Good evening all,
As we remain caught-up on our lecture schedule, we do not need to meet in person on Friday (04 Oct) for lecture. Instead, I'd like to you to consider a recent science news article that bears on our lecture material.
In recent weeks, we have considered the properties of our blood, its red blood cells and hemoglobin, as well as the ways in which the circulatory and respiratory systems interact to deliver oxygen to our tissues. We've also described how erythropoietin (EPO, a hormone released from the kidneys in response to low blood oxygen levels) can stimulate the production of more RBCs.
The article I am sending you considers these same phenomena in a human population that lives (but not thrives) in perhaps the highest-elevation city in the world, La Rinconada, Peru. La Rinconada sits at an elevation of 5,100 m (more than 16,500 ft) above sea level, and has a regular population of >50,000 at this very high altitude, there to work in gold mines.
The air at this elevation contains only half as much oxygen as the air at sea level. Persons not accustomed to living at high altitude can become very ill (sometimes fatally) at elevations above 9,000 ft. To give you an idea of how high in the Andes this city is, consider that 'mountain climbing' here is the US is typically considered to be very technical above 12,000 ft in elevation, and not for amateurs. At La Rinconada, people may spend their entire lives above 16,000 ft in elevation.
The physiological challenges of life at this altitude are many and severe. The low oxygen levels stimulate extremely high levels of RBCs and hemoglobin, as much as 3x those considered to be normal. This, in turn, causes blood viscosity to rise dramatically, which causes abnormally high blood pressures. These elevated blood pressures place extra strain on the heart, causing it to enlarge, often dramatically. Despite these adjustments, many suffer from chronic hypoxia, termed 'chronic mountain sickness', or CMS. Blue-ish skin, fatigue, and low endurance all are common symptoms of CMS, and all stem from low levels of blood oxygen.
Curiously, populations long adapted to life at high altitudes (including some populations in these South American Andes mountains, and others in the Himalayas of Southern Asia) seem to have evolved at least some protections against chronic hypoxia and the challenges it poses. This suggests that there may be genetic tools that can be put to use in helping others who suffer from hypoxia not because of altitude, but because of diseases related to cardiac or respiratory function.
This article describes one team of physiologists and their efforts to assess human physiology and health at this altitude. Their initial focus was on CMS and body responses to it, but they quickly became caught-up in the socio-economic plight of the people there - life is brutal for the residents of this city, and the researchers felt, in many ways, helpless to help them. They certainly could not improve the economic status of the town's residents, nor could they offer a cure for CMS. There, as in many parts of the world (including our own country), the working class are too easily exploited, too easily marginalized. Lack of access to basic health care is often one of the first signs of a population that is short of options and resources. When that combines with dangerous forms of employment for the un- or under-educated, health issues rise and life expectancy falls.
There is a companion podcast for this article as well:
As you review these materials, I'd like you to think about the basic physiological mechanisms at play: how low blood oxygen levels can stimulate RBC responses, and, in turn, how these can contribute to blood pressure, which itself can trigger responses (remember ANF, when blood pressure rises?). Keeping ourselves in homeostatic conditions is complex even under typical environmental conditions; life under extreme conditions only amplifies the challenge.
I hope that you enjoy this article, and I hope that you enjoy the Homecoming weekend. Please be safe, and I will see you on Monday.