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36 Cards in this Set

  • Front
  • Back
What is the rate of supply of 02 at rest?
250 ml/min
What is the rate of removal of CO2 at rest?
200 ml/min
What is the RQ at rest?
What is the rate of supply of O2 during exercise?
> 4000 ml/min
What is the rate of removal of CO2 during exercise?
>4000 ml/Min
What is RQ during exercise?
Name some diseases causing increased metabolic demands.
Fever,cancer,wound repair.
How does PiO2 change in diff. environments?
At sea level,PiO2= 150 mmHg
At mountain level, PiO2= 70 mmHg
At 30 ft underwater level,PiO2 = 320 mmHg
What would decreased blood and tissue O2 cause?(hypoxaemia/hypoxia)
Metabolic acidosis
Increased tissue and blood CO2 causes resp. acidosis.
Inspiration is negative pressure ventilation.
What increases the longitudinal and lateral dimensions of the thorax?
Contraction of the diaphragm
Would contraction of the external intercostals increase the AP diameter of the thorax?
Yes-generating negative intrapleural pressure.
Inspiration is a passive process.
False-its an ACTIVE process.
What forces need to be overcome during Inspiration?
1.Resistive forces due to airflow through bronchi.
2.Elastic forces due to expansion of lungs and chest wall.
What are the inspiratory muscles?
-Diaphragm,External IC,sternomastoids.
What are the expiratory muscles?
Internal muscles,Abdominal muscles.
Ventilation requires energy.
What is the work of breathing?
Sum of elastic and resistive forces.
What is the alveolar-capillary membrane composed of?
1. Layer of surfactant
2. Type 1 alveolar cell
3. Basement membrane
4. Vascular endothelial(capillary) cell.
How does diffusion of gases in the lungs occur?
Via a passive process driven by the difference in partial pressures of gases on either side of the A-C membrane.
Diffusion rate of CO2 is 20x that of O2.
Is diffusion of O2 very fast?
Yes.Partial pressure of O2 in capillaries become equal to that in the alveoli in 0.25 seconds(during exercise) and 0.75 s at rest.
What is special about the transfer of 02?
It is perfusion limited--->limited by the amount of capillary blood(availability of free-binding sites on Hb) ,NOT the diffusing capacity of the A-C membrane.
When does diffusion become a limiting factor in O2 transfer?
in AC mb is grossly abnormal.(does occur with less severe disease during exercise)---same for CO2
Inadequate alveolar ventilation leads to
Elevated PaCO2.
What are the 3 problems that arise due to the large surface area spread over 300 million alveoli ?
1. How to ventilate and perfuse all AC units equally.
2. How to keep alveoli dry
3. How to prevent collapse of alveoli.
How do we achieve even distribution and perfusion throughout the lungs?
The bronchial and pulmonary arterial trees have fractal structures.(divide dichotomously for 23 generations so that the distance that air or blood travels to any part of the lung is abt equal.
Normally there is a small flow of fluid out of the capillaries.
What creates the risk of capillary fluid flooding the airspaces?
Juxtaposition of air filled alveoli and a wet capillary mb.
What keeps alveoli dry?
Lymphatics drain fluid moving from capillaries into the interstitial spaces before it can pass into the alveoli.(a few ml/hour but can increase)
What prevents movement of fluid between alveoli and instertitium?(alveolar cells can pump ions and water to the instertitium)
Tight junctions and surfactants.
What prevents collapse of alveoli?
Surfactant reduces Tension T and equalizes pressure.This prevents collapse of regions of lungs esp at the bases of lungs.
Define surfactant.
A group of closely related phospholipids secreted by type 2 pneumocytes.
What is the mechanism of action of surfactant?
It lowers surface tension at air/fluid interfaces,with the unique property of lowering Tension in proportion to thickness of layer of surfactant.
Name some functions of surfactants.
1.Prevents collapse of alveoli.(equalize pressure across lungs)
2.Increases lung compliance.
3.Helps to keep alveoli dry.