One-lung ventilation in a patient with an organizing empyema and severe idiopathic pulmonary fibrosis
Editor—We present the anaesthetic management for lung decortication of a patient with an organizing empyema and underlying severe idiopathic pulmonary fibrosis.Patients with pulmonary fibrosis have an increased risk of pneumothorax,1 resolution of which can be markedly delayed because of the high negative pleural pressures necessary for the expansion of stiff, fibrotic lungs. Consequently prolonged chest-tube drainage in turn predisposes to the development of an organizing empyema which frequently requires thoracotomy and definitive lung decortication, rather than a simpler thoracoscopic procedure as is appropriate for early empyema.2 3
Our patient was a 77-yr-old male who had been admitted with a right pyo-pneumothorax complicating a lower lobe broncho-pneumonia. Despite intensive management with chest drains and Heimlich valves, the lung had never re-expanded fully. (See images from the CT scan before decortication in Fig. 1.) Pulmonary function tests over the preceding 12 months had consistently shown a marked restrictive pattern with severely reduced gas transfer. (FEV1 53%, TLC 51% and DLCO 27% of predicted values.) PaO2 was 7.2 kPa and PaCO2 7.4 kPa, breathing air.
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During surgery, lung separation was achieved with a left-sided 39FG Sher-i-bronch double-lumen tube (Sheridan, Hudson Respiratory Care Inc., Temulca, CA, USA) and its correct position confirmed with fibreoptic bronchoscopy. When one-lung ventilation was initiated, hand-ventilation was used initially in order to assess a considered optimal pattern for mechanical ventilation. This translated to a ventilatory frequency of 14 bpm, a tidal volume of 550 ml and an inspiratory pause of 40% of the inspiratory phase. With the ventilator set to produce these outcomes, the peak airway pressure during one-lung ventilation was 37 cm H2O and the plateau pressure 26 cm H2O.
The high inflation pressures might well have resulted in an increased fraction of the pulmonary blood flow passing to the non-dependent, non-ventilated lung,4 and an oxygen source at ambient pressure was therefore connected to the lung to allow ongoing apnoeic oxygenation during its collapse.5 The oxygen source was in the form of a 3 litre reservoir bag approximately three-quarter filled with oxygen, which was connected to the airway of the non-ventilated lung at the time one-lung ventilation was initiated. With the onset of one-lung ventilation, and before the chest was opened, the reservoir bag distended and returned to its pre-distension volume with each cycle of positive pressure ventilation of the dependent lung.5 After the chest was opened, the bag movement did not cease but continued, albeit to a less pronounced degree, for the whole of the approximately 1 h period of one-lung ventilation. Over this same period, the oxygen reservoir also progressively reduced in size. Most likely, the thick empyema membrane that encased the visceral pleura served to hold the lung partially expanded to the extent that at least some of its airways remained open, so enabling ongoing apnoeic oxygenation. This may well have played an important part in maintaining the SpO2 at 99–100%, for the 1 h duration of one-lung ventilation in this extremely compromised patient.
The early postoperative course was uneventful and the decorticated lung was well expanded initially, but it partially re-collapsed on the second postoperative day. Since then, the lung never re-expanded fully, and ongoing management has required a permanent pig-tail chest drain and attached Heimlich valve. A CT scan at follow-up 5 months after surgery showed the persisting right pneumothorax to occupy 50% of the hemithorax, although the lung itself was more uniformly and better expanded than before the decortication. No further surgery is planned.
The authors believe that during one-lung ventilation in the presence of empyema, and especially where there is also generalized lung pathology (such as pulmonary fibrosis and high ventilating pressures), it is rational to attach an oxygen source to the non-ventilated lung for the purpose of enabling possible ongoing apnoeic oxygenation.
Adelaide, South Australia
*E-mail: pfitznerwines{at}ozemail.com.au
References
1 Franquet T, Giménez A, Torrubia S, Sabaté JM, Rodriguez-Arias JM. Spontaneous pneumothorax and pneumomediastinum in IPF. Eur Radiol 2000; 10:108–13[Medline]
2 Landreneau RJ, Keenan RJ, Hazelrigg SR, Mack MJ, Naunheim KS. Thoracoscopy for empyema and hemothorax. Chest 1996; 109:18–24
3 Cassina PC, Hauser M, Hillejan L, Greschuchna D, Stamatis G. Video-assisted thoracoscopy in the treatment of pleural empyema: stage-based management and outcome. J Thorac Cardiovasc Surg 1999; 117:234–8
4 Conacher ID, Dark J, Hilton CJ, Corris P. Isolated lung transplantation for pulmonary fibrosis. Anaesthesia 1990; 45:971–5[Medline]
5 Pfitzner J and Pfitzner L. The theoretical basis for using apnoeic oxygenation via the non-ventilated lung during one-lung ventilation to delay the onset o f arterial hypoxaemia. Anaesth Intensive Care 2005; 33:794–800[Medline]
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