Hypertonic saline is often used to induce a sputum specimen (in someone who is unable to provide a specimen the usual way) or when normal saline is ineffective at loosening sticky secretions. You must be acreful when using hypertonic saline as it can induce bronchospasm. Therefore good practice would be to perform pre and post hypertonic saline spirometry and supervise the patient whilst they are being given the nebuliser.