Respiratory System Flashcards
What happens to PACO2 as minute ventilation increases linearly?
PACO2 decreases asymptotically
What is the most appropriate initial treatment for a patient who has a generalized seizure during hyperbaric oxygen therapy?
discontinue inhaled oxygen
What factors can reduce hypoxic pulmonary vasoconstriction during one lung ventilation?
- ACE inhibitors, calcium channel blockers, nitroglycerin, sodium nitroprusside, acetazolamide, corticosteroids, nitric oxide, prostacyclin
- hypocapnea
- volatile anesthetics
What factors enhance hypoxic pulmonary vasocontriction?
- hypercapnea
- catecholamines, phenylephrine
What anesthetic agents do no affect hypoxic pulmonary vasocontriction?
propofol
nitrous oxide
What is the effect of dexmedetomidine on the hypercapnic ventilatory response?
no effect
What primarily determines the resting tone of airway smooth muscle?
parasympathetic tone
What is the alveolar gas equation?
PAO2 = FiO2 (Patm - pH2O) - PaCO2/0.8
Patm ~ 760 mmHg
pH2O ~ 47 mmHg
What is the oxygen content equation?
CaO2 = (SaO2 x Hgb x 1.34) + (0.003 x PaO2)
** mL of O2 per 100 mL blood **
What happens to PaCO2 during apneic oxygenation?
increases by 6 mmHg in the first minute and 3 mmHg in each subsequent minute
What is the P50 of oxygen binding to hemoglobin?
SaO2 50% -> PaO2 27 mmHg
What does a typical blood gas show in pulmonary embolism?
hypoxemia and respiratory alkalosis
What are the pulmonary complications of ankylosing spondylitis?
pulmonary fibrosis
restrictive lung disease
What are the approximate FiO2s delivered by nasal cannula? Simple face mask? Venturi mask? Non-rebreather?
2L nasal cannula ~25%
6L nasal cannula ~ 40%
simple face mask ~50%
Venturi mask - adjustable
non-rebreather ~90%
By how much does hemidiaphragmatic paralysis decreased indices of pulmonary function?
~25%
What is the intrapleural pressure at normal end expiration in a healthy person?
-5 cmH2O
Where in the lungs are ventilation and perfusion maximal?
Both are maximal at the base
What are the non-cardiogenic, modifiable causes of pulmonary hypertension?
hypoxia
hypercarbia
acidosis
What part of the brainstem coordinates inspiration? Expiration?
dorsal medullary center: inspiration
ventral medullary center: expiration
Which receptors mediate hypoxic respiratory drive?
chemoreceptors in the aortic arch and carotid body
Why shouldn’t you give a patient with severe COPD too much supplementary oxygen?
It will interfere with HPV and worsen V/Q matching
How does blood in the ventricles increase respiratory rate in patients with TBI/hemorrhage?
Blood provides H+ ions and lower CSF pH
Through what mechanism can intubation cause bronchospasm?
direct parasympathetic activation
Is right heart failure more common in chronic bronchitis or emphysema?
chronic bronchitis
(causes elevated PA pressures earlier in the disease)
What are the most common EKG changes with massive PE?
tachycardia and ischemic changes (TWIs or ST depressions) in anterior prechordial leads (esp. V1-V2)
*S1Q3T3 is very specific for right heart strain from PE, but rarely seen*
With regard to variable intrathoracic and extrathoracic airway obstructions, which causes more obstruction to flow during inspiration? During expiration?
variable extrathoracic obstructions block flow more during inspiration
variable intrathoracic obstructions block flow more during expiration
What are the flow-volume loops like for variable intrathoracic and extrathoracic obstructions? Fixed obstruction?
