Static lung-lung interactions in unilateral emphysema SUSAN S. MARGULIES, ROBERT W. SCHRINER, MARK A. SCHROEDER, AND ROLF D. HUBMAYR Division of Thoracic Diseasesand Internal Medicine and Department of Physiology and Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55905 Biophysics, MARGULIES, SUSAN S., ROBERT W. SCHRINER, MARK A. SCHROEDER, AND ROLF D. HUBMAYR. Static Zung-lunginterac- tions in unilateral emphysema. J. Appl. Physiol. 73(Z): 545-551, 1992.-Motivated by the introduction of single-lungtransplan- tation into clinical practice, we comparedthe static mechanical properties of the respiratory system in six supine dogsbefore (at baseline) with those after the induction of unilateral em- physema. Relaxation volume (Vrel), total lung capacity (TLC), and static compliance of the emphysematous lung increased to 214 t 68, 186 t 39, and 253 t 95% (SD) of baseline, respec- tively. Vrel of the nonemphysematous lung fell to 81 k 28% of baseline, with no significant change in TLC of the nonemphy- sematous lung or its pressure-volume relationship, indicating that unilateral hyperinflation does not cause dropout of contra- lateral lung units. After unilateral emphysema,the chest wall shifted to a higher unstressed or neutral volume (when pleural pressureequalsatmospheric pressure)in three of six animals, minimizing the anticipated decrease in lung recoil pressureat the higher respiratory systemVrel. The pattern of relative lung emptying in the intact dog and in the excisedlungs was similar during stepwise deflations from TLC, suggestingthat mean pleural pressure of the hemithoracesis equal.We conclude that in the dog the static volume distribution between emphysema- tous and nonemphysematous lungs is determined only by dif- ferencesin lung recoil and compliance. single-lung transplantation; chest wall adaptation WITH THE INTRODUCTION of single lung transplantation (SLT) into clinical practice, questions have been raised about the mechanisms of interaction between two lungs with different mechanical properties. Failure of early SLT patients with chronic obstructive pulmonary dis- ease (COPD) was attributed to unfavorable lung-lung in- teraction (20), and SLT was discontinued for emphy- sema until 1989, when two centers reported a successful outcome from SLT in a few patients with COPD (13,23). The aim of this study was to evaluate the effects of a unilateral loss of lung recoil on the interpulmonary vol- ume and transpulmonary pressure distribution in dogs to gain insight into the mechanisms that govern lung-lung interdependence. With this goal in mind, we studied the static mechanical properties of lungs and chest wall in dogs before and after the induction of unilateral emphy- sema (UE) with papain (21). Specifically, we investigated the treatment-induced changes in the relaxation volume (Vrel) and the static compliance of each lung, the chest wall recoil and compliance, and we also determined the mean pleural pressure (Ppl) over each lung at Vrel ana auring quasistatic aerlations from total lung capac- ity (TLC). METHODS Instillation of elastolytic enzymes, such as papain, in- duces emphysema in animals that histologically and functionally resembles human panacinar emphysema (19). In this study, UE was produced in dogs with a tech- nique similar to that described by Mink (15). Eight adult mongrel d .ogs (21 yr) we ighing 28-44 kg were anesthe- tized with pentobarbi tal sodium (30 mg/kg), i ntubated with a Y-shaped dual-lumen endotracheal tube (Kott- maier; Willy Rusch), and placed in a lateral decubitus posture. A mixture of 4 ml (25 mg/ml) of papain solution (type III; Sigma Chemical) diluted in 40 ml of sterile nor- mal saline was injected through a PE-200 catheter into the airways of the dependent lung. After the instillation, the dogs were mechanically ventilated for 6 h (tidal vol- ume = 15 ml/kg, fractional 0, concentration = 0.6). Pen- icillin and gentamicin were administered every 12 h for a total of four doses to prevent bacterial infection. The instillation procedure was repeated at approximately weekly intervals for an average of four treatments. Two dogs died because of pulmonary hemorrhage and hypoxic respiratory failure during the induction of emphysema. Of the remaining six dogs, the left lung was treated in dogs 1-3 and the right lung in dogs 4-6. Measurements of Vrel and the static elastic properties of the intact respiratory system wrere made before the initial papain instillation (baseline values) and agai n at least 3 mo after the final treatment. On these occasions, anteroposterior projection X-rays were taken at Vrel to document respiratory system geometry. The dogs were anesthetized with pentobarbital sodium (25-30 mg/kg), placed in the supine posture, intubated with a Kottmaier dual-lumen endotracheal tube, and mechanically venti- lated with a Harvard pump. Complete separation be- tween the airways of right and left lung was assu med if a right-to-left airway pressure difference of 10 cmH,O could be maintained during a single lung inflation. To estimate pleural pressure, a balloon catheter was placed in the mid- to lower esophagus. Its position was adjusted until the drop in esophageal pressure (Pes) during inspi- ratory efforts against an occluded airway fell to within 1 cmH,O and/or 10% of the change in airway pressure (Pao) (2). Right and left Pao were recorded from the oral ends of the respective endotracheal tube lumina. Gas flow to each lung was measured with a pneumotacho- 0161-7567/92 $2.00 Copyright 0 1992 the American Physiological Society 545