Capnography and Pulse Oximetry Quiz

Introduction to Measurement and Monitoring

• Measurement and monitoring are essential in a variety of fields, including medicine
• These techniques allow for the continuous assessment of a variety of patient parameters, which are crucial for patient safety and efficiency
• Monitoring is important for safety, conduct of anesthesia, ICU practice, assessment of critical conditions and research

Systems of Measurement

• Early systems were based on everyday objects, like body parts (e.g., cubit).
• The need for standardization led to the development of the metric system, with units based on the meter, kilogram, and second (originally Centimeter, Gram, Second, and then replaced by Meter, Kilogram, and Second - MKS)
• The international system of units (SI) further refined this system
• The metric system has become dominant, though some non-SI units are still in use (e.g., pounds, mmHg).

SI Base Units

• The SI system uses seven base units:
  • Second (time)
  • Meter (length)
  • Kilogram (mass)
  • Ampere (electric current)
  • Kelvin (temperature)
  • Mole (amount of substance)
  • Candela (luminous intensity)
• The symbols for these units are their first letter (except for the ampere which is A).

Derived Units

• Derived units are derived from the base units.
  • Examples include: Hertz, Newton, Pascal, Joule, Watt, cubic metre, metre per second,

Decimal Multiples and Submultiples

• These represent multiples of a unit, like thousands or millionths.
• Prefixes (mega, kilo, milli, micro, nano) represent these scaled units, enabling efficient use of diverse units.

Non-SI Units Temporarily Retained

• Some non-SI units continue to be used in specific contexts, particularly in medical practice, as these remain common in practice.
  • Examples:
    • Bar and Psi (pressure of compressed gases)
    • mmHg (for blood pressure).
    • cm H2O (for central venous pressure)
    • Calorie(heat energy).

Clinical Monitoring

• The anesthetist relies on his or her natural senses and simple aids (e.g., stethoscope) to monitor the patient.
• Modern medicine increasingly uses sophisticated monitoring devices to assess various parameters, including oxygenation, ventilation, circulation and temperature
• Advanced methods often utilize various techniques and equipment, enabling real-time measurements of physiological functions that aid in diagnosis and efficient treatment.

Pulse Oximetry

• Non-invasive; measures the percentage of oxygenated hemoglobin
• The percentage reading is shown with a pulsatile waveform, providing an assessment of the patient's overall physiological parameters, detecting abnormal patterns and enabling more accurate estimations

Capnography

• Measures expired carbon dioxide (EtCO2)
• A waveform, providing continuous assessment of ventilation

ABP Monitoring

• Several techniques include non-invasive, intermittent techniques (e.g. auscultation, palpation), and invasive methods, for monitoring blood pressure
• Involves cuff, manometer and stethoscope for blood pressure
• Accuracy of measurement is dependent on the proper positioning of the cuff to the artery and the size of the cuff

Invasive Blood Pressure Monitoring

• This method provides a continuous beat-to-beat assessment of blood pressure
• A catheter is placed into the artery.
• The pressure signal is converted to a numerical and graphical display

ICP Monitoring

• Intracranial Pressure(ICP) monitoring and assessment; measurement using a catheter or fiberoptic catheter
• Normal Range: 8-12 mm Hg
• Used when a rapid change and/or instability is expected

Techniques for Assessing Neurophysiological Responses

• These techniques apply stimuli and analyze the patient's responses, often involving the brainstem or other areas of the peripheral nervous system
• Neurophysiologic parameters can identify problems with nerves, the spinal cord or the brain, or their blood supply
• Monitoring can alert the surgeon, enabling corrections before permanent injury occurs.
• Techniques can include:
• Somatosensory evoked potentials (SEPs)
• Motor evoked potentials (MEPs)
• Brainstem auditory evoked potentials (BAEPs)
• Visual evoked potentials (VEPs)

Other Brain Monitors: Bispectral Index (BIS)

• The BIS is a single numerical measure of anesthetic depth, offering a more objective technique
• It reflects a form of processed EEG signals

Additional notes

• A wide range of measurements and monitoring technologies is available to assist in a variety of medical contexts
• Different techniques offer varying levels of invasiveness, detail and accuracy.
• Appropriate use demands a careful understanding of each technique's limitations and potential sources of errors.
• Data from different monitoring tools can be combined to provide a comprehensive picture of a patient's physiological state

This quiz covers key concepts related to capnography and pulse oximetry, including measurement techniques and the expertise of Tarik Sarhan. Test your knowledge on the functions and applications of these vital monitoring tools in medical settings.