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

Posted on December 18, 2025 by Pat Neligan

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

Posted on December 12, 2025 by Pat Neligan

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

Posted on November 5, 2025 by Pat Neligan

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

Posted on October 2, 2025 by Pat Neligan

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.

Fundamentals of Anesthesiology and Critical Care Series

Posted on September 14, 2025 by Pat Neligan

Here are the first 9 Tutorials in the Series – the majority are useful for Anesthesiologists and Intensive Care practitioners. Every tutorial contains something that you may not have previously known: I guarantee, who ever you are, that you’ll learn something.

Tutorial 1: Saturated Vapor Pressure

Tutorial 2: The Gas Laws

Tutorial 3: Mixtures of Gases

Tutorial 4: The Alveolar Gas Equation

Tutorial 5: Henry’s Law

Tutorial 6: Carbon Dioxide Solubility

Tutorial 7: Oxygen Solubility

Tutorial 8: Oxygen Content of Blood

Tutorial 9: Oxyhemoglobin Dissociation

Clinical Forum – Western Anaesthesia Symposium 2025

Posted on June 16, 2025 by Pat Neligan

Here is a presentation that I gave at WAS in April – looking at the best papers that had been published in Critical Care up to that point in 2024-25.

A SHORT COURSE ON LOCAL ANESTHETICS

Posted on May 28, 2025 by Pat Neligan

I published 3 tutorials on Local Anesthetics this Month. These are part of a new series of Anesthesiology Tutorials.

Tutorial 1 looks at the basic pharmacology of local anesthetics

Tutorial 2 looks at the various different drugs that we use, the volume and concentration. I discuss the maximum safe doses at the end of the tutorial.

Tutorial 3 looks at the history of, the diagnosis of and the treatment of Local Anesthetic Systemic Toxicity (LAST)

Metabolic Acidosis in 2025 – More Important than Ever!

Posted on May 28, 2025 by Pat Neligan

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

Anaphylactic Shock

Posted on April 3, 2025 by Pat Neligan

This tutorial, from the Introduction to Critical Care Series, looks at perioperative anaphylaxis. It covers topics that are relevant to practitioners in the OR, ICU, ED and wards.

Nutrition 3 – Timing and Route of Nutrition in ICU

Posted on March 19, 2025 by Pat Neligan

This HI-Impact tutorial looks at the common questions relating to commencement and route of nutrition in critical care. Is TPN good, bad or indifferent. Is enteral feed better than parenteral? When should we start feeding? Is it useful to add parenteral feed to enteral if the patients’ caloric goals have not been met? When should patients achieve their isocaloric goals. I guarantee you’ll learn something.

ORtoICU

Tutorials in Anesthesiology & Intensive Care

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