Lung volumes Flashcards
What is tidal volume (Vt)
The volume of air entering the lungs during a single inspiration Vt
approx 500ml depending on body size
What is inspiratory reserve volume (IRV)
inspiratory reserve volume is the maximal amount of air that can be increased above tidal volume during deepest inspiration approx 3000ml (6 times greater then Vt)
What is functional residual capacity? (FRC)
This volume of air left in the lungs after expiration of a resting tidal volume
approx 2400ml
What is expiratory reserve volume (ERV)
This is the volume of air that can be expired after RTV has been expired through maximal active contraction of expiratory muscles
even after this the residual volume still remains
What is residual volume (RV)
The volume of air left in the lungs after expiratory reserve volume has been expired
What is vital capacity?
The maximal volume of air that a person can expire after maximal inspiration
expiration is RTV and IRV plus ERV (used to access pulmonary function)
What is forced expiratory volume in 1 sec (FEV1)?
This is when a person takes a maximal inspiration and then exhales maximally as fast as possible
The value is the fraction of total “forced” vital capacity expired in 1 sec
Healthy people can expire 80% in 1 second
What are pulmonary function tests?
- FEV 1 to vital capacity ratio
- Vital capacity
What do people with obstructive lung diseases show in pulmonary function tests? (increased airway resistance in asthma)
- Low FEV1 to vital capacity ratio (less than 80%) this is because it is hard to expire rapidly through obstructed airways
- Normal vital capacity
What do people with restrictive lung diseases show in pulmonary function tests?
- Normal FEV 1 to vital capacity ratio
- Reduced vital capacity
-Normal airway resistance but impaired respiratory movements because of abnormalities in lung tissue, pleura, chest wall or neuromuscular machine
Forced vital capacity
Vital capacity is the maximum amount of air a person can expel from the lungs after a maximum inhalation.
