Assessment For Lung Transplantation
Indications for lung transplantation
Lung transplantation is indicated for end-stage obstructive, septic, restrictive lung disease or pulmonary vascular disease. In broad terms, the presence of septic disease (e.g. cystic fibrosis) or pulmo- nary hypertension is an indication for bilateral lung transplantation; obstructive or restrictive disease may be treated by single or bilateral lung transplantation. Combined heart lung transplantation, popular in the 1990s, is now rarely performed, although may be indicated for some complex congenital heart diseases.
A decision to offer lung transplantation is based on physical status, quality of life and comorbidity.
Forced expiratory volume in one second (FEV1) is the amount of breath forcibly exhaled in 1 second. It is usually expressed as a proportion of the value predicted for age, sex and build. A reduced FEV1 signifies obstruction to air escaping.
Forced vital capacity (FVC) is the total amount of breath forcibly exhaled.
Diffusing capacity of the lung for carbon monoxide (DLCO), also called the carbon monoxide transfer factor. Carbon monoxide (CO) is avidly taken up by erythrocytes, and when inhaled, the difference between the inspired and expired partial pressure of CO reflects the ability of CO to diffuse across the alveoli, and thus reflects the alveolar surface area. It is reduced in pulmonary fibrosis.
BODE index: the body mass index, airflow obstruction, dysp- noea and exercise capacity index is a derived score that predicts mortality from chronic obstructive pulmonary disease (COPD).
Gastro-oesophageal reflux disease (GORD): severe reflux is associated with repeated aspiration and early onset obliterative bronchiolitis. Reflux is particularly common with cystic fibrosis. Patients undergo 24-hour oesophageal pH studies and barium swallow.
Bone density (DEXA) scan: osteoporosis is common in chronic respiratory disease, in part associated with chronic steroid therapy, and is associated with pathological fractures. Severe osteoporosis (T score <3.5) is a relative contraindication.
Body mass index: low BMI (<18 kg/m2) is associated with poor outcome; high BMI (>30 kg/m2) creates surgical difficulties.
Chronic obstructive pulmonary disease (COPD)
COPD is the most common indication for lung transplantation. Features that suggest lung transplantation may be appropriate are:
· FEV1 <20%; DLCO <20%
· resting hypoxia (PO2 <8 kPa) and hypercapnia (PCO2 >6 kPa)
· pulmonary hypertension (systolic PA pressure >40 mmHg on echo).
· right-sided heart failure due to chronic pulmonary hypertension
· BODE score >7.
Cystic fibrosis (CF)
CF is characterised by periods of relative good health in the face of lungs colonised by pathogens, punctuated by severe infectious exacerbations. Transplantation is indicated in those with poor lung function (FEV1 < 30%; FVC, 40%) or rapidly decreasing lung function and/or increasing frequency and severity of infective exacerbations. Other indications for transplantation include recurrent or refractory pneumothoraces and uncontrolled haemo- ptysis. Young female diabetics are at risk of early deterioration.
Patients with highly resistant organisms, particular those with Burkholderia cenocepacia or atypical mycobacteria (e.g. Mycobac- terium abscessus or M. kansasii) have poor outcomes and many centres will not accept them for transplantation.
CF is a systemic disease. Diabetes is very common, and must be well controlled. Most patients have a degree of hepatic insufficiency which, if severe, may warrant combined lung–liver transplant.
Idiopathic pulmonary fibrosis (IPF)
IPF has a poor prognosis for which there is no treatment. Patients with IPF have the highest rate of death on the waiting list so early referral and transplantation is required for a successful outcome. Patients with the following should be considered:
· >10% fall in FVC in 6 months;
· DLCO <35%;
· >15% fall in DLCO in 6 months;
· resting hypoxaemia (O2 saturations <88%) or desaturation during 6-minute walk.
Primary pulmonary hypertension
Primary pulmonary artery hypertension is associated with syncope, peripheral oedema, ascites, haemoptysis and chest pain. Patients with rapidly progressive disease, poor functional status (NYHA grade III/IV and low 6-minute walk test [<350 m]), in spite of maximal medical therapy should be considered.
Although right ventricular function is often very poor by the time of transplantation, it can improve back to normal. Combined heart and lung transplants are therefore no longer warranted.
Similar criteria as for cystic fibrosis.
Alpha-1 anti-trypsin deficiency
Similar criteria as for COPD.
Priority for transplantation
When donor lungs become available there is often a choice between transplanting a patient with COPD who is very handicapped by their disease, albeit in a stable condition with a low waiting list mortality, and someone who is relatively well with CF but who may deteriorate and die very quickly.
At present in the UK 25% of patients awaiting a lung transplant will die in the first year on the waiting list, and only 30% will have been transplanted.
Contraindications to transplantation
There are general and specific contraindications. The general ones are similar to those mentioned for other organ transplants.
Good cardiac function, and the absence of severe coronary artery disease is important. This is especially the case for recipients with COPD, many of whom will have been heavy smokers.
CF patients are often malnourished, and a BMI of less than 18 predicts less good outcome.