Category Archives: ccmtutorials

The Blood Gas Machine – Measuring Oxygen, pH, Carbon Dioxide, Tips and Tricks and Derived Variables

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To round out the year, here are three tutorials on the blood gas machine, blood gas analysis and the blood gas printout.

The first tutorial looks at how oxygen is measured using the Clark Electrode on the blood gas analyser and demonstrates the importance of co-oximetry in modern blood analysis. From that the fractional saturation of hemoglobin with oxygen is derived.

The second tutorial explains the Glass Electrode that measures pH and PCO2. Subsequently I cover problems you might encounter with blood gas sampling. If you don’t want to watch the technical stuff, I strongly recommend you scroll to the middle of the tutorial (12 minutes in) as it covers information that all healthcare practitioners must know.

The final tutorial looks at all of that other data that appears on blood gas printouts that you may never have understood – and it can be really confusing – DERIVED or calculated variables (bicarbonate, temperature correction, TCO2, O2 content, Base Excess, Standard Bicarbonate, Anion Gap etc.). I cover both the Radiometer ABL machines and the GEM 5000. I guarantee you’ll learn something.

TUTORIALS ON CAPNOMETRY AND CAPNOGRAPHY

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Here are three tutorials on inspiratory and expiratory CO2 gas analysis. Tutorial 1 looks at Capnometry and the process behind measuring CO2 in exhaled gas. I cover mainstream CO2 analysis and explain why the end tidal CO2 (EtCO2) may be high or low. Tutorial 2 addresses the Capnograph, the trace and anomalies of the Capnograph at the time of intubation. I also explain Sidestream and Microstream CO2 and gas analysis. The final tutorial will be very helpful to anesthesiologists, particularly those taking exams: I go through a series of abnormal Capnographs, explaining why they are abnormal. I guarantee that you will learn something.

Tutorials on Pulse Oximetry

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There are two tutorials on pulse oximetry. The first looks at the SpO2 and how it is measured. The second looks at the pleth waveform and problems that we commonly encounter with pulse oximetry in general. I guarantee you’ll learn something.

Carbon Dioxide in Acid Base – Three Tutorials

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As part of my fundamentals of Anesthesiology and Critical Care Series I have posted 3 tutorials on the Role of CO2 /HCO3 in Acid Base Balance. These are entirely new tutorials (not part of the previous acid base series – that I have not finished yet! There is some overlap and updated facts and figures) and I have put a lot of work into getting the message of why the respiratory system is so important in acid base. Tutorial 1 is the basics of acid base. Tutorial 2 discusses respiratory acidosis, acute and chronic, and respiratory alkalosis. Tutorial 3 discusses respiratory compensation for acute metabolic acidosis.
Although I cover the respiratory component in great depth, I also explain what metabolic acidosis is, what causes it and briefly discuss the anion gap, expected bicarbonate, base deficit and base deficit gap. I guarantee that you will learn something.

Metabolic Acidosis in 2025 – More Important than Ever!

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This is a longer version of the lecture that I delivered at the 2025 College of Anaesthesiologists of Ireland Annual Scientific Meeting.

Acute Coronary Syndromes and Cardiogenic Shock

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This is a trio or tutorials on Acute Myocardial Ischemia, Acute Coronary Syndromes and Cardiogenic Shock.

Critical Illness Nutrition 2 – Calories, Protein, Enteral Route, Gastric Residuals

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This is the second tutorial in the nutrition series. Previously I looked at metabolism in critical illness. In this tutorial I start to answer many of the questions that arise on rounds principally: how many calories does the patient need? How much protein? What are the routes of food administration? Is there a benefit to post pyloric feeding tubes? Should I feed the stomach continuously or by bolus? Should I check gastric residual volumes? I provide you with the answers to these questions using the best available evidence.

Critical Illness Cachexia (metabolism in acute and chronic critical illness)

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Patients who spend significant time in critical care may lose a staggering amount of weight, particularly lean body mass. In early critical illness glucose is used as the principle energy source in the stress response; glycogen is rapidly exhausted and glycogenic amino acids are mobilized from muscular protein to generate glucose via gluconeogenesis, to maintain plasma glucose levels to feed, principally red blood cells. This has a major impact on muscle mass and in particular muscular strength, that may take years, perhaps a decade to restore. The most effective mechanism of preventing the development of critical illness cachexia is to curtail the duration of the stress response, by rapid source control, deresuscitation and early mobilization. In general, patients should be receiving full nutrition and be mobilized by day 8 following injury.