principles of mechanical ventilation ret 2284 module 3.0 modes of ventilation
TRANSCRIPT
Principles of Mechanical Ventilation
RET 2284 Module 3.0 Modes of Ventilation
Modes of Ventilation
Mode Description of a breath type and the timing of
breath delivery Terms or acronyms used to describe the way a
ventilator performs in a particular situation; often invented by physicians, therapists, or manufacturers
Basically there are three breath delivery techniques used with invasive positive pressure ventilation CMV – controlled mode ventilation SIMV – synchronized Spontaneous modes
Modes of Ventilation
CMV Continuous Mandatory Ventilation
All breaths are mandatory and can be volume or pressure targeted
Controlled Ventilation – when mandatory breaths are time triggered
Assist/Control Ventilation – when mandatory breaths are either time triggered or patient triggered
Modes of Ventilation
CMV Continuous Mandatory Ventilation
Controlled Ventilation – when mandatory breaths are time triggered Mandatory breath – ventilator determines the start
time (time triggered) and/or the volume or pressure target
Modes of Ventilation
CMV Controlled Ventilation
Appropriate when a patient can make no effort to breathe or when ventilation must be completely controlled Drugs Cerebral malfunctions Spinal cord injury Phrenic nerve injury Motor nerve paralysis
Modes of Ventilation
CMV Controlled Ventilation
In other types of patients, controlled ventilation is difficult to use unless the patient is sedated or paralyzed with medications Seizure activity Tetanic contractions Inverses I:E ratio ventilation Patient is fighting (bucking) the ventilator Crushed chest injury – stabilizes the chest Complete rest for the patient
Modes of Ventilation
CMV Controlled Ventilation
Adequate alarms must be set to safeguard the patient E.g., disconnection
Sensitivity should be set so that when the patient begins to respond, they can receive gas flow from the patient
Do not lock the patient out of the ventilator!
Modes of Ventilation
CMV Assist/Control Ventilation
A time or patient triggered CMV mode in which the operator sets a minimum rate, sensitivity level, type of breath (volume or pressure)
The patient can trigger breaths at a faster rate than the set minimum, but only the set volume or pressure is delivered with each breath
Modes of Ventilation
CMV Assist/Control Ventilation
Indications Patients requiring full ventilatory support Patients with stable respiratory drive
Advantages Decreases the work of breathing (WOB) Allows patients to regulate respiratory rate Helps maintain a normal PaCO2
Complications Alveolar hyperventilation
Modes of Ventilation
CMV Volume Controlled –
CMV Time or patient triggered,
volume targeted, volume cycled ventilation
Graphic (VC-CMV) Time-triggered, constant
flow, volume-targeted ventilation
Modes of Ventilation
CMV Volume Controlled –
CMV Time or patient triggered,
volume targeted, volume cycled ventilation
Graphic (VC-CMV) Time-triggered,
descending-flow, volume-targeted ventilation
Modes of Ventilation
CMV Pressure Controlled – CMV
PC – CMV (AKA – Pressure control ventilation - PCV)
Time or patient triggered, pressure targeted (limited), time cycled ventilation
The operator sets the length of inspiration (Ti), the pressure level, and the backup rate of ventilation
VT is based on the compliance and resistance of the patient’s lungs, patient effort, and the set pressure
Modes of Ventilation
CMV Pressure Controlled – CMV
Note inspiratory pause
Modes of Ventilation
CMV Pressure Controlled – CMV
Note shorter Ti
Modes of Ventilation
CMV Pressure Controlled – CMV
Airway pressure is limited, which may help guard against barotrauma or volume-associated lung injury Maximum inspiratory pressure set at 30 – 35 cm
H2O Especially helpful in patients with ALI and ARDS
Allows application of extended inspiratory time, which may benefit patients with severe oxygenation problems
Usually reserved for patient who have poor results with a conventional ventilation strategy of volume ventilation
Modes of Ventilation
CMV Pressure Controlled – CMV
Occasionally, Ti is set longer than TE during PC-CMV; known as Pressure Control Inverse Ratio Ventilation Longer Ti provides better oxygenation to some
patients by increasing mean airway pressure Requires sedation, and in some cases paralysis
Modes of Ventilation
IMV and SIMV Intermittent Mandatory Ventilation – IMV
Periodic volume or pressure targeted breaths occur at set interval (time triggering)
Between mandatory breaths, the patient breathes spontaneously at any desired baseline pressure without receiving a mandatory breath Patient can breathe either from a continuous
flow or gas or from a demand valve
Modes of Ventilation
IMV and SIMV Intermittent Mandatory Ventilation – IMV
Indications Facilitate transition from full ventilatory support
to partial support
Advantages Maintains respiratory muscle strength by
avoiding muscle atrophy Decreases mean airway pressure Facilitates ventilator discontinuation – “weaning”
Modes of Ventilation
IMV and SIMV Intermittent Mandatory Ventilation – IMV
Complications When used for weaning, may be done too quickly
and cause muscle fatigue Mechanical rate and spontaneous rate may
asynchronous causing “stacking” May cause barotrauma or volutrauma
Modes of Ventilation
IMV and SIMV Synchronized IMV
Operates in the same way as IMV except that mandatory breaths are normally patient triggered rather than time triggered (operator set the volume or pressure target)
As in IMV, the patient can breathe spontaneously through the ventilator circuit between mandatory breaths
Modes of Ventilation
IMV and SIMV Synchronized IMV
At a predetermined interval (respiratory rate), which is set by the operator, the ventilator waits for the patient’s next inspiratory effort
When the ventilator senses the effort, the ventilator assists the patient by synchronously delivering a mandatory breath
Modes of Ventilation
IMV and SIMV Synchronized IMV
If the patient fails to initiate ventilation within a predetermined interval, the ventilator provides a mandatory breath at the end of the time period
Modes of Ventilation
IMV and SIMV Synchronized IMV
Indications Facilitate transition from full ventilatory support
to partial support
Advantages Maintains respiratory muscle strength by
avoiding muscle atrophy Decreases mean airway pressure Facilitates ventilator discontinuation – “weaning”
Modes of Ventilation
IMV and SIMV Synchronized IMV
Complications When used for weaning, may be done too quickly
and cause muscle fatigue
Modes of Ventilation
Spontaneous Modes Three basic means of providing support
for continuous spontaneous breathing during mechanical ventilation
Spontaneous breathing
CPAP
PSV – Pressure Support Ventilation
Modes of Ventilation
Spontaneous Modes Spontaneous breathing
Patients can breathe spontaneously through a ventilator circuit; sometimes called T-Piece Method because it mimics having the patient ET tube connected to a Briggs adapter (T-piece)
Advantage Ventilator can monitor the patient’s breathing and
activate an alarm if something undesirable occurs
Disadvantage May increase patient’s WOB with older ventilators
Modes of Ventilation
Spontaneous Modes CPAP
Ventilators can provide CPAP for spontaneously breathing patients Helpful for improving
oxygenation in patients with refractory hypoxemia and a low FRC
CPAP setting is adjusted to provide the best oxygenation with the lowest positive pressure and the lowest FiO2
Modes of Ventilation
Spontaneous Modes CPAP
Advantages Ventilator can
monitor the patient’s breathing and activate an alarm if something undesirable occurs
Modes of Ventilation
Spontaneous Modes PEEP (Positive End Expiratory Pressure)
“According to its purest definition, the term PEEP is defined as positive pressure at the end of exhalation during either spontaneous breathing or mechanical ventilation. However, use of the term commonly implies that the patient is also receiving mandatory breaths from a ventilator.” (Pilbeam)
PEEP becomes the baseline variable during mechanical ventilation
Modes of Ventilation
Spontaneous Modes PEEP
Helps prevent early airway closure and alveolar collapse and the end of expiration by increasing (and normalizing) the functional residual capacity (FRC) of the lungs
Facilitates better oxygenation
NOTE: PEEP is intended to improve oxygenation, not to provide ventilation, which is the movement of air into the lungs followed by exhalation
Modes of Ventilation
Spontaneous Modes Pressure Support Ventilation – PSV
Patient triggered, pressure targeted, flow cycled mode of ventilation
Requires a patient with a consistent spontaneous respiratory pattern
The ventilator provides a constant pressure during inspiration once it senses that the patient has made an inspiratory effort
Modes of Ventilation
Spontaneous Modes PSV
Modes of Ventilation
Spontaneous Modes PSV
Indications Spontaneously breathing patients who require
additional ventilatory support to help overcome WOB, CL, Raw Respiratory muscle weakness
Weaning (either by itself or in combination with SIMV)
Modes of Ventilation
Spontaneous Modes PSV
Advantages Full to partial ventilatory support Augments the patients spontaneous VT
Decreases the patient’s spontaneous respiratory rate
Decreases patient WOB by overcoming the resistance of the artificial airway, vent circuit and demand valves
Allows patient control of TI, I, f and VT
Modes of Ventilation
Spontaneous Modes PSV
Advantages Set peak pressure Prevents respiratory muscle atrophy Facilitates weaning Improves patient comfort and reduces need for
sedation May be applied in any mode that allows
spontaneous breathing, e.g., VC-SIMV, PC-SIMV
Modes of Ventilation
Spontaneous Modes PSV
Disadvantages Requires consistent spontaneous ventilation Patients in stand-alone mode should have back-
up ventilation VT variable and dependant on lung
characteristics and synchrony Low exhaled E Fatigue and tachypnea if PS level is set too low
Modes of Ventilation
Spontaneous Modes Flow Cycling During PSV
Flow cycling occurs when the ventilator detects a decreasing flow, which represents the end of inspiration
This point is a percentage of peak flow measured during inspiration PB 7200 – 5 L/min Bear 1000 – 25% of peak flow Servo 300 – 5% of peak flow
No single flow-cycle percent is right for all patients
Modes of Ventilation
Spontaneous Modes Flow Cycling During
PSV Effect of changes in
termination flow
A: Low percentage (17%)
B: High percentage (57%)
Newer ventilators have an adjustable flow cycle criterion, which can range from 1% - 80%, depending on the ventilator
Modes of Ventilation
Spontaneous Modes PSV during SIMV
Spontaneous breaths during SIMV can be supported with PSV (reduces the WOB)
PCV – SIMV with PSV
Modes of Ventilation
Spontaneous Modes PSV during SIMV
Spontaneous breaths during SIMV can be supported with PSV
VC – SIMV with PSV
Modes of Ventilation
Spontaneous Modes PSV
NOTE: During pressure support ventilation (PSV), inspiration ends if the inspiratory time (TI) exceeds a certain value. This most often occurs with a leak in the circuit. For example, a deflated cuff causes a large leak. The flow through the circuit might never drop to the flow cycle criterion required by the ventilator. Therefore, inspiratory flow, if not stopped would continue indefinitely. For this reason, all ventilators that provide pressure support also have a maximum inspiratory time.
Modes of Ventilation
Spontaneous Modes PSV
Setting the Level of Pressure Support Goal: To provide ventilatory support
Spontaneous tidal volume is 10 – 12 mL/Kg of ideal body weight
Maintain spontaneous respiratory rate <25/min
Goal: To overcome system resistance (ET Tube, circuit, etc.) in the spontaneous or IMV/SIMV mode Set pressure at (PIP – Pplateau) achieved in a
volume breath or at 5 – 10 cm H2O
Modes of Ventilation
Spontaneous Modes PSV
Exercise: Using the PIP and the PPlateau from the pressure waveform below, recommend a pressure support setting for this patient (patient is in VC-SIMV mode)
35
25
Answer: 10 cm H2O
Modes of Ventilation
Spontaneous Modes PSV - The results of your work
35 cm H2O
10 cm H2O
Modes of Ventilation
Spontaneous Modes Bilevel Positive Airway Pressure (BiPAP)
An offshoot of PEEP/CPAP therapy Most often used in NPPV AKA
Bilevel CPAP Bilevel PEEP Bilevel Pressure Support Bilevel Pressure Assist Bilevel Positive Pressure Bilevel Airway Pressure
Modes of Ventilation
Spontaneous Modes Bilevel Positive Airway Pressure (BiPAP)
Commonly patient triggered but can be time triggered, pressure targeted, flow or time cycled
The operator sets two pressure levels IPAP (Inspiratory Positive Airway Pressure)
IPAP is always set higher than EPAP Augments VT and improves ventilation
EPAP (Expiratory Positive Airway Pressure) Prevents early airway closure and alveolar collapse
at the end of expiration by increasing (and normalizing) the functional residual capacity (FRC) of the lungs
Facilitates better oxygenation
Modes of Ventilation
Spontaneous Modes Bilevel Positive Airway Pressure (BiPAP)
The operator sets two pressure levels IPAP EPAP
NOTE: The pressure difference between IPAP and EPAP is pressure support
Modes of Ventilation
Questions?