Non-Invasive Airway Mechanics
For resistance measurements on conscious subjects, use non-invasive airway mechanics (NAM). The NAM application involves monitoring both nasal and thoracic flows separately and simultaneously to calculate Specific Airway Resistance (SRaw) and its reciprocal, Specific Airway Conductance (SGaw)
Signals are collected using a double-chamber plethysmograph. The subject's body is placed in the thoracic chamber, the head is placed in the head chamber, and the two chambers are separated by an elastomeric neck seal.
Once a baseline is collected, subjects may be challenged with an agonist. Resulting phase shifts between nasal and thoracic flows are reflected in SRaw and SGaw values, indicating changes in airway resistance.1
Reported parameters
- Specific airway resistance
- Specific airway conductance
- Breath frequency
- Tidal volume
- Total volume breathed
- Minute ventilation
- Inspiratory time
- Expiratory time
- Peak inspiratory flow
- Peak expiratory flow
- End inspiratory pause
- End expiratory pause
- Relaxation time
- Expiratory flow at 50% volume (EF50)
- Others
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1Pennock, BE, CP Cox, RM Rodgers, WA Cain, JH Wells (1979). A non-invasive technique for measurement of changes in specific airway resistance. J. Appll. Physiology 46; pp 399-406.