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[Pharmacology](https://durgical.com/en/pharmacology/) · Class

# Medical gases

Gases given as medicines: oxygen corrects hypoxaemia and nitrous oxide gives analgesia and supports anaesthesia.

Updated 2026-11-01

## What they are

Pharmaceutical-grade gases supplied in cylinders, hospital pipelines or concentrators: oxygen, nitrous oxide, medical air and, for special uses, inhaled nitric oxide and heliox. Oxygen is an essential medicine: it is prescribed, adjusted to a saturation target and has adverse effects.

## Mechanism of action

Inspired oxygen raises the alveolar and arterial oxygen partial pressure and haemoglobin saturation; haemoglobin carries it to the tissues, where cytochrome c oxidase uses it to make energy. Under pressure (hyperbaric chamber) much more oxygen also dissolves in plasma and carbon monoxide is cleared faster.

Target: Haemoglobin (transport) and cytochrome c oxidase (cellular use)

## Key points

- Oxygen is titrated to a saturation target: both hypoxaemia and too much oxygen cause harm.
- Concentrated oxygen can collapse poorly ventilated alveoli (absorption atelectasis); dry and prolonged, it irritates the mucosa, so it is humidified.
- In preterm infants, too much oxygen is linked to retinopathy of prematurity.
- An oxygen-rich atmosphere is a fire hazard: no flames or cigarettes near the equipment.
- When nitrous oxide is stopped, 100% oxygen is given to prevent diffusion hypoxia.

## Drugs in this class

- [**Oxygen** Essential medical gas that corrects hypoxaemia. It is adjusted to a saturation target: too much harms the lung and the… Haemoglobin (transport) and cytochrome c oxidase (use in mitochondria)](https://durgical.com/en/pharmacology/oxygen/)

## Others in the class

- Medical air
- Inhaled nitric oxide
- Heliox

## Test yourself

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

## Why is oxygen considered a medicine?

Because it has indications, a dose adjusted to a saturation target, adverse effects (lung toxicity, retinopathy of prematurity, atelectasis) and needs a prescription.

## What physical risk makes smoking near a patient on oxygen forbidden?

Oxygen supports combustion: a spark or flame can start a fire and cause severe burns.

## Which poisoning is treated with 100% or hyperbaric oxygen?

Carbon monoxide poisoning, because oxygen speeds the release of CO from haemoglobin.

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 24 (McGraw Hill, 2023); [Oxygen Therapy | Hyperbaric Oxygen Therapy | MedlinePlus](https://medlineplus.gov/oxygentherapy.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [eEML - Electronic Essential Medicines List](https://list.essentialmeds.org/) (World Health Organization, 2025).

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