1. Mechanical Ventilation 101
Dr Paul Healey
ICU Fellow
John Hunter Hospital Newcastle

2. Outline What is mechanical ventilation ?
History of mechanical ventilation.
Why do we mechanically ventilate patients ?
Modes of mechanical ventilation ?
Setting the ventilator
Trouble shooting ventilation
Refractory Hypoxaemia
When to extubate the patient ?

3. Mechanical ventilation
Is a method to mechanically assist or replace spontaneous ventilation.
Is a supportive therapy.
Two main divisions of mechanical ventilation
Negative pressure ventilation
Positive pressure ventilation

6. Polio epidemic – Copenhagen 1952

8. Positive pressure ventilation

9. Mechanical ventilation
Positive pressure ventilation
Non-invasive ventilation (NIV) modes:
Continuous Positive Airways Pressure (CPAP)
Bi-level Positive Airways Pressure (BiPAP)
Invasive positive pressure ventilation (IPPV) modes:
Volume Control Ventilation (VCV)
Pressure Control Ventilation (PCV)
Pressure Support Ventilation (PSV)

10. Case study Mr CS – 75 year old male, weighs 80kg. Background
IHD, Ex-smoker 20 years ago, Type II DM, AF.
Day 4 post Hartmans procedure for colorectal cancer, severe abdominal pain and fever. Anastamotic leak on CT scan. Commenced on IV Tazocin.
Taken to OT and had extensive washout of abdomen and stoma formed. Abdomen is closed.
Currently ventilated in OT on FiO2 50% PCV-VG 14 x 480mL, with PEEP of 6cmH2O.
Vital signs: HR 115, BP 110/50 on 0.2mcg/kg/min of Noradrenaline, SaO2 96%, temperature 38.8 degrees.
Last ABG: pH 7.32, PaO2 92mmHg, PaCO2 35mmHg, Lactate 2.2mmol/l and BE -5.3mmol/l
What is the reason for mechanically ventilating this patient ??
What are the risks of mechanical ventilation ??

11. Why do we mechanically ventilate patients ?
Indications for mechanical ventilation
Impaired level of consciousness
Potential airway compromise
Respiratory failure
Hypoxaemic
Hypercapnoeic
Work of breathing and fatigue
Cardiac failure

12. Risks of mechanical ventilation
1. Respiratory Complications
Infection
Ventilator Associated Events
Ventilator Induced Lung Injury (VILI)
Barotrauma
Volutrauma
Atelectotrauma
Gas trapping and intrinsic PEEP
Oxygen toxicity
2. Non-respiratory complications
Haemodynamic compromise
Raised ICP
Reduced urine output
Ventilator induced lung injury
Excessive inflation pressurem
Mechanical tissue damage
Inflammation – mechano-signaling due to tensile forces
Overstretching of lung units
Shear force at junction of open and collapsed tissue
Repeated opening and closing of small airways under high pressure

13. Modes of ventilation

14. Modes of invasive ventilation
Nomenclature
Triggering – what initiates a breath
Ventilator
Patient
Inspiration
Volume
Pressure
Cycling – what determines change from inspiration to expiration
Time
Flow
Exhalation
Passive process due to lung elastic recoil

15. Modes of ventilation Classification based on patient triggering:
1. Mandatory ventilation modes
2. Spontaneous ventilation modes
3. Adaptive ventilation modes
Mandatory modes in the past did not allow triggering. Now they do.
Spontaneous modes in the past did not allow back up ventilation, but now they do.
Adaptive ventilation modes are a combination of mandatory, and spontaneous modes that adapt to the

16. Modes of ventilation 1. Mandatory ventilation modes
Volume control ventilation (VCV)
Pressure control ventilation (PCV)
Synchronised Intermittent Mandatory Ventilation (SIMV)

17. Ventilator waveforms

18. Volume Control Ventilation

20. Modes of ventilation 1. Mandatory modes Volume control ventilation
All breaths given are the same preset volume
Advantages
Relatively simple to set
Guaranteed minute ventilation
Rests respiratory muscles
Disadvantages
Historically, no patient triggering
Ventilator-patient dysynchrony
Reduced lung compliance will result in increased pressures and potential barotrauma

21. PCV

23. Modes of ventilation 1. Mandatory modes Pressure control ventilation
All breaths have same preset inspiratory pressure and time
Advantages
Simple to set
Avoids high inspiratory pressures
Rests respiratory muscles
Disadvantages
Historically, no patient triggering
Change in lung compliance results in change in tidal volumes
No guaranteed minute ventilation

24. SIMV

25. SIMV

26. Modes of ventilation 1. Mandatory modes SIMV Advantages Disadvantages
- Mandatory VCV or PCV with triggered PSV
Advantages
Better patient-ventilator synchrony
Guaranteed minute ventilation
Allows patient triggering and possible weaning
Disadvantages
- More complicated mode with multiple settings

27. PSV

29. Modes of ventilation 2. Spontaneous ventilation modes
Pressure support ventilation
Provides a set inspiratory and expiratory pressure during patient initiated breathing
Inspiration ends when inspiratory flow falls to a preset level (usually 25%)
Advantages
Maintains full spontaneous ventilation
Better ventilator-patient synchrony
Weaning mode of ventilation
Disadvantages
Historically no back-up ventilation
Changes in patient effort and lung compliance effect tidal volumes

30. PRVC Ventilator will adjust pressure by 3cmH2O to aim for TV.
The SERVO-i will restart with the start-up sequence should one of the following criteria occur:
- if the delivered Vt is 50% less than the set Vt, or
when the Upper pressure limit is exceeded during 3 consecutive breaths
If the measured Insp. Tidal Volume is more than 1.5 times higher than the set Tidal Volume,
the breath is interrupted and the next breath is delivered with 25% reduced pressure compared
with the previous breath. However, the maximum pressure decrease is 20 cmH2O.
If the patient suddenly coughs during an inspiration, and if the pressure reaches the set Upper
pressure limit, then the ongoing inspiration will be cut off and the next breath is delivered with
the same pressure as the previous breath.
TUTORIAL
English

32. Mechanical ventilation
3. Adaptive ventilation modes
Assist
Pressure regulated volume control
PCV - VG

33. Case study Mr CS – 75 year old male, weighs 80kg. Background
IHD, Ex-smoker 20 years ago, Type II DM, AF.
Day 4 post Hartmans procedure for colorectal cancer, severe abdominal pain and fever. Anastamotic leak on CT scan. Commenced on IV Tazocin.
Taken to OT and had extensive washout of abdomen and stoma formed. Abdomen is closed.
Currently ventilated in OT on FiO2 50% PCV-VG 14 x 480mL, with PEEP of 6cmH2O.
Vital signs: HR 115, BP 110/50 on 0.2mcg/kg/min of Noradrenaline, SaO2 96%, temperature 38.8 degrees.
Last ABG: pH 7.32, PaO2 82mmHg, PaCO2 35mmHg, Lactate 2.2mmol/l and BE -5.3mmol/l
How are you going to set the ventilator ??
What other information would you want to know ??

34. Setting the ventilator
FiO2
Mode
Triggering
Tidal volume
Inspiratory pressure
PEEP
Respiratory rate
Inspiratory time
I:E ratio
Inspiratory flow
Alarm settings
Peak pressure
PEEP
Minute ventilation

35. How to set a ventilator FiO2 Mode Triggering
Begin at 100% and wean as quickly as able to < 60%
Mode
Volume controlled ventilation
Set tidal volume 6 – 8 mL/kg
Pressure controlled ventilation
Set inspiratory pressure 10 – 20 cmH2O
Triggering
Flow triggering : 1 – 5 L/min
Pressure triggering: -0.5 to -2.0 cmH2o
Inspiratory pressure (Plateau)
Aim < 30 cmH2O.
VCV or SIMV = plateau pressure
PCV = Sum of PEEP and Inspiratory pressure
PEEP
Start with 5-10 cmH20
Respiratory rate
Start at 10 – 12 breaths per minute
Inspiratory time
Normal 0.8 – 1.3 seconds
I:E ratio
Normally 1:2
Increase in obstructive airways disease (COPD/Asthma)
Inspiratory flow
40 – 60 L/min

36. Case study Mr CS – 75 year old male, weighs 80kg. Background
IHD, Ex-smoker 20 years ago, Type II DM, AF.
Day 4 post Hartmans procedure for colorectal cancer, severe abdominal pain and fever. Anastamotic leak on CT scan. Commenced on IV Tazocin.
Taken to OT and had extensive washout of abdomen and stoma formed. Abdomen is closed.
Currently ventilated in OT on FiO2 50% PCV-VG 14 x 480mL, with PEEP of 6cmH2O.
Vital signs: HR 115, BP 110/50 on 0.2mcg/kg/min of Noradrenaline, SaO2 96%, temperature 38.8 degrees.
Last ABG: pH 7.32, PaO2 82mmHg, PaCO2 35mmHg, Lactate 2.2mmol/l and BE -5.3mmol/l
How are you going to set the ventilator ??
What other information would you want to know ??

38. Setting the ventilator
FiO2
Mode
Triggering
Tidal volume
Inspiratory pressure
PEEP
Respiratory rate
Inspiratory time
I:E ratio
Inspiratory flow
Alarm settings
Peak pressure
PEEP
Minute ventilation

39. What is the evidence ??

40. Ventilation modes - evidence
A single RCT and 3 observational trials
There were no statistically significant differences in mortality, oxygenation, or work of breathing
PCV
lower peak airway pressures
a more homogeneous gas distribution (less regional alveolar over distension)
improved patient-ventilator synchrony
earlier liberation from mechanical ventilation than volume-limited ventilation
VCV
it can guarantee a constant tidal volume, ensuring a minimum minute ventilation
Most studies comparing pressure-limited and volume-limited ventilation used a square wave (constant flow) pattern for both modes. When volume-limited mechanical ventilation with a ramp wave (decelerating flow) pattern was compared to pressure-limited ventilation, lower peak airway pressures were no longer an advantage of pressure-limited ventilation

41. Evidence for ventilation

43. The trial was stopped after the enrollment
of 861 patients because mortality was lower in the
group treated with lower tidal volumes than in the
group treated with traditional tidal volumes (31.0 percent
vs percent, P=0.007),
NORMAL MORTALITY RATE OF 40 – 60%

45. Twenty articles (2822 participants) were included. Meta-analysis using
a fixed-effects model showed a decrease in lung injury development (risk ratio [RR], 0.33;
95% CI, 0.23 to 0.47; I2, 0%; number needed to treat [NNT], 11), and mortality (RR,
0.64; 95% CI, 0.46 to 0.89; I2, 0%; NNT, 23) in patients receiving ventilation with lower
tidal volumes.

46. Evidence for ventilation
2013

48. In this multicenter, double-blind, parallel-group trial, we randomly assigned 400
adults at intermediate to high risk of pulmonary complications after major abdominal
surgery to either nonprotective mechanical ventilation or a strategy of
lung-protective ventilation. The primary outcome was a composite of major pulmonary
and extrapulmonary complications occurring within the first 7 days after
surgery.

49. Evidence for ventilation –FACCT trial
2006

51. Trouble shooting ventilation

52. Case study Mr CS – 75 year old male, weighs 80kg. Background
IHD, Ex-smoker 20 years ago, Type II DM, AF.
Day 4 post Hartmans procedure for colorectal cancer, severe abdominal pain and fever. Anastamotic leak on CT scan. Commenced on IV Tazocin.
Taken to OT and had extensive washout of abdomen and stoma formed. Abdomen is closed.
Vital signs: HR 115, BP 110/50 on 0.2mcg/kg/min of Noradrenaline, SaO2 96%, temperature 38.8 degrees.
The nursing staff come to you after one hour and show you the following ABG:
pH: 7.21, PaO2 82mmHg, PaCO2 58mmHg, Lactate 2.1mmol/l, BE -5.2mmol/l
How will you adjust the ventilator ??

53. Trouble shooting ventilation
We need to increase minute ventilation
Minute ventilation = TV x RR

54. Trouble shooting ventilation
Dead space ventilation
- Excess tubing, especially in paediatrics
2. Tidal volume
Aim 6-8 mL/kg
Risk of barotrauma if plateau pressure > 30cmH2O
Risk of volutrauma
3. Respiratory rate
Aim for < 30
Monitor for gas trapping, dynamic hyperinflation and intrinsic PEEP

55. Trouble shooting ventilation

56. Trouble shooting ventilation

57. Case study Mr CS – 75 year old male, weighs 80kg. Background
IHD, Ex-smoker 20 years ago, Type II DM, AF.
Day 4 post Hartmans procedure for colorectal cancer, severe abdominal pain and fever. Anastamotic leak on CT scan. Commenced on IV Tazocin.
Taken to OT and had extensive washout of abdomen and stoma formed. Abdomen is closed.
Vital signs: HR 130, BP 90/50 on 0.3mcg/kg/min of Noradrenaline, SaO2 96%, temperature 38.8 degrees
He is ventilated in ICU, and adjustments made after the last ABG.
The nursing staff come to you later that shift stating the patient has desaturated to 85% and shows you the following ABG:
pH 7.30, PaO2 52mmHg, PaCO2 40mmHg, lactate 2.0mmol/l, BE -5.1mmol/l
How will you manage this ??

58. Trouble shooting ventilation
Hypoxaemia
Most patients need SaO % at the most, some only 88-92% (chronic respiratory disease)
What to do ??

60. Patient is still hypoxic !

61. Trouble shooting ventilation
Increase FiO2
Increase mean alveolar pressure
Main determinant of oxygenation
Can be increased by increasing
Inspiratory pressure or tidal volume
Inspiratory time
PEEP
Increase PEEP
Maintains open alveoli and reduces shunt

65. What if SaO2 is still only 85% ??

66. Refractory hypoxaemia

67. Refractory hypoxaemia
1. Recruitment maneuvers
Is a high pressure inflation maneuver aimed at temporarily raising the transpulmonary pressure above levels typically obtained with mechanical ventilation.
Purpose is to overcome the high “opening pressures” of diseased and collapsed alveoli.
By opening alveoli, this increases the area available for gas exchange and oxygen transfer.
Open collapsed lung tissue so it can remain open during tidal ventilation with lower pressures and PEEP, thereby improving gas exchange and helping to eliminate high stress interfaces
Although applying high pressure is fundamental to recruitment, sustaining high pressure is also important
Methods of performing a recruiting maneuver include single sustained inflations and ventilation with high PEEP

68. Spectrum of Regional Opening Pressures (Supine Position)
Small Airway
Collapse
10-20 cmH2O
Inflated
Superimposed
Pressure
Consolidation 
Alveolar Collapse
(Reabsorption)
20-60 cmH2O =
Lung Units at Risk for Tidal
Opening & Closure

71. met the inclusion criteria for this review (the total number of included participants was 1170). All trials included a
recruitment manoeuvre as part of the treatment strategy for patients on mechanical ventilation for ARDS or ALI. However, two of the
trials included a package of ventilation that was different from the control ventilation in aspects other than the recruitment manoeuvre.
The intervention group showed no significant difference on 28-day mortality (RR 0.73, 95% CI 0.46 to 1.17, P = 0.2). Similarly there
Recruitment manoeuvreswas no statistical difference for risk of barotrauma (RR 0.50, 95% CI 0.07 to 3.52, P = 0.5) or blood pressure (MD 0.9 mm Hg, 95%
CI to 6.08, P = 0.73). Recruitment manoeuvres significantly increased oxygenation above baseline levels for a short period of
time in four of the five studies that measured oxygenation. There were insufficient data on length of ventilation or hospital stay to pool
results.

72. Refractory hypoxaemia
2. Inhaled prostacyclin
Nebulised prostacylin (PGI-2) given continuously via an ultrasonic nebuliser attached to the inspiratory limb of the ventilator.
An alternative to inhaled Nitric Oxide which is expensive and requires scavenging set-up.
Prostacyclin (PGI2), generic name epoprostenol (brand name
Flolan) is a member of the family of lipid molecules known as
eicosanoids. PGI2 is a naturally occurring prostaglandin that has
vascular smooth muscle relaxant and has anti-inflammatory properties
(it inhibits platelet aggregation and neutrophil adhesion).
It is synthesized by vascular endothelial and smooth muscle cells
within the lung and has an in vivo half-life of three to six minutes
(Jain 2006). PGI2 is a potent vasodilator of the systemic
and pulmonary vasculature resulting in reduction of right and left
heart afterload (Siobal 2004) and can be administered by different
routes such as: intravenous for pulmonary hypertension, and
inhalational preparations for ALI and ARDS. Inhaled PGI2 appears
to improve oxygenation; lower pulmonary vascular resistance
(PVR) andmean pulmonary arterial pressure (MPAP); and reduce
pulmonary shunt fraction (Siobal 2004). It might have potential
benefits in resolving hypoxaemia from ALI or ARDS and in the
treatment of pulmonary hypertension and right heart failure, similar
to the indications for inhaled nitric oxide (Siobal 2004).

75. Refractory hypoxaemia
3. Prone ventilation
Has been studied in severe ARDS
Complex process with safety issues
Risk of extubation
Risk of removing lines
Pressure areas
OH and S
Homogenise transpleural pressure
Compression – reduced compression from heart + abdomen
Improved recruitment
Increase in FRC
Decreased shunt
Benefit
Improved oxygenation in 60-80% patient, even on return to supine position

76. PROSEVA trial
2013
severe ARDS to undergo prone-positioning sessions of at
least 16 hours or to be left in the supine position. Severe ARDS was defined as a
ratio of the partial pressure of arterial oxygen to the fraction of inspired oxygen
(Fio2 ) of less than 150 mm Hg, with an Fio2 of at least 0.6, a positive end-expiratory
pressure of at least 5 cm of water, and a tidal volume close to 6 ml per kilogram
of predicted body weight.

78. Refractory hypoxaemia
4. High frequency oscillatory ventilation
Specialised equipment
Respiratory rates of Hz
Mean airway pressures of 30cmH2O
Tidal volumes smaller than dead space !
Effective at rescue oxygenation

80. OSCILLATE trial
Canada and Saudi Arabia

81. On the recommendation of the data monitoring committee, we stopped the trial after
548 of a planned 1200 patients had undergone randomization. The two study groups
were well matched at baseline. The HFOV group underwent HFOV for a median of
3 days (interquartile range, 2 to 8); in addition, 34 of 273 patients (12%) in the
control group received HFOV for refractory hypoxemia.
Patients in the HFOV group received higher doses of midazolam than
did patients in the control group (199 mg per day [interquartile range, 100 to 382]
vs. 141 mg per day [interquartile range, 68 to 240], P<0.001), and more patients in the
HFOV group than in the control group received neuromuscular blockers (83% vs.
68%, P<0.001). In addition, more patients in the HFOV group received vasoactive
drugs (91% vs. 84%, P = 0.01) and received them for a longer period than did patients
in the control group (5 days vs. 3 days, P = 0.01).

82. OSCAR trial
United Kingdom

83. There was no significant between-group difference in the primary outcome, which
occurred in 166 of 398 patients (41.7%) in the HFOV group and 163 of 397 patients
(41.1%) in the conventional-ventilation group (P = 0.85 by the chi-square test). After
adjustment for study center, sex, score on the Acute Physiology and Chronic Health
Evaluation (APACHE) II, and the initial Pao2 :FIo2 ratio, the odds ratio for survival
in the conventional-ventilation group was 1.03 (95% confidence interval, 0.75 to
1.40; P = 0.87 by logistic regression

84. Refractory hypoxaemia
5. Extracorporeal Membrane oxygenation (ECMO)
Involves gas exchange via an extracorporeal circuit.
Can support the lungs alone (V-V ECMO) or the heart and lungs (V-A ECMO)
Significant risks and costs

86. CESAR trial
In this UK-based multicentre trial, we used an independent central randomisation service to randomly
assign 180 adults in a 1:1 ratio to receive continued conventional management or referral to consideration for treatment
by ECMO. Eligible patients were aged 18–65 years and had severe (Murray score >3·0 or pH <7·20) but potentially
reversible respiratory failure. Exclusion criteria were: high pressure (>30 cm H#O of peak inspiratory pressure) or
high FiO# (>0·8) ventilation for more than 7 days; intracranial bleeding; any other contraindication to limited
heparinisation; or any contraindication to continuation of active treatment. The primary outcome was death or severe
disability at 6 months after randomisation or before discharge from hospital. Primary analysis was by intention to
treat.

88. Case study Mr CS – 75 year old male, weighs 80kg. Background
IHD, Ex-smoker 20 years ago, Type II DM, AF.
Day 4 post Hartmans procedure for colorectal cancer, severe abdominal pain and fever. Anastamotic leak on CT scan. Commenced on IV Tazocin.
Taken to OT and had extensive washout of abdomen and stoma formed. Abdomen is closed.
He has been ventilated in ICU for 5 days. He had a brief period of hypoxaemia due to bibasal atelectasis. It resolved with a recruitment maneuver and increased PEEP.
He has been on PSV for 24 hours, with settings FiO2 30%, Inspiratory pressure 10cmH2O and PEEP 5cmH2O.
His vital signs are: HR 90, BP 130/70, SaO2 98%, temperature 37.2 degrees
His latest blood gas shows:
pH 7.38, PaO2 95mmHg, PaCO2 39mmHg, lactate 0.7mmol/L and BE 1.0mm0l/L
How will you assess him for extubation ??
Should you extubate him onto NIV ??

89. Assessment for extubation
1. Disease process
Has disease process that required MV resolved
Complications – sepsis, transfusion
Pain – especially with thoracotomy, laparotomy
Fluid balance : ideally cummulative balance < 3L
2. Airway
Grade of intubation
How patient was intubated
Presence of cuff leak
Appropriate assistance available

90. Assessment for extubation
3. Neurological
Awake and co-operative
Pain controlled
Weakness
4. Respiratory
Ventilator support – ideally PSV < 10/5cmH2O
RR <30
Vital capacity > 10mL/kg
Cough
Secretion load – small load
Rapid shallow breathing index (f/Vt) <100
Review of CXR
5. Cardiovascular
Stable cardiac rhythm
Minimal ionotrope/vasopressor requirement

91. Extubation onto NIV
We identified 16 trials, predominantly ofmoderate to good quality, involving 994 participants,mostwith chronic obstructive pulmonary
disease (COPD). Compared with IPPV weaning, NPPV weaning significantly decreased mortality. The benefits for mortality were
significantly greater in trials enrolling exclusively participants with COPD (risk ratio (RR) 0.36, 95% confidence interval (CI) 0.24
to 0.56) versus mixed populations (RR 0.81, 95% CI 0.47 to 1.40). NPPV significantly reduced weaning failure (RR 0.63, 95% CI
0.42 to 0.96) and ventilator-associated pneumonia (RR 0.25, 95% CI 0.15 to 0.43); shortened length of stay in an intensive care unit
(mean difference (MD) days, 95% CI to -3.28) and in hospital (MD days, 95%CI to -2.87); and decreased the
total duration of ventilation (MD days, 95% CI to -1.77) and the duration of endotracheal mechanical ventilation (MD
days, 95% CI to -4.55) amidst significant heterogeneity. Noninvasive weaning also significantly reduced tracheostomy
(RR 0.19, 95% CI 0.08 to 0.47) and reintubation (RR 0.65, 95% CI 0.44 to 0.97) rates. Noninvasive weaning had no effect on the
duration of ventilation related to weaning

94. Conclusion Modes of ventilation How to set the ventilator
Mandatory
Spontaneous
Adaptive
How to set the ventilator
Evidence for ventilator strategies
Trouble shooting ventilation
Refractory Hypoxia
Assessment for extubation