Development of a Continuous Respiration Olfactometer for Synchronous Odour Delivery During Normal Re

1
Development of a Continuous Respiration
Olfactometer for Synchronous Odour Delivery
During Normal Respiration

• Caroline M. Owen 1, 3, John Patterson 1, 3 and
  David G. Simpson 2

1 Sensory Neuroscience Laboratory and the School
of Biophysical Sciences and Electrical
Engineering, 2 Brain Sciences Institute,
Swinburne University of Technology 3
Cooperative Research Centre for International
Food Manufacture and Packaging Science.
2
Introduction

• Reliability of measurement of responses to odours
  dependent on delivery system
• Timing, quantity delivered.
• Avoid concomitant excitation of other sensory
  systems.
• Discourage artificial methods of administering
  odorous stimuli (pulses, blast olfactometry).
• Variations in subjects sampling behaviour during
  odour presentation contributes to variations in
  monitored responses.
• Continuous Respiration Olfactometer
• Monitoring natural respiratory cycle, delivering
  air or odour during inspiration.

3
Continuous Respiration Olfactometer
A Delivery tubing D Pressure
Transducer B Pneumotach E
Microprocessor C Respiratory sampling tubing
F Motor control boards
4
Respiratory monitoring apparatus
A Disposable medical face mask B Two-way
non-rebreathing valve C Pneumotachometer (PNT)
D Tubing inserted in mask E
One-directional spiral-diaphragms F Exhalation
port G PNT pressure taps and tubing

• PNT signal sent to differential pressure
  transducer on serial interface device
• Output amplified as voltage proportional to flow
  rate

5
Odour Delivery Syringe System

• 50 ml gas-tight glass syringes with Teflon sealed
  plungers
• Small bore fluoropolymer tubing
• Stepper motors connected to syringe plungers

A Odour syringe B Air syringe C Luer
locks D Syringe plungers
E Re-circulating ball screws F Stepper
motors G Connection to serial interface device
6
Serial Interface Device

• Differential pressure transducer connected to PNT
• 12-bit Analog to Digital Converters
• Serial communication device (RS232
• Motor outputs to stepper motor control boards
• Microprocessor -
• Controls ADC and syringe stepper motor boards
  handles serial communication connected to
  monitoring computer.
• Processes incoming respiratory information
• Stepper motor controller converts digital
  information from each of the motor output
  transistors into series of voltages to control
  motors driving the syringes
• Adjustable gain control to adjust analog output
  of the circuit prior to signal being fed to ADC.

7
Serial Interface Device
A Stepper motor boards B Respiratory LED
display C Respiratory signal potentiometer D
Tube adaptor ports
E Monitoring computer connector F EEG
computer connector G Syringe connector H
Indicator lights (motor drives, serial sampling)
8
Respiratory Monitoring Software

• Respiratory flow rate monitored by means of
  serially transmitted samples
• Comparisons performed to determine
• Peak flow rate
• Respiratory rate
• Timing of respiratory parameters
• Volume of inspiratory breath
• Calculates timing of odour delivery (peak
  inspiration )
• Signal sent to microprocessor to drive syringe
  stepper motor
• File used to generate pseudo-random delivery
  sequences of different airodour ratios
• Stores to file all subject, respiratory and
  stimulus delivery information.

9
Calibration Procedures

• Calibration tests studied the effect on the
  system of natural variations in respiratory flow
  amplitude for artificial signals and for
  different subjects.
• Study of effect of individual variations over
  time
• Test odour 1 ml n-butanol (55.5 ppm)
• Mask dead-space calculated as 50ml (effective
  dilution factor of 50 ? mask concentration 1.11
  ppm
• Subject (24 year old female non-smoker)
• 5 min. trials with initial respiratory monitoring
  period
• 1 ml air or odour airodour ratio of 31
• 4 trials (each trial 7 -8 mins. 5 min. between
  each trial)
• 162 air 49 odour deliveries

10
Hardware Calibrations

• Timing of motor drive injection respiration
• Frequency of motor drive and syringe flow rate
• Relationship between number of motor steps and
  syringe volume
• Linear relationship for both syringes
• Control and accuracy of volumes delivered
  consistent with volumes delivered to subject

• Nature of air/odour delivery caused by syringe
  movement
• Gas pressure on-off profile approximated a
  rectangular wave

• Recorded from digital storage oscilloscope (50mV
  per division, 0.1 s sweep) during motor drive
  displacement
• No odour leakage or tail-off by residual pressure
  in the syringe ? Pulse delivery

11
Conclusions and Future Directions

• Preliminary tests demonstrated the CRO can be
  used to deliver known quantities of odour
  synchronous to natural respiration
• System effectively provided accurate information
  concerning timing and quantities of air or odour
  delivered.
• Future analysis of gas samples from the system
• Determine actual profile of gas delivery
• Verify the concentrations delivered
• Actual concentration delivered to the nasal
  epithelium
• Individual variations in size of epithelium,
  nasal cavity, rate of breathing, volume inspired
• Known concentration is placed in delivery system
  but biological variations prevents accurate
  knowledge of actual concentration reaching the
  olfactory epithelium