AdINSTRUMENTS POWERLAB 26T
By J. Paul W. Roberts
The AdInstrument PowerLab 26T is an integrated data recording unit, with such
features as a dual Bio Amp, an isolated stimulator, trigger input and two
independent analog outputs (non-isolated). The PowerLab has various transducers,
which can be used to measure different physiological activities such as heart rate,
breathing rate, muscle reactivity whether it be force generated from twitch or reflex
from stimulation. All information is measured using transducers hooked up to the
PowerLab, and with the PowerLab plugged into a computer the software programs
Chart and/or PowerLab will graph the data as designated by the user in regards to
Chart is the foundation for gathering data; Lab Tutor is largely based on similar
capabilities. Chart will graph data received from the PowerLab and transducers.
Chart will allow the user/professor/student to create their own lab, or just collect
various data from specimen/volunteers. Chart is a more in depth program, which
allows the user to manipulate receiving data, as well as analyzing data. Learning
all the capabilities of Chart is very time consuming and most likely require someone
with an extensive research history and be knowledgeable with computers.
Assuming universities or research labs have the resources multiple PowerLabs can
be hooked up and ran with one computer running Chart. Benefits of running
multiple PowerLab’s could be multiple volunteer readings. Chart can make two
distinctive graphs from one transducer available with the PowerLab.
Lab tutor is a program that also comes with the PowerLab; this program has labs
already installed which allow the user to test human or animal physiology. The
labs that are available are more of a selling point for universities and research labs
to purchase the PowerLab. The labs come with a lab report section asking the user
questions that seem to ask “which is better, using the manual method or using the
PowerLab?” The labs do have some benefits for those that are not as educated with
the physiological nature of mammals. The labs will generally guide the user
through the labs instructing what to do, than analyze data right after receiving the
data. As stated there is a lab report at the end of each lab, which asks users to
think about why the data on the graphs alters where it does. These lab report
question seem to be beneficial for students to be able to apply lecture material to
assist in the analysis process.
Transducers are the instruments that plugged into the PowerLab 26T. There are
various transducer that come with the PowerLab, some that are included are,
sphygmomanometers, respiratory belt, finger pulse transducer, electrode (for
muscle stimulation), cardiomicrophone (similar to a stethoscope), and many others
depending on which physiological information is desired. Lab tutor definitely makes
extensive use of all the transducers that accompany the PowerLab. Those that are
not familiar with the PowerLab and transducers will quickly become familiarized
with the hardware. Lab tutor complements the PowerLab as more of a tutorial for
those not quite familiar with any transducers or understanding graphed data.
In the 6 weeks of working with the PowerLab 26T, I was able to work through the
introduction, and 5 labs using Lab tutor. These are the labs I completed.
Learning objectives for this lab are
• Effects on breathing of voluntary hyperventilation
• Effects on the respiratory pattern of rebreathing expired gas
• Relationship between breathing and heart rate
Fig1. Apparatus Fig2. Lungs shape during breathing
The breathing lab first has a setup with placing the respiratory belt transducer
around the volunteer’s waist above the naval as seen in Fig 1. Once the equipment
is all hooked up, Lab tutor asks to monitor the normal breathing rate of the
volunteer, this of course is to have a basis for comparison after altering factors.
Measurements are in BPM (breaths per minute) and Breathing (mV). Once the
volunteer appears to be breathing normally, they are asked to inhale as much as
possible and hold their breath for as long as they can without discomfort. This is
repeated but with the volunteer exhaling than holding their breath. That is one
exercise of this lab.
Next exercise is to monitor hyperventilation. The volunteer is asked to inhale and
hold breath for as long as possible. Once breathing normally again volunteer begin
hyperventilating for 30 seconds, then return to normal respiration for 2-3 minutes.
After that time volunteer hyperventilates again for 30 seconds, than holds breath.
Third exercise is to monitor effects of rebreathing exhaled air. This exercise
requires a small bag to place over the volunteer’s mouth and nose. Volunteer
breathes normally for 2-3 minutes, than places the bag over the mouth and nose.
Volunteer rebreathes air for 30 seconds, then removes bag and continue monitoring
breathing for 60 seconds.
Last exercise is to monitor the effects of the volunteers pulse while breathing. The
finger pulse transducer is brought in for this last part of the experiment. This
exercise shows the effects of the human pulse while holding their breath.
The lab report portion asks various study questions to get the user thinking of why
certain graphs appear the way they do at the end.
• Rebreathing from a closed bag results in arterial hypercapnia (raised partial
pressure of carbon dioxide), which stimulates respiration. How was this
evident in this exercise? (That is, did the depth or rate or both increase
during rebreathing compared to normal breathing?)
• When could hyperventilation provide a significant advantage? (Athletic
performance, for instance? If so, how?)
Learning objectives for this lab
• Use a sphygmomanometer and stethoscope to measure human arterial blood
• Determine systolic blood pressure using a sphygmomanometer and detection
of a peripheral pulse
• Demonstrate how measurement position affects the magnitude of the arterial
Fig 3 Sphygmomanometer setup Fig 4 Finger pulse transducer setup
In this experiment students will be working with sphygmomanometers as seen in
Fig 3. also stethoscopes. Students will learn to listen for Korotkoff sounds when
taking blood pressure on each other.
The first exercise is to take blood pressure the traditional way with
sphygmomanometer and stethoscope. This can prove difficult for those have never
done this before, but is also beneficial at the end of the day. Lab tutor gives a brief
explanation on how to take blood pressure using this equipment.
The second exercise the stethoscope is replaced with the cardiomicrophone
transducer. The sphygmomanometer is plugged into the PowerLab, the
measurements are in mmHg for the pressure and mV for the cardiomicrophone.
The graphs display the Korotkoff sounds as to demonstrate where to read the
systolic pressure and diastolic pressure.
Third exercise the finger pulse transducer is attached to the same arm as the
sphygmomanometer. This exercise will monitor the effects of peripheral pulse while
taking blood pressure. This method only allows users to measure the systolic
The last exercise is measuring hydrostatic effect. The volunteer is asked to raise
the hand (with the finger transducer and cuff) above their head, lower and keep it
level to their heart. The graph will display which arm position has the greater
effect on systolic pressure.
Lab report asks the user questions that seem to sell the PowerLab more than
analyze data received.
• Comment on how the systolic pressure determined by auscultation and by
pulse detection compare for each of the subjects in your group.
• From your results, do you think that pulse measurement can replace the
stethoscope in determining diastolic pressure?
ECG & HEART SOUNDS
Learning objectives for this lab
• Know where to place electrodes to record the standard limb lead ECG (leads
I, II and III )
• Be able to identify the major components of the ECG (P wave, QRS complex,
T wave) in these leads
• Be able to relate the electrical activity in the heart to these major
• Be able to provide estimates of the timings of the components of the ECG and
• Know how to calculate heart rate from the ECG
• Explain the time relationships between the electrical activity of the heart (as
recorded in the ECG) and the mechanical activity of the heart (as judged from
the heart sounds)
Fig 5. Typical ECG wave Fig 6. Apparatus for proper ECG reading
This lab requires electrode cream, as to be applied to the reusable clamp
electrodes. The push-button switch is also being used in this lab, with a
stethoscope to indicate when heart sounds are heard. Once clamps are plugged
in, it is best to find the best spot on the wrist for the strongest signal as seen in
Fig6. This can be time consuming.
First exercise is to observe the volunteers ECG at rest, so as to create a baseline
for later on in the experiment. This is when finding the best place for the
electrode clamps occurs. The user if not already familiar with what an ECG
looks like (Fig 5) can study the graph and ask questions if need be.
The second exercise is to record variation between people. This was not
performed during my research of the PowerLab. This exercise would have
students study and recognize where variation will occur on ECG’s from person to
Third exercise requires the stethoscope and push-button plugged into the
PowerLab. This exercise allows students to listen for the heart sounds, once the
lub is heard the button is pressed and held, then released upon hearing the dub.
This can be difficult as human intuition is to predict when the lub and dub will
occur, thus influencing the results. The push-button has its own graph to match
up with the ECG graph, to observe when the lub was heard as to where and
when it appears on the ECG.
The last exercise is to replace the push-button and stethoscope with the
cardiomicrophone. This exercise is very similar to the previous one, as all that
has changed is now the PowerLab does all the reading for you. Once again this
is a selling point for the PowerLab itself.
The lab report portion once again asks question based information received and
how it was received. This lab report ask questions similar to the blood pressure
lab, is the manual way better than the digital way?
• The P wave and the QRS complex represent depolarization of the atrial
and ventricular muscle respectively. Why does the QRS complex have the
• Your "lub-dub" recordings probably show some differences from the
correct timing of the heart sounds as judged by phonocardiography. How
can you account for this difference?
ECG & PERIPHERAL CIRCULATION
Learning objective for this lab
• Measure the ECG and pulse at rest
• Analyze the resultant signals, and look at the variations
• Palpate the radial, ulnar and brachial pulses
• Show that the arterial blood supply to the fingers derives from both radial
and ulnar arteries by way of anastomoses
• Measure the effect of cold on the amplitude of the finger pulse
Fig 7. Circulation of hand Fig 8. Circulation of heart
This lab requires the reusable electrode clamps, as seen in the heart sounds lab; as
well as the finger pulse transducer. The volunteer will palpate the ulnar pulse, and
brachial pulse to observe these effects, as the finger pulse transducer measures the
readings. Students will have to be knowledgeable as to the whereabouts of arteries
in their arms Fig 7 gives a brief interpretation as to the location of arteries. Later
the experiment will require some ice water, as to observe the effects of cold on
First experiment is similar to the other labs, create a control measurement first.
Finger pulse and ECG are measured in mV. The volunteer must sit very still as to
not cause any artefacts. There is the option to make readings on other volunteers
Second Experiment is just measuring variation of finger pulse in other people. This
is to measure the amplitude and interval of the pulse for each student and compare
the different times. There was not much for variation considering the
Third exercise is to get students familiar with the location of the brachial artery and
ulnar artery. Students will also learn that to use the first three fingers and not
their thumb when checking pulse in arteries.
Fourth exercise will have the finger pulse transducer attached to the distal portion
of their middle finger, than apply firm pressure to the radial, ulnar, and brachial
arteries. This exercise demonstrates anastomoses, and how applying pressure to
higher arteries can affect their pulse, as well which artery can change the pulse
greatest. This exercise still depends on whether students are able to find the
arteries and apply proper pressure, given the size difference in some students.
Fifth exercise will measure the effects cold has on the pulse in fingers. With the
finger pulse transducer, a normal temperature measurement is taken, than the
volunteer will immerse their hand in ice water for approximately 30 seconds or
before discomfort. After cooling the fingers replace the finger pulse transducer and
take a measurement of the hand warming itself. Students observe how the pulse is
affected when blood is returning with proper circulation.
Lab report is more focused on asking how blood circulation is affected by pressure
and climate change. There are also medical questions in regards to first-aid
(haemorrhaging) and proper assessment of the pulse, this lab seems most applicable
to the 3302 course.
• When you feel a pulse, do you feel (a) the blood flow, (b) the pressure wave, or
(c) brief changes in diameter of the artery due to the pressure wave?
• Did the pulse disappear completely when the radial or ulnar artery alone was
compressed? If not, why not?
• Anatomical sites where a pulse can be palpated often correspond to 'pressure
points' for stopping hemorrhage in first-aid treatment. Why?
Learning objectives for this lab
• Demonstrate the effects of electrical stimuli using the nerves of the forearm
• Record and measure the muscular twitch response to nerve stimulation, and
show recruitment in the twitch response as the stimulus strength increases
• Measure the effects of changing the interval between paired stimulus pulses
and observe a short tetanic contraction
• Calibrate a hand dynamometer with respect to a volunteer's maximal grip
• Measure the decline in maximal force during a sustained contraction, and
examine some properties of muscular fatigue
Fig 9. Apparatus of lab Fig 10. Contraction and extension of muscle
This lab involves stimulating muscles in the wrist to cause a muscle twitch in your
thumb. Electrode and electrode cream will be required, as well the finger pulse
transducer as seen in Fig 9. The lab will not allow the stimulation to go above an
unsafe setting. This lab helps to have a volunteer that is willing to be subjected to
electrical stimulation, and high pulse frequency electrical stimulation, since
objective is to observe summation and tetanus of muscle twitches.
First exercise consists of finding the best location to place the electrode for the rest
of the experiment. The electrode cream also needs to be wiped off the skin after each
new test location the wrist; this is to prevent short circuiting. Students are to
observe the motor sensory stimulation of their thumb and fingers.
Second exercise the volunteer should have their hand set up as the apparatus seen
in Fig 9. The finger pulse transducer needs to be fixed in position. The finger pulse
transducer will be measuring the force generated by the thumb when stimulated by
the electrode. The electrode will stimulate and record for 0.5 seconds. The user will
increase the mA one unit at a time until the volunteer feels discomfort. The
maximum mA will be used in the next exercise.
Third exercise will cause multiple stimulation to the wrist in a fixed time frame of
1000 ms. The time will decrease after each trial eg. 1000, 500, 200, 100, 50 ms. As
the time decreases the stimulation will cause the thumb to generate a larger force
on the pulse transducer. The number of stimulations in a time frame can also be
increased in this exercise, but as the time frame decreases the number of pulses
Fourth exercise measure tetanic muscle twitches. The user will increase the number
of pulse stimulation to the wrist in a given time frame, 50 ms. This will cause the
thumb to generate a large twitch due to the stimulation summing yet the muscle
receives the stimulation as a large stimulation.
I. DIGITAL READ-OUT I. LAPTOPS
• Lab tutor and Chart both • Students would be
receive and display data required to have laptops,
digitally, which leads to as well have software
less human error when installed. This CON
graphing and collecting would be costly if done on
data. lab time. Student laptops
would have to meet the
II. KNOWLEDGE OF READING efficiency requirement for
GRAPHS software and hardware.
• Students will learn how
to properly read graphs II. CALIBRATION
obtained from • If a lab were designed
experiments from Lab using the Chart software,
tutor or designed labs on the machine would have
Chart. Such graphs to be calibrated to
include ECG, EMG, EEG. students, this definitely
causes a problem when
III. INTRODUCTION TO NEW using the
• Students can become
familiar with such III. LAB TUTOR
equipment as • This software program is
sphygmomanometer, has many labs, but most
stethoscopes, and the are not pertinent to the
PowerLab 26T. The 3302 course.
students will be able to • The lab analysis portions
practice taking blood are limited in educational
pressure and checking payoff.
heart rate on each other.
IV. SAMPLE SPEED
• The PowerLab is able to
take samples at an
incredible rate of 100,000
per second per channel. IV. UNIT CONVERSION
This results in a much • Chart requires either
more accurate method for professor or student to
obtaining results during know how to convert the
labs. default volt measurement
to preferred units ie.
V. CHART MANIPULATION mmHg, CO2, Newton, etc.
• Chart allows users to
manipulate obtained data V. PROPER USE OF
such to integrate the EQUIPMENT
graphs to observe • When measuring heart
patterns. Another rate and checking for
method is the Fourier heart beat, stethoscopes,
Transformation, allowing and sphygmomanometer
visual aid of peak times are required. This
during gathering of data. introduces problems if
• Graphs can also be students have not had
transported to Microsoft experience with said
excel, allowing for further devices.
manipulation. • Muscle electrodes; if used
incorrectly may cause
Lab tutor and Chart both
will only allow certain
frequency, and max
The PowerLab 26T can be very beneficial to a course such as 3302, but there are
many factors to take into consideration. Such factors as mentioned in the PROS &
CONS, is that students will need to have laptops that can handle the software, and
each student needs to bring their laptop to class. A solution is that the university
updates the portable computers as to meet the requirements for the PowerLab.
Than there is the matter of Chart program, that program is a fountain of
possibilities for labs; but requires someone to become very proficient with the
program. The manual that comes with Chart specifies that most of the information
gathered can be transferred onto MS excel, and the MAC equivalent. Large benefits
of this equipment is practicing lecture material, and learning exactly how
physiology works. PowerLab is probably best for small classes, since the university
would need numerous PowerLab’s and students need to have the software to
operate the hardware.
PowerLab can have labs designed specifically for certain courses, given that the
professor or T.A.’s are familiar with the equipment and software. After going
through the labs on Lab Tutor the ECG & Peripheral Circulation seemed to be best
for the 3302 course without altering the lab. Here is a lab proposal that explores a
bigger possibility for working with muscle twitches.
MUSCLE LAB PROPOSAL
Understand muscle twitch variations from left and right hand, and other students.
Understand how heart rate can play a factor on muscle twitch.
Understand tetanic, and summation muscle twitches.
Equipment used will be the electrode stimulator, pulse transducer, and PowerLab
Students will attach the electrode stimulator to their wrist, and place the finger
pulse on a flat surface as to read twitches from their thumb.
Through Chart, electrode stimulation ranges from 5mV to 20 mV, and at various
stimulation pulse intervals.
Change wrists, than change students, and increase heart rate.
Graphs obtained from Chart can be transferred to MS Excel.
Students will remark on differences on tetanic and summation muscle twitches,
which causes a greater force?
Is there a significant difference between left and right hand twitch, which hand
causes the greater force?
Does heart rate effect muscle twitches, w.r.t. tetanic, summation?
AdInstruments PowerLab 26T has a lot to offer for a course designed for examining
physiological aspects of the human body. Student can understand how to read
graphs from ECG, EMG, and spirometer read-outs, and apply lecture material to
these graphs. There are a few down sides to the PowerLab 26T, as mentioned in the
PROS & CONS section. Every student will need to have the software, and a
working laptop with enough space to hold all labs. Each Lab can take up to as
much space as 2 GB. The digital readings allow for continuous data retrieval,
which reduces minor human error when doing some measurements with older
equipment. If a professor is quite proficient and knowledgeable with both Chart
and Lab Tutor, there are endless possibilities for labs, given that there may be a
course dedicated to purely labs of medical biophysics. The program Lab Tutor gives
a great introduction to the capabilities of the PowerLab 26T, as it will walk
individuals through certain aspects eg: calibrating the machine, adjusting graphs
etc. A novelty that seemed to be inputted into the Lab Tutor program is the
program seems to “Sell itself”. The lab reports ask question in regards to which is
better checking blood pressure with a caridomicrophone or a stethoscope. After all is
said and done the PowerLab is a valuable asset