Acclimatization To The Altitude And Mountain Pathologies – Part 1

For those who are planning an expedition of the high mountain, it is essential to understand the behavior of the human body at high altitude and learn to identify the signs of diseases arising from exposure to hypoxia States or low pressure of oxygen, so that a correct acclimatization strategy is adopted.
This is an area little known by medicine, if compared to the advances of several other medical fields.
In addition to the lack of interest of major laboratories and companies to finance research projects on this subject, there is also an enormous operational difficulties to carry out investigations because of the conditions of the high mountain environment.
The studies have little statistical basis, preventing scientific conclusions. Many myths are propagated, also contributing to the misinformation on the subject. Is to try to bring some light to this theme, undoing such myths, that we will lead this series of articles.
Let’s start by describing what would be the popularly known “mal de altitude”. The Evil acute Mountain (MAM) or Acute mountain Sickness (MPEs) is more than a disease syndrome. A disease represents physiological or psychological disorders with causative agents Associates, like in the cold, which has a viral origin. A syndrome is a group of symptoms (senses by the patient) and signs (visible by third parties).
Thus, MAM there is a large set of symptoms and signs, which can vary widely from person to person, in an exposure to low oxygen pressure as a result of staying at high altitudes. It was described by the Consensus of Lake Louis as the presence of headache in a person not acclimatized at an altitude above 2500 m, along with one or more of the following symptoms:
 Gastrointestinal: lack of appetite, nausea, vomiting
 Insomnia
 Fatigue
 Nausea/dizziness
 Fatigue
The MAM ranks in mild, moderate and severe and, due to the wide variety of symptoms, a score of punctuation, known as Score of Lake Louis, for determining the severity of MAM.
In the Score of Lake Louis is assigned a score to the symptoms the patient senses:
 1 point : slight headache, nausea, anorexia (lack of appetite), insomnia, Vertigo
 2 points : headache resistant to aspirin or paracetamol, vomiting
 3 points : accelerated respiration at rest, fatigue, abnormal or decreased urine output (volume of urine)
Adding to the points, the severity of the MAM:
 1 to 3 points : take MAM
 4 to 6 points : MAM moderated
 More than 6 points : MAM serious
 These are the main symptoms observed in the syndrome known as MAM. One of the myths about the evil mountain says that people with a good physical conditioning or aerobic run higher risk at high altitude because your body “mask” the symptoms of MAM, besides having a greater propensity to pulmonary edema because they have a stronger heart. However, there is no relationship between the physical capacity or a person’s aerobic and non-observance of the symptoms that define the MAM.
 Maybe the statement that the body of people with a good fitness “mask” the symptoms of altitude sickness is caused by the mistake of taking the parameters brought by the use of pulse oximetry as signs of the presence or absence of MAM: level of oxygen saturation and heart rate per minute. These parameters cannot, and should not be used in this sense, as will become clear later. Only the symptoms set in the consensus of Lake Louis is determining the presence or absence of MAM and not the parameters of the Oximeter.
 The misunderstanding worsens because people with good physical conditioning, usually hiperventilam well, causing the heart rate per minute are relatively low and achieving a good level of oxygen saturation.
 But may be deliberately hiding the symptoms mild or moderate real MAM (perhaps out of fear or pride, just for being well prepared), which are not always visible by others, leaving only the obvious thing when they come to a MAM of moderate to severe.
 In short, you can’t reach the conclusion on the presence or not of MAM using a Pulse Oximeter for measurement of oxygen saturation level in the blood and the heart rate, and follow the Score of Lake Louis.
 High levels of oxygen saturation does not imply necessarily on good acclimatization, means they’re not masking the symptoms of MAM, because a person with MAM, inevitably, will have headache, vomiting, insomnia, etc., but may be hiding the fact that the guide or his companions for personal reasons. The understanding of the physiological mechanisms of acclimatization to the altitude will make this clear, as we will see next.
As we gain altitude there is a decrease in atmospheric pressure, with a consequent decrease in partial pressure of oxygen.
At any altitude, the composition of the gases of the atmosphere is invariant: 21% oxygen and 78% nitrogen more, being the small percentage remaining represented by other gases of low expressiveness.
The partial pressure of oxygen is thus 21% atmospheric pressure and corresponds to the only strength that takes oxygen from the air to the cells of the organism. The decrease of pressure with altitude is an obstacle to the cellular oxygenation.
The low concentration of oxygen in the blood produces a lack of oxygen in the cells of the body, a situation known as cellular hypoxia or anoxia, which is the sign that triggers the mechanisms of adaptation to the altitude (in fact, mechanisms of adaptation to hypoxic conditions), seeking to maintain an oxygen consumption tailored to the needs of the body, despite low levels of partial saturation of oxygen content of red blood cells responsible for driving the oxygen in the blood.
The adaptation mechanisms occur in 3 levels:
 Respiratory: hyperventilation, with increased volume of air breathed and respiratory rate.
 Phone: better release of oxygen in the blood, hemoglobin, carrier contained in red blood cells and is responsible for driving the oxygen.
 Blood type: Polycythemia, with the increase in the number of carriers (red blood cells).
The Polycythemia is often erroneously cited as the main mechanism of adaptation to altitude, but, as we shall see below, their effects will only become effective from the 15th day of exposure to hypoxic conditions, not being so relevant in mountains like Aconcagua, whose expeditions last, on average, 2 weeks.
Hyperventilation is the first compensatory mechanism when it comes to altitude, being immediate and proportional to the level of cellular hypoxia. From 3,500 m hyperventilation also manifests itself in home.
Consists of an increase in breathing through broader and more rapid movements. At the beginning if the amplitude of the respiratory movements increments, and the respiratory rhythm in individuals without disease, only increases significantly from the 6,000 m.
The increase in respiratory rate can decrease, considerably, the respiratory volume, which is not desirable, since for a effective hyperventilation should provide a sufficient amount of air to the extreme, bronchial pulmonary alveolus.
People with a good aerobic capacity, or with high rates of VO2 max, have a greater ability to hyperventilation and, so, feature more aptitude for proper fit in the initial periods of exposure to altitude.That doesn’t mean we necessarily have a better acclimatization to altitude, because this process depends on many factors that are not always well known or explained scientifically.
But also there is no relationship between being well prepared physically and have a greater tendency to have problems at high altitude because the body mask the symptoms of altitude, as we point out above. This is a myth has no scientific basis, because a person well prepared physically, if you start having problems at high altitude, will present the same symptoms as any other “poor mortal”: headaches, nausea, vomiting, etc., that is, the signs and symptoms described by Consensus of Lake Louis that define the MAM.
People with good aerobic capacity, for a more effective, hyperventilation usually feature a lower rate of heartbeats per minute that people least prepared physically, but a higher level of oxygen saturation. The problem is that the symptoms of the MAM (Evil acute Mountain) are not always visible signs by third parties and people, out of fear or out of pride, often lie about the presence of such symptoms.
That is, it is not the body of a person well prepared physically which is masking the symptoms of MAM, but the very person that masks, conscious and voluntarily, the existence of such symptoms. In addition, present good indices of heartbeats per minute and oxygen saturation doesn’t mean a good acclimatization and such indexes could not be used alone to determine the conditions of acclimatization.
Hyperventilation presents some disadvantages, such as greater energy expenditure and loss of heat and water by the body, since the air is cold mountain-inspired dry and must be heated and humidified.Hyperventilation is also one of the main causes of cough in altitude, because the cold and dry air tends to irritate the Airways.
The main problem of hyperventilation, however, is that causes a disorder in regulating breathing due to the marked decrease in CO2 levels in the body. In the alveoli, the sum of the pressures of oxygen and carbon dioxide is constant. Thus, a forced expiration, eliminating a greater amount of CO2, allows to penetrate a greater quantity of oxygen. However, oxygen and CO2 Act as stimulants of respiratory regulation in normal conditions.
The lack of oxygen (hypoxia) and the increase of CO2 (hypercapnia) are stimuli for breathing. Already the decrease of CO2 (hypocapnia) inhibits breathing. Hyperventilation produces an excessive CO2 elimination, leading to hypocapnia situation that conflicts with the stimulation of oxygen, inhibiting the respiratory control centers. CO2 is an acid molecule and hypocapnia also produces a source respiratory alkalosis.
Such respiratory conflict at the beginning of the period of altitude exposure can lead to difficulty of acclimatization. That’s why I have good aerobic capacity, and consequently a good hyperventilation, does not imply good acclimatization (which means “mask” the symptoms of MAM, we insist). A good acclimatization, usually is accompanied by chemical adaptations the organism, as the correction of respiratory alkalosis by bicarbonate disposal by the kidneys.
People with difficulty of acclimation, often resort to the use of acetazolamide, best known for your trade name, Diamox.
The acetazolamide is a medication of the family of the “neonatal oxygen” and one of the few that offers significant results and scientifically proven to minimize problems in altitude or facilitate the process of acclimatization.
However, the explanation usually presented for the effects of acetazolamide in the body de-emphasizes the properties that make it really effective. It is common to read or listen to arguments like Diamox, being a diuretic, helps eliminate the fluids of the body which could accumulate in the lungs or the brain, leading to edema. This argument is almost another myth about acclimation.
Despite the acetazolamide be, in fact, a diuretic drug, its effects diuretics in the body are not as relevant in the process of acclimatization to the altitude.
The efficacy of acetazolamide is in your ability to fix respiratory alkalosis was produced by hyperventilation, in the early stages of exposure to altitude, facilitating the process of acclimatization to improve the level of oxygenation of the body.
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