Inhaled anesthetics Exam 3 Flashcards
What is Boyle’s Law?
At Constant temperature, Pressure and Volume of gas are inversely proportional.
Bellows contract thus increasing circuit pressure → gasses flow from high pressure circuit to low pressure lungs.
What is Fick’s Diffusion Law (as is pertinent to inhaled anesthetics)?
Once air molecules enter alveoli, they move around randomly and begin to diffuse into the pulmonary capillaries.
What factors is diffusion dependent on?
Partial pressure gradient of the gas, Solubility of the gas, Thickness of the membrane.
What is Graham’s Law of Effusion?
Process by which molecules diffuse through pores and channels without colliding. (smaller molecules effuse faster, depends on solubility)
Smaller molecules effuse faster dependent on ________.
solubility
Which diffuses faster CO₂ or O₂? Why?
CO₂ is 20x more diffusible due to solubility despite O₂ weighing less.
If PBrain is greater than PA then what we expect to be occurring?
This means the concentration gradient is moving towards the alveoli away from the brain.
What does the following equation mean? PA ⇌ Pa ⇌ PBrain
This is comparing the partial pressure of volatile gas in the alveoli to the arterial blood to the brain.
What input factors affect the diffusion of volatile gas from the anesthetic machine to the alveoli?
Inspired partial pressure, Alveolar ventilation, Anesthetic system re-breathing, FRC.
Which factors affect the uptake of anesthetic gas from the alveoli to the blood?
Blood:gas partition coefficient, Cardiac output, A-V pressure difference.
How would a low cardiac output affect the diffusion of anesthetic gas from the alveoli to the pulmonary capillary blood?
↓CO = more time to diffuse across the alveolus.
What factors affect the uptake of anesthetic gas from the arterial blood to the brain?
Blood:Brain partition coefficient, Cerebral blood flow, A-V partial pressure difference.
Gas goes from a ____ gradient to a ____ gradient in order to reach a steady state.
high; low
What is the concentration effect?
Higher the PI ⇒ PA reaches PI quicker.
What does FE/FI mean?
FE/FI is the ratio of expired gas to inspired gas.
What concept is this chart conveying?
Concentration Effect: essentially, ↑concentration inspired gas = quicker rate of ↑PA.
What is over-pressurization?
A large increase in PI to offset slow induction from highly soluble volatiles.
What would sustained delivery of over-pressurization result in?
Overdose.
What gas does the second gas effect always apply to?
N₂O (nitrous oxide).
What is the second gas effect as it relates to anesthesia?
Uptake of N₂O accelerates a concurrently administered volatile gas.
How does N₂O create the second gas effect?
Rapid N₂O uptake hyper-concentrates second gas to create a high concentration gradient and increase uptake of second gas.
Describe what is being depicted on the graph below.
This is the second gas effect of N₂O on halothane. Leads to quicker increase in halothane alveolar concentrations.
What cases would nitrous oxide not be utilized in? Why?
Cases with an air-filled cavity. N₂O will diffuse into the cavity and fill it. (extent of damage dependent on the compliance of the cavity).
What specific cases are bad for the usage of N₂O?
Ear & eye, Open belly (stomach, intestines), Lung.
