Describe Oxygen Therapy & Delivery Devices in detail.

Oxygen Therapy

Oxygen therapy is the administration of oxygen at a concentration greater than that of air to treat or prevent hypoxaemia. It is a drug — given for an indication, at a dose (concentration/flow), and with awareness of hazards. The device is chosen for the concentration required and whether it must be fixed or variable.

Variable VS Fixed Performance

Variable-performance devices (nasal cannulae, simple mask) deliver an oxygen concentration that depends on the patient’s breathing (their inspiratory flow dilutes the oxygen with air), so the exact FiO₂ is unknown. Fixed-performance devices — the Venturi mask — entrain a constant proportion of air to deliver a precise, known concentration regardless of breathing, important when a controlled dose is needed (e.g. COPD).

Hazards

Oxygen has hazards: oxygen toxicity (prolonged high concentrations cause pulmonary damage and, in neonates, retinopathy); absorption atelectasis; CO₂ retention in some patients with chronic type-2 respiratory failure (give controlled oxygen via a Venturi mask, titrated to a target saturation); and it supports combustion (fire risk).

Choosing a Device

Match the device to the need: nasal cannulae for comfort and low requirements, a non-rebreathing reservoir mask for a critically ill/hypoxic patient needing high concentration, and a Venturi mask for a precise, controlled concentration. Always titrate to a target oxygen saturation.

Physiology & Prescribing Oxygen

Oxygen therapy corrects hypoxaemia by raising the alveolar and hence arterial oxygen tension, improving the saturation of haemoglobin and the delivery of oxygen to the tissues, and it is one of the commonest treatments given in acute care. The modern principle is that it should be prescribed and titrated to a target saturation like any other drug rather than given routinely at a fixed high flow, because both too little and too much oxygen can be harmful — hypoxaemia damages the tissues, while unnecessary hyperoxia carries its own risks and, in the carbon-dioxide-retaining patient, can be dangerous. Choosing the device and flow to achieve the target saturation, and reviewing the response, is therefore central to safe oxygen therapy.

Humidification & High-flow Oxygen

Oxygen drawn from a cylinder or wall supply is dry and cold, and prolonged administration of dry oxygen can dry the airway secretions and mucosa, so humidification is added for longer-term or high-flow therapy. A notable modern development is high-flow nasal oxygen, which delivers warmed, humidified oxygen at very high flow rates through wide-bore nasal cannulae, allowing a high and relatively predictable inspired concentration, some positive airway pressure and improved comfort; it has found a role in acute hypoxaemic respiratory failure and in supporting oxygenation around the time of intubation. These developments reflect the same principle of matching the device to the concentration, flow and duration of oxygen the patient needs.

Fixed-performance devices deliver a known FiO₂ regardless of breathing pattern.

• Oxygen is a drug: give for an indication, at a dose, titrated to a target saturation, aware of hazards.
• Variable-performance (nasal cannulae, simple mask): FiO₂ depends on the patient’s breathing (unknown).
• Fixed-performance (Venturi): precise, known concentration — for controlled therapy (COPD).
• Non-rebreathing reservoir mask: high concentration for the critically ill/hypoxic.
• Hazards: oxygen toxicity, absorption atelectasis, CO₂ retention (type-2 failure), fire.