[Risk of accumulation of CO2 in the oxygen chamber in "HOOD" (Experimental study on test bed)]. / Risque d'accumulation du CO2 lors de l'oxygénothérapie sous enceinte « HOOD ¼ (Étude expérimentale sur banc d'essai).

ABSTRACT

OBJECTIVES: Oxygen hood is largely used to deliver O2 to newborn infants with respiratory failure in the northern region of France. The oxygen flow is set to obtain the target arterial blood oxygen saturation. Thus, O2 flow delivers into the hood may be below the recommended gas flow of 6L/min. However, gas flow below 6L/min exposes to CO2 rebreathing. The aim of this study was to evaluate the effect of various rates of gas flows on the values of partial pressure of CO2 into the hood. MATERIAL AND METHODS: We measured CO2 and O2 partial pressure into hoods of two different volumes (4 and 10L) under two experimental bench test conditions. Protocol 1 gas flow was constant at 6L/min, while oxygen fraction varied from 0.21 to 1. Partial pressure of CO2 and O2 were recorded. Protocol 2 while O2 fraction was kept constant, oxygen flow varied from 0.5 to 7L/min (by step of 0.5L/min). Partial pressure of CO2 and O2 were recorded. RESULTS: Partial pressure of CO2 increases proportionally to the decrease in the gas flow delivered into the hood, and reached 14 mmHg at gas flow of 0.5L/min. CONCLUSION: Risk of CO2 rebreathing exists as soon as the gas is delivered into the hood at minimal flow rates below 6L/min.