Post-acute sequelae of COVID-19 (PASC) is incurring a huge health and economic burden worldwide. There is currently no effective treatment or recommended drug for PASC.

This prospective randomized controlled study was conducted in a hospital in China. The effect of intermittent hypoxia exposure (IHE; 5-min hypoxia alternating with 5-min normal air, repeated five times) on dyspnea and fatigue was investigated in patients meeting the NICE definition of PASC. Patients were computationally randomized to receive normoxia exposure (NE) and routine therapy or IHE and routine therapy. Six-minute walk distance (6MWD) and spirometry were tested before and after the interventions; the Borg Dyspnea Scale (Borg) and the modified Medical Research Council Dyspnea Scale (mMRC) were used to assess dyspnea; and the Fatigue Assessment Scale (FAS) and the Chalder Fatigue Scale-11 (CFQ-11) were used to assess fatigue. The study was registered in the Chinese Clinical Trial Registry (ChiCTR2300070565).

Ninety-five participants (33 males and 62 females) were recruited between March 1, 2023 and December 30, 2023. Forty-seven patients in the IHE group received 10.0 (9.0, 15.0) days of IHE, and 48 patients in NE group received 10.0 (8.0, 12.0) days of NE. 6MWD, forced vital capacity (FVC), FVC %pred, forced expiratory volume in 1 s (FEV₁), FEV₁ %pred, tidal volume (V_T), and dyspnea and fatigue scales markedly improved after IHE (p < 0.05), and improvements were greater than in the NE group (all p < 0.05). Furthermore, participants in IHE group had better subjective improvements in dyspnea and fatigue than those in the NE group (p < 0.05). Compared with <10 days of IHE, ≥10 days of IHE had a greater impact on 6MWD, FVC, FEV₁, FEV₁ %pred, V_T, FAS, and CFQ-11. No severe adverse events were reported.

IHE improved spirometry and 6MWD and relieved dyspnea and fatigue in PASC patients. Larger prospective studies are now needed to verify these findings.