Bronchiolitis (BQ) is an acute viral infection of the lower respiratory tract that affects the bronchioles of babies younger than 24 months of age. Respiratory physiotherapy (FTR) appears as a complementary treatment measure in clinical guidelines and consensus on the management of BQ. Nebulization with 3% hypertonic serum before the FTR session induces an osmotic flow of water in the mucus, which facilitates drainage and reduces edema in the submucosal tissue.

Once each patient legal guardians has signed the informed consent document and it has been verified that the inclusion criteria are met, participants will be assigned the same identification number (ID) that is related to its Clinical History (CH) by simple coding; custody of the file with the relationship of each ID with its CH will be the responsibility of the principal investigator. The method of blinding in the allocation will be carried out by choosing envelopes sealed by an external investigator to the study. The contents of the envelopes will be randomized by computer using the numerical randomization sequence generated with R ver 5.3.1 (R Foundation for Statistical Computing, Institute for Statistics and Mathematics, Welthandelsplatz 1, 1020 Vienna, Austria) based on stratified sampling for homogeneity , in two groups: nebulization with 3% hypertonic solution (group A) and in the nebulization group with 0.9% saline solution (group B).

None of the participants who make up both the control and intervention groups will be prohibited from regular pharmacological treatment as prescribed by their doctor, such as Ventolin. It will be collected in the investigator's notebook the medications that each patient has prescribed by their doctor. But applying a bronchodilator is not part of the protocol, because physiotherapists cannot prescribe or administer a drug. Before receiving the usual and standard manual techniques of respiratory physiotherapy, patients receive nebulization, group A with hypertonic serum 4 ml 3% and group B with a single-dose saline (0.9 NaCl) physiological serum 5 ml for 8 minutes, both with nebulizer Philips® vibrating mesh. The effects of both are similar in effects, in terms of secretions and their osmotic effects. The aim of this study is to evaluate if the type of serum affects the results of the manual physiotherapy that is later carried out on children, but there is no clinical problem for randomly giving one serum or another, as to what is the effect of the serum on itself.

The intervention ends with a 20-minute session of Respiratory Physiotherapy based on slow expiratory flow: a passive technique of expiratory aid applied to the participants by means of slow thoracic-abdominal pressure that begins at the end of a spontaneous expiration and continues until the residual volume. The physiotherapist through assisted cough or stimulation of the trachea achieves expectoration of sputum. Care must be taken during the maneuvers to maintain a supine position of the patient in a 30-degree incline, to avoid episodes of gastroesophageal reflux and decrease the risk of vomiting.

Both groups will receive 3 evaluations by an investigator who will be blinded on the treatment and the objectives. The evaluations will be carried out at the beginning of the session (T0), immediately after the nebulization (T30) and 10 minutes after the end of the 20-minute physical therapy intervention (T60). This same treatment and evaluation sequence will be carried out every month for 6 months.

The main variables will classify the participants according to the initial clinical severity score proposed by Wang (WS), the Wood-Downes Scale modified by Ferres (WDF-S) and the Pulmonary Score (PS) in addition to the measurement of Sp2 and heart rate (FC) measured through a pulse oximeter (Radical Touchscreen from Massimo®, Masimo Corporation, Irvine, CA)

Inclusion Criteria:

• Have a medical diagnosis of a recurrent wheezing.
• Have the informed consent signed by the legal guardians of the kid.

Exclusion Criteria:

• Acute bronchitis with score> 9 according to the Wang and Pulmonary Score clinical scale.
• Acute BQ with score> 8 on Ferres' modified Wood-Downes scale (WDF-S)
• Parental refusal
• Comorbidity as cardiac, neurological or traumatic pathology.
• Congenital anomalies.
• Chronic pulmonary pathology such as bronchodysplasia.
• Severe obstruction with a punctuation >10 according ESBA and >7 according pulmonary score.