lecture 3 - lung function tests Flashcards
What are the 2 key techniques for assessing ventilation?
Blood gases, lung volumes/flows (spirometry/peak flow rates)
What is the key blood gas measurement that can assess ventilation?
PaCO2 (arterial partial pressure of CO2)
What are the 2 key things that spirometry measures?
Volume of air, and its speed (flow)
What are the 4 volumes that can be measured with spirometry
Tidal volume, Inspiratory reserve volume, Expiratory reserve volume, residual volume
What is tidal volume?
The volume of air that moves in and out of the lungs during normal, quiet ventilation
What is inspiratory reserve volume?
The extra air that can be inspired if the external intercostal muscles are contracted to maximise ventilation
What is expiratory reserve volume?
The extra volume that can be expelled if the internal intercostal muscles are contracted maximal active expiration
What is residual volume?
The air remaining in the lungs after maximal expiration
What are the 4 capacities that be calculated via spiromtery?
Vital capacity, total lung capacity, inspiratory capacity, functional residual capacity
What is vital capacity, and how is it calculated?
The maximal volume of air from a max breath in to a max breath out - ERV + VT + IRV
What is total lung capacity, and how is it calculated
The total amount of air you can hold in your lungs - VC+ RV
What is inspiratory capacity, and how is it calculated?
The total amount you can breath in with maximum inspiration - VT + IRV
What is functional residual capacity, and how is it calculated?
Volume in the lungs at the end of normal, tidal expiration - ERV + RV
What are the 2 measurements made with forced spiromtery?
Forced vital capacity (FVC), Forced Expiratory Volume in 1 second (FEV1)
What pathologies can cause reduced Forced Expiratory Volume (FEV1)?
Obstructive airways disease, small/scarred/fibrotic lungs
What type of lung disease does the FEV1/FVC ratio help to identify?
Obstructive lung disease - ratio<0.7
What is the normal range for FEV1/FVC ratio?
> = 0.7
What is the unit for Peak Expiratory Flow Rate (PEFR)?
L/min
What is obstructive lung disease?
Increased resistance to airflow
What is restrictive lung disease?
Reduced lung volume due to reduced compliance (stiff lungs) - lungs are less able to expand
What are some examples of obstructive lung conditions?
Chronic bronchitis, emphysema/COPD, asthma
What are some examples of restrictive lung conditions?
Pulmonary fibrosis, pulmonary oedema, chest wall deformity/muscle problems
How does FVC change in patients with restrictive lung disease?
Decreased - reduced air can fit into the lungs
How does FEV1 change in patients with restrictive lung disease?
Decreased, but proportionate to the decrease in FVC
