35 - Pulmonary Pathophysiology Flashcards
What are the three major factors which will set off the peripheral chemo receptors and trigger an increase in respiratory rate?
1 - Increase in PCO2 ***
2 - Decrease in O2
3 - Decrease in pH
Describe the basic branching of the airway
The trachea bifurcates into two main stem bronchi, which then divide into lobar bronchi (one for each lobe), which in turn divide into segmental bronchi and into smaller and smaller branches until reaching the alveolus
Note that there is no gas exchange in the conducting airway
Describe the surface area achieved by the airway branching
Each branching of the respiratory bronchioles results in decreased diameter; however, the total surface area for that generation increases in size and number
Describe how gas exchange is maximized in the airway
In order to maximize gas exchange, capillaries branch as well as the airway
What is the KEY feature of obstructive airway diseases?
Increased resistance to airflow***
Give examples of obstructive airway diseases
- Inflammation of bronchial epithelium in bronchitis
- Secretions from epithelium (asthma, infection, decreased cilia)
- Constriction of smooth muscle in asthma
- Physical blockade (tumor, aspiration)
How do you calculate airway resistance?
Reynold’s formula
- Radius of the airway is the most influential factor determining airflow resistance.
- Resistance to airflow in the lower respiratory tract comes mainly from bronchioles and bronchi
What is Reynold’s formula?
R = (8nl)/(pi*r^4)
R = airway resistance n = viscosity of inspired air l = length of airway r = radius of the airway
What is the effect of parasympathetic activation on the airway resistance?
Increased airway resistance
- M3 activation occurs
- Examples: asthma, taking muscarinic agonists
What is the effect of sympathetic activation on the airway resistance?
Decreased airway resistance
- B2 activation occurs
- Examples: taking epinepherine or albuterol
What is the effect of bronchiolar size on the airway resistance
- Most important factor
- As bronchiolar size decreases, airway resistance increases
- Note that medium-sized bronchioles have the highest resistance compared to other bronchioles (most determinant factor on resistance)
What are three obstruction diseases that result from conditions in the airway wall?
1 - Asthma
2 - Acute bronchitis
3 - Chronic bronchitis
What is an obstructive disease that is related to the loss of lung parenchyma?
Emphysema
What are six obstruction diseases which are related to obstruction of the airway lumen?
1 - Bronchiectasis 2 - Bronchiolitis 3 - Cystic fibrosis 4 - Acute tracheobronchial obstruction 5 - Epiglottitis 6 - Croup syndrome
Describe why the respiratory surface between the air and blood is clinically relevant
Getting back to airway branching, you need to know the relationship between the air and the blood
- Very commonly affected by many disease states
- We want tot make sure the interface between the air and the blood is clear and free of infection
Describe the respiratory unit
The respiratory unit is where respiration takes place
- Consists of a respiratory bronchiole, alveolar ducts, atria and alveoli
- It is the site of gas exchange of the lung
Describe the pulmonary capillary network and “sheet of flow” concept
each alveolus contains 500 – 1000 capillaries that form a “sheet of flow” around it, substantially facilitating
gas exchange between the alveoli and the blood
Describe the capillary endothelium
- The endothelium of the capillary and the epithelium of the pulmonary unit are closely apposed
- There is only an ultra-thin barrier between the two surfaces
- There are NOT tight junctions here, but rather “leaky” cell junctions
Describe the function of this relationship between the capillary and respiratory unit
- The ultra thin barrier promotes gas exchange
- Water and solutes are able to move back and forth between the plasma and interstitial space due to “leaky” cell junctions
What is the respiratory membrane?
The basic respiratory membrane constitutes the
barriers that gas has to pass through for exchange
between the alveoli and the pulmonary capillary blood
What does the respiratory membrane consist of?
- a layer of fluid lining the alveolus containing surfactant - alveolar epithelium - epithelial basement membrane - interstitial space capillary basement membrane - capillary endothelial membrane
What is the effect of pathological conditions which affect the respiratory membrane?
Pathological conditions that
affect the thickness or integrity of any component of
the respiratory membrane will affect gas exchange at
the involved respiratory unit.
What is the lung interstitium?
The lung interstitial space or interstitium is
composed of connective tissue, smooth muscle,
lymphatics, capillaries, and a variety of other cells
What is the prominent cell in the interstitium?
Fibroblasts
Why are fibroblasts so important in the lung interstitium?
Fibroblasts produce collagen and elastin and therefore effect the distensibility and elastic recoil of the lungs
What is clinically relevant about the lung interstitium (interstitial space)?
Lung interstitium is very small under normal condition, but can become enlarged with inflammatory cells & edema fluid –> interfere with gas exchange