M103 T4 L2 Flashcards
How can be differentiate between obstructive or non obstructive spirometry?
the ratio between FEV1/FVC
When comparing the actual results to the predicted ones, what % of the predictive value for the population is normal?
within 80 to 100%
What should the FEV/FVC ratio be if an obstruction is present?
less than 70% / 0.7
What features does a spirometry graph showing obstruction have?
total volume is the same (under the graph)
the curve is less steep
What are two useful features of expiratory-flow volume loops?
makes it easier for us to see some early airway obstruction
gives us the ability to measure these mid expiratory flow rates as well
PEFR may be normal
What is the equation for recall flow?
recall flow = pressure gradient / resistance
What could cause a decrease in the radius of an airway?
Mucous or other obstruction Bronchoconstriction Compression (from a mass)
What two methods are there for measuring lung volume?
Helium dilution
Plethysmography “Body Box”
What are the ways of measuring the functional residual capacity of the lungs?
Alveolar filling process (e.g. pneumonia)
Lung tissue disease: Fibrotic lung disease
Pleural disease: pneumothorax, large pleural effusion, fibrosis of pleural tissue (“trapped lung”)
Chest wall disease (e.g. kyphoscoliosis)
Weakness (due to nerve and/or muscle disease)
How are the values different for a graph representing the lung volumes in fibrotic disease?
TV is normal
TLC, RV, FRC will be much lower
What causes abnormal gas exchange?
Airway disorders (asthma & COPD) Alveolar destruction (emphysema) Fibrotic lung disease (idiopathic lung fibrosis, asbestosis etc) Abnormal ventilatory control Abnormal environment (altitude) Measured as CO transfer factor
How is gas transfer / diffusing capaicty measured?
CO diffuses like Oxygen - can be measured as a marker for oxygen
CO binds to Hb and is carried away
Inhale known volume of gas with low concentrations of CO and Helium
Hold breath for known time
Measure CO and He in expired air
the dilution gives alveolar volume
What are the pulmonary diseases that decrease the results of the gas transfer test value?
Emphysema
Alveolar filling process
Lobectomy
Scarring or inflammation around the alveolar wall
What are the cardiovascular / haematological diseases that decrease the TLco?
Cardiovascular /haematological disease Pulmonary hypertension Low cardiac output Pulmonary oedema Anaemia
Occasionally, what three factors can be increased in high output cardiac states?
High cardiac output
Pulmonary haemorrhage
Polycythaemia
