Validation of Structured Light Plethysmography

Measurements using the Structured Light Plethysmography method will be compared to those obtained by spirometry using a flow based pneumotachograph.

Spirometry is the gold standard for measuring lung function in both clinical support and research roles. Modern spirometers are high precision, reliable instruments enabling a large numbers of parameters relating to lung volumes and the rate of emptying the lungs during a forced expiration to be measured. The most common and accurate method to measure the patient's forced expiration is via pneumotachograph which measures the flow of air through a mouthpiece and integrates the signal to derive the volume expired.

Structured Light Plethysmography (SLP) system that measures changes of the chest and abdominal wall movement during breathing by modelling the thorax and abdominal surface defined by a projected structured light pattern which enables a grid of virtual parts to be formed, the movement of which is recorded by digital cameras. SLP provides non-contact assessment to provide lung function data utilising structured light technologies and enhanced imaging processing.

In this study direct comparison will be made of measurements recorded simultaneously using the two measuring devices in children and adults.

To examine repeatability of the agreement between tidal breathing parameters measured by two techniques, repeated measurements will be performed in each of a group of normal adult subjects. The investigators will also examine whether the agreement is affected by a change in tidal breathing parameters. To obtain a change in tidal breathing parameters, measurements will be recorded during resting spontaneous breathing and after a period of exercise to elevate Respiratory Rate.

Inclusion criteria

• For the patient group, any patient attending the outpatient department or the Lung Function Laboratory
• For the Healthy Normals group, any adult between 18 and 80 years with no current or previous respiratory condition.

Exclusion criteria

• A current cold or other viral infection
• chest surgery within 4 weeks
• Haemoptysis of unknown origin the (forced expiratory manoeuvre may aggravate the underlying condition)
• Pneumothorax
• Unstable respiratory or cardiovascular status (forced expiratory manoeuvre may worsen angina or cause changes in blood pressure) or recent myocardial infarction or pulmonary embolus
• Recent eye surgery
• Presence of an acute disease process that might interfere with test performance (e.g. Nausea, vomiting)