C8.ii · Oxygen & Carbon Dioxide Disturbances

This viva will explore your knowledge of the following areas: Arterial blood gases and oxygen measurement. What is the difference between hypoxia and hypoxaemia?

This viva tested knowledge on pulse oximetry the physiology related to hypoxia and hypoxaemia.

This Viva will explore knowledge of the measurement and interpretation of Blood Gases and respiratory pharmacology. Subsequent discussion involved understanding differences between hypoxia and hypoxaemia, the Clark electrode, physiological mechanisms of hypoxaemia, asthma and bronchodilators

This Viva relates to the respiratory changes of pregnancy at term, hypoxaemia and the foetal circulation. Q 1. Describe the respiratory changes in pregnancy at term. Subsequent questions sought a description of ABG at term pregnancy, physiological mechanism to explain an increased A-a gradient, causes of a low PaO2 in a patient with a normal A-a gradient, the response of hypoxemia to supplemental O2 when the A – a gradient is normal and when abnormal, and a description of the foetal circulation and the changes that occur at birth.

This station will explore your knowledge of the physiology associated with the interpretation of Blood Gases and oxygen analysis. How would you interpret this Arterial Oxygen Tension? PaO2 = 24.6 mmHg (3.2 kPa) This viva tested the candidates’ knowledge of hypoxaemia, associated respiratory physiology and oxygen measurement. Specifically measurement of oxygen tension, the alveolar gas equation and physiological responses to hypoxia. Measurement of oxygen tension, in particular the principles behind the Clark electrode, was well done. The area candidates struggled the most was explaining and integrating arterial blood gases and the physiological principles surrounding them.

This viva will test your knowledge of hypoxemia, oxygen therapy and pulse oximetry The following is a blood gas of a young person who has taken a sedative drug overdose. pH 7.2 PO2 40 mmHg PCO2 80 mmHg HCO3- 28 mmols/L Describe this blood gas Apart from being asked to describe the blood gas, candidates were also asked about the Henderson-Hasselbach equation, causes of hypoxaemia, pulmonary shunt, response to supplemental oxygen and pulse oximetry.

This information is from a patient with a pulmonary embolism FIO2 0.5 PaO2 100mmHg PaCO2 20mmHg Calculate the A-a gradient.

What are the causes of a low PaO2?