Q.How the body makes long-term adjustments when living in high altitude.

Over days to weeks at high altitude, the body makes long-term physiological adjustments — more red blood cells, more haemoglobin, deeper/faster breathing, and better tissue-level oxygen delivery/use — that together improve its ability to survive the low partial pressure of oxygen at altitude.

At high altitude, the same percentage of oxygen is present in the air, but its partial pressure is lower because overall atmospheric pressure is lower, so less oxygen diffuses into the blood at the lungs with each breath. Over time (days to weeks) the body makes several long-term adjustments to cope:

1. Increased red blood cell (RBC) production — the low oxygen level is sensed by the kidney, which secretes more of the hormone erythropoietin; this stimulates the bone marrow to produce more red blood cells (polycythemia), increasing the blood's total oxygen-carrying capacity.

2. Increased haemoglobin content — along with more RBCs, total haemoglobin in the blood rises, allowing more oxygen to be bound and transported per unit volume of blood.

3. Increased pulmonary ventilation — breathing rate and depth (and over time, lung/vital capacity) increase, so more air (and hence more total oxygen) is moved in and out of the lungs per minute, partly compensating for the lower oxygen pressure in each breath.

4. Increased capillary density in tissues — more capillaries develop in body tissues, shortening the diffusion distance from blood to cells and improving oxygen delivery.

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Nitrogen narcosis is an anaesthetic-like state caused by excess dissolved nitrogen acting on the nervous system when a diver breathes compressed air at great depth.

Air is normally about 78% nitrogen, a gas that is physiologically inert at normal atmospheric pressure and is simply breathed in and out without producing any noticeable effect. However, when a diver descends to significant depths underwater while breathing compressed air from a cylinder, the surrounding water pressure (and hence the pressure of the air being breathed) increases greatly with depth. At these elevated pressures, much larger amounts of nitrogen than normal dissolve into the diver's blood and, from there, into fatty/nervous tissues, including the brain. This excess dissolved nitrogen begins to exert a narcotic (anaesthetic) effect on the nervous system, producing symptoms similar to alcohol intoxication — such as euphoria, overconfidence, impaired judgement, slowed reaction time, drowsiness, and reduced coordination. This condition is called nitrogen narcosis (informally 'rapture of the deep' or the 'martini effect'), and it typically starts to become noticeable at depths beyond roughly 30 metres, worsening as depth …