Ventilator associated lung injury

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

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]
InjuryMechanismManagement
Volutrauma & BarotraumaOver-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)
BiotraumaRelease of chemokines and cytokines cause influx WBC resulting in pulmonary and systemic inflammation and multi-organ dysfunction
  • Protective lung ventilation
  • Neuromuscular blockers may help.
AtelectotraumaRepeated 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 toxicityHigher 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]
SettingParameter
ModeAssist Control (AC)^
Tidal Volume6ml/kg of predicted body weight (PBW)
Respiratory Rate12-14bpm
PEEP5cm H20
I:E1:2
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

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. Zompatori M, Ciccarese F, Fasano L. Overview of current lung imaging in acute respiratory distress syndrome. Eur Respir Rev. 2014;23(134):519-30.
  5. 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.
This article is issued from Wikem. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.