Rebuttal to the Con Statement

Abstract

As Drs. Windsor and Rodway clearly point out (Windsor and Rodway 2014) obtaining an accurate measurement from a pulse oximetry is challenging in the high altitude environment. Clearly the trekker, who Drs. Windsor and Rodway use as an example, on the way to Barafu Camp (4600 m) on Kilimanjaro needs to follow directions about how to go about using the pulse oximeter (Luks and Swenson, 2011). Regardless of whatever medical reason one is using the pulse oximeter for, proper directions must to be followed. For example, using a single cut-off number from a pulse oximeter reading to predict acute mountain sickness (AMS) is clearly problematic.

So, we all agree that as with any medical instrument, the reading is only useful if it is interpreted properly. In addition, excess ambient light, hypothermia, motion artifact shivering), dyshemoglobinemias, nail polish, clubbing can all interfere with proper reading and are well known sources of error in pulse oximetry reading with digital probes (Sinex, 1999; Van Ginderdeuren et al. 2006). Indeed pulse oximetry has come into use in the mountains relatively recently, and with time we can hope people using this instrument will follow directions more stringently.

However on balance in the published, peer-reviewed literature as referenced in my main write-up, there are more studies in support of a link between hypoxemia and the development of AMS (Basnyat, 2014) than on the contrary. And many researchers appear to be convinced of the science behind this (Karinen et al. 2010).

Drs. Windsor and Rodway correctly say that genetics plays a role in the development of high altitude illness, and therefore some of us respond better to hypoxia than others. Hence two trekkers with the same low pulse oximetry reading at high altitude may have different presentation, one person is sick and the other is asymptomatic depending on their genetic predisposition. But we really do not know to what extent is this genetic contribution to the predisposition to AMS. Hence to discount the use of pulse oximeter to predict AMS on this basis would be premature. Finally to bolster their point about pulse oximetry giving confusing reading in acclimatizing individuals they reference a study (Khan et al. 2012) and elaborate on it. But the details (or even an abstract) of this study are hard to access.

As the science behind pulse oximetry continues to be refined, more robust clinical studies with reliable pulse oximeters need to be done at high altitude.

References

Basnyat

(2014). Pro: Pulse oximeter is useful in predicting acute mountain sickness. High Alt Med Biol., 15:440–441.

Karinen

, Peltonen

, et al. (2010). Prediction of acute mountain sickness by monitoring arterial oxygen saturation during ascent. High Alt Med Biol., 11: 325–332.

Khan

, Rodway

, Windsor

. (2012) Is pulse oximetry able to distinguish between acclimatized and unacclimatized visitors to altitude? —A systematic review. Oral Presentation. Oxford Hypoxia Symposium Nov 30th, 2012.

Luks

, Swenson

. (2011). Pulse oximetry at a high altitude. High Alt Med Biol., 12:109–119.

Sinex

J.E.

(1999). Pulse oximetry: Principles and limitations. Am. J. Emerg. Med., 17:59–67.

Van Ginderdeuren

, Van Cauwelaert

, and Malfroot

(2006). Influence of digital clubbing on oxygen saturation measurements by pulse-oximetry in cystic fibrosis patients. J. Cystic Fibrosis., 5:125–128.

Windsor

and Rodway

. (2014). Con: Pulse oximeter is useful in predicting acute mountain sickness-con. High Alt Med Biol., 15:442–443.