100% is the asthmatic's best. The yellow zone will typically be set to start at 80% of the asthmatic's best while the red zone will typically start at 60%. Variability of PEFR of greater than 20% should alert the asthmatic to a possible asthma attack.
This is usually a stock item - Please allow 1 to 3 working days delivery
In most cases, items in stock that are ordered before 12 noon are delivered on a next working day service.
If you need this item urgently please use the live chat or call us to enquire about our premium rate delivery service including same-day, timed and weekend deliveries. For more information about delivery, please visit our delivery information page here