1
PISA UNIVERSITY
School of Medicine
Anesthesiology and Intensive Care Medicine Director: Professor Francesco Giunta
Thesis:
CUFFED VERSUS UNCUFFED ENDOTRACHEAL TUBES DURING PEDIATRIC GENERAL ANAESTHESIA:
CRITICAL REVIEW OF LITERATURE DATA AND COHORT STUDY OF PEDIATRIC
NEUROSURGICAL PATIENTS
Supervisors: Author:
Prof. Francesco Giunta Dr. Elena Di Pietro Dr. Leonardo Bussolin
2 Contents
1. Acknowledgements... 2. Introduction…...………... 3. History…….. ... 4. Recent developments and "fall of a myth" …….... 5. Sizing of the endotracheal tube in pediatrics…… 6. Arguments against use of cuffed tubes in children 7. Literature research methodology…...……… • Complications after extubation... ……...
• Costs ... • Differences among types of tracheal tube • Monitoring of respiratory parameters …... •Environmental pollution……….. • Safety margin positioning ……….. • Number of reintubations ………... • Intracuff pressure... • Incidence of aspiration……… .. • Specific applications ………... • Low flows mechanical ventilation... …….. 8. Results of the systematic review ………... 9. Clinical research: prospective study…...………... • Methods ... • Results ... • Discussion……... 10. Conclusions…... 11. References……...……… 3 4 4 7 9 16 20 21 29 30 32 33 35 37 39 40 42 43 45 46 46 47 49 50 52
3
Acknowledgements
I am grateful to Professor Francesco Giunta for his support, encouragement, patience and constructive criticism throughout the period of my research and thesis writing.
I would like to thank Doctor Leonardo Bussolin, Head of Trauma Center, Meyer Children’s Hospital of Florence for the introduction to this field of research and for his advice and help with data collection. I also wish to thank Professoressa Joanne Spataro for help in the revision of the manuscript.
Finally, my thanks go to my Parents, who never failed to give me moral and material support.
4
INTRODUCTION
The use of uncuffed tubes was the gold standard of tracheal intubation in children under 8 years of age for more than 50 years. In the adult, practice of endotracheal intubation began to develop in the 20s of last century, but the availability of the techniques and the tools have begun to be used in pediatric patients since the 60s. The rule that was taught and that could be found in most texts of pediatric anesthesia was represented by the principle that the use of cuffed tracheal tubes had to be absolutely avoided in children under 5-8 years of age.
The analysis of the most recent literature on the topic reveals that this principle is not applied in a comprehensive manner, it has empirical rather than scientific grounds and it can be considered as a passed "myth" of pediatric anesthesia. For this reason, in literature, a lot of editorials and reviews appeared from the years 2001 onwards, showing great interest in the subject [1,2, 3, 4, 5, 6, 7 , 8, 9, 10]. The arguments against the use of cuffed tubes in children appeared to still have logic elements based on the view that the basis of the narrowest portion of the pediatric airway is represented by the cricoid ring. It was widely recognized that the larynx had a funnel shape that, during development, gradually took on a cylindrical shape with the rima glottidis which became the stretch narrowest airway. The lumen of cricoid ring, i.e. the only fully rigid portion of the airways, was described as circular.
These anatomical aspects have recently been called into question.
HISTORY
Early studies on a child's larynx were conducted on corpses and go back to the end of XIX century [11, 12] [Figs. 1 and 2] They were the results of those studies that influenced the theoretical concepts and the subsequent management of pediatric airways. Since then, it has been accepted by all the assumptions that the larynx of a child "has a funnel shape with the narrowest point located at the lower end
5 of the larynx." With the growth, the larynx gradually assumes the cylindrical shape of the adult.
6 Fig. 2 - JE Eckenhoff ‘s historical publication
Actually, the description by Eckenhoff [12] about pediatric larynx, and which the totality of the anesthesiologists considered the milestone on the topic, was not the result of his original studies, but it was written more than half a century earlier, by Bayeux [11]. In
7 1897, Bayeux proposed his classic description based on anatomical sections and casts made from larynx of corpses of children between 4 months and 14 years. It is important to note that Eckenhoff said, showing some caution, however, that "the measurements could not possibly be fully applicable to the living." It is very likely that the laryngeal soft tissue proximal to the rigid cricoid cartilage were able to stretch and thus deform and change the cast ring cricoid cartilage [13].
RECENT DEVELOPMENTS AND "FALL OF A MYTH"
In 2003, Litman et al. [14] published a study on the size of larynx of 99 children, aged from 0 to 14 y.o., undergoing intravenous sedation in spontaneous ventilation in order to perform magnetic resonance. The above mentioned study showed that the shape of pediatric larynx is cylindrical with the narrowest portion represented by the rima glottis and this aspect remains constant throughout the period of growth.
In a following study, Dalal et al. [15] upheld the conclusions of Litman, presenting data of great interest regarding laryngeal size in 128 pediatric patients, aged 6 months to 13 years, during diagnostic bronchoscopy under general anesthesia with muscle relaxation.
So, according to these publications, which are revolutionizing the beliefs and notions held so far, the airway’s narrowest anatomic stretch is the rima glottidis both in adults and children, even if the cricoid ring remains the tight stretch from the functional point of view. This aspect is of vital importance for pediatric anesthetists, especially regarding the identification of what might be the most riskful area for ischemic damage following tracheal intubation.
Another important element that derives from the above studies is represented by the proof that the cricoid ring is not circular, but elliptical, hence a tracheal tube, which has a perfectly circular section, will tend to lodge posteriorly and will not determine a perfect seal, unless it is oversized. This can result in a high pressure on the areas of the posterolateral cricoid, with consequent possible ischemia, and a seal failure in its front part [13].
8 A further reason for not using cuffed tracheal tubes in the pediatric patient was represented by the fact that the selected diameter is less than that of the uncuffed tubes to make easier the overcome of the cuff through the glottis with consequent significant increase in the flow resistance in the case of anesthesia in spontaneous ventilation [16].
Another argument against cuffed tube was based on the previous case reports of laryngeal and/or tracheal lesions observed in prolonged intubation in the ICU and caused by hyperinsufflation of high pressured- low volume cuffs [17, 18].
The current trend, characterized by more widespread use of cuffed endotracheal tubes in the child, shows a different reality. As reported below, a number of studies of numerically significant populations has shown that the use of cuffed tubes is associated with a reduced incidence of post-extubation stridor. In addition, the relatively recent use of thin cuffed tubes (i.e. high-volume and low pressure) causes less potential compression on the mucosa of the cricoid, while ensuring the stability by the cuff itself in correspondence of the upper and distensible trachea where rings are incomplete posteriorly. With these cuffes the stability is provided with an intracuff pressure which is less than 15 mmHg, that is, less than 20 cmH2O, which is considered the level of capillary perfusion pressure.
Furthermore, the front surface of the cricoid ring is coated with areolar connective tissue which is particularly exposed to edema formation, resulting in ischemic mucosal compression caused by an oversized tube. Ischemia leads to ulceration of both mucosa and perichondrium. This is followed by deposition of collagen, fibrosis and ending stenosis. An oversized tube can also result in other pathological consequences, such as the development of ductal cysts and fibrosis of vocal cords [19].
The incidence of laryngotracheal stenosis in pediatric patients has increased with the increase in the use of tracheal intubation, with percentages varying from 0.7% to 8% [20, 21, 22, 23, 24, 25].
To minimize laryngeal and tracheal traumas, uncuffed tracheal tubes in children under 8 years of age were increasingly preferred. Later, it
9 was observed that such traumas can occur with the use either of cuffed tubes and of uncuffed ones, especially if oversized [26, 27]. Repeated collisions which are consequent to the movements "up and down" of the uncuffed tube are another mechanism that can cause trauma of the anterior tracheal wall, because of its lower adherence and fixity.
TUBE SIZING IN PEDIATRICS
Capillary perfusion pressure in the adult trachea varies in a range from 25 to 30 mmHg [28, 29]. It is believed that the values are similar in the child, although this has not been demonstrated. So, in order to reduce the compression forces on the tracheal mucosa, it is assumed that the intracuff pressure should be maintained with a maximum value of 25 mmHg (or 34 cmH2O, being 1 mmHg = 1:36
cmH2O) [30,31].
The choice of an appropriate measure of the tube in the pediatric patient should be aimed to facilitate mechanical ventilation, limiting the laryngeal and tracheal traumas. To do this, we have proposed some formulas for the calculation of the internal diameter of the tracheal tube [Tab. I], bearing in mind that an ideal measure does not exist.
10 Tab. I - Formulae to calculate tube size in pediatrics.
NEWBORN (tube diameter / gestational age (weeks) <0.1) [32]
2.5 (< 1 kg) 3.0 (1-2 kg) 3.5 (> 2 kg)
AGE > 1 YEAR
Uncuffed tracheal tube
Modified Cole formula [16, 33]:
ID (mm) = age (yrs)/4 + 4
Morgan and Steward formula [34]:
ID (mm) = 16 + age (yrs)/4
Cuffed tracheal tube
Motoyama formula [16]:
ID (mm) = age (yrs4 + 3.5
Khine formula [35]:
11 Duracher C et al [36] tested the use of Khine formula on 204 pediatric patients undergoing general anesthesia and mechanical ventilation. The authors concluded that this formula underestimates the cuffed tube diameter of about 0.5 mm, thus recommending the use of Motoyama formula [16].
One widespread method to determine the most appropriate measure of the tracheal tube in the child is the so called "leak test", which demonstrates the loss of gas at a positive inspiratory pressure by auscultating with a stethoscope, placed on the front side of the neck [37]. This type of approach shows that the tracheal mucosa is not excessively compressed by the tube and/or by the cuff. The leak test consists in closing the circuit valve. This maneuver slowly increases the airway pressure and it gradually reaches a value at which the loss of air begins to be heard. The presence of air leak at a low pressure value (for example less than 10 mmHg) may indicate that the tracheal tube is too small for the patient, while the absence of air leak at a pressure higher than 25 mmHg indicates that the tube is too large and this could result in compression, risk of ischemia and mucosal damage. This method is the most appropriate to be sure that the tube is not pressing on the mucosa.
The air leak may be negative immediately after intubation and it usually turns into positive with the deepening of anesthesia or by changing head position [38] .In most cuffed tubes the top of the cuff corresponds to the upper edge of the marker of depth of uncuffed tubes. Furthermore, the depth markers are not present in cuffed tubes or they are situated at a too high level [39]. Thus, the cuff may be positioned in an inappropriate site: between the vocal cords, or in the subglottic space, if patient’s age is used to calculate the tube depth. The ideal cuff position should be below the cricoid ring in correspondence of tracheal rings in order to prevent subglottic mucosal trauma and its sequelae [Fig. 3]. On the other hand, if endotracheal tube is positioned below cricoid ring and the cuff is too long, endobronchial intubation is a possible risk. To ensure that the cuff is placed at the right level, cuffs should be short and the tube should not have eye Murphy.
12 Fig. 3
Stability provided by the cuff presence significantly reduces the endotracheal tube movements and tends to hold up and detach the tip of the tube from the tracheal wall so to stay in a more central position. This further helps to reduce the risk of airway trauma [40]. Shibasaki M et al [41] have proposed the use of ultrasound to determine with greater precision the appropriate diameter of endotracheal tube, both cuffed and uncuffed. The agreement calculated ratio shows a significantly higher prediction capability
Rima Glottidis
Cricoid Ring
13 with the ultrasound method, compared to the formulas described in Tab. 1 [Fig. 4].
Fig. 4
As previously said, the profile of airways and tracheal tube are different and the points on which can be exerted a greater pressure are represented by the mucosa of posterior-lateral area of larynx and trachea. This is in agreement given the fact that most of subglottic lesions associated with the use of uncuffed tubes are posterior, except for anterior tracheal lesions which are more frequent because they are caused by the movements of the tube tip.
Because of these anatomical aspects, it can be concluded that the application of an airway pressure of 20 mmHg can avoid the contact of tracheal tube with the tracheal mucosa, while it may be still high in correspondence of the rear face of the subglottic tract. The use of a cuffed tube may allow the choice of a smaller size, thus reducing the risk of damage to the larynx. Furthermore, the presence of a cuff
14 keeps away the tube tip from the anterior tracheal wall, thus reducing, also in this case, the risk of possible damage [1].
During anesthesia with nitrous oxide in pediatric patients, Felten et al. [42] observed that the pressure intracuff increases mainly in the first 105 min of mechanical ventilation. Hence, the authors concluded that intracuff pressure is unpredictable after insufflation with air and that numerous aspirations from the cuff itself, so to maintain pressure lower than 25 mmHg in case of using nitrous oxide, are required.
Special care should be taken when proceeding to deflate the cuff, to the subsequent formation of folds and flaps that could be responsible for mucosal injury through a shearing action during breathing movements. For this reason, desufflation of cuff should be carried out only just before extubation [43].
Undoubtedly, the first generation of endotracheal tubes made of red rubber cuffs, at high pressure and low volume [Fig. 5], yielded potential injury to larynx and trachea in both adults and children, sometimes resulting in severe damage and significant long-term sequelae (eg, need of permanent tracheotomy).
15 Fig. 5
The subsequent appearance of plastic tubes, less irritating and with cuffs at high volume and low pressure, has solved these problems in adults, making the uncuffed tracheal tube the universal standard for this patients’ population [5].
Indeed, a peculiar case is represented by pediatric patients undergoing cardiac surgery (including those cases undergoing cardiopulmonary bypass) in which metabolic monitoring requires a good seal routes to allow accurate measurement of oxygen consumption and carbon dioxide production. This is a distinct population at high risk because of the long periods of low perfusion when the bypass is applied. In such cases, the mucous capillary circulation can be seriously compromised in the area of the trachea in contact with the cuff. However, despite the fact that these patients are of course subject to mucosal ischemic damage, in numerous case studies of patients undergoing prolonged follow-up, cases of serious complications in the airways attributable to the cuff were identified
16 [44]. This does not exclude, obviously, the existence of minor injuries, but it is a strong argument in the debate against the use of cuffed tracheal tubes [5]. The rare case reports of airways’ lesions caused by the use of a cuffed tube were related to inappropriate management and inadequate equipment [43, 45].
Cuffed Tube and uncuffed tube
TOPICS AGAINST THE USE OF CUFFED TUBES IN PEDIATRICS
Holzki et al [46] are among the most determined opponents of the use of cuffed tracheal tubes in children. They claim that stridor, the indicator most commonly used, is not appropriate to identify and subglottic tracheal mucosal trauma and complications of airway should be evaluated with endoscopy breathing. These authors show that the symptoms of airway injury may not be immediately available, although it is unclear if they suggest to subject all children to endoscopy after extubation. In any case, even if a subglottic stenosis requires a period of time to be clinically overt, it is estimated that patients with such a situation will return to the observation and consequently be subjected to further diagnostic endoscopy. Wiel et al point out the importance of coexistent diseases that reduce mucous
17 capillary perfusion pressure and advise in such instances to perform a respiratory endoscopic follow up [26].
Holzki et al [46] have also sought and presented a series of images of trauma in pediatric airway related to tracheal intubation, although it is not absolutely clear which types of management were associated with these lesions. The authors report a marked increase in the incidence of severe trauma of the airways in their hospital at the same time of publication of the article Khine et al. 1997 [35]. They state, sometimes in a slightly self-referential way, that warnings about the risks of the use of cuffed tubes in children had appeared repeatedly in the literature. By contrast, it refers to sporadic, also particularly outdated, case reports. These alarming aspects have never appeared in the now extensive literature on the subject and it seems highly unlikely that such a marked increase in airway pediatric trauma, if done elsewhere, has never been reported from international experience.
Holzki et al [46] documented several cases of laryngeal lesion in children intubated with cuffed endotracheal tubes and, according to their beliefs, the incidence of airway trauma is high, with 82% of these cases related to the use of excessively wide tracheal tubes, rather than on the type of cuff.
However, no study has shown that a cuffed endotracheal tube, compared with an uncuffed one, increases risk of complications in the airways, as long as you choose an appropriate measure and intracuff pressure is monitored [37].
18 Tab. 2 – Pros and Cons in the use of cuffed and uncuffed tracheal tubes in children. UNCUFFED TUBES PROS CONS - A loss at 20-25 cmH20 may indicate a minimum mucosa pressure - A larger inner diameter by age: • Low flow resistance • Easier aspiration
- High rate of tube replacement: • Repeated laryngoscopies • Increased costs - Airway trauma:
• The oversized tubes exert excessive pressure on the cricoid mucosa • Undersized tubes cause movements which potentially damage the airways - Air leakage: • Inaccurate respiratory monitoring • Unreliable oxygenation and ventilation • High gas flows
• High gas consumption • Environmental
pollution
• Risk of pulmonary aspiration
19
CUFFED TUBES
PROS CONS
- Stability of the
endotracheal tube trough the cuff
- Easily adjustable cuff volume
- Use of low gas flows reduces consumption and anesthetic gases costs - Lower outer diameter:
• Less pressure on the cricoid mucosa - Reduced risk of
aspiration
- Improving of ventilation, especially in low lung compliance - Reduction of number of reintubations • Reduced costs • Fewer laryngoscopies for reintubation - Smaller internal diameter: • Increased flow resistance • Harder suction - Airway trauma: •Mucosal ischemia - Need to monitor cuff
pressure
- Qualitative tube design defects
- Minor safety margin to the tube
positioning
- Increased costs for a single device
20
LITERATURE RESEARCH METHODOLOGY
The literature research on the use of cuffed and uncuffed tracheal tubes in children was conducted according to the Cochrane methodology [47].
They used three databases, PubMed, Cochrane Collaboration and Primo Central, using the following keywords: pediatric endotracheal intubation, endotracheal cuffed tube, uncuffed endotracheal tube, pediatric age group. Only publications derived from peer-reviewed journals were included.
All primary outcomes and each study-design were cataloged and evaluated.
Fifty-seven studies were selected from an initial group of 239 publications.
They considered the following primary outcomes:
1) Post-extubation complications, such as stridor, laryngospasm, edema and subglottic stenosis
2) Economic costs
3) Differences based on the type of endotracheal tube 4) Monitoring of respiratory parameters
5) Environmental pollution
6) Safety margin positioning
7) Rate of reintubation 8) Intracuff pressure
9) Incidence of aspiration
10) Specific applications
21
1) Post extubation complications
Tab. 3 - Studies on uncuffed tracheal tubes
Author Review Year Study Outcome N ° Pts Complic Age Setting Puhakka HJ et al. [89] Acta Pediatr Scand 1990 Cohort Observational with endoscopy SGS 2.500 31 p 1.24 % 0-13 m ICU Stamm D et al. [90] Arch Fr Pediatr 1992 Cohort Observational with endoscopy SGS 1006 12 p 1.5 % 5m-7y ICU Contencin P et al. [91] Arch Otolar Head Neck Surg 1993 Cohort multicentric Stridor 247 5 p 2% 0-1 m ICU Grundfast KM et al. [92] Ann Otol Rhinol Laryng 1990 Prospective Observational with endoscopy SGS 159 3 p 1.9 % Mean 5.7 days ICU Parkin et al. [93] Ann Otol Rhinol Laryng 1976 Retrospective SGS 292 15 p 5.1 % New- born ICU Strong RM et al. [25] Arch Otolary ngol 1977 Retrospective SGS 88 5 p 5.7 % New- born ICU Papsidero MJ et al. [22] Ann Otol Rhinol Laryng 1980 Retrospective SGS 562 30 p 5.3 % New- born ICU Sherman JM et al. [32] J Pediatr 1986 Prospective SGS 102 10 p 9,8 % New- born ICU Nicklaus PJ et al [21] Laryng oscope 1990 Prospective SGS 289 7 p 2.4 % New- born ICU Litman RS et al. [49] Anesth esiol. 1991 Prospective Stridor 5589 0.1 % 7m-9y OR Parkin JL et al. [50] Ann Otol 1976 Retrospective SGS 603 15 p 2.5 % New- born ICU Black AE, et al. [24] Br J Anaest h 1990 Retrospective Stridor SGS 2791 Stri dor 44p 1.5 % SG S 0 Da ≥28 gg a ≤ 10 aa ICU Koka BV et al [51] Anesth Analg 1977 Prospective with the control group Stridor 7875 80 p 1% Da < 1 anno a 17 aa ICU
22 al [23] Dis Child 0.45 % basso peso Battersby EF et al. [48] Anaest hesia 1977 Retrospective SGS Stridor 435 SS G 0 Stri dor 21 p 4.8 % 0 – 5 y ICU Suzumura H et al [52] Pediatr Int 2000 Retrospective SGS 62 7 p 11.3 % New- born ICU SGS = Subglottic stenosis p = patients
The analysis of the studies reported in Tab. 1, then on newborns’ populations with use of uncuffed tube, seems to allow the following conclusions:
- Probably the cause of the SGS is multifactorial;
- The main factors contributing to the development of SGS are represented by the diameter of the tube, the length of intubation, from the frequency of the changes of the tube and infection related to the presence of the tracheal tube;
- Another risk factor for the development of SGS in infants appears to be represented by the type of intubation, oral- or nasotracheal. Ratner et al [23] point out that this complication was not observed in the first three years of observation during which only nasotracheal intubation was practiced; the same conclusion was reported by Battersby et al [48];***
- The low incidence of SGS in some PICUs makes it difficult to reach sufficient numbers to derive significant useful correlations in recognizing the causes;
- Literature mainly concerns Neonatal ICU populations;
- Publications of Black et al [24] and Koka BV et al [51] are of particular interest because they consider not only neonatal patient
23 populations, but until more than 10 years (Black) and 17 years (Koka), with a division into age groups;
- In the series of Black, stridor never arose in the neonatal group and in 25% of the group up to 1 year. There have been no reports of SGS; - A publication of Kokamerita analyzes the study design and the size of the examined population. A higher incidence of stridor in the age group 1 to 4 years was detected. What was surprising and inexplicable was the low incidence of stridor in patients younger than 1 year (Fig. 6). Finally, the possible factors that may influence the onset of stridor were examined (Figure 7). The factor that predisposes to a higher incidence of post-extubation stridor is represented by the changes of position and not by the duration of intubation, as in much of the literature is reported.
Fig. 6 - Relationship between age and onset of post-extubation stridor
24 Fig. 7 – Factors which potentially favor the onset of post-extubation stridor
- A publication of H Suzumura et al [52] appears of particular importance as it is the only one which correlates the onset of SGS with the presence of airways infection in a population of babies intubated for a period exceeding 14 days. The conclusions of the study is that the respiratory tract infection should be considered a major risk factor for the development of SSG. For this reason, the prevention of infection can reduce the incidence of SGS;
- SJ Gould et al [53], in a study on autopsies, claimed that the subglottic damage is established early in tracheal intubation. In addition, they showed that the lesion is a frequent event and healing usually occurs during the second and third week of intubation of permanence of the tracheal tube. The study suggests that the high grade lesions are a complication that occurs in the early stage and that the duration of intubation is probably not responsible for determining a SGS.
25 Tab. 4 - Studies on cuffed tracheal tubes
Author Review Year Study Outcome N°Pts complic Age Setting
Newth CJL et al [54] J Pedia tr 2004 Prospective Comparison cuff vs. no cuff Stridor 860 No differences between the two groups 1 g – 30 y ICU Murat I [55] Paed Anae st 2001 Report Prospective SGS Stridor 5435 of who m 3434 < 8 y e 904 <1y 0 0 0-8 y OR Weiss M et al [56] Br J Anae st 2009 Multicentric prospective randomized controlled Stridor 2246 No differences between the two groups 0-5 y OR Deakers TW et al [57] J Pedia tr 1994 Prospective Comparison cuff vs no cuff Stridor 243 No differences between the two groups 8.08 mean age in no cuff group 2.53 mean age in no cuff group ICU Khine HH et al [35] Anest hesiol 1997 Prospective randomized controlled cuff vs no cuff Stridor 488 No difference between the two groups 0-8 y Omoge neous groups OR Magh- soudi B et al [58] Med J Islam ic Rep Iran 2010 Prospective Comparison cuff vs no cuff Stridor 128 More incidence of stridor in no cuff group probably linked to numerous reintubatio ns 0-8 y OR Mhanna MJ et al [59] Crit Care Med
2002 Retrospective Stridor 105 < 7y air leak has a
low sensibility
in
26 - Publications on the use of cuffed tubes in pediatrics are newer and of higher quality than publications on the use of uncuffed tubes; - A critical problem that emerges from the analysis of the studies is the very wide range of ages. According to that, the biggest part of clinical records is not divided into age groups;
- The "setting" is particularly interesting and it is represented by either the operating room (populations undergone tracheal intubation in general anesthesia for a limited time [55, 56, 35, 58, 60]), and the PICU (intubated patients in prolonged general anesthesia [57, 59]); - Stridor is considered the hallmark of complication after extubation. There are limits to the reliability of signs of damage such as laryngeal stridor related to tracheal tube, either tracheal and subglottic, since its diagnosis is subjective, even when used scoring
predicting stridor ≥ 7 y can predict stridor Calder A et al [60] Paed Anae st 2011 Prospective cuff vs no cuff Faringo dynia 500 111(22%) faringodyn ia, 19% cuff and 37% no cuff 3-16 y OR Bordet F et al [61] Paed Anae st 2002 Prospective Unspec ific respirat ory compli cations 891 6.6 y±5.1 OR Dillier CM et al [43] Can J Anest h
2004 Case report Laryng eal damage web-like 1 - 13 m OR Sathy- armoort hy MK et al [62] Anest hesiol 2013 Small case serie Stridor 3 28 w 30 w OR Mossad E et al [44] J Cardi othor ac Vasc Anest h 2009 Retrospective SGS 783 17 p 2.2% < 2 y OR
27 scales. For this reason, as previously reported, Holzki et al [46] believe that post-extubation stridor is not a scientifically valid airway lesion. These authors state that post-extubation lesions may develop even at distance of time and without the presence of stridor; However, if that were true, we should admit that the damage itself is not preceded by an initial edema that, according to the experience and the pathophysiology, must be present and responsible of stridor in most cases; this principle is the proof that the use of aerosolized racemic epinephrine solves the stridor in the case series studied, and this treatment is a further indication of the existence of specific subglottic edema;
- By the above mentioned studies, it appears that further contraindication to the use of cuffed tracheal tube in children under 8 years of age is not justified, although the need for a more accurate management is required, i.e. choice of an appropriate diameter and intracuff pressure monitoring;
- The absence of an appropriate follow-up in the long term is an additional critical issue emerging from these studies analysis, although it is conceivable that intensive care and / or services of anesthesia would be informed of the onset of respiratory complications in patients who had undergone tracheal intubation; - The Khine [35] must be considered the first that contributed to encourage the use of cuffed tracheal tube in pediatrics, taking into consideration not only the incidence of post-extubation stridor, but also the number of replacements of the tracheal tube and the use of the low flows ventilatory technique (Fig. 8);
28 - Bordet et al [61] share the same findings of Khine et al [35], highlighting that in a population of pediatric patients undergoing anesthesia, the use of cuffed tracheal tubes was not associated with an increased risk of perioperative respiratory complications.
- The survey lead by Orliaguet GA et al [63] proposed a questionnaire to 130 French pediatric anesthesiologists using the cuffed tube. 25% used routinely cuffed tubes in more than 80% of their patients. This indicates that in clinical practice, starting from 2001, part of pediatric anesthetists used cuffed tubes before the publication of additional evidence. Unfortunately, this article does not indicate the age of the patients, and this is definitely an important lacking data;
- Murat I [55], despite publishing a simple letter, reports her significant experience, which began after the publication of Khine et al article, in 1997 [35]. From that year in her hospital purchasing uncuffed tracheal tubes was stopped. The author collected data of all anesthesia with endotracheal intubation (5435) carried out in 2000, of which 3434 under 8 years of age and 904 under one year of age. No respiratory complication was attributed to the endotracheal tube, and in particular, no single case of subglottic stenosis was observed. Air control of operating rooms showed a marked reduction in the rate of pollution caused by anesthetic gases. Finally, anesthesiologists did not insufflate cuffs without air leak and when they insufflated it they always monitored intracuff pressure;
- In a population of 783 patients under 2 years of age undergoing cardiac surgery, Mossad et al [44] recorded the cases of 17 SGS, corresponding to 2.2%. By comparing their data with those of other series in the literature, the authors conclude that the use of cuffed tracheal tubes does not appear to increase the risk of postoperative SGS;
- The few studies which attributed damage to the use of cuffed tracheal tube are represented by case reports [43] or case series [62], from which practical behavior is not scientifically correct.
29
2) Costs
Tab. 5
Author Review Year Study Outcome N° Pts complic Age Setting
Eschertzhuber S et al [64] Acta Anesthesiol Scand 2010 Prospective Randomized controlled gas consumption and related costs 75 - Mean 1.73 y (0.01- 4.8) OR
- Eschertzhuber S et al. [64] is the only one in the literature which takes into account costs related to use of gas and sevoflurane. This outcome leads to the choice of adopting technique of low flows ventilation only if cuffed tracheal tube were used, since there is a perfect seal between the tube and the trachea. The study design is a controlled randomization of patients into 2 groups: “cuffed” group and “uncuffed” group. The results are shown in Fig. 9. The authors conclude that the use of cuffed pediatric tracheal tubes in combination with the technique of low flow anesthesia reduces the economic costs associated with the consumption of sevoflurane and medical gases compared to use of uncuffed tubes.
30
3) Differences based on the type of endotracheal tube
Tab. 6
Author Review Year Study Outcome N° Pts complic Age Setting
Weiss M et al
[65]
PaedAn aesth
2006 In vitro study Qualitative characteristics of tracheal tubes - - 0-15 y OR Dullen kopf A et al [66] Acta Anesth esiolSc and 2005 Cohort Observational Qualitative characteristics of
the new type of tracheal tube Microcuff 500 0-14 y OR Salgo B et al [67] Acta Anesth esiolSc and 2006 Cohort Observational Qualitative characteristics of
the new type of tracheal tube Microcuff 350 0-5 y OR Weiss M et al [68] Br J Anaest h
2004 In vitro study Qualitative characteristics of tracheal tubes 125 tubes - - - Dullen kopf A et al [69] PaedAn aesth 2004 Cohort Observational Qualitative characteristics of
the new type of tracheal tube Microcuff 80 2-4 y OR Weiss M et al [70] Can J Anesth 2005 Cohort Observational Qualitative characteristics of
the new type of tracheal tube Microcuff 100 0-16 y OR Bernet V et al [71] Anaest hesia
2005 In vitro study Qualitative characteristics of
the new type of tracheal tube Microcuff 8 tubes - - Weiss M et al [72] Br J Anaest h 2005 Cohort Observational Qualitative characteristics of
the new type of tracheal tube Microcuff 250 0-16 y OR Bernet V et al [73] Anaest hesia
2006 In vitro study Qualitative characteristics of
the new type of tracheal tube Microcuff 8 tubes - - Moehrl en U et al [74] PaedAn aesth
2008 In vitro study Quality features of the new type of
tracheal tube Microcuff
8 tubes
31 - Weiss M et al [68] are the authors of the first publication that takes into account the differences in quality of various tracheal tubes on the market. They are compared with the physical aspect of 125 types of tracheal tube according to the anatomical parameters routes and age-related calculation formulas of the tube diameter. The authors conclude that the majority of pediatric tracheal tubes have poor accuracy of drawing, particularly those of a smaller size and they hope for a rapid improvement in the design of cuffed tubes with an increase of the volume / pressure ratio of cuff, an increase of the subglottic section still free from the cuff and more appropriate markers of depth.
- Weiss et al [65] compares the 5 brands of preformed cuffed and uncuffed tubes. The following features are considered:
1) distance between the curve and the pre-shaped tip of the tube 2) distance between the curve and the upper edge of the cuff
The authors conclude that improvements are needed in terms of quality of preformed tracheal cuffed tube. In particular, the previous features should be standardized, in order to reduce the risk of too deep intubation and check the exact position of the cuff into the trachea.
- Numerous studies have been performed to verify the qualitative peculiarities of the new tube Microcuff with a very thin cuff and with a high volume / pressure ratio. Dullenkopf A et al [66, 69, 70, 71, 72, 73, 74] emphasizes the safety and stability. Salgo B et al [67] show the best ratio outside diameter (OD) / inner diameter (ID) It allows the choice of a greater inner diameter for age.
32
4) Monitoring of respiratory parameters
Tab. 7
Author Review Year Study Outcome N° Pts complic Age Setting
Main E et al [75] Intensive Care Med
2001 Cohort Tidal Volume, compliance, elastance
75 - 0.02-12.8 y
ICU
Almost all of the editorials and reviews on the use of cuffed tracheal tubes in children show that because of the absence of cuff monitoring, respiratory parameters become difficult and unreliable. In particular, the entity of expiratory volume, breathing resistance and compliance may be overestimated in the presence of air leak and consequently clinical decisions can then be unreliable.
Main E et al [75] evaluated these aspects in 75 pediatric patients paralyzed and mechanically ventilated. The authors concluded that a greater loss than 20% results in an inconsistent current volume and an overestimation of compliance and resistance, regardless of the choice of ventilation mode [Fig. 10].
33 Fig. 10
5) Environmental pollution
Tab. 8
Author Review Year Study Outcome N° Pts complic Age Setting
Khin e HH et al [35] Anesth esiol 1997 Prospective randomized controlled cuff vs no cuff Ppm N2O in air 488 No differenc es between the two groups 0-8y homog eneous groups O R Mur at I [55] PaedA naesth 2001 Report prospective Ppm N2O/ sevorane in air 5435: 3434 < 8 y e 904 <1y 0 0 0-8 y O R Ram an V et al [76] Int J Pediatr Otorhi nolary ngol 2012 Coorte prospective Ppm N2O in orophary ngeal cavity 200 1-18 y O R
34 - Khine et al [Fig11] [35] and Murat [Tab. 9] [55] have revealed significant differences of environmental concentration of nitrous oxygen comparing the use of cuffed and uncuffed tracheal tubes.
Fig. 11 - Different concentrations of nitrous oxide with the use of cuffed and uncuffed tubes [35]
Tab. 9 - Different concentrations of nitrous oxide and sevoflurane with the use of cuffed and uncuffed tubes [55]
Nitrous oxide Sevoflurane
Before cuffed tubes 192 ppm 48.1 ppm
After cuffed tubes use 29.4 ppm 0.3 ppm
- RamanV et al [76] showed a significant contamination of the oropharynx in a population of pediatric patients undergoing adenotonsillectomy under general anesthesia with halogenated inhalation and FiO2 100% [Fig. 12].
35 Fig. 12
6) Safety margin positioning
Tab. 10
Author Review Year Study Outcome Outcome
Ho AMH et al [77] Anaesthesia 2002 In vitro study Safety margin Cuffed < 50% non cuffed
36 The safety margin of a tracheal tube is defined as the distance between the upper and lower placements at the level of which may arise adverse effects. For a tracheal uncuffed tube, the most cephalic position without excessive loss and risk of extubation, has the tip of the tube just exceeding and aligning immediately below the rima glottis. For a cuffed tracheal tube, the most cephalic position is reached when the proximal edge of the cuff is located immediately below the vocal cords; this position can cause trauma of the glottis and a low resistance, despite a sufficient cuff inflation. The location most distal end of the tube that does not cause carinal stimulation or accidental bronchial intubation is the same for both tubes, with the tip positioned immediately above the carina.
In their study, Ho AMH et al [77] define margin of safety the distance between the most cephalic and more caudal positions (T for uncuffed tubes and TL for those cuffed [Fig. 13]. The authors conclude that, when compared with the uncuffed tubes, the cuffed tracheal tubes have a safety margin below about 50%. This data must then be kept in mind when the cuffed tracheal tube is chosen by the anesthetist.
37
7) Number of reintubations
Tab. 11
Author Review Year Study Outcome N° Pts complic Age Setting
Khine HH et al [35] Anest hesiol 1997 Prospective randomized controlled cuff vs non cuff Number of reintuba- tions 488 More frequent in non cuffed group 0-8 y OR Weiss M et al [56] Br J Anae sth 2009 multicentric prospective randomized controlled Number of reintuba- tions 2246 More frequent in non cuffed group 0-5 y OR Dorsey DP et al [78]
Burns 2010 Retrospective Number of reintuba- tions 327 More frequent in non cuffed group 0-10 y OR
- The three studies reported take into account the number of substitutions of the tracheal tube caused by incorrect calculation of the diameter, resulting in over- or under-sizing, and accidental extubation. As previously said, the presence of the insufflated tubes makes the tube more stable and less exposed to up and down movements of the extremity. The results are unanimous, showing a rate of significantly lower reintubation with the use of cuffed tracheal tubes compared with uncuffed ones [Fig. 8, 14, 15];
- Publication of Dorsey DP et al [78] covers a population of pediatric patients undergoing general anesthesia for treatment of burns. The authors point out that, given the high incidence of uncuffed tracheal tube replacement, the use of cuffed tracheal tubes in this patient population should be emphasized in order to reduce the rate of airways manipulations.
38 Fig. 14- Tube replacement rate according to Weiss HH et al [56]
Fig. 15 – Tube replacement rate according to Dorsey DP et al in patients with burns [78]
39
8) Intracuff pressure
Tab. 12
Author Review Year Study Outcome N°Pts compl Age Setting
Felten ML et al [42]
AnesthAnalg 2003 Cohort study Intracuff Pressure 174 p - 0-9 y OR Ong M et al [79] Anaesthesia 2008 Prospective cohort study Intracuff Pressure 640 p - 0-15.8 y OR Tobias JD et al [80] Int J PediatrOtorhin olaryngol
2012 Cohort study Intracuff Pressure 200 p - 1 m-17y OR Kako H et al [81] PaedAnaesth 2013 Prospective cohort study Intracuff Pressure 200 p - 0.9-17.8 y OR
Studies regarding cuff pressure highlight the following conclusions: - Intracuff pressure has an unpredictable trend when nitrous oxide is used, known the gas diffusion phenomena. For this reason, repeated measurements and desufflations of cuff are needed in order to maintain the pressure within less than the aforementioned threshold value of 25 mmHg;
40 - To prevent that intracuff pressure exceeds the critical value of 20 mmHg (the value of capillary pressure tracheal mucosa), routine use of manometer for monitoring pressure is necessary;
- Kako H et al [81] demonstrated in their study that significant variations of intracuff pressure values with changes in the position of patient occur and in most cases an increase of this value is reported. The authors conclude that pressure cuff should be measured at every change of patient position.
9) Impact of aspiration
Tab. 13
Author Review Year Study Outcome N° Pts Age compl Setting
Browning DH et al [1] J Pediatr 1983 Comparative cuff vs no cuff Aspiration 22 p No cuff: 1 w-5y Cuff: 4-18y - ICU Gopalareddy V et al [3] Acta Paediatr 2007 Comparative cuff vs no cuff Aspiration 27 p No cuff 1±0.9 y Cuff: 12±5 y - ICU
- The scientific work of highest quality is by Gopalareddy V et al [83], who performed it on a population of pediatric patients on mechanical ventilation in ICU. The authors determined with enzymatic method the presence of gastric pepsin in tracheal aspirates. The results, shown in Fig. 16, demonstrate a greater presence of pepsin in tracheal aspirates of patients with uncuffed tube;
41 Fig.16
** Statistically significant difference (p <0.05) with the other two groups with one group and *.
- An important critical issue of this work is represented by the extreme age difference in the groups being compared;
- Publication of DH Browning et al [82] is probably the first work in which the use of cuffed tubes in children appears.
42
10) Specific applications
Tab.14
Author Review Year Study Outcome N° Pts Age complic Setting
Greemberg L et al [1] PaedAnaesth 1999 Case report Tracheo-esophageal Fistula 1 Newborn - OR Oh AY et al [2] AnesthAnalg 2003 Case report One Lung Ventilation 1 8 y - ICU Lucking-Famira KM et al [3] Intensive Care Med 2004 Case report Tracheo-esophageal Fistula 1 Pre-term 770 gr - ICU Sheridan RL PediatrCrit Care Med 2006 Case serie
Burns 5 Mean age 2.2 y±1.0
- Burn unit
- The four reports envisage the use of cuffed tracheal tube for specific applications;
- Greemberg L et al [84] used the cuffed tracheal tube to occlude the loss through a congenital tracheo-esophageal fistula in a newborn of 2,655 kg in order to prevent gastric dilatation during mechanical ventilation. After surgery of fistula closure, the patient was intubated and ventilated for 48 hours with the desufflated cuff. After extubation, the postoperative course was satisfactory with restoration of normal power supply;
- Also Lucking-Famira KM et al [86] reported the treatment of a tracheoesophageal fistula with cuffed tube in order to occlude the aforesaid fistula, but in this case the patient was a premature of extremely low weight (770 gr 27 weeks of gestation). The correct position was confirmed by direct visualization with fiberoptic bronchoscopy. The intracuff pressure was maintained at a value of less than 15 cmH2O. After surgical closure of the fistula, the patient
was reintubated with uncuffed tube. The extubation occurred at 27 days of life without bronchoscopic signs of mucosal damage;
43 - Oh AY et al [85] used successfully a cuffed endotracheal tube to perform bronchial anastomosis surgery in a 8-year-old patient who had suffered a rupture of the left main bronchus with bilateral pneumothorax and chylothorax after car accident ;
- Finally, Sheridan RL [87], burns surgeon at Shriner's Hospital in Boston, states that in severely burned pediatric patients undergoing mechanical ventilation uncuffed tubes should not be used for the frequent need for reintubation, (which in this patient population can represent a high-risk procedure for the situation of concomitant inhalation injury of the upper airway and massive facial edema).
11) Low flows mechanical ventilation
Tab. 15
Author Review Year Study Outcome N° Pts compl Age Setting
Khine HH et al [1] Anesthesiology 1997 Prospective randomized controlled cuff vs non cuff Low flows 488 - 0-8 y OR Engelhardt T et al [2] PaedAnaesth 2006 Prospective randomized controlled Low flows 45 - 5-13 y OR
- The aforementioned work by Khine HH et al [35] was the first to take into account the differences between cuffed tracheal tubes and not during mechanical ventilation with low flow technique. This type of ventilation requires a sufficient seal between the tube and the trachea. This study found that intubated patients without cuff needed flows > 2 l / min with significantly higher incidence than in the group with cuff [Fig. 8];
44 - In the most recent study by T Engelhardt et al [88], the authors compared the use of cuffed tubes, uncuffed tubes and laryngeal mask airway (LMA) in a population of pediatric patients undergoing mechanical ventilation at low flows. Fig. 14 shows that the differences between the LMA and the cuffed tube compared with the uncuffed tube were clearly significant, although it must be stressed that the sample examined population was small and this constitutes an important criticity.
Fig. 17
45
RESULTS OF SYSTEMATIC REVIEW
The systematic analysis above reported allows us to list the following conclusions:
- It appears with a good level of evidence that the pediatric cuffed tracheal tube does not determine a greater extent of respiratory complications than the uncuffed one;
- The principle of non-use cuffed tubes to under 8 years of age may be a handed down "myth" of pediatric anesthesia, because its theoretical basis date back to ancient studies and they never underwent critical review;
- Recent publications radically change the actual anatomy of the child larynx, confirming with the evidence that it is high time that that "myth" should be deleted;
- The few authors who still take a stand against the use of cuffed tube in pediatrics do not support their belief with arguments "evidence-based" reporting publications of lesser quality (case reports), dated and poorly documented;
- Paradoxically, it seems most likely that the presence of lesions related to intubation is due to the lack of cuff in the tracheal tube; - A major criticity is the low number of prospective randomized controlled trials, which does not allow a quantitative assessment to date in the form of meta-analysis and hopes additional trials on the argument;
- Another critical issue is represented by the large age range, and therefore by the high variability in the anatomical and functional characteristics, which frequently appears in the studied population; - The central aspect, represented by the stability of cuffed tracheal tube makes it almost logical some of the studied outcomes, such as reducing the risk of aspiration and environmental pollution; for this reason, it does not seem to need more specific studies;
- Improvements of cuffed tubes design gradually achieved certainly contributed in reducing the risk of complications associated with the use of cuffed tracheal tube in pediatric patients.
46
CLINICAL RESEARCH: PROSPECTIVE STUDY
For about 20 years there has been a gradual change in the practice of pediatric anesthesiologists with an increasing trend towards the use of cuffed tracheal tubes to replace the uncuffed ones. Previously, the standard clinical practice was represented by the use of uncuffed tracheal tubes up to 8 years of age. Lately, the improvements in design made cuffed tubes in children safer [66, 67, 68, 69]. The literature demonstrated many advantages in terms of low incidence of respiratory complications [35, 54, 55, 56, 57, 62, 44] and reduced economic costs because of the reduced consumption of anesthetic gases and substitutions of the tracheal tube consequent to excessive loss [64, 35, 55]. The fundamental aspect in the prevention of post-extubation respiratory complications is made from intracuff pressure monitoring in order to avoid excessive ischemic compression of ring cricoid and / or trachea [42, 80]. To our knowledge, there are no publications on the incidence of post-extubation complications in neurosurgical pediatric patients. The aim of this preliminary prospective observational study was to evaluate the incidence of post-extubation complications with the use of cuffed tracheal tubes in a pediatric population undergoing neurosurgery.
Methods
Intraoperative anaesthesiologic records of surgeries performed at the Pediatric Neurosurgery of the Azienda Ospedaliera-Universitaria Meyer, Firenze, from the 1st November 2015 to 28th February 2016 were analyzed, when intracuff pressure monitoring of tracheal tubes started. Exclusion criteria included congenital airways malformations, pre-existing or recent acute airway infections and the patient transfer to the ICU with the continuation of the tracheal tube stay.
The induction and maintenance of anesthesia was the same in the cases examined. The induction was performed with facial mask, in spontaneous ventilation with a mixture of O2 / air / sevoflurane inhaled, or intravenous propofol (2-3 mg / kg). Muscle relaxation was performed with rocuronium (0.6-1.2 mg / kg). For the choice of
47 the tube diameter Motoyama formula was used. The cuff is blown and "air leak" was tested. After fixing the tube and positioning the patient, the intracuff pressure was measured and noted with dedicated pressure gauge. A maximum cuff pressure of 20 mmHg was established. At this level, the "air leak" test is always negative. The choice of mechanical ventilation mode, both pressumetric and volumetric, was established according to the individual case and, where possible, with low flows (up to 0.7 l / min). The delivered gas mixture was always composed of O2 / sevoflurane without the addition of nitrous oxide. Analgesia was performed by continuous infusion of remifentanil at a variable speed depending on the type of intervention and the intraoperative stage. At the end of the surgery and after restart of spontaneous ventilation, maintaining sevoflurane concentration higher than the MAC awake, the intracuff pressure measuring was repeated and annotated. Then the tracheal tube was removed, checking and recording the presence of stridor. In case of post-extubation stridor, the patient was observed clinically until resolution of symptom. All patients were examined up to the moment of their discharge from the hospital.
Results
Fifty patients between the ages of 0 and 18 years were enrolled in the study. Tab. 16 shows the demographic and clinical data of the population and Tab. 17 shows the post-extubation complications. No patient with stridor required reintubation or drug treatment but spontaneous resolution in a maximum time of 13 minutes after onset was observed.
48 Tab. 16 - Demographic and clinical data
Age (y) (mean±ds + range) 5.7 ± 5.6 (0 – 18) Weight (kg) (mean±ds + range) 24.42 ± 20.30 (2 – 78) Gender M/F 34/16 Lenght of anesthesia (min) (mean±ds + range)
146.5 ± 95.723 (58 – 510)
Tab. 17 - Post-extubation complications
Subglottic stenosis 0
Stridor 4
Stridor after prone position
2
Patients age to whom stridor occurred
49
Discussion
Literature review on the use of cuffed tracheal tubes in pediatric patients found no case studies that were conducted on pediatric neurosurgical patients. This population presents clinical and procedural features that deserve dedicated analysis. The anesthesiological aspects, such as the ventilation techniques and gaseous agents used, the surgical aspects, such as for example the critical patient positioning on the operating table, and the age / weight of the patients can affect and influence the intubation manoevre.
A frequently observed aspect in enrolled pediatric populations is represented by the extreme age heterogeneity [51, 54, 60]. This represents an important bias because the conclusions are strongly influenced by this variable. Even in our study this aspect is highlighted, although stridor is almost exclusively present in the age group under 5 years.
Intracuff pressure is a very important parameter when cuffed tracheal tubes are used and its monitoring is considered the condition sine
qua non for the prevention of ischemic damage of the mucosa [79,
80]. According to that, the study of Felten et al [42] concluded that during anesthesia with nitrous oxide the intracuff pressure is unpredictable and that numerous desufflations are necessary to maintain pressure values below 25 mmHg. In our study intracuff pressure was measured: 1) after fixing the endotracheal tube; 2) after making the position on the operating table; 3) immediately before extubation.
In neurosurgical patients a proper monitoring of the intracuff pressure is impossible to perform, being no access to the patient's head during surgery. Nevertheless, we found no significant variations between the two measurements and it is therefore conceivable that intracuff pressure values remained constant even during surgery. An important technical aspect is that in neurosurgery is preferable to avoid the use of nitrous oxide which, for its physical characteristics, spreads in any empty cavities (pneumocephalus and cuff) and, for its
50 pharmacodynamic characteristics, tends to increase cerebral blood flow and O2 consumption and consequently intracranial pressure.
A further specificity caused by impossibility to gain access to the patient's head during a neurosurgical intervention is the absolute stability of the tube because of the risk of intraoperative accidental extubation, with letal consequences. Cuff reduces the movements and consequently also this risk.
In neuroanesthesia we use low flows mechanical ventilation, made possible thanks to the cuff seals which allow with high precision inspiratory and expiratory gases monitoring. This finding is in agreement with the literature [75].
Finally, the use of cuffed tubes enables additional benefits, already reported in the literature, consisting in the reduced consumption of gaseous agents, and consequently of economic costs [64] and environmental pollution [35, 55, 76].
CONCLUSIONS
We are aware that our study has some limitations. First, it is a prospective study with all the problems that this type of scientific study has. Second, the wide range of patients ages represents the main bias, although in common with the majority of publications. With this background, the study seems to allow to arrive at the following conclusions regarding the use of cuffed tracheal tube in pediatric patients undergoing brain surgery:
1) confirmation of the low incidence of post-extubation complications with the use of tracheal cuffed tube as reported in the literature;
2) cases of stridor were not so important to result in any treatment; 3) the absence of nitrous oxide in the gas mixture used for the maintenance of general anesthesia does not request to repeat intracuff pressure measurements during the surgery (moreover, it would not be possible because of the inaccessibility to the patient’s head;
51 4) other randomized controlled prospective studies are necessary, comparing cuffed endotracheal tubes and not, to further confirm the findings of our study.
52
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