Obstructive airways disease is the most common group of acute illnesses leading to hospital treatment in children. This group consists of different age-related diagnoses, such as bronchiolitis in infants or wheezing and asthma in older children. Though these entities overlap with each other, they have common characteristics and the same leading symptom breathing distress.

The investigators aim conduct an observational cohort study to examine if the clinical course of respiratory distress be quantified and the treatment improved in children with acute breathing difficulty using a new non-touch non-invasive SLP measurement device?

Thora3Di is a new CE- and FDA-approved medical device able to measure chest and abdominal wall movements during tidal breathing with a method called structured light plethysmography (SLP). The method is non-touch and non- invasive, it does not need any connection with the child.

One-month- to 12-years-old infants and children are recruited from the paediatric wards at Evelina London Children's hospital. The child lies or sits within the field of vision of the SLP device with their chest and abdomen exposed. A grid pattern of normal light will be projected onto the chest and changes in the format of the grid as the infant or child breathes will be recorded by the SLP device. Data will be collected for each child for 3-5 minutes once in 24 hour periods for 2-10 times during hospital stay.

The aim is to reduce duration of hospital stay by finding predicting parameters for obstructive airways diseases with the new SLP method, and further aim to standardization of treatment strategies, to reduce expenditure.

Cohort pilot study to characterise the chest wall movement during tidal breathing in children admitted due to acute obstructive airways disease, using non-invasive SLP methodology (Thora3DiTM).

The investigators propose to utilise the SLP in children admitted for obstructive airways disease and track progression of their condition during the hospital stay. Focus will be in the SLP output, and investigators aim to 1) quantify the breathing distress and whether this number has an effect on the patient outcome and 2) further aim to see if regional changes in the thoracic-abdominal movement can be recognized by the measurement method.

The data collected from this study will allow investigators to characterise chest wall movements in children with obstructive airways disease and to examine the effect of the treatment on this movement.

Study population

Investigators will aim to recruit:

• 35-60 children between the ages of 1 month and 12 years with acute obstructive airways disease
• Admitted to hospital within 24 hours

Locations: Participants are children, in Evelina Children's hospital as a patient due to obstructive airways disease

The eligible children admitted to hospital will be identified at the clinical handovers and after obtaining the parental consent to participate in the study, the first measurements are performed as soon as possible, however within the first 24 hours of admission. The SLP measurements are repeated in 24 hour intervals 2-10 times depending on the duration of hospital stay.

Clinical patient data of age, sex, ethnicity, weight and length will be collected. A member of the clinical / research team (respiratory clinical fellow) collects structured data on the breathing distress using a modified pulmonary index scale for children (mPIS).

Measurement of standard clinical variables, such as respiratory rate, heart rate and oxygen saturation will be made each time the SLP readings are recorded. The measurement will be taken on a bare skin with a white medical adhesive tape to cover any existing medical attachments on thoracic-abdominal region (such as ECG electrodes). Alternatively, measurements can be made if the child is wearing a close fitting white garment without any creases (such as a babygrow).

A structured light pattern will be projected onto the chest and abdominal wall and the movement of this pattern as the patient breathes will be recorded for 3-5 min. The total period of testing per session should take approximately 15 minutes per person, including the movement of the device and the positioning of the patient.

Physiological and clinical data collection at each study point:

Dates of onset of breathing difficulty, admission and discharge Oxygen treatment and breathing support (Flow in L/min for HFNC, Fi02 %O2, CPAP settings) Current medication Need for NG-tube Need for IV-fluids Heart Rate SaO2 Respiratory Rate

Data analysis will include the traditional time indices from tidal breathing, and the variability of these time indices.

Appropriate statistical analyses will be identified depending on the study and distribution of the samples (parametric vs. non-parametric). It is suspected that t-tests (one-sample to two sample), analysis of variance (ANOVA), or Mann-Whitney-U tests will be used where appropriate.

The investigators will also explore novel higher levels of data interpretation including Bayesian interpretation of respiratory function, and machine learning to predict disease diagnosis, severity and discharge.

Inclusion Criteria:

• Age 1 month to 12 years
• Any children who have been admitted to ELCH with a diagnosis of acute obstructive airways disease within 24 hours
• Weight over 3 kg

Exclusion Criteria:

• Weight less than 3kg
• History of thoracic or abdominal surgery, or any acute or chronic condition that, in the investigator's opinion, would limit the patient's ability to participate in the study
• Patients with significant co-morbidities resulting in clinical instability (assessed by the clinician at screening only), such as diaphramatic dysfunction, tracheostomy or need for non-invasive or invasive ventilation

Children admitted to paediatric HDU/ICU wards for acute obstructive airways disease aged 1 month to 12 years