The Influence of Posture on Airway Diameter, Resistance and Airflow Distribution in Healthy Subjects

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.

Study Overview

• Status: Completed
• Conditions: Healthy Participants
• Intervention / Treatment: Other: HRCT scan in a specific postural position

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.

• Study Type: Observational
• Enrollment (Actual): 5

Contacts and Locations

Study Locations

• Belgium
  • Edegem
    • Antwerp, Edegem, Belgium, 2650
      • UZA

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 16 years to 38 years (Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

• Sampling Method: Non-Probability Sample

Study Population

Healthy subjects

Description

Inclusion Criteria:

1. Men or female patients age > 18
2. No respiratory disease in the days prior to the enrollment
3. Able to perform a lung function tests
4. Motivated to participate.
5. Written informed consent from the subject prior to the participation

Exclusion Criteria:

1. Serious co-morbidity which would interfere with the examinations
2. One or multiple CT scans of the chest during the last year.
3. Deformities or complications preventing patients to maintain side lying position during the scanning procedure

Study Plan

How is the study designed?

Design Details

• Observational Models: Case-Crossover
• Time Perspectives: Prospective

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Healthy Participants; HRCT scan in a specific postural position	Other: HRCT scan in a specific postural position; HRCT Scan taken in supine and lateral position

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Functional Respiratory Imaging	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	1 study visit (1 day)

Collaborators and Investigators

• Sponsor: University Hospital, Antwerp
• Investigators: Principal Investigator: Wilfried De Backer, MD PhD, University Hospital, Antwerp

Study record dates

Study Major Dates

• Study Start: April 1, 2013
• Primary Completion (Actual): September 1, 2014
• Study Completion (Actual): September 1, 2014

Study Registration Dates

• First Submitted: June 27, 2013
• First Submitted That Met QC Criteria: July 2, 2013
• First Posted (Estimate): July 9, 2013

Study Record Updates

• Last Update Posted (Estimate): May 28, 2015
• Last Update Submitted That Met QC Criteria: May 27, 2015
• Last Verified: May 1, 2015

More Information

Terms related to this study

• Other Study ID Numbers: RESPT_2013_01