INTRODUCTION:Acquired pulmonary alveolar proteinosis results from impaired surfactant degradation by alveolar macrophages. This case report describes the physiologic and dynamic compliance differences between right and left lung in a patient with alveolar proteinosis, which suggests that preserved alveolar interstitial structure and fibrosis may exist in the same patient but in different regions of the lung.
CASE PRESENTATION:A 49 year old lifelong nonsmoking caucasian female was diagnosed with acquired pulmonary alveolar proteinosis by bronchoalveolar lavage and right lower lobe transbronchial biopsies. She complained of dyspnea on exertion, cough, and fatigue. Her room air oxygen saturation by pulse oximetry (SpO2) was 91% with a nadir of 86% while walking. Chest imaging demonstrated persistent bilateral middle and lower lobe infiltrates on plain films and a geographic “crazy paving pattern” by computed tomography. Lung lavage microbiologic studies were negative. Spirometry and static lung volumes were normal, but the diffusing capacity for carbon monoxide (DLCO) was severely reduced at 47% predicted. Hemoglobin was 14 grams per deciliter. Room air blood gas revealed mild hypocapnia and a PaO2 of 57 mmHg. Lactate dehydrogenase was 197 IU/L. Echocardiography was normal. Whole lung lavage (WLL) was performed with general anesthesia and a 37 French left sided double lumen endobronchial tube. Physiologic assessment of ventilation with 100% oxygen in the supine position revealed 1) bilateral lung ventilation with tidal volume (Vt) of 500 ml, peak airway pressure (PAP) 26 cmH20, PaO2 218 mmHg, oxygen saturation by pulse oximetry (SpO2)100%, 2) Left lung ventilation with Vt 450 ml, PAP 48 cm H2O, SpO2 100% to 80% within 4 minutes, 3) Right lung ventilation with Vt 450 ml, PAP 28 cm H2O, SpO2 100%, PaO2 200 mmHg. Whole lung lavage was limited to the left lung and completed with 20 liters warmed saline. Twelve hours later, the room air PaO2 was 70 mmHg, but imaging had not improved. For eight weeks, she remained symptomatic with dyspnea on exertion, cough, and fatigue. Room air PaO2 was 61 mmHg and DLCO was 53 % predicted. During the second WLL, physiologic assessment yielded similar results, most notably left lung Vt 450 ml producing a PAP 48 cmH2O with rapid desaturation. Bilateral lung lavage was performed, but right lung lavage was poorly tolerated and terminated after 10 liters warmed saline. Blood gases documented a progressive combined metabolic and respiratory acidosis. As the pH decreased below 7.2 and the PCO2 remained greater than 50 mmHg, the procedure was aborted. Days after the second WLL, she reported decreased cough and improved functional capacity. Two months later, she reported rare coughing, little fatigue, and significantly improved functional capacity. Resting SpO2 was 95% with a nadir of 91% while walking. Blood gases showed PaO2 78 mmHg, and DLCO improved to 72 % predicted.
DISCUSSIONS:The pathophysiology of alveolar proteinosis is better understood since the role of granulocyte macrophage colony stimulating factor (GM-CSF) in surfactant homeostasis was elucidated. WLL remains the treatment of choice, but results from GM-CSF experimental therapies appear promising. Although fibrosis is rare, some areas of the lung might have fibrosis while others have preserved alveolar architecture. Physiologic assessment in this patient suggests a different pathologic process in the left lung which might be determined by biopsies.
CONCLUSION:WLL during general anesthesia with neuromuscular blockade affords a unique opportunity to individually assess right and left lung physiology in patients with alveolar proteinosis. Results may reflect different pathologic processes. Whether this information can be combined with clinical and lab data to influence therapeutic options and efficacy may be determined in future studies with WLL, GM-CSF, or both.
DISCLOSURE:Perry Nystrom, No Financial Disclosure Information; No Product/Research Disclosure Information