Study: NCT02437630

Intervention type: PROCEDURE
Intervention: Oesophageal balloon to measure intra-thoracic pressure
Description: An oesophageal balloon will be inserted via a nostril after instillation of local anaesthetic and swallowed until the tip is in the lower third of the oesophagus. This will allow the intrathoracic pressure to be monitored via a pressure sensor attached to the oesophageal balloon catheter and placed next to the subject. This will allow us to observe the changes in oesophageal pressure during quiet breathing under a variety of applied positive pressure conditions.

Intervention type: PROCEDURE
Intervention: Oesophageal balloon to measure intra-thoracic pressure
Description: An oesophageal balloon will be inserted via a nostril after instillation of local anaesthetic and swallowed until the tip is in the lower third of the oesophagus. This will allow the intrathoracic pressure to be monitored via a pressure sensor attached to the oesophageal balloon catheter and placed next to the subject. This will allow us to observe the changes in oesophageal pressure during quiet breathing under a variety of applied positive pressure conditions.

Intervention type: PROCEDURE
Intervention: Fibre-optic laryngoscopy
Description: A fibre-optic laryngoscope will be inserted through the opposite nostril to that used for the oesophageal balloon and placed with its tip abve the larynx where the laryngeal movement can be observed This will allow us to observe the changes in laryngeal aperture under a variety of applied positive pressure conditions.

Intervention type: PROCEDURE
Intervention: Fibre-optic laryngoscopy
Description: A fibre-optic laryngoscope will be inserted through the opposite nostril to that used for the oesophageal balloon and placed with its tip abve the larynx where the laryngeal movement can be observed This will allow us to observe the changes in laryngeal aperture under a variety of applied positive pressure conditions.

Intervention type: OTHER
Intervention: standard lung function tests
Description: These will be carried out in any subject who has not had lung function testing in the previous 6 weeks and will be carried out by a lung function physiologist from the institution in accordance with standard procedures for lung function testing

Intervention type: OTHER
Intervention: standard lung function tests
Description: These will be carried out in any subject who has not had lung function testing in the previous 6 weeks and will be carried out by a lung function physiologist from the institution in accordance with standard procedures for lung function testing

Intervention type: PROCEDURE
Intervention: face mask CPAP
Description: The subjects will wear a facemask with apertures for the oesophageal balloon and fibre-optic devices to cover the mouth and nose. airflow and volume will be recorded with a pneumotachograph and there will be tubing to connect to a positive pressure source (CPAP) to allow mouth pressures to be altered between 0-15cm H20.( 1cm H20 is the pressure produced by a column of water of 1centimetre in depth)

Intervention type: PROCEDURE
Intervention: face mask CPAP
Description: The subjects will wear a facemask with apertures for the oesophageal balloon and fibre-optic devices to cover the mouth and nose. airflow and volume will be recorded with a pneumotachograph and there will be tubing to connect to a positive pressure source (CPAP) to allow mouth pressures to be altered between 0-15cm H20.( 1cm H20 is the pressure produced by a column of water of 1centimetre in depth)

Intervention type: PROCEDURE
Intervention: variation of mouth pressure with CPAP
Description: Once the other procedures are completed the subject will have his mouth pressure varied via application of positive pressure via a commercial CPAP device as used for treatment of obstructive sleep apnoea. The pressure will be varied randomly between 0-15cm H2O (water)for periods of 5 minutes both sitting and lying. Oesophageal balloon recording of intra-thoracic pressure and laryngeal movement and mouth airflow and volume will be recorded simultaneously and at the end of each 5 minute period the subject will be requested to take as big a breath in as possible to allow measurement of functional residual capacity and inspiratory capacity. This will allow us to observe the effect of changing mouth pressure with CPAP on laryngeal aperture and oesophageal pressures and airflow.

Intervention type: PROCEDURE
Intervention: variation of mouth pressure with CPAP
Description: Once the other procedures are completed the subject will have his mouth pressure varied via application of positive pressure via a commercial CPAP device as used for treatment of obstructive sleep apnoea. The pressure will be varied randomly between 0-15cm H2O (water)for periods of 5 minutes both sitting and lying. Oesophageal balloon recording of intra-thoracic pressure and laryngeal movement and mouth airflow and volume will be recorded simultaneously and at the end of each 5 minute period the subject will be requested to take as big a breath in as possible to allow measurement of functional residual capacity and inspiratory capacity. This will allow us to observe the effect of changing mouth pressure with CPAP on laryngeal aperture and oesophageal pressures and airflow.

Intervention type: OTHER
Intervention: facemask pneumotachograph
Description: The facemask will incorporate a pneumotachograph to allow measurement of airflow and volumes throughout the respiratory cycle. This will allow us to observe the pattern of airflow with varying applied CPAP

Intervention type: OTHER
Intervention: facemask pneumotachograph
Description: The facemask will incorporate a pneumotachograph to allow measurement of airflow and volumes throughout the respiratory cycle. This will allow us to observe the pattern of airflow with varying applied CPAP