Evaluation of cuffed tracheal tube size predicted using the Khine formula in children

BACKGROUND: The correct size of cuffed endotracheal tube (CET) limits the risk of postintubation tracheal damage. The aim of this study was to compare the size of the CET used in children with the size predicted by the Khine formula [age (years)/4 + 3]. METHODS: After ethical committee approval, 204 children aged 1 day-15 years were included prospectively in the study. The choice of the size of the CET was made at the discretion of the attending anesthesiologist. The main criterion of judgment was the comparison of the leak before and after inflating the cuff at a pressure of 20 cm.H(2)O. Demographic data, tracheal tube size used and that predicted by Khine's formulae and side-effects were recorded. RESULTS: Overall, 21% of the CET were in accordance with the size predicted by the Khine formula. In the remaining patients, 72% were oversized and 7% undersized. In 12 cases, the size of CET chosen initially was modified: for a larger size in eight children and for a smaller size in four others. Six children (2.9%) presented with minor postoperative complications. CONCLUSIONS: Our data suggest that Khine's formula for predicting the appropriate tracheal tube size underestimates optimal size by 0.5 mm. We therefore recommend the use of the following formula: internal diameter of the CET = [age/4 + 3.5] in children >1 year of age which may be applied without increased risk of complications. The rate of tracheal reintubation as well as the detected leaks supports these recommendations.     

Cuff compliance of pediatric and adult cuffed tracheal tubes: an experimental study

BACKGROUND: Tracheal mucosal damage related to tracheal intubation has been widely described in pediatric and adult patients. High volume-low pressure cuffs (HVLPC) are being advertised as safe to avoid this particularly unpleasant complication. Compliances of these supposed pediatric and adult HVLPC are not mentioned by manufacturers and still remain unknown. METHODS: The compliance of HVLPC was measured in vitro and defined as the straight portion of the pressure-volume curve. Cuff pressure was measured after incremental 0.1 ml filling volumes of air for sizes 3.0-8.0 of internal diameter of Rüsch and Mallinckrodt tracheal tubes. Compliances were assessed in air and in a rigid tube. The filling volume to achieve a 25-mmHg intracuff pressure was also measured. RESULTS: In air, each 0.1 ml step almost linearly increased cuff pressure by 1 mmHg (size 8.0) to 9 mmHg (size 3). In air, the volume needed to maintain a cuff pressure < 25 mmHg was small for sizes 3-5.5 (0.35-2 ml). The 25 mmHg inflated cuff volume and compliance were decreased within a rigid tube, especially for adult sizes. In a rigid tube simulating a trachea, the compliances of almost every Rüsch tracheal tube were statistically higher than those of the Mallinckrodt. CONCLUSION: We conclude that the tested tracheal tube cuffs have low compliance and cannot be defined as high volume-low pressure.     

Performance characteristics of a novel reusable intermediate–volume low–pressure cuffed endotracheal tube

Study objective: To evaluate the performance of the reusable intermediate–volume low–pressure cuffed “Super Safety Yellow” (Willy Rüsch AG, P. O. Box 1620, D–71332 Waiblingen, Germany) endotracheal tube with regard to cuff seal, tube tip position, and incidence of postoperative throat complaints. The “Super Safety Yellow” was compared with the “Super Safety Clear” (W. Rusch AG), the “lo–pro” (Mallinckrodt Laboratories, Cornamady, Athlone County, Ireland), and the “red rubber” (W. Rüsch AG) tubes. Methods: Two hundred adult patients scheduled for minor surgery under standardized general anaesthesia were allocated to one of these tubes. Past–cuff leakage (indicator: orally instilled 0.2% indigocarmine) as well as intratracheal tube tip position (degree of being centred) were assessed by fibre–optic tracheoscopy. The semi–standardized interviews for the recording of postoperative sore throat were performed in double–blind fashion once a day, starting on the day of operation till p.o. day 3. Statistics: x ²–test; significance: P < 0.05. Main Results: A past–cuff leakage was found in three “red rubber” tubes. There were significant differences in tube tip position with the “Super Safety Clear” being best, and the “Super Safety Yellow” being worst centred (P = 0.010). The incidence of postoperative throat complaints showed a nonsignificant tendency in favour of the PVC–tubes. A significant number of such complaints were observed in women (P = 0.0004) and in obese patients (P = 0.011). By contrast, this incidence did not significantly differ with age, tracheal cross–sectional shape, tube tip position, use of atropine, and duration of intubation. Conclusion: Although resembling the “red rubber” tube in the incidence of postoperative throat complaints, the “Super Safety Yellow” may be an alternative to the currently used disposable tubes in anaesthesia. Its performance is comparable with regard to cuff seal and intra–cuff pressure. Additionally, it helps in reducing PVC waste and may lessen costs.     

Postal survey of cuffed or uncuffed tracheal tubes used for paediatric tracheal intubation

A postal survey of the use of cuffed or uncuffed tracheal tubes for tracheal intubation in children and infants was performed to investigate the criteria used for deciding the choice of tube and the manner of inflating the cuff in the case of use of a cuffed tracheal tube (CTT). From 200 questionnaires despatched, replies were received from 130 paediatric anaesthesiologists (response rate 65%). In paediatric practice, the CTT was routinely used by 25% of respondents for more than 80% of their patients, while more than 37% of respondents use them in less than 20% of the cases. The three main criteria used for inflating a cuff were: (i) the presence of a leak, (ii) the type of surgery associated with the presence of a leak and (iii) the patient's age associated with the type of surgery and the presence of a leak. These criteria were specified, respectively, by 32%, 24% and 18% of the respondents. The cuff was inflated in response to a leak in 18% of the cases and as a response to a pressure manometer in 15% of the cases. Few paediatric anaesthesiologists use a cuffed tracheal tube routinely for tracheal intubation in children, and fewer actually use a pressure monitoring device, while it is suggested that the cuff pressure should be monitored in case of CTT.     

Tracheal sealing characteristics of pediatric cuffed tracheal tubes

BACKGROUND: The aim of the study was to compare sealing characteristics of the new Microcuff pediatric tracheal tube featuring a high volume-low pressure (HVLP) cuff with ultrathin membrane with three conventional pediatric cuffed tracheal tubes. METHODS: After obtaining approval of the local ethical committee, 80 children aged 2-4 years were tracheally intubated with the following tubes (i.d. 4.0 mm) in random order: Microcuff P-HVLP, Mallinckrodt Hi-Contour P, Rüschelit Super Safety Clear, and Sheridan CF. Cuff pressure to prevent air leakage at standardized ventilator setting (PIP 20 cm H2O/PEEP 5 cm H2O/RR 20 min(-1)) was assessed within 5 min after intubation by auscultation of audible sounds at the mouth. Cuff pressures required with each group were compared with Kruskall-Wallis test (P < 0.05). Values are median and range. RESULTS: No significant differences in patient characteristics were found between the four groups. The Microcuff tube required significantly lower sealing pressures [11 cm H2O (6-26)] compared with the other tracheal tube brands [Mallinckrodt: 36 cm H2O (18-48); Rüschelit: 21 cm H2O (8-46); Sheridan: 26 cm H2O (18-60), (P < 0.0001)]. CONCLUSION: This preliminary investigation suggests that the new Microcuff pediatric tracheal tube with ultrathin high volume-low pressure cuff membrane allows effective tracheal sealing at very low cuff pressures. This represents a benefit for children with regard to their lower mucosal perfusion pressures compared with adult patients.     

Sizes and depths of endotracheal tubes for cleft lip and palate children undergoing primary cheiloplasty and palatoplasty

Background:  Appropriate sizes (internal diameters) and insertion depths of uncuffed preformed endotracheal tubes in children with cleft lip and palate, who generally have delayed growth and development in early infancy have not been elucidated.
Methods:  The sizes and insertion depths of endotracheal tubes in patients who received primary cheiloplasty and/or palatoplasty in relation to age, height, and weight were retrospectively analyzed. Tube sizes were determined using an appropriate air leakage at an airway pressure of 15–20 cmH₂O. Tube insertion depths were confirmed by auscultation of bilateral breathing sounds at several tube depths, placing the tip 1.5 cm above the carina. Obtained data sets were compared with previously published studies.
Results:  The number of cases analyzed was 236 in total. The mean age, height, and weight were 327.4 ± 199.2 days, 69.7 ± 7.5 cm, and 8.2 ± 1.8 kg, respectively (mean ±  sd ). Neither the tube size nor tube depth in cleft lip and palate children was smaller or shorter than those of normal subjects. Discrepancies between the preformed bend and the tube insertion depth increased as the tube size increased.
Conclusions:  The current findings suggest that it is reasonable to apply the currently available standards for normal children, e.g. Motoyama's general guide, to predict the tube size and insertion depth for Japanese cleft lip and palate children, and that the use of the uncuffed preformed endotracheal tube is associated with a risk of endobronchial intubation, which appears to increase with age.     

Performance of a novel pressure release valve for cuff pressure control in pediatric tracheal tubes

BACKGROUND: Acute and chronic hyperinflation of tracheal tube cuffs represents a persistent risk factor for airway damage in children when cuffed tracheal tubes are used. In order to overcome this particular risk, a cuff pressure (CP) pop-off valve has been designed to avoid CP exceeding 20 cmH(2)O. METHODS: The performance of the novel pop-off valve has been evaluated in an in vitro set-up during slow and rapid air insufflation by a syringe or a CP manometer or inadvertent compression of the cuff pilot balloon while measuring cuff and tracheal wall pressure (WP) in ID 3.0 mm cuffed tracheal tubes. Steady-state performance was evaluated during nitrous oxide exposure of tracheal tube cuffs (ID 3.0 mm). RESULTS: The novel CP pop-off valve avoided cuff hyperinflation during rapid air volume changes and showed reliable performance during steady-state nitrous oxide exposure to the tube cuff. CONCLUSIONS: These preliminary results show that the CP pop-off valve limits the effect of rapid, potentially dangerous manual cuff inflation maneuvers and reliably prevents CP exceeding the predetermined level of 20 cmH(2)O when exposed to nitrous oxide.     

A pressure regulator for the cuff of a tracheal tube

A regulator is described for the maintenance of a constant pressure difference above airway pressure during positive pressure ventilation in a cuffed tracheal tube. It comprises a tubular threshold valve which is powered by the anaesthetic gas supply source to a breathing system. The valve is interposed between the anaesthetic gas supply machine and the breathing system creating a pressure differential. The upstream pressure is transmitted to the pilot tube supplying the cuff of a tracheal tube via an upstream connection. The valve is suitable only for breathing systems that require a constant gas supply. The regulator was evaluated during anaesthesia, using a modified Mallinkrodt Hi-Lo jet ventilation tube to obtain simultaneous pressure measurements within the cuff and the lumen of the tracheal tube. A greater pressure was demonstrated in the cuff than in the airway and the two traces were approximately parallel throughout the respiratory cycle. The device should prevent excessive cuff inflation pressure and solves the problem of forgetting to let the cuff down before extubation.     

Predictors of postoperative sore throat in intubated children

Background: The incidence of postoperative sore throat (POST) following intubation is not well defined in the pediatric population. The etiology is multifactorial and includes impairment of subglottic mucosal perfusion and edema as a result of the pressures exerted by cuffed or uncuffed tubes. Aim: To determine the incidence of, and risk factors for, POST in intubated children undergoing elective day‐case surgery. Methods: Five hundred patients aged 3–16 years were studied prospectively. Endotracheal tube (ETT) choice (cuffed or uncuffed) was left to the anesthetist. The cuff was inflated either until loss of audible leak or to a determined pressure using a cuff manometer. The research team then measured the cuff pressure (CP). POST incidence and intensity was determined by interviewing patients prior to discharge from the same day procedure unit. Chi‐square testing and stepwise logistic regression were used to determine the predictors of POST. Results: Of the 111 (22%) children developed a sore throat, 19 (3.8%) a sore neck, and 5 (1%) a sore jaw. 19% of patients with cuffed ETTs complained of sore throat compared with 37% of those intubated with an uncuffed ETT. The incidence of POST increased with CP; 0–10% at 0 cmH₂O, 4% at 11–20 cmH₂O, 20% at 21–30 cmH₂O, 68% at CP 31–40 cmH₂O, and 96% at CP >40 cmH₂O. The ETT CP and use of uncuffed ETTs were univariate predictors of POST. Conclusions: Children intubated with uncuffed ETTs are more likely to have POST. ETT CP is positively correlated with the incidence of POST. When using cuffed ETTs, CP should be routinely measured intraoperatively.     

Comparison of cuffed, uncuffed tracheal tubes and laryngeal mask airways in low flow pressure controlled ventilation in children

Background : The use of low flow circle systems necessitates a ‘leak free’ breathing system which is commonly achieved by using a cuffed tracheal tube (TT). We hypothesized that low flow circle system anesthesia can equally effectively be achieved by using the LMA in pediatric anesthesia. Methods : Following local ethics committee approval we randomly recruited 45 patients scheduled for elective surgery and requiring mechanical ventilation into three groups (cuffed TT, uncuffed TT and LMA group, n = 15). The size of the TT was determined by means of the formula (age/4) + 4.5 for uncuffed and (age/4) + 4 for cuffed TT whereas the size of the LMA size was dependent on weight. Following induction of anesthesia and muscle paralysis patients were ventilated with pressure controlled ventilation through a pediatric circle system and the lowest fresh gas flow (FGF) determined. Results : The FGF achieved were (median and range) 0.20 (0.2–0.25) l·min^?1 for the LMA group, 0.20 (0.2–0.4) l·min^?1 for the cuffed TT group and 1.15 (0.2–4.75) l·min^?1 for the uncuffed group. The differences between the LMA and cuffed TT compared with the uncuffed TT were significant (P < 0.0001 and P = 0.0002, respectively). The difference in FGF between LMA and cuffed TT was not significant. Conclusion : We conclude that pressure controlled ventilation using an LMA is an alternative to a cuffed TT during low flow circle system anesthesia in children. Low FGF is unlikely to be achieved consistently using an uncuffed TT because of a substantial leak.     

Evaluation of a new recommendation for improved cuffed tracheal tube size selection in infants and small children

BACKGROUND: The purpose of this study was to evaluate a new recommendation for tracheal tube size selection using second-generation Microcuff paediatric endotracheal tubes (PETs) with optimized outer diameter (OD) of the distal tube. METHODS: With Ethics Committee approval, patients aged from birth to 5 years, requiring general anaesthesia with orotracheal intubation, were included. Tracheal tube sizes were selected as follows: internal diameter (ID) 3.0 mm, birth (if > or =3 kg) to <6 months; ID 3.5 mm, 6 to <18 months; ID 4.0 mm, 18 months to <3 years; ID 4.5 mm, 3 to <5 years. Tracheal tubes with the cuff not inflated were classified as too large if no air leak was obtained at an airway pressure of < or =20 cmH2O. Post-intubation stridor requiring therapy was noted. RESULTS: Three hundred and fifty children were studied. Nine tracheal tubes (2.6%) were too large and had to be exchanged: in patients requiring tracheal tubes of ID 3.0 mm and 3.5 mm, three and four tracheal tubes, respectively, and, in patients requiring tracheal tubes of ID 4.0 mm and 4.5 mm, one tracheal tube in each group. In three patients (0.9%), post-intubation stridor occurred which required therapy. CONCLUSION: The new recommendation presented for the use of second-generation Microcuff PETs with improved OD to ID ratio allows the selection of cuffed tracheal tubes with larger IDs than previously recommended for small children without increased need for tracheal tube exchange or increased incidence of post-intubation stridor in these age groups.