LCI Spine: Assessing Pulmonary Function in Early Onset Scoliosis Using Lung Clearance Index: 

Summary:

Early Onset Scoliosis (EOS) is scoliosis occurring under the age of 10 years. EOS can be fatal via respiratory failure. We aim to describe the pulmonary function in children with EOS using a new technology. We will compare this to normative data in a disease free population.

 Whilst a considerable amount is known about the effects of scoliosis in the adolescent population, little is known in the younger population. Children aged under 8 find it difficult to comply with traditional pulmonary function assessments and sleep studies represent a poor surrogate. We will be the first to describe.

Lung Clearance Index (LCI) is derived from tracing the washout of an inert gas from the lungs during normal (“tidal”) breathing. It is a measure of ventilation inhomogeneity that reflects early disease in the small airways. LCI has been shown to be more sensitive and more responsive to change than standard spirometry in children and adults with lung disease. LCI is also very reproducible, and easy to perform since only relaxed tidal breathing is required. There is a narrow range of normal that does not change with age.This makes it particularly suitable for longitudinal studies since (unlike spirometry) any deviation in LCI can be confidently ascribed to changes in lung function rather than growth. Early disturbance of lung function, detectable by LCI, has been shown to predict later lung function decline.

Fifty children with a diagnosis of EOS will be recruited from ROH and BCH. They will be excluded if they have been previously diagnosed with asthma or significant non-scoliosis related respiratory problems. When possible, LCI will be measured each time they attend the Out-Patient Department. A minimum of 3 observations will be made over the 2 year study period for each subject.

Recruited children will perform washout assessments whilst comfortably seated and suitably distracted. Once relaxed tidal breathing is established, the wash-in phase is commenced by switching the child to breathing the tracer gas mixture. Wash-in is complete when the inspired and expired concentrations are equilibrated (equal). Using the rebreathe system this takes around 30 seconds in healthy children, and is predicted to be 1-2 minutes in children with respiratory disease. Once this equilibrium is reached, the wash-out phase is commenced automatically by switching the child to breathing room air. They continue gentle tidal breathing until the tracer gas has been washed out to 1/40th of the starting concentration. This process is repeated 3 times.

Additionally where children are able to comply with traditional spirometry measures, assessments will be made and therefore a degree of cross validation will be possible (primarily in the elder children-aged 8 and above)

Through similar studies in different populations (including disease free) a range of normative and disease specific LCI data exists. We will compare EOS patients to a cohort match and describe over the 2 year period both the absolute difference vs "normal" subject and also the natural history of the disease.

Multiple subgroup analyses will be possible including: the affect of surgery, the affect of curve magnitude, location of curve apex. There are a remarkable number of avenues which can be subsequently explored.

Through this work we aim to lay the foundations of a longer term natural history study in this important disease. There are critical questions that need to be answered, particularly around the benefits of particular surgical interventions in this disease group. Controversy remains as to whether surgical intervention truly improves pulmonary function as historically we have been unable to assess these young children. We are presented with a unique opportunity to study this serious disease and progress understanding about disease stratification and planning of interventions.

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