Article

Regional distribution of gas and tissue in acute respiratory distress syndrome. III. Consequences for the effects of positive end-expiratory pressure

Intensive Care Medicine (Impact Factor: 5.54). 04/2012; 26(9):1215-1227. DOI: 10.1007/s001340051340

ABSTRACT Objective: To determine whether differences in lung morphology assessed by computed tomography (CT) affect the response to positive
end-expiratory pressure (PEEP).¶Design: Prospective study over a 53-month period.¶Setting: Fourteen-bed surgical intensive care unit of a university hospital.¶Patients and participants: Seventy-one consecutive patients with early adult respiratory distress syndrome (ARDS).¶Measurements and results: Fast spiral thoracic CT was performed at zero end-expiratory pressure (ZEEP) and after implementation of PEEP 10 cmH2O. Hemodynamic and respiratory parameters were measured in both conditions. PEEP-induced overdistension and alveolar recruitment
were quantified by specifically designed software (Lungview). Overdistension occurred only in the upper lobes and was significantly
correlated with the volume of lung, characterized by a CT attenuation ranging between –900 and –800 HU in ZEEP conditions.
Cardiorespiratory effects of PEEP were similar in patients with primary and secondary ARDS. PEEP-induced alveolar recruitment
of the lower lobes was significantly correlated with their lung volume (gas + tissue) at functional residual capacity. PEEP-induced
alveolar recruitment was greater in the lower lobes with “inflammatory atelectasis” than in the lower lobes with “mechanical
atelectasis.” Lung morphology as assessed by CT markedly influenced the effects of PEEP: in patients with diffuse CT attenuations
PEEP induced a marked alveolar recruitment without overdistension, whereas in patients with lobar CT attenuations PEEP induced
a mild alveolar recruitment associated with overdistension of previously aerated lung areas. These results can be explained
by the uneven distribution of regional compliance characterizing patients with lobar CT attenuations (compliant upper lobes
and stiff lower lobes) contrasting with a more even distribution of regional compliances observed in patients with diffuse
CT attenuations.¶Conclusions: In patients with ARDS, the cardiorespiratory effects of PEEP are affected by lung morphology rather than by the cause of
the lung injury (primary versus secondary ARDS). The regional distribution of the loss of aeration and the type of atelectasis
–“mechanical” with a massive loss of lung volume, or “inflammatory” with a preservation of lung volume – characterizing the
lower lobes are the main determinants of the cardiorespiratory effects of PEEP.

Key words Acute respiratory distress syndrome–Positive end-expiratory pressure–Computed tomography–Alveolar recruitment–Lung overdistension

0 Bookmarks
 · 
121 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Die Beatmung von Patienten mit akutem Lungenversagen ist eine Herausforderung für den behandelnden Arzt. In den letzten Jahren hat sich die Behandlung dieser Patienten grundlegend geändert. Neben dem Einsatz niedriger Tidalvolumina stand die Höhe des positiven endexspiratorischen Drucks („positive end-expiratory pressure“, PEEP) im Fokus der Forschung. Die Ergebnisse legen heute die Anpassung des PEEP-Levels je nach Schweregrad der Gasaustauschsstörung nahe. Zusätzlich ermöglichen die Erfassung des Rekrutierungspotenzials mithilfe der Computertomographie und die Verbesserung bettseitiger Methoden eine weitere Modifikation des PEEP. Dieser Übersichtsbeitrag gibt einen Überblick über die Möglichkeiten der PEEP-Einstellung unter Berücksichtigung neuer Forschungsergebnisse. Zusätzlich werden die grundlegenden pathophysiologischen Vorgänge von hypoxischem und hyperkapnischem akutem Lungenversagen als Basis der „optimalen“ PEEP-Einstellung dargestellt.
    Der Anaesthesist 61(4). · 0.74 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: High-frequency oscillatory ventilation (HFOV) seems ideal for lung protection in acute respiratory distress syndrome, but randomized trials have not shown a mortality reduction. The initial oxygenation response to HFOV appears to be associated with survival. Here, we discuss the mechanisms of oxygenation response to increases in airway pressure and the interpretation of the oxygenation response observed in the present study.
    Critical care (London, England) 04/2013; 17(2):133. · 5.04 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Om maximaal voordeel te halen uit rekruteermanoeuvres (RM’s) bij het acute respiratory-distress syndrome (ARDS) is het belangrijk te weten welke patiënten goed reageren op RM’s en welke factoren bijdragen aan de effectiviteit. Met deze kennis kunnen technieken worden geoptimaliseerd en toegepast wanneer de kans op succes groot is. Situaties waarin RM’s weinig kansrijk zijn, kunnen met deze kennis herkend worden zodat een zinloze en mogelijk schadelijke poging achterwege kan blijven.
    Critical Care. 04/2011; 8(2).