MECHANICAL
VENTILATION
Marc Charles Parent
Presentation
Different settings to consider
Monitoring of the patient
Different type of patient
COPD, Asthma
ARDS
Trouble shooting
Ventilator settings
Ventilator settings
1. Ventilator mode
2. Respiratory rate
3. Tidal volume or pressure settings
4. Inspiratory flow
5. I:E ratio
6. PEEP
7. FiO2
8. Inspiratory trigger
CMV
A/CV
SIMV
PSV(pressure support
ventilation)
Spontaneous inspiratory efforts trigger
the ventilator to provide a variable flow
of gas in order to attain a preset airway
pressure.
Can be used in adjunct with SIMV.
Respiratory Rate
1. What is the pt actual rate demand?
Tidal Volume or Pressure
setting
Maximum volume/pressure to achieve
good ventilation and oxygenation
without producing alveolar
overdistention
Max cc/kg? = 10 cc/kg
Some clinical exceptions
Inspiratory flow
Varies with the Vt, I:E and RR
Normally about 60 l/min
Can be majored to 100- 120 l/min
I:E Ratio
1:2
Prolonged at 1:3, 1:4, …
Inverse ratio
FIO2
The usual goal is to use the minimum
Fio2 required to have a PaO2 >
60mmhg or a sat >90%
Start at 100%
Oxygen toxicity normally with Fio2
>40%
Inspiratory Trigger
Normally set automatically
2 modes:
Airway pressure
Flow triggering
Positive End-expiratory
Pressure (PEEP)
What is PEEP?
What is the goal of PEEP?
Improve oxygenation
Diminish the work of breathing
Different potential effects
PEEP
What are the secondary effects of PEEP?
Barotrauma
Diminish cardiac output
Regional hypoperfusion
NaCl retention
Augmentation of I.C.P.?
Paradoxal hypoxemia
PEEP
Contraindication:
No absolute CI
Barotrauma
Airway trauma
Hemodynamic instability
I.C.P.?
Bronchospasm?
PEEP
What PEEP do you want?
Usually, 5-10 cmH2O
Monitoring of the patient
Look at your patient
Question your pt
Examine your pt
Monitor your pt
Look at the synchronicity of your pt breathing
Pressures
Compliance pressure
(Pplat)
Represent the static end inspiratory
recoil pressure of the respiratory
system, lung and chest wall respectively
Measures the static compliance or
elastance
Pplat
Measured by occluding the ventilator 3-5 sec
at the end of inspiration
Should not exceed 30 cmH2O
Peak Pressure (Ppeak)
Ppeak = Pplat + Pres
Where Pres reflects the resistive
element of the respiratory system (ET
tube and airway)
Ppeak
Pressure measured at the end of inspiration
Should not exceed 50cmH2O?
Auto-PEEP or Intrinsic
PEEP
What is Auto-PEEP?
Normally,at end expiration, the lung
volume is equal to the FRC
When PEEPi occurs, the lung volume at
end expiration is greater then the FRC
Auto-PEEP or Intrinsic
PEEP
Why does hyperinflation occur?
Airflowlimitation because of dynamic
collapse
No time to expire all the lung volume (high
RR or Vt)
Expiratory muscle activity
Lesions that increase expiratory resistance
Auto-PEEP or Intrinsic
PEEP
Auto-PEEP is measured in a relaxed pt with
an end-expiratory hold maneuver on a
mechanical ventilator immediately before the
onset of the next breath
Auto-PEEP or Intrinsic
PEEP
Adverse effects:
Predisposes to barotrauma
Predisposes hemodynamic compromises
Diminishes the efficiency of the force
generated by respiratory muscles
Augments the work of breathing
Augments the effort to trigger the ventilator
Different types of
patient
COPD and Asthma
Goals:
Diminish dynamic hyperinflation
Diminish work of breathing
Controlled hypoventilation
(permissive hypercapnia)
Diminish DHI
Why?
Diminish DHI
How?
Diminish minute ventilation
Low Vt (6-8 cc/kg)
Low RR (8-10 b/min)
Maximize expiratory time
Diminish work of breathing
How:
Add PEEP (about 85% of PEEPi)
Applicable in COPD and Asthma.
Controlled hypercapnia
Why?
Limit
high airway pressures and thus
diminish the risk of complications
Controlled hypercapnia
How?
Control
the ventilation to keep adequate
pressures up to a PH > 7.20 and/or a
PaCO2 of 80 mmHg
Controlled hypercapnia
CI:
Head pathologies
Severe HTN
Severe metabolic acidosis
Hypovolemia
Severe refractory hypoxia
Severe pulmonary HTN
Coronary disease
A.R.D.S.
Ventilation with lower tidal volume as
compared with traditional volumes for
acute lung injury and the ARDS
The Acute Respiratory Distress Syndrome
Network
N Engl J Med 2000;342:1301-08
Methods
March 96 – March 99
10 university centers
Inclusion:
Diminish PaO2
Bilateral infiltrate
Wedge < 18
Exclusion
Randomized
Methods
A/C 28d or weaning
2 groups:
1. Traditional Vt (12cc/kg)
2. Low Vt (6cc/kg)
End point:
1. Death
2. Days of spontaneous breathing
3. Days without organ failure or barotrauma
Results
The trails were stopped after 861 pt because
of lower mortality in low Vt group
Trouble Shooting
Trouble Shooting
Doctor, doctor, his pressures are going
up!!!
What is your next step?
Trouble Shooting
1. Call the I.T., he will take care of it!
2. Where is the staff?
3. I dont know this pt, and run!
4. Ask which pressure is going up
Trouble Shooting
Ppeak is up
Look at your Pplat
Trouble Shooting
If your Pplat is high, you are faced with
a COMPLIANCE problem
If your Pplat is N, you are faced with a
RESISTIVE problem
DD?
Trouble Shooting
Trouble Shooting
Doctor, doctor, my patient is very
agitated!
What is your next step?
Trouble Shooting
1. Give an ativan to the nurse!
2. Give haldol 10mg to the patient!
3. Take 5mg of morphine for yourself!
4. Look at your pt!
Trouble Shooting
At the time of intubation, fighting is
largely due to anxiety
But what do you do if pt is stable and
then becomes agitated?
Trouble Shooting
1. Remove pt from ventilator
2. Initiate manual ventilation
3. Perform P/E and assess monitoring indices
4. Check patency of airway
5. If death is imminent, consider and treat
most likely causes
6. Once pt is stabilized, undertake more
detailed assessement and management
Trouble Shooting
Conclusion
Type of patient Tidal Volume RR PEEP FIO2 Ins. Flow I:E Note Note
Normal 10 cc/kg 10 to 12 0 to 5 100%. 60 l/min 1:2.
ARDS 6 cc/kg 10 to 12 5 to 15 100%. 60 l/min 1:2.
COPD 6 cc/kg 10 to 12 5 to 10 100%. 100 to 120 1:3 to 1:4 PH>7.2
PCO2 <80 mmhg
Trigger to consider
Trauma 10 cc/kg 10 to 12 0. 100%. 60 l/min 1:2.
Pediatric 8-10 cc/kg Varies age 3 to 5 100%. 60 l/min 1:2. Trigger to consider
