EuAsia 2017 Day 2: Spontaneous breathing and ARDS

Role of NIV (M Antonelli)

Mechanism of VILI: role of transpulmonary pressure (PL)

PL = Paw (ventilator) – Ppl (muscle)

Low Vt is almost impossible to obtain during NIV

The problem with ARDS trials….

  • Different disorders lead to ARDS
  • Different pts respond differently

Recognition of ARDS by clinicians is poor especially mild ARDS

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References

Fifty Years of Research in ARDS. Spontaneous Breathing During Mechanical Ventilation – Risks, Mechanisms &Amp; Management

Neuromuscular Blockers in Early Acute Respiratory Distress Syndrome

The LUNG SAFE study: a presentation of the prevalence of ARDS according to the Berlin Definition! 

 

HFOT (CY Lim)

Physiological effects

  • Warmth and humidity in upper airways
  • Reduction in inspiratory resistance
  • Positive pressure in nasopharynx
  • Washout of nasopharyngeal dead space

HFNC for ARDS

  • Hypoxia
    • increase end-expiratory volume
    • help homogenise distribution of ventilation
  • High dead space fraction
    • increase tidal volume
    • decrease Vd/Vt

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References

High-Flow Oxygen through Nasal Cannula in Acute Hypoxemic Respiratory Failure

Oxygen delivery through high-flow nasal cannulae increase end-expiratory lung volume and reduce respiratory rate in post-cardiac surgical patients

Nasal highflow improves ventilation in patients with COPD 

 

The dark side of spontaneous breathing in ARDS (T Yashida)

Harm of spontaneous breathing

  • Better oxygenation with paralysis
  • Less inflammation
  • Less work of breathing after paralysis
  • Improve mortality with early paralysis (in severe ARDS)

Pt may have a PS 5 and PEEP of 5 but with strong effort, can generate Vt of 12ml/kg –> barotrauma

The beneficial effects of spontaneous breathing is seen only in mild ARDS

Mechanism of harm

  • Large Vt and Pl
    • The negative pressure of SV can lead to high Pl
  • Pendelluft
    • Injured lung do not have homogenous ventilation
    • Worsening inflammation
  • Worsening capillary leak
  • Asynchrony

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References

Spontaneous Effort Causes Occult Pendelluft during Mechanical Ventilation

Fifty Years of Research in ARDS. Spontaneous Breathing During Mechanical Ventilation – Risks, Mechanisms & Management