Blood RSV RNA detection Correlates with Acute Airway Obstruction. Fig. 5A. Airway obstruction assessed by Penh (Y axis) significantly increased in mice infected with live RSV. On day 5 post-infection Penh values were significantly higher in RSV infected mice compared with mice inoculated with HI-RSV and non-infected controls n = 12-16; One way ANOVA (p < 0.001). Fig. 5B. Penh values correlated with peripheral blood RSV-RNA loads in RSV infected mice on day 5 post-inoculation (p < 0.01; r = 0.7; n = 14). Correlations were computed using the Pearson's correlation coefficient.