Καλομενίδης Ιωάννης, Αναπληρωτής Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Ζακυνθινός Σπυρίδων, Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Κουλούρης Νικόλαος, Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Interstitial lung disease is an umbrella term for a heterogeneous group of more than 300 different chronic conditions that affect primarily and to varying degrees irreversibly the lung parenchyma and whose prognosis heavily depends on their aetiology and type.
Epidemiologically interstitial lung disease is divided in disease of known aetiology and in disease of unknown aetiology (idiopathic), the most common being the latter. Irrespective of individual category, idiopathic pulmonary fibrosis and sarcoidosis represent together more than 50% of all interstitial lung disease cases.
Disorders of any of the physiological mechanisms of exercise or abnormal coordination interaction between them will result in exercise limitation. The processes that involve the function of the lungs in exercise are limited by the negative effects of interstitial lung disease whose role is considered multifactorial due to respiratory, cardiovascular, muscular, and symptom limitations. The main background mechanisms are considered to be hypoxaemia due to the impaired level of gas exchange insufficient increase of alveolar ventilation relative to the oxygen requirements of exercise, ventilation/perfusion inequalities, low mixed venous PaO2, and diffusion impairment with total ventilation remaining inefficient compared to carbon dioxide production throughout incremental exercise. Parallely, lung fibrosis narrows and distorts the small and larger airways, decreasing laminar airflow and ventilation of gas exchange units while the vascular bed is progressively obliterated impairing alveolar perfusion leading to pulmonary hypertension and cor pulmonale and the protective hypoxic vasoconstriction in areas of lung fibrosis is incomplete. In general, the pathophysiology of the pulmonary circulation has been shown to be even more important than ventilatory mechanics in limiting exercise in patients with interstitial lung disease. Accumulating evidence demonstrates muscle weakness and fatigue to be a consequence of interstitial lung disease
Studies thus far have proven pulmonary rehabilitation to be effective in relieving dyspnoea and fatigue and improving patient quality of life with increased daily exercise capacity, while being a safe practice for the patients. It has proven most effective when encompassing both aerobic and resistance training, supplemented by educational lectures nutritional and psychosocial support.
Health gains for interstitial lung disease patients appear to be according to the studies similar to those gained from such practices in chronic obstructive pulmonary disease patients but smaller in magnitude. Long-term effects tend to be absent with patient's lung health improvements returning to baseline within 3-6 months suggesting programmes of longer duration then 3 months may be beneficial for more sustainable results with up to 12-30 months of sustained effects in programmes reaching 6-months of duration. Evidence also suggests that maintenance exercise programs may help sustain the attained benefits and that pulmonary rehabilitation can demonstratively decrease severity of symptoms of the disease such as dyspnoea and cough. Results differences should be considered based on specific populations differences.
A large randomised study demonstrated negative effects of early exercise rehabilitation after an exacerbation of chronic respiratory disease with no benefits gained and even a higher rate of mortality observed in the group, considered to be associated with greater degrees of hypoxaemia at rest and greater desaturation on exercise following an acute exacerbation incidence of the disease.
Short-term benefits of pulmonary rehabilitation have been observed in those with more severe functional impairment, while no specific cut-off point was observed at which rehabilitation could be considered ineffective. Additionally, evidence shows that early referral in the disease course may confer greater benefits for the patient overall.
The current recommendations for pulmonary rehabilitation vary across international guidelines and statements. In general, It has been proposed that repetitive stimulus of high ventilatory demands during exercise sessions proved the most beneficial. Furthermore, exercise training was shown to have more evidence suggesting health gains than the non-exercise training component. Pulmonary rehabilitation programmes are proven effective when similar to those commonly employed in chronic obstructive pulmonary disease but with modifications due to the frequent corticosteroid treatment received by Interstitial lung disease patients that limits muscle gains and considering the more fast deteriorating sysmptoms of interstitial compared to obstructive lung disease.
The best balance studies suggest is whole body exercise, where endurance training is combined with resistance (strength) training with additional elements of flexibility training.
Evidence shoes that exercise is proven most effective when accompanied by the nest possible symptom control and other modalities such as oxygen supplementation as well as complication management such as of cardiac arrhythmias and pulmonary hypertension which are associated with interstitial lung disease.
In conclusion, consistent evidence of benefit from randomised controlled and other trials provides a rationale for including pulmonary rehabilitation as part of usual care for interstitial lung disease, despite some knowledge gaps when considering each individual type of disease. Pulmonary rehabilitation is supported by current guidelines, as a safe, feasible and worthwhile adjunct therapy.