Objective: To assess thoraco-abdominal kinematics, respiratory muscle strength and electromyographic activity of the diaphragm (EAdi) in moderate-severe allergic rhinitis (AR) patients. Methods: A cross-sectional study involving 40 individuals (20 in the AR group) and 20 in the control group [CG]) was conducted. Ventilatory pattern and chest wall volume distribution (optoelectronic plethysmography), respiratory muscle strength (manovacuometry and sniff nasal inspiratory pressure [SNIP]), and EAdi were assessed in both groups. Results: The AR patients had impaired thoraco-abdominal kinematics (reduced total chest wall volume) (p = 0.004), lower values of total respiratory cycle time (p = 0.014) and expiratory time (p = 0.006). They also presented an increase of percentage contribution of the abdominal rib cage (p = 0.475) and respiratory rate (p = 0.019). A positive correlation among pulmonary rib cage tidal volume and MIP (r = 0.544; p < 0.001), SNIP (r = 0.615; p < 0.001), and MEP (r = 0.604; p < 0.001) was observed. After adjusting for age, BMI and gender through multivariate analysis, the individuals with AR presented lower values of MIP (β = -24.341; p < 0.001), MEP (β = -0.277; p < 0.001), SNIP (β = -34.687; p < 0.001) and RMS (β = -0.041; p = 0.017). Conclusions: The individuals with moderate-severe persistent AR had worse respiratory muscle strength, diaphragm activation and chest wall volume distribution with a higher abdominal contribution to tidal volume than the control group. These findings reinforce the notion that the upper and lower airways work in an integrated and synergistic manner.
Keywords: Allergic rhinitis; diagnostic techniques; lung function; maximal inspiratory pressure; muscle weakness; respiratory muscles.