Lung Function Testing Flashcards
What are the reasons for performing a lung function test?
Diagnosis (rarely diagnostic alone)
Pt assessment
Research purposes
What is a forced volume measurement?
How much air can the subject blow out?
How fast is the air expelled?
Pattern of change in flow-volume curve = can indicate site of obstruction
What can we learn from forced flow-volume measurements?
Pattern of change in flow-vol curve = can indicate site of obstruction
Response to treatment
Change in age/growth
Progression of disease
What is forced vital capacity (FVC)?
Total amount blown out from total lung capacity to residual vol
What is FEV1?
Forced expired volume in 1 sec
Normal = 80% of FVC = 0.8 ratio between FVC:FEV1
What is a flow volume curve/loop?
Flow vs vol
Above = expiratory flow
Below = inspiratory flow
Outline the pre-inspiration phase
No flow
Pressure within the lungs is atmospheric = 0
Pressure surrounding lungs is -ve (pleural pressure) keeping lungs and chest wall in balance
+ve pressure across airway = open
What happing during the inspiration phase?
Chest wall expands = pleural pressure more -ve, lung pressure become -ve = air drawn into lungs
+ve pressure across airway = open
Outline the end-inspiration phase
Pressure within lungs is atmospheric = 0
+ve pressure across airway = open
What happens during the forced expiration phase?
Chest wall compressed + elastic recoil of the lung = +ve pressure = air forced out of the lung
Pressure is able to compress airway
Outline what would be seen on a vol-time plot in obstructive lung disease
Takes pt longer to empty their lungs
Rate of change of vol is slower
Outline what would be seen on a vol-time plot in restrictive lung disease
Rate of rise in vol initially is normal
But due to restriction they cant blow out as much = reduction in vol
Outline what would be seen on a vol-time plot in mixed lung disease
Small flow vol
Slow exhalation
Briefly outline the practical aspects on spirometry
Seated
Observe the pt
Inspect the raw data
Nose-clips not essential but preferable
When is an extrathoracic abnormality evident?
On inspiration = pressure gradient sucks in airway
