Week 9 Ventilators and Airway Monitors Flashcards
Describe possible issues with piston ventilators.
- refill even if a circuit disconnection occurs
- if a circuit leak is present, piston may entrain RA through the leak → diluting oxygen and anesthetic agent
- associated risks
- hypoxemia
- awareness
- Alarm should alert the operator
- associated risks
- positive pressure relief valve prevents excessively high breathing circuit pressure (60 to 80 cm H2O)
Distinguish ICU vents and anesthesia vents.
- ICU ventilators are more powerful allowing for greater inspiratory pressures and tidal volumes
- CO2 absorber - anesthesia vents
- ICU ventilators support more modes of ventilation
- Changing!!
- Gas supplied by the ICU ventilator directly ventilates the patient
-
Anesthesia driving gas never reaches the patient
- 100% O2 in old machines
- Air/100% O2 in newer models
Describe Pressure Support Ventilation as a mode of ventilation.
- aid in normal breathing with a predetermined level of positive airway pressure
- pt spontaneously breathing
- PSV senses patient inspiratory effort (volume or flow) and delivers pressure support
- results in larger TV than the patient would produce on their own
- PSV is useful to support MV and control arterial CO2 for spontaneously breathing patients during maintenance and emergence
How do you calculate the I : E ratio?
- Time spent in inspiration
-
TI = TV / Flow rate
- TV = IBW * 5-7 ml/kg = ____ mL
- Flow rate = 4 - 6 X minute ventilation
- MV = TV X RR
- X 60 seconds
- TE = (60 seconds / RR) - TI
What is the formula for oxygen delivery?
Oxygen delivery = CO x O2 content
Distinguish between ascending and descending bellows.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/317/170/170/a_image_thumb.jpeg?1596035263)
Bellows are classified by direction of bellows movement during _________.
EXPIRATION
How are we going to make sure that our ventilator settings are okay and that we are ventilating adequately?
PEtCO2
Discuss volume as a parameter used to describe ventilation.
- measure of the tidal volume delivered by the ventilator to the patient
- volume of gas patient breaths
- expressed in mls
- expressed in Ls for minute volume
Describe the disadvantage of the descending bellows type ventilator.
These bellows will continue regular upward and downward movement despite patient disconnection: the drive gas pushes the bellows upward during the inspiratory phase, and during the expiratory phase the bellows “fills” with entrained room air instead of the patient’s exhaled gas, because of the weighted bellows. The pressure monitor and the volume monitor may be fooled even if disconnection is complete.
**An essential safety feature of any anesthesia workstation that uses a descending bellows is an integrated CO2 apnea alarm that cannot be disabled while the ventilator is in use.**
Each time you increase FiO2 by _____ you increase PaO2 by _______.
10%; ~50 mmHg
- PaO2 FiO2
- 100 21%
- 150 30%
- 200 40%
- 250 50%
Discuss time as a paramter used to describe ventilation.
- divided into insp and exp periods
- expressed in seconds OR by relation of insp time to exp time expressed as I:E ratio
- used to define the number of respiratory cycles within a given time period
If ventilation is in adequate and we want to increase minute ventilation, in general, will we first increase RR or TV?
(think of Dr. E’s pearl in anesthesia, practical purposes)
- Tidal volume first
- recruit alveoli, not being ventilated as well as when patient is awake with negative pressure ventialtion
- however, must consider pressures as well
Describe features of a piston ventilator.
- use computer controlled stepper motor vs drive gas
- analagous to pushing plunger of syringe
- single circuit
-
less gas used
- great for remote locations
- more accurate TV delievery tied to piston movement
- **However, feedback mechanisms that help maintain stable tidal volume delivery are becoming increasingly more common**
- circuit compliance compensation
- use of inspired tidal volume measurement
Discuss flow rate as a parameter used to describe ventilation.
-
rate at which the gas volume is delivered to the patient
- from the patient connection of the breathing system to the patient
- refers to the volume change/time
- expressed in L/sec or L/min
FR = 4 - 6 X Minute Volume