Airflow and airway resistance- Handout 3 Flashcards
What is airway flow
ventilation
What is the equation airflow.
Define the parameters
Fa= (Patm-Palv)/R
Fa=airway flow
Patm-Palv= partial pressure difference between atmosphere and alveolar
R= resistance
How is airflow normally affected by resistance
normally resistance is very low and there is a small alternating between partial pressure of alveolar (-1 to 1) for air motion
What are the types of airflow
laminar
turbulent
transitional
What is laminar air flow
small airways close to alveoli
What is turbulent airflow
trachea
What is transitional (mixed) airflow
segmental bronchi
What is poiseuille’s law
resistance to laminar flow is inversely proportional to the fourth power of radius
What is the equation of poiseuille’s law; what can you infer from this
R= 1/r^4; that a small narrowing of the airways creates a huge increase in resistance to airflow
What happens to resistance during an inspiration
the resistance falls because of a widening of the bronchial tree- the tree lengthens and widens during inspiration
What happens to resistance during a expiration
the resistance rises up to 20% during expiration
What are some chemical and physiological factors control airway constriction
- parasympathetic (vagus nerves, cholinergic agonist)
- histamine and prostaglandins
- decrease in carbon dioxide
What are some chemical and physiological factors that control airway dilation
- beta-2 agonist (epinephrine released by the adrenals)
- some prostaglandins
- increase carbon dioxide
How does the autonomic nervous system control the airways
the airways are innervated by the efferent (motor) fibers that constrict the bronchial smooth muscle
How are the bronchi narrowed
vagal stimulation-parasympathetic fibers constrict the airways
What are some other features of the vagus nerve
it also contains afferent (sensory fibers) that convey information from the lung (distension, pain, etc) tissue to the central nervous system
Which part of the vascular system has the highest resistance
small arterioles
In contrast, most resistance to airflow does not reside in terminal bronchioles. Why not?
tremendous branching and the large number of bronchioles; as a result the total resistance at the level of bronchioles is less than upstream
What can lead to dangerous airflow obstruction
after upper airway narrowing (especially in children)
Where does the most AIRWAY resistance occur
50% of the total airway resistance resides in the nose
How do most children normally breathe
nose breathers
What factors increase nasal airway resistance
mucus secretion
dilation, engorgement and increase in permeability of blood vesses
What are some causes of nasal airway resistance
infection, allergy, sympathetic denervation (horners syndrome)
What is rhinitis
irritation and inflammation of the nasal mucous membrane
What is the action of histamine
one of the mediators involved in inflammatory and allergic responses that leads to fluid accumulation in the nose and congestion
What is the action of bradykinin
an inflammatory substance that causes vasodilation, fluid accumulation outside of blood vessels, swelling and increase in nasal airway resistance
What is Ludwigs angina
complication that can be fatal; usually from an odontogenic infection
What are the signs of ludwins angina
stridor (raspy noise while breathing)
muffled voice
swollen tongue
inability to tolerate secretions
What is coup; who does it impact and how does it occur
see other slides; its a common illness with scary symptoms; viral infection of children aged six months to 3 years-can strike at night
What are obstructive pulmonary diseases
disease with high airflow resistance; cant get enough air through; airflow is low and expiration takes longer time
What are types of obstructions in the pulmonary tract
- extrapulmonary-sleep apnea, croup
2. intrapulmonary-asthma, COPD-cant get air out of lungs
What characteristics do patients normally have with obstructions; how does that differ from patients with emphysema
slower peak expiratory flow
How can you assess airflow obstruction
1
What are the three main measurements of airflow
1
What is the normal FEV1/FVC ratio in a normal lung
1
What does obstruction do to the FEV1/FVC ratio
1
What does lung fibrosis do to the FEV1/FVC ratio
1
What is the break down of how many people are affected by obstructive pulmonary diseases
1
Compare the two diseases COPD and asthma: age dyspnea FEV1/FTC RV, TLC cough smoking
1
What are the distinctive featureso f hcho
1
