This document discusses strategies for mechanical ventilation in patients with acute respiratory distress syndrome (ARDS). It recommends using a protective ventilation strategy with low tidal volumes between 4-6 ml/kg and limiting airway plateau pressure to below 30 cmH2O to prevent ventilator-induced lung injury. Prone positioning is gaining acceptance as a standard of care for severe ARDS as it improves oxygenation and mortality outcomes. Early application of prone positioning for at least 16 hours per session is recommended for eligible ARDS patients meeting criteria. Recruitment maneuvers combined with high positive end-expiratory pressure are also advocated as part of an "open lung" approach to maximize aeration and oxygenation while minimizing pressures and volumes.

1. Mechanical ventilation – beyond
BASIC
ARDS
Hanaa A. El Gendy
Assistant Professor of Anesthesia and
ICU (ASUH)

2. The Berlin Definition 2011

6. Sternum
Vertebra

7. Complications of mechanical ventilation
• Oxygen
toxicity
• Barotrauma
• Volutrauma
• Shear injury
• Biotrauma

9. Solutions
• Minimize FIO2
–SpO2 88-94%
• Open lung

10. Recruitment Manoeuvres

12. Recruitment manoeuvre
Pressure
Time
Pressure
Time

23. Recruitment manoeuvre
Pressure
Time
Pressure
Time

24. Before Recruitment
Arterial blood gas 18:00 23/10/1999 Fi02=0.7
pH=7.47 pCO2=31 pO2=59 Saturation 91%
After Recruitment
Arterial blood gas 19:00 23/10/1999 Fi02=0.6
pH=7.45 pCO2=34 pO2=182 Saturation 99%

25. PEEP after recruitment
– Generally, it is recommended (Hickling 2001) to
gradually decrease PEEP until there is a fall in PO2; this is
a “decremental PEEP trial”
– PEEP is decreased by 2cmH2O every 4 minutes
– A fall in PO2 by over 10% indicates that there is
derecruitment
– PEEP is then set to just 2cmH2O above the level at which
derecruitment occurs
– For Girgis et al (2006) this strategy resulted in 4 hrs of
improved oxygenation

26. PEEP Endpoints
• Best PaO2
• Best O2 delivery
• Pplat < 30 cm H2o
• Best CT aeration
• The best possible lung compliance
• Hemodynamic stability

29. Protective Ventilation Strategy in ARDS
• Keep the PaO2 55-80 mmHg
• Maintain an arterial oxygen saturation (SaO2) of 88-94%
• Avoid volutrauma, barotraumas and biotrauma (VIL), by keeping the tidal volumes in the 4-6ml/kg
range and airway plateau pressure < 30 cmH2O .
• Predicted body weight in kg, calculated by: [2.3 *(height in inches - 60) + 45.5 for women or + 50
for men].
* PEEP values of 2cmH2O above PEEP associated with optimal compliance
• Higher respiratory rate.
• PH ≥ 7.15

30. The advantages of using PCV
in ARDS
Gas Distribution

31. Driving Pressure and Survival in the Acute Respiratory Distress Syndrome
The New England Journal of Medicine 2015

32. In patients with severe ARDS as defined by PaO2/FiO2 <150,
48 hrs administration of non depolarizing neuromuscular
blocking agent (NMBA) cisatracurium has been shown to
improve oxygenation, and adjusted 90-day survival, as well as
decreasing duration of mechanical ventilation and
barotrauma, without increasing muscle weakness .Moreover,
NMBAs have been shown to reduce levels of both pulmonary
and systemic pro-inflammatory mediators
Papazian L, Forel JM, Gacouin A, et al. Neuromuscular blockers in early acute
respiratory distress syndrome. N Engl J Med 2010;363:1107-16

33. THE ARDS LUNG

34. EARLY Prone ventilation

35. Preparation
• Criteria
– PaO2/FiO2 ratio ≤ 150mmHg (20kPa)
– PEEP ≥ 5cmH2O
– FiO2 ≥ 0.6
• Haemodynamically stable
• Not severely acidaemic,
• Does not have intracranial hypertension
• Adequately paralysed
• Increase FiO2 to 1.0 app 15-20 min before repositioning

36. Duration
• Most responders show an improvement in gas
exchange within a few hours
• Prone for 16h then supine for at least 4h

37. Venous access secure

38. Intubation drugs/equipment

39. Preparation
• Prepare padding to prevent pressure sores in
prone position
• Staff
• Someone who can re-intubate to look after head, neck
& ETT
• 4 other staff

40. Duration
• Most responders show an improvement in gas
exchange within a few hours
• Prone for 16h then supine for at least 4h

41. Prone positioning (face-down) improves gas exchange and has long been used as an
adjunctive or salvage therapy for severe or refractory ARDS. Prone positioning is
gaining credibility as a new standard of care for ARDS after a multicenter trial
published in 2013, demonstrated a dramatic near-50% relative risk reduction, and a
17% absolute risk reduction for mortality

42. Benefits of prone positioning
• Improves V/Q mismatch
• Increased ventilation in dependent areas
• Decreases physiologic shunt
• Improved ventilation in areas where perfusion remains the same
• Decreases compression/Increase FRC
Cardiac
Abdominal
• Prevent ventilator associated lung injury
• Enhances mobilization of secretions

43. Summary
• Low tidal volume, low pressure
• Open lung approach makes “sense”
– Recruitment
– High PEEP
• Minimize FiO2
• Early prone ventilation in patients meeting
criteria

44. Thank You!