Helium-oxygen flow-volume curves in detecting acute response to hair spray

The acute effect of hair spray on small airway function was studied in 11 healthy subjects by recording maximum expiratory flow-volume (MEFV) curves while the subjects were breathing first air (Ar) and then a 80% helium-20% oxygen mixture (He). The flow rate response of breathing He compared to Ar (delta MEF50) at 50% of the control forced vital capacity (FVC), and the point of identical flow on Ar and He MEFV curves, known as volume of isoflow (VisoV) were measured. Eight of 11 subjects reacted to the hair spray by demonstrating a decrease in the MEF50 and delta MEF50 although the difference was not significant. However, there was a significant increase in VisoV at 12,20 and 30 min post exposure. VisoV may be a sensitive index in detecting small airway dysfunction following acute exposure to hair spray.