Effects of prone position ventilation and kinetic therapy in acute respiratory failure

Introduction

In acute respiratory failure (ARF), in particular acute lung injury (ALI) and respiratory distress syndrome (ARDS), change from the supine position (SP) to the prone position (PP) or the use of kinetic therapy can improve oxygenation by recruiting alveoli situated in dorsal-dependent regions of the lung and by alteration of the ventilation/perfusion ratio. The efficacy of this intervention can be demonstrated by the course of oxygenation index. The aim of our study is to compare prone position ventilation (PP) and kinetic therapy (KT) in the first 5 days after intervention in patients with acute respiratory failure.

Methods

We studied n = 149 patients with ARF at a surgical ICU in a university hospital using the American–European consensus definition in a clinical follow-up design. The physicians on duty had the freedom of choice to use PP or KT guided by their clinical experience. One hundred and eleven patients (ALI: n = 18/ARDS: n = 93; mean age 66 ± 13 [standard error] years) were ventilated intermittently in SP and PP (135° left/right-side position) for at least 6 hours per day for supportive treatment of respiratory failure. Thirty-eight patients (ALI: n = 16/ARDS: n = 22; mean age 60 ± 16 [standard error] years) were treated with kinetic therapy using the Rotorest^®-bed (60° left/right side; KCI).

Data collection included, apart from baseline characteristics, the individual oxygenation index of the patients in the course of the first 5 days after intervention. The individual oxygenation index before and after intervention was compared with linear regression analysis for each group (linear regression procedure and t test; SPSS^®).

Results

During conventional ventilation in the supine position there was no significant improvement in oxygenation in both groups. The mean oxygenation index (PaO₂/FiO₂) decreased until intervention to 157.6 ± 0.48 mmHg in the PP group and to 165.8 ± 1.47 mmHg in the KT group (mean ± standard error of the mean). Both forms of positional changes lead to a distinct improvement of oxygenation: after 120 hours the oxygenation index in the PP group was 219.67 ± 0.66 and in the KT group was 197.89 ± 2.07 mmHg. Subsequent to intervention the PP group showed a more rapid and significant increase of oxygenation index in comparison with the KT group as the equations of linear regression show: y[PPV] = 4.4618 × X + 188.72 and y[KT] = 3.9349 × X + 160.47. Mortality was 62.2% in the PP group and 63.2% in the KT.

Discussion

In ARF the change of body position in the form of PP and KT leads to an improvement of oxygenation. PP seems to have a more rapid and marked effect than KT. It is remarkable that mortality is nearly the same in both groups, despite the unequal group size. PP is a comparatively simple strategy to treat the heterogenity of ventilation and perfusion in ARF and needs no special technical equipment, while KT is an advantageous alternative in patients with contraindications for PP.