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.
Assessment investigations
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.
Disease-specific considerations
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.
Bronchiectasis
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.
