Lecture 15: Worth of breathing/Lung volumes Flashcards
What is spirometry?
What is a spirometer?
Spirometry allows us to measure lung volume and air flow rates
A spirometer measures the volume inspired/exhaled; you do this by breathing into/out of a howl bell inverted over water
What can spirometry distinguish between?
Obstructive pulmonary disease = increased resistance to air flow
e.g asthma, Chronic bronchitis. Emphysema
Restrictive disorders = decreased lung volume - reduced lung compliance
- reduction in lung volume from structural or functional lung changes
e. g fibrosis, chest/wall abnormalities and respiratory muscle disease
What is tidal volume?
- lung volume type
= 500ml
- Is the volume of air that moves in and out during normal quiet ventilation
What is inspiratory reserve volume IRV ?
- lung volume type
= 3L
- Is the extra volume that can be inspired with maximal inhalation - external intercostals
What is the expiratory reserve volume ERV?
- lung volume type
= 1.5L
- Is the extra volume that den be exhaled with maximal effort - internal intercostals
What is the residual volume RV?
= 1.2L
Is the volume remaining in the lune after maximal expiration
average = 0.8 - 1.4L
What is forced vital capacity FVC?
Why are the measurements from forced expiration useful?
FVC = maximum breath in to maximum breath out - forced as hard as possible
- Forced measurements give info about flow
- Forced expiratory volume in one second FEC
= reduced with disease causing resistance to airflow
= Normal = 80%
What is vital capacity?
- lung capacity type
What is total lung capacity?
= 5L
- Maximal breath in to maximum breath out - volume of air you can shift in/out of the lungs
= 6L
- Is the total volume in then lungs which maximally full = VC + RV
What is inspiratory capacity?
What is functional residual capacity ?
- lung capacity types
= Tidal volume + IRV
= 2.5 L
Is the volume in lungs at equilibrium point - volume at end of normal breath out
How is the work of breathing influenced by compliance
What is lung compliance?
To expand the lungs you need complaint lungs
- A measure of how easy it is to change lung volume
How is the work of breathing influenced by surfactant?
Surface tension generated by fluid lining the alveoli is overcome by surfactant with reduces surface tension so the lungs can expand.
- lowers surface tension in alveoli
- reduces attractive forces btw fluid molecules lining alveoli
- easier to increase lung size
lack of surfactant —> stiff lungs
How is the work of breathing influenced by airway resistance?
Muscle need to move air - overcome air resistance
- most of the resistance to airflow arises in the upper airway and the first 6 generation of the lower airway
