2 Breathing Mechanics Flashcards
What does Boyle’s law dictate?
Pressure exerted by gas is inversely proportional to its volume
(P proportional to 1/V)
i.e. larger volume of gas lower pressure
What is dalton’s law?
Total pressure of a gas mixture is the sum of pressures of all individual gases
What is charles’ law?
Volume of a gas is proportional to temperature
(V proportional T)
What is Henry’s law?
Amount of gas dissolved in a liquid depends on its solubility & pressure
What binds the lower respiratory system?
Ribs
Spine
Diaphragm
What is differnet about the external anatomy of the lungs?
Right lung has 3 lobes
Left only has 2 lobes
What are the lobes of the lung called?
Superior and inferior
Right lung has middle lobe
What encloses each lung?
Two pleural membranes separated by thin space of pleural fluid
What is the pericardial cavity?
Space around heart
What is the inner pleural membrane called
The one around lung (inner) is visceral pleura
What is the outer pleural membrane called?
The one coating inner rib surface (outer) is Parietal pleura
What is inflammation of the pleura called?
Pleurisy
What do pleura do?
Effectively stick lungs to ribs
Elastic recoil of chest wall keeps lung stretched open by opposing action of ribs at rest
What is pneumothorax?
When air gets into the pleural cavity causing lung to detach from ribs and collapse
What muscles are involved in inspiration?
External intercostal muscles
Diaphragm
Sternocleidomastoids
Scalenes
What muscles are involved in expiration?
Passive at rest
Under heavy respiratory load - internal intercostal muscles & abdominal muscles
What are the scalenes?
3 pairs of muscles in lateral neck connecting transverse processes of cervical vertebrae to the first 2 ribs
How does air enter the lungs?
- Muscles cause lung to expand increasing volume.
- Due to boyle’s law, pressure decreases
- Air moves from higher pressure outside to lower pressure in lung
What abnormal action occurs during asthma?
Over-constriction of bronchial smooth muscle
How does asthma cause breathing problems?
Over-constricted smooth muscle decreases airway diameter
Air flow resistance increases
Expiration becomes difficult
What are the 3 relevant pressures in breathing?
Intra-thoracic pressure (Alveolar) (Pa)
Intra-pleural pressure (Pip)
Transpulmonary pressure (Pt)
What is intra-thoracic (alveolar) pressure?
Pa:
Pressure inside thoracic cavity (lungs).
-ve or +ve compared to atmospheric pressure
What is intra-pleural pressure?
Pip:
Pressure inside pleural cavity.
Always -ve
What is transpulmonary pressure?
Pt:
alveolar pressure - intra-pleural pressure.
Always +ve because Pip is always -ve.
Is Alveolar pressure +ve or -ve?
Either as compared to atmospheric pressure
Is intra-pleural pressure -ve or +ve?
Always -ve
How is transpulmonary pressure determined?
Pt = Pa - Pip
What is the measurment of pressure?
mm Hg
‘millimetres of mercury’
How does alveolar pressure change?
During inspiration it decreases then returns to normal
During expiration it increases then returns to normal
How does intrapleural pressure change?
It decreases during inspiration
Returns to normal during expiration
What effects bulk air flow between atmosphere & alveoli?
Proportional to differnce between atmospheric & alveolar pressure.
Inversely proportional to airway resistance.
Equation for bulk flow of air?
F = (Patm - Pa)/R
When does Patm = Pa?
Between breaths at the end of unforced expiration
What factor determines how much air flows into the lungs?
- Airway resistance
- Pressure difference between atmosphere & alveoli
