7. Spirometry Flashcards
What are pulmonary function tests used for?
Used to diagnose patients with respiratory symptoms
Used to establish severity and progression of lung disease
Used to assess treatment response
Used to monitor patients on meds with lung toxicity
What are pulmonary function tests?
Tests that measure lung volumes, rate of airflow, gas exchange
What are the instruments/methods used in PFTs?
Peak flow meter
Spirometry
Diffusing capacity for carbon monoxide (DLCO)
What is peak expiratory flow?
Maximum airflow rate attained during forces expiration
Using peak flow meter
What is normal expiratory flow rate predicted off?
Ethnicity
Height
Gender
Age
What is spirometry used for?
Used to measure some lung volumes
Calculates airflow as volumes are measured over time
Which lung volumes can spirometry not measure?
Residual volume
Functional residual capacity
Total lung capacity
What can be measured in spirometry?
Forced expiratory volume in 1 second (FEV1)
Forced vital capacity (FVC) - occurs over 6 seconds
FEV1/FVC
What is forced vital capacity?
Total amount of air exhaled after maximal inspiration during entire FEV test - occurs over 6 seconds
What does an FEV1:FVC <70% indicate?
Obstructive airway disease
What is the flow volume loop?
Plot of inspiratory and expiratory flow (y-axis) against volume (x-axis) during performance of maximally faced inspiratory and expiratory manoeuvres
What is the FEV1 in obstructive lung disease?
Decreased
How much its decreased below normal provides information about disease severity
What is the FVC in COPD?
Initially normal, will decrease in severe disease
What is FVC in asthma?
Typically decreased - small airways close prematurely
Wha happens if there s air trapping because of small airways collapse?
Total lung capacity and functional residual capacity will be increased because of increased residual volume
What are some restrictive lung disease?
Interstitial lung disease
Myasthenia gravis
What does DLCO do?
Determines how much oxygen travels from alveoli of lungs to bloodstream i.e. diffusion provides information on alveolar-capillary membrane
When may decreased DLCO be present?
Emphysema - decreased SA
Alveolar inflammation - increased thickness
Pulmonary fibrosis - increased thickness
Would all have abnormal spirometry or chest x-ray
What does an abnormal DLCO with normal chest x-ray and spirometry suggest?
Problem with vascular part of membrane - idiopathic pulmonary arterial hypertension, chronic thrombi-embolism disease of lung
Need other tests to confirm
What will parenchymal lung diseases, such as interstitial lung diseases show?
Restrictive pattern and abnormal DLCO
What will restrictive lung diseases related to abnormalities in chest wall such as kyphoscoliosis show in DLCO?
Normal DLCO
What will restrictive lung diseases related to neuromuscular disease, for example myasthenia gravis show in DLCO?
Normal DLCO
