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The course of the oxygenation index before kinetic therapy or prone ventilation is decisive for the prognosis of acute respiratory failure


In acute respiratory failure (ARF), in particular acute lung injury (ALI) and respiratory distress syndrome (ARDS), an intervention in the form of rotational therapy (RT) or the prone position (PP) may improve oxygenation by recruiting alveoli situated in dorsal-dependent regions and by alteration of the ventilation/perfusion ratio. The efficacy of this interventions can be demonstrated among other parameters by the course of the oxygenation index. The aim of our study is to analyze the prognostic value of the course of the oxygenation index before and after such an intervention.


We studied 112 mechanically ventilated patients (mean age 63 ± 15.6 [SE] years) with an ARF (ARDS n = 69; ALI n = 43) at a surgical ICU in a university hospital using the American-European consensus definition in a clinical follow-up design, who received supportive therapy either with RT (n = 52; Rotorest®) or using PP (n = 60; 135° left/right-side position for at least 6 hours in each position). The physicians on duty had the freedom of choice to use one or other method guided by their clinical experience and judgement. Data collection included, apart from baseline characteristics, individual PAO2/FiO2 of patients in the course 64 hours before and 120 hours after intervention. The individual PAO2/FiO2 before and after intervention was compared with linear regression analysis for each group (linear regression procedure and t test, SPSS®).


The mean PAO2/FiO2 decreased within 64 hours until the intervention from 230 ± 91 to 178 ± 59 mmHg in all patients (mean ± SE). Patients who died (n = 64) showed a more rapid deterioration of PAO2/FiO2 during conventional ventilation in the supine position in the interval of 64 hours prior to intervention in the form of RT or PP (slope of regression straight line: RT -5.14; PP -7.14) in comparison with patients who survived their acute respiratory failure (slope RT -3.43; PP -0.57) within the scope of the critical illness (P < 0.05). Nearly all patients showed a more or less marked improvement of PAO2/FiO2 during the first 5 days after intervention after 120 hours: RT group (PAO2/FiO2 184 ± 77.28; PP group 213 ± 75 mmHg; y [all patients] = 3.9045*X + 234.61], but there was no significant difference in the linear regression analysis between survivors (slope of regression straight line: RT 0.28; PP 2.48) and nonsurvivors (RT 0.61; PP 2.03) during 120 hours after the intervention.


The course of PAO2/FiO2 seems to be more decisive for the prognosis of patients with an evolving RF than the course after supportive interventions such as RT or PP. In patients with a rapid deterioration of PAO2/FiO2 we should be aware that this may indicate an unfavourable prognosis in the sequel. Supportive measures such as RT or PP, which aim to treat the ventilation/ perfusion heterogenity, both seem to work, and therefore should be used in the early phase of ARF to reduce aggravation of lung injury and complications of mechanical ventilation.

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Lewejohann, J., Rieh, E., Börner, B. et al. The course of the oxygenation index before kinetic therapy or prone ventilation is decisive for the prognosis of acute respiratory failure. Crit Care 10 (Suppl 1), P19 (2006).

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