HR monitoring

Heart Rate (HR) is a measurement of a climber’s heart rate. It is instrumental in determining the acclimatization level of a climber. Acclimatization to altitude drops a climber HR. Effectively it allows a climber’s heart to pump more oxygenated blood with each beat as time goes by. When this happens, the heart does not have to beat as often to get needed oxygen to the body.

Except at extreme altitudes, i.e. > 27,000 ft a climber heart rate returns to near normal after acclimatization. Beyond 27,000 ft a climber must keep his or her time in the death zone as short as possible since among other things his or her heart rate will remain dangerously high at all times.

Failure to acclimatize causes the heart to operate near or close the maximum heart rate. The maximum heart rate (Max HR) is defined as the highest HR value attainable during an all out effort to the point of exhaustion. Climbing at Max HR is a potentially fatal condition.

HR is most commonly expressed as the number of heart beats per minute.

EKG monitoring

An electrocardiogram (ECG or EKG) consists of electrical impulses registered from the heart in graphical format. In the normal heart, electrical impulses are generated at a rate of 60–100 times per minute.

Special training is required for interpretation of a climber electrocardiogram but it is is an essential part of a vital sign monitoring device for diagnosis purposes.

An EKG records the electrical changes in the heart and shows the series of waves that relate to the electrical impulses which occur during each beat of the heart. The results are displayed on the iPAQ vital signs window.

When the presence of all waves observed in the EMACS EKG display follow the order defined alphabetically, the heart show a normal sinus rhythm; however, he heart is described as showing arrhythmia (an anormal rhythm in hearts which contract in an irregular way) when time intervals between waves, the order, or the number of waves do not fit this pattern.

RR monitoring

A climber's respiratory rate (RR) is measured as the number of breaths taken by a climber every minute. Normal resting respiratory rates for an acclimatized climber are from 16 to 20 breaths per minute.

Respiratory rate is one vital sign that needs to be followed in a number of situations; as such, EMACS' real-time respiratory rate monitoring is of great clinical interest for a climber medical diagnosis. Indeed, the importance of monitoring a climber respiration can not be overemphasized. If a climber is conscious and responding to verbal commands, a climbing party can usually assume the climber is safe. If the same climber is unconscious or asleep, a climbing party must have more concern: several studies have shown inadequate ventilation to be the most common cause of death or brain damage. .

During the first week of adaptation, a variety of changes take place. Respiratory rate and depth increase in response to lower concentrations of oxygen in the blood, causing more carbon dioxide to be lost and more oxygen to be delivered to the alveoli. The increased respiratory rate begins within the first few hours of arriving at altitudes as low as 5,000 feet. While climbing, both the partial pressure of carbon dioxide and the pH of the blood change dramatically: these changes can be attributed to the increase in oxygen consumption by the muscular system. The lungs increase their respiratory rate to compensate for these changes in an attempt to bring the body back to homeostasis

BB monitoring

Two things need to be kept in mind regarding BB (Blood Pressure) measurements:
- Higher blood pressures are normal during exertion or other stress.
- Systolic blood pressures below 80 may be a sign of serious illness or shock.

At high elevation, blood flow to the brain increases to provide the brain with its required volume of oxygen (equivalent to that available at sea level) and in the lungs, the pulmonary capillaries constrict, increasing resistance to flow through the lungs and raising pulmonary blood pressure. Dangerously high blood pressure in the pulmonary artery may cause fluid to escape from the capillaries and leak into the lungs (pulmonary edema).

ETCO2 monitoring

End-terminal CO2 is a measurement of the percentage of CO2 in an climber exhalation. A climber should never be given supplemental O2 for sustained periods without constant monitoring of ETCO2 values.

SPO2 - Pulse and Blood Oximetry

Blood Oximetry (SPO2) shows the oxygen saturation of hemoglobin in a climber's blood which is instrumental in the diagnosis of hypoxia at high elevation. A SpO2 greater than 91% usually indicates adequate oxygenation in a climber.

However, there is at least one caveat to SPO2 readings: if climbers are given supplemental oxygen, their hemoglobin saturation will approach 100%. Climbers with severe altitude induced respiratory problems, could have a normal oxygen saturation reading even though exchange rates were inadequate to cleanse the blood of CO2. This could lead to high CO2 levels and resulting low pH of the blood. Yet, in the end a climber will be damaged more by a lack of O2 than by a high CO2 level.

Three more additional things need to be keept in mind with regard to SPO2 measurements.
- SpO2 readings may not be obtained if core body temperature falls to the level of hypothermia.
- Quality signal may be unobtainable in 10% of patients with a temperature inferior to 35º C.
- Signal failure may occur at temperatures inferior to 28.5º C.