Mechanical Ventilation Flashcards
goals of mechanical ventilation
1: maintain alveolar ventilation
2: correct hypoxemia
3: decrease work of breathing
what controls the breath?
1: pressure: flow is not constrained to a preset value, allows for better pt-ventilator synchronization
2: volume: more stable minute ventilation
3: flow
parts of breath
start=trigger
sustains=control variable
stops=cycle
in-between=baseline
triggers
based on the frequency set. It becomes time for the pt to receive a breath
pressure
flow
volume
pressure trigger
the patient creates enough negative pressure to initiate a breath
flow trigger
the ventilator constantly measures the flow of the inspiratory and expiratory sides of the ventilator.
when he expiratory side shows a decrease in flow, the ventilator initiates a breath
limit
a preset level that must be reached before the breath will end.
reaching this level does no necessarily end the breath
cycle
ends inspiration and begins expiration pressure volume flow time
baseline=expiration
pressure-most practical
if atmospheric pressure is 0, the baseline is measured from 0
positive end expiratory pressure (PEEP) is a baseline pressure above 0
PEEP
positive end expiratory pressure
baseline pressure above 0
improves oxygenation by opening or holding open the lung alveoli preventing collapse
ventilation mode
combination of breathing pattern, control type and control strategy
breath types (patterns)
mandatory
spontaneous
assisted
supported
mandatory breath type
=ventilator sets the start time and control variable (pressure or volume)
spontaneous breath type
=pt sets start time and tidal volume
assisted breath type
mandatory breath that is patient initiated
supported breath type
spontaneous breath that has a pressure greater than baseline
tidal volume
=volume of air that moves in and out of the lungs for each breath
minute volume
=volume of air breathed in 1 minute
FiO2
=fraction of inspired oxygen expressed as the percentage of oxygen being breathed
I:E ratio
=the ratio of inspiratory time to expiratory time
sensitivity
=a measure of the amount of effort to trigger a breath
peak inspiratory pressure (PIP)
=the highest pressure produced during inspiration
plateau pressure
=pressure reflected on the ventilator during an inspiratory pause… after inspiration is complete, but before expiration has begun
auto PEEP
spontaneous development of PEEP, usually due to insufficient expiratory time
rise time, flow acceleration %, or pressure slope
=terms that indicate the speed which gas flows to deliver a breath
adjustment of the rise time can improve pt comfort
promote ventilator/pt synchrony
decrease work of breathing
common ventilation modes
1: A/C (CMV)
2: IMV (intermittent mandatory ventilation)
3: SIMV (synchronized IMV)
4: spontaneous
A/C ventilation
- AKA CMV (continuous mandatory ventilation)
- all mandatory breaths set to be delivered at a minimum rate, sensitivity level and control variable (pressure or volume)
- the pt can initiate assisted breathes and breathe at a faster rate, but the preset pressure or volume will be delivered
-provides pt with max ventilator support
SIMV ventilation
=synchronized intermittent mandatory ventilation
- all mandatory breaths set to be delivered at a min rate, sensitivity level, and control variable (pressure or volume)
- the pt can breathe spontaneously between mandatory breaths at their own tidal volume and rate
- positive pressure can be delivered during spontaneous breathes by adding pressure support or tubing compensation
- allows for respiratory muscle use preventing atrophy
- the negative pressure generated by spontaneous breaths allows for improved blood return to the heart
spontaneous ventilation
- all breaths are determined by the pt
- positive pressure can be added to support breaths
- the pt must have an intact respiratory drive
- evaluates pt’s ability to breathe independently while ventilating parameters are measured and alarms available
- various support breaths can be added
PEEP vs. CPAP
PEEP: positive end expiratory pressure
-an adjunct to mechanical ventilation
CPAP: continuous positive airway pressure
- measurement of baseline pressure during spontaneous ventilation
- can be administered non-invasively with a face mask
- both are a measurement of baseline pressure
- both improve oxygenation through the same mechanism
additional modes of ventilation
1: bilevel
2: pressure regulated volume control (PRVC)
bilevel
- pressure controlled breaths with a set rate, that determines I:E ratio, and a baseline pressure
- inspiratory pressure=high PEEP
- baseline pressure (PEEP)= low PEEP
- the pt can initiate spontaneous breaths
- pt can assist breaths
-improves patient/ventilator synchrony and reduces the need for sedatives or paralytics during PCV
APRV
airway pressure release ventilation
PRVC
pressure regulated volume control
pressure control with a targeted tidal volume
types of supported breaths
-can only be applied to spontaneous breaths
pressure support
tubing compensation
pressure support
- preset pressure delivered with each spontaneous breath
- estimated to overcome artificial airway resistance
tubing compensation (TC)
- type and size of airway is entered into the ventilator
- using flow and airway calculations the pt is given enough pressure support to only overcome tube resistance
- simulates spontaneous respirations w/out an airway present
alarms
properly set and functioning alarms are essential for the safe operation of any mechanical ventilator
it is important for the licensed care professional to be aware of proper corrective actions to take with each type of alarm
basic alarms
sound when patient becomes disconnected or develops a significant leak
sound when the pressure in the circuit exceeds a specified level
high pressure alarms
sounds when the pressure in the circuit has exceeded the set level
- evaluatie the need for suction
- tube biting
- reposition pt’s head
- evaluate need for sedation
- consult your respiratory care practitioner
low inspiratory pressure alarm
inspiratory pressure falls below set level
- look at your patient: chest rise, color, SpO2
- check for disconnect or major leak
- if ventilation is inadequate, bag the patient and call your respiratory care practitioner
low exhaled tidal volume alarm
sounds the the pt’s tidal volume falls below set level
treat the same as low inspiratory pressure alarm
low inhaled minute volume alarm
sounds when the pt’s minute volume falls below set level
treat the same as low inspiratory pressure alarm
apnea alarm
sounds when a specified amount of time has passed without the ventilator sensing a spontaneous or mandatory breath
- may need to stimulate the pt. if respirations are still inadequate, bag patient and contact respiratory care practitioner
- most ventilators have clinician set apnea parameters that should ventilate the pt when apnea is sensed
silencing alarms
should only be done judiciously, if at all.
once an alarm is silenced, the clinician must continuously monitor the adequacy of ventilation by evaluating chest excursions, SpO2, heart rate and general appearance of the pt.
failure to ensure adequate ventilation and oxygenation can result in anoxic brain injury and death. never silence an alarm and leave the pt’s room
