Anesthesia machine 6 Flashcards
Continuous positive airway pressure is when
a continuous amount of pressure is applied to the breathing circuit throughout the respiratory cycle
CPAP has two benefits:
it augment’s the patient’s spontaneous breath and it reduces airway collapse during expiration
What is biphasic positive airway pressure (BiPAP)?
two levels of pressure are set
P1= inspiratory positive airway pressure (think pressure support for a spontaneous breath)
P2= expiratory positive airway pressure (think CPAP during exhalation)
the patient receives one pressure during inhalation and a different pressure during exhalation
BIPAP is useful for
the patient with COPD or when CPAP isn’t quite enough
Airway pressure release ventilation can be used for
spontaneous ventilation
like BiPAP but there is a high level of CPAP throughout most of the respiratory cycle
-the high level of pressure is released at preset intervals to facilitate exhalation
Airway pressure release ventilation is useful in patients with
ARDS
What is inverse ratio ventilatioN?
the respiratory cycle is divided into inhalation and exhalation and the I:E ratio determines how much time is spent in each part
IRV reverses
the typical ratio (most modes have longer exhalation than inhalation) and allocates more time to inspiration
IRV requires
a paralyzed and sedated patient (no spontaneous ventilation)
IRV has a risk of
dynamic hyperinflation (auto-peep or breath stacking)
IRV is useful in the patients
with a small FRC or in the patient with ARDs
What is high frequency ventilation?
delivers a tidal volume below anatomic dead space in conjunction with a very high respiratory rate
High frequency ventilation allows gas transport by a combination of
molecular diffusion
coaxial flow
high-velocity flow
Types of high-frequency ventilation icnlude
high-frequency oscillation, high-frequency jet ventilation, and high-frequency percussive ventilation
At what pH does the ethyl violet change to purple?
a. 7.5
b. 8.6
c. 10.3
d. 12.1
c. 10.3
Carbon dioxide absorbents remove
exhaled carbon dioxide from the breathing circuit
Without carbon dioxide absorption,
closed and semi-closed anesthesia circuits would not be possible
The size of the absorbent granule must strike a balance between
surface area (absorptive capacity) and airflow resistance (work of breathing)
The best balance of absorbent granule is achieved when _________ are used
4-8 mesh granules
The two major problems that can occur with carbon dioxide absorbents include:
exhaustion- it’s no longer able to neutralize carbon dioxide
desiccation- it’s too dry
An indicator dye (such as ethyl violet) turns purple when
soda lime is exhausted; there’s no color change to signify dessication
Desiccated soda lime increases the production of
carbon monoxide in the presence of halogenated agents (desflurane> isoflurane> sevoflurane) and compound A in the presence of sevoflurane
Methods to reduce carbon monoxide and compound A production include
use a low FGF
turn off the FGF between cases
change all absorbent canisters at one time
change the canisters when the indicator dye signals exhaustion
change the canisters if you’re unsure about the level of hydration
__________ in soda lime is a strongly alkaline compound that’s irritating to skin and mucous membranes.
Sodium hydroxide
The addition of _________ to soda lime provides hardness and minimizes dust production
silica
What is the reaction of CO2 with soda lime?
- Carbon dioxide + water–> carbonic acid
- carbonic acid + 2 sodium hydroxide–> sodium carbonate + 2 water+ heat
- Sodium carbonate + calcium hydroxide–> calcium carbonate + 2 sodium hydroxide
The best indicator of expired soda lime is the
presence of inspired Co2 in the breathing circuit
If you’re not able to replace a CO2 absorbent right away, you should
increase your fresh gas flows
Carbon monoxide can cause
carboxyhemoglobinemia
When compared to soda lime, what factor is increased with the use of calcium hydroxide lime?
a. carbon monoxide
b. frequency of replacement
c. CO2 absorption capacity
d. fire risk
b. frequency of replacement
Benefits of calcium hydroxide lime include
no carbon monoxide production
very little or no compound A production
lower risk of fire when compared to soda lime
Drawbacks of calcium hydroxide lime include
lower CO2 absorption capacity
requires more frequent replacement
higher cost
Calcium hydroxide lime does not contain ________ such as sodium hydroxide or potassium hydroxide
strong bases
What is the calcium hydroxide lime equation?
- carbon dioxide + water–> carbonic acid
- carbonic acid + 2 calcium hydroxide–> calcium carbonate + 2 water + heat
While a patient is ventilating spontaneously with an endotracheal tube, you notice that a fresh gas flow of 10L/min is required to fill the breathing bag and determine that the scavenger is malfunction. Which statement must be true?
a. the negative pressure relief valve has failed
b. the positive pressure relief valve has failed
c. there is an open scavenging system
d. there is a passive scavenging system
a. the negative pressure relief valve has failed
The scavenger removes
excess gas from the breathing circuit and minimizes environmental exposure to waste anesthetic gas
The scavenger system has five components:
- gas collection assembly
- transfer tubing
- interface (open or closed)
- gas disposal tubing
- gas disposal system
The scavenger can be
active or passive
During spontaneous ventilation, the __________controls the amount of gas that remains in the circuit and the amount that is released to the scavenger
APL valve
During mechanical ventilation, the ___________ determines the amount of gas that remains in the circuit and the amount that is released to the scavenger.
ventilator spill valve
The most critical component of the scavenger is the
interface
Removal of too much gas would create __________________, while removal of too little gas could increase the risk of _________
negative pressure in the circuit; barotrauma
To maintain a constant pressure inside the breathing circuit, the scavenger must only remove
an amount of gas equal to fresh gas flow minus the volume of gas lost due to the patient’s oxygen consumption
The gas collecting assembly
collects waste gas from the breathing circuit
The gas collecting assembly is located at
the APL valve and the ventilator spill valve
Transfer tubing directs
collected gas to the interface
With an open system too much suction
entrains room air into the scavenger
With an open system, too little suction
vents scavenged gas into the operating room
An open system has a higher risk of
exposing OR personnel to waste gas
An open system removes the risk of
barotrauma or removal of fresh gas from the breathing circuit
An open system is open to
the atmosphere
An open system can only be used
with active systems (a system that is connected to suction)
A closed system communicates to the
atmosphere with pressure valves
