Ventilation and Compliance Flashcards
Lung capacity
About 6 litres
Tidal volume
Volume breathed in or out at rest
Residual volume
Allows stays in alveoli (stops alveoli from collapsing, allows gas exchange to always be taking place)
Vital capacity
Volume of air that can be moved - tidal volume, inspiratory reserve volume and expiratory reserve volume
Expiratory reserve volume
Maximum volume of air that can be expelled from the lungs at the end of a normal expiration
Inspiratory reserve volume
Maximum volume of air that can be drawn into the lungs at the end of a normal inspiration
Total lung capacity
Vital capacity + residual volume
Inspiratory capacity
Tidal volume + inspiratory reserve volume
Functional residual capacity
Expiratory reserve volume + residual volume
Pulmonary ventilation
Total air movement into/out of the lungs (L/min)
Alveolar ventilation
Fresh air getting to alveoliand therefore available for gas exchange (L/min)
Partial pressure
The pressure of a gas in a mixture of gases is equivalent to the percentage of that particular gas in the entire mixture multiplied by the pressure of the whole gaseous mixture
Hyperventilation
Oxygen pressure rises
Hypoventilation
Oxygen pressure falls - lots of shallow breaths
Surfactant
Detergent-like fluid produced by type II alveolar cells
Reduces surface tension on alveolar surface membrane thus reducing tendency for alveoli to collapse
Increases lung compliance
Redduces lung’s tendency to recoil
Makes work of breathing easier
More effectiv in small alveoli as molecules more concentrated
Compliance
Change in volume relative to change in pressure
High compliance
Large increase in lung volume for small increase in pressure
Emphysema
Loss of elastic tissue means expiration requires effort
Fibrosis
Inert fibrous tissue means effort of inspiration increases
Obstructive lung disease
Obstruction of air flow, especially on expiration
Restrictive lung disease
Restriction of lung expansion
Obstructive lung disorders
Asthma COPD (chronic bronchitis - inflammation of the bronchi, emphysema - destruction of the alveoli, loss of elastisity)
Restrictive lung disorders
Loss of lung compliance
Fibrosis - excess fibrous connective tissue
Infant respiratory distress syndrome - insufficent surfactant production
Oedema
Pneumothorax
Spirometry
Technique used to measure lung function
Anything not involving residual volume can be measured using spirometry
Static spirometry
Only consideration is volume exhaled
Dynamic spirometry
Time taken to exhale a certain volume is measured
Anatomical dead space
Volume of air taken in during each breath that does not mix with the air in the alveoli. Measure of the volume of the conducting airways
Surface tension in alveoli
Caused by air-water interface on the surface of the alveoli due to the air being humidified
Distensibility
Surfactant increases lung compliance
Pressure-volume compliance
Easier to inflate once it has started to inflate
Needs to overcome tissue inertia (elastic recoil) and surface tension
Effect of gravity on compliance
Alveoli at base of lung squashed and so more able to open - change in transpulmonary pressure - base increases in volume more than apex
Restrictive ratio (FEV1/FVC)
Stays the same or increases due to less air able to get into lungs
Obstructive ratio (FEV1/FVC)
Ratio drastically decreases as forced expiratory volume massively decreases
FEV1
Forced expiratory volume in 1 second
FVC
Forced vital capacity
FEV1/FVC in healthy males
80%
