Introduction: FOT is a useful assessment tool in asthma, that could be used to assess responses to bronchodilators and bronchoconstriction (King et al. ERJ 2020). 30% of asthma patients may also have a breathing pattern disorder (Tay et al. RESP 2016) which may affect FOT measurements, impacting accuracy of reversibility and challenge assessments. This study aimed to examine the effect of breathing frequency (BF) on measures of airway resistance and reactance using FOT.?Method: Following a within-subject randomized study design 13 participants (male: 6; age: 30±8yr; height: 1.74±0.1m; weight: 78±15kg; normal spirometry) performed FOT (Resmon Pro, Restech Srl) at four BF (15, 20, 30, 40 breaths per minute), with measurements at each performed in triplicate. Data analyses were performed to assess differences between BF for measures of total airway resistance (R5, R11 & R19) and reactance (X5, X11 & X19).?Results: No significant differences (p>0.05) were found between BF for all measures. Although on average higher BF resulted in a marginal reduction in total airway resistance (table 1).?Conclusion: BF does not significantly impact measures of total airway resistance and reactance. Although higher BF may slightly influence results, this study suggests this is not at the level of expected positive bronchodilator or bronchoconstriction response via FOT (King et al. ERJ 2020). Further investigations should utilize a clinical population, to determine if there are greater implications in patients with obstructive lung disease.

Table 1. Total airway resistance BF15vsBF40. Mean±SD.