Respiratory 6 Flashcards
If perfusion remains constant and hypoxia is not caused by hypoventilation or alterations in atmospheric PO2 then what causes the problem
Issue with gas exchange between the alveoli and blood
- issue at exchange barrier with diffusion
What causes an issue with gas exchange
Alterations in a layer
Water layer, or interstitial space
What are the layers between alveoli and capillary
Alveolar air - water layer - interstitial space - alveolar type 1 epithelial cell - interstitial space with matrix - blood plasma - cytoplasm of RBC
What happens to oxygen once diffuse into cytoplasm of RBC
Attaches to hemoglobin
Diffusion
Random movement of molecules from a region of high concentration to a region of low concentration
What are 4 things that will affect the random movement of gas molecules between the alveoli and capillaries
- Concentration gradient
- Surface area
- Barrier permeability
- solubility of gas - Diffusion distance
What is the only thing that changes in healthy individuals to affect diffusion
Concentration gradient
What is directly proportional to diffusion
Surface area, concentration gradient, barrier permeability
What is inversely proportional to rate of diffusion
Distance
What is constant under normal conditions in relation to diffusion
Surface area, diffusion distance and barrier permeability
What is the main determinant of diffusion
Concentration grradien
Emphysema
PO2 normal or low
- destruction of alveoli
- decreased surface area
What diseases cause hypoxia
Emphysema, fibrotic lung disease, pulmonary edema, asthma
Pulmonary fibrosis
- PO2 normal or low
- thickened fibrous connective tissue slows gas exchange
- loss of lung compliance
- decreased barrier permeability
Restrictive
Pulmonary edema
Fluid in interstitial space increases diffusion distance
- PO2 normal
Asthma
Increased airway resistance, bronchioles constrict
- PO2 low
- decreased concentration gradient
What is alveolar gas exchange influenced by
O2 reaching alveoli and gas diffusion between the alveoli and blood
What is O2 reaching alveoli determined by
Composition of inspired air
Alveolar ventilation
What is alveolar ventilation determined by
Rate and depth of breathing, airway resistance, lung compliance
What is gas diffusion between alveoli and blood determined by
Surface area and diffusion distance/permeability
What is diffusion distance/permeability determined by
Barrier thickness, amount of fluid
Why must respiratory gases be soluble in liquids
Alveoli lined with liquid, space between alveoli and capillaries liquid and plasma is liquid