B超测量环状软骨水平气道横径对小儿加强型带套囊气管导管型号选择的预评估价值

目的比较B超测量环状软骨水平气道横径(minimal transverse diameter of the subglottic airway, MTDSA)法、年龄公式法和身高公式法对加强型带套囊气管导管型号选择的预判价值。方法选取睢宁县人民医院外科2021年1月—2021年12月择期手术行全麻气管插管患儿120例(排除失访及资料不全样本7例, 删失率5.83%), 按照分层随机区组的方式将研究样本分为年龄公式组(36例)、身高公式组(39例)和MTDSA组(38例)。气管导管选择加强型带套囊气管导管, 3组分别以年龄公式法、身高公式法和B超测量MTDSA法行气管导管型号预评估, 以插管成功最适气管导管型号为标准, 判定3种方法的预评估准确率;比较组间换管率, 插管后即刻MAP、心率, 并发症情况。结果 B超测量MTDSA法对首次气管导管型号评估的准确率为86.84%, 高于年龄公式法的55.56%、身高公式法的46.15%(P<0.05)。MTDSA组换管率为5.26%、换管例次率为10.53%, 均低于年龄公式组的33.33%、44.44%和身高公式组的43.59%、58....     

超声在阻塞性睡眠呼吸暂停综合征患儿气管插管中的应用

目的 探讨超声在阻塞性睡眠呼吸暂停综合征(OSAS)患儿气管插管时选择合适导管型号、插管成功率、围术期气道相关并发症中的应用效果。方法 选择择期全麻下行扁桃体和(或)腺样体切除术的OSAS患儿123例,男59例,女64例,年龄3～8岁,身高92～141 cm,体重16～39 kg, ASAⅠ或Ⅱ级,MallampatiⅠ或Ⅱ级。采用随机数字表法将患儿分为两组：超声组(n=62)和常规组(n=61)。超声组通过测量环状软骨内空气-黏膜界面直径来选择导管型号,听诊法和气管超声检查定位导管深度;常规组采用年龄公式确定气管导管型号,听诊法确定插管深度。记录插管深度、首次插管成功例数、插管时间和气管导管置换、气管导管脱出、支气管内插管、咳嗽声嘶、拔管后喘鸣等围术期气道相关并发症发生情况。结果 与常规组比较,超声组插管深度明显增加(P<0.05),首次插管成功率明显升高(P<0.05),插管时间明显延长(P<0.05),气管导管置换发生率明显降低(P<0.05)。两组气管套管脱出、支气管内插管、咳嗽声嘶和拔管后喘鸣发生率差异无统计学意义。结论OSAS患儿术中通过气管超声选择...     

超声引导与普通喉镜下气管插管的临床应用

目的 比较超声引导与普通喉镜下气管插管的临床应用,评估超声引导下实施气管插管的安全性及优缺点.方法 选择择期全麻下手术的患者70例,ASAⅠ或Ⅱ级,性别不限,年龄20～60岁,体重46～78 kg.随机分为超声引导组(U组,n=32)和普通喉镜组(L组,n=38).插管前Mallampati法评估气道分级.U组采用超声引导法,在长轴和短轴显示会厌、声门和环状软骨后,经口插入套有气管导管的换管器,超声引导下将换管器置入声门,然后经换管器插入气管导管;L组采用普通喉镜暴露声门,直视下插入气管导管.以胸部听诊法及PETCO2监测综合判断气管插管是否成功,两次试插不成功被认定为插管失败,改用可视喉镜引导气管插管.记录气管插管成功率、误入食管例数、口咽部黏膜出血及轻度声门水肿发生率;记录插管前、插管后即刻及插管后5 min的HR、SBP、DBP的变化.结果 与L组比较,U组插管后即刻HR明显减慢,SBP和DBP明显降低(P＜0.05);与插管前比较,两组插管后即刻HR明显增快,SBP和DBP明显升高(P＜0.05).插管后5min,两组患者HR、SBP和DBP差异无统计学意义.两组患者气管插管成功率、误入食管、口咽黏膜出血和轻度声门水肿发生率差异无统计学意义.结论 超声引导和普通喉镜下气管插管成功率无明显差异,但超声引导下气管插管可减少患者血流动力学波动和气管插管并发症.     

超声与CT测量声门至隆突气道解剖结构的一致性评价

目的评估超声测量声门至隆突气道解剖结构的准确性。方法 2019年1～4月选择我院90例颈椎手术,术前应用超声测量环甲膜、环状软骨、C7横突水平皮肤至气管内壁垂直距离及气管横径,并与CT测量的数值进行比较。结果超声与CT测量的环甲膜水平、环状软骨水平和C7水平3个层面气管横径的相关系数分别为0. 846(P=0. 000)、0. 801(P=0. 000)、0. 856(P=0. 000),3个层面皮肤至气管内壁垂直距离的相关系数分别为0. 964(P=0. 000)、0. 971(P=0. 000)、0. 985(P=0. 000)。Bland-Altman分析超声与CT测量的环甲膜水平、环状软骨水平和C7水平3个层面气管横径平均差异分别为-0. 53、-0. 18、-0. 42 mm,皮肤至气管内壁垂直距离平均差异分别为0. 49、0. 42、0. 74 mm。Bland-Altman图显示绝大多数散点在差值±1. 96SD线内均匀分布,且均值线接近0,表明这2种测量方法有较好的一致性。结论超声技术用于评估气管上段解剖结构,可较准确测量声门下皮肤至气管内壁垂直距离及气管横径。     

小儿应用Trachlight光索引导气管插管的临床观察

Trachlight(laerdal medical corporation,美国)是在传统光索基础上加以改进的新型光导气管插管工具,具有光亮度强、硬度适中的特点,特有的可移动管芯既能减少导管置入时的气道损伤,还能避免光索退出时将导管带出声门[1];同时还有三种不同型号可以适用于新生儿至成人.目前,有关成人应用Trachlight光索引导气管插管的研究较多[1,2],但小儿的报道较少.本观察探讨小儿应用Trachlight光索引导气管插管的临床效果.     

非先天性心脏病患儿气道环状软骨平面横径预测模型能否适用于先天性心脏病患儿

目的 评价基于非先天性心脏病患儿(children without congenital heart disease,NCHD)气管环状软骨平面横径值(transverse diameter of cricoid cartilage,CD)与年龄或体型所建立的直线回归方程,比较回归方程预测先天性心脏病患儿(children with congenital heart disease,CHD)环状软骨平面的气管横径值(cricoid diameter predicted by formula,CDfomula)和超声实测值(cricoid diameter measured by ultrasound,CDultra)的一致性.方法 纳入64名NCHD,镇静后测量CDultra,记录患儿年龄、身高、体重、BMI、体表面积等数据,采用逐步向前法与CD建立线性回归模型.纳入CHD 30例和NCHD 25例,比较两组患儿CD超声测量值与线性回归模型预测值的一致性.结果 NCHD的CD值与年龄呈正相关(r=0.90,P＜0.05),回归方程为CD(cm)=0.048×年龄(岁)+0.525.两组人群CDfomulaCDultra之间存在相关性(P＜0.05),NCHD组患儿CDfomula和CDultra的相关性为0.94,而CHD组患儿CDfomula和CDultra的相关性为0.71.NCHD组和CHD组CDultm和CDfomula的偏移值分别为-0.00 cm、-0.01 cm,95％一致性界限分别为(-0.06 cm,0.05 cm)和(-0.17 cm,0.15 cm),虽然两组患儿CDultra和CDfomula的偏移相近,但是CHD组患儿的界限值宽于NCHD组患儿.结论 在建立NCHD超声测量的CD值与年龄间线性回归方程的基础上,认为CHD模型预测和超声实测的一致性不如NCHD.因此在CHD气管插管时,测量CDultra可能会使气管导管的选择更加准确和便捷.     

小儿气管插管损伤的处理和预防

小儿气管插管的应用日益增多,其并发症也以■人的速度增加着。虽然许多危重患儿经长期呼吸支持获得挽救,但也有不少患儿继发威胁着生命的并发症—气管狭窄。如能取得早期诊断和处理是能防止此并发症的发生。作者认为小儿气管损伤的发病率之所以比成年人高的原因如下:1.小儿气管比成人小,更易因发生肉芽肿和疤痕而引起梗阻;2.成人及年长儿童声门是气管最窄处,而年幼儿童和幼儿最窄处是环状软骨环,如导管恰好通过声门,有可能紧嵌在环状部而产生压迫性坏死;3.年幼儿童较易患喉气管疾病,如气管导管通过发炎的气道或留置之,可迅速     

Discoscope内窥镜与GlideScope可视喉镜用于声门显露困难患者气管插管效果的比较

目的 比较Discoscope内窥镜与GlideScope可视喉镜用于声门显露困难患者气管插管的效果.方法 择期行经口气管插管的全麻患者40例,Macintosh喉镜显露Cormach-Lehane分级Ⅲ或Ⅳ级,性别不限,年龄24 ～ 78岁,采用随机数字表法,将患者随机分为2组(n=20):GlideScope可视喉镜组(G组)和Discoscope内窥镜组(D组).记录声门显露情况、声门显露时间、气管插管情况、声门显露后至气管导管置入时间和气管插管时间.术后随访患者,记录咽喉出血和咽喉疼痛的发生情况.结果 与G组比较,D组声门显露时间延长,环状软骨按压率降低,声门显露至气管导管置入时间缩短,1次气管插管成功率升高(P＜0.05),1次声门显露成功率、2次声门显露成功率、2次气管插管成功率、气管插管时间、咽喉出血发生率和咽喉疼痛发生率差异无统计学意义(P＞0.05).结论 与GlideScope可视喉镜比较,Discoscope内窥镜用于声门显露困难患者有助于声门的显露,且可提高气管插管的成功机率.     

超声在气道管理中的应用进展

超声在气道管理领域的研究不断取得的进展,为临床上将超声应用于气道管理提供了理论依据和新思路,拓宽了超声在气道管理方面的应用范围。超声能够实时显影和测量全气道的几乎所有组织结构,保证气道解剖结构的准确定位及测量,为气道评估提供客观的理论支持。超声可实时成像的特点有助于引导气管插管、确定气管导管及喉罩位置、评估胃内容量等。人工智能提高了超声识别解剖结构的准确率和效率,促进超声在气道管理的拓展应用。本文简述超声在实时引导气管插管、确定气管插管位置、确认喉罩准确对位、预测成功拔管、预测困难气道、定位气道解剖结构、评估胃内容物误吸风险等方面的应用进展,并讨论超声结合人工智能在气道管理领域的应用。     

Airtraq DL喉镜用于双腔气管导管插管的临床效果

目的 评价Airtraq DL喉镜用于双腔气管导管插管的临床效果.方法 选择拟行胸科手术单肺通气的患者30例.术前评估患者的气道情况.患者入室后常规麻醉诱导,插管前分别使用直接喉镜和Airtraq DL喉镜,按Cormack-Lehane分级评估声门暴露情况.记录使用AirtraqDL喉镜的插管次数、插管时间等.结果 与直接喉镜比较,Airtraq DL喉镜可以明显提高声门暴露程度(P＜0.01),有27例患者一次插管成功,平均插管时间为41(12～225)s.结论 Airtraq DL喉镜能够改善声门暴露程度并有效地用于双腔气管导管插管,因此可以作为双腔气管插管的新选择.     

Usefulness of ultrasound for selecting a correctly sized uncuffed tracheal tube for paediatric patients

The purpose of this study was to assess whether ultrasonography is useful for determining uncuffed tracheal tube sizes for paediatric patients. The equation for selecting the correctly sized tracheal tube was developed using data on the subglottic diameter measured by ultrasonography and air leak test. The efficacy of the new equation was evaluated by comparing it with the conventional age-based formula (4 + age/4) in another 100 patients. Tracheal tube sizes were selected using two methods, and air leakage pressure was measured after each intubation. The ultrasonographic method allowed the correct tube size to be selected in 60% of cases, whereas the age-based method enabled this in 31% of cases (p < 0.001). Ultrasound can offer a useful means of selecting correct tracheal tube size compared with the age-based formula in paediatric patients. However, even using ultrasound, the success rate of correct tube size selection is still not very high.     

Predicting the appropriate uncuffed endotracheal tube size for children: a radiograph-based formula versus two age-based formulas

Study ObjectivesTo determine whether a radiograph-based formula using the tracheal diameter from a chest radiograph predicted the appropriate endotracheal tube (ETT) size in children, and to compare these results with those produced using age-based formulas.DesignRetrospective, observational study.SettingMedical record review.MeasurementsData from 537 pediatric patients, aged 3 to 6 years, who underwent orotracheal intubation with an uncuffed ETT, were randomly divided into two datasets: one was used to derive a formula and the other was for validation. A radiograph-based formula was obtained by linear regression modeling between the tracheal diameter at the seventh cervical vertebra (C7) on chest radiography and the appropriate ETT size from the estimation dataset (n=268). The appropriate size was defined as the ETT size when air leak pressure was 10 to 30 cmH₂O. The predictive ability of this equation was evaluated using the validation dataset (n=269). The primary outcome was the success rate of the prediction.Main ResultsThe following radiograph-based formula was obtained: ID = 3 + 0.3 × (tracheal diameter at C7). The success rate of the radiograph-based formula was 57%, which is higher than the 32% (P < 0.001) of the standard age-based formula (ID = 4 + age/4) or 43% (P = 0.002) of Penlington's formula (ID = 4.5 + age/4). An underestimation of the actual tracheal size occurred in 65% of cases using the age-based formulas, but in only 19% with the radiograph-based formula (P < 0.001).ConclusionsThe radiograph-based formula may be useful for predicting the appropriate ETT size in children aged 3 to 6 years.     

Comparison of cuffed and uncuffed preformed oral pediatric tracheal tubes

BACKGROUND: In preformed cuffed tracheal tubes the position of the cuff within the airway is given by its distance to the tube bend placed at the lower teeth. The aim of this study was to compare the design of cuffed and uncuffed preformed pediatric oral tracheal tubes with regard to anatomical landmarks. METHODS: Complete series of cuffed and uncuffed preformed oral pediatric tracheal tubes sized from internal diameter 3.0-7.0 mm if available were ordered from five different manufacturers. The distance from the bend to the distal tube tip and to the upper border of the cuff were measured and compared with anatomical airway landmarks in the developing child. RESULTS: Between cuffed and uncuffed tracheal preformed tubes up to 37 mm differences in the bend-to-tracheal tube tip distances were found for given age groups. Thus uncuffed preformed tracheal tubes were more at risk for inadvertent endobronchial intubation than cuffed preformed tracheal tubes. Comparison of bend-to-upper border of the cuff distances with teeth-to-vocal cord distances calculated from anatomical data revealed that several of the tracheal tube cuffs become positioned within the subglottic larynx or even within the vocal cords when inserted according to the bend. CONCLUSIONS: There is a need for improvement in cuffed preformed pediatric tracheal tubes, namely a standard bend-to-tracheal tube tip distance to allow a safe insertion depth, a short cuff placed on the tube shaft as distally as possible and an intubation depth mark to verify a proper position of the cuff in the trachea.     

Using middle finger length to determine the internal diameter of uncuffed tracheal tubes in paediatrics

The selection of an appropriately‐sized tracheal tube is of critical importance in paediatric patients to reduce both the risk of subglottic stenosis from a tracheal tube that is too large, and inadequate ventilation or poor end‐tidal gas monitoring from a tracheal tube that is too small. Age formulae are widely used, but known to be unreliable, often resulting in a need to change the tracheal tube. Previous work has shown that the length of the middle finger and the internal diameter can both be used to guide depth of tracheal tube insertion. Therefore, we hypothesised that middle finger length may also be related to tube internal diameter. We enrolled children aged up to 12 years presenting to our institution for elective anaesthesia and measured the length of the middle finger on the palmar aspect of the hand. Anaesthetists chose the airway device they felt most appropriate for the procedure, and were unaware of the middle finger measurement. Of 160 patients who were enrolled, 108 were included in the final analysis. We found a linear relationship between uncuffed tracheal tube internal diameter and median middle finger length for each size of tracheal tube. Relationship between middle finger length and cuffed tracheal tube internal diameter was less clear. We propose that the formula: ‘middle finger length (cm) (round up to nearest 0.5) = internal diameter of uncuffed tracheal tube (mm)’ may be an improvement compared with age formulae for selecting uncuffed tracheal tubes in children, although this requires formal testing.     

Laryngeal damage due to an unexpectedly large and inappropriately designed cuffed pediatric tracheal tube in a 13-month-old child

PURPOSE: To present a case of laryngeal damage in an infant caused by a too large and inappropriately designed cuffed tracheal tube. CLINICAL FEATURES: A 13-month-old child undergoing cardiac surgery was intubated with an uncuffed endotracheal tube with an internal diameter (ID) of 4.0 mm. Because of an important air leak around the tracheal tube during mechanical ventilation, a cuffed endotracheal tube ID 4.0 mm was inserted. The air leak with the tube cuff not inflated was acceptable at 25 cm H2O airway pressure. After extubation on the third postoperative day, the patient showed increasing stridor and respiratory deterioration. Fibreoptic laryngoscopy of the spontaneously breathing patient showed a large intra-laryngeal web. After surgical removal of the web, the child rapidly recovered and was discharged from the hospital on the 12th postoperative day. Inspection of the 4.0 mm (ID) cuffed tracheal tube revealed a cuff positioned inappropriately high and an increase of 0.7 mm in outer tube diameter compared to the 4.0 mm (ID) uncuffed tracheal tube from the same manufacturer. The tube cuff is likely to be situated within the larynx when placed in accordance to insertion depth formulas or radiological criteria, as used for uncuffed tracheal tubes in children. CONCLUSION: The larger than expected tracheal tube with its intra-laryngeal cuff position in a 13-month-old child likely caused mucosal damage and an inflammatory reaction within the larynx resulting in granulation tissue formation and fibrous healing around the tracheal tube.     

Endotrachealtuben bei Kindern

Background

Estimating the endotracheal tube size with the optimal internal diameter (ID) is of outstanding importance for airway management in pediatric patients. For many years different weight, height, and/or age-based formulas have been published. The aim of the present study was to identify and to compare published formulas to estimate optimal tube size in pediatric patients.

Materials and methods

A PubMed search was performed to identify published formulas for tube diameter in pediatric patients. The keywords ??pediatric?? or ??paediatric??, ??anesthesia?? or ??anaesthesia??, ??anaesthesiology?? or ??anesthesiology??, ??size??, ??formula??, ??diameter??, ??tube?? or ??endotracheal tube?? were used. Analysis was limited to articles published between 01.01.1951 and 30.06.2009. Additionally, similar publications retrieved from PubMed (related articles) and cited references were identified. Publications and formulas were assessed and classified by two independent colleagues.

Results

In the specified time-frame, 13 publications (11 original contributions and 2 letters to the editor) were identified with PubMed and 3 more formulas with the extended search. Altogether 22 formulas to estimate appropriate endotracheal tube size for pediatric patients (age 0?C18 years) were identified: 12 age-based formulas for tubes without a cuff, 4 height-based formulas for tubes without a cuff, 2 weight-based formulas for tubes without a cuff and one multivariate formula for tubes without a cuff as well as 3 age-based formulas for cuffed endotracheal tubes.

Conclusions

The identified formulas were comparatively simple to apply but were validated only for pediatric patients older than 1 year. Using tubes with a cuff can minimize the problem of optimal tube size. If a tube without a cuff is intended to be used other sizes should also be available.     

Intubation depth markings allow an improved positioning of endotracheal tubes in children

OBJECTIVES: To evaluate the position of the new Microcuff pediatric tracheal tube, based upon intubation depth markings. METHODS: With Institutional Ethics Committee approval and informed parental consent, we included patients from birth (> or = 3 kg) to 16 yr undergoing interventional cardiac catheterization requiring general anesthesia with orotracheal intubation. The intubation depth mark of the tracheal tube was placed between the vocal cords by direct laryngoscopy. The distance between tube tip and tracheal carina was measured from routinely taken cardiac catheterization posterior-anterior x-ray computer images with the patient supine and the head in a neutral position. Evaluation was performed for 20 tubes size 3.0 mm internal diameter (ID) and for ten tubes of each size from 3.5 to 7.0 mm ID. RESULTS: 100 patients were studied (47 girls; 53 boys). Tracheal tube tip advancement into the trachea ranged from 40.6% to 68.6% (median 51.4%). The shortest distance from tube tip to the tracheal carina was 15.7 mm using a 3.0 mm ID tube. Using a standard formula for tube insertion in children aged > or = two years [12 cm + (age/2)], in one patient the tube tip would have been below the carina and in seven patients the tube cuffs would have been placed within the larynx. CONCLUSIONS: The intubation depth markings of the new Microcuff pediatric tracheal tube allow safe placement of the tracheal tube with a cuff-free laryngeal zone without the risk for endobronchial intubation. Placement using the intubation depth markings was superior to predicted insertion using a standard formula.     

A weight-based formula for tracheal tube size in children

Objective:  Age (in years) of the child has conventionally been used in formulae to estimate the tracheal tube (TT) size. The objective of this retrospective study was to test a weight-based formula (WBF) for uncuffed oral TT in children and compare it with the conventional age-based formula (ABF).
Methods:  The patient's age, weight, and size of TT internal diameter (ID) were recorded. For comparative analysis, the actual TT size used was compared with predicted TT size, calculated using both the standard ABF [ID = age (years)/4 + 4 mm] and the WBF [ID = weight (kg)/10 + 3.5 mm].
Results:  The Pearson's correlation coefficient for age and actual TT size used was 0.77 (95% CI: 0.74–0.80) and between weight and actual TT used was 0.70 (95% CI: 0.66–0.74). The ABF correctly predicted 51.3% of TT sizes while the WBF correctly predicted 44.8% of TT sizes ( P  = 0.01). The measures of agreement between the actual and predicted TT size were 0.35 and 0.27 for the ABF and WBF respectively. The difference between the percentages of paired predictions for the ABF and WBF was statistically significant ( P  < 0.001) suggesting that, when correctly predicting the actual tube size used, the WBF functions for a different subset of the patient cohort than the ABF.
Conclusions:  This study suggests that in this patient cohort, the WBF is statistically inferior to the conventional ABF. However, our findings also suggest that the WBF may correctly predict TT sizes in a subset of patients in whom the ABF is inaccurate.     

Role of ultrasound compared to age‐related formulas for uncuffed endotracheal intubation in a pediatric population

Background: It is often difficult to determine the correct size of endotracheal tubes (ETT) needed for intubating pediatric patients. Therefore, we evaluated the role of ultrasound in pediatric patients to compare the correct size of an uncuffed (ETT) with the minimal transverse diameter of the subglottic airway (MTDSA) measured by ultrasound and with tube size predicted by different age‐related formulas. Methods: A total of 50 pediatric patients ≤5 years were enrolled. As a standard, we defined the adequate ETT size with no audible leakage below a ventilation pressure of 15 mbar and with an audible leakage above 25 mbar. The maximum allowed difference between the prediction method result and the ETT that fit was defined as 0.3 mm. Ultrasound was performed before the intubation procedure; the intubating anesthesiologists were blinded to the results of the ultrasound measurement. Agreement between the two age‐based formulas most commonly used at our department and MTDSA with the correct ETT size (standard) was analyzed using a Bland–Altman plot. Correlation and regression analyses were performed and the numbers of correct intubation trials recorded. Results: The frequency of bias ≤0.3 mm between each method and the correct ETT in the first attempt was <50% and the mean number of reintubations 1.6 ± 1.3. In contrast to age‐related formulas, however, the ultrasonographically determined MTDSA was not significantly different from the correct ETT. MTDSA was highly associated with the outer diameter of the ETT (r = 0.869, R² = 0.754). Conclusions: Measuring MTDSA by ultrasound facilitates selection of the appropriate ETT in pediatric patients and may reduce the number of reintubations.     

Comparison of Cuffed and Uncuffed Endotracheal Tubes in Young Children during General Anesthesia

Background: Uncuffed endotracheal tubes are routinely used in young children. This study tests a formula for selecting appropriately sized cuffed endotracheal tubes and compares the use of cuffed versus uncuffed endotracheal tubes for patients whose lungs are mechanically ventilated during anesthesia.

Methods: Full-term newborns and children (n = 488) through 8 yr of age who required general anesthesia and tracheal intubation were assigned randomly to receive either a cuffed tube sized by a new formula [size(mm internal diameter) = (age/4) + 3], or an uncuffed tube sized by the modified Cole's formula [size(mm internal diameter) = (age/4) + 4]. The number of intubations required to achieve an appropriately sized tube, the need to use more than 21 [center dot] min sup -1 fresh gas flow, the concentration of nitrous oxide in the operating room, and the incidence of croup were compared.

Results: Cuffed tubes selected by our formula were appropriate for 99% of patients. Uncuffed tubes selected by Cole's formula were appropriate for 77% of patients (P < 0.001). The lungs of patients with cuffed tubes were adequately ventilated with 2 1 [center dot] min sup -1 fresh gas flow, whereas 11% of those with uncuffed tubes needed greater fresh gas flow (P < 0.001). Ambient nitrous oxide concentration exceeded 25 parts per million in 37% of cases with uncuffed tubes and in 0% of cases with cuffed tubes (P < 0.001). Three patients in each group were treated for croup symptoms (1.2% cuffed; 1.3% uncuffed).