Flashcards in Respiratory Deck (340)
peculiar feature about newborn respiratory physiology
obligate nose breathers
RV vs. ERV
RV is the volume of air remaining after a maximal expiration. ERV is the volume remaining after normal expiration.
Characteristic of NRDS
Atelectasis. This is because without surfactant, the surface tension of the small alveoli collapse into the large aveoli.
- Lack of surfactant also decreases compliance.
When does surfactant appear?
Around week 24
Wheezing + tachypnea. Hypoxemia causes tachypnea, which drives PCO2 down.
What happens to intrapleural pressure with inspiration?
Becomes more negative than it is at rest or during expiration.
When airway pressure is equal to atmospheric pressure...
This is equilibrium and there is no airflow. ***Volume in the lungs = FRC.
What happens to alveolar PO2 with a PE?
Alveolar PO2 is equal to the PO2 in inspired air.
Blood flow in the systemic vs. pulmonary circulations...
Blood flow in the systemic and pulmonary circulations is nearly equal. Pulmonary flow is slightly less than the systemic flow because about 2% of systemic CO bypasses the lungs.
Resistance in pulmonary circulation
Resistance in the pulmonary circulation is lower than in the systemic circulation.
Compared with the apex of the lung, the base of the lung has...
a higher pulmonary capillary **PCO2
Mean arterial PO2 and PCO2 during exercise...
There is no change in mean arterial PO2 or PCO2. This is because ventilation rate increases to match the increased O2 consumption and CO2 production.
BUT venous pCO2 increases.
Central chemoreceptor location
Medulla. (medullary chemoreceptors).
Peripheral chemoreceptor location
Carotid and aortic bodies
If an area of the lung is not ventilated because of bronchial obstruction, the pulmonary capillary blood serving that area will have a PO2 that is...
Equal to mixed venous PO2. This is because pulmonary blood will NOT equilibriate with alveolar PO2 but will have a Po2 equal to that of mixed venous blood.
What happens with transporting CO2 from tissues to lungs?
CO2 is hydrated to form H+ and HCO3- in RBCs. H+ is buffered inside the RBCs by deoxyhemoglobin, which ACIDIFIES RBCs. HCO3- leaves RBCs in exchange for Cl- and is carried to the lungs in the plasma.
Sits in RBCs and CO2 + H2O H2CO3.
What buffers H+ in RBCs?
Decreased arterial PO2
Causes of hypoxemia
1) high altitude
3) right to left cardiac shunt
Which cause of hypoxemia is associated with an increased AA gradient?
Right-to-left cardiac shunt. This is because the shunt "dilutes" the PO2 of the normally oxygenated blood thus decreasing the arterial O2.
Causes of hypoxemia with normal A-a gradient?
High altitude + hypoventilation
Causes of hypoxemia with increased A-a gradient?
1) V/Q mismatch
2) Diffusion limitation (fibrosis)
3) right-to-left shunt
Why is pH of venous blood only slightly more acidic than the pH of arterial blood?
H+ generated from CO2 and H2O is buffered by deoxyhemoglobin in venous blood.
Function of J (juxtacapillary) receptors
Receptors located in the alveolar walls, close to the capillaries. Engorgement of pulmonarry capillaries such as with left HF stimulates J receptors, which then cause rapid, shallow breathing.
How do you calculate dead space?
Tidal volume x ((arterial PCO2-expired PCO2)/arterial PCO2))
Initial development of lungs and when it happens
Lung bud buds off from distal end of respiratory diverticulum during week 4
embryonic stage events + timeframe
lung bud --> trachea --> mainstem bronchi --> secondary (lobar) bronchi --> tertiary (segmental) bronchi
what do errors in embryonic stage lead to?