C6. Specialist referral

Consider referral to specialist respiratory services if needed [evidence level III-2, strong recommendation]

Referral to a respiratory medicine specialist may be considered for the indications outlined in Box 6.

Box 6: Indication for referral to specialist respiratory outpatient services
Reason Purpose
Diagnostic uncertainty and exclusion of asthma Establish diagnosis and optimise treatment.

Check degree of reversibility of airflow Obstruction
Unusual symptoms such as haemoptysis Investigate cause including exclusion of Malignancy
Rapid decline in FEV1 Optimise management
Moderate or severe COPD Optimise management
Onset of cor pulmonale Confirm diagnosis and optimise treatment
Assessment of home oxygen therapy: ambulatory or long-term oxygen therapy Optimise management, measure blood gases and prescribe oxygen therapy
Assessing the need for pulmonary rehabilitation Optimise treatment and refer to specialist or community-based rehabilitation service
Bullous lung disease Confirm diagnosis and refer to medical or surgical units for bullectomy
COPD <40 years of age Establish diagnosis and exclude alpha1-antitrypsin deficiency
Assessment for lung transplantation or lung volume reduction surgery Identify criteria for referral to transplant Centres
Frequent chest infections Rule out co-existing bronchiectasis
Dysfunctional breathing Establish diagnosis and refer for pharmacological and non-pharmacological management

FEV1, forced expiratory volume in 1s; COPD, chronic obstructive pulmonary disease. Box adapted from British Thoracic Society Statement (British Thoracic Society 2008b).

C6.1 Complex lung function tests

Other measurements of lung function such as static lung volumes and diffusing capacity of lungs for carbon monoxide assist in the assessment of patients with more complex respiratory disorders. Measurements such as inspiratory capacity (IC), which indicate the degree of hyperinflation and relate to exercise tolerance (O’Donnell 2001) and mortality (Casanova 2005) and forced oscillometry, have not yet found clinical application.

C6.2 Exercise testing

Cardiopulmonary exercise tests may be useful to differentiate between breathlessness resulting from cardiac or respiratory disease and may help to identify other causes of exercise limitation (e.g., hyperventilation, musculoskeletal disorder). Exercise prescription and monitoring of outcomes from drug or rehabilitation therapies are additional uses for these tests. Walking tests (6-minute walking distance and shuttle tests) are also useful and can indicate whether exercise oxygen desaturation is occurring.

C6.3 Sleep studies

Specialist referral is recommended for patients with COPD suspected of having a coexistent sleep disorder or with hypercapnia or pulmonary hypertension in the absence of daytime hypoxaemia, right heart failure or polycythaemia. Continuous overnight oximetry (with appropriate sampling frequency and averaging time) may be used to assess a need for overnight domiciliary oxygen therapy and may be indicated in patients receiving long-term domiciliary oxygen therapy to assess whether hypoxaemia has been adequately corrected.

C6.4 Ventilation and perfusion scans

The ventilation and perfusion (V/Q) scan may be difficult to interpret in COPD patients because regional lung ventilation may be compromised leading to matched defects. If pulmonary emboli are suspected, a CT pulmonary angiogram may be more useful. Quantitative regional V/Q scans are helpful in assessing whether patients are suitable for lung resection and lung volume reduction surgery.

C6.5 Echocardiography

Echocardiography is useful if cor pulmonale is suspected, when breathlessness is out of proportion to the degree of respiratory impairment or when ischaemic heart disease, pulmonary embolus or left heart failure are suspected. Patients with COPD may have poor quality images on transthoracic examination and transoesophageal echocardiography may be frequently needed.

Patients with COPD are prone to other conditions associated with cigarette smoking, including accelerated cardiovascular, cerebrovascular and peripheral vascular disease, and oropharyngeal, laryngeal and lung carcinoma. Conversely, there is a high prevalence of COPD among patients with ischaemic heart disease, peripheral vascular disease and cerebrovascular disease and smoking-related carcinomas (National Heart Lung and Blood Institute 1998) [evidence level I]. These patients should be screened for symptoms of COPD, and spirometry should be performed.

C6.6 Computed tomography pulmonary angiogram

CT pulmonary angiograms are useful for investigating possible pulmonary embolism, especially when the chest x- ray is abnormal.

C6.7 Transcutaneous oxygen saturation

Oximeters typically have an accuracy of plus or minus 2%, which is satisfactory for routine clinical purposes. They are more useful for monitoring trends than in single measurements. If continuous overnight oximetry is required, standard oximeters are not appropriate (See section C5.3). Oximetry does not provide any information about carbon dioxide status and is inaccurate in the presence of poor peripheral circulation (e.g., cold extremities, cardiac failure) and when readings are consistently below SpO2 80%.

C6.8 Arterial blood gas measurement

Arterial blood gas analysis should be considered in all patients with severe disease, those being considered for domiciliary oxygen therapy (e.g., whose FEV1 is <40% predicted or <1 L, whose oxygen saturation as measured by pulse oximetry [SpO2] is <92%), those with pulmonary hypertension, and those with breathlessness out of proportion to their clinical status). Respiratory failure is defined as a PaO2<60mmHg (8kPa) or PaCO2 >50mmHg (6.7kPa). The latter is termed ‘ventilatory failure’ and is accompanied by either compensated (chronic) or uncompensated (acute) acidosis. Acute respiratory acidosis indicates a need for assisted ventilation.