Improvement in Altitude Performance Test After Further Acclimatization in Pre-Acclimatized Soldiers

Abstract

The Altitude Performance Test is a measure designed to assess an individual's degree of acclimatization to reduce the risk of acute mountain sickness during high-altitude activities. The aim of this study was to investigate the hypothesis that test results will improve in pre-acclimatized soldiers after several days of further acclimatization. The Altitude Performance Test consists of an uphill run at high altitude. The event is timed and performed with continuous oxygen saturation (SpO2) monitoring. The individual's time and lowest SpO2 measurement are recorded. This test was performed on the first day of arriving at 11,060 ft, and after 9 days at the same location. The 37 male soldiers were all pre-acclimatized before arrival. The sleeping altitude remained constant at 11,060 ft, and the daytime altitudes increased up to a maximum of 15,775 ft. Test results improved significantly after a further 9 days of acclimatization (time, -11 s; SpO2, +5%-points; p ≤ 0.001). This is remarkable because all soldiers were pre-acclimatized and showed only minor acute mountain sickness symptoms during the entire stay. This indicates that the acclimatization process is not finished after amelioration of altitude symptoms. The demonstrated improvement in physical performance could prove very important, particularly during military missions performed at high altitude.

The Use of Pulse Oximetry at High Altitude

“…In conclusion, the measurement of SpO 2 during physical exercise is more sensitive concerning the individual degree of acclimatization than the measurement at rest [38]. We could also show that the test result improves with increasing acclimatization (faster running time, higher SpO 2 ) [39].…”

“…A deficient standardization of SpO 2 measurement at altitude and fundamental differences in the study design are most likely the major reasons for the heterogeneous study situation regarding the predictability of AMS by pulse oximetry [7,12,[33][34][35][36][37]. With the experience of numerous SpO 2 measurements up to an altitude of 7,100 m [3,12,24,38,39] we regard a strictly standardized, always identical determination of SpO 2 at rest as the mandatory requirement for its use in the context of altitude medicine [12][13][14]. In addition to the defined time of measurement [24,25] usually in the morning when the patient is fasting, averaging over a longer measurement period (several minutes) is necessary [5,10,12].…”

“…The assessment of an individual's degree of acclimatization to altitude is difficult. We have therefore developed a test procedure to assess the individual degree of acclimatization [38,39]. The competitive character of the performance test ensured a high degree of motivation for all subjects and this led to a well-standardized test environment.…”

Using modified Fenn diagrams to assess ventilatory acclimatization during ascent to high altitude: Effect of acetazolamide

“…Despite smaller differences in $${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$$, $${S_{{\mathrm{p}}{{\mathrm{O}}_{\mathrm{2}}}}}$$ variability caused significant differences in AUC between the three groups. Other studies also noted decreased $${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$$ and improved $${S_{{\mathrm{p}}{{\mathrm{O}}_{\mathrm{2}}}}}$$ in more acclimatized participants due to greater VA and increased ventilation (Katayama et al., 2005; Kong et al., 2015; Tannheimer et al., 2013), confirming that our results are physiologically congruent, and that highly acclimatized participants have smaller AUCs on modified Fenn diagrams (Rahn & Otis, 1949).…”

Challenges of Military Health Service Support in Mountain Warfare

“…14 Several tests exist that support estimation of the individual risk of AMS and/or the degree of acclimatization. 14,[37][38][39] However, it must be pointed out that all these tests have so far shown a limited positive predictive value and should therefore be used conservatively. To date, the most valid data with regard to future altitude tolerance is the individual's altitude history.…”