Water-sealed spirometer for measurements in newborns and infants

Details are given of two spirometers for use in neonates and infants < 12 mo old. The minimum volumes are 520 and 670 ml, respectively. The maximum volume changes that can be recorded are 250 and 450 ml, respectively. The minimal detectable volume changes are 0.4 and 0.6 ml, respectively. Rebreathing of dead space gas is prevented by a fan producing a flow of 6.2 and 10.2 l/min, respectively; 100% gas mixing after injecting a gas bolus in the two spirometers is achieved in 5.7 and 6.6 s, respectively. Resistance to airflow is 0.2 kPa.l-1.s (2 cmH2O.l-1.s) at 150 ml/s in both spirometers. The frequency response of both instruments is flat to 6 cycles/s. The instruments can be easily cleaned and are suitable for bedside measurements.