Recently a patient was referred to the lab for the above test who presented with a cluster of disabling signs and symptoms who had previously contracted poliomyelitis. Post Polio Syndrome although rarely life threatening can result in under ventilation if the patient has untreated respiratory muscle weakness and aspiration pneumonia from a weakness in the muscles controlling swallowing.
Maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) are measurements that may aid in evaluating respiratory muscle weakness. Measurement of MIPS/MEPS are the most widely used test to assess muscle pressure as it has no adverse effects and is non invasive.
Healthy adults can generate a MIP of greater than -60cmH2O and MEP of greater than 80cmH2O (both pressures tend to be higher in males and decline with age). Pressures lower than these may indicate neuromuscular disease affecting the muscles of respiration. However, other disorders may reduce the pressures by placing the respiratory muscles at a mechanical disadvantage. For example, the pressures may be reduced if there is chest wall deformity. MIP may be reduced by hyperinflation/gas trapping which flattens the diaphragm and places the intercostal muscles at a disadvantage. MEP may also be reduced in severe lung diseases. A MEP of less than 40cmH2O leads to an ineffective cough.
Several studies have demonstrated that MIP and MEP may be very useful in the diagnosis and follow-up of pulmonary and cardiac disease. A reduction in MIP has been shown to be associated with a progressive clinical worsening in patients affected by myasthenia gravis or Guillain-Barré syndrome. In addition it has been suggested that an imbalance between the pressure generated by the inspiratory muscles and the MIP may lead to the development of hypercapnia in patients with COPD. Indeed both MIP and MEP have been shown to be useful in detecting the presence of iatrogenic myopathy, such as steroid-induced myopathy or in predicting post-operative pulmonary complications following coronary artery by-pass surgery.
MIP and MEP are useful in the assessment of respiratory failure. They are sometimes used to predict whether a patient can be weaned from a ventilator. They are occasionally helpful in the diagnosis of unexplained breathlessness in association with a low vital capacity.
However, their usefulness is limited by the wide range of normal values and the fact that the tests are very effort-dependent. MIP and MEP are hard to perform and require a highly motivated subject.
Maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) are measurements that may aid in evaluating respiratory muscle weakness. Measurement of MIPS/MEPS are the most widely used test to assess muscle pressure as it has no adverse effects and is non invasive.
Healthy adults can generate a MIP of greater than -60cmH2O and MEP of greater than 80cmH2O (both pressures tend to be higher in males and decline with age). Pressures lower than these may indicate neuromuscular disease affecting the muscles of respiration. However, other disorders may reduce the pressures by placing the respiratory muscles at a mechanical disadvantage. For example, the pressures may be reduced if there is chest wall deformity. MIP may be reduced by hyperinflation/gas trapping which flattens the diaphragm and places the intercostal muscles at a disadvantage. MEP may also be reduced in severe lung diseases. A MEP of less than 40cmH2O leads to an ineffective cough.
Several studies have demonstrated that MIP and MEP may be very useful in the diagnosis and follow-up of pulmonary and cardiac disease. A reduction in MIP has been shown to be associated with a progressive clinical worsening in patients affected by myasthenia gravis or Guillain-Barré syndrome. In addition it has been suggested that an imbalance between the pressure generated by the inspiratory muscles and the MIP may lead to the development of hypercapnia in patients with COPD. Indeed both MIP and MEP have been shown to be useful in detecting the presence of iatrogenic myopathy, such as steroid-induced myopathy or in predicting post-operative pulmonary complications following coronary artery by-pass surgery.
MIP and MEP are useful in the assessment of respiratory failure. They are sometimes used to predict whether a patient can be weaned from a ventilator. They are occasionally helpful in the diagnosis of unexplained breathlessness in association with a low vital capacity.
However, their usefulness is limited by the wide range of normal values and the fact that the tests are very effort-dependent. MIP and MEP are hard to perform and require a highly motivated subject.
Vanessa
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