online ML Comm Head and Neck Korean J Otorhinolaryngol-Head Neck Surg 2016;59(1):35-40 / pissn 2092-5859 / eissn 2092-6529 http://dx.doi.org/10.3342/kjorl-hns.2016.59.1.35 An Evaluation Protocol of the Upper Airway for Pediatric Patients with Stridor or Extubation Failure Jun Oh Park 1, Woori Park 1, Jungkyu Cho 1, Joongbum Cho 2, Jin Kyoung Kim 3, and Han-Sin Jeong 1 1 Departments of Otorhinolaryngology-Head and Neck Surgery, 2 Pediatrics, 3 Anesthesiology and Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea 기관삽관발거실패또는심한천명을호소하는호흡곤란소아환자에대한상기도평가프로토콜 박준오 1 박우리 1 조정규 1 조중범 2 김진경 3 정한신 1 성균관대학교의과대학삼성서울병원이비인후 - 두경부외과학교실, 1 소아청소년과학교실, 2 마취통증의학과학교실 3 Received April 14, 2015 Revised June 15, 2015 Accepted June 26, 2015 Address for correspondence Han-Sin Jeong, MD, PhD Department of Otorhinolaryngology- Head and Neck Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon-ro, Gangnam-gu, Seoul 06351, Korea Tel +82-2-3410-3579 Fax +82-2-3410-3879 E-mail hansin.jeong@gmail.com Background and ObjectivesZZAdequate evaluation of the upper airway is critical in the management of pediatric patients with stridor or extubation failure. For this purpose, we designed an evaluation protocol of the upper airway for these patients, in collaboration with Dept. of Pediatrics, Intensive care team and Anesthesiology. Here we present the clinical results of our evaluation protocol and provide information about the etiology and management of the upper airway problems. Subjects and MethodZZClinical data of 380 pediatric patients (M:F=231:149) having airway evaluation for their problems (stridor or extubation failure) were retrospectively analyzed. Among them, patients of age less than 3 months ranked first (30.0%). Comorbidities of pulmonary diseases (30.8%) and cardiovascular diseases (29.5%) were found. The pre and post-evaluation diagnosis, management and prognosis were evaluated and the usefulness of an airway evaluation protocol was discussed. ResultsZZFrequent pre-evaluation diagnoses were subglottic stenosis (55.2%), laryngomalacia (12.6%) and tracheal stenosis (9.2%) and these were changed to subglottic stenosis (44.5%), laryngomalacia (9.7%), tracheal stenosis (6.6%) and no abnormality (14.5%). Particularly, 50% of prediagnosis laryngomalacia, 25% of subglottic stenosis and 37% of tracheal stenosis were corrected to other causes by airway evaluation. The procedures were exam only (41.6%), endoscopic dilatation (20.8%) and tracheostomy (17.9%). In 190 out of 380 (50.0%), extubation was successful, but 151 patients (39.7%) had tracheostomy tube. ConclusionZZAdequate evaluation of the upper airway in pediatric patients with stridor or extubation failure can facilitate the diagnosis and management of their problems. Korean J Otorhinolaryngol-Head Neck Surg 2016;59(1):35-40 Key WordsZZEvaluation ㆍ Extubation failure ㆍ Pediatrics ㆍ Stridor ㆍ Upper airway. 서론 현대신생아학 (modern neonatology) 과소아중환자의학 (pediatric intensive care medicine) 의발전은전체신생아생존율을향상시켰고, 또한저체중아, 조산아, 미성숙신생아및선천성기형을가진환아의생존가능성을크게증가시켰다. 하지만이러한신생아들은상기도의구조적, 기능적이상으로 기관삽관 (intubation) 이필요한경우가많고이로인해발관에실패하거나발관후에천명음 (stridor) 을보이는경우가증가하고있다. 1-4) 천명음이란큰기도의좁아진부분을공기가통과하면서만드는빠른난기류로인해생성되는고음의소리이다. 선천적인후두천명음의가장흔한원인으로는후두연화증 (laryngomalacia) 이며, 천명음원인의 22~81% 정도를차지한다고알 Copyright 2016 Korean Society of Otorhinolaryngology-Head and Neck Surgery 35
Korean J Otorhinolaryngol-Head Neck Surg 2016;59(1):35-40 려져있다. 1,5,6) 이외에도양측성대마비또는기도연화증 (tracheomalacia) 등도중요한원인으로발표된바있다. 7,8) 선천적또는장기간의기관삽관후후천적성문하부협착 (subglottic stenosis) 이흔히발생할수있다. 윤상연골에의해둘러싸여있는성문하부는신생아에서직경이 5~7 mm 정도되는기관의가장좁은부위이다. 9,10) 성문하부의직경이 4 mm보다좁아지면성문하부협착증상이나타날수있는데, 성문하부는느슨한결합조직으로쌓여있기때문에염증이나외상에의해쉽게부종이생길수있다. 직경이 1 mm 좁아질때면적은 25% 가줄어들며 Poiseuille s 법칙에따르면기도저항은 16배로증가한다. 9) 장기간의기관삽관에의해발생한압력은성문하부점막의괴사를유발하고결과적으로발관 (extubation) 후에도성문하부협착을유발하게된다. 11-13) 위와같이다양한원인에의하여, 호흡시천명음을보이거나기관발관에실패하였을때상기도에대한적절한평가와이에근거한치료방법의선택은신생아및소아호흡기관리 (respiratory care) 에서매우중요한임상문제이다. 일반적으로환아가자발적호흡을하고있는동안굴곡형내시경을이용하여상기도를평가할수있으나, 14-16) 호흡부전 Evaluation protocol of the upper airway in pediatric patients A child with stridor or extubation failure (respiratory failure) 등의위험상황에대한충분한준비가필요하다. 이에본기관에서는자세변화로호전되지않는천명음을가진환아또는기관삽관제거가실패한환아에대하여, 소아기도 (airway) 전문이비인후과의사, 소아중환자의학전문의, 소아마취전문의로이루어진팀을통하여수술실에서전신마취하에상기도를평가하는프로토콜을디자인하였다 (Fig. 1). 본연구에서는천명이나발관실패로본상기도평가프로토콜에따라진단및치료를시행받은환아들의의무기록을분석하여본프로토콜의유용성을확인하고소아상기도문제의병인과예후를알아보고자하였다. 대상및방법 대상환자의선택 2005년 7월부터 2014 년 11월까지천명음을보이거나기관발관에실패하여본원에서만든상기도평가프로토콜에따라서상기도평가를시행한, 동반기저질환으로협조가어려운 18세이하환아를대상으로하였다. 수술전과후의진단명, 동반된신경계, 호흡기또는순환기질환의여부, 치료결과등에대해서후향적으로의무기록분석을시행하였다. 본후향적연구는연구시작이전에기관윤리심의위원회의승인을받았으며동의서는면제되었다. Preparation to general anesthesia in operation room, monitoring of V/S, consider difficult airway algorithm* in child with risk of cannot ventilate or intubate Intubation Controlled ventilation under general anesthesia (muscle relaxation) Intermittent apneic technique (intermittent extubation) Evaluation of structure abnormality from the oral cavity to bronchus Self-respiration under deep sedation (recovery of muscle relaxation) Evaluation of vocal fold movement/ laryngomalacia Discharge to Intensive care unit Decision making/ management of the problems Close post-operative monitoring Fig. 1. Evaluation protocol of the upper airway in symptomatic children with stridor. *Difficult airway algorithm: Practice guidelines for management of the difficult airwau: an updated report by the american society of anesthesiologists task force on management of the difflcult airway. Anesthesiology 2003;98(5):1269-77. 17) 상기도평가프로토콜상기도평가프로토콜은다음과같이 5단계로이루어져있다 (Fig. 1). 1) 자세변화에의하여호전되지않는천명을보이거나기관발관에실패한환아들에대해서수술장에서생체징후를감시하며전신마취하에기관삽관을먼저시행한다. 특히기계적환기나기관삽관이어려울것으로생각되는환아에있어서는미국마취과의사협회 (American Society of Anesthesiologists) 의기도확보알고리즘 (difficult airway algorithm) 을고려하였다. 17) 2) 다음, 전신마취하에서구강부터기도까지구조적문제가있는지기관튜브를빼고내시경 (d=2.7 or 4 mm, 0 endoscope, length=317 mm; Richard Wolf, Vernon Hills, IL, USA) 을이용하여평가한다 (apneic technique). 3) 이후깊은수면하에근이완제의효과를줄이면서자가호흡을회복시켜서성대의움직임 ( 성대마비여부 ) 과후두연화증여부를확인한다. 4) 이상의진단과정을통하여얻어진진단에대하여적절한조치 / 치료를결정하고시행한다. 36
An Airway Evaluation Protocol Park JO, et al. 5) 상기도평가후소아중환자실로퇴실하여일정기간지속 적인환자상태감시를시행한다. 후향적자료의분석 해당연구기간동안총 380 예의상기도평가가시행되었으 며, 평균연령은 2.6 세였고남아가 231 예, 여아가 149 예였다. 연 령분포를보면, 3 개월이하가 114 예 (30.0%), 3 개월에서 6 개월 사이가 35 예 (9.2%), 3~12 개월이 33 예 (8.7%), 1~2 세가 74 예 (19.5%), 3~5 세가 55 예 (14.5%), 5 세이상이 69 예 (18.2%) 였다. 동반된질환 ( 전체예의 58.6%) 으로는, 기관지폐이형성증 (dysplasia) 등의호흡기질환이동반된경우가 117 예 (30.8%), 동맥 관개존증등순환기질환이동반된경우가 112 예 (29.5%), 저 산소뇌손상이나뇌성마비등신경계질환이동반된경우가 50 예 (13.2%) 에서있었다. 각상기도평가에대하여평가전진 단, 평가후진단을비교하여상기도평가에의한진단의변화 를평가하였다. 또한, 수술후결과는환아의기도상태와예후를기준으로 평가하였다. 기도상태는수술후문제없이발관, 삽관유지 혹은발관후재삽관, 기관절개술시행또는유지로분류하였 고예후는지속적인병원치료, 퇴원, 전원, 사망, 재수술로분 류하였다. 진단 결 과 총 380 예를후향적으로분석한결과 23 가지의진단이내려 졌고빈도및중요성에따라 10 개로분류하였다. 수술전의심 되었던질환으로는성문하부협착이 210 예로가장많았고다 음으로후두연화증 (48 예 ), 기도협착 (35 예 ) 등의순서로나타 Table 1. Clinical diagnosis before airway evaluation n (%) Subglottic stenosis 210 (55.3) Laryngomalacia 48 (12.6) Tracheal stenosis 35 (9.2) Airway compression by mass 9 (2.4) Granulation 9 (2.4) Laryngeal cleft 7 (1.8) Vocal cord palsy 6 (1.6) Tracheomalacia 6 (1.6) Unknown* 6 (1.6) Laryngeal web 1 (0.3) Others 43 (11.3) Total 380 (100) *no specific etiology presumed, papilloma, adenotonsillar hypertrophy, foreign body, branchial cleft cyst 났다 (Table 1). 상기도평가후교정된진단명으로는성문하 부협착이 169 예로가장많았고다음으로특이소견이발견되 지않은경우가 55 예, 후두연화증 37 예, 기도협착 25 예순이 었으며, 육아종 (granulation), 성대마비, 종양에의한상기도 압박, 기도연화증, 후두열 (laryngeal cleft), 후두막증 (laryngeal web), 상기도유두종 (papilloma), 이물질, 아데노이드및 편도비대등이진단되었다 (Table 2). 또한, 28 예의경우에는 주요병인외에추가적인문제가발견되었다. 기도평가전의 심되었던질환이확인되거나환아의증상에가장영향을미 치는병인을주요병인으로정의하였고이외에발견된구조적 기능적상기도문제를추가적인병인으로간주하였다. 가장 흔한경우는성문하부협착, 기도협착이동반된경우였고후 두및기도연화증, 기타질환들이포함되었다. 상기도평가에의한진단의변경 대표적인병인에대하여상기도평가전의심되었던질환과 평가후의진단을비교해보면, 성문하부협착은의심되었던 210 예중 158 예에서성문하부협착으로확인되었고 21 예는 특이소견이없었으며 9 예는후두연화증, 5 예는육아종, 3 예 는기도협착, 2 예는각각성대마비, 성대막증, 1 예는기도연 화증으로진단이변경되었다. 후두연하증이의심되었던 48 예 Table 2. Final diagnosis through airway evaluation Total, n=380 n % Subglottic stenosis 169 44.8 Normal* 55 14.5 Laryngomalacia 37 9.7 Tracheal stenosis 25 6.6 Granulation 14 3.7 Vocal cord palsy 11 2.9 Tracheomalacia 7 1.8 Airway compression by mass 6 1.6 Laryngeal cleft 4 1.1 Laryngeal web 2 0.5 Others 50 13.2 Additional airway lesions (n=28, 7.4%) Subglottic stenosis 7 Tracheal stenosis 6 Laryngomalacia 3 Tracheomalacia 3 Glottic stenosis 3 Vocal cord palsy 2 Laryngeal web 2 Respiratory papilloma 2 Laryngeal web 2 *no specific etiology found, papilloma, adenotonsillar hypertrophy, foreign body, branchial cleft cyst www.jkorl.org 37
Korean J Otorhinolaryngol-Head Neck Surg 2016;59(1):35-40 Subglottic stenosis (n=210) Laryngomalacia (n=48) Tracheal stenosis (n=35) 중 25 예에서만후두연화증으로확인되었고, 기도협착은의 심되었던 35 예중 22 예가기도협착증으로진단되었다 (Fig. 2). 다시정리하면, 기도평가전성문하부협착이의심되었던경 우 24.8% 에서다른병인으로확인되었으며, 후두연화증진 단의 47.9%, 기도협착진단의 37.1% 가진단이변경되었다. 처치 Airway evaluation Correct diagnosis 75.2% Revised diagnosis 24.8% Correct diagnosis 52.1% Revised diagnosis 47.9% Correct diagnosis 62.9% Revised diagnosis 37.1% Subglottic stenosis (n=158) Normal (21) Laryngomalacia (9) Granulation (5) Tracheal stenosis (3) Vocal cord palsy (2) Laryngeal web (2) Tracheomalacia (1) Other (9) Laryngomalacia (n=25) Normal (16) Subglottic stenosis (5) Vocal cord palsy (2) Tracheal stenosis (n=22) Normal (4) Laryngomalacia (3) Subglottic stenosis (3) Tracheomalacia (2) Vocal cord palsy (1) Fig. 2. Change of diagnosis through airway evaluation. Table 3. Procedures during airway evaluation for causative etiologies of stridor or extubation failure n (%) Evaluation alone 158 (41.6) Endoscopic dilatation (Balloon or bouge) 79 (20.8) Tracheostomy or tracheo-stomaplasty 68 (17.9) Removal of granulation or shaving 56 (14.7) Open framework surgery 14 (3.7) Others* 5 (1.3) Total 380 (100) *adenotonsillectomy, mitomycin-c application, removal of foreign body 상기도평가과정에서검진만시행하고종료한경우가 158 예, 내시경하에서협착부위에대하여확장술을시행한경우 가 79 예 [ 풍선확장술 23 예, 부지 (bougie) 확장술 56 예 ], 기관 절개술및기관절개술관련처리가 68 예, 육아조직절제및 제거가 56 예에서행하여졌다. 기도평가후외부절개를별도 로시행한후후두골격수술시행한경우도 14 예에서있었으 Table 4. Outcomes and prognosis in pediatric patients with stridor or extubation failure, undergoing airway evaluation Outcomes of airway evaluation n % Successful extubation 190 50.0 Tracheostomy 151 39.7 Re-intubation with additional procedures 39 10.3 Prognosis of the subjects Successful discharge to home 259 68.2 Need additional procedures 66 17.4 Hospital care 47 12.4 Refer to other hospital 4 1.1 Death 4 1.1 며, 편도절제술혹은마이토마이신 -C 적용, 이물질제거등 의처치도 5 예에서시행되었다 (Table 3). 본상기도평가프로 토콜수행과정에서직접적인합병증발생또는사망의경우 는발견되지않았으며, 모든경우에서호전또는평가전의상 태로회복가능하였다. 상기도평가후의임상경과및예후 상기도평가후 190 예에서는발관후에정상적인호흡및 상기도기능을유지할수있었으나, 151 예에서는기관절개술 을시행하였다. 또한, 39 예에서는삽관을유지하거나발관후 재삽관 (re-intubation) 하였고 2 차적인시술을필요로하였다 (Table 4). 해당환아의예후를보면, 68.2% 에서퇴원이가능 하였으나, 약 30% 의환아에서는병원치료를지속하거나재 수술을시행하였다. 또한, 기저질환의악화로사망한경우도 4 예에서발견되었다. 고 찰 본연구는자세변화로호전되지않는천명이나발관실패 소아환자에대하여체계적이고안전한상기도평가프로토 콜을제시하고자하였으며, 단일기관에국한된제한적인경 험이지만소아상기도문제의병인과예후를알아보고자하였 다. 본연구결과, 주요병인으로는대부분의다른연구에서 빈도가가장높은것으로보고되었던후두연화증보다성문 하부협착이많은것이관찰되었다. 1,5,6,16,18) 이러한차이의원인 으로는최근신생아집중치료 (neonatal intensive care) 의발 전및본기관의경우 3 차의뢰기관이라는특수성을고려할 수있겠다. 신생아치료의발전은미숙아및조산아의생존가 능성을향상시켰고이에따라기관삽관과호흡기치료를하 는경우가증가하였다. 19,20) 따라서, 장기간의삽관또는선천적 인성문하부협착이증가하는경향을보이는것으로생각된 다. 또한, 본원의경우굴곡형내시경으로진단가능한후두 38
An Airway Evaluation Protocol Park JO, et al. 연화증과성문상부의병변은진단이확진되어의뢰가적은반면굴곡형내시경진단이어려운기타구조적이상이많이의뢰되는특성이있다. 21-23) 이외에도다른선천성기형이동반된환아의복합적치료를위하여의뢰되는경우역시많은편이었다. 6) 본연구결과에서알수있듯이다른호흡기, 순환기, 신경계동반질환을가진경우가대상환아의 60% 정도를차지하고있었다. 따라서, 이러한병원특성으로인하여본연구결과에서는성문하부협착이가장흔한원인으로관찰되었다고생각할수있겠다. 24) 또한동반질환으로인해상기도평가상구조적으로특이소견이없더라도기능적인문제 ( 윤상인두기능부전, 반복적인흡인, 성대이상운동등 ) 로호흡장애가발생하여기관발관에실패하는아이들이많은것으로생각된다. 이러한임상경험을바탕으로본기관에서는소아상기도평가프로토콜을디자인하였다 (Fig. 1). 기존의여러연구에서호흡곤란환아의일차평가로서굴곡형내시경검진을제안하고있으나, 25-28) 본소아상기도평가프로토콜의경우먼저기도확보알고리즘 (difficult airway algorithm) 에맞게기관삽관을통한기도확보를진행하였다. 17) 이러한이유로는앞에서제시한바와같이상기도의구조적이상이있는경우가흔하며, 굴곡형내시경검진시에드물지만발생가능한호흡부전 (respiratory failure) 을방지할수있기때문이다. 29) 그결과로본소아상기도평가프로토콜에따르는합병증발생을완전히피할수있었다. 일반적으로후두내시경 (flexible nasolaryngo-pharyngoscope) 을먼저사용하지만, 본대상환자의경우여러동반질환으로인하여기관삽관을필요로하는경우가많았기때문에, 후두내시경을일차적으로선택할수없는경우가많았다. 또한, 본원의뢰시이미기관삽관을가지고있었거나심한호흡곤란증상으로즉시기관삽관을한경우가많아서후두내시경을시행하기어려운경우가많았다. 또한추가로동반된상기도문제들이소아상기도의평가및처리를어렵게만들수있다. 16,30,31) 본연구에서도 28예에서주요병인외에추가적인문제가있었다. 가장흔한경우는성문하부및기도협착이동반된경우였으며, 이러한추가적인질환들은면역적, 신경학적으로미성숙한미숙아나만성적인문제로장기간치료받으면서추가적으로발생한경우가많았다. 이경우주요병인에대한적절한처치와더불어추가병인에대한치료를고려하여야할것이다. 32) 본기관에서디자인한소아상기도평가프로토콜은전체적으로약 30% 에서평가전진단을수정하였다. 평가전진단은대부분임상적추정에기초한진단이며소아과에서기관삽관을하면서관찰하거나환아의영상검사와임상적증상을고려하여추정한진단이어서, 전신마취하에정확한상기도평가로진단명이수정되는경우가많았다. 또한이전상기 도평가때진단된후에병의경과를위해추가시행하는경우 가있어진단되어있는경우가있었다. 특히주목할점은후두 연화증으로임상진단한경우약 50% 에서다른진단으로변 경된점이다. 즉, 후두상부만을관찰함으로써주요병인이되 는후두하부및기도의병변을간과할가능성이높은것으로 생각된다. 따라서, 임상증상의경과및변화를잘평가하여 다른질환이의심되거나상기도평가가필요한경우지체없 이소아상기도평가를시행하는것이진단및치료의지연을 방지할수있는방법이라고판단된다. 이외에도임상적성문 하부협착, 기도협착의경우소아상기도평가가없었다면약 20~30% 의잘못된진단가능성이있음을염두에두어야한 다. 요약하면, 적절한시기에소아상기도평가를진행하는것 은호흡곤란환아의진단과치료에서매우중요한역할을담 당한다고할수있겠다. 본소아상기도평가후질병의경과및예후는주로환아 의기저질환에좌우되는것으로보인다. 약반수에서는성공 적인기관튜브의발관을할수있었으나약 40% 에서는기관 절개술을시행할수밖에없었고, 70% 정도에서는퇴원가능 하였으나나머지는지속적인병원치료가필요하였다. 비록, 질 병의경과와예후는환아의기저질환에크게영향을받으나, 상기도문제에대한적시의진단, 처치를위하여본상기도평 가프로토콜은그임상적유용성을가지고있다고생각된다. REFERENCES 1) Zoumalan R, Maddalozzo J, Holinger LD. Etiology of stridor in infants. Ann Otol Rhinol Laryngol 2007;116(5):329-34. 2) Zalzal GH. Pediatric stridor and airway compromise. J Med Liban 1994;42(4):221-6. 3) Yee-Hang WB, Theresa H, So-Lun L, Wai-Kuen H, Ignace WW. Stridor in asian infants: assessment and treatment. ISRN Otolaryngol 2012;2012:915910. 4) Friedberg J. An approach to stridor in infants and children. J Otolaryngol 1987;16(4):203-6. 5) Levitan R, Ochroch EA. Airway management and direct laryngoscopy. A review and update. Crit Care Clin 2000;16(3):373-88, v. 6) Holinger LD. Etiology of stridor in the neonate, infant and child. Ann Otol Rhinol Laryngol 1980;89(5 Pt 1):397-400. 7) Berkowitz RG. Neonatal upper airway assessment by awake flexible laryngoscopy. Ann Otol Rhinol Laryngol 1998;107(1):75-80. 8) Altman KW, Wetmore RF, Marsh RR. Congenital airway abnormalities requiring tracheotomy: a profile of 56 patients and their diagnoses over a 9 year period. Int J Pediatr Otorhinolaryngol 1997;41(2):199-206. 9) Fearon B, Whalen JS. Tracheal dimensions in the living infant (preliminary report). Ann Otol Rhinol Laryngol 1967;76(5):965-74. 10) Benjamin B. Prolonged intubation injuries of the larynx: endoscopic diagnosis, classification, and treatment. Ann Otol Rhinol Laryngol Suppl 1993;160:1-15. 11) Duynstee ML, de Krijger RR, Monnier P, Verwoerd CD, Verwoerd- Verhoef HL. Subglottic stenosis after endolaryngeal intubation in infants and children: result of wound healing processes. Int J Pediatr Otorhinolaryngol 2002;62(1):1-9. 12) Gould SJ. The pathology of neonatal endotracheal intubation and its relationship to subglottic stenosis. J Laryngol Otol Suppl 1988;17:3-7. www.jkorl.org 39
Korean J Otorhinolaryngol-Head Neck Surg 2016;59(1):35-40 13) Hawkins DB. Pathogenesis of subglottic stenosis from endotracheal intubation. Ann Otol Rhinol Laryngol 1987;96(1 Pt 1):116-7. 14) Boudewyns A, Claes J, Van de Heyning P. Clinical practice: an approach to stridor in infants and children. Eur J Pediatr 2010;169(2): 135-41. 15) Moumoulidis I, Gray RF, Wilson T. Outpatient fibre-optic laryngoscopy for stridor in children and infants. Eur Arch Otorhinolaryngol 2005;262 (3):204-7. 16) Erdem E, Gokdemir Y, Unal F, Ersu R, Karadag B, Karakoc F. Flexible bronchoscopy as a valuable tool in the evaluation of infants with stridor. Eur Arch Otorhinolaryngol 2013;270(1):21-5. 17) American Society of Anesthesiologists Task Force on Management of the Difficult Airway. Practice guidelines for management of the difficult airway: an updated report by the American Society of Anesthesiologists Task Force on Management of the Difficult Airway. Anesthesiology 2003;98(5):1269-77. 18) Nussbaum E, Maggi JC. Laryngomalacia in children. Chest 1990;98 (4):942-4. 19) Bigelow AM, Gothard MD, Schwartz HP, Bigham MT. Intubation in pediatric/neonatal critical care transport: national performance. Prehosp Emerg Care 2015;19(3):351-7. 20) Noblett KE, Meibalane R. Respiratory care practitioners as primary providers of neonatal intubation in a community hospital: an analysis. Respir Care 1995;40(10):1063-7. 21) Woo HY, Yoo YS, Lee JY, Kim YM. Congenital epiglottic cysts. Korean J Otolaryngol-Head Neck Surg 1999;42(6):788-90. 22) Kim DE, Kim EH, Jung HR, Ahn BH. Two cases of congenital vallecular cyst with respiratory distress and feeding problems in young infant. Korean J Otolaryngol-Head Neck Surg 2011;54(9):646-9. 23) Park HM, Chung PS, Jang YJ, Kim JK. A case of laser microsurgical management in severe laryngomalacia. Korean J Otolaryngol-Head Neck Surg 1997;40(10):1467-70. 24) Denoyelle F, Garabedian EN, Roger G, Tashjian G. Laryngeal dyskinesia as a cause of stridor in infants. Arch Otolaryngol Head Neck Surg 1996;122(6):612-6. 25) Manna SS, Durward A, Moganasundram S, Tibby SM, Murdoch IA. Retrospective evaluation of a paediatric intensivist-led flexible bronchoscopy service. Intensive Care Med 2006;32(12):2026-33. 26) Gerritsen J. Flexible bronchoscopy in children: an open airway. Eur Respir J 2003;22(4):576-7. 27) Kuo CH, Niu CK, Yu HR, Chung MY, Hwang CF, Hwang KP. Applications of flexible bronchoscopy in infants with congenital vocal cord paralysis: a 12-year experience. Pediatr Neonatol 2008;49(5):183-8. 28) O Sullivan BP, Finger L, Zwerdling RG. Use of nasopharyngoscopy in the evaluation of children with noisy breathing. Chest 2004;125(4): 1265-9. 29) Chhajed PN, Glanville AR. Management of hypoxemia during flexible bronchoscopy. Clin Chest Med 2003;24(3):511-6. 30) Yuen HW, Tan HK, Balakrishnan A. Synchronous airway lesions and associated anomalies in children with laryngomalacia evaluated with rigid endoscopy. Int J Pediatr Otorhinolaryngol 2006;70(10): 1779-84. 31) Dickson JM, Richter GT, Meinzen-Derr J, Rutter MJ, Thompson DM. Secondary airway lesions in infants with laryngomalacia. Ann Otol Rhinol Laryngol 2009;118(1):37-43. 32) Song JJ, Lim YS, Kwon SK, Hah JH, Ahn SH, Sung MW, et al. Management of pediatric airway stenosis using cold instruments and mitomycin-c. Korean J Otolaryngol-Head Neck Surg 2004;47(11): 1164-8. 40