4430 Exam 2 Material: Lung Volumes, Capacities & Measurement

What are the 4 lung volumes?

- VT

- IRV

- ERV

- RV

What are the 4 lung capacities?

- TLC

- VC

- IC

- FRC

What does VT stand for?

Tidal volume

What is tidal volume (VT)?

The amount of air inhaled or exhaled during a normal breath

What does IRV stand for?

Inspiratory reserve volume

What is inspiratory reserve volume (IRV)?

The amount of air that can be inhaled above and beyond a normal inspiration

What does ERV stand for?

Expiratory reserve volume

What is expiratory reserve volume (ERV)?

The amount of air that can be exhaled beyond a normal expiration

What does RV stand for?

Residual volume

What is residual volume (RV)?

The amount of air remaining in the lungs after a maximal exhalation

Why does residual volume remain in the lungs?

It prevents the lungs from completely deflating

What is a lung capacity?

A combination of 2 or more lung volumes

What does TLC stand for?

Total lung capacity

What is total lung capacity (TLC)?

The total amount of air contained in the lungs

What volumes make up TLC?

- IRV

- VT

- ERV

- RV

What does VC stand for?

Vital capacity

What is vital capacity (VC)?

The amount of air moved between maximal inhalation and maximal exhalation

What volumes make up VC?

- IRV

- VT

- ERV

What does IC stand for?

Inspiratory capacity

What is inspiratory capacity (IC)?

The amount of air that can be inhaled starting after a normal exhalation

What volumes make up IC?

- VT

- IRV

What does FRC stand for?

Functional residual capacity

What is functional residual capacity (FRC)?

The amount of air remaining in the lungs after a normal exhalation

What volumes make up FRC?

- ERV

- RV

What is the equation for TLC using FRC and IC?

TLC = FRC + IC

What is the standardized ATS method for calculating TLC according to the lecture?

FRC + IC

What is another way to calculate TLC?

RV + VC

How can RV be calculated using TLC and VC?

RV = TLC - VC

How can RV be calculated using FRC and ERV?

RV = FRC - ERV

How can FRC be calculated?

FRC = ERV + RV

How can VC be calculated?

VC = IRV + VT + ERV

How can IC be calculated?

IC = VT + IRV

What does TGV stand for?

Thoracic gas volume

What is thoracic gas volume (TGV)?

The absolute volume of gas in the thorax at any point in time and at any level of alveolar pressure

When is TGV measured for lung-volume testing?

At end expiration

When TGV is measured at end expiration, what is it equal to?

FRC

What terms may be used synonymously?

- TGV

- VTG

- FRC

What equation might appear on a report using TGV?

TGV + IC = TLC

Do we need to memorize the average numerical lung volumes of a normal 20-year-old male?

No

Which lung volume is diagnostic and increases with emphysema/COPD?

RV

What happens to RV in obstructive disease?

Increases

Why does RV increase in obstructive disease?

Air trapping

What happens to RV in restrictive disease?

Decreases

What happens to TLC in restrictive disease?

Decreases

What happens to TLC in obstructive disease?

Increases

What happens to FRC in obstructive disease?

Increases due to hyperinflation

What happens to FRC in restrictive disease?

Decreases

What happens to VC in restrictive disease?

Decreases

What can happen to VC in obstructive disease?

It is usually decreased but can vary

Are IRV and ERV diagnostic by themselves?

No

What can happen to IRV and ERV in obstruction or restriction?

They can be decreased in either

Is IC diagnostic by itself?

No

What can happen to IC in obstruction or restriction?

It can decrease in either

What is IC clinically useful for?

Setting goals for incentive spirometry

Which measurements are especially useful for identifying obstruction-related air trapping and hyperinflation?

RV - FRC - TLC

What does an increased FRC indicate?

Hyperinflation

What does an increased RV indicate?

Air trapping

What FRC percent predicted begins to indicate hyperinflation in this course?

Greater than 120% predicted

What RV percent predicted begins to indicate air trapping in this course?

Greater than 120% predicted

What TLC finding supports restrictive impairment?

Decreased TLC

What is LLN?

Lower limit of normal

What is ULN?

Upper limit of normal

What are the restriction severity ranges given in lecture?

80-100% normal - 70-79% mild - 60-69% moderate - 50-59% moderately severe - 35-49% severe - less than 35% very severe

What are the 3 methods discussed for measuring lung volumes?

Multiple-breath nitrogen washout - multiple-breath helium dilution - body plethysmography

Which lung-volume measurement technique is the gold standard?

Body plethysmography

Which technique is used at Ohio State if needed but is less accurate than body plethysmography?

Multiple-breath nitrogen washout

Is nitrogen washout an open or closed circuit?

Open circuit

What gas does the patient breathe during nitrogen washout?

100% oxygen

What is the purpose of 100% oxygen during nitrogen washout?

To wash nitrogen out of the lungs

What does the analyzer measure during nitrogen washout?

Nitrogen concentration breath by breath

Approximately when is nitrogen washout complete?

When nitrogen concentration falls to around 1% to 1.5%

What should a normal nitrogen washout tracing look like?

A smooth and steadily decreasing pattern

What happens if room air leaks into the circuit during nitrogen washout?

Nitrogen concentration rises and the test becomes inaccurate

How many satisfactory nitrogen washout tests did the instructor say may be sufficient if the test correlates well with spirometry?

One

What do newer standards recommend for nitrogen washout?

Two tests

How long should you wait before repeating nitrogen washout?

At least 15 minutes

How closely should repeated nitrogen washout tests agree?

Within 10%

How long should a healthy subject usually take to wash out nitrogen?

About 1-3 minutes

What should you do if nitrogen washout has not occurred by about 7 minutes?

Stop the test and report that washout did not occur

Which patients commonly have prolonged nitrogen washout?

Patients with obstruction and large residual volumes

What equipment must be checked before nitrogen washout?

Calibration - oxygen supply

How much oxygen should be available before beginning nitrogen washout?

More than half a tank according to the instructor

What is the patient position for nitrogen washout?

Sitting upright

What must be placed on the patient's nose during nitrogen washout?

Nose clips

When is the patient switched to 100% oxygen during nitrogen washout?

At the end of a normal expiration

What maneuver is performed at the end of nitrogen washout?

Slow vital capacity

Is helium dilution an open or closed circuit?

Closed circuit

Why must helium dilution use a closed circuit?

Room air entering the system would alter the gas concentration and invalidate the test

What happens during helium dilution?

The patient rebreathe a known helium-air mixture until helium equilibrates between the system and the lungs

Approximately how long does helium equilibration take?

About 3 minutes

Why are CO2 and moisture absorbers needed in helium dilution?

Because the patient is rebreathing from a closed circuit

Why may oxygen need to be added during helium dilution?

To maintain approximately 21% oxygen as helium dilutes the gas mixture

When is helium dilution considered equilibrated?

When helium readings change by less than 0.02%

What is the maximum helium dilution test time given in lecture?

10 minutes

How much additional oxygen should normally be required during helium dilution?

About 200-400 mL

What should the helium dilution curve look like?

- Smooth

- regular fall

How many helium dilution tests are required according to the lecture?

At least 2 acceptable tests

How closely should helium dilution tests agree?

Within 10%

What maneuver is performed after helium dilution?

Slow vital capacity

How is RV obtained with gas dilution techniques?

Indirectly as a subdivision of FRC