Methacholine challenges: comparison of different tidal breathing challenge methods.

Tidal-breathing methacholine challenges are now recommended by guidelines, to avoid the bronchoprotective effects of deep inhalation. This study compared different tidal breathing methacholine challenge methods; assessed the agreement between tidal dosimetric and continuous output challenges; and assessed challenge repeatability with different methods. 15 asthma patients performed dosimetric challenges and a continuous-output breath-actuated challenge, all ≥3 days apart.