The Science Journal of the American Association for Respiratory Care

2005 OPEN FORUM Abstracts

SIMPLE AND RELIABLE REGULATION OF BUBBLE CPAP USING 100% HUMIDIFIED GAS AT BODY TEMPERATURE (VAPOTHERM) AS THE GAS SOURCE.



Harris C. Jacobs, MD and Louis DeMichiel, RRT, Departments of Pediatrics and Respiratory Medicine, Yale Univ. School of Med, and Bridgeport Hospital, Bridgeport, CT 06525

Background: Gregory introduced bubble CPAP over 30 years ago as a means of providing respiratory support to infants with respiratory distress. Other methods of delivery have been introduced including the use of a "CPAP setting" on standard mechanical ventilators. Delivery of CPAP by submerging the expiratory limb of the ventilator circuit in 0.25% acetic acid (bubble CPAP) has been argued to be the preferred method because the rapid bubbling produces an oscillatory effect. The problem with bubble CPAP is lack of a reliable means of locking the tube at the desired depth in the 0.25% acetic acid. We have devised a simple and reliable device to solve this problem and combined it with a commercial method of delivering 100% humidified gas at body temperature, which has the advantage of being less irritating to the nasal mucosa.

Method
: The device we designed consists of a collar and venting pathway fixed to a bottle top. A central tube fits loosely through the collar and locks in place at any of several preset points via protrusions on the side of the central tube and slots in the collar. The expiratory limb of the ventilator tubing connects to the central tube. The bottle is filled with 0.25% acetic acid to a preset level. CPAP is adjusted by locking the central tube at the necessary level (Figure). We modified the Vapotherm system to connect to standard Hudson CPAP prongs. Flow was set at 8 liters per minute and FIO2 was adjusted based on oxygen saturation. This system was used for a continuous 3 hour period on a 3 week old former 700 gram infant born at 25 weeks gestation who was already on CPAP.

Results
: The CPAP pressure remained at the set point of 5 cm H2O for the entire observation period. Oxygen requirements before during and after the observation period were unchanged (25%-30%) as were oxygen saturations. Similarly, PCO2 and pH before, during and after the observation period were unchanged (50 to 52 mm Hg for the PCO2 and 7.25 for the pH). No distress was noted during the observation period.

Conclusion
: We have devised a safe, simple and reliable method of delivering bubble CPAP that can be combined with a source of 100% humidified gas providing all of the advantages of both. (This protocol was approved by the IRB at Bridgeport Hospital.)

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