The Mechanics of Breathing I Flashcards
Define:
Inspiratory capacity,
Inspiratory reserve volume,
and expiratory reserve volume.
IC - Maximum volume of gas that can be inhaled from end of resting exhalation. Equal to sum of of tidal and inspiratory reserve volume.
IRV - Additional air you can get into the lungs at the end of normal tidal volume.
ERV - Additional air that can be forcibly exhaled after the expiration of a normal tidal volume.
What is functional reserve capacity?
Volume of air present in the lungs at end of passive respiration.
What are compliance and elasticity?
Compliance - Ability of the lungs to stretch.
Elasticity - Tendency of lungs to return back to their normal shape.
What is pneumothorax?
Occurs due to stabbing or disease.
Air moves down pressure gradient from less negative alveoli into the intrapleural space.
Intrapleural pressure will become the same as atmospheric - becomes more positive.
Recoil forces of the lungs aren’t balanced, ∴ lungs collapse.
How do you measure lung compliance?
Measure the intra-oesophageal pressure - not commonly used now.
Spirometry now used.
What makes the lungs elastic?
Primarily is tissue structure - presence of elastin fibres in the lungs allows the lungs to stretch and then return to their original shape.
What happens in pulmonary fibrosis?
Collagen fibres are laid down in the alveolar regions of the lung.
Collagen is not stretchy, so lots of collagen makes the lungs stiff - becomes very difficult to inflate the lungs.
Because lung compliance is reduced, you have to generate even more negative intrapleural pressure to generate airflow.
What happens in emphysema?
There’s a breakdown of alveoli and elastin skeleton.
Lungs are now easier to inflate (compliance is increased) - due to less recoil, there’s decreased tendency of lungs to collapse.
What do pulmonary surfactant contain and where is this secreted from?
Phospholipids.
Proteins.
Secreted by alveolar type II cell.
What percentage of mass to surfactant protein A through D make up?
10%.
What are the functions of pulmonary surfactant?
Reduces work of inspiration.
Helps prevent alveoli collapsing.
Prevents alveoli from becoming waterlogged.
What is respiratory distress syndrome?
Found in premature babies that have not initiated surfactant secretion.
May also be mutation of surfactant protein B.
Result is alveolar collapse, lungs will be harder to expand, babies tire rapidly with effort required to inhale, and lungs waterlogged making gas exchange difficult.
How is respiratory distress syndrome treated?
Can be treated with artificial surfactant given to the baby.
Also treatment of mothers with glucocorticoids prior to deliver - initiates surfactant production and air fluid clearance.
Babies can also be given Continuous Positive Airway Pressure (CPAP) to keep airways open.
How does the mobility of thoracic cage affect compliance?
Skeletal disorders that affect the movement of the ribs or spinal column - e.g arthritis / ankylosing spondylitis may reduce lung compliance.
