The general objective of this project is to determine the best method to measure maximal inspiratory flow rates, to study their reproducibility and create reference equations in healthy subjects.

1. Reproducibility and reference values in normal subjects: the investigators will propose a method for measurement of the maximal inspiratory flow rates (MIFR) and establish their reproducibility in normal subjects. The variability of these inspiratory flow rates will be compared with the variability of effort dependent and non-effort dependent expiratory flow rates.

   Also, reference equations will be drawn up and compared to the only existing set of reference values (2) (needing a revision).

2. Reproducibility in disease: the investigators will evaluate the reproducibility of the MIFR in patients with neuromuscular diseases (Steinert muscular dystrophy, amyotrophic lateral sclerosis) and with upper airway obstruction (tracheal stenosis, thyroid enlargement) and compare to the reproducibility of expiratory flow rates in this population.

3. Monitoring of diseases: In the neuromuscular patients MIFR will be correlated to the existing parameters used for monitoring of these diseases (respiratory muscle strength, forced vital capacity), with a longitudinal follow-up.

In the patients with upper airway obstruction the MIFR (quantitative measurement) will be compared to the visual inspection (qualitative interpretation) of the maximal flow-volume loop and also the evolution after a therapeutic intervention (airway stenting, thyroidectomy) will be monitored.

Inclusion Criteria:

• healthy hospital workers or visitors

Exclusion Criteria:

• current smokers or ex-smokers with a history of > 80 PY
• Presence or history of serious illness or thorax deformity (questionnaire)
• recent respiratory tract infection (1 week)

Normal healthy subjects