A Note on Increased Blood Pressure While Staying at a High Elevation Site

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Forrest M. Mims III

Various studies have shown that increased blood pressure is experienced by people who temporarily move from a low altitude to an alpine site (Bärtsch and Gibbs, 2007).

Since 1992 I have made at least one trip each year to Hawaii to teach a short course on basic experimental science at a site near sea level and to calibrate my atmospheric instruments at the Mauna Loa Observatory (MLO), which is 3,396 m above mean sea level (msl).

Figure 1. The Mauna Loa Observatory, which is indicated by the arrow, is on the upper south slope of Hawaii's Mauna Loa, the world's largest mountain.Photograph by Forrest M. Mims III.

Because the most important calibrations must begin when the sun is very low in the sky, for most of these years I have been given permission to stay overnight at MLO to avoid having to negotiate the single lane access road during darkness. Most stays were 10 days, and the latest (June 2011) was 13 days and 12 nights. Instruments calibrated during this stay included two GLOBE sun photometers and four Microtops II sun photometers (one being an ozonometer). The original two LED sun photometers (1990 and 1991) were also calibrated, as were three shadowband radiometers (TX21, TX22 and TX31) of the UV-B Monitoring and Research Program administered by Colorado State University for the US Department of Agriculture. Every two days a five to six hour trip to sea level was made for a shower and to purchase groceries.

I have usually experienced only minor altitude symptoms at MLO, and these have mainly been due to dry nasal passages that can make sleep difficult. This problem can usually be alleviated by spraying saline solution into one's nostrils at intervals during the day and night.

Figure 2. The author is photographed at MLO. Photograph by Preston Sato.

My blood pressure is normal, and I take no blood pressure medication. During the latest trip, I measured my blood pressure at least once a day using an Omron HEM-711 arm cuff-style digital blood pressure meter. I then compared the mean of the 71 readings from 9-20 June with the mean of 240 readings made at my office in Texas (159 msl) from 7 May to 7 June 2011. Pressure and pulse rate were measured at least five times during each session. Because of the busy work schedule at both sites, the readings were not made at the same time each day. While there was usually time to relax for at least several minutes before each session, this was not always the case.

The study showed a mean increase in systolic pressure of 10.9% and a mean increase in diastolic pressure of 13.2% during the 13 days at MLO. Mean pulse rate was reduced by 1.3% during the stay. Pressure quickly returned to pre-MLO values in the days after returning to the Texas site. As with previous MLO trips, several days were required to return to a normal work schedule after returning to Texas.

Acknowledgments

I thank Dr. John Barnes, Station Chief of the Mauna Loa Observatory, for permission to stay and conduct research at MLO. The 2011 MLO calibration trip was sponsored in part by the Institute for Earth Science Research and Education and the UV-B Monitoring and Research Program of the United States Department of Agriculture headquartered at Colorado State University.

Reference

Peter Bärtsch and J. Simon R. Gibbs (2007), Effect of Altitude on the Heart and the Lungs, Circulation 116. 2191-2202. Accessed online 27 June 2011.

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