Efficiency of the Carden "Ventmasta" in A and D modes during controlled ventilation in children.
We have determined the efficiencies of the enclosed Mapleson A and Mapleson D modes of the Carden "Ventmasta" ventilator during controlled ventilation in 19 anaesthetized children. In addition, we determined the suitability for the A mode of the fresh gas formula, VF = 0.6 x weight0.5. Efficiency was assessed in terms of the fraction of fresh gas delivered to the alveoli. When the minute volume to fresh gas flow ratio exceeded 1.5, fractional delivery of fresh gas was 23% greater in the A mode than in the D mode (0.74 vs 0.60) (P < 0.0001). Under the same conditions, mean end-tidal carbon dioxide concentration in 27 children undergoing ventilation in the A mode with VF = 0.6 x weight0.5 was 4.6% (range 3.5-5.4%). We conclude that the Carden system is up to 23% more efficient in the A mode than in the D mode, and that under the conditions of this study, normocapnia or mild hypocapnia was produced accurately using the formula VF = 0.6 x weight0.5.
Barrie
J R
JR
University Department of Anaesthesia, Withington Hospital, Manchester.
Meakin
G
G
Campbell
I T
IT
Beatty
P C
PC
Healy
T E
TE
D000293:Adolescent; D000768:Anesthesia, General; D001835:Body Weight / Q000502:physiology; D002245:Carbon Dioxide / Q000502:physiology; D002648:Child; D002675:Child, Preschool; D017558:Elective Surgical Procedures; D006801:Humans; D007223:Infant; D010372:Pediatrics / Q000295:instrumentation*; D012121:Respiration, Artificial / Q000379:methods; D012122:Ventilators, Mechanical
D002245:Carbon Dioxide