Clinical exam skills: Breathlessness

In the fourth part of our series, Ian Bickle, Fionnuala Crummy, and Barry Kelly guide you through another typical exam question

An 86 year old woman was admitted acutely short of breath. She had become progressively short of breath over the past five years, to the extent that she was virtually housebound. Her exercise tolerance at best was 100 metres walking on flat ground. Doctors also noted an irritating dry cough. She was a non-smoker and otherwise in good health. There was no family history of note. She was living alone at the time and received limited formal help with daily living activities.

On examination, she was in overt respiratory distress. The oxygen saturation while breathing room air was 81%. This increased to 96% after administration of oxygen via a face mask (fractional inspired oxygen (Fio₂) 0.28).

Her respiratory rate was 30 breaths per minute; her heart rate was 98 beats per minute and regular in nature; and her blood pressure was 142/78. The jugular venous pulse was raised 3 cm. She had peripheral oedema up to her mid-calf bilaterally. There was no finger clubbing, but she had fine inspiratory crepitations to the mid-zones bilaterally (fig1).

Questions

1. Describe the findings on the chest radiograph and any suitable further imaging investigations.

   The patient was initially treated with loop diuretics and fluid restriction. Laboratory investigations showed normal inflammatory markers. Her breathing returned to baseline over the subsequent two days, and the following further investigations were undertaken.

   Figure 2 shows pulmonary function tests.

   Fig 2 (38k image)
   
   

2. What do these pulmonary function tests show?
3. Interpret the findings on blood gas analysis.

   High resolution computed tomography imaging of the chest was done. Figure 3 shows sample images.
   
   

4. What does the high resolution computed tomography image of the chest show?
5. What is the chief abnormality on the echogram?
6. What is the definitive diagnosis and what treatment may be of prognostic importance?

Answers

1. The heart size is normal. Interstitial changes are present in the middle and lower zones of the lungs. You can see the heart borders and hemidiaphragms. Assuming that these changes are established, as the clinical history indicates, the appearances show interstitial lung disease. This is classically seen as reticulonodular shadowing, which is described as having the appearance of "lines and dots" on the radiograph. High resolution computed tomography is recommended for further evaluation. This technique uses thin image slices of 1 mm, with a 10 mm gap between slices. This helps in evaluating the lung tissue.
2. A severe restrictive defect is noticeable on pulmonary function testing. Both the forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV₁) are significantly reduced, to 42.5% and 50.8% of predicted volume, respectively (fig 2). This gives a FEV₁/FVC ratio of 132.6%. The overall picture is characteristic of a restrictive defect. In obstructive lung disease, the ratio would be reduced to a value of 70-75% or less. The flow volume loop (fig 2) shows this visually. Compare this to the picture of the normal pulmonary function test (fig 2). The shape is essentially the same, but the volume is much reduced. In conjunction with this, the diffusion capacity is severely reduced, seen as a corrected transfer factor of only 11.8% predicted. The diffusion of gases across the alveolar membrane is reduced due to disease at this level.
3. The arterial blood gas taken on room air indicates type 1 (hypoxic) respiratory failure. This is hypoxia in the presence of a normal or low partial pressure of carbon dioxide (Pco₂). In contrast, type 2 respiratory failure is defined as hypoxia in the presence of a raised Pco₂.
4. Subpleural interstitial changes are present in the middle and lower zones, in keeping with the appearances on the chest radiograph. These are maximal at the lung bases where there is marked reticulonodular disease (fig 4). Traction bronchiectasis is evident in these areas too. There are no pleural plaques to indicate asbestos related disease. The differential diagnosis is of fibrosing alveolitis, asbestos related lung disease, connective tissue diseases, such as rheumatoid arthritis and scleroderma, or treatment with the drug amiodarone.
5. The left side of the heart, including left ventricular function, is essentially normal despite a clinical presentation suggestive of pulmonary oedema. However, the right ventricle is moderately dilated, leading to functional tricuspid regurgitation. There is also a high estimated right ventricular pressure (although confirmation on cardiac catheterisation would be helpful), which implies right sided heart failure. The normal right ventricular systolic pressure range is 15-25 mm Hg.
6. The definitive diagnosis is one of longstanding pulmonary fibrosis leading to cor pulmonale (right sided heart failure secondary to disease of the respiratory system). In this patient, the lung disease may be idiopathic, although her previous occupation may be of some relevance.

Her initial presentation with pulmonary oedema in the context of chronic respiratory disease that was responsive to diuretics is further evidence of this underlying diagnosis

Treatment of cor pulmonale includes fluid restriction and diuretics. Treatment should also be directed towards the underlying lung disease if possible. It has been shown that people with evidence of right sided heart failure and lung disease who have a partical oxygen pressure (Po₂) of 8 kPa or less benefit from long term treatment with oxygen.¹ This is oxygen delivered through a concentrator for 16 hours a day and confers prognostic rather than therapeutic benefit.

Patients should be carefully assessed before being prescribed long term oxygen therapy. They should be non-smokers and ideally should have been clinically stable for six weeks before the recommendation for treatment is taken.

Ian Bickle, senior house officer, medical rotation
Email: clonvara@yahoo.co.uk

Fionnuala Crummy, specialist registrar, respiratory medicine

Barry Kelly, consultant radiologist, Royal Victoria Hospital, Belfast


studentBMJ 2004;12:437-480 December ISSN 0966-6494

1. Medical Research Working Party, Flenely DC. Long term domiciliary oxygen in chronic hypoxic cor pulmonale. Lancet 1981;1:681-6.