PMC4531190_01
Chest X-rays and CT scan. Patchy bilateral infiltrates can be seen in the first chest X-ray made immediately postoperatively (top left). After three days of noninvasive ventilation and two days of invasive ventilation, the CT scan of the lungs was performed at a PEEP of 15 cm H2O (right) showing bilateral dorsal infiltrates reaching from cranial (top right) to caudal lung regions (down right). The chest X-ray made after CENPV during the following day shows impressive regression of the infiltrates and pleural effusions (bottom left), corresponding to improved oxygenation.
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Administration of intravenous furosemide administrations had no effect, and the initial chest X-ray revealed patchy bilateral infiltrates but without enlarged heart (Figure 1). Two days later the patient was tracheostomized; CT scans of the lungs were performed at a PEEP level of 15 cm H2O and showed bilateral patchy infiltrates and dorsal consolidation extending from cranial to caudal lung regions (Figure 1).
Course of gas exchange and ventilatory pressures. After three days of noninvasive positive-pressure ventilation, the patient was intubated and ventilated in a pressure-controlled mode. Three days later, negative-pressure ventilation was commenced in combination with conventional pressure support (gray columns). In both ventilatory modes, inspiratory pressures are shown as red and expiratory pressures as green lines. Ventilatory pressures represent inspiratory plateau pressures and positive end-expiratory pressures (PEEP) during conventional positive-pressure ventilation and maximum or minimum chamber pressures during negative-pressure ventilation.
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During the following day, the PaO2/FiO2 ratio again decreased below 200 mmHg, despite high PEEP values of not less than 15 cm H2O (Figure 2) that were not sufficient to maintain lung volumes; even recruitment maneuvers using airway pressures up to 85 cm H2O were unable to substantially improve oxygenation. We combined CENPV with conventional PEEP of about 8 cm H2O and pressure support of 4-12 cm H2O (Figure 2), applying tidal volumes of 6-8 mL/kg predicted bodyweight. During the first application of the chamber ventilator (that lasted for 7 hours), the PaO2/FiO2 value increased from 236 to more than 300 mmHg (Figure 2), and alveolar infiltrates showed an impressive decrease. However, it was only during the second application time (after eight hours of CENPV) that the PaO2/FiO2 value increased to more than 500 mmHg (Figure 2), indicating significant recruitment of lung volume without the use of any recruitment maneuvers. Before opening the chamber respirator again, the PEEP level was elevated by at least 8 cm H2O to compensate for the discontinuation of the end-expiratory negative chamber pressure (Figure 2). Subsequently, higher levels of pressure support became necessary and oxygenation deteriorated again, with PaO2/FiO2 values mainly between 200 and 300 mmHg (Figure 2).
Patient with ARDS in the chamber respirator. CENPV has been discontinued and the chamber opened to enable better access for nursing procedures. The PEEP was elevated before opening the chamber to compensate for discontinuation of end-expiratory negative chamber pressure, and the patient is breathing spontaneously while receiving pressure support from the conventional ventilator. The separate pump unit (bottom right) was manufactured by Coppa S.r.l. (Biella, Italy) and was usually integrated into a tank respirator.
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In this situation, six days after the development of ARDS and three days after invasive CPPV, we decided to apply CENPV with the chamber respirator (Figure 3). Gull-wing doors at both sides and one at the head enabled rapid access to the intubated patient who was placed completely inside the chamber (Figure 3). Following cessation of CENPV, the patient breathed spontaneously at this high PEEP level with pressure support of only 4-8 cm H2O (Figure 3).