Clinical management of chronic obstructive pulmonary disease patients with muscle dysfunction

Abstract

Muscle dysfunction is frequently observed in chronic obstructive pulmonary disease (COPD) patients, contributing to their exercise limitation and a worsening prognosis. The main factor leading to limb muscle dysfunction is deconditioning, whereas respiratory muscle dysfunction is mostly the result of pulmonary hyperinflation. However, both limb and respiratory muscles are also influenced by other negative factors, including smoking, systemic inflammation, nutritional abnormalities, exacerbations and some drugs. Limb muscle weakness is generally diagnosed through voluntary isometric maneuvers such as handgrip or quadriceps muscle contraction (dynamometry); while respiratory muscle loss of strength is usually recognized through a decrease in maximal static pressures measured at the mouth. Both types of measurements have validated reference values. Respiratory muscle strength can also be evaluated determining esophageal, gastric and transdiaphragmatic maximal pressures although there is a lack of widely accepted reference equations. Non-volitional maneuvers, obtained through electrical or magnetic stimulation, can be employed in patients unable to cooperate. Muscle endurance can also be assessed, generally using repeated submaximal maneuvers until exhaustion, but no validated reference values are available yet. The treatment of muscle dysfunction is multidimensional and includes improvement in lifestyle habits (smoking abstinence, healthy diet and a good level of physical activity, preferably outside), nutritional measures (diet supplements and occasionally, anabolic drugs), and different modalities of general and muscle training.

Nutritional status and muscle dysfunction in chronic respiratory diseases: stable phase versus acute exacerbations

“…Muscle dysfunction is defined by the loss of strength (i.e., the ability to develop a maximal effort) and/or endurance (i.e., the ability to maintain a submaximal effort through time) (10,11). This functional impairment can be relatively stable (this is known as 'muscle weakness') or temporary (denominated 'fatigue', which is reversible with rest) (10,11). Muscle dysfunction can involve peripheral (limb) as well as respiratory muscles, and can appear in acute or chronic respiratory diseases due to different causes.…”

“…The presence of limb muscle dysfunction can even limit normal walking, leading to a reduction of patient daily activities and social life, with a strong negative impact on prognosis, quality of life, and utilization of social and health resources (3,7,8,(15)(16)(17)(18). Respiratory muscle dysfunction in turn is associated with increased dyspnea (10,11,19), a worse ventilatory response to both exercise and exacerbations (19)(20)(21), and can even lead to severe respiratory failure, as well as weaning difficulties in patients submitted to mechanical ventilation (22,23).…”

“…This is the case for both limb (prevalence 20-30%) and respiratory muscles (prevalence 20-45%) (111)(112)(113)(114). While nutritional abnormalities and deconditioning play a key role in the impairment showed by the former group, respiratory muscle dysfunction is mainly the result of geometrical changes occurring in the thorax as a direct result of the lung disease (10,11).…”

“…It should be noted that diagnosis of nutritional deficiencies can be especially difficult in female patients, since they can show loss of muscle mass even though body weight remains relatively stable, showing significant discrepancies between BMI and FFMI (105). Other methods that can also be used to assess nutritional status are imaging techniques (computed tomography, magnetic resonance and ultrasounds), air displacement plethysmography (ADP), deuterium dilution, and isotopic techniques (7,11,179,180). Blood determinations of serum total proteins, albumin fraction, cholesterol and prothrombin time can also be useful to complete the assessment of nutritional status (7).…”

“…Functional evaluation of respiratory muscles can be addressed with different approaches from clinical semiology to instrumentalized techniques. On the one hand, muscle dysfunction can be suggested by the presence of different symptoms and signs such as a very high respiratory rate with small tidal volume, a relevant worsening of dyspnea when lying in supine, the use of accessory muscles for ventilation, thoraco-abdominal or upper-lower chest incoordination, and difficulties in effective coughing (11). Imaging techniques, such as conventional chest X-ray and ultrasounds, can also be useful to suggest the presence of respiratory muscle dysfunction (183,184).…”