Ventilator associated lung injury

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Background

  • Abbreviation: VALI

Terminology

  • An acute lung injury that is suspected to have developed during mechanical ventilation is termed ventilator-associated lung injury (VALI)
  • If it can be proven that the mechanical ventilation caused the acute lung injury it is termed ventilator-induced lung injury (VILI)
  • VALI is the appropriate term in most clinical situations because it is virtually impossible to prove causation outside of the research laboratory

Epidemiology

Pathogenesis

  • VALI is alveolar injury caused by overexpansion of alveoli (volutrauma), repeated alveolar collapse and expansion (RACE), and cyclic atelectasis
  • Eventually, in serve VALI/ARDS alveoli edema/bleeding and loss of surfactant can cause complete alveoli collapse[2]

Clinical Features

Indistinguishable from ARDS

Clinical signs

  • Hypoxemic - or requiring a greater fraction of inspired oxygen (FiO2) to maintain the same arterial oxygen tension
  • Tachypneic
  • Tachycardic
  • VALI may also be associated with multiple organ dysfunction syndrome (MODS)[3]

Imaging

ARDS/VALI progression over the course of 1 week (a) Day 1 - No pathological findings. (b) Day 2 - some pulmonary consolidations in lower lobes. (c) Progressing to diffuse alveolar involvement, with “white lung” appearance (d). The normal-sized heart and vascular structures help in the differential diagnosis of pulmonary oedema due to heart failure.[4]
  • CXR - increased bilateral interstitial or alveolar opacities of any severity.
  • Computed tomography (CT) - heterogeneous consolidation and atelectasis, as well as focal hyperlucent areas that represent overdistended lung.[4]

Differential Diagnosis

Evaluation

Overview

Imaging

  • CXR
  • Echocardiography

Labs

  • BNP
    • Below 100 pg/mL favors ARDS
    • But higher levels neither confirm heart failure nor exclude ARDS[6]
  • CBC

Other

  • Noninvasive respiratory sampling
    • Lower respiratory tract can be sampled via tracheobronchial aspiration or mini-bronchoalveolar lavage (mini-BAL)
    • Tracheobronchial aspiration is performed by advancing a catheter through the endotracheal tube until resistance is met and then applying suction

Management

  • Prevention is key with ventilator lung protective settings
  • Management is the same as ARDS:
    • Continue mechanical ventilation
    • Apply lung protective settings (see Lung Injury Strategy section of Ventilation (Settings))
    • Treat underlying causes
    • Supportive care

Management by Injury Type[7]

Injury Mechanism Management
Volutrauma & Barotrauma Over-distension alveoli to pressures ≥ 30 cm H20 causing basement membrane stress
  • Maintain Plateau pressure ≤ 30 cm H20
  • Use tidal volume 6ml/kg of PBW (see EBQ:ARDSnet Trial)
Biotrauma Release of chemokines and cytokines cause influx WBC resulting in pulmonary and systemic inflammation and multi-organ dysfunction
  • Protective lung ventilation
  • Neuromuscular blockers may help.
Atelectotrauma Repeated alveolar collapse and expansion (RACE) with tidal ventilation will contribute to lung injury. Alveoli especially easy to collapse if edematous
  • High PEEP of 5 cm H20
  • Consider prone positioning
Oxygen toxicity Higher than needed O2 leads to free radicals with cause oxidative injury
  • Limit FiO2 and maintain higher PEEP.
  • Accept SaO2 at "shoulder" of oxyhaemoglobin dissociation curve (SaO2 88-94%).

Ventilator Lung Protective Settings[5]

Setting Parameter
Mode Assist Control (AC)^
Tidal Volume 6ml/kg of predicted body weight (PBW)
Respiratory Rate 12-14bpm
PEEP 5cm H20
I:E 1:2
Plateau Pressure ≤30 cm H2O

^Fully supported mode (rather than partially supported) on either volume (better studied) or pressure control (both acceptable).

Disposition

  • Admit to ICU

External Links

See Also

References

  1. Gajic O, Dara SI, Mendez JL, et al. Ventilator-associated lung injury in patients without acute lung injury at the onset of mechanical ventilation. Crit Care Med 2004; 32:1817.
  2. Rouby JJ, Brochard L (2007). "Tidal recruitment and overinflation in acute respiratory distress syndrome: yin and yang.". Am J Respir Crit Care Med 175 (2): 104–6. doi:10.1164/rccm.200610-1564ED. PMID 17200505.
  3. Plötz FB, Slutsky AS, van Vught AJ, Heijnen CJ. Ventilator-induced lung injury and multiple system organ failure: a critical review of facts and hypotheses. Intensive Care Med 2004; 30:1865.
  4. 4.0 4.1 Zompatori M, Ciccarese F, Fasano L. Overview of current lung imaging in acute respiratory distress syndrome. Eur Respir Rev. 2014;23(134):519-30. Cite error: Invalid <ref> tag; name "ESICM" defined multiple times with different content
  5. 5.0 5.1 Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. The Acute Respiratory Distress Syndrome Network. N Engl J Med 2000; 342:1301.
  6. Levitt JE, Vinayak AG, Gehlbach BK, et al. Diagnostic utility of B-type natriuretic peptide in critically ill patients with pulmonary edema: a prospective cohort study. Crit Care 2008; 12:R3.
  7. Nickson, Chris. "Ventilator Associated Lung Injury (VALI) | LITFL." LITFL Life in the Fast Lane Medical Blog. N.p., n.d. Web. 02 Aug. 2016.