62. Tonometry

yaboiemil's version from 2016-02-02 17:05


1. Tonometry is the measurement of pressure (P=F/A)
2. Electromechanical Transducers transform pressure into electrical quantities.
3. Piezoelectric transducers rely on a piezoelectric crystal to work. External pressures
on a piezoelectric crystal result in a shift of ion electric charges which manifest as
an electric voltage across the crystal. This voltage is directly proportional to the
4. Piezoelectric Transducers can me miniaturized to tenths of a milimeter.
5. The piezoelectric effect can also be reversed... if a voltage is applied to the
crystal, the crystal can be made to deform by a certain amount. This can be used
to create ultrasound.
6. Systolic pressure is the maximum pressure, Diastolic the resting mean pressure.

Methods of measuring Blood Pressure:


Question Answer
DirectInsertion of a thin, flexible catheter into a vessel.
IndirectThe Riva-rocci method
Riva-rocci methodShut off blood flow to the arm. Slowly ease pressure, listen for Korotkoff Sounds.
Korotkoff's SoundsThe sounds that blood makes when it floods into a vessel.


7. The first sound to be heard indicates the Systolic Blood Pressure.
8. This will slowly get louder as Diastolic blood pressure sounds join in. It is at its loudest
at mean arterial pressure.
9. A cuff can be kept on all day, monitoring at intervals to monitor blood pressure
throughout the day. This is recorded on a small machine, which can then be
later analysed by a doctor.This is HOLTER MONITORING.
10. Intraocular pressure can be measured using a Schiotz Tonometer. An application rod is
applied to a desensitized area of the cornea at a SET PRESSURE. The deformation of the
eye is then measured, indirectly measuring the pressure in the eye.