← All decks
The first 25 slides, exactly as they appear. The full deck has 139 content slides.
Anaesthesiology
Noninvasive monitoring
Built from Al-Shaikh — Essentials of Equipment in Anaesthesia, Critical Care and Peri-operative Medicine, 6e
What’s inside
12 sections · 139 slides
Overview
- What this session covers
- First principles: monitors extend the senses
- Two families of monitoring
Integrated monitoring
From a cluttered machine to one clean screen
- From many boxes to one screen
- Integrated patient and machine monitoring display
- Portable compact anaesthesia monitor
- Colour-coded values and waveforms on one screen
The electrocardiogram (ECG)
Reading the heart's electricity from the skin
- What the ECG actually measures
- Bipolar vs unipolar leads
- The four components of an ECG system
- Silver / silver-chloride ECG skin electrode
- Getting a clean trace: attaching electrodes
- Cleaning the signal: high-pass and low-pass filters
- Unfiltered versus filtered ECG signal
- Two ECG modes: monitoring vs diagnostic
- Electrode configurations: which leads to use
- The CM5 lead configuration
- Display standards and ST-segment monitoring
- ECG with ST-segment monitoring
- ECG pitfalls and safety points
- Sources of ECG interference and how to reduce it
- Why is the ECG useless as a monitor of cardiac output?
Noninvasive arterial blood pressure
Reading the pressure from a squeezing cuff
- Oscillometry: the everyday method
- What is inside the device
- How oscillometry finds the pressures
- How cuff-pressure oscillations map to blood pressure
- Choosing the right cuff width
- Getting the cuff right
- Where cuff pressures go wrong
- The Finapres: continuous finger pressure
- The Von Recklinghausen oscillotonometer
- The Von Recklinghausen oscillotonometer
- Your automated cuff reads a very low pressure. What must you check before treating?
Pulse oximetry
Colour-reading the blood for its oxygen
- What pulse oximetry does
- Handheld pulse oximeter
- The probe and its parts
- Finger and ear pulse-oximeter probes
- Sequenced LEDs and the photodetector
- The physics: why two colours work
- What contributes to the absorbed light
- Beyond two colours: multi-wavelength oximetry
- When to distrust the oximeter
- Sources of error in pulse oximetry
- Two more practical cautions
- A smoke-inhalation patient has SpO2 of 99% but looks unwell. Why might the number be wrong?
- Masimo: seeing through movement
- Multi-wavelength 'rainbow' co-oximetry
- SedLine and O3: brain and tissue oximetry
- The SedLine brain-function monitor and forehead sensor
End-tidal carbon dioxide
Capnography: watching the breath the patient breathes out
- The principle behind capnography
- The normal capnograph waveform, phase by phase
- Three words that are easy to confuse
- Why end-tidal CO2 is not quite arterial CO2
- The carbon dioxide gradient across the lung
- What the analyser contains
- How the reading is produced
- Inside an infrared carbon dioxide analyser
- The infrared detector principle
- A main-stream capnograph sensor
- A side-stream monitor measuring CO2, oximetry and agent
- Photoacoustic spectroscopy: listening to the gas
- Side-stream and main-stream in practice
- Side-stream versus main-stream analysers
- A portable capnograph and oximeter
- What end-tidal CO2 tells you
- Causes of raised and lowered end-tidal CO2
- Abnormal capnograph traces: rebreathing and COPD
- Capnography pitfalls
- Overlapping CO2 and nitrous oxide infrared spectra
- Immediately after intubation the capnograph shows no trace. What does this mean?
Oxygen concentration analysers
Proving the patient is getting oxygen
- Why and how we measure inspired oxygen
- Different types of oxygen analyser
- Paramagnetic (Pauling) analyser: how it works
- The paramagnetic oxygen analyser
- Two more oxygen sensors
- Polarographic (Clark) oxygen electrode
- Oxygen analyser practicalities
Nitrous oxide and agent analysers
Measuring the vapour the patient actually receives
- Why measure the agent, not just set the dial
- Inspired and end-tidal agent concentrations displayed
- Infrared agent analysis and its wavelengths
- How an infrared agent monitor identifies the vapour
- Automatic agent identification
- Infrared absorption spectra of the volatile agents
- Building a spectral shape to identify the agent
- Other ways to measure agents
- The mass spectrometer
- Which technology measures which gas
Measuring gas volume and flow
How much gas is actually moving
- The Wright respirometer
- The Wright respirometer
- Inside the Wright respirometer
- The pneumotachograph
- A pneumotachograph flow sensor
- Adding a Pitot tube for accuracy
- Combined pneumotachograph and Pitot tube
- Pressure-volume loops before and during laparoscopy
- Cross-section of a Pitot-tube flowmeter
- What affects a pneumotachograph reading
Ventilator alarms
Guarding against disconnection and obstruction
- Why ventilator alarms are mandatory
- The pressure-monitoring alarm
- A pressure-monitoring ventilator alarm
- The volume-monitoring alarm
Neuromuscular monitoring
Measuring how paralysed the patient is
- Peripheral nerve stimulators: the idea
- A peripheral nerve stimulator
- How stimulation is done properly
- Continuous neuromuscular transmission monitoring
- Graphical train-of-four display and trend
- Patterns of stimulation
- Twitch, tetanus and train-of-four responses
- The double-burst stimulation pattern
- Interpreting the block carefully
Depth of anaesthesia
Reading the brain to prevent awareness
- The bispectral index (BIS)
- Bispectral index as part of patient monitoring
- The BIS sensor
- Adult BIS forehead electrode
- BIS electrode connected to its monitor
- Paediatric BIS electrode
- The BIS scale and what it means
- The BIS value scale
- What can fool the BIS
- Entropy of the EEG
- Entropy of the EEG across anaesthesia
- Key-points summary marker
- Numbers worth remembering
- A paralysed patient shows a BIS of 35. Can you be sure they are deeply anaesthetised?
- Three things to carry away
- References
- Essentials of Equipment in Anaesthesia, Critical Care, and Perioperative Medicine