There are two main types of inhalers generally used to deliver inhaled medication to the lungs:

• Metered-dose inhalers. By pushing down on a small, pressurized canister, a metered amount of aerosolized medication is released from the inhaler through the use of chemical propellant, usually chlorofluorocarbon (CFCs). This process converts the medication into a fine mist that can be inhaled deep into the lungs.
  
  

  

  When the canister is depressed, a puff of medication is released into the mouth of the user. Once in the mouth, the user can inhale the mist into the lungs, allowing the medication to come into direct contact with the inner lining of the lungs, where symptoms associated with asthma and COPD frequently appear.
  
  This type of inhaler usually includes between 50 and 200 individual doses. To properly use a metered–dose inhaler, the timing of the “push” needs to coincide with the proper inhalation. This takes some practice, but it is important to use these inhalers correctly. With an incorrect breathing technique, the medication will be blocked by the tongue or back of the throat and will be unable to penetrate into the lungs.
  
  Some of these types of inhalers are breath activated, so that the medication is automatically released as the patient draws a deep breath.
  
  The CFC propellant used by these inhalers is harmful to the ozone layer. As a result, they are being phased out in favor of metered-dose inhalers with hydrofluoroalkane (HFA), an ozone-friendly propellant. HFA may have a different taste and smell. However, the size, shape and effectiveness of the inhaler are the same.
  
  
• Dry powder inhalers. This type of inhaler does not use a chemical propellant to release the medication. Instead, it relies on the force of the patient’s rapid intake of breath. As the patient inhales, a measured dose of small granules of medication is pulled into the lungs.
  
  Because there is no need for coordination between the hand and the lungs, dry powder inhalers are generally considered easier to use than metered-dose inhalers. Still, some types of dry powder inhalers require a large amount of effort to inhale the medicine. For this reason, these inhalers may not be usable by children or the elderly. There are several types of dry powder inhalers:
  
  
• • Turbohaler. Uses a rotated knob to dispense each dose.
    
    
  • Diskhaler. Uses a raised lid to dispense each dose from replaceable disks.
    
    
  • Rotahaler. Uses a rotated sleeve to dispense each dose through a mesh screen.
    
    
  • Spinhaler. Uses a sliding sleeve and a small propeller to deliver each dose.
    
    
  • Diskus. Uses a lever to deliver each dose.

Sometimes a device called a spacer is used with a metered-dose inhaler. A spacer is a holding chamber that is added to the mouthpiece of the inhaler to increase its effectiveness. When the inhaler is activated, the spacer allows the puff of medication to turn into a very fine mist before the individual inhales. The finer the mist, the deeper the medication can be inhaled into the lungs. A spacer also prevents the medication from being blocked by the tongue or back of the throat, which can happen when a metered-dose inhaler is used alone. Spacers cannot be used with dry powder inhalers.