Letter to the Editor: Kinetic therapy in ARDS patients treated with extracorporeal membrane oxygenation

Litmathe and colleagues reported two cases of veno-venous extracorporeal membrane oxygenation (vv-ECMO) combined with 135° prone positioning. ¹ We greatly appreciate their efforts not to abandon adjunctive strategies such as kinetic therapy in adult respiratory distress syndrome (ARDS) patients treated with vv-ECMO. Reports dealing with this issue are lacking and, therefore, their report is very important. However, Litmathe and colleagues only performed very brief periods (4 hours a day) of prone positioning. Therefore, one might suggest that the improvements in gas exchange observed in their patients were more likely to be related to recovery from the underlying disease than related to the prone positioning.

Kinetic therapy is an accepted adjunctive and rescue strategy to enhance oxygenation due to several mechanisms, such as alveolar recruitment or better ventilation/perfusion matching in patients with severe ARDS (PaO₂/FiO₂-ratio <100 mmHg). In a current meta-analysis, this strategy was associated with a survival benefit in this subgroup of patients. ² However, according to recent recommendations and clinical data, ³ prone positioning should be extended to a minimum of 12 hours a day in order to maximise its effects on gas exchange. Although this prolonged period of kinetic therapy might also be possible in ECMO-treated patients, as the authors point out, a highly trained team is necessary to perform this adjunctive therapy safely during ECMO due to possible devastating complications such as cannula dislocation or deviation. Therefore, position changes from supine to prone or vice versa should only be performed when an experienced team is present. This could be the advantage of continuous axial rotation therapy in patients on extracorporeal life support, since the patient is fixed in the pivotal bed and there is no need of intermittent position changes. During a 72-hour trial, continuous axial rotation had, indeed, a similar effect on oxygenation in comparison with prone positioning for about 20-22 hours a day. ⁴ Litmathe and colleagues appraised their two patients with body mass indexes (BMI) >50 kg/m² to be unsuitable for continuous axial rotation. However, there are also clinical situations, e.g. multiple trauma patients with unstable spine fractures or severe head injury, in which prone positioning is not optimal or even is contraindicated. Both forms of kinetic therapy, prone positioning and continuous axial rotation therapy, are performed in our institution in patients with severe ARDS, irrespective of ECMO therapy. Similar to our colleagues, the use of kinetic therapy during ECMO was associated with good clinical outcome and was devoid of major complications (see Figure 1).

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Figure 1.

Continuous axial rotation in a patient with vv-ECMO. The oxygenator and the centrifugal pump drive are mounted at the pivoting part of the bed. The drive console and the heater unit are located on a table beside the bed. (Department of Anaesthesia and Critical Care, University of Würzburg, Germany.)

However, since clinical data are still lacking, further studies are needed to evaluate the efficacy and side effects of positioning therapy in combination with vv-ECMO in patients with ARDS.