Surfactant proteins-A and -B are elevated in plasma of patients with acute respiratory failure.
Surfactant protein-A (SP-A) leaks into the circulation of patients with acute respiratory distress syndrome (ARDS) or acute cardiogenic pulmonary edema (APE) in a manner inversely related to lung function. Since surfactant protein-B (SP-B) is synthesized as a precursor considerably smaller than alveolar SP-A, we investigated whether it enters the circulation more readily. Reactivities consistent with SP-B proprotein (approximately 42 to approximately 45 kD) and the approximately 25 kD processing intermediate were detected in plasma. Plasma immunoreactive SP-B levels were significantly higher in ARDS (8,007+/-1,654 ng/ml [mean+/-SEM], n = 22) and APE (3,646+/-635 ng/ml, n = 10) patients compared with normal subjects (1,685+/-58 ng/ml, n = 33) and ventilated patients with no cardiorespiratory disease (1,829+/-184 ng/ml, n = 7). All groups had plasma SP-B/SP-A ratios approximately 6- to approximately 8-fold higher than in normal lavage or ARDS tracheal aspirate fluid, consistent with protein sieving. During admission, both plasma SP-B and the SP-B/SP-A ratio were inversely related to blood oxygenation (PaO2/FIO2) (p < 0.0001 and p < 0.025, n = 260 from 39 patients; Spearman) and static respiratory system compliance (deltaV/deltaP) (p < 0.0001 and p < 0.01, n = 168 from 25 patients). We describe in detail three patients and conclude that immunoreactive SP-B enters more readily than SP-A, is cleared acutely, and provides a better indicator of lung trauma.
Doyle
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IR
Department of Human Physiology, School of Medicine, Flinders Medical Centre, Adelaide, Australia.
Bersten
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AD
Nicholas
T E
TE
D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers; D005260:Female; D006242:Haptoglobins / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D011510:Proteolipids / Q000097:blood*; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants / Q000097:blood*; D012121:Respiration, Artificial; D012128:Respiratory Distress Syndrome / Q000097:blood / Q000150:complications / Q000628:therapy; D012129:Respiratory Function Tests; D012131:Respiratory Insufficiency / Q000097:blood* / Q000209:etiology / Q000503:physiopathology; D015656:Respiratory Mechanics
D015415:Biomarkers; D006242:Haptoglobins; D011510:Proteolipids; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants