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Management of tracheobronchomalacia with continuous positive airway pressure
Management of Tracheobronchomalacia With Continuous Positive Airway Pressure By Nathan E. Wiseman, Peter G. Duncan, and Calvin B. Cameron
Winnipeg, Manitoba, Canada 9 Three infants presenting with respiratory distress required early ventilator support. With attempts at extubation recurrent airway obstruction occurred. The clinical course was marked by recurrent episodes of hyperinflation, atelectasis, and pneumonia. Bronchoscopy, bronchography, and chest fluoroscopy revealed extensive collapse of the trachea and main stem bronchi. T w o of the infants had gastroesophageal reflux and recurrent aspiration. T r e a t m e n t of tracheobronchomalacia (TBM) was carried out with a tracheostomy tube attached to a portable C P A P apparatus. Initially CPAP was maintained at 10 cm of w a t e r and subsequently weaning was achieved by gradual decreasing of both positive pressure and hours of treatment par day. Total t r e a t m e n t time ranged from 13 to 25 months. Feedings w e r e carried out via gastrostomy. T w o infants with severe gastroesophageal reflux u n d e r w e n t fundoplication. Each infant was successfully w e a n e d from distending pressure and decanulatad. The t r e a t m e n t of sever T B M with long-term CPAP appears to be a reasonable alternative or adjunct to surgical procedures such as tracheopexy, resection, external splinting and tracheobronchoplasty. 9 1985 by Grune & Stratton, Inc. INDEX W O R D : Tracheobronchomalacia.
R A C H E O B R O N C H O M A L A C I A (TBM) is a rare disease of infancy and childhood characterized by abnormal compliance of the tracheobronchial tree. ~ The disease may occur as a primary 2 entity or secondary to congenital lesions causing tracheobronchial compression as seen with esophageal atresia? and vascular rings. 4 The diagnosis is established at bronchoscopy 5 and fluoroscopy, ~ which reveal tracheobronchial collapse. Although mild forms of the disease may be diagnosed beyond infancy, 6 severe T B M presents as neonatal respiratory distress with evidence of airway obstruction. 7 In some patients pathologic examination may reveal tracheobronchial cartilaginous abnormalities. 8 In the past, medical management of patients with T B M has met with variable success. In an effort to improve survival, C P A P has been advocated as a mode of therapy. 9 Three patients with severe T B M were treated successfully with the long-term use of CPAP.
T
CPAP at 7 cm of water. Initial efforts to decrease the CPAP resulted in recurrent airway obstruction. At age 9 months, bronchoscopy revealed severe TBM with aposition of the distal trachea in the AP diameter, flattening of the carina, and collapse of the left lower lobe bronchus. Gradual weaning from CPAP was achieved between 12 and 18 months by removing the distending pressure during progressively increasing periods of time each day. Recurrent pneumonias complicated the weaning. At age 21 months the tracheostomy tube was removed. Additional problems in this child included: Pierre Robin syndrome, spondyloepiphyseal dysplasia, short limb dwarfism, seisure disorder, developmental delay, and pectus carinatum. The child's pulmonary status remains stable at age 5 years.
Case 2 A female infant weighing 4640 g was born following an uncomplicated pregnancy with Apgars of 4 at 1 minute and 5 at 5 minutes. Acute respiratory distress at birth required immediate intubation and ventilator support. At 1 day of age chest x-ray showed bilaterial pulmonary hyperlucency and bronchoscopy was considered normal. Attempts at extubation resulted in airway obstruction and worsening cyanosis. Chest fluoroscopy showed marked anteroposterior collapse of the lower trachea and main bronchi (Fig 1). TBM was diagnosed and tracheostomy performed. By age two months the infant was weaned from the ventilator to CPAP (10 cm of water) breathing spontaneously. At age 4 months aspiration pneumonia secondary to severe gastroesophageal reflux necessitated fundoplication and gastrostomy. During the first year of life CPAP was maintained at 10 cm of water and the course was complicated by recurrent pneumonia and persistent hyperlucency of the left lung. Gradual weaning from CPAP was accomplished at age 27 months. Inability to take oral feeding was the major late complication persisting until age 4 years. At age 7 years the child is developmentally normal and remains free from respiratory symptoms.
Case 3 This 3500 g infant had Apgars of 3 at 1 minute and 4 at 5 minutes. Cyanosis and respiratory distress were evident on day 1 of life and by day 3 the infant required ventilator support. Aspiration pneumonia led to the diagnosis of hiatus hernia with severe gastroesophageal reflux. Early attempts at weaning from the ventilator resulted in cyanosis and respiratory arrest. Bronchoscopy at age 3 weeks was considered to be normal. Fundoplication at age 6 weeks was followed by successful weaning from the ventilator, however, progressive respiratory distress, upper lobe collapse, and hypercapnia necessitated reinstitution of ventilator support (Fig 2). At age 4 months, repeat bronchoscopy revealed severe TBM with complete collapse of
A 3060 g Inuit female was born following a full-term pregnancy complicated by polyhydramnios. At birth the infant was grunting, indrawing, and cyanotic. On day 4 of life, she was intubated and placed on ventilator support. Tracheostomy was performed at 31/2 months of age and was followed by weaning from the ventilator to
From the Sections o f Pediatric Surgery and Pediatric Anesthesiology, Children's Hospital o f Winnipeg, Manitoba, Canada. Presented at the Annual Meeting o f the Canadian Association o f Paediatric Surgeons, September 10-11, 1984, Montreal, Quebec, Canada. Address reprint requests to Nathan E. Wiseman, MD, Children's Hospital o f Winnipeg, Winnipeg, Manitoba, R3E OWl, Canada. 9 1985 by Grune & Stratton, Inc. 0022-3468/85/2005~0004503.00/0
Journal of Pediatric Surgery, Vol 20, No 5 (October), 1985: pp 489-493
489
CASE REPORTS Case 1
490
WISEMAN ET AL
Fig 1. Case 2: Fluoroscopy of trachea and bronchus (top) during spontaneous breathing with (A) and without (B) CPAP. An increase in airway caliber is seen with CPAP. Fluoroscopy of trachea and bronchus breathing spontaneously showing increase in caliber during inspiration (C) and decrease in airway caliber during expiration (D).
the lower trachea and left main bronchus. At bronchoscopyapplication of positive pressure was noted to reduce airway collapse. By 5 months, the infant was weaned from the ventilator to CPAP (10 cm water). Between ages 6 and 18 months the infant was weaned by a step-wise reduction of CPAP and a progressive increase in time periods with distending pressure off. At age 18 months the tracheostomy was decannulated. Recurrent pneumonia and respiratory failure at ages 24 and 28 months resulted in reinstitution of ventilator support for two two-week periods. The child is now home under close surveillance and has the additional problem of developmentaldelay and a significantpectus carinatum deformity. MATERIALS AND
METHODS
Continuous positive airway pressure was administered to patients using a modified East-Radcliffe ventilatory circuit (Fig 3). Heated and humidified blended fresh gases pass constantly in front of the patient's tracheostomy to which the circuit is attached via a standard T connecter. Continuous airway pressure is applied during exhalation by passage through a commercial PEEP valve (Bird). Inspiratory positive pressure is maintained by a 2 litre anesthetic reservoir bag located on the inspiratory limb of the circuit. When distended, the bag compliancemaintains a constant positivityover the range of the patient's tidal volume.Pressure monitoringwith highqow alarms and a pressure relief valve are located on the expiratory limb of the circuit. The CPAP apparatus is compact and portable such that with
the apparatus attached infants are able to move about easily and may even ambulate. DISCUSSION
I n T B M a b n o r m a l l y compliant airways exhibit a tendency to collapse. Collapse occurs when the transm u r a l force exceeds the intrinsic rigidity (compliance) of the airway I (Fig 4). D u r i n g forced expiration, cough, or Valsalva maneuver, i n t r a p l e u r a l pressure m a y become positive, resulting in a collapsing force upon the trachea. T r a c h e a l a n d bronchial narrowing during expiration is a normal observation however in patients with a b n o r m a l compliance complete collapse m a y o c c u r ) A t bronchoscopy patients with T B M demonstate aposition of the anterior and posterior wall of the trachea a n d proximal b r o n c h i ) '5 In the n e o n a t e this diagnostic finding m a y be overlooked when positive pressure ventilation L~ (Case 2) is used and thus airway collapse is best observed with patients breathing s p o n t a n e o u s l y : A t fluoroscopy the intrathoracic portion of the trachea and proximal bronchi are seen to collapse d u r i n g the expiratory phase of respiration in
TRACHEOBRONCHOMALACIA
491
Fig 2. Case 3: Chest x-rays during first 6 months of life: 13 w e e k s (A) bilateral basal consolidation; 17 weeks--(B) complete collapse of right upper lobe; 20 w e e k s - - ( C ) hyperinflation of left and right lower lobe; 23 w e e k s - - ( D ) hyperinfiation of left lower lobe with partial collapse of left upper lobe.
patients with TBM 1 (Case 2). The application of CPAP to infants with TBM produces a positive intratracheal pressure throughout the respiratory cycle with a resultant transtracheal force which tends to prevent collapse; an observation made both at bronchoscopy and fluoroscopy.9 In patients with less severe tracheomalacia H and bronchomalacia 2 survival with medical treatment has been possible. In severe TBM as reported by McMahon ~ and Gupta lz medical and surgical management proved unsuccessful. Five patients have been previously reported in whom CPAP was used in the management of TBM diagnosed in early infancy. Neijens 9 applied 5 cm of CPAP over 14-week periods to 2 patients with severe bronchomalacia. Symptomatic and bronchoscopic improvement was noted at the time of CPAP weaning with both patients surviving. Campbell ~3 applied 5 cm of CPAP for a period of 23 weeks to an infant with bronchomalacia who subsequently came to bilobectomy with survival. In 2 separate reports of severe tracheomalacia diagnosed in infants with Larsen's syndrome, Gundfast ~4and Kanter ~~used high levels of CPAP (15 to 30 cm of water) for periods in excess of 14 and 22 months respectively
with surviving infants. Kanter demonstrated that the application of CPAP was associated with a decrease in transpulmonary pressure change throughout the respiratory cycle and an increase in peak flow, tidal volume, and minute ventilation. The efficacy of the technique appears to be well established with eight reported surviving patients. Disadvantages to this mode of therapy have also been noted: prolonged intubation and attachment to the CPAP apparatus poses restrictions upon infants and developmental delay results. Also observed is a delay in the onset of normal oral feedings, a problem compounded by the presence of gastroesophageal reflux. Long-term separation from family in early infancy resulted in failure of normal bonding and parental rejection in two of the patients reported. It has however been possible to maintain CPAP therapy in the home l0 (Case 2) during the late weaning stage of therapy. Surgical management of severe TBM has met with some success. Secondary tracheomalacia in infants with esophageal atresia has been treated successfully by anterior tracheopexy. 15 Nakayama 16 has demonstrated the feasibility of tracheal resection in early infancy and both Saad ~7 and Kimura ~8 have success-
492
WISEMAN ET AL
,,.
f'
o2
Fig 3. Ventilatory circuit for administration of CPAP. Inspiratory limb of circuit (arrows directed to patient) contains anesthetic reservoir bag for maintenance of positive pressure during inspiration. Expiratory limb of circuit (arrows away from patient) contains PEEP valve for maintenance of positive pressure during expiration.
fully treated infants with long segment tracheal stenosis using the technique of cartilage graft tracheoplasty. Recently, Filler ~9reported the successful treatment of four patients with tracheomalacia using a prosthetic external tracheal splint. All of these surgical techniques appropriately applied appear to have a roll to play in the management of TBM. Pathologic examination of the airways in patients with TBM have demonstrated abnormalities in cartilage development. 6'8 These include: a reduction in
Pc
=
AIRWAY
COMPLIANCE
=
number, size, and thickness, of cartilage plates and a reduced peripheral distribution of cartilage in the bronchial tree. Absence of the longitudinal muscle in the membranous portion of the trachea has been shown in some patients. 2~These findings may each contribute to abnormal airway compliance. Sinclair-Smith 21demonstrated that an increase in the number of cartilage bearing bronchi and an increase in the number of cartilage fragments occurs during early infancy. Also noted was an increase in the total area of cartilage in 1 Pr
=
AIRWAY
RESISTANCE
i tm - T R A N S M U R A L
Ptm = Pit - Pet
it
-
INTRATRACHEAL
et - E X T R A T R A C H E A L NORMAL
TBM
P ~ > Pc
TBM + CPAP
Pc' >
Pc
Pit' = Pit + Pcpap
Pc' >
Ptm
Ptm' = Pit'- Pet Ptm' •
t
Pc'
9
/
Fig 4. Physiologic rationale for CPAP: Normal patient (left) maintains airway patency with transmural pressure (Pt,) greater than airway compliance (Pc). With tracheobronchomalacia (middle) abnormally high compliance (P'c) becomes greater than transmural pressure (Ptm) resulting in airway collapse. Application of CPAP (right) results in an increase in intratracheal pressure (P~ = Pk + P===p) and an increase in transmural pressure (Pt~,). The normal relationship between transmural pressure and airway compliance (Pt~, > P') is restored and airway patency is maintained.
TRACHEOBRONCHOMALACIA
493
the child's lungs during infancy and childhood. Early growth of the cartilaginous structure and bronchi may account for the improvement of airway compliance which has been observed in patients with TBM. This, together with the increase in airway size which occurs
with normal growth results in an ability to maintain airway patency after treatment with CPAP and facilitates successful weaning. It remains to be determined whether the application of CPAP has any direct effect upon the growth of airways or their cartilage.
REFERENCES 1. Wittenberg MH, Gyepes MT, Crocker D: Tracheal dynamics in infants with respiratory distress, stridor, and collapsing trachea. Radiology 88:653-662, 1967 2. Lynch JI: Bronchomalacia in children--Considerations governing medical vs surgical treatment. Clin Pediatr 9:279-282, 1970 3. Davies MRQ, Cywes S: The flaccid trachea and tracheoesophageal congenital anomalies. J Pediatr Surg 13:363-367, 1978 4. Harrison MR, Hendren H: Agenesis of the lung complicated by vascular compression and bronchomalacia. J Pediatr Surg 10:813-816, 1975 5. Benjamin B: Endoscopy in congenital tracheal anomalies. J Pediatr Surg 15:164-171, 1980 6. Williams HE, Landau LI, Phelan PD: Generalized bronchiectasis due to extensive deficiency of bronchial cartilage. Arch Dis Child 47:423-428, 1972 7. Agosti E, DeFilippi G, Fior R, et al: Generalized familial bronchomalacia. Acta Paediatr Scand 63:616-618, 1974 8. McMahon HE, Ruggiere J: Congenital segmental bronchomalacia. Am J Dis Child 118:923-926, 1969 9. Neijens H J, Kerrebijn KF, Smalhout B: Successful treatment with CPAP of two infants with bronchomalacia. Acta Paediatr Scand 67:293-296, 1978 10. Kanter RK, Pollack MM, Wright WW, et al: Treatment of severe tracheobronchomalacia with continuous positive airway pressure (CPAP). Anesthesiology 57:54-56, 1982 11. Cox WL, Shaw RR: Congenital chondromalacia of the trachea. J Thor Cardiovasc Surg 49:1033-1039, 1965
12. Gupta TGCM, Goldberg S J, Lewis E, et al: Congenital bronchomalacia. Am J Dis Child 115:88-90, 1968 13. Campbell PE: Congenital lobar emphysema. Aust Paediat J 5:226-233, 1969 14. Grundfast KM, Kanter R, Mumtaz A, et al: Tracheomalacia dynamics in infants with multiplex congenita (Larsen's) syndrome. Ann Otol 90:303-306, 1981 15. Cohen D: Tracheopexy-aorto-tracheal suspension for severe tracheomalacia. Aust Paediatr J 17:117-121, 1981 16. Nakayama DK, Harrison MR, Delorimier AA, et al: Reconstructive surgery for obstructing lesions of the intrathoracic trachea in infants and small children. J Pediatr Surg 17:854-868, 1982 17. Saad AS, Falla A: Management of intractable and extensive tracheal stenosis by implantation of cartilage graft. J Pediatr Surg 18:472-474, 1983 18. Kimura K, Mukohara N, Tsugawa C, et al: Tracheoplasty for congenital stenosis of the entire trachea. J Pediatr Surg 17:869-871, 1982 19. Filler RM, Buck JR, Bahoric A, et al: Treatment of segmental tracheomalacia and bronchomalacia by implantation of an airway splint. J Pediatr Surg 17:597-603, 1982 20. Wailoo M, Emery JL: Structure of the membranous trachea in children. Acta Anat 106:254-261, 1980 21. Sinclair-Smith CC, Emery 3L, Gadson D, et al: Cartilage in children's lungs: A quantitative assessment using the right middle lobe. Thorax 31:40-43, 1976
Winnipeg, Manitoba, Canada 9 Three infants presenting with respiratory distress required early ventilator support. With attempts at extubation recurrent airway obstruction occurred. The clinical course was marked by recurrent episodes of hyperinflation, atelectasis, and pneumonia. Bronchoscopy, bronchography, and chest fluoroscopy revealed extensive collapse of the trachea and main stem bronchi. T w o of the infants had gastroesophageal reflux and recurrent aspiration. T r e a t m e n t of tracheobronchomalacia (TBM) was carried out with a tracheostomy tube attached to a portable C P A P apparatus. Initially CPAP was maintained at 10 cm of w a t e r and subsequently weaning was achieved by gradual decreasing of both positive pressure and hours of treatment par day. Total t r e a t m e n t time ranged from 13 to 25 months. Feedings w e r e carried out via gastrostomy. T w o infants with severe gastroesophageal reflux u n d e r w e n t fundoplication. Each infant was successfully w e a n e d from distending pressure and decanulatad. The t r e a t m e n t of sever T B M with long-term CPAP appears to be a reasonable alternative or adjunct to surgical procedures such as tracheopexy, resection, external splinting and tracheobronchoplasty. 9 1985 by Grune & Stratton, Inc. INDEX W O R D : Tracheobronchomalacia.
R A C H E O B R O N C H O M A L A C I A (TBM) is a rare disease of infancy and childhood characterized by abnormal compliance of the tracheobronchial tree. ~ The disease may occur as a primary 2 entity or secondary to congenital lesions causing tracheobronchial compression as seen with esophageal atresia? and vascular rings. 4 The diagnosis is established at bronchoscopy 5 and fluoroscopy, ~ which reveal tracheobronchial collapse. Although mild forms of the disease may be diagnosed beyond infancy, 6 severe T B M presents as neonatal respiratory distress with evidence of airway obstruction. 7 In some patients pathologic examination may reveal tracheobronchial cartilaginous abnormalities. 8 In the past, medical management of patients with T B M has met with variable success. In an effort to improve survival, C P A P has been advocated as a mode of therapy. 9 Three patients with severe T B M were treated successfully with the long-term use of CPAP.
T
CPAP at 7 cm of water. Initial efforts to decrease the CPAP resulted in recurrent airway obstruction. At age 9 months, bronchoscopy revealed severe TBM with aposition of the distal trachea in the AP diameter, flattening of the carina, and collapse of the left lower lobe bronchus. Gradual weaning from CPAP was achieved between 12 and 18 months by removing the distending pressure during progressively increasing periods of time each day. Recurrent pneumonias complicated the weaning. At age 21 months the tracheostomy tube was removed. Additional problems in this child included: Pierre Robin syndrome, spondyloepiphyseal dysplasia, short limb dwarfism, seisure disorder, developmental delay, and pectus carinatum. The child's pulmonary status remains stable at age 5 years.
Case 2 A female infant weighing 4640 g was born following an uncomplicated pregnancy with Apgars of 4 at 1 minute and 5 at 5 minutes. Acute respiratory distress at birth required immediate intubation and ventilator support. At 1 day of age chest x-ray showed bilaterial pulmonary hyperlucency and bronchoscopy was considered normal. Attempts at extubation resulted in airway obstruction and worsening cyanosis. Chest fluoroscopy showed marked anteroposterior collapse of the lower trachea and main bronchi (Fig 1). TBM was diagnosed and tracheostomy performed. By age two months the infant was weaned from the ventilator to CPAP (10 cm of water) breathing spontaneously. At age 4 months aspiration pneumonia secondary to severe gastroesophageal reflux necessitated fundoplication and gastrostomy. During the first year of life CPAP was maintained at 10 cm of water and the course was complicated by recurrent pneumonia and persistent hyperlucency of the left lung. Gradual weaning from CPAP was accomplished at age 27 months. Inability to take oral feeding was the major late complication persisting until age 4 years. At age 7 years the child is developmentally normal and remains free from respiratory symptoms.
Case 3 This 3500 g infant had Apgars of 3 at 1 minute and 4 at 5 minutes. Cyanosis and respiratory distress were evident on day 1 of life and by day 3 the infant required ventilator support. Aspiration pneumonia led to the diagnosis of hiatus hernia with severe gastroesophageal reflux. Early attempts at weaning from the ventilator resulted in cyanosis and respiratory arrest. Bronchoscopy at age 3 weeks was considered to be normal. Fundoplication at age 6 weeks was followed by successful weaning from the ventilator, however, progressive respiratory distress, upper lobe collapse, and hypercapnia necessitated reinstitution of ventilator support (Fig 2). At age 4 months, repeat bronchoscopy revealed severe TBM with complete collapse of
A 3060 g Inuit female was born following a full-term pregnancy complicated by polyhydramnios. At birth the infant was grunting, indrawing, and cyanotic. On day 4 of life, she was intubated and placed on ventilator support. Tracheostomy was performed at 31/2 months of age and was followed by weaning from the ventilator to
From the Sections o f Pediatric Surgery and Pediatric Anesthesiology, Children's Hospital o f Winnipeg, Manitoba, Canada. Presented at the Annual Meeting o f the Canadian Association o f Paediatric Surgeons, September 10-11, 1984, Montreal, Quebec, Canada. Address reprint requests to Nathan E. Wiseman, MD, Children's Hospital o f Winnipeg, Winnipeg, Manitoba, R3E OWl, Canada. 9 1985 by Grune & Stratton, Inc. 0022-3468/85/2005~0004503.00/0
Journal of Pediatric Surgery, Vol 20, No 5 (October), 1985: pp 489-493
489
CASE REPORTS Case 1
490
WISEMAN ET AL
Fig 1. Case 2: Fluoroscopy of trachea and bronchus (top) during spontaneous breathing with (A) and without (B) CPAP. An increase in airway caliber is seen with CPAP. Fluoroscopy of trachea and bronchus breathing spontaneously showing increase in caliber during inspiration (C) and decrease in airway caliber during expiration (D).
the lower trachea and left main bronchus. At bronchoscopyapplication of positive pressure was noted to reduce airway collapse. By 5 months, the infant was weaned from the ventilator to CPAP (10 cm water). Between ages 6 and 18 months the infant was weaned by a step-wise reduction of CPAP and a progressive increase in time periods with distending pressure off. At age 18 months the tracheostomy was decannulated. Recurrent pneumonia and respiratory failure at ages 24 and 28 months resulted in reinstitution of ventilator support for two two-week periods. The child is now home under close surveillance and has the additional problem of developmentaldelay and a significantpectus carinatum deformity. MATERIALS AND
METHODS
Continuous positive airway pressure was administered to patients using a modified East-Radcliffe ventilatory circuit (Fig 3). Heated and humidified blended fresh gases pass constantly in front of the patient's tracheostomy to which the circuit is attached via a standard T connecter. Continuous airway pressure is applied during exhalation by passage through a commercial PEEP valve (Bird). Inspiratory positive pressure is maintained by a 2 litre anesthetic reservoir bag located on the inspiratory limb of the circuit. When distended, the bag compliancemaintains a constant positivityover the range of the patient's tidal volume.Pressure monitoringwith highqow alarms and a pressure relief valve are located on the expiratory limb of the circuit. The CPAP apparatus is compact and portable such that with
the apparatus attached infants are able to move about easily and may even ambulate. DISCUSSION
I n T B M a b n o r m a l l y compliant airways exhibit a tendency to collapse. Collapse occurs when the transm u r a l force exceeds the intrinsic rigidity (compliance) of the airway I (Fig 4). D u r i n g forced expiration, cough, or Valsalva maneuver, i n t r a p l e u r a l pressure m a y become positive, resulting in a collapsing force upon the trachea. T r a c h e a l a n d bronchial narrowing during expiration is a normal observation however in patients with a b n o r m a l compliance complete collapse m a y o c c u r ) A t bronchoscopy patients with T B M demonstate aposition of the anterior and posterior wall of the trachea a n d proximal b r o n c h i ) '5 In the n e o n a t e this diagnostic finding m a y be overlooked when positive pressure ventilation L~ (Case 2) is used and thus airway collapse is best observed with patients breathing s p o n t a n e o u s l y : A t fluoroscopy the intrathoracic portion of the trachea and proximal bronchi are seen to collapse d u r i n g the expiratory phase of respiration in
TRACHEOBRONCHOMALACIA
491
Fig 2. Case 3: Chest x-rays during first 6 months of life: 13 w e e k s (A) bilateral basal consolidation; 17 weeks--(B) complete collapse of right upper lobe; 20 w e e k s - - ( C ) hyperinflation of left and right lower lobe; 23 w e e k s - - ( D ) hyperinfiation of left lower lobe with partial collapse of left upper lobe.
patients with TBM 1 (Case 2). The application of CPAP to infants with TBM produces a positive intratracheal pressure throughout the respiratory cycle with a resultant transtracheal force which tends to prevent collapse; an observation made both at bronchoscopy and fluoroscopy.9 In patients with less severe tracheomalacia H and bronchomalacia 2 survival with medical treatment has been possible. In severe TBM as reported by McMahon ~ and Gupta lz medical and surgical management proved unsuccessful. Five patients have been previously reported in whom CPAP was used in the management of TBM diagnosed in early infancy. Neijens 9 applied 5 cm of CPAP over 14-week periods to 2 patients with severe bronchomalacia. Symptomatic and bronchoscopic improvement was noted at the time of CPAP weaning with both patients surviving. Campbell ~3 applied 5 cm of CPAP for a period of 23 weeks to an infant with bronchomalacia who subsequently came to bilobectomy with survival. In 2 separate reports of severe tracheomalacia diagnosed in infants with Larsen's syndrome, Gundfast ~4and Kanter ~~used high levels of CPAP (15 to 30 cm of water) for periods in excess of 14 and 22 months respectively
with surviving infants. Kanter demonstrated that the application of CPAP was associated with a decrease in transpulmonary pressure change throughout the respiratory cycle and an increase in peak flow, tidal volume, and minute ventilation. The efficacy of the technique appears to be well established with eight reported surviving patients. Disadvantages to this mode of therapy have also been noted: prolonged intubation and attachment to the CPAP apparatus poses restrictions upon infants and developmental delay results. Also observed is a delay in the onset of normal oral feedings, a problem compounded by the presence of gastroesophageal reflux. Long-term separation from family in early infancy resulted in failure of normal bonding and parental rejection in two of the patients reported. It has however been possible to maintain CPAP therapy in the home l0 (Case 2) during the late weaning stage of therapy. Surgical management of severe TBM has met with some success. Secondary tracheomalacia in infants with esophageal atresia has been treated successfully by anterior tracheopexy. 15 Nakayama 16 has demonstrated the feasibility of tracheal resection in early infancy and both Saad ~7 and Kimura ~8 have success-
492
WISEMAN ET AL
,,.
f'
o2
Fig 3. Ventilatory circuit for administration of CPAP. Inspiratory limb of circuit (arrows directed to patient) contains anesthetic reservoir bag for maintenance of positive pressure during inspiration. Expiratory limb of circuit (arrows away from patient) contains PEEP valve for maintenance of positive pressure during expiration.
fully treated infants with long segment tracheal stenosis using the technique of cartilage graft tracheoplasty. Recently, Filler ~9reported the successful treatment of four patients with tracheomalacia using a prosthetic external tracheal splint. All of these surgical techniques appropriately applied appear to have a roll to play in the management of TBM. Pathologic examination of the airways in patients with TBM have demonstrated abnormalities in cartilage development. 6'8 These include: a reduction in
Pc
=
AIRWAY
COMPLIANCE
=
number, size, and thickness, of cartilage plates and a reduced peripheral distribution of cartilage in the bronchial tree. Absence of the longitudinal muscle in the membranous portion of the trachea has been shown in some patients. 2~These findings may each contribute to abnormal airway compliance. Sinclair-Smith 21demonstrated that an increase in the number of cartilage bearing bronchi and an increase in the number of cartilage fragments occurs during early infancy. Also noted was an increase in the total area of cartilage in 1 Pr
=
AIRWAY
RESISTANCE
i tm - T R A N S M U R A L
Ptm = Pit - Pet
it
-
INTRATRACHEAL
et - E X T R A T R A C H E A L NORMAL
TBM
P ~ > Pc
TBM + CPAP
Pc' >
Pc
Pit' = Pit + Pcpap
Pc' >
Ptm
Ptm' = Pit'- Pet Ptm' •
t
Pc'
9
/
Fig 4. Physiologic rationale for CPAP: Normal patient (left) maintains airway patency with transmural pressure (Pt,) greater than airway compliance (Pc). With tracheobronchomalacia (middle) abnormally high compliance (P'c) becomes greater than transmural pressure (Ptm) resulting in airway collapse. Application of CPAP (right) results in an increase in intratracheal pressure (P~ = Pk + P===p) and an increase in transmural pressure (Pt~,). The normal relationship between transmural pressure and airway compliance (Pt~, > P') is restored and airway patency is maintained.
TRACHEOBRONCHOMALACIA
493
the child's lungs during infancy and childhood. Early growth of the cartilaginous structure and bronchi may account for the improvement of airway compliance which has been observed in patients with TBM. This, together with the increase in airway size which occurs
with normal growth results in an ability to maintain airway patency after treatment with CPAP and facilitates successful weaning. It remains to be determined whether the application of CPAP has any direct effect upon the growth of airways or their cartilage.
REFERENCES 1. Wittenberg MH, Gyepes MT, Crocker D: Tracheal dynamics in infants with respiratory distress, stridor, and collapsing trachea. Radiology 88:653-662, 1967 2. Lynch JI: Bronchomalacia in children--Considerations governing medical vs surgical treatment. Clin Pediatr 9:279-282, 1970 3. Davies MRQ, Cywes S: The flaccid trachea and tracheoesophageal congenital anomalies. J Pediatr Surg 13:363-367, 1978 4. Harrison MR, Hendren H: Agenesis of the lung complicated by vascular compression and bronchomalacia. J Pediatr Surg 10:813-816, 1975 5. Benjamin B: Endoscopy in congenital tracheal anomalies. J Pediatr Surg 15:164-171, 1980 6. Williams HE, Landau LI, Phelan PD: Generalized bronchiectasis due to extensive deficiency of bronchial cartilage. Arch Dis Child 47:423-428, 1972 7. Agosti E, DeFilippi G, Fior R, et al: Generalized familial bronchomalacia. Acta Paediatr Scand 63:616-618, 1974 8. McMahon HE, Ruggiere J: Congenital segmental bronchomalacia. Am J Dis Child 118:923-926, 1969 9. Neijens H J, Kerrebijn KF, Smalhout B: Successful treatment with CPAP of two infants with bronchomalacia. Acta Paediatr Scand 67:293-296, 1978 10. Kanter RK, Pollack MM, Wright WW, et al: Treatment of severe tracheobronchomalacia with continuous positive airway pressure (CPAP). Anesthesiology 57:54-56, 1982 11. Cox WL, Shaw RR: Congenital chondromalacia of the trachea. J Thor Cardiovasc Surg 49:1033-1039, 1965
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