Cardiorespiratory Practice
Cardiorespiratory questions blend physiology with safety. You should be able to interpret arterial blood gases (pH, PaCO2, PaO2, bicarbonate, base excess) and identify respiratory versus metabolic acidosis or alkalosis with compensation; read a chest radiograph at a basic level; recognise abnormal breath sounds; and select oxygen delivery devices by the fraction of inspired oxygen they reliably provide. Positioning is a treatment: upright and forward-lean positions improve ventilation-perfusion matching and reduce dyspnoea, while a unilateral lung problem is often managed with good-lung-down positioning for perfusion, subject to tolerance and monitoring.
Concepts to own
- Airway clearance: active cycle of breathing, autogenic drainage, PEP and oscillating PEP, percussion and vibration, and when each is indicated or contraindicated (for example, untreated pneumothorax, frank haemoptysis, unstable cardiovascular status).
- Exercise prescription: METs, Borg and RPE scales, Karvonen target heart rate, and the difference between symptom-limited and heart-rate-limited training.
- Pulmonary rehabilitation principles and the expected benefits in obstructive versus restrictive disease.
- Post-operative precautions after cardiac surgery, including sternal precautions and safe mobilisation.
- Monitoring: pulse oximetry limitations in poor perfusion, anaemia or motion; when to hold or stop a session.
Traps
Calculation errors in target heart rate are common: Karvonen is ((maximal HR − resting HR) × intensity) + resting HR, with maximal HR estimated as 220 − age. A second trap is treating a single desaturation value as meaningful without considering trend, technique and symptoms. Third, questions often describe a patient whose breathlessness is cardiac or metabolic rather than pulmonary.
Rule of thumb
Before every mobilisation, ask three questions: is the patient stable enough to move, what is the objective stopping criterion, and what will I do if it is met? State the criterion (for example, a fall in oxygen saturation, a rise in heart rate beyond an agreed limit, new chest pain or arrhythmia) before you start, not after.