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\begin{document}

\title{Is secondary tracheomalacia associated with persistent lower respiratory
tract inflammation and subclinical infection?}



\author[1]{Antonino Capizzi}%
\author[1]{Michela Silvestri}%
\author[2]{Giovanni Rossi}%
\author[1]{Oliviero Sacco}%
\affil[1]{Istituto Giannina Gaslini}%
\affil[2]{G. Gaslini Institute}%


\vspace{-1em}



  
  \date{May 26, 2024}


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\selectlanguage{english}
\begin{abstract}
Background. In secondary tracheomalacia due to mediastinal vascular
anomalies one of the most prevalent symptom is recurrent lower
respiratory tract (LRT) infections, related to defective airway
clearance. Whether this condition could result in persistent LRT
inflammation and subclinical infection is not known. Patients and
methods. Children with tracheomalacia due to mediastinal vascular
anomalies, recurrent (\textgreater{}3/y) LRT infections were evaluated
while in stable condition. Computed tomography (CT) scan and
bronchoscopy with bronchoalveolar lavage (BAL) were performed. Results.
31 children were included in the study: 21 with aberrant innominate
artery (AIA), 4 with right aortic arch (RAA) and 1 with double aortic
arch (DAA) and 5 with AIA associated with RAA. Cytological evaluation of
BAL fluid showed increased neutrophil percentages and normal lymphocyte
and eosinophil proportions. Microorganism growth was detected in 35.5\%
of BAL samples, with a bacterial load \textgreater{}105
colony-forming-units (CFU)/mL only in 10,2\% of them. Most isolates were
positive for Haemophilus influenzae, followed by Streptococcus
pneumoniae, Group A \selectlanguage{greek}β-\selectlanguage{english}hemolytic streptococci and Moraxella catarrhalis.
Chest CT scan demonstrated the presence of bronchiectasis in 13\% of the
children, of which only one had a positive BAL culture for Haemophilus
influenzae. Conclusions. Only in a small subgroup of children,
persistent neutrophilic alveolitis was associated with a significant
bacterial load and the presence of bronchiectasis. Because most
pathogens detected in BAL samples cultures can produce biofilms, caution
should be used in inappropriate antibiotic prescription in these
patients that, chiefly in those with bronchiectasis, in which chest
physiotherapy can be of great benefit.%
\end{abstract}%



\sloppy


\textbf{INTRODUCTION}

An uncommon, but potentially serious, cause of respiratory disorders in
childhood is represented by the extrinsic tracheal compression due to
congenital vascular anomalies within the mediastinum {[}1{]}. The most
severe forms are usually diagnosed during the neonatal period, while the
less severe forms can be detected later in life, when unexplained
chronic or recurrent respiratory symptoms, or occasional mild dysphagia,
lead to endoscopic evaluations. In two retrospective studies we found
that the most prevalent respiratory symptoms associated with this
condition were chronic cough, poorly responsive to therapy, and
recurrent lower respiratory tract infections (LRTI) {[}2,3{]}. In the
absence of known comorbidities, these symptoms are often misdiagnosed as
asthma, non-specific bronchial hyperreactivity and/or gastroesophageal
reflux and inappropriate prescription of anti-asthmatic drugs and/or
antibiotics often occurs {[}3,4{]}. The generation of cough in these
children is thought to be induced by mechanical sensory inputs, through
rapidly adapting mechanoreceptors {[}3,5{]}. The recurrence of LRTI in
these otherwise healthy children is believed to be related to the
dynamic collapse of the airway lumen, associated with malacia, that
reduces cough effectiveness and interferes with mucociliary clearance
{[}6-8{]}. Under-recognition and under-treatment of subclinical
protracted bacterial infections may lead to the development of chronic
suppurative lung disease and bronchiectasis {[}8{]}. With this
background a retrospective study was performed to evaluate whether
tracheal malacia, secondary to abnormal mediastinal vessels, is
associated with persistent lower respiratory tract inflammation and
infection.

\textbf{MATERIALS AND METHODS}

\textbf{Study population}

A retrospective study was performed on records of patients referred to
the Gaslini Institute because of recurrent/chronic cough and found to
have tracheomalacia associated with mediastinal vascular anomalies.

They all had history of recurrent LRTI (\textgreater{}3/y) treated with
antibiotics but were evaluated while in stable condition, at least four
months after the last infection. We excluded children presenting other
congenital anomalies or malformations, swallowing disorders, primary
ciliary dyskinesia, cystic fibrosis and immunodeficiencies.

\textbf{Patient evaluation}

Demographic data were collected, and physical examination, routine blood
tests were performed in all patients. Children underwent additional
investigation and consultations, when clinically indicated by the
presence of ``specific cough pointers'' {[}9{]}. Diagnosis of tracheal
compression by mediastinal vascular abnormalities was diagnosed in all
patients by flexible bronchoscopy and chest computed tomography with
radiocontrast agents.

\textbf{Fiberoptic bronchoscopy and bronchoalveolar lavage (BAL)}

Fiberoptic bronchoscopy was performed in sedation, with the patient
spontaneously breathing but ventilation was assisted manually, when
needed. The video bronchoscopes (Olympus BF-XP190, BF-3C160 or BF-P190)
were introduced through a face mask in a nostril, as described elsewhere
{[}3{]}. The presence and the characteristics of tracheal narrowing, in
inspiration and expiration or during cough, was evaluated during
bronchoscopy and reassessed playing back the session videotape. BAL was
performed by injecting 3\selectlanguage{ngerman}×1 ml/kg body weight aliquots of sterile saline
solution, which were aspirated at a negative pressure of

40mm Hg in siliconized plastic tubes. Samples of BAL fluid was sent to
the laboratory for microbiologic and cytologic examination and total and
differential cell counts were recorded as described {[}10{]}. Bacterial
growth was expressed as colony-forming units (CFU)/mL.

\textbf{Computed tomography (CT)}

Multidetector CT was performed with a 64-slice CT scanner (Siemens
Somatom Sensation 64, Siemens, Erlangen, Germany) {[}11{]}. The
intravenous contrast agent (Iomeron 300, Bracco, Milan, Italy) was
administered, in all patients, with a power injector via a peripheral
vein, and when possible, the examination was performed with breath
holding at suspended inspiration, but in younger and noncooperative
patients, quiet breathing was tolerated. CT images were interpreted
without knowledge of the bronchoscopic findings.

\textbf{Data analysis}

Descriptive statistics were performed and reported in terms of absolute
frequencies or percentages for qualitative data and expressed as mean
with standard deviation in parenthesis or in terms of medians, with
lower and upper quartiles in brackets, for quantitative data.
Comparisons between BAL data in tracheomalacia children and reference
values were performed using Mann U Whitney. Data were analysed using
``Statistica release eight'' (StatSoft Corp., Tulsa, OK), and a
difference of \emph{P} value less than 0.5 was considered as
statistically significant

\textbf{RESULTS}

31 children, 15 males and 16 females, mean age at time of referral of
5.64\emph{+} 3.62 years, were included in the study. In all children
fiberoptic bronchoscopy demonstrated the presence of pulsatile extrinsic
compression of the trachea middle third, leading to different degree of
narrowing that increased in expiration and, more, during coughing
(figure 1). Mucus/mucopurulent secretions and various degree of
congestion and edema of the airway mucosa were revealed. Chest CT scans
demonstrated the presence of aberrant innominate artery (AIA) in 21
children, right aortic arch (RAA) in 4 children, double aortic arch
(DAA) in 2 child and AIA associated with RAA in 5 children (figure 2).
Analysis of BAL cells demonstrated a significant difference in total
cell numbers, corrected per milliliter of BAL fluid recovered {[}92.03
(70.15-481.39) cells \selectlanguage{greek}µ\selectlanguage{english}L\textsuperscript{-1}{]}, compared to control
values in our laboratory {[}132.15 (35.15-290.74) cells
\selectlanguage{greek}µ\selectlanguage{english}L\textsuperscript{-1}; p\textless{}0.01{]}. A neutrophilic alveolitis
was detected, with 21.50 (10.55-66.10) neutrophil proportion, compared
to control values of 1.70\% (0.60--3.50) (p\textless{}0.01), but with
normal lymphocyte and eosinophil counts (figure 3). Microbiological
analysis of BAL fluid demonstrated bacterial growth in 35.5\% of the
children, but with a pathogen load\emph{\textgreater{}}
10\textsuperscript{5} colony-forming units (CFU)/mL only in 10,2\% of
them. In these cultures, 72.7\% of the isolates were\emph{Haemophilus
influenzae} , 27.3\% \emph{Streptococcus pneumoniae}and, 9.0\% each for
Group A \selectlanguage{greek}β-\selectlanguage{english}hemolytic streptococci (GABHS) and\emph{Moraxella catarrhalis}
(figure 4). Coinfection were present in two isolated, one being positive
for \emph{Haemophilus influenzae} plus SBEGA and the other for
\emph{Haemophilus influenzae} plus \emph{S. pneumoniae} . BAL
neutrophilia tended to be higher in children with bacterial load
\textgreater{}10\textsuperscript{3} CFU/mL (figure 5). Finally, chest CT
scan demonstrated the presence of bronchiectasis in 13\% of the
children, 5.9+2.2 years old, of which one had a positive BAL culture
(\textgreater{}10\textsuperscript{4} CFU/mL) for

\emph{Haemophilus influenzae.}

\textbf{DISCUSSION}

In this retrospective study we have shown that a significant
inflammatory reaction at airway level is present in children with airway
malacia due to mediastinal vascular anomalies and recurrent respiratory
symptoms. A significant neutrophilic alveolitis was detectable by
bronchoalveolar lavage thought the procedure was performed when children
were in well-being conditions, at least four months after the last
respiratory infection. Additionally, microbiological analysis of BAL
fluid demonstrated bacterial growth in more than one third of them, but
with a pathogen load \emph{\textgreater{}} 10\textsuperscript{5} CFU/mL
only in a small proportion. \emph{Haemophilus influenzae} was the
pathogen most frequently isolated. In a total of 512 bronchoscopies,
airway malacia was diagnosed in 160 children (94 males) at a median age
of 4.0 years (range, 0 to 17 years). Airway malacia is not a rare
condition in the general paediatric population, as reported by Boogaard
and co-workers {[}12{]}. Out of total of 512 bronchoscopies performed in
children with a median age of 4.0 years, 160 cases of airway malacia
were detected and classified as primary in 136 cases and secondary in 24
cases {[}12{]}. Airway malacia, inducing a dynamic collapse of the
airway lumen, reduces cough effectiveness and interferes with
mucociliary clearance, favoring airway plugging by bronchial secretions
and possibly bronchiectasis formation {[}13{]}. Moreover, in a study in
which bronchoscopy was performed to exclude other wheezing diseases in
children with ``severe chronic asthma'' (likely including a group with
airway malacia), Fayon M and co-workers, showed lower airway
neutrophilia and infection (\textgreater{}10\textsuperscript{4} CFU/mL)
with \emph{Haemophilus influenzae} detectable in 39.5\% of BAL cultures
{[}14{]}. Chronic wet cough, evidence of bronchitis at bronchoscopy and
airway neutrophilic inflammation are the hallmark of protracted
bacterial bronchitis (PBB) {[}15{]}. In the first study defining this
disorder, Chang AB and co-workers reported that trachea-bronchomalacia
was found in 33\% of children with chronic cough and BAL cultures in PBB
group were positive in 47\% of samples for \emph{Haemophilus influenzae}
, in 35\% for \emph{Streptococcus pneumoniae} and in 26\%
for\emph{Moraxella catarrhalis} {[}16{]}. More than one organism grew in
a significant number of PBB patients and 48\% of the children had a
positive clinical response to 14 days of amoxicillin clavulanate (22.5
mg/kg/dose, b.i.d.) {[}16,17{]}. In a follow-up study, Chang AB group
evaluated the 2-year outcomes of 161 PBB children {[}18{]}. They found
that a great proportion of them (43.5\%) had more than three episodes of
bacterial bronchitis per year, and 8.1\% were diagnosed with
bronchiectasis (vs the 13\% of our patient group)
{[}18{]}.\emph{Haemophilus influenzae} infection was demonstrated in BAL
fluid of 85\% of children with bronchiectasis and of 49\% of children
without bronchiectasis. Recurrent PBB episodes and high
\emph{Haemophilus influenzae} titers in BAL fluid were major risk
factors for bronchiectasis at 2 years follow-up, suggesting a role of
this specific infection in bronchiectasis pathogenesis {[}18{]}. In our
patient group, 72.7\% of the isolates were \emph{Haemophilus influenzae}
positive but only one child with bronchiectasis had a positive culture
for\emph{Haemophilus influenzae.} Through its ability to form
biofilms,\emph{Haemophilus influenzae} is a chief bacterial pathogen
associated with chronic respiratory disorders {[}19{]} and subinhibitory
concentrations of beta-lactam antibiotics may promote its transformation
into the biofilm phenotype, favoring antibiotic resistance and increased
susceptibility to reinfection {[}20{]}. In randomised controlled trial
in children with chronic wet cough it was reported that many of the
children whose symptom was not cured by 2 weeks of amoxicillin
clavulanate had underlying tracheo-bronchomalacia and needed a longer
treatment duration before their cough disappeared {[}15,21{]}.
Therefore, in view of high frequency of positive isolates
for\emph{Haemophilus influenzae} but also of the general low bacterial
load and the significat coesistence of bronchiectasis, caution should be
used in inappropriate antibiotic prescription in patients with secondary
airway malacia and recurrent respiratory infections. This approach may
be chiefly important in children with bronchiectasis, in which chest
physiotherapy can be of great benefit {[}22{]}. When possible,
antibiotics should be chosen on the basis of sputum or cough-swab
culture and sensitivity, adherence to treatment should be monitored and
the opportunity to switch from twice to thrice daily administration or
to increase the dosage should be taken in consideration in specific
cases to lengthen the time at higher minimum inhibitory concentration
levels {[}15{]}.

\textbf{References}

1. McLaren CA, Elliott MJ, Roebuck DJ. Vascular compression of the
airway in children. Paediatr Respir Rev 2008;9:85--94.

2. Gardella C, Girosi D, Rossi GA, Silvestri M, Tom\selectlanguage{ngerman}à P, Bava G, Sacco O.
Tracheal compression by aberrant innominate artery: clinical
presentations in infants and children, indications for surgical
correction by aortopexy, and short- and long-term outcome. J Pediatr
Surg. 2010;45:564-73.

3. Ghezzi M, Silvestri M, Sacco O, Panigada S, Girosi D, Magnano GM,
Rossi GA. Mild tracheal compression by aberrant innominate artery and
chronic dry cough in children. Pediatr Pulmonol. 2016;51:286-94.

4. Chang AB, Glomb WB. Guidelines for evaluating chronic cough in
pediatrics. ACCP evidence-based clinical practice guidelines. Chest
2006;129:260S--283S.

5. Widdicombe JG. Neurophysiology of the cough reflex. Eur Respir J
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6. Carden KA, Boiselle PM, Waltz DA, Ernst A. Tracheomalacia and
tracheobronchomalacia in children and adults: an in depth review. Chest
2005;127:984e1005

7. Chang AB, Redding GJ, Everard ML. Chronic wet cough: Protracted
bronchitis, chronic suppurative lung disease and bronchiectasis. Pediatr
Pulmonol. 2008;43:519-31.

8. Verhagen LM, de Groot R. Recurrent, protracted and persistent lower
respiratory tract infection: A neglected clinical entity. J Infect.
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9. Chang AB, Phelan PD, Sawyer SM, Robertson CF. Airway
hyperresponsiveness and cough-receptor sensitivity in children with
recurrent cough. Am J Respir Crit Care Med 1997;155:1935-1939.

10. Sacco O, Silvestri M, Ghezzi M, Capizzi A, Rossi GA. Airway
inflammation and injury in children with prevalent weakly acidic
gastroesophageal refluxes. Respir Med. 2018;143:42-47.

11. Sacco O, Santoro F, Ribera E, Magnano GM, Rossi GA. Short-length
ligamentum arteriosum as a cause of congenital narrowing of the left
main stem bronchus. Pediatr Pulmonol. 2016;51:1356-1361.

12. Boogaard R, Huijsmans SH, Pijnenburg MW, et al. Tracheomalacia and
bronchomalacia in children: incidence and patient characteristics. Chest
2005;128:3391--3397.

13. Santiago-Burruchaga M, Zalacain-Jorge R, Vazquez-Cordero C. Are
airways structural abnormalities more frequent in children with
recurrent lower respiratory tract infections? Respir Med.
2014;108:800-5.

14. Fayon M, Just J, Thien HV, et al. Bacterial flora of the lower
respiratory tract in children with bronchial asthma. Acta Paediatr
1999;88:1216-1222.

15. Chang AB, Upham JW, Masters IB, Redding GR, Gibson PG, Marchant JM,
Grimwood K. Protracted bacterial bronchitis: The last decade and the
road ahead. Pediatr Pulmonol. 2016;51:225-42.

16. Marchant JM, Masters IB, Taylor SM, Cox NC, Seymour GJ, Chang AB.
Evaluation and outcome of young children with chronic cough. Chest.
2006;129:1132-41.

17. Wurzel DF, Marchant JM, Yerkovich ST, Upham JW, Mackay IM, Masters
IB, Chang AB. Prospective characterization of protracted bacterial
bronchitis in children. Chest. 2014;145:1271-1278.

18. Wurzel DF, Marchant JM, Yerkovich ST, et al. Protracted bacterial
bronchitis in children: natural history and risk factors for
bronchiectasis. Chest. 2016;150:1101-1108.

19. Sacco O, Capizzi AF, Silvestri M, Rossi GA. Recurrence of Protracted
Bacterial Bronchitis in Children: What Can We Do? Chest. 2017;151:940.

20. Wu S, Li X, Gunawardana M, Maguire K, et al. Beta-lactam antibiotics
stimulate biofilm formation in non-typeable Haemophilus influenzae by
up-regulating carbohydrate metabolism. PLoS One. 2014;9:e99204.

21. Marchant J, Masters IB, Champion A, Petsky H, Chang AB. Randomised
controlled trial of amoxycillin clavulanate in children with chronic wet
cough. Thorax. 2012;67:689-93.

22. Chang AB, Marchant JM. Protracted bacterial bronchitis is a
precursor for bronchiectasis in children: myth or maxim? Breathe
(Sheff). 2019;15:167-170.

\textbf{Figure legends}

Figure 1. CT scan and bronchoscopic images of a 9 years old child with
extrinsic tracheomalacia due to compression by aberrant innominate
artery. A. CT scans show the anomalous course of the innominate artery
(white arrows) that causes an extrinisic compression on the tracheal
wall inducing the

reduction of the tracheal caliber (asterisk). B. Bronchoscopic image in
quiet breth showing the significant reduction tracheal caliber due both
to the extrinisic compression and the bulging of the posterior
membranous wall. C. Bronchoscopic image during coughing, showing
collapse of the tracheal walls and the almost complete obstruction of
the lumen.

Figure 2. Distribution of children with secondary tracheomalacia induced
different mediastinal vessel abnormalities. (A) Number of patients with
aberrant innominate artery (AIA), right aortic arch (RAA), double aortic
arch (DAA), and AIA and RAA in the whole population.

Figure 3. Bronchoalveolar lavage (BAL) cell data in children with
secondary tracheomalacia induced mediastinal vessel abnormalities (TM
children), white bars, and normal reference value (gray bars). Data are
presented as median values, interquartile range and min-max.

Figure 4. Percentage of bacteria grown in bronchoalveolar lavage sample
cultures data in children with secondary tracheomalacia induced
mediastinal vessel abnormalities: \emph{Haemophilus influenzae}
,\emph{Streptococcus pneumoniae} , Group A \selectlanguage{greek}β-\selectlanguage{english}hemolytic streptococci
(GABHS) and \emph{Moraxella catarrhalis} .

Figure 5. Neutrophilic inflammation and bacterial load in
bronchoalveolar lavage sample cultures. The percentage of BAL
neutrophils is expressed on the ordinate and the colony-forming units
(CFU)/mL on the abscissa.\selectlanguage{english}
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