.NonInvasive
Blood Pressure Overview- A must read if one is about to have a study where
blood pressure on a mouse or rat will be tested and the data supplied
must be accurate, reliable and reproducible at low temperature.
No false claims from IITC
Life Science just the facts for 35 years.
*IITC Life Science is the ONLY validated method when compared to Telemetry *
IITC Life Science Instruments now in it's
35th year. We are a company that is dedicated to improving the Life Sciences
field by supplying the best possible equipment and service to you the
researcher. We continue to improve our line of NonInvasive Blood Pressure
testing equipment on mice, rats, cats, dogs, swine and monkeys via the
tail along with our Analgesia line and rat and mouse indwelling catheters.
In addition, we carry an extensive line of other research equipment; Small
Animal Ventilators, Syringe Pumps, Restrainers.
To current or future users of Non-Invasive Blood Pressure on a mouse or
rat (NIBP).
It is known Non-invasive Blood Pressure
(NIBP) testing by tail plethysmography needs elevated ambient temperature.
The effect of higher ambient temperature on rodents’ blood pressure
is also well established in literature. Rats and mice regulate their body
temperatures by controlling the amount of blood that flows through their
tails. When body temperatures are elevated above normal; either by elevated
ambient temperatures or exercise; the flow of blood to the tail increases
dissipating the extra heat. The higher the body temperature the more blood
flow. It has been found; heating rats to 32 degrees Celsius and above
or heating mice to 34 degrees Celsius and above causes thermostress, the
loss of animals is common due to high temperature. The result of this
is a modified blood pressure, (modification can be as much as +/-12-28
mmHg), and a lot of open questions that are still unanswered (for example
the effect of elevated ambient temperature on constant vasoconstriction).
The form of pulse detection is critical and sensor selection determines
the method. Due to its simplicity the piezoelectric sensors enjoyed widespread
use over the years. When an external physical force is applied to piezoelectric
sensors the drum like action generates electrical signals.. Piezoelectric
crystals are widely used in inexpensive microphones and touch switches.
There are inherent problems and drawbacks to the use of these crystals
for pulse detection:
When measuring blood pressure in rodents these crystals need a temperature
significantly higher (36 to 40 deg C) than the thermostress level in order
to detect pulses. These facts have been published decades ago. In addition
the heating of the tail only is based on the mistaken assumption that
the tail pulsation is the result of local heating
This happy boiling of the animals has gone on for decades, the only forward
was when IITC introduced the photoelectric sensor in 1978. IITCs sensors
use light and photo sensors for pulse detection. When blood flows throughout
the tail, the diameter of the tail changes and in turn the amount of light
that reaches the photocell changes. IITCs one-piece design (sensing electronics
and occluding cuff) does not mechanically load the animal's tail and eliminates
exact sensor placement as is needed using other equipment.
The main advantage is: The photoelectric sensor can detect pulsation at
close to room temperature without stressing the animals! As a matter of
fact, numerous papers have been published with the use of the IITC instruments,
stating temperatures as low as 28 degrees Celsius for mice and even lower
for rats! The high reliability of these sensors and the associated electronic
gear allow IITC to back these products up with an Unconditional Lifetime
Warranty, a product backup still unparalleled in the Experimental Biology
field worldwide.
For those who are still pursuing the use of the piezoelectric sensors:
You do not need an instrument to measure systolic blood pressure in rats,
all you need is a cuff, pressure gauge and an inflating bulb. Heat the
animal to 40 degrees Celsius then occlude blood flow and place your finger
on the distal ventral side of the tail, slowly deflate and you will start
to feel the pulsation of the poor rat laboring under the heat Companies
who produce piezoelectric gear for NIBP are quite numerous. The heat goes
on! Imagine the tail has to beat this piezoelectric drum to produce a
pulse so hard that you can feel it with your hand.
We at IITC are proud to have contributed to the state of the art by our
NIBP method and regard the piezoelectric sensors as an inferior non-humane
way of testing blood pressure in rodents.
These papers are just a few of the large family of published reports over
our 31 years in existence using the NIBP methods. Although we encourage
the use of low ambient temperature, it is amazing that published reports
with IITC units are using even lower than suggested temperatures. Our
method is the Gold Standard.
Literature References:
1. Salt Sensitive Hypertension and Reduced
Fertility in Mice Lacking the Prostaglandin EP2 Receptor. Christopher
R.J. Kennedy, Yahua Zhang, Suzanne Brandon, Youfei Guan, Keith Coffee,
Colin D. Funk, Mark A. Magnuson, John A. Oates, Matthew D. Breyer and
Richard M. Breyer. Nature
Medicine, Vol. 5, No.2 Pg. 217-220.
Mice tested at 28 degrees Celsius with the IITC Model 179 Apollo Amplifier.
2. Relationship between cardiovascular Hypertrophy and cardiac baroflex
function in spontanious hypertensive and stroke prone rats. Naoyoshi Minami
and Geoffrey A. Head, Journal of Hypertension,1993 Vol. 11 No. 5, page
523-533 Rats tested at 28 degrees
Celsius with the IITC Multi-Channel test system.
3. Tail Cuff BP Measurement without external preheating in awake rats,
R. Bunag et. Al., Hypertension Vol.4, No.6, Nov-Dec. 1982, pg. 898-902
4. Elevation of Systolic BP of Spontaneous Hypertensive Rats by heating,
T.T. Yen et. Al., The Pharmacologist, Col. 19, Pg. 212, 1977, Abstract
481
5. Effect of Heating on body Temperature (BT), Direct Aortic BP &
Indirect Tail BP (DABP & ITBP) In Wystar Kyoto (WKY) and Okamoto Aoki
(SHR) Rats, Phyllis Schaller and the Upjohn Company, Kalamazoo, MI ASPET
1980
6. COMPARISON OF SIMULTANEOUS MEASUREMENT OF MOUSE SYSTOLIC ARTERIAL BLOOD
PRESSURE BY RADIOTE- RADIOTELEMETRY LEMETRY AND TAIL-CUFF METHODS Steven
E. Whitesalla, Janet B. Hoffa, Alan P.
Vollmerd, Louis G. D’Alecy Am J Physiol Heart Circ Physiol, Feb
2004; 10.1152 ajpheart.01089.2003
7. Cellular Mechanisms of Insulin resistance in Rats With Fructose-Induced
hypertension. Cristiana Catena, Gilberta Giacchetti, Marileda Novello,
Gianluca colussi, alessandro Cavarape, and Leonardo A. Sechi AJH 2003;
16:973-978
8. Cardiovacular, antihyperlipidemic and antioxidant effects of oleanolic
and ursolic acids
in experimental hypertension. Somova L, Nadar A, Rammanan P, Shode FO.
Phytomedicine. 2003 Mar;10(2-3):115-21 PMID:12725563 [PubMed - indexed
for
MEDLINE] NOTE: Harlan Sprague Dawley rats are quality tested with the
IITC Noninvasive Blood Pressure method.
WHY IS THE IITC INDIRECT BLOOD
PRESSURE SYSTEM BETTER THAN OTHERS?
Comparison is to other high temperature methods out on the market today
1. Ambient temperature for testing: (Heating)
Rats as do other animals have a built-in regulating mechanism; It is called
thermoregulation. Their normal ambient temperature is approximately 26-27
Deg.C. It is at 28-30 Deg.C. the thermoregulation starts an increased
blood-flow; If the normal ambient temperature is exceeded for mice. As
a result, the rodent pumps more blood into its tail, thereby trying to
cool itself off, since the tail is the only body part not covered by fur
and able to lose heat faster. This mechanism is used in indirect blood
pressure testing.
The big difference is the pulse detection. The tail exhibits small pulses
at even 26 Deg.C. or less, When the pulse detector is not sensitive enough
one must has to go to higher temperatures.
Why is this bad?
For rats as well as for mice there is a temperature limit after which
the blood pressure is getting modified. Modified is the key word. It may
go higher or lower on the same animal daily. Deviations will therefore
go either plus or minus. The temperature limit is 32 Deg.C. for rats and
34 Deg.C. for mice.
If the ambient temperature is kept under
these limits the test results will be uniformly close and within five
to seven mmHg from the blood pressure values obtained by direct cannulation
from arteries.
The IITC method tests at 32 Deg.C. on
rats and at 34 Deg.C. on mice. The ambient temperature for other methods
is at 38-40 Deg.C. this should never be done to a rat. They do not mention
this, they simply advise to heat the rat to 36-40 Deg.C. and then shut
off their heating pads, metal plates covered by plastic and air heaters so they do not heat.
The excessive heating changes the BP reading
dramatically by + -12-28 mmHg. This could be a window of 56 mmHg day to
day!
What does this mean?
This means that the high temperature methods also measure BP, but huge
deviations and the animals are lost periodically due to heat shock. This
can be a costly mishap. In essays three animals per dosage on average
are used. Two of three readings should be usable. If the two animals from
the same dosage are lost, the whole essay is not acceptable. To do this
twice is quite an expense.
2. Animal Holders and sensors:
The IITC animal holders are made with matching sensors to cover an expansive
weight range of 25-1000 gr. We also offer large sensors that enable the
test of dogs, cats, swine and monkeys.
The least sensitive are the piezoelectric
sensors. These detectors require the highest temperature 38 deg. C. At
high temperatures the animal labors, its parameters change and may even
cause death.
The piezoelectric detectors require high
heat (36-38 Degrees Celsius), which in turn causes high stress on the
animal. At this temperature you do not even need equipment to detect a
pulse since you can feel it with bare fingers on the low central side
of the tail as the pulse occurs.
The IITC sensors have a specially designed
photoelectric detector, which allows the low temperature testing.
3. System Design:
A user can buy a single channel system and expand it into a multi-channel
system without having to discard any of the existing equipment they purchased
previously. When it comes to versatility IITC’s line is unsurpassed.
All IITC units have an analog output.
Starting with the Model 29-SSP single channel system and the Model 229
single channel system with built-in pump. They both can be used with a
single or dual channel recorder. This is unique since all other makes
can only use a dual channel chart recorder; this means a savings for the
end user.
4. Technical Support and Warranty:
IITC offers unlimited advice and help before and after the purchase. Users
can fax us their recordings, which will enable us to lead them to a perfect
recording. It is as if we are in the laboratory with them.
We offer an Unlimited Lifetime Warranty on our entire line of NIBP products that we manufacture.
5. Literature and Customer Circle: Supplied upon request.
