Many COPD patients develop weakness of their chest and diaphragm muscles that are used to inspire air, and this sometimes contributes to chronic shortness of breath, or an impaired capability to exercise or otherwise exert themselves. If this weakness is substantial, then the technique of Inspiratory Muscle Training ("IMT") may be beneficial.
Ideally, to know whether or not you might benefit from IMT, you should obtain a test from your doctor called the Maximum Inspiratory Pressure ("MIP") which measures the strength of your inspiration muscles. Patients with an MIP of less than 60 cm H2O pressure are most likely to benefit from Inspiratory Muscle Training. And as you will see later, knowing the MIP is very helpful in defining the work load of your exercise program. However, if you are not able to obtain the MIP test, and would like to experiment with the IMT technique, go ahead. It will do you no harm to try the technique.
Note this technique refers to the muscles of inspiration. Properly done, expiration is mainly passive, and if forced expiration is done as part of a breathing training program, that forced expiration is used in only briefly in emergency situations. Therefore, there is seldom a need to exercise strengthen the muscles of expiration, though indeed there are some advocates and devices for expiratory muscle training.
There are two general types of muscular training, namely strength training and endurance training. Strength training is characterized by the very muscular athlete lifting very heavy weights. Endurance training is characterized by the thin long distance runner able to run marathons. The strength trained athlete would certainly finish dead last in a marathon, and it is doubtful the skinny endurance athlete could lift even 1/4 the weight of the strength trained athlete. In COPD, Inspiratory Muscle Training one is training for endurance, not strength, though the inspiratory muscles will indeed become stronger in the course of training.
The goal of an exercise program therefore is to provide a sufficient level of muscular work to achieve proper endurance training, while at the same time not provide an excessive work load to induce strength training.
There are two general types of IMT trainers, namely the so-called "Alinear Resistors" (or "Pinhole Resistors") and "Threshold Resistors."
Alinear (Pinhole) Resistors are very simple adjustable pinhole devices where one inspires through a narrow opening to induce a work load. An example is the popular "Pflex" device sold by the Respironics Company. The problem with these devices is the patient's ability to "cheat" the system by lowering their inspiration work load by simply breathing slower, to lower the inspiratory resistance. This makes it very difficult to establish and maintain a consistent exercise program. As such, this type of device is not recommended for serious training.
Far better are the Threshold Resistors, for example the Threshold IMT device, also sold by Respironics. These devices generally have a spring loaded valve, requiring the patient to inspire hard enough to open the valve and permit inspiration against that force. This opening pressure may be adjusted, and therefore set to a desired load for the individual patient. The required force, i.e. the inspiratory work load, is therefore known, and constant, and can be tailored for the individual, and changing individual needs. Therefore, it becomes an important part of a definable exercise program.
How high should the inspiratory resistance be set? Well, if you know your Maximal Inspiratory Pressure, the training resistance should be set at about 30 to 40% of the MIP for training, and about 20 to 30% when you first begin IMT training. This would require that you have a resource such as a local pulmonary laboratory or pulmonary rehabilitation program that had the necessary pressure gauge.
Otherwise, the Threshold IMT device has a reasonably accurate built-in indicating pressure reference, and simply set the device to about 30 to 35 cm H2O, or comfortably less if initially you are very weak. And as your strength improves to the point you are exercising without much difficulty, then advance the pressure up to, but generally not more than 40 cm H2O.
How long and how often should you exercise? Some programs advocate IMT for 15 or 20 minutes or even longer periods of time, and several times a day. The problem with this is, IMT is somewhat stressful and unpleasant, and it is rather boring. I would suggest IMT lasting only five minutes (but never more than 10 minutes), and practiced twice daily (and never more than three times a day). This will take you somewhat longer to achieve IMT, but it is more tolerable and less boring, and chances are you will be more likely to stay with the program.
The Breathing Trainer can be used to advantage in your IMT exercise program. Set the Tidal Volume to about 1000 cc, the Respiration Rate to about 8 to 10 breaths per minute, and the Inspiration Time to about 35 to 40%. This will automatically set a desired prolonged Expiration Time to about 60 to 65%, to be sure you are getting the air our of your lungs and not developing Air Trapping and Dynamic Hyperinflation.
Now, you will have a known level of inspiration pressure (i.e. work load), a known breathing pattern, and a known total time of exercise (i.e. 5 minutes). By changing the exercise time and the inspiratory work load, it is now possible to define an exercise program, and to set training goals and evaluate progress.
For those of you who have an Alinear "Pinhole" Resistor, e.g. the Pflex device, use of the Breathing Trainer to time your breathing will now permit a constant and reliable inspiratory air flow, and therefore a steady and reliable work load. In other words, the Breathing Trainer will elimit the "cheating" factor, and make these simple and more economical devices into a reliable inspiratory exerciser.Your work load can then be increased as your strength improves by selecting a smaller pinhole opening, while maintaining the same Breathing Trainer prompting.
Initially, you may not be able to exercise for a full five minutes without excessive fatigue. You should feel tired, but not too tired. If too tired, note the time you had to stop, and on you next exercise sessions for the next few days, work for 1/2 a minute less than your fatigue time. After about five days you should be feeling more comfortable with this level of stress, and if so, then try exercising 1/2 a minute longer for a few days. In this manner, gradually work your way up to a full five minute session.
When you are comfortable with that full five minute session, then increase your work load by about 5 cm H2O, and start again to build up to a comfortable five minute exercise time. Note, if initially your muscles are very weak, you may lower your inspiratory load about 10 to 20 cm H2O, as well as reducing your work time to only a minute or so. In this case, also gradually increase your work load as well as your exercise time as your strength and exercise fatigue improves.
When should you stop your IMT program? Ideally, you should again have your Maximum Inspiratory Pressure measured. If you are able to achieve a MIP of 80 to 90 cm H2O pressure you have probably achieved your therapeutic goal and will no longer benefit from further IMT. Otherwise, if you can exercise for about ten minutes with an inspiratory work load of 40 cm H2O you will probably have reached your training goal.