Use of Bubble CPAP Compared to Nasal Prong Oxygen or Humidified High Flow in Children Under Five With Severe Pneumonia and Hypoxaemia: a Randomized Trial

Continuous Positive Airway Pressure (CPAP) is a common form of support for patients admitted to Intensive Care Units (ICUs) of industrialized countries with respiratory distress (1). Nasal CPAP (NCPAP) is effective in correcting hypoxemia and contributes to reducing the number of children requiring endo-tracheal intubation and mechanical ventilation (2). CPAP is most frequently delivered to neonates using conventional mechanical ventilators, and thus there is minimal or no cost saving. There are other ways of delivering CPAP, such as Bubble-CPAP, which requires a source of gas flow (typically 6-8 L/ minute in a neonate), an air-oxygen blender, a humidifier and a T-piece.(3). The expiratory arm is inserted in a bottle of water and the level of CPAP delivered is equivalent to the length of the expiratory tubing that remains under water. Robust equipment is now available at a fraction of the cost of mechanical ventilators. Bubble-CPAP has potential advantages over the mechanical ventilation, such as lower cost, ease of application by nursing staff, lower risk of complications, and has been proposed as an inexpensive method of delivering CPAP in developing countries (3).

High flow air/oxygen mix is useful in reducing the indication of mechanical ventilation (4); however, there is a lack of randomized studies comparing it with bubble CPAP or with standard flow O2 supplementation by nasal prongs. High flow air/oxygen mix uses flows of 2 litre per kg per minute of blended air/oxygen mix, usually with a low fraction of inspired oxygen (say 25-40%). It is easy to apply, but requires additional equipment to standard oxygen therapy, and closer monitoring. "High flow" delivers uncertain levels of CPAP, so it is not clearly superior to bubble-CPAP, and there have been no controlled comparative trials of these two techniques.

Pneumonia and malnutrition are two of the most common co-morbidities in children in developing countries (5). In hospitals in resource-poor settings, children with severe malnutrition and pneumonia often present with respiratory distress with or without severe hypoxaemia and impending respiratory failure (6). They initially receive O2 supplementation through nasal prong or face mask. Support from bubble CPAP might help to effectively treat hypoxaemia, improve respiratory function, avoid the need for mechanical ventilation and its complications, and reduce mortality.

Almost half of the patients admitted in the intensive care unit of the Dhaka hospital of ICDDR,B present with hypoxaemia, many with impending respiratory failure. Children with pneumonia also invariably have severe malnutrition with or without diarrhoea (Chisti MJ, MMed thesis, unpublished data). They often need mechanical ventilation, with attendant costs, complications and high mortality rates. However, no published data are available about the use of bubble-CPAP in children with pneumonia and malnutrition and there have been no controlled trials of CPAP in developing countries.

The Hypothesis is:

In children with severe pneumonia and hypoxaemia the probability of treatment failure (see definition below) will be significantly lower when respiratory support is initially provided by bubble-CPAP or high-flow, humidified air/O2 mix by nasal prongs, compared to standard oxygen flow.