Fachbereich Veterinärmedizin



    Increasing the Inspiratory Time and I:E ratio during Mechanical Ventilation Aggravates Ventilator-induced Lung Injury in Mice (2015)

    Zeitschriftenartikel / wissenschaftlicher Beitrag
    Müller-Redetzky, Holger C
    Felten, Matthias
    Hellwig, Katharina
    Wienhold, Sandra-Maria
    Naujoks, Jan
    Opitz, Bastian
    Kershaw, Olivia (WE 12)
    Gruber, Achim D (WE 12)
    Suttorp, Norbert
    Witzenrath, Martin
    Critical care (London, England); 19 — S. 23
    ISSN: 1466-609x
    DOI: 10.1186/s13054-015-0759-2
    Pubmed: 25888164
    Institut für Tierpathologie

    Robert-von-Ostertag-Str. 15
    Gebäude 12
    14163 Berlin
    Tel.+49 30 838 62450 Fax.+49 30 838 62522

    Abstract / Zusammenfassung

    Lung-protective ventilation reduced acute respiratory distress syndrome (ARDS) mortality. To minimize ventilator-induced lung injury (VILI), tidal volume is limited, high plateau pressures are avoided, and positive end-expiratory pressure (PEEP) is applied. However, the impact of specific ventilatory patterns on VILI is not well defined. Increasing inspiratory time and thereby the inspiratory/expiratory ratio (I:E ratio) may improve oxygenation, but may also be harmful as the absolute stress and strain over time increase. We thus hypothesized that increasing inspiratory time and I:E ratio aggravates VILI.

    VILI was induced in mice by high tidal-volume ventilation (HVT 34 ml/kg). Low tidal-volume ventilation (LVT 9 ml/kg) was used in control groups. PEEP was set to 2 cm H2O, FiO2 was 0.5 in all groups. HVT and LVT mice were ventilated with either I:E of 1:2 (LVT 1:2, HVT 1:2) or 1:1 (LVT 1:1, HVT 1:1) for 4 hours or until an alternative end point, defined as mean arterial blood pressure below 40 mm Hg. Dynamic hyperinflation due to the increased I:E ratio was excluded in a separate group of animals. Survival, lung compliance, oxygenation, pulmonary permeability, markers of pulmonary and systemic inflammation (leukocyte differentiation in lung and blood, analyses of pulmonary interleukin-6, interleukin-1β, keratinocyte-derived chemokine, monocyte chemoattractant protein-1), and histopathologic pulmonary changes were analyzed.

    LVT 1:2 or LVT 1:1 did not result in VILI, and all individuals survived the ventilation period. HVT 1:2 decreased lung compliance, increased pulmonary neutrophils and cytokine expression, and evoked marked histologic signs of lung injury. All animals survived. HVT 1:1 caused further significant worsening of oxygenation, compliance and increased pulmonary proinflammatory cytokine expression, and pulmonary and blood neutrophils. In the HVT 1:1 group, significant mortality during mechanical ventilation was observed.

    According to the "baby lung" concept, mechanical ventilation-associated stress and strain in overinflated regions of ARDS lungs was simulated by using high tidal-volume ventilation. Increase of inspiratory time and I:E ratio significantly aggravated VILI in mice, suggesting an impact of a "stress/strain × time product" for the pathogenesis of VILI. Thus increasing the inspiratory time and I:E ratio should be critically considered.