Napolitano Natalie, Nishisaki Akira, Buffman Hayley S, Leffelman Jessica, Maltese Matthew R, Nadkarni Vinay M
Respiratory Therapy Department
Division of Anesthesiology and Critical Care Medicine.
Respir Care. 2017 Jan;62(1):70-77. doi: 10.4187/respcare.04751. Epub 2016 Oct 25.
Partial pressure of end-tidal carbon dioxide (P ) monitoring in children is important to detect apnea or hypopnea early to intervene before hypoxemia develops. Monitoring P in children without a tracheal tube is challenging. To improve P measurement accuracy in a commercially available mask with a mainstream CO detector, we implemented design changes with deform-and-hold shaping technology and anterior-posterior adjustment of the expiratory gas flow cup.
Two sizes of redesigned face masks (small for 7-20 kg, medium for 10-40 kg) were evaluated. Initial bench testing used a simulator modeling a spontaneously breathing infant and child with a natural airway. An infant/child manikin head was connected to the breathing lung simulator. A mass flow controller provided expiratory CO. Mask fit was then evaluated on healthy human subjects to identify anatomical features associated with good fit, defined as square shape capnography waveform during expiration. A 3-dimensional digital scan was used to quantify anatomical features. The gaps between face mask rims and facial surface were manually measured.
Bench testing revealed a P difference of 3.4 ± 1.5 mm Hg between a measured P by the redesigned mask and CO concentration at trachea, as compared with 6.7 ± 6.2 mm Hg between P measured by nasal cannula and trachea (P < .001). In the human mask fit study, 35 children (13 ± 4 kg) with the small mask and 38 (24 ± 8 kg) with the medium mask were evaluated. Capnography tracing was successfully obtained in 86% of the small and 100% of the medium masks. In children with small-size masks, the gap between the face mask rim and the child's face was not statistically different among those with good mask fit and without (1.0 ± 1.5 mm vs 1.4 ± 1.9 mm, P = .73).
P measurement by a redesigned open-system face mask with a mainstream CO detector was accurate in the bench setting. The redesigned face mask can attain good mask fit and accurate capnography tracings in the majority of infants and children.
监测儿童呼气末二氧化碳分压（PetCO₂）对于早期发现呼吸暂停或呼吸浅慢以便在低氧血症发生前进行干预至关重要。在没有气管插管的儿童中监测PetCO₂具有挑战性。为了提高配备主流二氧化碳探测器的市售面罩的PetCO₂测量准确性，我们采用了变形并保持塑形技术以及呼气气流杯的前后调节进行设计改进。
对两种尺寸重新设计的面罩（7 - 20 kg儿童用小号，10 - 40 kg儿童用中号）进行评估。最初的台架测试使用模拟自然气道的自主呼吸婴儿和儿童的模拟器。将婴儿/儿童人体模型头部连接到呼吸肺模拟器。质量流量控制器提供呼气二氧化碳。然后在健康人体受试者上评估面罩贴合度，以确定与良好贴合度相关的解剖特征，良好贴合度定义为呼气期间方形二氧化碳波形图。使用三维数字扫描来量化解剖特征。手动测量面罩边缘与面部表面之间的间隙。
台架测试显示，重新设计的面罩测得的PetCO₂与气管处二氧化碳浓度之间的差值为3.4±1.5 mmHg，相比之下，鼻导管测得的PetCO₂与气管处之间的差值为6.7±6.2 mmHg（P <.001）。在人体面罩贴合度研究中，评估了35名使用小号面罩的儿童（13±4 kg）和38名使用中号面罩的儿童（24±8 kg）。小号面罩86%、中号面罩100%成功获得二氧化碳波形图。在使用小号面罩的儿童中，面罩贴合良好和贴合不佳的儿童之间，面罩边缘与儿童面部之间的间隙无统计学差异（1.0±1.5 mm对1.4±1.9 mm，P =.73）。
在台架设置中，配备主流二氧化碳探测器的重新设计的开放式面罩测量PetCO₂是准确的。重新设计的面罩在大多数婴儿和儿童中能够实现良好的面罩贴合度和准确的二氧化碳波形图。
