EGGN 3610 Bioinstrumentation

1
EGGN 3610Bioinstrumentation

• Dr. Tuinstra
• 2.1.11

2
Example Clinical Instruments
Blood Pressure
EKG
Thermometer
3
Major Manufacturers of Bioinstruments
4
Basic System
Patient
Clinical Instrument
Analog Processing
Sensor
Analog to Digital
Storage
DSP
Control Feedback
Display
Transmit
5
Analog Processing Important Circuits in
Bioinstrumentation
Most circuits used in bioinstrumentation circuits
involve the use of operational amplifiers
6
Important Op-amp circuits
Inverting Amplifiers
7
Important Op-amp circuits
Differential Amplfier
8

• The key question is
• What are the quantities that we will measure?

9
Biopotential
Electrolyte


Metal
Electrolyte
-
-
-

-

-
-
Electrolyte



Electrolyte
Half Cell Potential Voltage arising from the
distribution of charge around a metal in an
electrolyte
10
Measuring Biopotential

• non-invasive
• invasive

Electrode 1
Diff Amp
Electrode 2
11
BioSensors-ECG
Adhesive Disk
ECG Electrocardiogram, Measures the electrical
impulses that are associated with a beating
heart. ECG EKG
Snap Connector
12
Human Heart Anatomy
Right side of heart pumps deoxygenated blood to
the lungs. Left side of heart pumps oxygenated
blood to the rest of the body. Heart beat
consists of contraction (systole) and relaxation
(diastole).
13
The Heart Beat
The Virtual Heart http//thevirtualheart.org/anat
omyindex.html

• Key Terms
• Depolarization Occurs when interior of heart
  cells goes from being more negative with respect
  to the extracellular fluid to more positive.
  Travels as a wave in the heart. Causes
  Contraction (systole)
• Repolarization Normal voltage potential balance
  is regained. Also travels as a wave in the heart
  (diastole).

14
ECG (EKG) Signals
P-wave Atrial DepolarizationLeft and right
atria contract QRS Complex Ventricular
DepolarizationLeft and right ventricles
contract T-wave Repolarization of the ventricles
15
BioSensors-EMG
EMG Electromyography - measures the electrical
potential of muscles during contraction and rest.
EMG Electrodes
16
BioSensors-EEG
EEG Electroencephalography Used to monitor brain
activity
17
Physical Measurements

• Measurement of Temperature
• May be measured electronically using a thermistor
• Thermistors present a resistance that changes
  with temperature

18
Measuring Motion

• Linear Variable Differential Transformer (LVDT)

19
Other ways to measure linear motion

• Strain Gauges
• Used in measuring blood pressure (inside the
  blood pressure cuff)

20
Measuring Airflow
Differential Pressure
Screen
Fleish Pneumotachometer
21
Measuring Airflow

• Common Airflow Measurements
• Forced Vital Capacity (FVC)
• How much air can you exhale in one breath?
  (litres)
• Peak Expiratory Flow (PEF)
• What is the maximum rate of exhaling? (litres per
  second)

22
Measuring Gases in Blood

• What we typically measure
• Oxygen (O2)
• Carbon Dioxide (CO2)
• pH
• These measurements usually made during surgery or
  while patient is in the ICU.

23
Measuring Oxygen

• Oxygen carried in two places in blood
• Dissolved in plasma (2)
• Attached to hemoglobin (oxyhemoglobin)

24
Measuring Oxygen
-

V
A
Silver/Silver chloride
Gold
Electrolyte
OH-
Cathode
Anode
O2
25
Measuring Oxygen

• It is possible to measure the oxygen content of
  blood optically
• This follows from the observation that arteries
  appear red and veins appear blue.

26
Measuring Oxygen
?1
?2
27
Measuring Oxygen
28
Transmission-type Pulse Oximeter Finger Probe

• Measure Red/Infrared Ratio
• Digital Signal Processing is used to do the
  math

29
Microbial Biosensors

• Primary Uses
• Detection of pollutants in the atmosphere
• Detection of chemical warfare agents
• Detection of biological warfare agents
• With this technology the biology is in the sensor

30
Microbial Bio-Sensors
Bacteria
Biproducts
Chemical Agents
Electrode
31
Optical BioSensors

• We transmit light into a medium to be tested and
  measure characteristics about the returned light

32
Optical BioSensors
Computer
Detector
Optical Fiber
Transceiver
Material to be tested
33
BioSignal Processing
Patient
Analog Processing
Sensor
Analog to Digital
Storage
DSP
Display
Transmit
34
Where do biosignals come from?

• Bioelectric
• Biomagnetic
• Biochemical
• Biomechanical
• Bioacoustic

35
Dr. Ts BioSignal Tree
BioSignals
Continuous
Discrete
Random
Deterministic
Deterministic
Random
Periodic
Aperiodic
Periodic
Aperiodic