Transcript Advanced Modes of CMV

Advanced Modes of CMV
RC 270
Pressure Support = mode that
supports spontaneous
breathing
A preset pressure is applied to the
airway with each spontaneous
inspiration
Pressure Support
 Pure assist mode
 Patient determines rate, Vt, and
inspiratory time
 Inspiration is flow cycled
 Most
ventilators flow cycle a pressure
support breath when inspiratory flow drops
to 25% of the peak flow for that inspiration

PB 7200 flow cycles when pressure support
flow drops to 5-10 lpm
Indications/Advantages:
Pressure Support
 Initially used to overcome the increased
W.O.B. when breathing spontaneously
through an E-T tube
 Also may be used during spontaneous
breaths during IMV
 Weaning
 Assisted ventilation (instead of A/C)
 PSVmax
Initial Settings and
Adjustments: Pressure
Support
 To overcome resistance of E-T tube,
start at 5-10 cmH2O
 For PSVMax, set pressure to level that
gives an exhaled Vt of 10-12 ml/kg
Advantages: Pressure
Support
 Supports spontaneous breathing with
decreased W.O.B.(with or without an ET tube)
 Can be done with a face mask
 Usually less barotrauma and
hemodynamic compromise
 Patients like it!
Disadvantage: Pressure
Support
 A leak in the system prevents flow
cycling
 Will
cause a CPAP effect
Pressure Controlled
Ventilation (PCV)
A set pressure is applied to the
airway during inspiration and the
breath time cycles
Pressure Controlled
Ventilation
 Can be used in A/C or control
 Flow tapers – if it drops to zero before
time cycling occurs, the pressure
plateaus
 Besides pressure, RCP also sets rate
and either inspiratory time or I:E ratio
 Vt may vary from breath to breath
Pressure Controlled
Ventilation
 Indications are same as for any type of CMV:
 Apnea
 Acute ventilatory failure
 Impending ventilatory failure
 Acute respiratory failure (Oxygenation failure)
 Often used when volume cycling (volume
control) is causing high airway pressures
 Has been used to ventilate neonates since
the 60s
PCV: Initial Settings and
Adjustments
 Initially choose a pressure (PIP) that gives
desired exhaled Vt
 If switching from volume cycling (volume
control), use a PIP that is less than PIP
during volume cycling
 Adjustment in rate, PIP, and I:E (or inspiratory
time based on ABGs, oximetry, and
capnography

A change in PIP or I:E/insp time will change Vt
PC-IRV: Pressure Control with
Inverse I:E Ratio
Control mode only
Patient is paralyzed
Settings like PCV except for
inverse I:E (gives long insp time)
PC-IRV used in diseases with
high elastic resistance, eg
ARDS
Prolonged insp time helps O2
To increase PaO2: increase rate,
PIP or insp time
To decrease PaCO2: decrease
rate or PIP
Airway Pressure Release
Ventilation (APRV)
Alternating levels of CPAP in a
spontaneously breathing patient
APRV
 Like PC-IRV but patient is breathing
spontaneously and is not paralyzed
 Also used for high elastic resistance
 High CPAP level is applied longer than
low CPAP level
 Is
NOT synchronized with inspiration and
expiration
APRV: Settings and
Adjustments
 Low CPAP usually between 2-10
cmH2O
 High CPAP usually between 10-30
cmH2O
 RCP also sets the time for each CPAP
level
 Low
CPAP is usually only for 1-2 seconds
Bilevel Positive Airway
Pressure (BIPAP)
IPAP + EPAP
Differs from APRV – IPAP only
during inspiration, EPAP only
during expiration
Rate and I:E ratio can also be set
Indications : BIPAP
 Sleep apnea
 Ventilatory Assist without intubation
 Can
be done via face mask
 Often used to keep COPDers from being
tubed and put on A/C
 Popular mode for NIPPV (Non-invasive
Positive Pressure Ventilation)
High Frequency Ventilation
(HFV)
A form of ventilation utilizing high
rates and small Vt that seems to
enhance diffusion of gases into
and out of the lung
History of CMV
HFV should not work based on
classical respiratory physiology!
HFV: High Frequency Jet
Ventilation (HFJV)
 Vt usually 20-150 ml
 Frequency (rate) 60-400 breaths per
minute
 Usually a catheter is inserted via ET
tube or transnasally to apply jet bursts
to airway
 Adjust rate, driving pressure, and insp
time, and FIO2
HFV: High Frequency
Oscillation (HFO)
 Vt between 5-50ml
 Frequency between 400-3000
 Frequency
expressed in Hertz (Hz)
 10 Hz equals 600 breaths per minute
HFO Techniques
HFV (both HFJV and HFO)
 Strict FIO2 and
humidification can
be variable
 Both appear to
cause diffusion to
occur from proximal
airway to alveoli

How does
spontaneous
breathing work?
 Coaxial flow
 Inspiration and
expiration may be
occurring
simultaneously
 HFV seems to
stimulate
mucociliary
clearance
Enough
already!