Objective: A vortex whistle (VW) is a low-cost device that produces an acoustic signal with a frequency directly proportional to the airflow moving through it. We have previously reported on the use of a VW in the measurement of forced vital capacity (FVC) and slow vital capacity (SVC) in typical subjects. However, our initial VW design limited peak flow to approximately 2 L/s, with the VW resistance resulting in a prolongation of the FVC. When the expiratory task is prolonged, expected measures of FEV1 (forced expiratory volume in the 1st second) and the FEV1/FVC ratio (70-80% in adults) may not be valid. This presentation describes a new VW designed to produce higher peak flows and more closely replicate the flow profile observed in a typical spirometer-obtained FVC.

Methodology: Forty young adults with no report of respiratory or voice disorder were tested using (1) the Koko Sx1000 pneumotach-based spirometer, and (2) a specially designed high flow, low resistance vortex whistle system (VWS) comprised of a 3D printed VW and audio analysis software.

The two tasks were: (1) FVC using the Koko with the subject instructed to take a maximal inhalation followed by a “blast” of air and continued expiration for 6 seconds; (2) FVC using the high-flow VW with similar instructions. The VW signal was recorded at 44.1 kHz, 16 bits using a lavalier microphone.

Results: The high-flow, low-resistance VW was observed to correlate strongly with the Koko system for both FVC (r = 0.92, r2=0.85, SE = 0.37 L) and FEV1 (r = 0.93, r2=0.83, SE = 0.30 L). In addition, mean FEV1/FVC ratios were at expected levels for typical subjects for both the Koko and VWS (78.81% vs. 81.73%) and nonsignificantly different.

Conclusions: The newly designed high flow VW can provide a wider range of respiratory measures (FVC, FEV, FEV1/FVC ratio) that complement our previous design that provided accurate SVC results. These findings expand the potential of a VW to provide low-cost measures that aid in the assessment of respiratory function in settings where traditional spirometry may be unavailable or unaffordable.