G2.i · Blood Gas Analysis

This viva will examine acid-base physiology and pharmacology. Interpret these lab values using either the traditional or Stewart (physicochemical) approach to acid-base. pH 7.20 (7.35 - 7.45) pCO2 39mmHg (5.2 kPa) (35 - 45mmHg or 4.7-6.0 kPa) HCO3- 15mmol/l (22 - 26mmol/l) Lactate 10mmol/l (0 - 2mmol/l) BE -14 mmol/l (-3 - +3mmol/l) Na 126 mmol/l (135 - 145mmol/l) K 3 mmol/l (3.7 - 4.7mmol/l) Cl 82mmol/l (101 – 110mmol/l) Cai 1.5mmol/l (1.15 – 1.30mmol/l) Mg 1mmol/l (0.7 – 1mmol/l) PO4 1.5 mmol/L (0.8 – 1.5 mmol/l) Albumin 20g/L (35 – 50 g/L)

This VIVA will examine acid-base and renal physiology and pharmacology. Outline the principles of the Stewart (physicochemical) approach to acid base disturbances. Using this approach interpret the arterial blood gas below. (Image removed from report.)

This VIVA will examine acid-base physiology. Describe the following arterial blood gas. (Image removed from report.)

This viva will examine on acid base physiology. Define pH and its physiological importance. Describe how pH is measured by the blood gas machine.

This viva will explore your understanding of acid-base physiology. Please interpret the following blood gas: pH: 7.30 Na: 133 mmol/L pCO2: 19 mmHg K: 4.8 mmol/L pO2: 79 mmHg Cl: 104 mmol/L HCO3: 9.0 mmol/l Lactate: 7.5 mmol/L FiO2: 30%, Temp: 37.5C Base Excess: - 16.4 mmol/L

This viva will explore your understanding of acid base physiology. Please interpret this blood gas. pH 7.30 pO2 400 mmHg (53.3 kPa) pCO2 30 mmHg (4 kPa) HCO3- 14 mmol/L BE – 8 mmol/L Na 140 mmol/L K 4 mmol/L Cl 120 mmol/L

This viva will explore your understanding of acid-base physiology. List the abnormalities in this arterial blood gas analysis. FiO2 0.5 pH 7.1 PCO2 25 mmHg (3.3 kPa) PO2 100 mmHg (13.3 kPa) HCO3- 7 mmol/L Base deficit -19.9 Na+ 133 mmol/L K+ 4.5 mmol/L Cl- 105 mmol/L Anion gap 25 Lactate 7 mmol/L

This viva will assess your knowledge of renal physiology. Please interpret the following blood gas: Temperature 37.5°C pH 7.31 BE -4 mEq/L pCO2 39 mmHg (5.2 kPa) Na+ 136 mmol/L pO2 84 mmHg (11.2 kPa) K+ 3.0 mmol/L HCO3 18 mmol/L Cl- 101 mmol/L FiO2 30% Lactate 3.4 mmol/L

This viva will assess your knowledge on acid-base. Define pH. Describe how pH is measured by the blood gas machine?

This viva will explore your knowledge of maternofoetal physiology. This is a normal blood gas of a pregnant woman at term breathing room air. Outline the changes and explain their physiological basis. pH 7.45 pO2 105 mmHg pCO2 30 mmHg HCO3- 20 mmol/L BE -2

This viva will explore your knowledge of metabolism related to acid-base physiology. What does this blood gas show? pH 7.10 BE -20.4 HCO3- 8 mmol/L Na+ 145 mmol/L K+ 4.4 mmol/L Cl- 113 mmol/L

This viva will explore your knowledge of acid-base physiology. Please interpret this arterial blood gas: pH 7.30 pO2 400 mmHg (53.3 kPa) pCO2 30 mmHg (4 kPa) HCO3- 14 mmol/L BE - 8 mmol/L Na2+ 140 mmol/L K+ 4 mmol/L Cl- 120 mmol/L

This viva will examine your understanding of arterial blood gases and carbon dioxide. Interpret this arterial blood gas. pH 7.27 pCO2 55 mmHg (7.3 kPa) pO2 144 mmHg (19.1 kPa) HCO3 24 mmol/L BE 1 mEq/L

This viva will explore hypoxia. Interpret this arterial blood gas. Patient is breathing O2 at 6 litres/minute via a Hudson mask. pH 7.50 PaO2 55 mmHg PaCO2 30 mmHg HCO3- 22 mmol/L BE -2

Estimate the values for an arterial blood gas expected for a patient who has a saturation of 85% on FiO2 = 0.5 Explain the values. • pH • PO2 • PCO2 • HCO3 • BE • A-a gradient Use the paper and pen provided below and take into the viva.

This viva is on maternal oxygenation. What are the values for the following parameters in an arterial blood gas for a female who is 38 weeks pregnant? pH pO2 pCO2 HCO3 BE SaO2

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 discussed arterial blood gases, dead space, the measurement of carbon dioxide and capnography.

This Viva tested knowledge of blood gas interpretation and insulin physiology.

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 will examine maternal physiology and pharmacology. Write down the expected values in an Arterial Blood Gas for a pregnant woman at term. Subsequent discussion involved respiratory changes with pregnancy, including spirometry, pharmacology of drug transfer across the placenta, pharmacology of syntocinon and ergotamine.

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.

a period of prolonged vomiting. An arterial blood gas analysis was performed on room air, revealing the following findings. pH 7.59 (7.35 – 7.45) PaCO2 58 mmHg (35 – 45) PaO2 72 mmHg (90 – 110) HCO3- 59 mmol/L (22 – 32) Interpret the findings. This viva tested the candidate’s knowledge of renal physiology related to the control of urinary pH, effects of acetazolamide and frusemide upon metabolic acid base state and respiratory response to metabolic acid base changes. The main points expected for a pass were knowledge of : • Respiratory response to changes in metabolic acid base. Use of correctly labelled graph or common formulae • Renal handling of H+ at the proximal and distal tubules. • Mechanism of HCO3- reabsorption and regeneration • Urinary buffers such as phosphate, ammonia and glutamine • Mechanism of frusemide associated metabolic alkalosis • Affect of acetazolamide on HCO3- The use of illustrations greatly assisted candidates to answer questions within this viva Syllabus : D1-2e, D2a and B1c-2a & b Reference : Textbook of Medical Physiology by A. C Guyton & J. E Hall.