JRSM >
Volume 96, Number 5 >
Pp. 215-218
Addenbrooke's Palliative Care Team, Box 193, Hills Road, Cambridge CB2
2QQ;
1 St Nicholas Hospice, Bury St Edmunds IP33 2QY, UK
Correspondence to: Dr Sara Booth E-mail: sarabooth{at}addenbrookes.nhs.uk
 | INTRODUCTION |
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 TOP INTRODUCTION AETIOLOGY AND ASSESSMENT OF...PALLIATION OF BREATHLESSNESSTHE USE OF OXYGEN...REFERENCES |
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The neural pathways serving the sensation of breathlessness are poorly understood, but dyspnoea is not simply an abnormality of the heart and lungs; it is a multisystem disorder with many accompanying subtle neurohormonal abnormalities and alterations in skeletal and respiratory muscle structure and function. The higher centres responsible for thinking and feeling can strongly influence the severity of the symptom. The ‘nervous system is not hard-wired’:4 it is characterized by plasticity and, just as with pain, the experience of breathlessness is likely to be modified both by previous experience of the sensation and by pathways from different areas in the central nervous system. Patients with apparently similar disease can have breathlessness of widely different severity.
In this review we outline the causes of breathlessness in advanced cancer and the use of air and oxygen in management of the symptom.
| AETIOLOGY AND ASSESSMENT OF BREATHLESSNESS IN ADVANCED CANCER |
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The contributions of the higher centres can be modified to reduce breathlessness. People can learn relaxation and breathing techniques and consciously use them whenever they feel threatened by an episode of breathlessness. Anxiety is a potent trigger of dyspnoeic episodes in advanced cancer—a stigmatizing and still terrifying disease for many people.
The pathophysiology of dyspnoea in advanced cancer is manifold (Box 1). The mechanisms can be summarized as the direct effects of cancer in the thorax and respiratory tract, the systemic non-metastatic effects of the cancer, sequelae of cancer treatments and coexistent non-malignant disease. A patient with advanced malignancy will often have several of these, along with many psychological and social concerns triggering anxiety. The relative importance of each is not always clear in an individual, but the treatable cause must be identified.
Most studies of the causes of breathlessness are retrospective but from a prospective study of 100 ‘terminally ill’ patients Dudgeon and Lertzman6 concluded that severe respiratory muscle weakness contributed substantially to dyspnoea. Among the potentially treatable causes of breathlessness in this series were hypoxia (40%), anaemia (20%) and bronchospasm (52%). Patients had a ‘median of five different abnormalities that could have contributed to their shortness of breath.’ More work is needed to confirm these preliminary findings. As in all areas of medicine, accurate diagnosis of the causes of the symptom in the individual is the best guide to effective treatment. In someone who is at the very end of life and breathless at rest, advanced imaging techniques or even transfer to hospital for investigation may not be appropriate because the discomfort will outweigh possible benefits. The treatment can then be based only on history, examination and the choice of individual patients and their doctors.
| Box 1 Causes of breathlessness in advanced cancer Effect of cancer Large/small airways obstruction with tumour Lymphangitis carcinomatosa Lung/segmental collapse Pleural effusion Pericardial/cardiac infiltration Hepatomegaly Infection Rib/spinal metastasis Systemic non-metastatic disease Weakness/cachexia Anaemia Pain Paraneoplastic syndromes Pulmonary embolism Secondary to treatment Radiation pneumonitis/fibrosis Chemotherapy fibrosis Infection Coexistent disease COPD/asthma Heart failure/dysrhythmia Ischaemic heart disease Motor neuron disease
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The presence and severity of breathlessness can be assessed during history-taking or by more formal measurement such as visual analogue scales. It is important to distinguish breathlessness at rest from breathlessness during exercise. One method for doing this, validated in patients with advanced cancer is the shuttle-walking test.7 This is an externally paced exercise test during which the pace increases as the patient increases the distance walked. As it requires a 10 m clear corridor and a trained assessor, it is not a realistic option for every patient in most palliative care facilities. An additional benefit from an exercise test is greater confidence in the ability and capacity to walk, which increases motivation to take exercise. Families and healthcare professionals tend to encourage patients to rest, and their obvious alarm when the patient becomes breathless discourages further activity.7 The observation of a shuttle-walking test, performed by an experienced member of staff with the patient becoming comfortable again after exercise, can help relatives understand that breathlessness is not of itself harmful. The benefits of exercise are becoming clear from many areas of medicine, and the changes found in skeletal muscle of breathless patients resemble those in patients who are deconditioned. Appropriate exercise and activity should be encouraged, even in patients with advanced cancer.
| PALLIATION OF BREATHLESSNESS |
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| THE USE OF OXYGEN AND AIR |
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TOPINTRODUCTIONAETIOLOGY AND ASSESSMENT OF...PALLIATION OF BREATHLESSNESSTHE USE OF OXYGEN...REFERENCES |
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Oxygen
The following definitions are important when prescribing oxygen
therapy.9
Short-burst oxygen therapy (intermittent oxygen therapy) is the
intermittent use of oxygen for the relief of breathlessness, before exercise
or for recovery after exercise. Ambulatory oxygen therapy is the
provision of oxygen therapy during exercise and activities of daily living.
Ambulatory oxygen equipment is any oxygen equipment that can be
carried by a patient during the activities of daily living; usually it weighs
less than 4.5 kg.
There is little published evidence on use of oxygen for breathlessness in advanced cancer; most work has been done in patients with COPD and did not use quality of life or the severity of breathlessness as endpoints. In addition, many patients with COPD have a different pattern of breathlessness. They tend to experience a slow descent into breathlessness, and are older by the time they have severe disease. Over the years they become familiar with doctors, nurses, hospitals and oxygen equipment. Patients with cancer may experience a rapid onset of breathlessness from previous good health, at a young age. Some have the double fear that death is imminent and that they will die gasping for breath. In a different category are the patients with lung cancer who have lived with COPD for many years. In every case knowledge of the previous experience of the patient and the history of the onset of breathlessness is crucial to management of the symptom.
The recommendations here are based on reports from the Royal College of Physicians (Domiciliary Oxygen Therapy Services9) and a working group of the scientific committee of the Association of Palliative Medicine (Booth S, Wade R, Johnson M, Kite S, Swanwick M, Anderson H, unpublished). Long-term oxygen therapy—i.e. the provision of oxygen at home, to be used long term for at least 15 hours a day—will not be considered here. It is not prescribed primarily to relieve symptoms but to reduce morbidity and mortality in patients with COPD and chronic hypoxaemia (defined as PaO2 <7.3 Kpa, one-second forced expiratory volume <1.5 L, forced vital capacity <2 L and cor pulmonale with or without hypercapnia).
Breathlessness at rest
Patients with breathlessness at rest are very ill. In one study of 38
cancer patients who were breathless at
rest10 rather than
on minimal exertion, the median survival was only 19 days after entry into the
trial. Several studies have indicated that oxygen supplementation gives relief
in some patients whether or not they are
hypoxic.10,11,12,13
In these studies oxygen was used for only short periods (if specified, 15
minutes maximum). The mix of patients with and without hypoxaemia differed
between the studies, and this may have affected the findings and the
conclusions.
A point to note is that oxygen was not consistently beneficial, even in patients initially hypoxaemic on air or those who had previously reported benefit from oxygen. The use of air from a cylinder reduces breathlessness in some patients.
Some of the authors proposed that the reductions in breathlessness could be due to some other factor—the facial cooling produced by a stream of oxygen;10 or movement of the gases across nasal receptors.13 Relief of breathlessness was not necessarily related to the reversal of hypoxaemia.10,11
The RCP report9 says that domiciliary oxygen therapy can be prescribed for palliation of dyspnoea in pulmonary malignancy and other terminal disease. It does not specify hypoxaemia, because not all breathless patients are hypoxaemic and not all hypoxaemic patients benefit from oxygen therapy. Evidence of hypoxaemia on pulse oximetry may strengthen the case for use of oxygen but is not sufficient by itself. Before oxygen is prescribed, simple but formal tests must show clear evidence of benefit, because the treatment is not without adverse effects. Testing may simply entail the use of a visual analogue scale before and after a test dose, or a more formal blinded ‘n of 1’ study.12
Breathlessness on exertion
The shuttle-walking test and other standardized assessment exercise tests
are becoming routine in patients with COPD. The
recommendation9 is
that ambulatory oxygen therapy be prescribed if patients, breathing air, show
‘a fall in oxygen saturation of 4% or more below 90%, or [that] exercise
endurance is increased by 10% measured by walking distance or breathlessness
scores by breathing oxygen.’ In some patients there is no doubt that
ambulatory oxygen therapy increases the capacity for exercise and it may also
speed recovery from breathlessness after
exercise.9,14
Knower et
al.15 have
suggested that in certain patients—those with an oxygen saturation of
95% or less at rest—desaturation to below 90% is likely on walking and
that such patients will benefit from oxygen therapy. The results need
confirmation since they were derived from a retrospective study of case notes.
A simple therapeutic trial of oxygen is at present the best predictor.
Ambulatory oxygen therapy is indicated for patients who desaturate 4% or more
below 90% on exercise when breathing air and/or if there is an improvement of
10% in walking distance or breathlessness scores when breathing oxygen: this
can be diagnosed by formal exercise testing and oximetry. There is no medical
reason why formal exercise testing should not be done in people with advanced
cancer, though it seldom is. An alternative, since the focus of care is to
improve and maintain quality of life at home, is to ask patients to keep a
simple record of the frequency and severity of breathlessness at home over a
period of time at first without and then with oxygen therapy.
Careful selection is necessary to identify those people who will benefit from oxygen therapy. Clearly a few get useful palliation from both short-burst and ambulatory oxygen while a larger number do not. Those who do benefit from oxygen should receive it; those who do not should not be burdened with its disadvantages. Individualized care is paramount.
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