Clinical Nursing Knowledge and Applied Physiology
Core physiology to hold
Questions test whether you can link a mechanism to a sign. Revise homeostasis and fluid compartments (intracellular versus extracellular, oncotic versus hydrostatic pressure), the renin–angiotensin–aldosterone system and ADH, and acid–base balance. Understand oxygen delivery as a chain - airway, alveolar gas exchange, haemoglobin carriage, cardiac output, tissue extraction - so that a low saturation prompts you to ask why, not just to increase oxygen. Know glucose regulation and insulin action, the inflammatory and immune response, wound healing phases, renal concentrating ability, and normal age-related changes such as reduced thirst, lower glomerular filtration and stiffer arteries.
Interpreting data
Vital signs must be read as trends and patterns, not isolated numbers. A "normal" blood pressure in a young, fit patient can mask significant hypovolaemia; a rising respiratory rate and new confusion are often earlier and more sensitive deterioration markers than blood pressure. Pulse oximetry is unreliable in poor peripheral perfusion, carbon monoxide poisoning and severe anaemia.
Traps
- Confusing early (tachycardia, tachypnoea, anxiety) with late (hypotension, bradycardia) signs of shock.
- Forgetting that potassium disturbances cause arrhythmias.
- Assuming oedema always means fluid overload - hypoalbuminaemia and third-spacing also cause it.
- Misreading compensation on a blood gas as a second disorder.
Rule of thumb for blood gases
Look at pH first, then decide whether CO₂ (respiratory) or bicarbonate (metabolic) explains it. Compensation moves in the same direction as the primary change and never over-corrects the pH.
Worked example
pH 7.28, PaCO₂ 4.0 kPa (low), HCO₃ 14 mmol/L (low). Acidaemia with a low bicarbonate and hyperventilation - a metabolic acidosis with respiratory compensation.