Lung Function Tests Flashcards
How would you use lung function tests
Diagnosis and monitoring of
- disease progression
- risk stratification
- treatment response
What are the 4 routine LFTs
Spirometry
Lung volume
Gas transfer
Volitional resp muscle strength
What are the 4 specialist LFTs
Exercise bronchial provocation
Exhaled biomarkers
Lung mech, forced oscillations
Non volitional resp muscle strength
What are some examples of
- airway
- chest wall
- lung
- muscle
- thoracic cavity
- pulmonary vasculature diseases
Airway
- Asthma
- CODP
- Bronchiolitis
Chest wall
- Scleroderma
- Kyphoscoliosis
- Pregnancy
- Obesity
Lung
- IPF
- Tumour
- Resection
- Collapse
Muscle
- Polio
- NMD
- Phrenic palsy
Thoracic cavity
- Cardiomegaly
- Effusion
- Tumour
Pulmonary vascular diseases
- PE
- HF
What are the characteristics of obstructive illnesses
What are some examples
Decreased airflow due to lumen obstruction
Airway wall changes
Airway support loss
Ext compression
Asthma COPD Bronchiectasis Bronchiolitis CF
What are the characteristics of restrictive illnesses
What are some examples
Decreased lung volume Abnormal lung parenchyma Abnormal chest wall Weak resp muscles Abnormal pleura
Fibrosis Kyphoscoliosis DMD Phrenic palsy Obesity
What are the characteristics of mixed illnesses
Decreased airflow and lung volume
SCD
Idiopathic fibrosis + emphysema
How would you differentiate between obstructive and restrictive lung disease on a flow volume loop
Obstructive
-concave shape on expiration as airways collapse
Restrictive
-similar shape to normal loop but smaller
Each disease has its own characteristic shape
How would you differentiate between obstructive and restrictive lung disease on spirometry
What can you not diagnose via spirometry
Obstructive
- FEV1 < 0.8
- FRC reduced slightly
- FEV1/FRC <0.7
Restrictive
- FEV1, reduced
- FRC, reduced
- FEV1/FRC normal
Cannot diagnose restrictive diseases
-in obstructive diseases, airways collapse on themselves so FRC may be reduced. Can look restrictive
What is the reversibility test
How would you differentiate between asthma and COPD
Repeat spirometry after BD
-Increased FEV1 > 12% => significant reversibility
Asthma, significant reversal
COPD, relief due to some deflation but no significant reversal
What are the definitions of
- RV
- TLC
- FRC
How would you measure lung volume
RV -vol after max expiration TLC -vol after max inspiration FRC -vol after relaxed expiration
Gold standard
Body plethysmograph
Inert gas dilution
N2 washout
CXR planimetry
volume CT
USS
What are the causes of increased FRC, RV
- intrapulmonary
- extrapulmonary
Intrapulmonary
-airway obstruction
Extrapulmonary
-resp muscle weakness
What are the causes of increased TLC
Emphysema
What are the causes of decreased TLC
- intrapulmonary
- extrapulmonary
Intrapulmonary
- Pneunectomy
- Atlectasis
- Consolidation
- Edema
- Fibrosis
Extrapulmonary
- pleural disease
- ribcage issues
- resp muscle issues
- obesity
What is the transfer coefficient
What is it a measure of
What factors does the TLCO depend on
- alveolar mv
- Hb binding
KCO=TLCO/Va
Gas uptake/litre of vent lung
gas transfer from lung to Hb Alveolar mv -SA -conc change -solubility -MW
Hb binding
- [Hb]
- perfusion
- PO2