a Flashcards
(26 cards)
How is respiatory pressure described?
Relative to atmospheric pressure.
How does Ppul change with breathing?
Fluctuates. Eventually always eventually equalises itself with atmospheric pressure if the airways are open to the atmosphere.
How does Pip change with breathing.
Usually less that intrapulmonary pressure and atmospheric pressure except during active (forced) respirations.
What two forces act to pull the lungs away from the thoracic wall.
Elasticity of lung tissue and surface tension of alveolar fluid
What counteracts the collapsing forces in the lungs?
The elasticity of the inflated chest wall pulls the thorax outwards to enlarge the lungs.
When can lung collapse only occur?
When the integrity of the chest wall is compromised during a pneumothroax.
What is Boyle’s gas law?
P1V1=P2V2. It shows that the relationship between the pressure and volume of a fixed amount of gas molecules within an enclosed container.
How is air expelled from the lungs during exercise.
The expiratory muscles are used.
These are external oblique, internal oblique, rectus and transverse.
How is the relationship between airflow (F) , the pressure driving the airflow (P), and the resistance to the airflow described?
F=ΔP/R
What does F=ΔP/R mean?
Airflow is inversely proportional to airway resistance.
What causes airway resistance?
Bronchoconstriction.
What determines lung compliance?
Distensibility of lung tissue due to elastic tissues in lungs.
Surface tension of the alveoli.
What factors diminish lung compliance?
Fibrosis (scar tissue)
Blockage of passages with mucous, fluid, bronchospasm
Reduced production of lung surfactant
What is the respiratory membrane?
The structures that separate the alveolar air from the pulmonary capillary blood.
What factors impact the rate of O2 and CO2 across the respiratory membrane in the alveoli?
Pressure gradients
Surface area.
Thickness of the respiratory membrane
What does Dalton’s law of partial pressures say?
Rate of diffusion across the respiratory membrane is dependent on the concentration gradiant or partial pressure gradient.
What is the partial pressure of o2 in the alveolar air and in mixed venous blood? Therefore what is the concentration gradient of O2 across the respiratory membrane.
104mmHg vs 40mmHg
CG=64mmHg
What is the pressure gradient of CO2 across the respiratory membrane?
PCO2 is 40mmHg in alveolar air.
PCO2 is 45mmHg in mixed venous blood.
Therefore pressure gradient is 5mmHg
What is PO2 and PCO2 in atmospheric air?
PO2=160mmHg
PCO2=0.3mmHg
What is the PO2 and PCO2 in the alveoli?
PO2=104mmHg
PCO2=40mmHg
What is PO2 and PCO2 in the venous mixed blood?
PO2=40mmHg
PCO2=45mmHg
What is the PO2 and PCO2 in blood leaving pulmonary capillaries?
PO2=104mmHg
PCO2=40mmHg
Same as alveolar air
What is ventilation?
The volume of gas that reaches the alveoli each minute.
What is perfusion
The volume of blood reaching alveolar pulmonary capillaries each minute.
