Long COVID affects approximately 10% of COVID-19 survivors, with symptoms persisting
beyond the acute phase and impacting multiple organ systems. While some individuals
experience mild to moderate illness, others develop severe complications, such as Acute
Respiratory Distress Syndrome (ARDS), increasing the risk of long-term pulmonary
dysfunction. There is no universally accepted definition of long COVID, but it is often
categorized based on symptom duration: post-acute COVID-19 (symptoms persisting beyond
three weeks) and chronic COVID-19 (lasting beyond 12 weeks). According to NICE and the
Italian National Institute of Health (ISS), long COVID includes symptoms lasting between
4 and 12 weeks (ongoing symptomatic COVID-19) or beyond 12 weeks (post-COVID-19
syndrome), provided they are not attributable to alternative diagnoses.

Common symptoms include fatigue, dyspnea, cough, and chest pain. Some patients recover
spontaneously with rest, symptomatic treatment, and gradual physical activity, while
others require targeted rehabilitation. Since 80% of breathing effort relies on the
diaphragm, long COVID patients often exhibit altered breathing patterns, such as shallow
breathing and increased reliance on accessory muscles, leading to dyspnea, fatigue, and
inefficient respiration.

Rehabilitation programs have been shown to improve ambulation, hospital discharge rates,
and overall recovery in COVID-19 patients, highlighting their potential role in long
COVID management. Pulmonary rehabilitation, particularly the Active Cycle of Breathing
Technique (ACBT), is a structured method aimed at restoring normal breathing patterns,
improving respiratory muscle efficiency, and reducing airway irritation. ACBT consists of
controlled breathing, thoracic expansion exercises, forced expiration, and huffing,
facilitating airway clearance and optimizing lung function. Given the association between
physical inactivity and worse COVID-19 outcomes, rehabilitation strategies incorporating
breathing exercises and physical activity may be beneficial.

Pulmonary function studies indicate that Forced Expiratory Volume in 1 second (FEV1) and
the FEV1/FVC ratio generally remain within normal limits after COVID-19 recovery,
regardless of disease severity. However, impairments in Mid-Expiratory Flow (MEF25-75%)
suggest small airway dysfunction (SAD), which appears independent of disease severity but
may contribute to persistent respiratory symptoms. Early detection of pulmonary
abnormalities is crucial, and Impulse Oscillometry (IOS) is recommended for assessing
SAD. Studies indicate that up to 70-90% of symptomatic long COVID patients exhibit
persistent SAD up to five months post-infection, emphasizing the need for ongoing lung
function monitoring.

This retrospective and prospective study aims to evaluate whether ACBT, combined with
moderate daily physical activity, can alleviate symptoms such as cough, dyspnea, and
fatigue in long COVID patients. Effectiveness will be assessed using validated clinical
scales, including the Leicester Cough Questionnaire (LCQ), the Modified Medical Research
Council (mMRC) dyspnea scale, and the Visual Analog Scale (VAS) for fatigue.
Additionally, the study will investigate whether respiratory symptoms correlate with SAD,
assessed through IOS by analyzing changes in distal airway resistance (R5-R20) and
reactance (X5) before and after a six-week rehabilitation period. The rehabilitation
protocol involves performing ACBT twice daily at home for six weeks. Clinical and
respiratory functional parameters will be assessed before and after the intervention of
six weeks. To ensure adherence, patients will receive instructional materials, including
video tutorials and augmented reality tools. Additionally, participants will be
encouraged to engage in moderate physical activity, aiming for at least 6,000 steps per
day, tracked via smartphone applications.

Participants will be monitored over six weeks, with two scheduled visits: an initial
baseline assessment (V1) and a follow-up evaluation (V2).

The study protocol was approved by Ethics Committee in the session of 05/07/2022 with
protocol. No. 28421 of 07/06/2021.

Data will be collected in a dedicated electronic Clinical Records Form (CRF). The
database will be saved on a password-protected company Personal Computer (PC) which will
be updated at each visit and used exclusively for scientific research purposes. At the
time of enrollment, each patient will receive an alphanumeric code so that any
information collected during the study, and in particular sensitive data, is treated in
an anonymous manner. Data reporting patients' identifications will only be used to file
patients and collect informed consent.