Lecture 13- Pulmonary lung function tests Flashcards
PFTs are tests that measure
- Lung volumes
- Rate of airflow
- Gas exchange (alveolar-vascular membrane)
PFTs used to
- diagnose patients with resp symptoms
- establish severity and progression of lung disease
- assess treatment response
- monitor patients on meds with lung toxicity
- Instruments used
- peak flow meter
- spirometry
- diffusing capacity of CO (DLCO)- provides info about alveolar-capillary membrane diffusing capacity
define peak expiratory flow
Maximum airflow rate attained during forced expiration (PEFR)
normal peak PEFR
- Normal >80% of predicted average based on
- Ethnicity
- Height
- Gender
- Age
what is used to measure PEFR
peak flow meter

baseline PEFR measured when
when pt is asymptomatic
- PEFR Useful in monitoring people with
asthma
Spirometry
- Used to measure some lung volumes
- Calculates airflow as volumes are measured over time
- Reports those values
- Also produces graphical representations

graph which can be produced by spirometry

Which values will spirometry give
- Tidal volume
- Inspiratory reserve volume
- Expiratory reserve volume
- Inspiratory capacity
- Forced expiratory volume in 1 second (FEV1)
- Forced vital capacity (FCV)
- FEV1/FVC

- Tidal volume
- Breathing quietly
- How much air you breathe in and out of the lungs

- Inspiratory reserve volume
Extra air inspired above and beyond normal inspiration (tidal volume)

- Expiratory reserve volume
Extra air expired above and beyond normal expiration

-
Residual volume
*
- Air left in lungs after expiratory reserve volume
- Spirometry cant measure this- can only measure air that can be blown or sucked into tube

- Functional reserve volume
= expiratory reserve volume + residual volume
- Also cant measure this using spirometry
- Represents the balance between lung inner elastic recoil and chest wall outer elastic recoil
- Volume of air left when the forces are equally balanced

- Inspiratory capacity
Amount of air I can breathe in (tidal volume) + inspiratory reserve volume

- Vital capacity
Amount of air breathe out after maximum inspiration
- Total lung capacity
- Vital capacity + residual volume
- Spirometry cant give this
- Vital capacity + residual volume

- Forced expiratory volume in 1 second (FEV1)
- maximum volume of can be forcefully expired within 1 second after maximal inspiration
- Forced vital capacity (FCV)
- total amount of air exhaled after maximal inspiration during entire FEV test – occurs over 6 seconds
- FEV1/FVC r
-
epresents proportion of patients forced vital capacity that they are able to expire in first second of forced expiration
- FEV1:FVC <70% (0.7) obstructive airway disease
volume time plot
shows FEV1 and FVC graphically
- characteristic shape
-
Healthy plot
- FEV1 = 4l
- FVC= 5l

Flow volume loops (spirotmetry doesn’t measure these)
- Volume of air present in lungs at transition maximum inspiration expiration = total lung capacity
- Volume of air present in lungs transition expiration to inspiration= residual volume (RV)





