Pulmonary function tests

Question 1

What is peak expiratory flow (PEF)?

Answer 1

• The maximal speed of airflow as the patient exhales (L/min)
• Increase in PEF value = lung function is better, decrease = wprse
• predicted values used depending on age, height and gender

Question 2

What is FVC?

Answer 2

• The maximal amount of air (L) that the patient can forcibly exhale after taking a max inhalation

Question 3

What is a spirometer?

Answer 3

• records the volume of air that is breathed in and out
• ## Generates tracings of air flow

Question 4

What are tracings used to calculate?

Answer 4

• Vital capacity (Vc), Tidal volume (Vt)
• The flow rate of air movement

Question 5

How do modern spirometers work?

Answer 5

• Use electronic method of measuring the gas inhaled/exhaled through a mouthpiece
• Vitalograph - records the volume expired during a vital capacity breath common in primary care setting
• FVC standing vs seated
• High intrathoracic pressure can result in reduced cardiac output and cerebral blood flow
• Subject is observed

Question 6

What is a spirometer?

Answer 6

• Floating bell jar
• Expired gas passes into water seal
• Increased pressure causes jar to rise
• Movement transmitted to pen
• Pen movement proportional to volume breathed in/out

Question 7

Explain what trace movements indicate?

Answer 7

INSPIRATION = upward deflection
EXPIRATION = downward deflection

Question 8

How to calculate Inspiratory Capacity?

Answer 8

VT (TIDAL V) + IRV ( inspiratory reserve volume)

Question 9

How to calculate functional residual capacity?

Answer 9

ERV + RV

Question 10

What do forced flow-volume measurements show us? (FVC, FEV)

Answer 10

• How much air can the subject blow out (reduced in restrictive disorders)
• How fast the air is expelled
• Pattern of change in flow-volume curve can indicate site of obstruction
• Response to treatment
• Change with age or growth
• Progression of disease

Question 11

What is FEV1?

Answer 11

• The volume exhaled in the first second
• most reproducible flow parameter. Useful in diagnosing and monitoring patients with obstructive pulmonary disorders (asthma, COPD)

Question 12

What is peak expiratory flow?

Answer 12

• Max speed of airflow as the patient exhales

Question 13

Describe volume-time graphs in obstructive disease (Asthma, COPD)

Answer 13

-FVC is not markedly reduced
- Narrowed airways reduces the speed at which air can be breathed out
- Fraction of air expelled during 1st sec (FEV1)- markedly reduced
- Typical pattern in obstructive airways disease :
- FVC nearly normal
- FEV1 markedly reduced
- FEV1/FVC ratio <70%

Question 14

Describe Volume-time graphs in restrictive disease (lung fibrosis)

Answer 14

• FVC markedly reduced (lungs are stiff, cannot be expanded adequately)
• Speed at which air can be breathed out is normal (no airway narrowing)
• FEV1 is reduced but proportionally so to FV
• Typical pattern in restrictive airways disease:
• Low FVC
• Low FEV1 but proportional
• ## FEV1/FVC ratio >// 70%