RESPIRATORY SYNCYTIAL VIRUS-INFECTION REINFORCES REFLEX APNEA IN YOUNG LAMBS

To evaluate the effect of respiratory syncytial virus (RSV) infection on reflex apnea elicited by application of water on the laryngeal muco sa, 11 healthy, term lambs were chronically instrumented at 2 wk of ag e. Six lambs were inoculated with bovine RSV, and five lambs were mock -infected. The lambs were studied awake and unsedated before and 4, 8, 14, and 21 d after infection. RSV infection was associated with sligh t rhinorrhea and with moderately increased tracheal mucous discharge. There was an average increase of 0.5-degrees-C in body temperature. Ar terial PH, PO2, and PCO2 remained within the normal range. The ventila tory response to laryngeal chemostimulation measured as the percentage of decrease in ventilation from control was significantly (p < 0.05) larger among the infected animals when compared with controls on d 4 a nd 8. There were no differences in indices of respiratory drive (airwa y occlusion pressure and mean inspiratory flow), ventilatory response to hypoxia (0.10 fraction of inspired O2), or hypercarbia (0.03 fracti on of inspired O2). We speculate that RSV infection alters the sensiti vity of the laryngeal chemoreceptors so that a prolonged or even fatal apnea may result from stimulation of these receptors. These results m ay be relevant to the pathogenesis of sudden infant death syndrome ass ociated with RSV infection.