Lung Mechanics Flashcards
What is respiration in biochemical and physiological terms
Biochemical - Energy producing chemical reactions(converting lactic acid to CO2 and H2O)
Physiological - An interchange of gases between an organism and its environment
What is ventilation
The movement of air into and out of the lungs (breathing)
What do the muscles in the lungs do
They control the diameter of the airways
What generates pressure differences for breathing
Respiratory muscles
What is the active part of breathing
inspiration
What allows expiration to be mostly passive
The elastic recoil of the lungs that pulls the lungs and diaphragm back to the resting position
What is the main respiratory muscle
Diaphragm
Note: not essential for life as other muscles can take over mostly
What effect does activity in the PHRENIC nerves cause in the diaphragm
Diaphragm flattens and descends in the chest, causing air to be drawn into the chest
What are the 3 flat muscles that are found in each intercostal space
External
Internal
Innermost
What are the roles of the intercostal muscles
- Increase the diameter of the chest to reduce pressure and draw air in.
- ## Stiffens chest during inspiration preventing it from being sucked in
When are the external intercostals most active and what motion do they control
Most active = inspiration
Moves ribs superiorly
When are the internal intercostals most active and what motion do they control
Most active = expiration
Moves ribs inferiorly
What is the role of the innermost internals
They just act with the internal intercostal muscles
What nerves innervate the intercostal muscles
Intercostal nerves
What two types of movement happen during inspiration
Pump-handle
Bucket-handle
Describe Pump handle and Bucket handle movements
Pump handle - anterior end of each rib is elevated
Bucket handle - diameter of chest increases by rib on either side raised from horizontal position
When can expiratory muscles actively contract
During high levels of breathing or if airways obstructed by disease
What are the most important expiratory muscles
Abdominal muscles
How do the abdominal muscles help expiration
They squeeze the contents of the abdomen up against the diaphragm and force it up into the chest to expel air
What is the intrapleural pressure (Ppl)
The pressure in the small amount of fluid between the visceral and parietal pleruae
Is the intrapleural pressure usually negative or positive with respect to the atmosphere and what effect does this ha ve on the lungs
Negative this means the lungs are firmly pressed to the chest wall as the space is airtight
What would happen if a puncture wound is made through the thorax
Air enters the pleural space, as the pleural pressure is less than the atmosphere, causing pneumothorax. The pressure around the lungs will increase and the lungs may collapse
What happens to intrapleural pressure during inspiration and expiration
Intrapleural pressure = more negative in inspiration, less negative for expiration
Can become positive in forced expiration
What are the elastic properties of the lungs caused by
elastic and collagen fibres
surface tension in the alveolar-liquid interface
What is lung compliance an expression of
the elasticity of the lungs or how easily they can be stretched
What is the main thing that affects lung compliance
Lung diseases
How is lung compliance defined
The change in volume produced by a change in pressure across the wall of the structure being investigated - lungs (Cl), chest wall (Cw) or lungs and chest wall (Total compliance Ctot)
What is the equation for compliance
Change in Volume/Change in Pressure
How would emphysema and fibrosis affect compliance
Emphysema = increased Fibrosis = decreased
Why does emphysema increase lung compliance
It causes destruction of the normal lung architecture, including elastic and collagen fibres, so lungs are mode easily distended and the compliance increases
Why does fibrosis decrease compliance
Scar tissue replaces normal interstitial tissue so the lungs become stiffer and compliance decreases
How is airway resistance (Raw) defined
This is the resistance to the flow of has within the airways of the lung
What is COPD
Chronic Obstructive Pulmonary Disease
What is bronchitis
Blocking of airways by secretions
What are the 2 types of airway flow
Laminar and Turbulent
Describe laminar and turbulent flow
Movement is orderly and streamlined whereas in turbulent flow movement is chaotic
What is Poiseuille’s Law
Laminar flow is described by this law and is the relationship between driving pressure and flow
How is airflow affected by tube radius
Wider tube = less resistance
Not directly proportional to change in resistance. radius in equation is r^4. so if radius is halved and everything else is constant, flow is reduced to 1/16.
