Within-Breath Total Respiratory Input Impedance in Healthy Adult Subjects

Purpose and rationale Assessment of lung function requires the evaluation of pulmonary function by spirometry. However, some patients (e.g. children, elderly, or diseased individuals) may have difficulty performing the related forced maximal respiratory maneuver correctly. Forced oscillation technique (FOT) is increasingly being used in clinical settings to evaluate lung function noninvasively by measuring the mechanical input impedance of the respiratory system. FOT measures lung impedance during tidal breathing, requiring minimal patient cooperation. Recently a new methodology (within breath analysis) has emerged to evaluate changes that occur in the impedance during the breathing activity. The within-breath calculation of impedance allows separating the contribution of inspiration and expiration to the measured parameters.

The purpose of this study is to establish reference ranges for within breath FOT parameters and their short term variability.

Objectives Primary: To derive equations to predict normal values and normality ranges for within-breath respiratory system resistance, reactance and related parameters at the selected stimulating waveform and to measure the short term variability of such parameters.

Secondary: To demonstrate the equivalence of the results of a single multiple-breath test to results obtained as an average of 3 consecutive repeated tests.

Study design This will be a prospective multi-center trial of healthy subjects. After signing the Informed Consent, an interview and physical examination will be performed. The examiner will confirm that subjects are able to perform acceptable and repeatable spirometry. FOT measurements will be performed, followed by standard spirometry measurements.

Study Duration This is a single visit study. Subject participation will be completed in 1 hour and 15 min. Enrollment of all subjects is expected to take 23 weeks (6 months).

Inclusion criteria

• Subjects ≥ 18 years of age.
• Signature of the written informed consent

Exclusion criteria

Subjects will be excluded if they meet at least one of the following conditions:

• Abnormal spirometry defined as FEV1, FEV1/VC and VC below the LLN as established by the Global Lung function (GLI) 2012 reference equations.
• Smokers or ex-smokers
• BMI >30 kg/cm2
• History of respiratory symptoms using the ECRHS II screening questionnaire (www.ecrhs.org)

• Wheezing
• Cough
• Phlegm production
• Dyspnea
• Feeling of chest tightness
• Night awakening due to a cough attack
• Have a history of pulmonary or cardiac disease
• Had a recent (e.g., in the last 4 weeks) respiratory tract infection
• Have a neurological or neuromuscular disorder