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Keywords:

  • airway;
  • complications;
  • intubation;
  • airway devices;
  • equipment;
  • anomalies acquired;
  • anomalies congenital

Summary

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. Conflicts of interest
  9. References
  10. Appendix 1

Background

Airway alterations found after endotracheal intubation are usually associated with mechanical trauma from the tube. However, no studies are available concerning alterations in airways that have never been intubated before. It was the aim of the study to compare endoscopic findings in the larynx and trachea of children who had undergone prior endotracheal intubation with findings in children who had not been intubated before.

Methods

In 1021 children aged from 0 to 6 years, rigid endoscopies were performed before planned elective endotracheal intubation. The anonymized endoscopy videos were reviewed and graded by five international airway experts. Data was compared between the two groups using the chi-square test (P ≤ 0.05).

Results

Endoscopic records of 971 children (473 with prior intubation; 498 without prior airway intubation) were included in the final calculations. Most patients (93.7%) with prior intubation had been intubated with a cuffed tube. The number of intubations ranged from 1 to 27. The median interval between intubation and endoscopy was 0.53 years (0.003–5.57 years). Abnormal findings were observed in 31.7% and 26.8% of patients with and without prior intubation, respectively (P = 0.063). Glottic granulomas were significantly more common after intubation (3.6% vs 1.4%; P = 0.028). The incidence of other abnormal findings was similar in both groups.

Conclusion

Endoscopic airway alterations can be observed in about one-quarter of children presenting for routine surgery without prior intubation. Except for glottic granulomas, the abnormalities are found with similar frequency in patients with and without prior intubation. No relevant airway damage from short-term endotracheal intubation was found.


Introduction

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. Conflicts of interest
  9. References
  10. Appendix 1

Endotracheal intubation continues to be one of the most common procedures in children during anesthesia and intensive care. The mere fact that a plastic tube remains in the delicate larynx for hours or days and that this tube moves relative to the soft underlying mucosa already suggests possible traumatization or alteration.

Increased risks of alteration must be expected with traumatic or repeated intubation and with oversized tubes or overinflated cuffs [1-3]. Despite this, postextubation stridor, indicating laryngeal (subglottic) edema, is quite rare and usually transient when correctly sized tubes are used and cuff pressures are carefully controlled [4, 5].

Long-term airway alteration after endotracheal intubation and ventilation can be observed, although infrequently, in patients who have been ventilated in a critical condition in intensive care. After intubation for anesthesia, long-term symptoms in children are almost completely absent [6]. In adults, some endoscopic studies have been carried out immediately after extubation, providing some information about the irritating and damaging effect of endotracheal intubation on the larynx [7, 8]. In children, to our knowledge, endoscopic studies have only been performed when persistent stridor or airway obstruction was present after extubation [2, 9]. As systematic endoscopic data on airways that have never been intubated before has not been available to date, the relevance of some of the alterations that can be seen endoscopically is questionable. Frequent upper airway infections in young children also induce mucosal reactions but have not been studied by means of endoscopy so far. Some minor congenital malformations remain symptomless and are only seen by chance. Thus, the aim of this study was to examine and compare larynx and trachea of symptomless children with and without prior endotracheal intubation.

Methods

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. Conflicts of interest
  9. References
  10. Appendix 1

With Ethics Committee Approval (KEK StV 24/08) and written parental consent, children aged 0–6 years were included in a prospective, observational, blinded clinical study. Inclusion criteria were elective general anesthesia with planned tracheal intubation and muscle paralysis. Patient groups were defined as prior single or multiple tracheal intubations [group T (tube) – intended 500 patients] performed at our institution or absence of any prior laryngotracheal airway instrumentation in the past [group N (normal; no tube; no airway instrumentation) – intended 500 patients]. Exclusion criteria were a known difficult or abnormal airway, actual stridor, emergency anesthesia, patient at risk for regurgitation, ASA physical status class >III, and patients with cervical spine problems including Down's syndrome. Premedication and induction of anesthesia were performed in all patients according to the clinical treatment protocol of the Department of Anaesthesia, University Children's Hospital, Zurich.

Rigid laryngotracheoscopies were performed by one of the two investigators (Weiss/Gerber) blinded to patient history and not involved in the patient's anesthetic management. Direct laryngoscopy was performed in the preoxygenated, anesthetized, paralyzed and conventionally monitored patient (NIBP, ECG, SpO2) patient. A rigid endoscope (0°, 3.0 mm, 30 cm, Karl Storz 7200 A, 8700B, GmbH, Germany) was then carefully guided through the larynx down to the carina and back again under monitored vision. The entire endoscopic examination was recorded. If airway secretions obstructed the endoscopic view, laryngotracheal suction was performed, the patient again fully oxygenated and the endoscopic procedure completed. Suctioning was noted on the patient's record. After the examination and further oxygenation, the trachea was intubated with an appropriately sized tube.

Demographic and anesthesia-related data [age, gender, type of tracheal tube (cuffed or uncuffed), number of intubations, and interval since last intubation] were noted.

The recorded endoscopy videos were reviewed and graded by an International Study Board Committee consisting of 5 pediatric airway experts (authors 3–7) according to a grading list (Appendix 1). The assessors were blinded to the nature of the group and the medical history with the exception of age and gender of the patient investigated. Pathological findings such as nodules, ulceration, granulations, cysts, follicles, stenosis, and malacia were graded at the level of the glottis, subglottis, trachea, carina, and main bronchi as appropriate. Endoscopic findings with different grading among the experts were discussed and adjusted after coming to a final consensus among the five experts. Data was compared between the two groups using Student's t-test or the Mann–Whitney U-test and chi-square test.

Results

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. Conflicts of interest
  9. References
  10. Appendix 1

In total, 1021 (521 in group T; 500 in group N) rigid endoscopic examinations were performed and assessed in children aged from 0 to 6 years. Four patients were excluded by the experts because the endoscopic records were of insufficient quality, and another 46 patients in group T had to be excluded because review of subsequently available anesthesia records revealed that a supraglottic airway instead of an endotracheal tube had been used.

Eventually, the endoscopic findings of 971 children (473 in group T; 498 in group N) were included in the final calculations. Epidemiological and anesthetic data for the studied patients are presented in Table 1.

Table 1. Epidemiological and anesthetic data
 Group TGroup N
  1. Group T = Patients with prior endotracheal intubation(s).

  2. Group N = Patients without prior airway intubation.

  3. a

    P < 0.05

  4. b

    P < 0.01

  5. c

    P < 0.001 Data in median (range).

Patients (n)473498
Age (years)2.79 (0.1–6.0)2.22 (0.01–6.0)b
ASA Status II/III184/60109a/8c
Gender (m/f)286/187339/159
Total number of intubations

1017

1 (0–27)

-
Duration since last intubation (years)0.526 (0.003–5.57)-
Duration of previous intubations (min)149 (22–23,040)-
Cuffed tubes only443-
Uncuffed and cuffed tubes20-
Uncuffed tubes only10-

There was no significant difference in the gender distribution between groups T and N. Children in group T were slightly older than in group N (median age, 2.79 and 2.22 years; range, 0.1–6.0 and 0.01–6.0 years, respectively, P < 0.01). Patients in group T compared with group N had significantly higher ASA status (60 pts with ASA 3 in group T compared with 8 pts in group N) (P < 0.0001).

Most patients (443 of 473) had been intubated with a cuffed endotracheal tube. In 20 (4.2%) patients, cuffed and uncuffed tubes had been used, and in 10 patients (2.1%), only uncuffed tubes had been used for securing the airway. Some of the patients had been intubated several times. The 443 patients in group T had 1017 prior tracheal intubations. The number of intubations ranged from 1 to 27 (median, 1; Figure 1). Median duration of the 1017 previous endotracheal intubation in the group T was 149 min (22–23′040 min). Seventeen of the 473 patients in group had 21 long-term intubations (duration >24 h). Median duration of long-term intubation was 2 days (1–16 days). The median time interval between the endoscopy and the last intubation was 0.526 years, with a range from 0.003 to 5.57 years.

image

Figure 1. Number of previous intubations.

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In the group with prior intubation (T), abnormal findings were recorded in 150 of 473 patients (31.7%), and in the group without prior intubation (N), in 131 of 498 patients (26.8%) (P = 0.063). Endoscopic findings are listed in detail in Table 2. Typical endoscopic pictures of the abnormal findings are shown in Figure 2. Various degrees of these abnormal endoscopic findings in different patients can be seen as video sequences at www.kindernarkose.ch/endoscopy.htm.

Table 2. Endoscopic airway findings
 Group TGroup N
  1. Group T = Patients with prior endotracheal intubation(s).

  2. Group N = Patients without prior airway intubation.

  3. a

    P < 0.05.

Patients473489
Patients with findings150 (31.7%)131 (26.8%)
Total findings182153
Glottic
Ulceration1 (0.2%)0 (0%)
Granuloma17 (3.6%)7 (1.4%)a
Nodules44 (9.3%)37 (7.6%)
Cysts4 (0.9%)2 (0.4%)
Stenosis1 (0.2%)0 (0%)
Subglottic
Ulceration0 (0%)0 (0%)
Granuloma1 (0.2%)0 (0%)
Cysts8 (1.69%)3 (0.6%)
Follicles76 (16%)81 (16.5%)
Stenosis0 (0%)0 (0%)
Trachea
Ulceration0 (0%)0 (0%)
Granuloma2 (0.4%)0 (0%)
Stenosis0 (0%)0 (0%)
Tracheomalacia <50%19 (4%)19 (3.8%)
Tracheomalacia a > 50%6 (1%)2 (0.4%)
Carina
Ulceration0 (0%)0 (0%)
Granuloma0 (0%)0 (0%)
Stenosis0 (0%)0 (0%)
Main Stem Bronchus R
Granuloma0 (0%)0 (0%)
Bronchomalacia <50%1 (0.2%)0 (0%)
Bronchomalacia >50%1 (0.2%)1 (0.2%)
Main Stem Bronchus L
Granuloma0 (0%)0 (0%)
Bronchomalacia <50%1 (0.2%)0 (0%)
Bronchomalacia >50%0 (0%)1 (0.2%)
image

Figure 2. (a) Endoscopic findings of airway alterations at the glottic and subglottic level. (b) Endoscopic findings of airway alterations at the level of the trachea and the main stem bronchi.

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At glottic level, granulomas, vocal cord nodules and cysts were the most common pathologies found in both groups with a significantly higher incidence of granulomas in group T (P = 0.028), when including long- and short-term intubation (Figure 3). One mild glottic stenosis and one healed ulcer were found in the group T.

image

Figure 3. Endoscopic images of glottic granulomas. Group T = patients with prior intubation (n = 17)/Group N = patients without prior airway intubation (n = 7).

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At subglottic level, follicular hyperplasia and cysts were often found in both groups. Follicular hyperplasia with a ‘cobblestone’ appearance was seen very frequently, mostly extending to some degree into the trachea. The incidence of these findings did not differ between groups. No subglottic stenosis or large cysts were recorded.

Tracheomalacia with <50% narrowing was similarly found in both groups. Severe malacia (>50% narrowing) was recorded in five patients in group T and two patients in Group N. Details of these patients including their medical history are presented in Table 3. A tracheal bronchus was found in 11 patients (1.1%).

Table 3. Patients with severe malacia (> 50% narrowing) of the trachea and/or main stem bronchus left/right
Patient groupAge (years)Malacia locationGenderASA statusDuration since last Intubation (years)Number of prior intubationsDetailed patient history
T2.6TracheaM21.88Neonatal meningitis with hydrocephalus. Posted for ventriculoperitoneal (vp) shunt revision.
T2.7TracheaF10.42

Premature (35 weeks of gestation).

Posted for orchidopexy operation.

T0.8TracheaM36 days2

Myelomeningocele.

Posted for revision of vp shunt.

T0.6TracheaF30.22

Premature born at 33 weeks, VACTERL association. esophageal atresia with tracheo-esophageal fistula. Tetralogy of Fallot – repaired.

Posted for cleft lip repair.

T1.5Bronchus rightM20.21

Atrial septal defect repair.

Posted for cleft palate repair.

T0.5TracheaM20.41Cerebral malformation with vp shunt. Posted for revision of shunt.
N4.0TracheaF1-0Posted for strabismus surgery.
N0.7Trachea and Bronchi bilateralM1-0Posted for penile surgery.

Patients with ASA physical status III demonstrate a significantly higher incidence of glottic granuloma (P = 0.007), glottic cysts (P = 0.011), and tracheomalacias (P < 0.0001). Similarly, patients with prior prolonged intubation revealed a significantly higher incidence of glottic granulomas (P = 0.0015) and glottic cysts (P = 0.02) compared to patients with short-term intubation. When comparing glottic granuloma between only short-term intubated patients and nonintubated patients, there was no longer a statistically significant difference (P = 0.069).

We found a higher incidence of subglottic cysts in patients with prior mixed cuffed and uncuffed tubes when compared to patients who had only cuffed tubes in previous intubations (10% versus 1.12%). Patients who had prior intubations with uncuffed tubes only had higher incidence of subglottic cysts compared to patients with prior cuffed tubes only (20% versus 1.14%; P = 0.00001).

Discussion

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. Conflicts of interest
  9. References
  10. Appendix 1

This study investigated the pediatric airway in 971 patients with and without prior airway intubation using rigid endoscopy of the larynx and trachea before routine endotracheal intubation. The videos of the endoscopies were reviewed and graded by five international pediatric airway experts. To allow the reader to see the abnormal findings, photographs of typical abnormal findings are presented.

The main finding is that airway abnormalities can be found endoscopically in about 25% to 30% of children presenting for routine surgery, irrespective of whether the airway has been intubated before or not. Only glottic granulomas were significantly more common in children who had been intubated before, particularly in long-term intubation patients. Follicular hyperplasia and cysts were the most common findings in the subglottic area. No major ulceration, relevant subglottic stenosis or major mucosal retention cysts were found.

This systematic endoscopic study in previously intubated pediatric patients does not support the continuing concern [2, 10-12] that significant laryngotracheal damage is caused by endotracheal tubes, especially by cuffed endotracheal tubes.

It must be remembered that the main reasons for intubation-related airway trauma in children are traumatic intubation and oversized tracheal tubes including cuff hyperinflation [1, 2]. Almost all patients (96.4%) of Group T were previously intubated for short periods in this study. They had all a correctly sized tube (air leakage latest at 20 cm H2O airway pressure), and the cuff pressure was controlled to ≤20 cm H2O in accordance with departmental guidelines. Subglottic stenosis, a well-documented and frequent consequence of intubation with oversized tubes, was not found in a single patient in our study. Mild glottic stenosis was found in a single asymptomatic patient in group T (Figure 2). Congenital stenosis prior to intubation cannot be ruled out in this patient.

Massive subglottic mucosal retention cysts have been described as a consequence of endotracheal intubation in neonates [13, 14]. No large cysts were found in our study. Minor cysts seem to be a usual finding, because they were also seen in nonintubated children [15].

The incidence of glottic, subglottic as well as tracheal pathology is higher in patients with ASA physical status III, prior prolonged intubation and the use of uncuffed tracheal tubes. Patients with higher ASA classes have co-morbidities and often prolonged postoperative intubation periods, which may explain these findings. Whether prolonged intubation is a risk factor for laryngeal damage is still undetermined [16-19]. Larger populations are required to define its impact on airway pathologies.

The finding that patients with prior intubation with an uncuffed tube had a higher incidence of subglottic cysts can be explained by pressure injury due to their larger outer diameter compared with cuffed tracheal tubes. In this regard, the selection of a smaller cuffed tracheal tube and sealing the airway within the trachea with a cuff seems to be of advantage compared with sealing the pediatric airway within the susceptible larynx with a larger uncuffed tracheal tube [20].

The high incidence of follicular hyperplasia can probably be explained by the very liberal attitude of our institute to anesthetizing children with a common cold. Although follicular hyperplasia is a common finding in pneumonology, however, there is no clear evidence about its pathogenesis. Most often it is associated with respiratory tract infection or gastro-esophageal reflux.

A similar degree of mild tracheomalacia [21] was found in both groups. Severe tracheomalacia (>50% narrowing) was more frequent but not statistically significant in group T (six versus two patients); however, five of these six patients in group T also had other congenital abnormalities (Table 3).

Usually endoscopy is performed only with the aim of confirming or excluding a suspected specific pathology. This study shows that minor alterations or abnormalities without pathological significance are quite common in normal children. These may be normal variants or secondary to common respiratory infections and have no consequences. The study also demonstrates that relevant airway trauma should not be expected after short-term intubation when correctly sized tubes are used for and cuff pressures are properly controlled.

The limited number of endoscopies in normal children, the small number of prolonged intubations, and the few patients with uncuffed tubes do not allow general statements about the incidence of abnormal findings and variants in these categories. The variable time interval between intubation and endoscopy in our study obscures temporary lesions. Because of missing follow-up endoscopies, statements about the healing processes are not possible. As most of the children in this study had only been intubated for a relatively short period, airway trauma from long-term endotracheal intubation cannot be excluded from our data and this question needs further studies.

In conclusion, endoscopic airway abnormalities can be observed in about one-quarter of children presenting for routine surgery without prior intubation. Except for glottic granulomas, the incidence of abnormalities found in young children with and without prior intubation was similar. No relevant airway damage from short-term endotracheal intubation was found.

References

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. Conflicts of interest
  9. References
  10. Appendix 1

Appendix 1

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. Conflicts of interest
  9. References
  10. Appendix 1

Endoscopy Study Assessment Form

Glottis
Ulceration□ No □ Yes [RIGHTWARDS ARROW]
Granuloma□ No □ Yes [RIGHTWARDS ARROW] □ <75% obstructive □ >75% obstructive
Nodules□ No □ Yes
Cysts□ No □ Yes
Stenosis□ No □ Yes [RIGHTWARDS ARROW] □ <25% □ 25–49% □ 50–90% □: >90%
Comments: 
Subglottis
Ulceration□ No □ Yes [RIGHTWARDS ARROW]
Granuloma□ No □ Yes [RIGHTWARDS ARROW] □ <75% obstructive □ >75% obstructive
Cysts□ No □ Yes
Follicles□ No □ Yes
Stenosis□ No □ Yes [RIGHTWARDS ARROW] □ <25% □ 25–49% □ 50–90% □: >90%
Comments: 
Trachea
Ulceration□ No □ Yes [RIGHTWARDS ARROW]
Granuloma□ No □ Yes [RIGHTWARDS ARROW] □ <75% obstructive □ >75% obstructive
Stenosis□ No □ Yes [RIGHTWARDS ARROW] □ <25% □ 25–49% □ 50–90% □: >90%
Malacia□ No □ Yes [RIGHTWARDS ARROW] □ <50% Narrowing □ >50% Narrowing
Comments: 
Carina
Ulceration□ No □ Yes [RIGHTWARDS ARROW]
Granuloma□ No □ Yes [RIGHTWARDS ARROW] □ <75% obstructive □ >75% obstructive
Stenosis□ No □ Yes [RIGHTWARDS ARROW] □ <25% □ 25–49% □ 50–90% □ >90%
Comments: 
Left Main Stem Bronchus
Granuloma□ No □ Yes [RIGHTWARDS ARROW] □ <75% obstructive □ >75% obstructive
Malacia□ No □ Yes [RIGHTWARDS ARROW] □ <50% Narrowing □ >50% Narrowing
Right Main Stem Bronchus
Granuloma□ No □ Yes [RIGHTWARDS ARROW] □ <75% obstructive □ >75% obstructive
Malacia□ No □ Yes [RIGHTWARDS ARROW] □ <50% Narrowing □ >50% Narrowing
Comments: