Vacuum-assisted closure of the sternotomy wound: respiratory mechanics and ventilation.

BACKGROUND: Numerous authors have reported promising results with the use of vacuum-assisted closure therapy in poststernotomy mediastinitis. The negative pressure applied to the anterior mediastinum substantially exceeds the normal negative pressure in the pleural cavities, and interaction with respiratory physiology cannot be excluded. The aim of the present study was to evaluate whether the application of six clinically relevant negative pressures between -50 mmHg and -175 mmHg to the sternotomy wound affects respiratory parameters in a porcine model.
METHODS: A midline sternotomy was performed in six mechanically ventilated pigs weighing 70 +/- 3 kg. Vacuum-assisted closure therapy was applied with continuous negative pressure in a randomized order to the sternotomy wound. The following respiratory parameters were monitored by a carbon dioxide-based noninvasive monitoring system connected to the ventilator: carbon dioxide elimination, peak inspiratory pressure, peak expiratory flow, alveolar minute volume, alveolar tidal volume, expired tidal volume, static compliance, and airway resistance.
RESULTS: All pigs survived the treatment, and there was no significant change in the respiratory parameters investigated at any of the six negative pressures applied. A tendency toward increased airway resistance was noted when -175 mmHg was applied, although this change was not significant.
CONCLUSIONS: The application of negative pressure therapy in the treatment of deep poststernotomy infections is a novel modality gaining increased attention. In this study, no impairment in respiratory mechanics, ventilation, or oxygenation was detected when comparing applied pressures ranging from -50 mmHg to -175 mmHg in the sternotomy wound.