Acute Viral Bronchiolitis (AVB) is one of the leading causes of respiratory illness and hospitalization among infants during the first year of life, generating a substantial burden on healthcare services and public health expenditures. Despite the widespread use of respiratory physiotherapy in clinical practice, there is limited evidence regarding its effectiveness in preventing hospital admissions when provided in an outpatient setting.

This quasi-experimental study aims to evaluate the impact of an outpatient respiratory physiotherapy protocol on hospitalization rates among infants up to 12 months of age diagnosed with mild to moderate acute viral bronchiolitis in the public healthcare system of Sorocaba, Brazil. Infants referred for respiratory physiotherapy will be compared with a similar group of infants who receive standard medical care without physiotherapy referral.

The physiotherapy protocol includes slow expiratory techniques, rhinopharyngeal retrograde clearance, cough stimulation, and continuous positive airway pressure (CPAP) when clinically indicated. Participants will be followed through medical records and telephone monitoring.

The primary outcome is hospital admission due to bronchiolitis. Secondary outcomes include length of hospital stay, healthcare costs, and clinical evolution. The findings may provide evidence on whether outpatient respiratory physiotherapy can reduce hospitalizations and optimize healthcare resource utilization in infants with acute viral bronchiolitis.

Acute Viral Bronchiolitis (AVB) is the most common lower respiratory tract infection in infants and one of the leading causes of emergency department visits and hospital admissions during the first year of life. The disease imposes a substantial burden on healthcare systems, particularly during seasonal epidemics, resulting in increased healthcare utilization and costs.

Although respiratory physiotherapy is frequently used in clinical practice, its role in the management of bronchiolitis remains controversial. Most available studies have focused on hospitalized infants and have shown inconsistent results regarding clinically relevant outcomes. Furthermore, evidence regarding the effectiveness of respiratory physiotherapy in outpatient settings is scarce, and little is known about its potential impact on hospital admission rates and healthcare costs.

This study will be conducted in the public healthcare network of Sorocaba, São Paulo, Brazil, and is designed as a quasi-experimental study intended to emulate a clinical trial under real-world conditions. Infants up to 12 months of age diagnosed with mild or moderate acute viral bronchiolitis in participating emergency care units will be included. Participants referred for outpatient respiratory physiotherapy will constitute the intervention group, while infants with similar clinical characteristics who are not referred for physiotherapy will serve as the comparison group.

The respiratory physiotherapy protocol will include slow expiratory techniques, rhinopharyngeal retrograde clearance, cough stimulation, and continuous positive airway pressure (CPAP) when clinically indicated. Clinical assessment and treatment decisions will be based on standardized evaluation procedures and disease severity classification using the Wang Bronchiolitis Severity Score.

Data will be obtained from electronic medical records, physiotherapy records, and follow-up telephone contacts. The study aims to generate evidence regarding the effectiveness of outpatient respiratory physiotherapy in reducing healthcare utilization and improving the management of infants with acute viral bronchiolitis within a public healthcare system.

Inclusion Criteria:

• Infants aged 12 months or younger.
• Clinical diagnosis of acute viral bronchiolitis.
• Mild or moderate bronchiolitis according to clinical assessment and Wang Bronchiolitis Severity Score.
• Initial evaluation performed at a participating emergency care unit (UPA).
• Parent or legal guardian able and willing to provide informed consent for participants receiving direct physiotherapy care.

Exclusion Criteria:

• Severe bronchiolitis requiring immediate hospitalization or emergency medical intervention.
• Infants who did not follow the predefined clinical care pathway (e.g., no initial evaluation at a participating emergency care unit).
• Absence of a clinical diagnosis of acute viral bronchiolitis by the attending pediatrician.
• Any medical condition that, in the opinion of the clinical team, would make participation inappropriate or interfere with study procedures.

Individual participant data (IPD) will not be shared because the study involves identifiable health information from infants obtained through medical records and follow-up contacts. Although the data will be anonymized for analysis, no data-sharing plan has been established, in accordance with institutional policies and ethical requirements to protect participant confidentiality.

This is an open-label, non-randomized, quasi-experimental study. Participants, caregivers, healthcare providers, investigators, and outcome assessors are aware of the intervention status, as group assignment is determined by the routine clinical referral pathway for outpatient respiratory physiotherapy.