The incidence of physician confirmed asthma is approximately 4-7% in children. An additional 5% of children suffer from infection-related bronchiolitis and obstructive bronchitis. Of all patient visits at pediatric emergency rooms, 1 out of 10 is due to breathing difficulties with a great proportion leading to hospitalization. Salbutamol is the most commonly used drug in the treatment in acute bronchial obstruction. A vast majority of children require a spacer device (valved holding chamber, VHC) for the delivery of the drug aerosol. There are several different types of VHC on the market, but no recommendations on the device selection have been published. Both in in vivo and in vitro studies significant differences between different spacer devices have been reported. The study compares two different VHCs in the treatment of acute breathing difficulties in children. The end-points in this randomized physician-blinded study are symptom relief, rate of hospitalization, symptom recurrence, treatment compliance, and adverse events. The study will be conducted in pediatric emergency rooms (ER) in three university hospitals in Finland and one private clinic that routinely treat this type of patients. The treatment is given according to national treatment guidelines and no blood samples are drawn for study purposes. Both of the VHCs used in this study have been approved for use in clinical practice.