Jen's PFT Equipment final study tips SG (4/19)

Give some examples of volume measuring devices?

1. water seal

2. dry seal piston

3. turbine rotor

4. bellows

Pressure differential pneumotachometer. What law? What vent is it used in?

Aka pressure drop. Follows POISEUILLE law: diameter decreases → flow decreases → requires increased pressure, so it restricts flow. Because of this, if the flow is LAMINAR, restriction is fixed and the change is what’s measured. Utilizes a pressure transducer to measure pressure before and after restriction. Used in Hamilton

Heated wire flow sensor. What law it follows? What vent it’s used in?

Aka temperature drop. Follows KING’S law. How much energy applied to wire to keep constant temperature. If blowing on something hot, it has to increase energy to keep it hot. Uses heated element inside: flow increases = increased energy to heat element. Change in energy is translated by computer into flow information. Used in Draegar.

Pilot tube principle. What law it uses?

Bunch of holes blowing across to measure flow to relate to gas’s density and velocity. Follow’s BERNOULLI’S law. As air goes across the orifice, pressure decreases. Like the pneumotach with the honeycomb.

Ultrasonic flow sensor

Uses hertz through air, disrupting air to measure total flow. Doesn’t utilize any laws.

O2 analyzer. What electrode it uses?

Polarographic electrode, used in a blood gas. Uses an electrochemical process, where gas is drawn into a cell with a polarized, platinum electrode and the O2 is reduced based upon its partial REQUIRING A POWER SOURCE.

O2 analyzer and water in tubing.

If water is in the tube, air goes from increased surface area to decreased surface area back to increased surface area because of the water. This relates to a venturi system, with FiO2 changing based on SA. Less SA = More FiO2, More SA = Less FiO2. A wet circuit will also create a pressure change, affecting accurate FiO2.

Infrared gas analyzer

Some gasses absorb infrared radiation faster than others. This analyzer evaluates absorption rate of a reference gas vs the rate of the sample gas to determine concentration.

Spectroscopy. What gas does it analyze?

Based on principle of photo intensity, being a N2 ANALYZER.

Thermal conductivity. What gas does it analyze?

HE ANALYZER. Reads ZERO when calibrated to room air (need to calibrate it at a low and high point). Gasses differ ability to dissipate heat. Circuit at a higher temp have more resistance to current at a lower temp.

gas chromatography. what test is it used in?

Can measure MULTIPLE GASSES. Takes in gas and the ones that leave first, weight the lightest, with the inverse being true. Used for DLCO due to it “competing” with tracer gases. Separates the gas based off of weight.

Interferences in analyzer

REMOVE water vapor (pass through silica gel or calcium sulfate) + CO2 (pass gas sample through ganules of hydroxide).

Nation tubing is highly selective, semi-permeable membrane to water vapor, meaning it doesn’t collect water like large Bohr tubing does. If tubing is more wet than gas, tubing dries, if tubing is less wet than gas, humidity will occur.

O2 polargraphic electrode

Principle: polarographic (more O2 = more electrons), interference = pressure changes and H2O

O2 zirconium fuel cell

Pirnciple: voltage, interference = pressure changes and H2O

CO2 and CO

technollogy: infared
principle: radiation
no interferences.

N2

technology: spectroscopy
principle: photo intensity

He

technology: thermal conductivity
principle: heat

multiple gases

technology: gas chromatography
principle: weight

NO technology, principle and interference

technology: chemoluminesence
principle: light
interference: H2O, CO2