Inspiratory muscle training

Inspiratory Muscle Training or Respiratory Muscle Training or Ventilatory Muscle Training. IMT is the physiotherapy technique, with the help of different breathing exercises.

1. Inspiratory Muscle Training Dr. T.SUNIL KUMAR

2. Inspiratory muscle training (IMT) is indicated for patients who exhibit signs and symptoms of decreased strength or endurance of the diaphragm and intercostal muscles. Signs and symptoms include, but are not limited to, decreased chest expansion, decreased breath sounds, shortness of breath, uncoordinated breathing patterns, bradypnea , and decreased tidal volumes.

3. Patients with respiratory muscle weakness or fatigue may have such diagnoses as COPD, acute spinal cord injury, Guillain – Barré syndrome , amyotrophic lateral sclerosis, poliomyelitis, multiple sclerosis, muscular dystrophy , myasthenia gravis, or ankylosing spondylitis. In addition, IMT may be indicated for patients on mechanical ventilation to improve weaning from ventilation.

4. The goal of IMT is to increase the ventilatory capacity and decrease dyspnea . An IMT program has two parts : strengthening and endurance training. Each part will have increased or decreased priority according to the needs and medical condition of the patient . Concepts of ventilatory muscle training are the same as those for other skeletal muscle training, incorporating the concepts of overload, specificity, and reversibility.

5. The overload principle applied to endurance muscle training requires low load imposed over longer periods. Specificity refers to training the muscles for the function they are to perform , for example, resistance applied to inspiratory versus expiratory muscles. Training effects may be lost over time if training is discontinued.

6. The first step in any program is to teach the patient (if alert and oriented) the correct way to use the inspiratory muscles to ensure efficient inhalation. Including family members and support system members in the teaching can reinforce the program.

7. Weakness of a muscle is the inability to generate force against resistance. The length of the muscle affects the force output, as demonstrated in the length–tension curve. In the respiratory system, the strength of the diaphragm and other inspiratory muscles is measured as a function of standard pressure–volume curves. Weakness of the diaphragm will decrease the negative inspiratory pressure generated by the patient, and thereby decrease the volume of air inhaled.

8. Patients with COPD have hyperinflated lungs and a flattening of the diaphragm, which alters the length–tension relationship of this muscle . Fatigue of the inspiratory muscles, particularly of the diaphragm, will result in failure to meet the demand for adequate alveolar ventilation. Hypoventilation will decrease the arterial partial pressure of oxygen (PaO2) and increase the arterial partial pressure of carbon dioxide (PaCO2), and can lead to acute respiratory failure.

9. The diaphragm is made up of all three types of muscle fibers , including slow-twitch oxidative (SO), fast-twitch oxidative glycolytic (FOG), and fast-twitch glycolytic (FG ). The adult diaphragm is approximately 55% slow-twitch fibers , compared with about 10% in the infant. Fatigue is related to the ‘SO’ fibers , whereas weakness is attributed to thE FG fibers .

10. When initiating physical therapy treatment, the therapist should realize that all fibers need to be addressed in the cardiopulmonary treatment program. While mechanically supported on a ventilator, the diaphragm can lose 5% of its strength per day. When the patient begins the weaning process, the inspiratory muscles will gain endurance while performing inhalations without the assistance of the ventilator.

11. Endurance training of the diaphragm will increase capillary density, myoglobin content, mitochondrial enzymes, and the concentration of glycogen. Overall , it will increase the proportion of fatigue-resistant slow-twitch fibers . The recommendations include two to three daily sessions of 30 to 60 minutes of deep breathing, concentrating on using a diaphragmatic breathing pattern.

12. An early-stage IMT technique is sniffing. Sniffing naturally enlists the diaphragm. With the patient in a comfortable position such as side-lying or reclined, the therapist may assist the patient in placing both hands on the abdominal area to provide proprioceptive feedback. Then , in a relaxed tone of voice, the therapist instructs the patient to sniff quickly through the nose three times with slow, relaxed exhalations.

13. The Therapist gives feedback throughout this technique on the quality of sniffing, assessing whether the patient is showing a diaphragmatic breathing pattern . If the patient is able to perform this effectively, the progression of this technique is to reduce the number of sniffs from three down to one at an increasingly slower pace. The goal of this technique is to increase the awareness of correct use of the diaphragm.

14. The technique progression continues until the patient shows the diaphragmatic breathing pattern at a normal rate and depth for all levels of functioning. According to Massery and Frownfelter , there is an 80 % success rate, with patients affected by primary pulmonary pathologies or neurologic impairments

15. Strength training can be performed in a number of different ways, depending on the initial strength of the diaphragm. One method that can be utilized easily for the patient achieving tidal volumes of 500 mL or better is resisted inhalation. This can be performed manually by the therapist. The therapist has the patient assume a comfortable position as described earlier to promote diaphragmatic excursion.

16. The therapist gently places the hands just below the rib cage on both sides of the patient’s thorax. Before the patient initiates an inspiration, the therapist gives a small amount of resistance to the diaphragm by pushing gently up and in, and continues this pressure through the inspiratory phase. No resistance is given during exhalation.

17. The therapist may also use weights for diaphragmatic strengthening. To evaluate if this is an appropriate method, the therapist first observes to determine whether normal diaphragmatic excursion occurs at rest and then with the addition of weights. The patient should be able to breathe comfortably and without accessory muscles for 15 minutes; if the amount of weight is excessive, the pattern of inspiration will become uncoordinated.

18. Several authors suggest that strength training in this manner should include two or three sets of 10 repetitions once or twice a day. However , with either the manual or the weights method, the quality of the contraction needs to be monitored. The patient should not be “pushing” with the abdominal muscles against the resistance, which enhances the exhalation phase of breathing rather than the muscles of inspiration.

19. For a patient with “fair or reduced” diaphragmatic strength (tidal volume less than 500 mL), active breathing exercises are indicated without resistance. A patient with poor strength will find it difficult to exercise with the head of the bed elevated; a supine position will prevent the abdominal contents from pushing up on the diaphragm and limiting its excursion.

20. Another form of resistive training utilizes specific handheld training devices, such as the P-flex, DHD device, Threshold, or the Peace Pipe. The resistance is increased by decreasing the radius of the device’s airway. The patient inhales through the device at a level that does not cause adverse effects, such as dyspnea or a drop in oxygen saturation, for a 15- to 30-minute session twice per day. When this level is comfortable for the patient , then the resistance is gradually increased.

21. Much controversy has surfaced regarding the efficacy of IMT since its introduction into clinical practice. Evidence has been presented both supporting and dismissing IMT as a reliable treatment method. The major discrepancy may exist in the diagnosis for which this treatment is prescribed. A patient with insult to the lung tissue itself—for example, COPD or ARDS—may not tolerate IMT.

22. Inspiratory muscle training, which is a strengthening exercise, would increase the demand for oxygen delivery in the diseased lungs . However , a patient with a neuromuscular disease and intact lungs may be more likely to tolerate the increased oxygen demand and derive a benefit, as would the patient on mechanical ventilation who is trying to be weaned from the ventilator.

23. Deep breathing exercises are indicated for the patient with atelectasis, which is caused by hypoventilation and the collapse of alveoli in the lungs. The use of an incentive spirometer is an effective way to practice diaphragmatic breathing, prevent or reverse atelectasis , and stimulate a cough. Often, it is given to the patient preoperatively so he or she can practice deep breathing.

24. Then, after surgery, the patient may be able to perform this technique from memory as the effects of anesthesia start to diminish . The patient is instructed to perform deep breathing exercises with the incentive spirometer 10 times every hour to replenish surfactant, which is lost in the presence of atelectasis. The patient needs to be instructed to perform a slow, relaxed breath through the mouthpiece.

25. It is often helpful to have the patient place a hand on the abdominal area to feel the diaphragm working in the correct way. If the patient is having a difficult time performing this technique, the therapist may place a hand over the patient’s hand to facilitate the proper technique. Then the therapist should instruct the patient to perform the breathing slowly, with the abdomen rising out during inspiration.

26. The goal is for the patient to be able to use the incentive spirometer independently without proprioceptive or verbal feedback. Alternatively , early mobilization has been shown to be as effective as deep breathing exercises after gallbladder and cardiac bypass surgery

27. Endurance training of the extremities is another technique that has been explored in an effort to increase ventilatory muscle endurance. studies ON pediatric patients with cystic fibrosis and found that upper extremity endurance training did increase the endurance of the ventilatory muscles . SOME STUDIES examined the effects of upper and lower extremity training on ventilatory muscle endurance with adult patients with COPD and found no correlation.

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