This seemed like a timely entry here at Cirugia de Torax, as I return from Bogotá, Colombia (the third highest capital city in the world.) However, while the concept of surgical constraints due to elevation is not new; but today we will discuss definitions and explore the published literature. I’d also like to apologize to my readers – much of the available medical literature in not available as a free text, so while I am able to access and reference this information – I can not post links to the full articles themselves.
First, we need to define some terms when we talk about altitude, since most of the research is actually looking at very high (versus moderate altitude). This is important because as you will see, very few people are living at, and even fewer people are having surgery at these heights.
Definitions of Altitude: from Muzo, Tulco & Cymerman (2004).
Very-High Altitude: 4250 – 6000 meters elevation (13,943 ft to 19,685 ft): There are few permanent cities at this altitude. At the upper range of very high altitude cities, you are essentially talking about ‘base camp’ settlements of Mount Everest and places like Wenzhuan (Tibet) which is listed as the world’s highest city at an elevation of 16,467. (There is some controversy over this status, as La Riconada, Peru at 16,728 ft. (5100 meters) also claimed status as the highest city. There are no cities with any significant size (greater than just a few thousand residents) at this elevation. However, the majority of altitude research has been conducted at the very high and high altitude elevations.
High-Altitude: 2500 meters – 4249 meters
(8,202 ft to 13,940 ft): this classification includes several larger cities / population centers including three capital cities:
La Paz, Bolivia (est. elevation ranging from 3200 meters to 3,650 meters in different portions of the city) population of metro area: 2.3 million.
Quito, Ecuador (est. elevation 2800 meters or 9186 feet) population: 1.4 million
Bogotá, Colombia (2660 meters, 8727 feet) population: 10 million
According to the majority of scientific and medical literature, physiological adaptation, high altitude effects and illnesses usually do not occur until people reach an altitude of 2500 meters or greater. (However, the authors acknowledge that in certain individuals – these effects can occur at relatively low elevations (1,000 meters).
Moderate Altitude: 1000 meters to 2500 meters (3900 feet to around 8000 ft) This is actually the level that most of the people who are concerned about the effects of elevation live and operate at. This includes Denver, Colorado; Lake Tahoe, California/Nevada; Flagstaff, Arizona and several other American cities in the Sierra Nevada Mountain Range. It also includes several Alpine cities (while the alps themselves are around 4400 – 4800 meters, most of the cities are in the valleys, and most lay at around 1500 meters.)
Low Altitude: below 1000 meters.
References:
Heart. 2006 Jul;92(7):921-5. Epub 2005 Dec 9. Safety and exercise
tolerance of acute high altitude exposure (3454 m) among patients with coronary artery disease. Schmid JP, Noveanu M, Gaillet R, Hellige G, Wahl A, Saner H. (Switzerland)
Chest. 1995 Nov;108(5):1292-6. The safety of air transportation of
patients with advanced lung disease. Experience with 21 patients requiring lung transplantation or pulmonary thromboendarterectomy. Kramer MR, Jakobson DJ, Springer C, Donchin Y. (Israel).
Br J Sports Med. 1995 Jun;29(2):110-2. Poor ventilatory response to mild hypoxia may inhibit acclimatization at moderate altitude in elderly patients after carotid surgery. Roeggla G, Roeggla M, Wagner A, Laggner AN. (Austria).
Thorax. 1995 Jan;50(1):22-7. Doppler assessment of hypoxic pulmonary vasoconstriction and susceptibility to high
altitude pulmonary oedema. Vachiéry JL, McDonagh T, Moraine JJ, Berré J, Naeije R, Dargie H, Peacock AJ. (Belgium)
Ann Surg. 1897 Sep;26(3):297-306. II. A Preliminary Comparison
of Methods and Results in Operative Surgery at the Sea Level (New York) and in Places of High Altitude (Denver). Powers CA. (Note the date of publication – 1897 – we’ve been looking at this issue for quite a long time.)
West J Med. 1995 Aug;163(2):117-21. Sea-level physical activity and acute mountain sickness at moderate altitude. Honigman B, Read M, Lezotte D, Roach RC. – This is an interesting study which looks (observational by survey only) at the physiological responses of conference participants from low elevations upon reaching higher elevations (3000 meters in this study / 9,840 ft). The study compared the incidence of altitude sickness/ symptoms among people who defined themselves as physically fit/ physically active (using standardized criteria) versus more sedentary individuals. In total, 28% of the 200+ participants reported three or more symptoms of acute mountain sickness, but surprisingly, there was no difference in incidence among the physically fit (at sea-level) group and the more sedentary group which belies much of the current folklore related to altitude sickness.
Muza, Tulco & Cymerman (2004). Altitude Acclimatization Guide.
Essenbag, V., Halabi, A. R., Churchill-Smith, M & Lutchmedial, S. (2003). Air transport in Cardiac Patients. Chest 2003 Nov; 124(5): 1937-45. McGill University, Montreal, Canada.
Altitudes of World Cities – there are some discrepancies with altitudes listed here and other reference materials.
In our next post we will talk more about this research, what it means, and what research is still needed to examine the effects of high altitude surgery, particularly in thoracic patients.
Thoracic Surgery 