Respiratory medicine

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chapter 41 Respiratory medicine

INTRODUCTION AND OVERVIEW

The human respiratory system is complex and finely tuned. Fortunately, two factors are of enormous benefit to us. First, there is a large reserve of function, greater than many of us are ever going to call upon; and secondly, the respiratory system can tolerate quite a degree of insult before symptoms appear. The predominant symptoms of respiratory problems that present to GPs are breathlessness, cough, sputum, wheeze and chest pain.

Diagnosis is the important first step in medical practice, and the classic method of adequate history, appropriate physical examination, thinking about the clinical problem and then considering special investigations will clarify most situations.

IMPORTANT CONDITIONS

The four diagnoses that are most prominent and/or important in general practice are:

• asthma
• chronic obstructive pulmonary disease (COPD)
• lung cancer
• infections.

The Bettering the Evaluation And Care of Health (BEACH) data show the distribution of respiratory problems managed in general practice (Table 41.1).1

TABLE 41.1 Important respiratory conditions managed in general practice

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Infections of particular importance are best considered as:

• bacterial—community-acquired pneumonia
• viral—viral upper respiratory tract infection (URTI)
• other—including opportunistic infections (PCP) and tuberculosis (TB).

ASTHMA

BACKGROUND AND PREVALENCE

It is estimated that worldwide as many as 300 million people of all ages have currently diagnosed asthma. The prevalence of asthma in Australia is quite high, with one in six children (14–16%) and one in nine adults (10–12%) having the disease.2 There is variation between countries in the incidence of asthma (this is detailed in the document Global burden of asthma (see Resources list at the end of this chapter)).

The condition we call asthma involves a number of pathological processes including inflammation, smooth muscle spasm and increased airways secretions. In essence it is a chronic inflammatory disorder affecting the airways. Many types of cells play a role in this inflammatory process, including mast cells, eosinophils, T-lymphocytes, macrophages, neutrophils and epithelial cells. Individuals who experience asthma generally have a genetic susceptibility that can also be affected by lifestyle and environmental factors. Airway inflammation causes recurrent episodes of asthma associated with the symptoms of wheezing, shortness of breath, chest tightness, and also coughing, most commonly at night or in the early morning or in response to exercise. These episodes of wheezing and dyspnoea brought on by widespread airflow obstruction will reverse spontaneously or with treatment.2 In those disposed to airway hypersensitivity, the inflammation is usually triggered by environmental factors such as allergens, irritants and temperature change. Psychological and emotional factors can also trigger or aggravate episodes of asthma.

AETIOLOGY

Asthma manifests as a combination of atopy, bronchial hyper-reactivity and IgE- and non-IgE-mediated acute and chronic immune responses. Most authorities accept that it occurs as a result of the action of a variety of environmental stimuli on genetically predisposed people.3

PATHOLOGY

The description of asthma given above, based on the National Asthma Council of Australia’s definition, covers the pathology of asthma quite succinctly.

DIAGNOSTIC APPROACH

It is important that a careful clinical history is taken (see below). An examination is done (in order to assist in excluding other differential diagnoses) and objective lung function testing, preferably spirometry, is performed.

HISTORY

As asthma is most often an intermittent disease, the history is of symptoms that wax and wane—there are episodes of symptoms. The most sensitive symptom of uncontrolled or destabilising asthma is awakening during the night with asthma symptoms such as chest tightness, breathlessness and wheeze. If the patient (or witness) reports hearing a wheeze with expiration, this is very suggestive, but not diagnostic, of asthma. Other information that supports the diagnosis of asthma include:

• a personal history of previous recurrent episodes of asthma (or symptoms suggestive of asthma if the diagnosis has not yet been made)
• normal respiratory and functional performance in the intervals between episodes
• a personal history of atopic (especially flexoral) eczema
• a family history of asthma.

If there are clearly identifiable triggers that precipitate episodes of cough, breathlessness or wheeze, this is strongly suggestive of asthma. The more common asthma triggers are viral URTI, change in ambient air temperature, house dust mite and exercise.

EXAMINATION

Physical examination is, on most occasions, normal unless the patient is in the midst of an asthma attack (i.e. an episode of bronchospasm). In the past, the chronic untreated asthma sufferer sometimes had a deformed thoracic area with a barrel chest and spreading of the ribs, but this is now only seen, in developed countries, in historical textbooks of medicine.

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FIGURE 41.1 Airway affected by asthma (right); a healthy airway is shown on the left

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FIGURE 41.2 Mucus hypersecretion in asthma: A The airway lumen is plugged with mucus released from the submucosal gland via a gland duct; B (higher magnification) Mucus can be seen streaming from the luminal tips of the goblet cells into the lumen

INVESTIGATIONS

• In the consulting room—spirometry is the ‘gold standard’ for objective lung function testing.
• Away from the surgery—encouraging self-monitoring by the measurement of peak expiratory flow rate (PEFR) is worthwhile. This is particularly important where the history suggests occupational or hobby-associated asthma. PEFR is also an important way for some patients to self-monitor their asthma, so they know when control of their asthma is slipping.
• Pathology—if one is looking for an allergic cause of asthma, sometimes radioallergosorbent testing (RAST) or skin prick testing is useful in helping to identify specific triggers. However, careful history taking will often narrow the allergens to a manageable number so that specific investigations are not needed.
• Special tests—these are rarely needed unless one is attempting to exclude differential diagnoses that have not been excluded by clinical methods.

INTEGRATED MANAGEMENT

Prevention

The ‘hygiene hypothesis’4 is a theory, still being debated,5 that links an increased risk of atopic disease with reduced microbial exposure from a variety of sources during childhood. Epidemiological studies are providing increasingly strong evidence that protection from atopic disorders including asthma is afforded by early-life exposure to environmental microbes. For example, children who are raised on farms, who drink unpasteurised milk, have more older siblings or attend day care at an earlier age are protected to some extent against asthma. This may explain to some extent the ‘asthma epidemic that has been occurring, especially in developed nations, over the past several decades’.6

If the ‘hygiene hypothesis’ is correct, letting children ‘get down and dirty’ may become a preventive activity!

Respiratory hygiene and minimising spread of infection is important in preventing exacerbations. Ensure routine immunisation against Haemophilus influenzae, seasonal influenza and pertussis (whooping cough).

Active surveillance

If we look back to when there were no effective treatments for asthma, the consequences of providing no active intervention are well described. Although patients can sometimes learn to ride out mild asthma attacks using self-help techniques such as breathing exercises, thereby reducing the need for reliever medication, doing nothing for moderate to severe asthma, or not taking preventer medications where asthma episodes are frequent, would not be considered a valid option. A worst-case scenario is that it is life-threatening. This is especially so for those with a history of brittle asthma and severe attacks.

Self-help

Many self-help strategies or home remedies are suggested but robust evidence of their efficacy is often lacking. Self-help strategies or home remedies that have been subjected to scrutiny and are listed in the medical literature are described below.

Tobacco avoidance

Cease smoking and avoid exposure to other people’s smoke. Exposure to cigarette smoke can trigger asthma attacks, increase the frequency of asthma attacks, cause the need for higher doses of preventer and reliever medication, increase the need for asthma medication and reduce lung function. Children exposed to cigarette smoke are more likely to develop asthma and have more severe symptoms and more frequent attacks.

House dust mite control

The major allergen in house dust comes from mites. Although methods of reducing dust mite exposure, such as adequate ventilation, keeping a dust-free environment and having regular fresh bed linen, are intended to reduce asthma symptoms, these methods have not been as successful as expected.7

Ion generator

Although marketed for use in homes to reduce asthma by removing dust and smoke particles, and although some studies show that ion generators can alter airways function, ‘the few studies which have been conducted in the homes of people with asthma, demonstrate no significant benefit in improving lung function or symptoms’.8

Pets

Some people with asthma are allergic to their own and others’ pets. The solution for many is the removal of the pets, to reduce exposure to the allergens in their hair and skin, but other methods such as pet washing, sprays and air filtration units can help reduce the amount of allergen in the air and on the floor of the home. The evidence is not at present conclusive.9

Caffeine

Caffeine (a methylxanthine drug) is related to the theophyllines that used to be commonly prescribed for asthma. These have an effect on the airway musculature. Caffeine is commonly found in coffee, tea, cola drinks and cocoa, and it has been found that even small amounts of caffeine can improve lung function for up to 4 hours, but for some the amount required to improve symptoms may be offset by the other side effects of caffeine.10

Fish oil

Many people with asthma who change their diets to include more fish oil do not improve their asthma,11 but other evidence has suggested that others do. There has been some work published on taking fish oil supplements (rather than just increasing fish in the diet). In one study,12 some benefit was shown in people with predominately exercise-induced bronchospasm (EIB) but the authors have given the guarded advice that ‘fish oil supplementation may represent a potentially beneficial non-pharmacological intervention in asthmatic patients with EIB’.

Vitamin C, vitamin E and beta-carotenes

There is a great deal of research under way into whether specific dietary supplementation is of benefit in asthma. Consensus on the importance of eating enough fresh fruit is yet to emerge, but one review found that:

Longitudinal data support the hypothesis that fresh fruit consumption has a beneficial effect on the lung. Among children, consumption of fresh fruit, particularly fruit high in Vitamin C, has been related to a lower prevalence of asthma symptoms and higher lung function.13

The message is therefore that a healthy diet is far more likely to be beneficial in asthma than supplements, particularly in the presence of a poor diet.13

Tartrazine exclusion

Tartrazine is one of the most commonly used food and medication additives or colourants. The evidence that tartrazine makes asthma worse, or that avoiding it makes asthma patients better, is questionable.14

Pharmacological

The cornerstone of asthma management is the use of inhaled corticosteroids. The greatest challenge is in deciding when they are required and in what dose. The recommendation of the National Asthma Council Australia is summarised in Figure 41.3.2a

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FIGURE 41.3 Management of mild, moderate and severe persistent asthma. BDP-HFA: beclomethasone dipropionate; ICS: inhaled corticosteroid; LABA: long-acting beta-2 agonist; LTRA: leukotriene receptor antagonist

(from NACA 20062)

Surgical

There has been some very early work on destroying the muscle layer in the airways as a means of minimising asthma symptoms, but this is still experimental.

Breathing exercises

The way in which ‘breathing exercise’ or ‘re-training’ is understood varies depending on the form of the therapy, the therapist providing the therapy and the cultural background of the person having the therapy. Some of the earlier studies of breathing exercises were small or had methodological flaws, but more recent studies demonstrate a trend for improvement.15 Evidence on breathing exercises, including yoga-based breathing exercises16, in asthma suggests that they can provide objective and subjective benefit and can be useful in reducing the need for reliever and preventer use.17 The Buteyko method is also widely used in asthma. Evidence suggests that it provides subjective benefit, although results indicating whether it also provides objective benefit have been inconsistent. It is best to learn breathing exercises from health professionals trained in their use.

Complementary therapies

Dietary supplements

There has been much interest in whether specific dietary supplementation can influence the clinical course of asthma. Many entities and results have been examined but the authors of the studies are careful in making claims. One study showed that the lipid extract of New Zealand green-lipped mussel had a beneficial effect in patients with atopic asthma.18

Adolescents with a less nutritious diet, with a lower intake of antioxidants and anti-inflammatory micronutrients, have poorer pulmonary function and increased respiratory symptoms, especially among smokers. The likely explanation is that these nutrients promote respiratory health and lessen the effects of oxidative stress.19 Dietary supplementation or adequate intake of lycopene and foods rich in vitamin A may also be beneficial in asthma.20

Acupuncture

The evidence is not clear and consistent enough to make firm recommendations about the value of acupuncture in asthma.21 It may be that some forms of acupuncture are more beneficial than others, or that acupuncture is beneficial for some variants of asthma but not others.

Alexander Technique

The Alexander Technique is a form of movement-based physical therapy. It is commonly used to correct posture and bring the body into natural alignment, and also as an aid to relaxation and greater body awareness. Although there are some positive findings, a review of trials found that there was not enough evidence to show a benefit of the Alexander Technique in reducing the need to use medication for asthma.22

Herbal treatments

Evidence from 27 trials covering 21 different herbal treatments for both adults and children, and from both inpatient and outpatient settings, was inconclusive generally because of methodological limitations of the trials. Although further trials of high quality are needed to assess the use of herbal treatments in asthma, there is enough positive preliminary evidence to suggest that some of these compounds will prove to be of benefit.23

Homeopathy

Different types of homeopathy are used for asthma, such as classical homeopathy (tailored to an individual’s bodily and psychological constitution and their symptoms) or isopathy (e.g. using a dilution of an agent that causes an allergy, such as pollen). In the existing studies on homeopathy and asthma, the type of homeopathy used varies and study designs are sometimes poor. Consequently, there is no strong evidence that homeopathy is effective for asthma.24

Speleotherapy

Speleotherapy, or staying in an underground environment such as a cave or mine, is believed by some to be of benefit for people with asthma. If benefits are there, it is believed that they come from air quality, underground climate (cool and humid), air pressure or radiation. Evidence is more anecdotal than derived from high-quality randomised controlled trials.25

ONGOING REVIEW AND/OR MONITORING

Asthma is a chronic disease and, as such, is worthy of regular planned medical review. However, it is the experience of many clinicians that people with asthma tend to view their asthma as an intermittent disease and so take medications and seek treatment only when they are particularly troubled by symptoms.

IMPORTANT PITFALLS

Making an accurate diagnosis of asthma can be particularly difficult in the paediatric age group, when the history and response to empirical treatment are the only guides. In the older patient, it is important to differentiate asthma from COPD (see below) but, at the same time, to be aware that some people have a mixed picture. If there is significant reversibility on spirometry (post-bronchodilator FEV1 increases by 200 mL and 12%), treat as asthma.

PROGNOSIS

More children than adults manifest asthma and so the assumption is that, as a problem, asthma ‘weakens’ with age. It is probably better to accept the view of the National Asthma Council Australia that:2

education, together with self-monitoring, appropriate drug therapy, regular medical review and a written asthma action plan, reduces morbidity and mortality.

Most people with asthma lead normal lives and can participate competitively in sport.

PATIENT EDUCATION

There is a wealth of useful material available at the National Asthma Council Australia website (see Resources list).

CHRONIC OBSTRUCTIVE PULMONARY DISEASE

BACKGROUND AND PREVALENCE

Chronic obstructive pulmonary disease (COPD) is a major cause of disability, hospital admission and premature death. It is commonly associated with other diseases including heart disease, lung cancer, stroke, pneumonia and depression.26 In a community-based survey that included lung function testing, doctor-diagnosed chronic bronchitis or emphysema was reported by 4.3% of the population. When clinical diagnosis is combined with complex lung function testing and an FEV1/FVC of less than 75%, around 12% of the population have some evidence of emphysema.27 This figure will be considerably higher in countries where anti-smoking legislation and campaigns are less prominent.

Definition

According to the Australian and New Zealand guidelines on COPD,26 COPD is:

characterised by airway inflammation and airflow limitation that is not fully reversible. It is a progressive, disabling disease with serious complications and exacerbations that are major burdens for healthcare systems.

AETIOLOGY

COPD is really a group of diseases that are clustered together—the more common sub-types are emphysema, chronic bronchitis and fixed airflow obstruction due to asthma.

COPD is the end result of chronic insults to the lungs. 70% of COPD is related to cigarette smoking28 but it can result from any particulate matter insult (in low-income countries this is often the indoor burning of biomass for cooking and heating) or air pollution.

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