1. is a device for recording velocity and force of chest movements during respiration.
   1. It is mainly used in neonatal respiration monitors.
2. pneumographic devices(based on principles of operation).
   1. a flexible rubber vessel is attached to the chest and the vessel is equipped with sensors
      1. a very thin tube filled with mercury is stretched across the patient's chest
   2. impedance based.
      1. it is implemented by either using two electrodes or Four electrodes
      2. is to measure changes in the electrical Impedance of the person 's thorax caused by respiration or breathing
3. Impedance Pneumograph
   1. The idea behind the Impedance pneumograph is that
      1. the AC impedance across the chest of a subject changes as respiration occurs.
   2. The Resp1 is a self balancing, stand-alone signal conditioner which converts changes in Thoracic impedance resulting from respiration, into a high-level respiration signal.
   3. A front panel meter shows respiration activity for easy checkout. Battery (9V) powered for field use.
   4. Problem
      1. is that they are most useful if they are standardized to some known volume.
      2. So, typically a calibration curve must be made by having the subject breathe in or out several known volumes both above and below the FRC and then construct a calibration curve.
      3. This usually requires the use of a spirometer
   5. Respiration Rate & Depth
   6. Strain gauge pneumograph
      1. Elastic belt
      2. Stiff leaf spring
      3. Strain gauges
      4. Wheatstone bridge
4. Inductance plethysmography
   1. Basic principle:
      1. This uses a pair of wires, each attached in a zig-zag pattern to a highly compliant belt
         1. (one belt is placed around the ribcage, the other around the abdomen).
         2. Each wire forms a single loop, which is excited by a low-level radio-frequency signal.
      2. Changes in cross-sectional area result in changes in self inductance, which can be measured
         1. (after demodulation).
      3. The output is proportional to the local cross-sectional area encircled by the loop.
   2. The change in resistivity of the lungs with inspiration and expiration can be measured
      1. by injecting a small high-frequency current across the chest and measuring the resulting voltage
         1. The change in voltage during the breathing cycle, ΔV, is proportional to the change in electrical impedance of the chest, ΔZ, since ΔZ = ΔV / I, where I is the high-frequency (of constant amplitude) current.
5. two types of pneumograph
   1. Mercury strain gauge
      1. Same wire foil or piezoresistive semiconductor devices
   2. Thermistors
      1. are used as flow detectors in some pneumographs'
      2. 1- a bed thermistor is placed just inside the patient's nostril
      3. 2- thermistors are mounted on a patient who is fitted with an endotracheal tube or is on a respirator o ventilator
   3. In some transducers, the thermistor is placed with a thin platinum wire stretched taut across a short section of tubing
6. Advantage of Impedance PG
   1. they are easy to obtain, and they accurately reflect instantaneous changes in breathing.
   2. They can be fed directly into a computer and analyzed.
7. Measuring Minute Volumes and Breathing Rates
   1. The impedance pneumograph
      1. is a device that utilizes impedance changes that occur in a person's chest during breathing.
   2. These changes are linear as the person's chest size changes during breathing.
   3. The device applies a very small, constant rms.
   4. If the impedance changes the electrical energy
      1. that is able to be transmitted through the person's chest changes with the impedance.
      2. Thus, the changes in electrical current accurately reflect chest volume with respect to time.
8. Choice of frequency for Electrical Impedance Plethysmography
   1. AdequateSNR requires a current of about 1Am
   2. At low frequencies
      1. a 1mA current causes an unpleasant shock
      2. electrode contact impedance can be high
   3. At frequencies above 100 kHz, stray capacitance makes the design of the circuitry difficult
   4. A frequency between 20 kHz and 100 kHz is usually chosen
9. measure of electrical impedance
   1. The simplest method is to use a two-electrode System
      1. same electrodes for current injection and voltage measurement
   2. Two electrode systems
      1. The movement of the thorax with breathing
         1. will cause changes in electrode contact impedance
      2. This artefactual change in 2 will be superimposed on the desired quantity
         1. (change in 2 due to change in lung resistivity)
   3. Four electrodes system
      1. The a current flows through two outer electrodes and voltage
         1. is sensed between tow inner electrodes
      2. If the voltage sensing amplifier has an infinite input impedance
         1. the errors caused by the changes in electrode contact impedance are eliminated
10. Electrical Impedance Plethysmography Conclusions
    1. Advantage
       1. Simple to use, non-invasive
    2. Disadvantage
       1. Not sufficiently accurate to quantify volume change
       2. Often used simply to extract breathing rate (Impedance Pneumography), in which case two-electrode method is adequate