The author studied the adequate flow rate of fresh gas to Jackson-Rees circuit to obtain normal arterial carbon dioxide tension (Pa
co2) in clinical pediatric anesthesia. The problem, whether the controlled respiration with large tidal volume and low respiratory rate was appropriate or not, was investigated with blood gas study and also hemodynamicaly in clinical cases and adult mongrel dogs. The following results were obtained.
1. In children aged from 3 months to 5 years old, 220 ml/kg/min of fresh gas flow to Jackson-Rees circuit showed invariably more normal Pa
co2 than the cases with 31/min of fresh gas flow.
2. In the similar cases, the controlled respiration with large tidal volume (20 ml/kg) and low respiratory rate (20/min) showed more normal Pa
co2 and higher arterial oxygen tension than those with smaller tidal volume (10 ml/kg) and high respiratory rate (40/min) .
3. In the dogs, the controlled respiration with large tidal volume and low respiratory rate showed larger alveolar ventilation, larger fall of mean arterial pressure, smaller rise of pulmonary arterial pressure and smaller increase of cardiac output than those with small tidal volume and high respiratory rate.
From above results, the author concluded that 220 ml/kg/min of fresh gas flow to Jackson-Rees circuit was sufficient to guarantee the adequate CO
2 washout from the body, and the controlled respiration with large tidal volume and low respiratory rate was satisfactory from the viewpoint of gas exchange and hemodynamics.
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