Lung Testing B Flashcards
Nitrogen washout: A method to measure ___.
FRC
Functional Residual Capacity
In nitrogen washout, the patient breathes 100% oxygen for up to ___ minutes or until the N2% is less than ___ to “wash out” the nitrogen from the lungs. Exhaled gases are collected in a spirometer or bag and the final ___ is used to calculate the ___.
7 minutes
Less than 1%.
N2%
FRC
Nitrogen washout: a patient with normal lungs should wash out in ___ minutes or less. A patient with obstructive lung disease will take (shorter or longer).
3 minutes
Longer (than 7 minutes)
Nitrogen washout: when should “switch in” occur?
At the end of normal expiration.
Nitrogen washout: There are three lung values that are calculated. What are they?
FRC, RV, and TLC.
Nitrogen washout: breath by breath analysis is possible with a/an ___.
Rapid nitrogen analyzer.
Nitrogen washout: a ___ is not required in nitrogen washout because no rebreathing occurs.
CO2 reabsorber.
Nitrogen washout: If %N2 does not drop after several minutes, what should you suspect?
How much N2 is in the atmosphere?
Air leaking into the system.
Amount of nitrogen in room air: 79%
Nitrogen washout: If the O2 tank is less than ___, you should replace it.
50psi
Body Plethysmography: What is the definition of Thoracic Gas Volume (VTG)?
Volume of gas contained in the thorax measured at end expiration. Includes measurement of air trapped in thorax which is not in communication with airways.
Body Plethysmography: The VTG is usually equal to ___.
FRC
Body Plethysmography: How is the RV/TLC ratio calculated?
Divide residual volume by total lung capacity then multiply by 100.
What is the technique for doing a typical body plesthysmography?
- Patient breathes normally for several minutes.
- At end expiration, shutter closes and patient “pants”. No airflow is occurring.
- Mouth pressure approximates alveolar pressure when there is no airflow. (Pmouth = Palveolar)
- A second pressure transducer measures pressure in the box, which is equal to the volume of gas in the thorax. (Pbox = V tg)
Body Plethysmography: What law is used to calculate thoracic gas volume?
Boyle’s law
Body Plethysmography: On the oscilloscope, the vertical axis represents ___.
Mouth pressure