Inhaling medication into the lungs can be a very effective drug delivery route, but frequently isn't. To get the best performance from dry powder inhalers and aerosol MDIs, the patient should be prescribed a suitable device, and trained to use their device optimally. By simulating the resistance to air that is encountered when breathing in through each different type of inhaler, and measuring the inspiratory flow achieved, the Doctor or Nurse can train the patient to inhale faster or slower - to get the optimum from their device.