Respiratory Physiology &
Oxygen Therapy

• Interpret SpO₂ in context and state the correct oxygen target for general vs at-risk (COPD / CO₂-retainer) patients
• Explain the oxyhaemoglobin dissociation curve and why a falling SpO₂ below 90% signals a steep drop in PaO₂
• Titrate oxygen to target — up, down, or hold — using the Oxygen Target Interpreter
• Differentiate type 1 from type 2 respiratory failure and adjust the oxygen plan accordingly
• Read a basic ABG: pH, PaCO₂, PaO₂, HCO₃ — acute vs chronic compensation
• Recognise impending respiratory failure from the work of breathing and the whole-patient picture
• Distinguish a COPD exacerbation from an asthma exacerbation and select a first-line approach

This module was developed from bedside workflow analysis across North American emergency and acute-care settings — not from a flow-rate chart taped to a wall. Oxygen is the single most administered drug in the hospital, yet it is the one most often given without a target, without a prescription, and without anyone deciding when to turn it down.

Module 09 is not against oxygen. It is against thoughtless oxygen — the reflex that reads a number, opens a flow meter, and walks away; that mistakes 100% for “safe”; that never asks what the saturation is costing the patient in work of breathing, and never asks whether this is a person who will stop breathing if you over-oxygenate them.

On most wards, oxygen is treated as harmless comfort — something you give because the patient “looks like they could use it.” But oxygen is a pharmacological agent with indications, a dose, a target, and real toxicity. Given without a target, it routinely overshoots. Hyperoxia is not benign: it causes vasoconstriction (including coronary and cerebral), absorption atelectasis, oxidative injury, and — in the CO₂ retainer — a rise in arterial CO₂ that can progress to narcosis and arrest.