A clinical determination of optimal fresh gas flow in a baby EAR circuit.
OBJECTIVE
Baby EAR circuit is a new modified enclosed afferent reservoir anesthetic breathing system for pediatric patients. By following His Majesty the King of Thailand's self-sufficiency philosophy, the circuit is simple and made of low-cost and easy-to-find materials found in the operating room. This present study was to investigate clinical use of the circuit and to find the optimal fresh gas flow in clinical setting.


METHODS
A prospective descriptive study was conducted in pediatric patients, weighed 5-20 kg, anesthetized for surgery. The Baby EAR breathing circuit was used for general anesthesia with endotracheal tube and control ventilation. Different fresh gas flow of 3, 2.5, 2 and 1.5 liter per minute (LPM) was used consecutively. The authors recorded end-tidal carbon dioxide (EtCO2) and mean inspiratory carbon dioxide (ImCO2) while using fresh gas flow at 3, 2.5, 2, and 1.5 LPM. EtCO2 of 35-45 mmHg and ImCO2 of < 6 mmHg were considered clinically acceptable.


RESULTS
Fifty patients were enrolled. Mean value (95% CI) of EtCO2 at fresh gas flow rate of 1.5, 2, 2.5, and 3 LPM were 39.6 (39.2, 40.9), 36.7 (35.5, 37.8), 35.4 (34.3, 36.4), and 35.4 (34.3, 36.4) mmHg respectively. Mean value (95% CI) of ImCO2 at fresh gas flow rate of 1.5, 2, 2.5, and 3 LPM were 4.0 (3.0, 4.9), 2.4 (1.7, 3.0), 1.8 (0.9, 2.6), and 1.3 (0.9, 1.7) mmHg respectively. Percentage of patients (95% CI) who had clinically acceptable EtCO2 and ImCO2 at fresh gas flow rate of 1.5, 2, 2.5, and 3 LPM were 70% (56.2, 80.9), 92% (81.2, 96.8), 98% (89.5, 99.6), and 100% (92.9, 100) respectively. No patients had serious complications.


CONCLUSIONS
Baby EAR circuit can be made economically and used safely for general anesthesia with control ventilation in pediatric patients weighing 5 to 20 kg at optimal fresh gas flow of 3 LPM.
Theerapongpakdee
Sunchai
S
Department of Anesthesiology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand. Sunchai@kku.ac.th
Phanpanusit
Thanyathorn
T
Horatanaruang
Duenpen
D
Bunsangjaroen
Piyaporn
P
Limpkulwathanaporn
Prapapan
P
Thananun
Maneerut
M
Nonlhaopol
Duangthida
D
D000764:Anesthesia, Closed-Circuit / Q000295:instrumentation*; D000768:Anesthesia, General; D001835:Body Weight; D002245:Carbon Dioxide / Q000097:blood; D002648:Child; D002675:Child, Preschool; D004867:Equipment Design; D005260:Female; D006784:Hospitals, Teaching; D006801:Humans; D007442:Intubation, Intratracheal; D007530:Isoflurane / Q000008:administration & dosage; D008297:Male; D009609:Nitrous Oxide / Q000008:administration & dosage; D010100:Oxygen / Q000008:administration & dosage; D011446:Prospective Studies; D012121:Respiration, Artificial / Q000295:instrumentation*; D013785:Thailand; D013990:Tidal Volume; D012122:Ventilators, Mechanical
D002245:Carbon Dioxide; D007530:Isoflurane; D009609:Nitrous Oxide; D010100:Oxygen