1. Pulse Transit Time Measuring Device
Team:
Jonathan Baran, Karen Chen, William Stanford, Mark Yarmarkovich
University of Wisconsin-Madison
BME 200/300
October 20, 2006

2. Intellectual Property
All information provided by individuals or Design Project Groups during this or subsequent presentations is the property of the University and of the researchers presenting this information. In addition, any information provided herein may include results sponsored by and provided to a member company of the Biomedical Engineering Student Design Consortium (SDC). The above information may include intellectual property rights belonging to the University to which the SDC may have license rights.
Anyone to whom this information is disclosed:
1) Agrees to use this information solely for purposes related to this review;
2) Agrees not to use this information for any other purpose unless approved in advance by the Project Group, the Client / SDC, and the Advisor;
3) Agrees to keep this information in confidence until the University and the relevant parties listed in Part (2) above have evaluated and secured any applicable intellectual property rights in this information;
4) Acknowledges that worldwide patent rights are waived if publication or public dissemination occur prior to filing a corresponding U.S. provisional or utility patent application.

3. Department of Pedatrics
Client:
Dr. Christopher Green
Department of Pedatrics
Advisor:
Wally Block
Associate Professor
Department of Biomedical Engineering

4. Client Motivation Effects of sleep apnea on children
Sleep apnea is a disorder where a patient’s tongue will fall into the back of their mouth
Can cause blocked airway
Epinephrine affects pulse transit time
Conducting tests in sleep centers are not economically feasible
A more feasible option is desired

5. Pulse Transit Time
ECG
Pulse caused by the pressure wave travels down to the fingertip (takes about ms)
PPT is the difference between the peak of the R wave and the peak of the pressure wave (Plethysmogram)

6. Problem Statement
Current instruments used in the measurement of pulse transit time are inefficient for home use. An existing product with working ECG and pulse wave circuits along with software to analyze the data has been provided. The primary goal will be to optimize the existing setup for use at home. This will be performed by miniaturizing the circuit, improving the signal to noise ratio, and improving of the already existing software. These tasks will attempt to be rectified by numerous design additions.

7. Specifications Finger probe (uses LED 805nm)
Circuits to magnify detected voltages
Power supply to run for up to 10 hours
Peak detection of ECG (QRS complex) and plethsymograph waves (finger tip)
Reduced wires
Small, portable device

8. Plethysmogram Circuit
Existing Device Setup
Labview Program
ECG Circuit
Laptop Computer
DAQ
Plethysmogram Circuit
User Display

9. Existing Setup: Pros/Cons
Data stored directly on computer
Analyzed immediately after collection
Cons
Bulky
Restricts patient movement in sleep
Cords detach during sleep
High noise levels
Imperfect software

10. Existing System Circuits
ECG Circuit
Buffer Stage
Provides a clean signal
Amplify the signal
Differential Amplification
Minimize interference
Bandpass Filter
Cuts of certain frequencies

11. Existing System Plethysmogram
Pressure wave circuit
Bandpass filter
High pass filter
Amplification
Low pass filter

12. Software - LabVIEW ECG template
Eliminates low frequencies in ECG and plethysmograph signals
Threshold detection to determine times of QRS complex and plethysmograph peak
Difference of QRS complex and peak is calculated = PTT

13. Proposed Setup Transfer to computer when needed Improved ECG Circuit
Memory
Plethysmogram Circuit
Improved Labview Program

14. Proposed Setup: Pros/Cons
Memory Addition
Pros
Small and wearable
Eliminates bedside computer
No restriction of movement
Cons
No immediate permanent data storage
No immediate analysis

15. Microcontroller/Memory Addition
Specifications
Needs A/D converter
10-bit microcontroller will handle data best
Minimum of 100Mb of data to safely store all data
Input from two leads recorded 30 times per second for up to ten hours
Memory interface
EasyPSoC3 allows for all of these features in a developmental environment
EasyPSoC3 $199.00

16. Pros of Additional Modifications
Improved ECG circuit
Reduce noise in the circuit
Miniaturize circuit
How will this be done?
Addition of an instrumentation amplifier
Reduces noise by combining many parts of the circuit into one
Improved LabVIEW software
Allow for more accurate measurements
How will this be done?
Programming of the software to account for skipped beats

17. Cost List for Improved Setup
EasyPSoC3
$199.00
Memory Chip 512MB
$35.99
Analog Devices AD624AD Instrumentation Amplifier
$23.50
Total=
$258.49

18. Future Work Incorporate flash memory Obtain Microprocessor unit
Program processor
Incorporate flash memory
Rework Circuit
Improve LabView program
Edit out skipped beats

19. References

20. Questions?