This module provides an introduction to the principles of physics and physical instrumentation as they are applied to the measurement and recording of human physiological signals. The module is inextricably linked to the other two co-requisite modules in this course.
The aim of this module is to provide the student with knowledge and understanding of the physical principles of fluid dynamics applied to blood flow, and the physical principles of electric, resistive and temperature measurement devices, among others, as they are applied to blood pressure measurement and blood flow measurement.
Principles of Fluid Dynamics (8 hours)
- Hydrostatic pressures, Darcy’s Law, Laplace’s Law, the Continuity Equation, Bernouilli’s equation; rheology of Blood, the effect of haematocrit on blood viscosity, Poiseuille’s Law, the Fahraeus and Fahraeus-Linquist Effect; turbulence; branching tubes; application of Bernouilli’s equation to measure orifice diameter; the Windkessel theory and autoregulation.
Blood Pressure Measurement; Principles and Devices (8 hours)
- Indirect Measurement
Pascal’s principle - application to sphymomanometer and manometer; operating characteristics (calibration, zero point). Measurement technique for measurement of pressure using sphymomanometer, patient position, sources of uncertainty and combination, equipment management issues. Comparison of measurement to automated oscillometric technique.
- Direct Measurement
Strain Gauge resistive transducers (bonded and unbonded), principles of operation including operation of the Wheatstone bridge. Construction and principles of operation of a strain gauge transducer for biomedical applications. Effects of fluid-filled catheter and transducer damping on systolic and diastolic blood pressure measurements. Measurement of damping response (fast flush technique) and relation to catheter and transducer characteristics (e.g., resistance, compliance and inertance).
Blood Flow Measurement; Principles and Devices (8 hours)
Blood Volume Flow Measurement
- Dilution
- bolus injection, the Stewart-Hamilton Equation; constant-rate injection; time-varying flow injection, errors in dilution techniques.
- Indicator transport
- the Fick Equation, indicator types (selective, inert, isotopes), application to cardiac output measurement.
- Thermal techniques
- thermistor operation, thin-film flow meters, thermal dilution.
- Plethysmography
- venous occlusion plethymography, strain-gauge plethysmography; voltage measurement and impedance plethysmography, photoelectric plethysmography (LEDs).
Blood Velocity Measurement
- Electromagnetic flow meters
- Faraday’s Law of electromagnetic induction, inductors, application to measurement of blood velocity.
A typical laboratory programme may include experiments taken from the list below or equivalent experiments may be used:
- Determination of the Resistivity of the material in a wire
- Investigation of the Characteristics of a Thermistor;
- Determination of Young’s Modulus for a Wire;
- Determination of Hooke’s Law constant. Exploring Harmonic Motion;
- Exploration of Damped Harmonic Motion;
- Practical Blood Pressure Measurement – Invasive and Non-Invasive Demonstration;
- Demonstration of Volume Flow by Venous Occlusion Plethysmography;
- Photoelectric plethysmography.
Lectures, laboratory sessions, student-directed learning and computer based learning.
24 hours of lectures, 18 laboratory hours.
| Module Content & Assessment | |
|---|---|
| Assessment Breakdown | % |
| Formal Examination | 40 |
| Other Assessment(s) | 60 |