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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
β-2 receptors do what in the lung?
promote smooth muscle relaxation. epi is the main activator of β-2 receptors.
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
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.
A normal DLCO will rule out what disease?
emphysema because in emphysema there is distruction of alveoli and decreased DLCO
What are four causes of alveolar hypoventilation?
-CNS depressing drugs
-diseases that suppress respiratory activity (ondine's curse)
respiratory muscle disease (myasthenia gravis)
-acute chest wall injury
Condition sthat reduce blood flow to the alveoli (embolism) do what to the VD/VT ratio?
they increase the ratio by increasing dead space.
Which area of the lungs is more ventilated and why?
The lower lungs are more ventilated because they have more change in volume with each breath
What are some factors that change diffusion in alveoli?
-fluid in alveoli
Sensitivity to PaCO2 is increased and decreased by what?
increased by hypoxia and decreased by CNS depressents, sleep, increased age
The carotid body and aortic body are fed to the medullary center by what nerves?
IX and X respectively
In high altitude, once respiratory alkalosis has acutely treated hypoxia, what takes over in the chronic state?
kidney begins to secrete HCO3-. respiratory alkalosis is corrected to pH. increased hemoglobin will also occur due to erythropoeitin secretion by the kidney
What is the respiratory response to severe metabolic acidosis?
Kussmaul respirations. deep and frequent. stimulation comes from peripheral receptors.
Is it wise to give a patient 50% O2 who has a normal pH and chronic hypercapnia?
No because you will relieve hypoxic vasoconstriction and send them into CO2 narcosis. give enough to elevate PaO2 to 60mmHg
Periods of apnea alternating with periods of hyperpnea when tidal volume waxes and wanes
Cheyne stokes breathing. seen in HF, brain damage, and high altitude
short periods of expiration alternating with prolonged inspiratory gasps
Apneustic breathing. Seen in brainstem trauma
Ventilation per unit lung volume is highest where in the lung?
it is higher at the base due to more lung volume
Intrapleural pressure is highest at what location in the lung?
It is highest at the apex, apical alveoli are more distended, alveoli at base are easier to ventilate and more compliant
What is the haldane effect in the lungs?
HbO2 has lower affinity for CO2 and H+. aids in release of CO2
What is the haldane effect in the tissue?
deoxygenated Hb has higher affinity for CO2 and H+. helps loading
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