30/01/2012&
Aims&and&objec5ves&
The&Basics&of&Mechanical&
Ven5la5on&
January&2012&
Why&we&ven5late&people&
Terms,&acronyms&and&other&confusing&things&
Basic&ven5lator&seFngs&/modes&
Those&wavy&lines&they&ask&you&about&in&the&
exam&
•  This&is&NOT&an&encyclopedic&lecture&on&
complex&ven5la5on&!&
•
•
•
•
1&
30/01/2012&
Confusing&screens&
Why&do&we&use&mechanical&ven5la5on?&
•  Respiratory&failure&
How&do&we&normally&breathe?&
Physiological&=&nega5ve&pressure&ven5la5on&
•  IntraN&&&postNopera5ve&
•  Intubated&cri5cally&ill&pa5ents&(sepsis,&shock,&
neuro,&airway,&etc..)&
&
Invasive&mechanical&ven5la5on&eliminates&the&metabolic&cost&of&
breathing&(i.e.&!&VO2)&
&
Hayek&Oscillator&
2&
30/01/2012&
Early&intensive&care&units&&
How&do&most&ven5lators&work..?&
Posi5ve&pressure:&
–  NonNphysiological&
–  Inflammatory&response&
–  Barotrauma&
–  Uncomfortable&
The&“Iron%lung”&
Airway&devices&
Physiology&of&ven5la5on&
The-goal-of-ven1la1on-is-to-maintain-normal-PaO2-and-PaCO2Minute-ven1la1on-(VE):• Minute&volume&=&Resp&rate&x&5dal&volume&(VT)&
• Total&volume&of&gas&exhaled&per&minute&(“normal”&=&80N100&ml/kg)&
• Minute&volume&comprised&of&two&factors:&
•  Alveolar&ven5la5on&(VA)&
•  Dead&space&ven5la5on&(VD)&
• VD/VT&=&0.33&
&
Respira1on-in-the-cri1cally-ill:• Increased&CO2&produc5on&
•  Pyrexia,&sepsis&&&inflamma5on,&&
• Increased&VD&(V/Q'mismatch)&
•  Atelectasis,&pneumonia,&ARDS&&&pulmonary&embolism&
3&
30/01/2012&
Components&of&an&ar5ficial&breath&
cle
Cy
Trigger-
Inspira5on&(ac/ve)&
Expira5on&(passive)&
Triggering&(exp4insp)&
Cycling&(insp4exp)&
Inspira5on&:&expira5on&(I:E)&ra5o&
Posi5ve&endNexpiratory&pressure&(PEEP)&
-
•
•
•
•
•
•
&
Volume&control&ven5la5on&
Pressure&
Volume&
Flow&
Tidal&volume&preset&(e.g.&500ml)&
8N10&ml/kg&is&fine&(ideal'body'weight)&
Less&in&‘damaged’&lungs&(6N8&ml/kg)&
Airway&pressure&will&vary&–&
compliance'
•  Set&high&airway&pressure&alarms&(e.g.&
30&cmH2O)&
•
•
•
•
&
&
4&
30/01/2012&
Pressure&control&ven5la5on&
•  Inspiratory&pressure&preset&
(e.g.&15&cmH2O)&
•  Tidal&volume&will&vary&
•  CHECK&TIDAL&VOLUME&
&
5&
30/01/2012&
Triggering&
Cycling&
The&parameter&chosen&to&ini5ate&a&breath&and&
cycle&to&inspira5on:&
&
•  Time:&preNset&frequency&(mandatory&vent)&
•  Pressure:&to&detect&spontaneous&breaths&
(N0.5N2.0&cmH2O)&&
•  Flow:&to&detect&spontaneous&breaths&&
OP 4
Parameter&used&to&dictate&the&end&of&the&
inspiratory&phase,&cycling&to&expira5on:&
•  Time-:-mandatory&vent;&set&insp&5me&(Ti)&
•  Flow:&in&pressure&support;&preNdetermined&%&
of&peak&insp&flow&(e.g.&25%)&
•  Volume:&when&set&volume&reached,&no&end&
insp&pause&
How to use the 840 ventilator
•
TH:TL determines the ratio of the high PEEP time interval to the
low PEEP time interval for BiLevel breaths.
•
TLrepresents the time interval for the low PEEP level (PEEPL).
Follow these steps to view or change the timing variable that is
held constant during respiratory rate changes:
I:E&ra5o&(5me&cycled)&
1
2
•  Mandatory&ven5la5on&
&
•  Alter&inspiratory&5me&(Ti)&
Touch VENT SETUP.
Touch CONTINUE. A graphic of the breath timing bar appears
in the lower screen, with a lock icon above each of the three
timing variables (Figure 4-4).
8-00204
TI or TH
I:E or
TH:TL
TE or TL
Figure 4-4. TI (or TH) selected as the constant during rate change
3
Touch the lock icon of the timing variable that you want to
remain constant when the respiratory rate setting changes.
The lock icon of your selection should now be a closed lock, as
it appears above the TI/TH timing variable in Figure 4-4.
•  RR&=&10&and&Ti&=&2&seconds…&&
•  Te&will&be&4&seconds&and&I:E&=&1:2&
In addition, the current value of your selected timing variable
is highlighted within the breath timing graphic, and both this
variable name and its current value are displayed in a
highlighted box under the ventilator control parameter PC.
4
Turn the knob to set the value of your constant timing
variable.
5
Review the selected timing variable and its value. Make
changes if necessary, then press ACCEPT.
•  ARDS:&1:1,&2:1,&3:1&(remember&PCO2)&
840 Ventilator System Operator’s Manual
Pressure&or&volume&control??&
Take&your&pick….&
•  Volume:&shortNterm,&
healthy&lungs,&constant&MV&
•  Pressure:&longNterm,&
reduced&airway&pressure,&
variable&MV&
4-075609-00 Rev. G (10/06)
OP 4-16
6&
30/01/2012&
What&is&PEEP&?&
•  S5ck&your&head&out&of&a&car&window&
•  Raised&baseline&respiratory&pressure&
•  Physiological&PEEP&is&around&5&cmH2O;&
resistance&of&expiratory&airflow&through&gloFs&
•  When&intubated,&loss&of&physiological&PEEP&
provided&by&the&larynx&and&vocal&cords&&
•  Delivered&throughout&the&respiratory&cycle&and&
is&synonymous&to&CPAP,&but&in&the&intubated&
pa5ent&
PEEP&
•  Prevents&alveolar&collapse&
•  Improves&oxygena5on&
•  How&high?&
–  Fixed&regimens&?&
–  PressureNvolume&curve&
inflec5on&points&?&
Don t forget that the peak airway pressure
will also include the PEEP that is added
7&
30/01/2012&
Don t forget that the peak airway pressure
will also include the PEEP that is added
Modes&of&ven5la5on&
•  Mandatory&&
•  Synchronised&intermiqent&mandatory&
ven5la5on&(SIMV)&
•  Spontaneous&e.g.&pressure&support&
•  Unsupported&spontaneous&i.e.&CPAP&
Mandatory-(controlled)-ven1la1on-
SIMV&
•  Device&terminology&&varies&
•  Three&types&of&breath:&
–  Mandatory&(5med)&
–  Supported&(spontaneous)&
–  Assisted&(addi5onal&spontaneous)&
•  Commonly:&&
–  Mandatory&&&supported&=&volume&e.g.&500ml&
–  Assisted&=&pressure,&e.g.&16&cmH2O&&
–  Minimum&RR&set&
8&
7
C HAPTER
Synchronous intermittent
mandatory ventilation (SIMV)
7
30/01/2012&
SIMV is a mixed ventilatory mode that allows both mandatory
and spontaneous breaths. The mandatory breaths can be volumeor pressure-based, and the spontaneous breaths can be pressureassisted (for example, when pressure support is in effect). You can
select pressure- or flow-triggering in SIMV.
The SIMV algorithm is designed to guarantee one mandatory
breath each SIMV breath cycle. This mandatory breath is either a
patient-initiated mandatory (PIM) breath (also called an assisted
breath) or a ventilator-initiated mandatory (VIM) breath (in case
the patient's inspiratory effort is not sensed within the breath
cycle).
As Figure 7-1 shows, each SIMV breath cycle (Tb) has two parts:
the first part of the cycle is the mandatory interval (Tm) and is
reserved for a PIM. If a PIM is delivered, the Tm interval ends and
the ventilator switches to the second part of the cycle, the
spontaneous interval (Ts), which is reserved for spontaneous
breathing throughout the remainder of the breath cycle. At the
end of an SIMV breath cycle, the cycle repeats. If a PIM is not
delivered, the ventilator delivers a VIM at the end of the
mandatory interval, then switches to the spontaneous interval.
SIMV&
Synchronised-intermiEent-mandatory-ven1la1on(SIMV)--
Tb = SIMV breath cycle
(includes Tm and Ts )
Tb
Tm
Ts
Tm = Mandatory interval
(reserved for a PIM breath)
Ts = Spontaneous interval (VIM)
delivered if no PIM delivered
during Tm)
8-00055
Figure 7-1. SIMV breath cycle (mandatory and spontaneous intervals)
4-075609-00 Rev. G (10/06)
840 Ventilator System Technical Reference
TR 7-1
TR 7
Synchronous intermittent mandatory ventilation (SIMV)
Figure 7-2 shows an SIMV breath cycle where a PIM is delivered
within the mandatory interval.
PIM
(Subsequent trigger efforts during Ts
yield spontaneous breaths)
Tm transitions to Ts when a PIM is delivered
Tm
Ts
Tb
SIMV&
TR 7
Synchronous intermittent mandatory ventilation (SIMV)
SIMV&
8-00056
Figure 7-2. SIMV breath cycle, PIM delivered within mandatory interval
Figure 7-3 shows an SIMV breath cycle where a PIM is not
delivered within the mandatory interval.
Figure 7-2 shows an SIMV breath cycle where a PIM is delivered
within the mandatory interval.
VIM
PIM
(Subsequent trigger efforts during Ts
yield spontaneous breaths)
VIM delivered at end of Tm
if no PIM delivered during Tm
Tm transitions to Ts when a PIM is delivered
Tm
Tm
Ts
Ts
Tb
Tb
8-00057
8-00056
Figure 7-2. SIMV breath cycle, PIM delivered within mandatory interval
Figure 7-3. SIMV breath cycle, PIM not delivered within mandatory interval
7.1
Figure 7-3 shows an SIMV breath cycle where a PIM is not
delivered within the mandatory interval.
Mandatory breaths in SIMV are identical to mandatory breaths in
A/C mode, and spontaneous breaths in SIMV are identical to
spontaneous breaths in SPONT mode. Patient triggering must
meet the requirements for flow and pressure sensitivity.
VIM
VIM delivered at end of Tm
if no PIM delivered during Tm
Tm
Breath delivery in SIMV
Ts
Tb
8-00057
Figure 7-3. SIMV breath cycle, PIM not delivered within mandatory interval
7.1
840 Ventilator System Technical Reference
4-075609-00 Rev. G (10/06)
TR 7-2
Breath delivery in SIMV
Mandatory breaths in SIMV are identical to mandatory breaths in
A/C mode, and spontaneous breaths in SIMV are identical to
spontaneous breaths in SPONT mode. Patient triggering must
meet the requirements for flow and pressure sensitivity.
9&
840 Ventilator System Technical Reference
TR 7-2
4-075609-00 Rev. G (10/06)
30/01/2012&
Spontaneous&ven5la5on&
1.&Pressure-support-ven1la1on-(PSV)Ven5lator&provides&insp.&assistance&to&each&
pa5ent&effort&(flowNcycled)&
2.&Con1nuous-posi1ve-airways-pressure-(CPAP)Constant&pressure&above&atmospheric&
maintained&
Spontaneous-ven1la1on-(pressure-support)-
Pressure&support&ven5la5on&
•  Some5mes&known&as&“Assisted&spontaneous&
Breaths”&(ASB)&&
•  Part&of&weaning&process&/&improves&muscle&
strength&
•  Decreases&work&of&spontaneous&breathing&
•  Pa5ent&controlled&RR,&Ti&and&I:E&=&comfortable&&&
less&seda5on&
•  Fa5gue&possible&
•  Apnoea&possible&
Spontaneous-ven1la1on-(CPAP)-
10&
30/01/2012&
Pressure Support Ventilation
Other&modes…&
•
•
•
•
•
Airway&pressure&release&ven5la5on&(APRV)&
Pressure&regulated&volume&control&(PRVC)&
Propor5onal&Assist&Ven5la5on&(PAV)&
Automa5c&Tube&Compensa5on&(ATC)&
BiLevel&
FORGET%ABOUT%THEM%!!%
Patient
Patient
Complica5ons&of&ven5la5on&
•  Barotrauma:-Pressure&bursts&alveoli&and&small&air&
passages&and&in&par5cular&bursts&alveoli&into&
adjacent&bronchovascular&sheath&&
•  Volutrauma:-abnormal&stretching&of&lung&5ssue&
disrup5ng&architecture;&also&causes&release&of&
cytokines&and&feeds&inflammatory&process&&
•  Atelectotrauma:-areas&of&closed&lung&forcefully&
reopened&in&a&situa5on&of&low&surfactant&leading&
to&trauma&to&the&alveolar&walls&(openNclose)&
How&much&oxygen?&
•  Normoxaemia&is&desirable&
•  Higher&FIO2&if&unknown&gas&exchange&
capability&
•  Alter&FIO2&to&achieve&target&
•  Oxygen&toxicity&
11&
30/01/2012&
Common&seFngs&
•
•
•
•
•
•
•
MODE&
Inspiratory&phase&(pressure&/&volume)&
Desired&pressure&/&volume&
RR&
I:E&
FIO2&&
Alarms&
Need-forven1la1on-
Mandatory-
Pressure&
Volume&
Spontaneous-
SIMV-
Pressure&
Volume&
Pressure&
Volume&
CPAP&
PEEP-
Basic Ventilatory Modes: Summary
CMV
PSV
PEEP
SIMV
PSV
Mandatory
Overlap
Spontaneous
12&