[A simple method for improvement of the measurement of respiratory impedance in humans by increasing oropharyngeal impedance using cheek and mouth floor clamps].

It is known, that the upper airway (oropharyngeal) impedance (Z(op)) influences the measured input impedance of the respiratory system (Zrs). This investigation deals with simple methods reducing the artefact caused by Z(op). The following methods have been examined: (1) Supporting the cheeks with fingers, (2) supporting the cheeks and the floor of the mouth with fingers and (3) using a new mechanical clamp for the cheeks and the floor of the mouth. The effect of these procedures on Zrs, were investigated on two subjects. Also Z(op) has been estimated during a voluntary closure of the glottis (VALSALVA manoeuvre). The impedance has been assessed as well with forced sine shaped oscillations as with the pulsatile technique. All three procedures show, compared to measurements without any support, an increase of the Zrs, especially at high values. The highest increase has been obtained while using the clamp (up to 50%). The varied impedance must be placed in parallel to Zrs, because Z(op) increases even more than Zrs. So, by applying the clamp the subjects is better coupled to the measuring system. The clamp is easy to handle, leads to more exact values, and increases the inter- and intra-individual reproducibility.