Bliss Peter L, McCoy Robert W, Adams Alexander B
Department of Pulmonary/Critical Care Medicine, Regions Hospital, St Paul, Minnesota, USA.
Respir Care. 2004 Feb;49(2):160-5.
Demand oxygen delivery systems (DODS) allot oxygen by interrupting the oxygen flow during exhalation, when it would mostly be wasted. Because DODS conserve oxygen by various methods, there are important performance differences between DODS. We studied certain performance factors that have not previously been carefully examined.
A bench model was constructed to simulate a nose, airway, and alveolar chamber. A breathing simulator generated 4 respiratory patterns, at frequencies of 15, 20, 25, and 30 breaths/min. Eighteen models of DODS were tested at 4 settings, each up to the maximum output, and compared to continuous-flow oxygen. The variable of interest was the fraction of inspired oxygen (F(I)O(2)) in the alveolar chamber, which was measured for each condition.
The DODS differed from continuous-flow oxygen, delivering 0.5-2.1 times (mean = 1.13 times) the F(I)O(2) increase at similar settings. During maximum output the DODS showed a wide range of F(I)O(2), from 0.27 to 0.46. There was a direct relationship between volume output per pulse in the first 0.6 s of inhalation and the delivered F(I)O(2).
DODS settings were not equivalent to continuous-flow oxygen in a bench model assessment; with equivalent settings the DODS tended to deliver greater F(I)O(2) than did continuous-flow oxygen. The maximum output capacity differed markedly among the DODS, and the user should know the device's capacity. A volume-referenced setting system for DODS should be adopted that would allow more predictable oxygen prescription and delivery via DODS.
按需给氧系统（DODS）通过在呼气期间中断氧流来分配氧气，因为此时氧气大多会被浪费。由于DODS通过各种方法节约氧气，所以不同的DODS在性能上存在重要差异。我们研究了一些此前未被仔细研究过的性能因素。
构建了一个模拟鼻子、气道和肺泡腔的实验台模型。一个呼吸模拟器以每分钟15、20、25和30次呼吸的频率产生4种呼吸模式。对18种DODS模型在4种设置下进行测试，每种设置均达到最大输出，并与连续流氧气进行比较。感兴趣的变量是肺泡腔内的吸入氧分数（F(I)O(2)），针对每种情况进行测量。
DODS与连续流氧气不同，在相似设置下，其F(I)O(2)增加量为连续流氧气的0.5 - 2.1倍（平均为1.13倍）。在最大输出时，DODS的F(I)O(2)范围很广，从0.27到0.46。吸气开始的0.6秒内每个脉冲的输出量与输送的F(I)O(2)之间存在直接关系。
在实验台模型评估中，DODS的设置与连续流氧气不等同；在同等设置下，DODS输送的F(I)O(2)往往比连续流氧气更高。不同DODS的最大输出能力差异显著，用户应了解设备的能力。应采用一种基于体积的DODS设置系统，以便通过DODS实现更可预测的氧气处方和输送。
