Pulse Oximeter on Mount Kilimanjaro
A pulse oximeter is a tiny clip which fits over a finger, shining light into the tissue to measure the color of reflected light and estimate the amount of oxygen in the blood. It can subtly aid the diagnosis of altitude sickness on a Kilimanjaro climbing challenge. Oxygen is carried by red blood cells, the color determined by the percentage of oxygen they contain. Bright scarlet blood is oxygen rich as it leaves the lungs and becomes a dark, burgundy color when the oxygen is used up and replaced by carbon dioxide, which is exchanged for more oxygen when it goes back to the lungs. Altitude sickness occurs when less oxygen is obtained from the lungs and arterial blood is darker in hue. Acclimatization increases the number of red blood cells available, enabling more oxygen to be carried. The redness of the blood tells you the level of oxygen saturation, from which you can judge the amount available to the trekker. However, these readings are very difficult to assess and vary from one individual to another especially at a high altitude environment.
A high reading of SpO2 could indicate very good acclimatization, or that the person is hyperventilating from anxiety, or even that he has carbon monoxide poisoning! A lower reading could demonstrate anoxia, oxygen starvation, or it could show that a person is coping very well with altitude. A trained athlete with 65% oxygen saturation may be perfectly safe, whilst a less fit trekker could still be at risk for hypoxemia at 75%. The real purpose of a pulse oximeter is to correlate heartbeat and oxygen saturation in a clinical environment for someone suffering from sleep apnea, heart attack or failure, pneumonia, anaemia and asthma. On a climbing excursion on Kilimanjaro mountain, it makes more sense to rely on your AMS symptoms and your guide to decide if you can safely continue your climb, or if you should return to a lower elevation. We advise trekkers to take an extra day acclimatizing on Kilimanjaro to make summit success more likely and allow you to avoid the worst effects of Altitude Sickness.