Abstract Persistent respiratory symptoms after COVID-19 have been associated with impaired ventilation–perfusion matching and muscle dysfunction. However, the relationship between inspiratory muscle fatigability and pulmonary aerosol deposition remains unclear. Objective To investigate the association between the Fatigue Index Test (FIT) and pulmonary aerosol deposition in symptomatic and asymptomatic individuals recovered from acute COVID-19. Methods Thirty-three adults previously infected with SARS-CoV-2 were included, of whom 10 (30.3%) were asymptomatic and 23 (69.7%) remained symptomatic after recovery. The median age was 46 24 years, 78.8% were women, and the median post-infection time was 24 3.5 months. Pulmonary aerosol deposition was assessed by gamma scintigraphy using technetium-99m–labeled diethylenetriamine-pentaacetic acid (99mTc-DTPA). Total and regional lung activity (right and left) were quantified after standardized inhalation with a vibrating-mesh nebulizer (Aerogen® Solo) generating 3.0–4.5 µm particles. Participants inhaled 1.5 mL of 99mTc-DTPA (5 mCi) in saline for 4–5 minutes while seated, performing slow, deep breaths with a 3-second inspiratory pause. Inspiratory muscle performance was evaluated using the PrO2® (Smithfield, RI, USA) system through the Test of Incremental Respiratory Endurance (TIRE), which provides maximal inspiratory pressure (MIP), sustained maximal inspiratory pressure (SMIP), inspiratory duration (ID), and the Fatigue Index Test (FIT). The FIT score represents the ratio between sustained and maximal effort, indicating inspiratory muscle fatigability. Results Symptomatic post-COVID-19 individuals exhibited lower inspiratory performance and higher muscle fatigability compared with asymptomatic participants. Median IQR values for MIP were 73 37 vs. 114 22.5 cmH2O, for SMIP 502 222 vs. 935.5 215 PTU, and for FIT 22.3 9.2 vs. 46.25 20.28 (all p 0.001). Inspiratory duration was shorter in symptomatic participants (10 3.5 vs. 15.5 3.38 s, p 0.001). Pulmonary scintigraphy revealed a marked reduction in aerosol deposition among symptomatic individuals, with total lung values of 327.16 232.97 vs. 618.26 187.88 Kct (p = 0.006) and right lung values of 174.95 141.26 vs. 387.51 68.70 Kct (p 0.001). Importantly, the FIT score showed a strong positive correlation with total aerosol deposition (r = 0.93, p 0.001), indicating that lower inspiratory muscle endurance in symptomatic individuals was associated with reduced and less efficient pulmonary aerosol distribution. Conclusions Symptomatic post-COVID-19 individuals exhibit significant inspiratory muscle fatigability and reduced pulmonary aerosol deposition compared with asymptomatic counterparts. The strong correlation between FIT and pulmonary deposition underscores a potential physiological link between inspiratory muscle endurance and aerosol distribution efficiency. This abstract is funded by: CNPQ 421756/2021-7, cNPQ 313165/2021-1
Andrade et al. (Fri,) studied this question.