Preliminary Model of Acute Mountain Sickness Severity

Altitude illness severely limits operational effectiveness of dismounted Warriors in mountainous terrains. Commanders, therefore, need accurate estimates and predictors of Acute Mountain Sickness (AMS), the most common altitude illness, to effectively plan and manage missions to altitude. Purpose The purpose of this project was to utilize the USARIEM Mountain Medicine relational database (26 studies, 420 subjects, and 91,590 data points) of AMS with relevant subject descriptors and various altitude exposure conditions to develop a preliminary model of AMS severity scores under militaryrelevant conditions (i.e., rapid ascent, unacclimatized and non-medicated Warriors). Methods All volunteers provided descriptive background information and completed an Environmental Symptoms Questionnaire (ESQ). The ESQ assessed AMS severity using the validated AMS-Cerebral (AMS-C) factor score at various time points and elevations. A general linear mixed model was used to model the rate of change in AMS-C scores over time at various altitudes using SAS Proc Mixed (Version 9.1, Cary, NC). Significant covariates were examined in addition to time and the polynomial effects of time and included in the model as necessary. Time was centered at 18 hours. Results The preliminary AMS symptom severity model developed in our laboratory suggests that time 2 (p=0.006), altitude (p=0.0001), altitude*time (p=0.009) and altitude*time 2 (p=.0001) are important factors in predicting AMS severity scores. Output from the model suggests that the higher the elevation, the higher the AMS severity scores and that AMS peaks between 16-24 hours of exposure and resolves following 3640 hours of continuous exposure. Report Documentation Page Form Approved OMB No. 0704-0188 Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. 1. REPORT DATE OCT 2010 2. REPORT TYPE N/A 3. DATES COVERED 4. TITLE AND SUBTITLE Preliminary Model of Acute Mountain Sickness Severity 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) U.S. Army Research Institute of Environmental Medicine Thermal and Mountain Medicine Division Kansas Street, Building 42 Natick, MA 01760-5007 USA 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S) 11. SPONSOR/MONITOR’S REPORT NUMBER(S) 12. DISTRIBUTION/AVAILABILITY STATEMENT Approved for public release, distribution unlimited 13. SUPPLEMENTARY NOTES See also ADA564696. Human Modelling for Military Application (Applications militaires de la modelisation humaine). RTO-MP-HFM-202 14. ABSTRACT Altitude illness severely limits operational effectiveness of dismounted Warriors in mountainous terrains. Commanders, therefore, need accurate estimates and predictors of Acute Mountain Sickness (AMS), the most common altitude illness, to effectively plan and manage missions to altitude. 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT SAR 18. NUMBER OF PAGES 8 19a. NAME OF RESPONSIBLE PERSON a. REPORT unclassified b. ABSTRACT unclassified c. THIS PAGE unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 Preliminary Model of Acute Mountain Sickness Severity P5 2 RTO-MP-HFM-202 Conclusion Although validation of the model is necessary, this is the first model developed using military-relevant conditions which defines the rate of change in AMS severity over time at various altitudes. This preliminary model of AMS is far superior to any currently published estimates of AMS over this altitude range, and can provide quantitative guidance to Commanders in order to develop policy, training and planning tools to sustain Warrior resilience, health and performance at altitude.