Measurement of air flow in the maxillary sinus by hot-film technique

A method of hot-film-anemometry was developed to investigate the velocity of air flow in the maxillary sinus which has hitherto not been detected by other methods. The hot-film-probe can registrate the slow but rapidly changing air flow dependent on the respiratory cycles. This study was performed during sinuscopy. The average of measurement values by quiet respiration was found in the sinus of 8 cm/sec during a velocity in the nose of 5 m/sec. The respiratory fluctuations in the nose induce a movement stream of circulation in the sinus. When inspiration changes to expiration there was still a flow but at a lower degree. No flow in the sinus could be observed between respiratory cycles. After sniffing the velocity peak rises to higher values. The air flow in the sinus depends on the patency of the ostium. In case of a reduced air flow we can distinguish between a partially open ostia and an obstructed one. The measurement demonstrates an injector-effect beside the influence of pressure difference and diffusion on the ventilation of the sinus.