What would happen without surfactant in the alveoli?
lung recoil would be so powerful that inspiration would not be possible. decreased radius increases pressure. surfactant decreases tension.
Surfactant is secreted by what cells?
type II alveolar epithelial cells by exocytosis of lamellar bodies
What happens to dynamic compliance in obstructive lung disease?
increased breathing freq. decreases compliance. There is not enough time to fill alveoli
How does branching affect airway resistance in the pulmonary system?
branching actually makes total resistance to flow LESS
Effect of parasympathetic activity on muscarinic receptors?
smooth muscle contraction.
β-2 receptors do what in the lung?
promote smooth muscle relaxation. epi is the main activator of β-2 receptors.
Increased lung volume does what to Raw?
increased lung volumes decrease airway resistance
Two forces that determine caliber of intrathoracic airways during changes in lung volume?
transmural pressure change, pull on the airways by fibrous connections with their surrounds (radial traction). ↓ in intrapleural presure causes ↑ in transmural pressure and ↑ in radial traction and airways open. opposite for expiration
In emphysema what causes the obstruction?
reduced radial traction due to destruction of the interstitial elastic fibers.
What causes the puffer in pink puffers?
pursing the lips and partially closing the epiglottis increases the airway pressure during expiration keeping the alveoli open
Alveoli are more compliant at the base or apex?
at the base they are more compliant because at the apex they are inflated more. there is a progressive increase in alveolar ventilation from apex to base
Tidal volume is the total of what things?
VA + VD. alveolar space plus dead space
Physiologic dead space is?
anatomic dead space plus alveolar dead space. pulmonary embolus can stop blood flow to alveoli and that air is dead space.
Increased breathing frequency does affects alveolar ventilation how?
decreased alveolar ventilation with increased frequency of breaths. VdotA= VdotE - VD x freq
Increased in alveolar ventilation cause PaO2 to _______?
increase in alveolar ventilation causes PaO2 to increase and PaCO2 to decrease.
What is the effect of high altitude on PAO2?
High altitude means lower barometric pressure which lowers the PAO2. Low PaO2 due to hypoxemia would cause hyperventilation and decrease in PACO2
What are some causes of an increased diffusion time leading to increased A-a gradient?
pulmonary interstitial edema, interstitial fibrosis, alveolar edema increase the diffusion time and increase the A-a gradient
Although PaCO2 usually stays the same regardless of changes in PaO2, what can cause an A-a gradient difference by altering PaCO2?
drugs such as acetazolamide inhibit carbonic anydrase and reduce rate of CO2
Conditions that decrease DLCO?
Thickening of the alveolar-capillary membrane, decreased surface area, decreased uptake by erythrocytes, V/Q mismatch.
A reduction in P50 mean that affinity for O2 ______ and an increase in P50 means that affinity for O2 _______
reduction in P50 increases affinity for O2 and increase in P50 means a decrease in affinity for O2
Increased PCO2 does what to P50?
increased PCO2 ↑ P50. Increased oxidative metabolism increases CO2 and reduces affinity for O2 so more O2 can be unloaded and go to tissues.
FEF 25-75 shows what?
it shows the state of smaller airways.
A normal DLCO will rule out what disease?
emphysema because in emphysema there is distruction of alveoli and decreased DLCO