Oxygen therapy in pediatrics

Accuracy of a novel system for oxygen delivery to small children

OBJECTIVE

Oxygen therapy for infants and small children in developing countries is often not available. Entrainment devices may provide an accurate and precise concentration of oxygen when used at the flow rates appropriate for infants and small children.

METHODS

A continuously adjustable entrainment device was tested to determine the concentrations and flows of oxygen delivered by using low inlet flow rates suitable for therapy for infants and small children and 3 distinct oxygen delivery systems that varied in their resistive load.

RESULTS

The use of long and large bore, low resistance tubing (similar to a mask) resulted in the delivery of oxygen concentrations that tracked closely (accurate and precise) to values indicated by the entrainment device. The directly connected system with lower resistance (similar to a hood) produced a similar profile of concentrations and flow rates to the large bore tubing but with even greater accuracy. The use of a long and narrow tubing with higher resistance (similar to a cannula) did not deliver accurate oxygen concentrations. In fact, this high-resistance system failed to work as intended, and instead of entraining air, a large proportion (sometimes >50%) of the oxygen delivered to the entrainment device was ejected through its vents.

CONCLUSIONS

Entrainment devices can deliver accurate oxygen concentrations at low flow rates if used with low resistance delivery systems; however, entrainment devices are not suitable for use with high resistance delivery systems such as a standard nasal cannula.

Controlled FiO2 Therapy to Neonates by Oxygenhood in the Absence of Oxygen Analyzer

BACKGROUND

A study was conducted to evaluate a system of standardizing the oxygen concentration inside the oxygen hood and to develop guidelines for controlled FiO2 administration by changing size of the hood, lid position on the hood and the oxygen flow rate, without an oxygen analyzer. The effect of low flow rates on carbon dioxide (CO2) retention was also studied.

METHOD

A dummy patient and thirty neonates, requiring oxygen to be delivered through head box, constituted the material for the study group. Oxygen content in the head box was measured using a standard oxygen analyzer while the size of head box, flow rate and lid position were changed independently and in combination. The head boxes were tested on a dummy patient. These results were analyzed, and applied to thirty neonates requiring oxygen therapy using a head box.

RESULT

Volume of headbox had an inverse relation with the oxygen concentration inside the headbox and smaller sized headbox achieved more predictable oxygen concentration at all flow rates. Maximum difference in oxygen concentration by varying the lid position was seen in the large headbox. Keeping the variables constant, oxygen concentration was significantly lower in babies as compared to dummy. No significant CO2 retention was found at a flow rate of four litres per minute (lpm) in small and three lpm in a medium and large head box respectively, while lower flow rates were associated with CO2 retention.

CONCLUSION

It is possible to predict the oxygen concentration inside the head box without the use of oxygen analyzer. Larger head box and higher lid position, results in lower oxygen concentration, at a given oxygen flow rate. Oxygen concentration achieved in babies is lesser than the concentration achieved in a dummy. Flow rates of less than four lpm in small and three lpm in medium and large sized head boxes are associated with CO2 retention. These results are not applicable to infants weighing less than 2 kg.