1. Complications of Mechanical Ventilation

2. Ventilator-Induced lung injury (VILI)
Overdistention
Volutrauma
Repeated recruitment and collapse
Atelectetrauma
Inflammatory mediators
Bio trauma
High-pressure induced lung damage
Barotrauma
FiO2
Oxygen toxic effect 2

3. The Problem of Heterogeneity in ARDS
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4. The Problem of Heterogeneity Especially in ARDS
Some lung units may be overstretched while others remain collapsed at the same airway pressure.
Finding the right balance of TV and PEEP to keep the lung open without generating high pressures is the goal.
This presents major difficulty for the clinician, who must apply only a single pressure to ventilate patients

5. Ventilator-induced Lung Injury (VILI)
Collapse
Over
Distension

6. Pinsp = 40 mbar

7. Ventilator-Induced Lung Injury Atelectotrauma Vs Volutrauma
Atelectrauma:
Repetitive alveolar collapse and reopening of the under-recruited alveoli
Volutrauma:
Over-distension of normally aerated alveoli due to excessive volume delivery
Dreyfuss: J Appl Physiol 1992 7

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

9. How Much Collapse Is Dangerous Depends on the Plateau20 60
100
Pressure [cmH2O] 40
Total Lung Capacity [%]
R = 22%
R = 81%
R = 93%
R = 0%
R = 59%
Some potentially recruitable units open only at high pressure
More Extensive
Collapse But
Lower PPLAT
Less Extensive
Greater PPLAT
R = 100%
From Pelosi et al AJRCCM 2001

10. Effect of lung expansion on pulmonary vasculature
Effect of lung expansion on pulmonary vasculature. Capillaries that are embedded in the alveolar walls undergo compression even as interstitial vessels dilate. The net result is usually an increase in pulmonary vascular resistance, unless recruitment of collapsed units occurs.

11. VALI vs VILI Ventilator-associated lung injury (VALI)
Acute lung injury that resembles ARDS in patients receiving MV
VALI may be associated with pre-existing lung pathology
VALI is associated only with MV
Ventilator induced lung injury (VILI)
Acute lung injury directly induced by MV in animal models

12. Histopathology of VILI
Belperio et al, J Clin Invest Dec 2002; 110(11):

13. Mechanisms of Airspace Injury
Airway Trauma
“Stretch”
“Shear”

14. ARDS
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15. ARDS after PEEP preventing atelectotrauma

16. Atelectetrauma

17. The PEEP Effect NEJM 2006;354:1839-1841
taken at the end of inspiration.
A=0, B=15, C=15 x3, D= 15*5 F=0*1, G = 0*3, H =0*5
NEJM 2006;354:

18. Avoiding Atelectotrauma :How much PEEP is enough
Avoiding Atelectotrauma :How much PEEP is enough? ARDSnet protocol: PEEP - FiO2 Combinations
GOAL: PaO mm Hg or SpO %
Use these FiO2/PEEP combinations to achieve oxygenation goal.
FIO2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
PEEP 5 8 10 12 14 16 18
20-24
New Eng J Med. 2000;342(18)

19. Zone of
↑ Risk

20. Biophysical biochemical Injury due to MV
Biotrauma
Cytokines, complement, prostanoids, leukotrienes, O2- Proteases
Organ dysfucntion
Biophysical biochemical Injury due to MV
High volume & Low PEEP 20

21. Lung-Protective Ventilation
ARDS Network, 2000: Multicenter randomized,861Pts
Lung-protective ventilation
Conventional ventilation
Tidal Volume (ml/kg) 6 12
Pplateau
<30
<50
PEEP
Protocol
Actual PEEP
8.1
9.1
Result (p<0.001)
31.0%
39.8%
用的是預期體重
Principle for FiO2 and PEEP Adjustment
FiO2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
PEEP 5
5-8
8-10 10
10-14 14
14-18
18-24
NEJM 2000; 342:

22. Lung-Protective Ventilation Low VT Low Plateau pressure
Result:
22% reduction in mortality (31% vs 39.8%)
Increase ventilator-free days
目前唯一對mortality有效的方法
NEJM 2000; 342:

23. Optimized Lung Volume “Safe Window”
Overdistension
Edema fluid accumulation
Surfactant degradation
High oxygen exposure
Mechanical disruption
Derecruitment, Atelectasis
Repeated closure / re-expansion
Stimulation inflammatory response
Inhibition surfactant
Local hypoxemia
Compensatory overexpansion
Zone of
Overdistention
Injury
“Safe”
Window
Volume
Zone of
Derecruitment
and Atelectasis
Injury
Pressure

24. Dependent to Non-dependent Progression of Injury

25. Links Between VILI and MSOF
Biotrauma and Mediator
De-compartmentalization
Slutsky, Chest 116(1):9S-16S

26. Effect of 45 cmH2O PIP
Control min min

27. Baro-trauma Etiology :Directly related to airway pressures/PEEP
Incidence
4% - 15%
Highest in ARDS
Incidence now decreased secondary to lung protective ventilation

28. Barotrauma-Pathophysiology
Some alveoli become more distended than others. Alveolar pressure increases and forms a pressure gradient between the alveoli and adjacent perivascular sheath.
Air dissects into the perivascular sheath leading to perivascular interstitial emphysema (PIE) and further moves into areas of least resistance including subcutaneous tissue and tissue planes.

29. Barotrauma-Complications
Pneumothorax
Interstitial emphysema
Pneumomediastinum-leads to PTX in 42% of patients in one study
Pneumopericardium
Subcutaneous emphysema
Pneumoperitoneum

30. Gas Extravasation

31. Barotrauma

33. Oxygen Toxicity : FIO2 > 60 % for > 24h
Absorptive atelectasis
O2/N2 = 21/79 >>>>>> 50/50
Oxygen
Carbon dioxide
Water vapour
Nitrogen

34. Hyperoxia toxicity: mechanism
Free radicals: lipid peroxidations, especially in the cell membranes, inhibit nucleic acids and protein synthesis, and inactivate cellular enzymes.
Explosive free radical production leading to swamping of the anti-oxidant enzyme systems and as a result free radicals escape inactivation.

35. Oxygen Toxicity Absorptive atelectasis Accentuation of hypercapnia
Chronic respiratory failure: PCO2 with PO2
Damage to airways
Bronchopulmonary dysplasia
Diffuse alveolar damage

37. Infectious complications of Mechanical ventilation

38. Maxillary Sinus and Middle Ear Effusion
Maxillary effusion
20% in patients intubated for > 7 days.
47% when the gastric tube is placed nasally
95%
Secondarily infected maxillary effusion (45-71% of effusions)
Middle ear effusion (29%) with 22% of them become infected
Hearing impairment that may contribute to the confusion and delirium in elderly population

39. VAP: Definitions VAP – ventilator associated pneumonia
>48 hours on vent
Combination of:
CXR changes
Sputum changes
Fever, ↑ WBC
positive sputum culture
Occurs secondary to micro-aspiration of upper airway secretions

40. Organism Entry for VAP

41. Risk Factors for VAP No 1 risk factor is endotracheal intubation
Factors that enhance colonization of the oropharynx &/or stomach:
Poor oral hygiene
Conditions favoring aspiration into the respiratory tract or reflux from GI tract:
Supine position
NGT placement
Re-Intubation and self-extubation
Surgery of head/neck/thorax/upper abdomen
GERD
Coma/ depressed Glascow coma scale

42. Significance of VAP
Mortality 20-70%(Leading cause of mortality from nosocomial infections in hospitals)
Increases mechanical ventilation days
Increases ICU stay by 4.3 days
Increases hospital LOS by 4-9 days
Increases cost -Excess costs of approximately 11,000 -$40,000/patient

43. VAP prevention :VAP Bundle
Elevation of the head of the bed 30-45o
Use 15-30o for neonates and small infants, otherwise 30-45o
Daily sedation vacations (minimize duration of intubation
Daily assessment of readiness to extubate
Peptic ulcer disease (PUD) prophylaxis
Oral care protocol (chorhexidine)
DVT prophylaxis option

44. HOB 30-45o decrease risk of aspiration
45o head-up tilt is the goal in all patients unless contraindicated
No benefit of semi-recumbency ~30o over standard care ~10o
Supine position is harmful

45. HOB Elevation Leads to Significant reduction in VAP
Studies have also shown a dramatic decrease in VAP when a simple HOB elevation is done.
These data are from a study by Drakulovic et al in 86 intubated and mechically ventilated patients in a medical and respiratory ICU.
Subjects were randomly assigned to either 0 degrees or 45 degree HOB elevation.
VAP was detected in 2 of 39 patients (5%) in the HOB elevation to 45 degree group and 11 of 47 patients (23%) of the 0 degree HOB elevation.
The risk reduction was 78% for patients placed in the HOB elevation to 45 degrees.
Dravulovic et al. Lancet 1999;354:

47. Handwashing
Strict handwashing before and after handling patient or patient’s equipment or supplies

48. Does the VAP bundle work in real life
NHSN 50th Percentile 4.1

49. Complications of Mechanical Ventilation
Complications related to Intubation
Mechanical complications related to presence of ETT
Ventilator induced lung injury
Complications related to Oxygen
Infectious complications of mechanical ventilation