First Pass Miss Exam 2 Flashcards
What areas of the medulla are involved in inspiration?
pre-Botzinger = pacemaker
rVRG (nucleus paraambiguus)
DRG (NTS)
Nucleus ambiguus = tense CN12, CN9, CN10 during inspiration to keep upper airway muscles clear
What areas of the medulla are involved in expiration?
cVRG (nucleus retroambiguus)
Botzinger (inhibits inspiratory muscles)
What is congenital hypoventilation syndrome?
Disease reducing phrneic nerve activity and altering respiratory frequency
can cause respiratory arrest during sleep
What is Rett syndrome?
Brainstem abnormality most common in females that can lead to breath holding / breathing arrythmia
What is Analgesia / respiratory depression?
Opoids can suppress breathing at pre-Botzinger complex, slow breathing.
What is the recoil pressure of a system defined as?
Pressure inside - pressure outside
If it were positive, the system would have a propensity to recoil outwards
Thus, a positive value across the lung wall = lung inflated. A negative value across the chest wall = chest is slightly collapsed at FRC relative to its resting point
What is the point which the lung deflates to if uncoupled from the chest wall?
Minimal volume
not reserve volume, which is max you can deflate with expiratory effort
What is the transpulmonary pressure vs transrespiratory system pressure?
Transpulmonary = pressure across the lung wall Transrespiratory = Palv - Patm
What accounts for 1/3 and 2/3 of the compliance behavior of the lungs, respectively?
1/3 - elastic behavior - inflation of one alveoli tends to inflate adjacent ones
2/3 - surface tension - propensity of liquid to try to reduce the air/liquid interface as much as possible
What is the function of surfactant?
Decreases work of breathing, increases compliance, stabilizes alveolar size, reduces hysteresis, dries alveoli
Why is the law of Laplace important for alveolar size?
Since P = 2T/R, if you decrease the radius of an alveoli, its pressure will be greater. If surface tension is not reduced by a higher concentration of surfactant here, it will further collapse. A reduction in T by surfactant prevents airflow away from the smaller alveoli
Why does pulmonary fibrosis lead to increased breathing effort?
Reduces lung compliance, requiring a more negative intrapleural pressure for the same volume (chest wall has to work harder to generate that more negative pressure)
What happens to resistance as lung volume increases, and how does the differ in COPD?
Airway resistance decreases as lung volume increases due to radial tension. COPD people have floppy lungs so at any given lung volume they have a greater resistance to flow as their alveoli / bronchi are always collapsed.
How do PANS and SANS affect airway resistance?
PANS - muscarinic Ach to constrict
SANS - beta2 receptor to dilate. circulating catecholamines are most important
What happens to blood flow in hypoxic alveoli? When is this really bad?
Blood vessels are vasoconstricted, really bad when living at high altitudes, can lead to chronic pulmonary hypertension
Why might vascular remodeling lead to decreased ability to accommodate cardiac output?
Normally, vascular tissues are compliant enough to store about 500 mL of blood for increased CO. If compliance is decreased because vessels thicken, then this blood will not be stored for LV increased loads.
What is the alveolar air equation?
PaO2 = PinspiredO2 - (PaCO2/R)
R = respiratory quotient, rate of CO2 production / oxygen consumption
Thus, if you tend to create more CO2 per oxygen, and your CO2 is that high, your O2 will be relatively lower.
What factors does the rate of the diffusion depend on?
- Diffusion coefficient - ^ with solubility, decrease with MW
- Area - increases diffusion rate
- Thickness - decreases diffusion rate
- Pressure gradient - increases diffusion rate
Vdiffusion = A/T * (P1-P2), which is the pressure gradient
Where is the highest ventilation / perfusion ratio in the lung?
At the apex, where there is minimal flow and lots of ventilation
What are the two compensatory mechanisms by which a lung with excellent ventilation but poor flow due to blockage would divert air to the opposite lung?
- Increased O2 causes bronchoconstriction of deadspace lung, diverting flow towards opposite
- Type II cells will decreased surfactant production when there is less flow -> increasing alveolar collapse
What are normal values for arterial and venous pCO2 and PO2?
arterial:
O2 = 100 mmHg
CO2 = 40 mmHg
venous:
O2 = 40 mmHg
CO2 = 46 mmHg
How is most CO2 in the body carried?
only 7% dissolved (but 24 times more soluble than O2). Rest as bicarbonate. Although venous blood has as much as 23% due to carbamino compounds (CO2 attached to amine of hemoglobin)
What three factors can lead to an increased A-a gradient?
V/Q defect
Diffusion defect
Right to left shunt
What are the two locations of the peripheral chemoreceptors?
- Carotid bodies - bifurcation of common carotid, afferents CN9
- Aortic body - superior wall of aortic arch
What do the peripheral chemoreceptors respond to?
CO2, H+, K+ and PO2 (only one to do this). Only get dramatic increases in minute ventilation at less than 60 mmHg O2
What do central chemoreceptors respond to?
increases H+ concentration, which gets across blood brain barrier via CO2.
What is the primary and then two additional functions of the stretch receptors?
Main function: terminate inspiration when lung volume is large enough
- Control breathing pattern -> frequency and tidal volume. Allows for shallower breaths if lung compliance is low to reduce the work of breathing
- Feedsback to give breathing discomfort if work achieved does not equal work demanded. -> dyspnea
What is the general function of irritant receptors?
Found all through airway, respond to mechanical / chemical stimuli and trigger a different reflex based on where you are.
I.e. Nasal = CN5 = sneeze
Tracheal = CN10 = cough
Epipharyngeal = CN9 = aspirate
What is the general function of irritant receptors?
Found all through airway, respond to mechanical / chemical stimuli and trigger a different reflex based on where you are.
I.e. Nasal = CN5 = sneeze
Tracheal = CN10 = cough
Epipharyngeal = CN9 = aspirate
What is the function of juxtapulmonary capillary (J receptors)?
They respond to engorgement of pulmonary capillaries / increases in interstitial volume of the alveoli. Feedback via vagus -> cause rapid shallow breathing, especially in heart failure / interstitial lung disease
They are a type of irritant receptor
What do all irritant receptors do? Why is this bad with asthma?
All stimulate breathing and produce bronchoconstriction. This is meant to increase airway velocity to flush things out. Like via coughing. Bad in asthma because you already have bronchoconstriction from active agents
What determines the fate of an upper airway particle?
Size. This dictates where they get trapped and their method of expulsion
Large - Trapped in nose + pharynx
Medium - small airway
Large/medium cleared via cilia / expectoration
Small - alveoli - cleared by alveolar macrophages. i.e. sulfur and nitrogen oxides