By: Arslan Dogar

The first visit to Muhimbili National Hospital was amied at needs findings for the hospital which resulted in alot of projects that we could work on. These projects included; the bubble CPAP (continuous positive air pressure) machine, wall sanction machine, the length board, automatic chest compressor and others.

The project that we were assigned to complete was the Bubble CPAP machine for pediatric intensive care unit (PICU) at the hospital. There was an urgent need for the bubble CPAP machine in this unit of the hospital as it didn’t even operate a single CPAP machine.

Basically Bubble CPAP is a non-invasive ventilation strategy for newborns with infant respiratory distress syndrome (IRDS). It is one of the methods by which continuous positive airway pressure (CPAP) is delivered to a spontaneously breathing newborn to maintain lung volumes during expiration. With this method, blended and humidified oxygen-air mixture is delivered via short bi-nasal prongs or a nasal mask and pressure in the circuit is maintained by immersing the distal end of the expiratory tubing in water. The depth to which the tubing is immersed underwater determines the pressure generated in the airways of the infant. As the gas flows through the system, it bubbles out and prevents buildup of excess pressures. 

A Bubble CPAP Machine

The second visit to Muhimbili National Hosipal was aimed at gaining some primary data for the research. The activities during this visit basically included interviewing PICU staff of the hospital and collecting some technical data. 

The technical data obtained was as follows:

  • Pressure value of the oxygen supply: this was among essential data that was necessary for the design of the oxygen intake of the machine. The value of oxygen supply pressure is 68Psi or 460KPa approximately.


Pressure Gauge at The Hospital


  • Dimensions of standard oxygen connector

the dimensions of this connector were taken so that exact part can be searched for in the market or 3D printed if not available. The function of this connector is basically to connect the oxygen pipe to the oxygen supply interface.

Standard Oxygen Connector


  • The volume flow rate essential for the infants: this data basically enabled the capacity of air pump needed for the machine to be built. The capacity of air pump is given in liters of air it can pump per minute (L/min).
  • The Minimum and Maximum pressure values required for the inflation of the lungs of infants. The pressure of blended air mixture in the system is basically judged by the water level of the pressure relieving bottle from which the bubbles are given out. The pressure that is used for the infants is between 4-8 mmH2O. 

This technical date proved to be helpful at each step during the project each of these data had been utilized to design the machine and hence the pre-set objectives were attained to a reasonable extent. 

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