氣管插管是臨床呼吸道處理相當重要的技術。根據統計，美國每年有800萬的病患接受氣管插管的處置。應用傳統硬式喉頭鏡進行挑管是臨床上施行氣管插管最常用的技術。然而由於傳統硬式喉頭鏡構造上的限制，困難插管與其相關併發症(如:牙齒傷害)一直是臨床上威脅病患安全的重要議題。在美國，困難插管是麻醉死亡的主要原因，而其導致的醫療糾紛之賠償金額平均每件高達424,000美元。此外，插管所導致的牙齒傷害更是麻醉醫師最主要的醫療糾紛來源(佔全部醫療糾紛的29%)。本研究的目的為設計與發展新式阻力回饋型喉頭鏡以改善目前臨床插管所面對的問題。

本研究分成兩階段進行。第一階段的研究為設計與發展新式阻力回饋型喉頭鏡。透過生物力學分析、人因工程、與電腦輔助設計之應用，阻力回饋型喉頭鏡的基本設計包含一個阻力回饋把手、一個關節葉片、與一組阻力回饋傳動機構。接下來透過有限元素挑管模擬分析以決定其最佳化之設計，並比較最佳化設計之阻力回饋型喉頭鏡相對於傳統Macintosh 喉頭鏡之挑管表現。最後透過金屬加工製造新式阻力回饋型喉頭鏡之原型。第二階段的研究為探討新式阻力回饋型喉頭鏡應用於插管的可行性。新式阻力回饋型喉頭鏡首先由五位經驗豐富之插管者在假人上，進行其使用之最佳喉頭視野、喉頭鏡旋轉程度、與插管所需時間之功能性評估。接下來透過40位不同經驗之插管者比較阻力回饋型喉頭鏡與傳統Macintosh喉頭鏡在插管效果與效益之差異，包含:最佳喉頭視野、牙齒傷害風險、插管時間、成功率、與滿意度/效益度，以評估其應用於臨床插管的可行性。其中由有經驗插管者進行兩種喉頭鏡插管效果之評估比較，而由無經驗插管者比較兩種喉頭鏡應用於插管之效益。此階段的實驗在插管假人身上進行。統計上使用paired-t test，Wilcoxon signed-rank test及McNemar’s test進行資料分析比較(p < 0.05)。

阻力回饋型喉頭鏡最佳化設計之有限元素分析結果顯示:在40N的握力驅動下，喉頭位移量隨著前端葉片長度從10 mm ~ 30 mm的增長而逐漸增加，但是隨著前端葉片長度從30 mm ~ 50 mm的增長而逐漸減少; 而作用於喉頭的應力則是隨著前端葉片長度從10 mm ~ 50 mm的增長而逐漸減少。由於30mm的前端葉片長度可產生13.6mm的最大喉頭位移與1.53MPa的中等應力，因此被決定為阻力回饋型喉頭鏡之最佳前端葉片長度。另外，最佳化設計之阻力回饋型喉頭鏡相對於Macintosh 喉頭鏡的挑管表現之有限元素分析結果顯示:新式阻力回饋型喉頭鏡比傳統Macintosh 喉頭鏡有更好的挑管效果。最後最佳化設計之阻力回饋型喉頭鏡原型即根據有限元素模擬分析之結果製造完成。

新式阻力回饋型喉頭鏡原型之功能性評估結果顯示:相較於傳統Macintosh喉頭鏡，新式阻力回饋型喉頭鏡能達到更好的喉頭視野(grade 1 laryngeal view: 5/5 vs. 3/5)、較少的葉片旋轉(2.2 + 1.5 degree vs. 13.4 + 3.4 degree; p < 0.05)、與相似的插管時間(30 + 8 sec vs. 33.4 + 2.4; p = 0.389)。由有經驗插管者所進行的插管效果評估結果發現:阻力回饋型喉頭鏡在喉頭視野(grade 1 laryngeal view: 18/20 vs. 13/20; p < 0.05)、把手旋轉(3.9 + 2.2 degree vs. 12.4 + 4.8 degree; p < 0.05)、牙齒壓迫(1.3 mm vs. 3.5 mm; p < 0.05)、挑管所需時間(1.9 + 0.4 sec vs. 2.5 + 0.4 sec; p < 0.05)與滿意度(5 vs. 3.5; p < 0.05)上都優於傳統Macintosh喉頭鏡。由無經驗插管者所進行之插管效益評估結果顯示:阻力回饋型喉頭鏡比傳統Macintosh喉頭鏡能提供更好的喉頭視野(grade 1 laryngeal view: 12/20 vs. 4/20; p < 0.05)、較少的把手旋轉(4.1 + 1.8 degree vs. 13.8 + 4.7 degree; p < 0.05)與牙齒壓迫(0.8 mm vs. 4.3 mm; p < 0.05)、較短的挑管時間(2.0 + 0.4 sec vs. 2.5 + 0.5 sec; p < 0.05)、以及較高的成功率(90% vs. 60%; p < 0.05)與效益度(4 vs. 3; p < 0.05)。而不論插管者的經驗豐富與否，兩種喉頭鏡應用於氣管插管，對於喉頭鏡放置所需時間、氣管內管放置所需時間、與插管全程所需時間都無顯著影響。

不論插管者的經驗如何，使用阻力回饋型喉頭鏡應用於氣管插管都比使用傳統Macintosh喉頭鏡有更佳的效果表現。而無經驗的插管者使用阻力回饋型喉頭鏡更有較高的插管成功率。本研究的結論為新式阻力回饋型喉頭鏡可有效的提升挑管效率與改善插管問題，因此有潛力成為未來臨床插管的新選擇。

Tracheal intubation (TI) is a critical technique in clinical airway management. It is estimated that TI is performed on 8 million patients per year in the United States. In clinical practice, TI is commonly conducted through direct laryngoscopy with conventional rigid laryngoscopes. Because of the structure limitation of conventional rigid laryngoscopes, difficult TI and complications associated with TI, such as dental trauma, continue to be a major issue of patient safety since 1985. In the U.S., difficult and failed TI is the major cause of anesthesia-related death, and its resulting claims payment is $424,000 per patient in average. Furthermore, dental damage related to TI is the adverse event responsible for majority of malpractice claims against anesthesiologists (29% of all cases). The purpose of this research was to design and develop a novel resistance feedback laryngoscope (RFL) to improve the efficacy of TI in clinical practice.

This research was divided into two stages. Stage I was aimed to design and develop a novel RFL. The RFL consisting of a resistance feedback handle and an articulating blade with a biofeedback mechanism connected to the handle was designed through biomechanical analysis, ergonomics, and computer-aided design. Optimal design of the RFL and performance of the optimally designed RFL relative to the Macintosh laryngoscope on laryngoscopy were investigated through finite element analysis on a laryngoscopy simulation model. A prototype of the RFL was then manufactured through machining process. Stage II was to investigate the feasibility of the novel RFL on laryngoscopic TI. The functional performance of the RFL prototype on TI was evaluated by five expert nurse anesthetists to investigate the best laryngeal view, levering movement, and intubation time on a manikin. The effect and usefulness of the RFL on TI was then investigated by 40 laryngoscopists with different levels of experience to comparatively evaluate the differences of the novel RFL and conventional Macintosh laryngoscope on the best laryngeal view, risk of dental trauma, intubation time, success rate, and satisfaction/usefulness score. The effect of the RFL relative to the Macintosh laryngoscope on TI was evaluated by experienced laryngoscopists, while the usefulness of the RFL relative to the Macintosh laryngoscope on TI was evaluated by inexperienced laryngoscopists. An intubation manikin with normal-appearing airway was used to conduct the study. Paired-t test, Wilcoxon signed-rank test, and McNemar’s test were used for data analysis with p < 0.05 for statistical significance.

The results of finite element analysis for optimal design of the RFL reveal that under the 40 N trigger force, laryngeal displacement is gradually increasing from the 10 mm to 30 mm levering tip lengths but is reversely decreasing from the 30 mm to 50 mm levering tip lengths; the von Mises stress is gradually decreasing from the 10 mm to 50 mm levering tip lengths. As the 30 mm levering tip length generates the greatest laryngeal displacement of 13.6 mm with a median stress of 1.53 MPa among the nine levering tip lengths, it is referred to as the optimal levering tip length of the RFL. The results of finite element analysis for the performance of the optimally designed RFL relative to the Macintosh laryngoscope reveal that the novel RFL with trigger force could generate greater laryngeal displacement than the conventional Macintosh laryngoscope with either lifting force or levering force. Based on the analytical results of finite element analysis, the novel RFL prototype has been completely designed.

The results of RFL prototype performance on TI show that the novel RFL improves laryngeal exposure (grade 1 laryngeal view: 5/5 vs. 3/5), significantly reduces levering movement (2.2 + 1.5 degree vs. 13.4 + 3.4 degree; p < 0.05), and has similar intubation time (30 + 8 sec vs. 33.4 + 2.4; p = 0.389) compared with the conventional Macintosh laryngoscope. The results of the study conducted by experienced laryngoscopists demonstrate that the effects of TI using the RFL are better than those using the Macintosh laryngoscope on the best laryngeal view (grade 1 laryngeal view: 18/20 vs. 13/20; p < 0.05), handle rotation (3.9 + 2.2 degree vs. 12.4 + 4.8 degree; p < 0.05), dental compression (1.3 mm vs. 3.5 mm; p < 0.05), lifting time (1.9 + 0.4 sec vs. 2.5 + 0.4 sec; p < 0.05), and satisfaction score (5 vs. 3.5; p < 0.05). The results of the study conducted by inexperienced laryngoscopists reveal that the RFL is more useful than the Macintosh laryngoscope on the best laryngeal view (grade 1 laryngeal view: 12/20 vs. 4/20; p < 0.05), handle rotation (4.1 + 1.8 degree vs. 13.8 + 4.7 degree; p < 0.05), dental compression (0.8 mm vs. 4.3 mm; p < 0.05), lifting time (2.0 + 0.4 sec vs. 2.5 + 0.5 sec; p < 0.05), success rate (90% vs. 60%; p < 0.05), and usefulness score (4 vs. 3; p < 0.05). There are no differences in the insertion time, intubation time, and overall time between the use of the RFL and Macintosh laryngoscope on TI for either the experienced or inexperienced laryngoscopists.

When the novel RFL is used to perform laryngoscopic TI on a manikin by laryngoscopists with different levels of experience, it is more effective and useful than the conventional Macintosh laryngoscope. The RFL also improves the success rate of TI for inexperienced laryngoscopists. It is concluded that the novel RFL is effective in improving the problems of TI and may be a viable option for application in clinical TI.

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