The Science Journal of the American Association for Respiratory Care

2000 OPEN FORUM Abstracts

UTILIZING HELIOX TO IMPROVE CARBON DIOXIDE ELIMINATION DURING HIGH FREQUENCY OSCILLATORY VENTILATION IN A PEDIATRIC PATIENT

Jeffery Attwood RRT, Ndidiamaka Musa MD, Department of Pediatric Critical Care, Clarian Health Partners, Indianapolis, Indiana

Introduction: HFOV is being used successfully in the neonatal patient population and is finding favor as an alternative mode of ventilation for the pediatric patient. A consequence of using HFOV, especially on larger patients, is the inability to adequately purge carbon dioxide. Studies have shown that breathing a helium-oxygen mixture (Heliox) can improve ventilation and increase the removal of carbon dioxide. This case report demonstrates the successful use of Heliox to reduce the PaCO2 of a pediatric patient being ventilated using a SensorMedics 3100A high frequency oscillator.
Case Study: A 7 year old with a history of sickle cell anemia was admitted for an acute onset of chest pain and shortness of breath. Over the next 48 hours his respiratory status continued to deteriorate and ultimately he was intubated and placed on pressure regulated volume control, Vt=400ml, f = 20, FiO2 0.60 and Peep=10, PIP = 40+cmH2O. His pulmonary condition continued to worsen despite increases in FiO2, rate, and Peep. PIP was 60+cmH2O. CXR showed no evidence of pneumothorax or mis-positioned ET tube. Patient was placed on HFOV, MAP=30, Delta P=58, FiO2 0.60, frequency 4 Hz, and Insp. Time 35%. Oxygenation improved allowing the FiO2 and MAP to be decreased, however PCO2 remained high (70 -- 90 mmHg) despite adjustments to Delta P, frequency, and Insp. Time. Conventional ventilation was restarted but again PO2 decreased and patient was placed back on HFOV. It was decided to trial HFOV with Heliox in an attempt to lower PCO2. A cylinder containing 79% Helium / 21% Oxygen was connected to the medical air hose of the HFOV blender. Later this set-up was modified to include a secondary blender powered by medical air and Heliox, which delivered a controlled concentration of Heliox to the oscillator blender. Increasing the secondary blender percentage increased the Heliox delivery. The following chart illustrates a sample of ABG's obtained before and during the 24 hours of Heliox therapy.

Arterial Blood Gas pH PCO2 PO2 HCO-3 Oscillator Blender Secondary Blender
Pre Heliox 7.31 77 91 39 40% -
Heliox - 15 minutes 7.64 30 43 33 40% -
Heliox - 30 minutes 7.56 36 63 33 60% -
Off Heliox - 1 hour 7.23 93 100 39 60% -
Heliox - 30 minutes 7.37 69 81 41 50% 60%
Heliox - 8 hours 7.50 42 69 36 50% 75%
Heliox - 22 hours 7.54 45 84 39 40% 70%

Patient was removed from Heliox and HFOV and placed on conventional ventilation without difficulties. He was extubated after 6 days, and discharged 2 weeks later.
Discussion: Heliox delivered with HFOV was able to drastically lower the PaCO2 and produced no serious effects on machine function. More research is required to determine which patients might benefit from this therapy, and to perfect the Heliox delivery system.

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