The secret of longevity is to keep breathing. Sophie Tucker
Lung disease encompasses a large collection of widely varying chest pathologies. The most frequent include chronic obstructive pulmonary disease (COPD – what used to be referred to as chronic bronchitis and/or emphysema), asthma and pulmonary fibrosis. They share the feature of causing more than usual breathlessness at levels of exertion which would normally be tolerated well.
There is no lung disease which is caused by lack of exercise (except when this has resulted in obesity) but any loss of lung function has effects which can be helped by being active and physically fit. When lung function is impaired the supply of oxygen from the lungs to the blood is compromised.
Lung function is not normally a limiting factor in exercise tolerance. The oxygen saturation of arterial blood is still high at maximal exercise. This is not true of exercise for patients with lung disease. As they increase the intensity or duration of exercise the oxygen saturation of their blood falls progressively until breathlessness stops further effort.
Exercise, increased fitness and lung disease
Aerobic exercise for people with lung disease increases “cardio-respiratory” fitness but through different mechanisms to those with normal lung function. The limitation of exercise tolerance in pulmonary patients is provided by falling levels of blood oxygen level rather than reaching maximum cardiac output. Physical training increases their exercise tolerance by improving the efficiency of blood distribution to the working muscles and their ability to take up oxygen from their blood supply. Physical training also improves the efficiency and strength of the muscles of respiration – the diaphragm and rib muscles. Improvement in cardiac function is less important than in those with normal lung function.
Patients with chronic lung disease inevitably have low levels of physical fitness, a consequence of their limited exercise tolerance and ability to exercise. Pulmonary rehabilitation (PR) aims to reverse this loss of fitness using a programme of graduated exercise within the limits of the patients’ breathlessness. It is now provided by most hospital trusts in the UK and is recommended by NICE as part of the routine care for COPD patients.
A Cochrane systematic review of PR included 64 controlled trials with 3822 participants. The conclusions were that “pulmonary rehabilitation relieves breathlessness and fatigue, improves emotional function and enhances the sense of control that individuals have over their condition. These improvements are moderately large and clinically significant. Rehabilitation serves as an important component of the management of COPD and is beneficial in improving health‐related quality of life and exercise capacity.” The report found that hospital based programmes were more effective than community based programmes but that the complexity of the intervention made no difference – it was just the exercise which did the business. Other benefits which have been shown include increased walking distance and improved quality of life.
The timing of the initiation of PR is important. The sooner it can be started after a hospital admission the better. In one study, when PR was started within 90 days of discharge the one year mortality was 7%, compared with 20% for those not given PR or started after the 90 day period.
Regular exercise also improves the lot of asthma patients. The main feature of asthma is narrowing of the airways leading to wheezing when breathing out. For some asthma patients, exercise, particularly in cold weather, worsens both wheezing and breathlessness. However exercise training does benefit asthma patients and the more exercise they take the more effective it is up to a high level. At very high levels (>10 hours training per week) the benefit is lost. Body weight is also an important factor in asthma – the higher the BMI, the worse the control of asthma symptoms.
Long-term exercise habit and death from lung disease
The evidence is strong that long-term exercise reduces the ill effects of lung disease. A US study of 480,000 adults followed up for 8.5 years identified 3,188 deaths. Among those who met national recommendations for muscle strengthening exercise, the mortality was 65% of those who did no exercise. For those who took regular aerobic exercise the figure was 34% and for those who did both it was an astonishing 21%.
Respiratory infections including Covid
Physical fitness is no protection against catching lung infections. However the fitter you are the less the impact of such infections and the quicker the recovery. This has been particularly important during the pandemic. The deaths have been in the least physically fit, be that a consequence of age, obesity or the myriad of diseases associated with lack of exercise (diabetes, heart disease etc).. This has led to the idea of “prehabilitation” for our more vulnerable citizens. That is exercise training to improve physical fitness, reduce weight and lessen the impact of all the diseases of later life. Prehabilitation is used to prepare patients for major surgery and works by giving the individual greater reserves of resilience. Regular exercise also improves the immune response to virus and other infections, providing further protection against complications of Covid and other nasties.
The message should not be “Don’t kill Granny” but “Send Granny to the gym!”.