Indirect estimation of laryngeal resistance via airflow redirection

Objectives: Our aim was to estimate aerodynamic parameters of laryngeal resistance (Rl) and aerodynamic power indirectly from a subglottal pressure (Ps) data trace obtained with the airflow redirection system. Methods: During airflow interruption, the airflow redirection tank fills capacitively with pressure until it reaches the subject's Ps. Therefore, a time constant, τ, can be extracted from the data trace and used to calculate Rl. The validity of applying this method to the estimation of RL was demonstrated with a computer model. Estimations were made for values of 10, 20, 30, 40, and 50 cm H2O per liter per second (L/s). Twenty subjects performed 10 trials on the experimental system designed to measure Ps. The values of RL and aerodynamic power were then calculated. Results: The computer model simulation yielded a maximum measurement error of 3.00% and a mean error of 1.78%. In human subject testing, the mean ± SD laryngeal resistance was 22.61 ± 8.65 cm H2O per L/s, the mean Ps was 6.91 ± 1.94 cm H2O, and the mean aerodynamic power was 0.247 ± 0.170 kPa × (L/s). Conclusions: The proposed method of data analysis enables a clinician to estimate Rl and aerodynamic power from a single experimental trial designed to measure Ps. This technique provides the clinician with an aerodynamic function report that can be used to analyze patient health and treatment efficacy.