MCQ's: Breathing Systems Flashcards
What type of breathing system most efficient for spont. breathing?
Mapleson A - Magill
How much FGF needed to work for Mapleson A?
Will work with minimal rebreathing at 70% of minute volume in spontaneous ventilation.
How does water affect soda lime efficiency?
Water is generated by the overall reaction of CO2 with soda lime but it’s presence or absence does not influence performance of the compound.
What does Bain’s system require to prevent rebreathing?
The Bain system (a Mapelson D variant) requires a FGF 2-3x minute ventilation to prevent rebreathing.
When will the volatile concentration not equate with the dial on anaesthetic machines?
The delivered volatile concentration is, in practice, rarely the same as the dial setting but it cannot exceed it except in the few moments after the vaporiser is dramatically turned down or switched off and the system is re-equilibrating.
In the circle system with a FGF <1 L (N2O:O2=66:34), will FIO2 in the circle increase or decrease over time?
In low flow operation of the circle, particularly where the oxygen volume supplied falls towards or below metabolic requirements, the FiO2 will steadily fall and the circle will empty;
N2O rapidly equilibrates and so uptake of N2O will not exceed that of oxygen so increase in oxygen concentration does not result.
NITROUS OXIDE: Cylinder color? Safely administered via a...? Pseudo-critical temperature? Inert gas? MAC?
Cylinder color - French blue
Safely administered - via a Quantiflex mixer which allows a full range oxygen/nitrous oxide mixtures to be administered from 21-100% oxygen so avoiding accidental hypoxic mixtures.
Pseudo-crit: none, only for mixed gases like Entonox.
Inert gas? NO, at high temps can dissociate to an avid oxidant.
MAC - 105% cannot be used as anaesthetic purely, without O2.
Activated charcoal in Cardiff Aldsorber:
- effective at absorbing which volatile agent?
- effect on respiratory resistance?
- how can it be reactivated?
- change as it absorbs?
- Isoflourane
- Low resistance device
- Reactivated by heating to remove adsorbed agents
- is no indicator dye; the only change the device undergoes during use is a small and gradual increase in mass as volatile substances are adsorbed onto the granules.
Contents of soda lime cannister? How much is filled?
The principal ingredient in soda-lime is calcium hydroxide with others including sodium hydroxide (3%) and water (20%).
When packed will be 50% filled with granules
Circle system minimum FGF requirements?
A fresh gas flow of at least 2/3 of the minute volume is required.
Due to the ability to largely recycle gases and a lack of leaks, modern circle systems can sustain very low flows; in a fully closed configuration, total gas flow can be reduced to 100% oxygen at a rate equivalent to the metabolic requirements of the patient (200-300ml/min).
What is the Bain system derived from?
Coaxial of Mapleson D
Whats the maximum size Bains circuit can be?
5.4 meters in length
Which part of the tubes do inhaled and exhaled gases pass through in the bains circuit?
Inhaled in the outer tube,
Exhaled in the inner tube.
In what setting is Bains circuit most efficient?
Most efficient in controlled ventilation.
