(i) To validate the inversed occlusion technique by comparing the results of resistance obtained on the relaxed expiratory occlusion monitor (REOM) with the resistance obtained with respiratory oscillometry (OSC) measurements on the tremoflo® C-100 and (ii) explore (within-test and day-to-day) repeatability and responsiveness to change of this technique when used as home monitoring device in children with asthma.

Children will be evaluated for eligibility by telephone or videoconferencing. After eligibility and consent documented by email by parents and on a source document by the research assistant:

1. Children will receive by courier one new REOM unit, a tablet with charger, and related disposables (nose clips etc.),

2. At a videoconference planned at a mutually conveniently time with the child and their parents the following will be obtained;

   1. Basic demographics (date of birth, age, sex, ethnicity, height, weight) and asthma morbidity and medications.
   2. Training on the REOM unit measurement using a recorded instructions video, followed by hand-on use of the unit under remote observation. The Research Assistant will teach the parents and child in the REOM, namely on how to use the unit to measure resistance until it is mastered and reproducible, how to complete the brief daily questionnaire, and how upload data from the REOM to the tablet by Bluetooth. Confirmation of the validity and reproducibility of the technique will be obtained by review of the measurement output that will be sent by WIFI automatically from the tablet to a protected google drive (with the patient identified only by a code) accessible to the Coordinating Centre.
   3. Briefly, a minimum of three (3) reproducible measurements of Reo on the REOM will be obtained in accordance to the following standardized procedures: the subjects will be asked to be comfortably seated upright, with the head slightly tilted upward at an angle of about 15 degrees from neutral position to prevent upper airway obstruction, with the cheeks tightly supported to prevent upper airway shunting. A nose clip will be worn to prevent nasal air leak. Subjects will be instructed to breathe normally in a single-use bacterial/viral respiratory filter connected to the mouthpiece of the REOM device. This manoeuvre will be repeated for a maximum of 6 trials to obtain a coefficient of variation (CV) ≤15% on at least 3 Reo measurements with visual remote inspection of the curves and results via Bluetooth connection by the research assistant. Each trial will last 20 to 30 seconds to obtain a minimum of 3 to 6 valid expirations per trial. The mean Reo of 3 reproducible measurements will be calculated at the peak (Reo1) and the low (Reo2) flow.

3. Once the technique is mastered, the child will be asked to:

   1. Perform the REOM measurements once daily before receiving their asthma controller medication, ideally at the same time in the evening.
   2. If the child requires a rapid beta-2 agonists because of symptoms, a before and after measurement will be obtained 30 minutes after the dose has been administered to document responsiveness to change once a day when sick.
   3. Once a week, a short questionnaire including the cACT (or ACT for 12 years and older), a question about an acute care visit or use of rescue oral corticosteroids, and occurrence of any adverse event will be sent by text message or email (patient preference) throughout the study duration.

4. A research assistant will contact the family at 7±3 days, 14±3 days, and monthly thereafter or, if in case of problem with the equipment or interruption in REOM measurements/response to the weekly questionnaire.

The study duration will be 4 months (to maximize the chance of an exacerbation).

Inclusion Criteria:

1. Children aged between 6 and 17 years old

2. Adequate understanding of French or English

3. Asthma diagnosis confirmed by a physician

4. Poor asthma control in the past 6 months, that is,

   1. an acute exacerbation requiring oral corticosteroids, or
   2. an FEV1 <80% of predicted, FEV1/FVC ratio below the lower limit of normal, or significant (≥12%) reversibility in FEV1, or
   3. a total score <20 on the child Asthma Control Test (ACT) for children aged ≤11 years or on the ACT for those aged ≥12 years).

Exclusion Criteria:

1. Inability to produce a good seal around the mouthpiece when previously tested with spirometry
2. Oscillometry or REOM, contra-indication to performing respiratory tests (e.g., facial trauma, chest pain, severe scoliosis)
3. Other reason interfering with respiratory testing.

The asthmatic study subjects will be recruited a the Sainte-Justine University Hospital Center, Montreal, QC. Recruitment will be performed by Dr. Ducharme's research staff. The study will be conducted remotely with patients who consented to the Pediatric asthma database and Biobank of the Sainte-Justine University Hospital Center or among the families subscribing to the Asthma Clinic newsletter or seeing the advertisement on the CHUSJ website.