Airway Pressure During Humidified High Flow Nasal Cannula Therapy in Children
Condition: Bronchiolitis; Pneumonia; Bronchial Asthma
MeSH terms: Bronchiolitis; Asthma
Study type: Observational

Summary: 
      Humidified High Flow Nasal Cannula (HHFNC) is a new modality of respiratory support for
      children with respiratory failure. Despite its extensive use in pediatric and adult
      population, the exact mechanism of work of HHFNC is not fully explained.The objective of the
      investigators' research project is to determine the relationship between the amount of airway
      pressure that can be delivered at specific flow levels of HHFNC. This information will allow
      the investigators to use HHFNC in a much more informed and safe manner.
    

Detailed description: 
      Background: Respiratory failure is one of the most common reasons for admission to the
      Pediatric Critical Care Unit (PCCU). 17% of children admitted to a PCCU require some form of
      invasive or non-invasive mechanical respiratory support. HHFNC therapy was first introduced
      in early 2000 and hence is a relatively new mode of respiratory support. One of the proposed
      mechanisms of action of HHFNC is by providing airway positive pressure hence considered as
      non-invasive mode of ventilation in pediatrics. However, the actual amount of positive airway
      pressure that HHFNC provides at increasing flow rates has not been well studied in children.

      Objectives: The investigators' objectives are to measure the positive airway pressure
      delivered with increasing HHFNC flow rates in children, and to evaluate the variables that
      may influence the delivery of positive airway pressure during HHFNC.

      Methods & Design: This is an observational cohort study which will be conducted at McMaster
      children's hospital, pediatric critical care unit (PCCU). Children under 18 years of age,
      admitted to PCCU, who require respiratory support by HHFNC, as determined by the caring
      physician; and informed consent and or assent of substitute decision maker. Those children
      must have NG tube of size 10 French or smaller inserted at time of HHFNC application.
      Patients who are on intermittent NGT suction will be excluded. Airway pressure will be
      measured indirectly using esophageal pressure liquid filled method.

      Data Analysis Baseline demographics will be summarized using counts (%) for categorical
      variables, and mean (standard deviation) or median and interquartile range (IQR) as
      appropriate for continuous variables. Estimates of the pressure will be reported as mean (95%
      confidence interval [CI]). Relationship of pressure to delivered flow will be analysed using
      analysis of variance. Regression methods will be used to determine if the following factors
      delivered flow per weight of patient, patient size, disease severity, work of breathing and
      nasal cannula: nares diameter ratio are associated with air pressure
    

Observational model: Cohort
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        Children under 18 years, admitted to PCCU, who require respiratory support using HHFNC, as
        determined by the caring physician; and informed consent of substitute decision maker will
        be included in the study.