Investigations RSV can be identified rapidly using a fluorescent antibody test on nasopharyngeal secretions. The chest X-ray shows hyperinflation of the lungs due to small airways obstruction and air trapping. Blood gas analysis, which is required in only the most severe cases shows lowered arterial oxygen and raised co2 tensionInvestigations ◼ RSV can be identified rapidly using a fluorescent antibody test on nasopharyngeal secretions. The chest X-ray shows hyperinflation of the lungs due to small airways obstruction and air trapping. Blood gas analysis, which is required in only the most severe cases, shows lowered arterial oxygen and raised CO2 tension