Over the past decade, extracorporeal membrane oxygenation (ECMO) has been increasingly used to support patients with cardiorespiratory failure.1,2 Safety and survival of patients on ECMO has improved both because of improvement in ECMO technology and better management practices such as low tidal volume ventilation and effective anticoagulation monitoring. Proponents of ECMO believe that it provides “lung rest” through the use of low tidal volume (6 ml/kg) and ultralow tidal volume (<6 ml/kg) lung-protective ventilation.3 However, the use of very low tidal volume strategies can result in low dynamic respiratory compliance, with a potential for increased retention of secretions in the airway.4 This can lead to mucous plugging and airway collapse resulting in increased time on ECMO. The role of using pulmonary secretion clearance techniques such as frequent patient repositioning, chest physiotherapy via automated bed percussion or other percussion devices, and regular bronchoscopies in patients on ECMO is unclear. In this report, we describe the role of automated rotatory percussion bed (ARPB) and frequent bronchoscopies for pulmonary secretion clearance in a pilot study of four patients supported with ECMO and low tidal volume ventilation.
We used a rotatory percussion bed in four patients with severe acute respiratory distress syndrome (ARDS) receiving ECMO. Demographics, indications for ECMO, mechanical ventilation (MV) settings before ECMO, and type of support are shown in Table 1. Before ECMO, patients had received MV for an average of 7 days. Mean partial pressure of oxygen in arterial blood (PaO2)/fraction of inspired oxygen (FiO2) (P/F) ratio at ECMO initiation was 58. All patients received support with venovenous (VV)-ECMO via a double-lumen internal jugular catheter (DLC). All patients received anticoagulation with heparin. Lung-protective ventilation strategy was used after initiation of ECMO, although different modes of ventilation were used (Table 2). Despite optimal ventilator adjustments, peak (38 cm H2O) and plateau pressures (34 cm H2O) remained high in the patient ventilated using volume control mode, whereas the driving pressures (set inspiratory pressures) to attain desired tidal volumes remained high in the other three patients ventilated with pressure control ventilation (mean: 31 cm H2O). This was attributed to both ARDS and copious amounts of pulmonary secretions leading to possible mucous plugging. To facilitate secretion clearance, we performed a therapeutic bronchoscopy in all patients and decided to use an ARPB (Triadyne Proventa, Getinge AB, Getinge, Sweden). These beds were programmed to perform an automated side-to-side tilt maneuver (45°) every 2 hours. In addition, the bed provided timed intermittent chest wall percussion. We evaluated the changes in respiratory mechanics and oxygenation after 4 days of ARPB use. We noted a substantial reduction in peak and plateau pressures in two patients on assist control-volume control ventilation, while the driving pressures (inspiratory pressure) to attain the desired tidal volumes in patients on assist control-pressure control ventilation (Table 2) also decreased. In addition, mean P/F (109 pre-ARPB vs. 157 post-ARPB), PEEP (10 cm H2O vs. 8 cm H2O), and FiO2 (0.88 vs. 0.52) improved after initiation of ARPB (Table 3). The improvements in the respiratory mechanics and oxygenation helped us to initiate ECMO weaning. Tracheal aspirate culture data were positive in all four patients, and antibiotic coverage was selected accordingly. Serial chest radiographs demonstrated improvement in lung aeration. Automated rotational percussion bed was used for a mean duration of 8 days, and an average of 3 bronchoscopies per patient was performed.
Lung-protective ventilation strategies such as low tidal and ultralow tidal volume ventilation have shown a mortality benefit in ARDS and other causes of respiratory failure.5 However, it may lead to extremely low dynamic compliance states causing distal airway collapse and obstruction of mucociliary secretion clearance.4 Ventilator settings that produce flow bias have a major effect on mucus movement. Expiratory flow bias associated with intrinsic positive end-expiratory pressure generated by elevated minute ventilation moves mucus toward the airway opening, whereas intrinsic positive end-expiratory pressure generated by increased airway resistance moves the mucus toward the lungs.6–8 Chest physiotherapy can augment expiratory flow and assist in secretion clearance during positive pressure ventilation.6,9,10 Common chest physiotherapy techniques used are manual percussion/vest therapy, high-frequency percussive ventilation, and rotational vibration beds. Similarly, flexible bronchoscopy can be safely used to aid in secretion clearance in ARDS patients on MV.
However, during ECMO support, institution of chest physiotherapy (CPT) may be delayed or avoided because of concerns of dislodgment of ECMO cannulas and potential bleeding or mechanical complications. Similarly, excessive coughing during suctioning or bronchoscopy can lead to increased intrathoracic pressures and transient reductions in ECMO flow.
During our literature search, we found little data regarding the use of CPT and bronchoscopy in adult ECMO patients. We found two reports describing the improvement in lung dynamics with the use of chest physiotherapy in an adult patient on ECMO. Michaels et al.11 used high-frequency percussive ventilation in adult ECMO patients and showed a reduced duration on ECMO. Similarly, Cork et al.12 described the use of various chest physiotherapy and recruitment techniques in adult ECMO patient. Several reports in the pediatric literature have demonstrated the beneficial role of bronchoscopy in the secretion management of pediatric ECMO patients. Yehya et al.13 in a case–control study in pediatric ECMO patients showed that frequent bronchoscopy and high-frequency percussive ventilation resulted in greater number of extracorporeal life support free days. Kamat et al.,14 in a retrospective review on 79 children on ECMO, showed that bronchoscopy while on ECMO was safe and useful for secretion clearance. Our case series describe for the first time the use of rotational vibration beds and frequent bronchoscopies for successful secretion management in adult ECMO patients with excessive airway secretions. Decision to use ARPB was made by an attending physician based on qualitative bronchoscopy findings of increased airway secretions. Frequent repositioning of dependent portions of the lung and chest wall percussion by the ARPB resulted in a reduction of lung atelectasis, less intrapulmonary shunting, and improved mucociliary transport.15,16 In addition, the use of bronchoscopy assisted in secretion clearance. These interventions contributed to an improvement in respiratory mechanics and oxygenation; however, further studies are needed to evaluate whether these translate into a reduction in duration of ECMO support. We did not encounter any adverse events with ARPB use. Minor blood-tinged mucoid secretions were observed with repeated airway suctioning. No major intrapulmonary or DLC cannula site bleeding was noted. In addition, no displacement or dislodgment of the DLC or endotracheal tube was noted with ARPB or bronchoscopy use. Bronchoscopy was not associated with any hypoxia or significant change in ventilator or ECMO settings. During the study period (January 1, 2014, to December 31, 2015), a total of 90 ECMO runs were performed (47 VV [52%], 41 VA [46%], and 2 mixed configuration [2%]) at our institution. Automated rotational percussion bed was used in a minority of ARDS patients (4 of 40 [10%]) supported with VV-ECMO during the study period. Barriers to the more frequent use of ARPB in other patients included bed availability, lack of available safety data in ECMO patients, and absence of a defined protocol for clinical use at that time.
Based on our experience, use of chest physiotherapy, frequent body repositioning, and bronchoscopy may be helpful in the management of pulmonary secretions in patients supported with ECMO. Larger studies are needed to validate the safety and utility of ARPB and other CPT techniques in patients receiving lung-protective ventilation on ECMO.
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