The Influence of Posture on Airway Diameter, Resistance and Airflow Distribution in Healthy Subjects
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|ClinicalTrials.gov Identifier: NCT01893697|
Recruitment Status : Completed
First Posted : July 9, 2013
Last Update Posted : May 28, 2015
|Condition or disease||Intervention/treatment|
|Healthy Participants||Other: HRCT scan in a specific postural position|
Many respiratory diseases require a physiotherapeutic treatment that focusses on clearance of excessive mucus from the airways.
The underlying physiological hypothesis why those mucus clearance techniques are effective is based on the development of an optimal expiratory airflow velocity that applies shearing forces on the mucus at the inner surface of the airway. These shearing forces eventually lead to displacement of mucus to the central airways were it could be evacuated.To accomplish optimal velocity with the same expiratory airflow, it is necessary to decrease the airway diameter and hence increase in the airflow velocity. In other words, the airway diameter and resistance are important factors to take into account in mucus clearance techniques.
In many mucus clearance techniques, postural position is used to facilitate this clearance. Clinical trials in patients with chronic obstructive pulmonary disease (COPD) and cystic fibrosis where they combined clearance techniques with different postural positions showed to be effective.
The influence of posture has been evaluated in the lateral decubitus position and resulted in a greater clearance of mucus in the depended lung. The authors suggested that this may be due to a better deflation of the depended lung that is favored by 3 forces: gravity, mediastinum weight and pressure of abdominal viscera on the infra lateral lung. Deflation of this lung leads not only to a decrease in lung volume, but also results in a decrease in airway diameter. Nevertheless, it is not known to what extend this decrease in diameter occurs in a lateral position. Furthermore, an optimal expiratory flow must be retained in the underlying lung at lower lung volumes. These regional changes in the underlying lung cannot be measured by for example classic lung function tests since these test are not sensitive enough. Indeed, Washko et. al. found no significant changes of overall residual volume (RV), total lung capacity (TLC) and vital capacity (VC) between the different positions in healthy subject.
However, Functional respiratory imaging (FRI) is able to assess the regional changes in healthy subjects. This 3D imaging technique in combination with computational fluid dynamics (CFD) is accurate in calculating regional changes such as airway diameter, volume and resistance. In addition, repetitive FRI measures are able to assess lobar expansion, which is an indirect measure of airflow distribution in a specific part of the lung.
|Study Type :||Observational|
|Actual Enrollment :||5 participants|
|Official Title:||The Influence of Posture on Airway Diameter, Resistance and Airflow Distribution in Healthy Subjects|
|Study Start Date :||April 2013|
|Actual Primary Completion Date :||September 2014|
|Actual Study Completion Date :||September 2014|
HRCT scan in a specific postural position
Other: HRCT scan in a specific postural position
HRCT Scan taken in supine and lateral position
- Functional Respiratory Imaging [ Time Frame: 1 study visit (1 day) ]A low dose 3D spiral high resolution computed tomography (HRCT) scan will be taken on 2 volumes TLC and functional residual capacity (FRC) in both supine and lateral decubitus position. Image post processing is performed to look at local changes in airway or lobar volume [liter] and airway resistance [kiloPascal.seconds/liter] distribution in the lung
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Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT01893697
|Antwerp, Edegem, Belgium, 2650|
|Principal Investigator:||Wilfried De Backer, MD PhD||University Hospital, Antwerp|