Breathing patterns in people with exercise-induced laryngeal obstruction

Exercise-induced laryngeal obstruction (EILO) is common, but we lack readily available diagnostic tools. The larynx represents an important point of resistance in the airways, and we therefore hypothesized that EILO is associated with characteristic breathing patterns possible to record from a standard incremental ergospirometry test. We studied 24 individuals with moderate/severe EILO and 20 individuals with no-EILO, mean (SD) age 17 (6.1) and 24 (6.4) years, respectively. EILO versus no-EILO was verified from maximal continuous laryngoscopy treadmill exercise (CLE) tests, which also included ergospirometry. We described the relationships between minute ventilation (V-E) versus tidal volume (V-T) and V-E versus carbon dioxide output (VCO2), using respectively quadratic and linear equations, and applied adjusted regression models to compare ergospirometry data and curve parameters. Compared to the no-EILO group, the group with EILO had prolonged inspiratory time (T-in), lower breathing frequency (B-f), lower V-E, and lower inspiratory flow rate (V-in) at peak exercise. Mathematical modeling of the breathing pattern relationships was feasible in both groups, with similar coefficients of variation. For V-E versus V-T, the mathematical curve parameters were similar. For VE versus VCO2, the slope was similar but the intercept was lower in the EILO group. EILO was associated with prolonged T-in, lower B-f, V-E, and V-E. The relationship between V-E versus V-T was similar, whereas for V-E versus VCO2, the slope was almost parallel but shifted downward for the EILO group. Most ergospirometry data overlapped, except Vin which discriminated between EILO and no-EILO in a promising way.