, and coma. It typically occurs after spending a week or more at high altitudes and can be fatal if not promptly treated. Immediate descent of 2,000 to 4,000 feet is necessary to save a person's life. Anyone experiencing HACE should be evacuated to a medical facility for appropriate follow-up care.

In conclusion, the significance of oxygen for the functioning of the human body cannot be underestimated.

The impact of decreased oxygen pressure at higher altitudes can be substantial, and the rate at which individuals adapt to altitude exposure varies, making it challenging to anticipate who may develop altitude sickness.

There is no specific link between factors like age, sex, or physical condition and susceptibility to altitude sickness. Most people can go up to 8,000 feet without much trouble. During acclimatization, it's typical to lose fluids, so it's important to drink plenty of liquids (at least 3-4 quarts per day) to stay hydrated. Urine should be plentiful and clear.

According to research, it is important to identify symptoms of altitude sickness early and

take appropriate actions. It is better to participate in light activity during the day instead of sleeping because respiration worsens during sleep, which can make the symptoms worse. Additionally, it is crucial to avoid using tobacco, alcohol, and other depressant drugs like barbiturates, tranquilizers, and sleeping pills.

The consumption of these depressants while sleeping reduces respiratory drive, worsening symptoms. Additionally, at high altitudes, a high carbohydrate diet (with over 70% of calories from carbohydrates) can assist in the recovery process.

With proper planning and awareness, it is possible to greatly reduce the chances of altitude sickness and avoid its more severe consequences. It is important to recognize the early symptoms of altitude sickness as the human body requires sufficient oxygen for optimal functioning.

The organism's survivability is shown by its ability to adapt to different conditions, such as adjusting to lower oxygen pressure at higher altitudes.

Sources:
Electric Differential Multimedia Lab, Travel Precautions and Advice,
University of Iowa Medical College, 1995.

The book "Biological Systems" was written by Shelby D. Gerking and published by W.B. Saunders Company in 1969.

The New Grolier Multimedia Encyclopedia, 1993, is published by Grolier Electronic Publishing.

Grollman, Sigmund, The Human Body: Its Structure and Physiology, Macmillian Publishing Company, 1978.

The book "Physiology of the Human Body" was authored by Arthur C. Guyton and published in 1979 as the 5th edition by Saunders College Publishing.

The book titled "Mountain Sickness" was written by P. Hackett and published by The Mountaineers in Seattle in 1980.

The source of the text is an article titled "High Altitude Illness" written by Frank Hubble, published in the Wilderness Medicine Newsletter in March/April 1995.

Hubble, Frank, The Use of Diamox in the Prevention of Acute Mountain Sickness, Wilderness

Medicine Newsletter, March/April 1995.

The Outward Bound Wilderness First Aid Handbook was written by Isaac, J. and Goth, P. It was published by Lyons & Burford in 1991.

Johnson, T., and Rock, P., Acute Mountain Sickness, New England Journal of
Medicine, 1988:319:841-5
Langley, Telford, and Christensen, Dynamic Anatomy and Physiology,
McGraw-Hill, 1980.

Princeton University, Outdoor Action Program, 1995.

Starr, Cecie, and Taggart, Ralph. (1992). Biology: The Unity and Diversity of Life. Wadsworth Publishing Company.

Tortora, Gerard J. and Grabowski, Sandra. Principles of Anatomy and Physiology, Seventh Edition. Harper Collins College Publishers, 1993.

Wilkerson., J., Editor, Medicine for Mountaineering, Fourth Edition, The
Mountaineers, Seattle, 1992.

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