A selected, view-only collection of Primary FRCA educational discussions. Register to join the full Oxford FRCA community.
Pinned
Dr Henry Jefferson, Consultant Anaesthetist
👋 Welcome to Discuss Ask questions, discuss concepts, suggest features or point out anything that doesn’t look right. I’ll do my best to reply personally. Character limit has been increased from 250 to 750 to allow more detailed discussion! New - want it in bold? Put a star on either side of a word or sentence. Henry
Read discussionDr Henry Jefferson, Consultant Anaesthetist
#QuestionFeedback 15. Physiological Shunt A useful correction was highlighted regarding normal physiological shunting. It is VENOUS blood from the bronchial circulation that drains into the pulmonary veins, rather than the bronchial arteries themselves. This represents a normal anatomical right-to-left shunt, contributing to physiological venous admixture. Thebesian venous drainage into the left heart is another example.
Read discussionDr Henry Jefferson, Consultant Anaesthetist
#QuestionFeedback 14. Apical V/Q Is the V/Q ratio infinite at the apex of the lung? Not normally. Although apical perfusion is relatively low, it is not absent in a healthy upright adult. An infinite V/Q ratio requires ventilation with ZERO perfusion, representing alveolar dead space. Conversely, V/Q = 0 represents perfusion without ventilation (shunt). The normal lung apex has a HIGH V/Q ratio, but not an infinite one.
Read discussionDr Henry Jefferson, Consultant Anaesthetist
#QuestionFeedback 13. V/Q ratio - Apex vs Base A question was raised about why the V/Q ratio is higher at the lung apex despite both ventilation and perfusion increasing towards the base. The key is that perfusion increases proportionately MORE than ventilation. Consequently, the V/Q ratio falls from apex to base. This also explains why alveolar PO₂ is higher and PCO₂ lower at the apex. Regional alveolar gas composition depends on the V/Q ratio, rather than absolute ventilation alone.
Read discussionDr Henry Jefferson, Consultant Anaesthetist
#QuestionFeedback 12. Fetal Ductus Arteriosus What keeps the ductus arteriosus patent during fetal life? Two important factors are: • LOW fetal oxygen tension • HIGH prostaglandin E₂ activity Following birth, increasing oxygen tension and decreasing prostaglandin concentrations promote ductal constriction. Feedback highlighted that the original answer simply stated 'prostaglandin E₂' without specifying a HIGH concentration.
Read discussionDr Henry Jefferson, Consultant Anaesthetist
#QuestionFeedback 11. Haldane Effect Feedback highlighted an ambiguity in how the Haldane effect was described. Deoxygenated haemoglobin carries more CO₂ through two distinct mechanisms: 1. Increased H⁺ buffering, facilitating bicarbonate formation. 2. Increased direct binding of CO₂ to haemoglobin, forming carbamino compounds. Binding H⁺ does NOT itself form carbamino compounds.
Read discussionDr Henry Jefferson, Consultant Anaesthetist
#QuestionFeedback 10. Lung Capacities A useful terminology clarification. Although FRC describes a volume of gas within the lungs, it is formally classified as a lung CAPACITY because it consists of two volumes: FRC = ERV + RV Closing capacity (CC) is similarly composed of closing volume + residual volume. When CC approaches or exceeds FRC, small airway closure can occur during normal tidal breathing. This becomes particularly relevant under general anaesthesia, when FRC commonly decreases.
Read discussionDr Henry Jefferson, Consultant Anaesthetist
#QuestionFeedback 9. GLP-1 Agonists Should Ozempic, Wegovy or Mounjaro routinely be stopped before surgery? Current UK multidisciplinary guidance generally recommends CONTINUING GLP-1 receptor agonists and dual GIP/GLP-1 agonists peri-operatively. Individual aspiration-risk assessment and appropriate mitigation remain essential. This differs from earlier guidance recommending withholding these drugs. SGLT2 inhibitors, by contrast, are generally omitted the day before and day of surgery because of the risk of euglycaemic ketoacidosis.
Read discussionDr Henry Jefferson, Consultant Anaesthetist
#QuestionFeedback 8. Hypercapnia Does very high PaCO₂ eventually cause respiratory depression? Yes, but it is important to distinguish this from the normal ventilatory response. Over the usual physiological range, ventilation increases approximately linearly with increasing PaCO₂. At extreme levels, severe hypercapnia can cause CNS depression, blunting ventilation and potentially leading to respiratory failure.
Read discussionDr Henry Jefferson, Consultant Anaesthetist
#QuestionFeedback 7. Electrical Charge What does C mean in an electrical calculation? Electrical charge is represented by Q and measured in COULOMBS (C). Charge = Current × Time Q = I × t Therefore: 1 C = 1 A·s 1 μC = 10⁻⁶ C Confusingly, C is ALSO used as the symbol for capacitance, although capacitance is measured in FARADS (F). The distinction is between the symbol representing a physical quantity and the symbol representing its unit.
Read discussionRegister for Oxford FRCA to participate and access 50 free Primary FRCA questions.
Register or sign in