Klein Ulrich, Bucklin Brenda A, Poulton Thomas J, Bozinov Daniel
Department of Pediatric Dentistry, The Children's Hospital, Denver, Colorado, USA.
Pediatr Dent. 2004 Sep-Oct;26(5):410-6.
Nitrous oxide (N2O) administration with nasal mask produces variable outcomes in dental patients. This study describes a novel sampling method to measure actual inspired/expired N2O concentrations ([N2O]).
Fifteen adult volunteers (32.5 +/- 8.5 years) underwent placement of a nasopharyngeal probe. With a nasal mask, 100% oxygen (O2) was administered for 2 minutes. N2O was introduced incrementally every 2 minutes for a final flowmeter [N2O] of 50% and subsequently decreased in the same manner. Anesthesia gas monitors analyzed inspired/expired [N2O], [O2], and PETCO2 from the nasopharynx and end-inspired/expired [N2O] in the mask. Data were measured every 20 seconds and analyzed. Inspired/expired nasopharyngeal and nasal mask [N2O] and [O2] were expressed as the median value at each time point for all subjects and plotted against flowmeter settings.
Average inspired nasal mask [N2O] was 31% lower than flowmeter settings and decreased by another 19% on the way to the nasopharyngeal sampling site. During the phase of increasing N2O, average expired nasopharyngeal [N2O] was 22% lower than inspired [N2O]. When N2O was decreased, the effect was reversed and average expired [N2O] was 18% higher than inspired. Expired [N2O] was on average 51% lower than flowmeter settings. Mean PETCO2 was 39.7 +/- 1.4 mm Hg.
Nasopharyngeal end-expired [N2O] varied markedly from flowmeter settings. Correlation of PETCO2 with expected physiologic values validates sampling methodology. This method allows accurate, continuous, and actual measurements of inhaled/exhaled gases in awake patients as well as decision-making/analysis of effectiveness of mask type to determine average [N2O] during administration by nasal mask.
牙科患者使用鼻罩给予氧化亚氮（N₂O）会产生不同的结果。本研究描述了一种新颖的采样方法，用于测量实际吸入/呼出的N₂O浓度（[N₂O]）。
15名成年志愿者（32.5±8.5岁）接受了鼻咽探头的放置。使用鼻罩，给予100%氧气（O₂）2分钟。每2分钟递增引入N₂O，最终流量计的[N₂O]为50%，随后以相同方式降低。麻醉气体监测仪分析来自鼻咽的吸入/呼出[N₂O]、[O₂]和呼气末二氧化碳分压（PETCO₂）以及面罩内吸气末/呼气末[N₂O]。每20秒测量一次数据并进行分析。所有受试者在每个时间点的吸入/呼出鼻咽和鼻罩[N₂O]及[O₂]均以中位数表示，并针对流量计设置进行绘制。
平均吸入鼻罩[N₂O]比流量计设置低31%，在到达鼻咽采样部位的过程中又降低了19%。在N₂O增加阶段，平均呼出鼻咽[N₂O]比吸入[N₂O]低22%。当N₂O降低时，效果相反，平均呼出[N₂O]比吸入高18%。呼出[N₂O]平均比流量计设置低51%。平均PETCO₂为39.7±1.4毫米汞柱。
鼻咽呼气末[N₂O]与流量计设置有显著差异。PETCO₂与预期生理值的相关性验证了采样方法。该方法能够准确、连续且实际地测量清醒患者吸入/呼出的气体，以及对鼻罩类型的有效性进行决策/分析，以确定鼻罩给药期间的平均[N₂O]。
