Section 868.2550 - Pneumotachometer(a)Identification. A pneumotachometer is a device intended for medical purposes that is used to determine gas flow by measuring the pressure differential across a known resistance. The device may use a set of capillaries or a metal screen for the resistive element.(b)Classification. Class II (special controls). The device is exempt from the premarket notification procedures in subpart E of part 807 of this chapter subject to the limitations in § 868.9 .47 FR 31142, July 16, 1982, as amended at 84 FR 71811 , Dec. 30, 2019