The Influence of Posture on Airway Diameter, Resistance and Airflow Distribution in Healthy Subjects
Condition: Healthy Participants
Study type: Observational

Summary: 
      FRI could give the opportunity to investigate the possible effect of a lateral posture on
      airway diameter and airflow distributions. This physiological study in healthy subjects may
      help to identify the role of positioning as an aid in airway clearance techniques for
      patients with respiratory diseases.
    

Detailed description: 
      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.
    

Intervention name(s): HRCT scan in a specific postural position
Intervention type(s): Other
Intervention description(s): HRCT Scan taken in supine and lateral position
Observational model: Case-Crossover
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Healthy subjects