PFT Clinic

Which of the following volumes and capacities make up the Total Lung Capacity (TLC)?

• Inspiratory Reserve Volume (IRV) and Residual Volume (RV)
• Tidal Volume (TV) and Expiratory Reserve Volume (ERV)
• Inspiratory Capacity (IC) and Functional Residual Capacity (FRC)
• Vital Capacity (VC) and Inspiratory Capacity (IC)

Answer explanation

This is just memorizing this chart.

Examples: IC + FRC = TLC

IC + ERV + RV = TLC

VC + RV = TLC

Practice drawing it out! Once you can, do that at the beginning of your exam and you'll get all of those questions right every time.

In spirometry, which of the following is characteristic of a restrictive lung disease?

• Decreased Total Lung Capacity (TLC)
• Decreased Forced Expiratory Volume in 1 second (FEV1)
• Decreased FEV1/FVC ratio
• Increased Residual Volume (RV)

Answer explanation

With restrictive disease (all but the CBABEs) just consider them as smaller lungs. All of the measured volumes and capacities will be smaller.

On the FVC, the total capacity will be reduced. The lungs are smaller, so they don't have as much to blow out!

FEV1 -- or the speed that they are blowing out will be about normal. The FVC/FEV1 ration will be normal -- because the speed that they're blowing considering the size of their lung is normal -- not reduced like in obstructive disease.

A patient presents with an FEV1/FVC ratio of 0.7. This finding is indicative of:

• Normal lung function
• Restrictive lung disease
• Obstructive lung disease
• Mixed lung disease

Answer explanation

This is just more memorization. The FEV1/FVC ratio is what we use to determine if someone has obstructive disease. 70% is the minimum acceptable normal value.

To have obstructive disease, the ratio must be below that.

A patient's FVC is 2.5 liters, and their FEV1 is 1.5 liters. What is their FEV1/FVC ratio?

• 0.4
• 0.6
• 1
• 2

Answer explanation

FEV1/FVC ratio = FEV1 divided by FVC.

Just the simple calculation for it. Sometimes the NBRC wants to know that you know how.

Further, based on the FEV1/FVC ratio -- would this patient have normal lungs, obstructive disease, restrictive disease, or mixed disease?

Which of the following flow-volume loop patterns is most characteristic of an obstructive lung disease?

• Reduced peak expiratory flow rate (PEFR) and flattened inspiratory curve
• Decreased FEV1 and normal PEFR
• Decreased FVC and normal FEV1/FVC ratio
• Reduced expiratory flow with a scooped-out appearance

Answer explanation

Got a scoop in your loop? That's an obstructive issue.

Reason is that the top of the loop is exhalation, and it takes them longer to push the volume out -- hence the more slow exhale that it represents.

A patient exhibits a flow-volume loop with a scooped-out appearance. This is indicative of:

• Restrictive lung disease
• Normal lung function
• Obstructive lung disease
• Mixed lung disease

Answer explanation

Got a scoop in your loop? That's an obstructive issue.

Reason is that the top of the loop is exhalation, and it takes them longer to push the volume out -- hence the more slow exhale that it represents.

What is the classification of spirometry results for a patient with an FEV1/FVC ratio less than 0.7 and a reduced FEV1?

• Normal lung function
• Restrictive lung disease
• Mild obstructive lung disease
• Mixed lung disease

Answer explanation

FEV1/FVC ratio less than 0.7 means it's definitely obstructive. Since we don't have an actual value for FEV1, we can't really determine the severity -- but there is only one obstructive option as far as answers, so it's the best available.

FEV1s are graded on a similar scale to hypoxemia.

80 to 100% is normal

60 to 79% is mild

40 to 59% is moderate

Less than 40 is severe

Whichever range the patient's FEV1 fell in would classify the obstructive disease severity determined by the low FEV1/FVC ratio.

Which lung volume or capacity is typically increased in obstructive lung diseases?

• Residual Volume (RV)
• Inspiratory Capacity (IC)
• Tidal Volume (TV)
• Vital Capacity (VC)

Answer explanation

They can all be increased, but RV is where we see the biggest increase typically due to air trapping.

A patient presents with a TLC of 6 liters, an RV of 1 liter, and an ERV of 1 liter. Calculate their Inspiratory Capacity (IC).

• 3 liters
• 4 liters
• 5 liters
• 6 liters

Answer explanation

Another question you would get right if you can draw this chart out! Practice it!

What is the primary function of the Forced Vital Capacity (FVC) test?

• To measure the maximum volume of air a patient can exhale forcefully in one breath.
• To assess the patient's inspiratory capacity during normal breathing.
• To measure the volume of air remaining in the lungs after a maximum exhalation.
• To assess the patient's tidal volume during relaxed breathing.

Answer explanation

Knowing that it measures a forceful exhale is important. This type of breath is required so we can essentially measure the speed of the exhalation to test for obstructive disease.