Respiratory Flashcards
describe the role and constituents of surfactant
surface active lipoprotein secreted by type 2 pneumocytes. The lipids have both a hydrophobic and hydrophilic region. Its role is to reduce surface tension allowing for symmetrical inflation of the alveoli.
what is negative pressure
pressure below atmospheric pressure
what is positive pressure
pressure above atmospheric pressure
define airway resistance
= 1/radius to the power 4
lateral traction
the elastic tissue linking the outside of the airways to the alveolar tissue helps the alveoli to expand during inhalation. It is the ease of expansion
transpulmonary pressure
the difference in pressure between the inside and ourside of the lungs. it increases during inspiration- airway radius increases, resistance decreases as the lungs expand.
boyles law
p1v1=p2v2
partial pressure of a gas
directly proportional to its concentration
anatomical dead space
the proportion in inhaled air which does not participate in gas exchange
the haldane effect
the more oxygen the blood holds the less carbon dioxide it can hold and vice versa
intrapleural pressure
changes in hydrostatic pressre of the intrapleural fluid which causes the lungs to move in and out during normal breathing. an increased intrapleural pressure compresses the small conducting airways and decreases their radii. Thus increased airway resistance
neuroendocrine and paracrine factors
can influence smooth muscle- thus influencing airway resistance.
where is airway resistance greatest in the lungs?
in the intermediate bronchi
Define type 1 respiratory failure and its causes
hypoxemic respiratory failure. low PO2, CO2 can be normal and high. It can be result of fluid in the lungs, pulmonary embolism or collapse of alveolar sacs or airway obstruction.
define type 2 respiratory failure and its causes
hypercapnic respiratory failure, High PaCO2. commonly caused by neuromuscular diseases, cardiac failure and emphysema. Commonly causes hypoxemia as CO2 levels in the blood alters pH of the blood too.
ventilation
the exchange of air between the atmosphere and the alveoli
I neurons
discharge during inspiration, relayed from C3,4,5 and T3,4,5,6 by the phrenic and intercostal nerves respectively innervating the diaphragm and intercostals
E neurones
discharge during expiration, relayed from the same areas but causes inhibition of I neurons. E neurons are only excited on forced expiration
pneumotaxic centre
may have a role in switching between inspiration and expiration
aperneustic centre
controls the speed of inhalation and exhalation
forced expiry volume 1
volume of air forcibly expired in one second
peak flow rate
the measure of air expired from the larger upper airway (highest rate of air flow out of the lungs)
total lung capacity 5900ml
the total volume of air the lungs can hold at maximal inhalation
vital capacity 4700ml
the volume of air exhaled after the deepest inhalation
