Respiratory physiology 2 Flashcards
What is tidal volume?
Volume of air inspired/expired in a single breath (500ml)
What is the functional residual capacity?
Volume in normal lungs after expiration (2300ml)
What is residual volume?
Air in lungs after maximal expiration (1200ml)
What is expiratory reserve volume?
Air that can still be breathed out after normal expiration (1100ml)
What is inspiratory capacity?
Total amount of air that can be inspired after a normal tidal volume expiration (3500ml)
What is inspiratory reserve volume?
Quantity of air that can be forcefully inhaled after a normal tidal volume inhalation (3000ml)
What is vital capacity?
The volume of air that the patient can exhale after a maximal inhalation (4600ml)
What is total lung capacity?
Total volume of air in lungs (5800ml)
What prevents the alveoli from collapsing after expiration?
Residual volume
What are the 2 pleural membranes?
Parietal pleura (outer)
Visceral pleura (inner)
What is the role of the pleural sac?
Ensures lungs and chest wall stay connected.
What prevents the lungs recoiling?
Pleural fluid
What causes pneumothorax?
Air entering the pleural sac
Why does air move into the lungs when the diaphragm contracts?
Thoracic volume increase which decreases pressure allowing air to move into lungs (gas moves from high to low pressure)
How do external intercostal muscles increase thoracic volume?
They ‘lift’ rib cage which increase volume
How do internal intercostal muscles decrease thoracic volume?
The ‘pull’ ribs down which decrease volume
What is alveolar pressure?
Pressure of air within the lungs ( can be negative or positive depending on atmospheric pressure)
What is intrapleural pressure?
Pressure within the pleural cavity (always negative)
What is transpulmonary pressure?
Difference between alveolar pressure and intrapleural pressure (almost always positive as intrapleural pressure is always negative)
What effect does inspiration and expiration have on intrapleural pressure?
During inspiration intrapleural pressure becomes more negative, and during expiration it becomes more positive.
What muscles are required during forced inspiration?
Diaphragm, external intercostals, scalenes, stemocleidomastoids.
What muscles are required during forces expiration?
Abdominal muscles, internal intercostals.
What is the role of surfactant and how does it work?
To reduce surface tension
It sits in between water molecules to reduce attraction, preventing the collapse of the alveoli
What causes surface tension?
Air-water interference
At what stage of embryology is surfactant production complete?
36 weeks
What causes infant respiratory distress syndrome?
Insufficient quantity of surfactant in premature infants
What is compliance of the lungs?
Ability for lungs to expand
What is high compliance in the lungs?
High stretchability
i.e lungs will have a large increase in volume for a small pressure change.
What is low compliance in the lungs?
Low stretchability
i.e lungs will have a small increase in volume for a large pressure change.
Does high compliance represent healthy lungs?
Yes, but only when coupled with high elasticity
An example of a condition where lung compliance is low
Pulmonary fibrosis
An example of a condition where lung compliance if high, but elasticity is low
Emphysema
