O'Hagan M, Reid E, Tarnow-Mordi W O
Department of Child Health, University of Dundee, Ninewells Hospital and Medical School, UK.
Crit Care Med. 1991 Nov;19(11):1370-3. doi: 10.1097/00003246-199111000-00012.
To investigate: a) the relationship between humidifier temperature and inspired gas humidity and b) the effect of insulating the inspiratory tube on "rainout" (condensate).
Observational study.
Regional neonatal unit in a university hospital.
Forty-eight infants receiving assisted ventilation, of whom 31 infants were nursed in incubators and 17 under radiant heaters.
Despite always maintaining humidifier temperature greater than 34.7 degrees C, inspired gas humidity decreased below the American National Standards Institution minimum of 30 mg H2O/L on 35 of 479 occasions. At a humidifier temperature of 36 degrees C, inspired gas humidity varied between 17 and 43 mg H2O/L. In incubators set at a temperature of 34.1 +/- 1.3 (SD) degrees C, inspired gas humidity was linearly related to humidifier temperature, but with wide scatter (p less than .001, r2 = .28). In cooler incubators set at 32.9 +/- 1.8 degrees C, inspired gas humidity varied inversely with humidifier temperature. This variation was attributed to condensate due to inspired gas cooling within the incubator. Insulation of the inspiratory tubing reduced condensate by only 15%.
Inspired gas humidity cannot be predicted reliably from humidifier temperature. Accurate control will require a new generation of humidifiers that measure inspired gas humidity.
研究：a）加湿器温度与吸入气体湿度之间的关系；b）对吸气管进行绝缘处理对“雨水形成”（冷凝水）的影响。
观察性研究。
一所大学医院的地区新生儿病房。
48名接受辅助通气的婴儿，其中31名婴儿在暖箱中护理，17名在辐射加热器下护理。
尽管始终将加湿器温度维持在高于34.7摄氏度，但在479次测量中有35次吸入气体湿度降至低于美国国家标准机构规定的最低值30毫克H2O/升。在加湿器温度为36摄氏度时，吸入气体湿度在17至43毫克H2O/升之间变化。在温度设定为34.1±1.3（标准差）摄氏度的暖箱中，吸入气体湿度与加湿器温度呈线性相关，但离散度较大（p<0.001，r2 = 0.28）。在温度设定为32.9±1.8摄氏度的较冷暖箱中，吸入气体湿度与加湿器温度呈反比。这种变化归因于暖箱内吸入气体冷却导致的冷凝水。吸气管的绝缘处理仅使冷凝水减少了15%。
无法根据加湿器温度可靠地预测吸入气体湿度。精确控制将需要新一代能够测量吸入气体湿度的加湿器。
