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# Living high: tissue acclimatization, highland natives and chronic mountain sickness

- Regulation
- Exam priority: medium

Weeks to years at altitude change lungs, blood and muscle; people born high adapt further, and a few make too much blood (Monge disease).

Updated Nov 13, 2026

Also called: High-altitude adaptation, Monge disease, Chronic mountain sickness

**See it in 3D:** [Kidneys](https://durgical.com/en/anatomy/kidney/)

## Key points

- Time course: ventilation rises in hours to days; EPO peaks in days; red cell mass rises over weeks to months; full adaptation takes months to years.
- Lifelong highlanders have larger chests and lungs, higher diffusing capacity and better O₂ delivery at the same PaO₂ than acclimatized lowlanders.
- Andeans tend to have higher hemoglobin and more chronic mountain sickness; Tibetans keep hemoglobin near sea-level values with higher ventilation and blood flow.
- Chronic mountain sickness (Monge disease) = excessive erythrocytosis (Hb roughly ≥ 21 g/dL in men, ≥ 19 g/dL in women) + hypoxemia ± pulmonary hypertension; descent reverses it.
- Maximal work capacity (VO₂max) falls with altitude and recovers only partly with acclimatization; natives keep more of it.
- Hemoglobin reference ranges are higher in cities such as Bogotá: lab values must be read against altitude-adjusted ranges.

## What it is

Acclimatization goes on long after the first days of hyperventilation: red cell mass rises over weeks, lung diffusing capacity and tissue O₂ handling improve, and work capacity partly recovers. People born and raised at altitude (Andean, Tibetan, Ethiopian) show further, partly genetic, adaptations. When the erythropoietic response overshoots, chronic mountain sickness appears: excessive erythrocytosis, hypoxemia and pulmonary hypertension that resolve with descent. Bogotá (about 2600 m) is moderate altitude, where these changes are mild but measurable.

## How it works, step by step

- Lower barometric pressure lowers inspired and alveolar PO₂; carotid bodies drive ventilation up, lowering PaCO₂.
- Renal bicarbonate loss over days corrects the alkalosis and lets ventilation rise further (ventilatory acclimatization).
- Hypoxia stabilizes HIF in the kidney; EPO rises and, over weeks, red cell mass and hemoglobin increase.
- 2,3-BPG rises in red cells, shifting the O₂ curve right and helping unloading in tissues.
- With time, lung capillary blood volume and alveolar surface (especially in those born high) raise diffusing capacity.
- Muscle capillary density rises (partly because fibres get smaller), shortening the diffusion distance for O₂.
- In susceptible people the hypoxic drive to breathe blunts with years; PaO₂ falls further, EPO stays high and the hematocrit climbs too high.
- High viscosity plus hypoxic pulmonary vasoconstriction raise pulmonary artery pressure and load the right ventricle.

### Oxygen–hemoglobin dissociation curve

**P50** 27.7 mmHg **Arterial blood** 97 % **Mixed venous blood** 73 % **O₂ given up to the tissues** 24 %

Right shift (P50 27.7 mmHg): Hb has less affinity and gives up more O₂ in the tissues. Acid, CO₂, heat and 2,3-BPG cause it.

- Current curve
- Normal curve (pH 7.40 · 37 °C)
- Arterial blood (PO₂ 100)
- Mixed venous blood (PO₂ 40)
- O₂ given up to the tissues

Altitude preset: higher 2,3-BPG and a lower PCO₂ pull on the curve in opposite directions; tap the presets to compare.

## Approximate values at Bogotá-like altitude (~2600 m) versus sea level, healthy adult residents (ranges; local norms vary)

| Parameter | Value | Note |
| --- | --- | --- |
| Barometric pressure | ≈ 550–570 mmHg | ≈ 760 mmHg at sea level |
| Inspired PO₂ | ≈ 105–110 mmHg | ≈ 150 mmHg at sea level |
| Arterial PO₂ | ≈ 60–75 mmHg | ≈ 80–100 mmHg at sea level |
| Arterial PCO₂ | ≈ 29–35 mmHg | ≈ 35–45 mmHg at sea level |
| SpO₂ at rest | ≈ 90–96% | ≈ 95–100% at sea level |
| Hemoglobin | roughly 0.5–1.5 g/dL above sea-level ranges | use altitude-adjusted ranges |

Approximate values for a healthy adult at rest; each laboratory sets its own ranges.

## Acclimatized lowlander versus lifelong highlanders (general tendencies)

| Feature | Acclimatized lowlander | Andean native | Tibetan native |
| --- | --- | --- | --- |
| Resting ventilation | High | Near or slightly above sea-level values (blunted hypoxic drive) | High, with a brisk hypoxic response |
| Hemoglobin | Rises over weeks | Highest | Close to sea-level values |
| Chest and lung volumes | Unchanged | Larger | Larger |
| Pulmonary artery pressure | Mildly raised | Often raised | Near normal (more nitric oxide) |
| Chronic mountain sickness | Rare | Most frequent | Uncommon |

## Clinical notes

- Chronic mountain sickness: headache, dizziness, poor sleep, cyanosis, plethora and dilated veins; scored with the Qinghai criteria; relieved by moving to low altitude.
- Long-standing high-altitude pulmonary hypertension can lead to right heart failure (cor pulmonale); COPD and sleep apnea at altitude add to the hypoxemia.
- An erythrocytosis in a highland resident is first read against local norms; very high values or a low EPO suggest another cause, such as polycythemia vera.

## Memory aid

Breathe first, build blood next, rebuild tissue last; too much blood and the high life turns heavy.

## Test yourself

Think of the answer, then tap the question to see it.

## Which change of acclimatization takes the longest to develop: hyperventilation, renal bicarbonate loss, or a rise in red cell mass?

The rise in red cell mass. Ventilation rises within hours, bicarbonate falls over days, but EPO-driven red cell production needs weeks to months to raise red cell mass.

## How do Tibetan highlanders typically differ from Andean highlanders in hemoglobin and disease risk?

Tibetans keep hemoglobin close to sea-level values and rely on higher ventilation and blood flow; Andeans have higher hemoglobin and more chronic mountain sickness.

## What three features define chronic mountain sickness?

Excessive erythrocytosis, marked hypoxemia and, often, pulmonary hypertension, in a long-term high-altitude resident; the features regress after descent.

## Why might a healthy adult from Bogotá have a hemoglobin flagged as high by a sea-level reference range?

At about 2600 m the lower inspired PO₂ raises EPO and red cell mass a little; hemoglobin must be interpreted with altitude-adjusted ranges.

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## Connections

## See it in 3D 1

The structures of Durgical's 3D anatomy where it happens.

- [Kidneys](https://durgical.com/en/anatomy/kidney/)

## Related topics 6

- [High altitude and acclimatization](https://durgical.com/en/physiology/high-altitude-and-acclimatization/)
- [Polycythemia: physiological causes](https://durgical.com/en/physiology/polycythemia-physiological-causes/)
- [Erythropoiesis and erythropoietin](https://durgical.com/en/physiology/erythropoiesis-and-erythropoietin/)
- [Exercise and training physiology](https://durgical.com/en/physiology/exercise-and-training-physiology/)
- [The pulmonary circulation and hypoxic vasoconstriction](https://durgical.com/en/physiology/the-pulmonary-circulation-and-hypoxic-vasoconstriction/)
- [Diffusion across the respiratory membrane and DLCO](https://durgical.com/en/physiology/diffusion-across-the-respiratory-membrane-and-dlco/)

## Related conditions 4

- [High-altitude illness (AMS, HACE, HAPE)](https://durgical.com/en/conditions/high-altitude-illness/)
- [Pulmonary hypertension and cor pulmonale](https://durgical.com/en/conditions/pulmonary-hypertension-and-cor-pulmonale/)
- [Polycythaemia vera](https://durgical.com/en/conditions/polycythaemia-vera/)
- [Chronic obstructive pulmonary disease (COPD)](https://durgical.com/en/conditions/chronic-obstructive-pulmonary-disease/)

## In Biochemistry 1

- [Hemoglobin and 2,3-BPG](https://durgical.com/en/biochemistry/enzymes/hemoglobin-and-2-3-bpg/)

## In Pharmacology 1

- [Acetazolamide](https://durgical.com/en/pharmacology/acetazolamide/)

[← All of physiology](https://durgical.com/en/physiology/)

Educational physiology content; not a diagnostic or treatment guide and no substitute for a health professional's advice. Values are approximate references. No doses are given.

Sources: [Chronic Mountain Sickness: Clinical Aspects, Etiology, Management, and Treatment](https://pmc.ncbi.nlm.nih.gov/articles/PMC4913504/) (High Altitude Medicine & Biology (PMC), 2016); [Human adaptation to high‐altitude: A contemporary comparison of the oxygen cascade in Andean, Tibetan and Ethiopian highlanders](https://pmc.ncbi.nlm.nih.gov/articles/PMC12949176/) (Experimental Physiology (PMC), 2026); [High-Altitude Travel and Altitude Illness](https://www.cdc.gov/yellow-book/hcp/environmental-hazards-risks/high-altitude-travel-and-altitude-illness.html) (CDC Yellow Book, 2025); [Acute mountain sickness: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000133.htm) (MedlinePlus, US National Library of Medicine, 2024).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/physiology/living-high-tissue-acclimatization-highland-natives-and-chronic-mountain-sicknes/