PEDIATRICS Vol. 118 No. 4 October 2006, pp. e1264-e1267 (doi:10.1542/peds.2006-0135)
EXPERIENCE & REASON |
Pulmonary Function Assessment in an Infant With Barnes Syndrome: Proactive Evaluation for Surgical Intervention
a Nemours Research Lung Center
b Nemours Children's Clinic, Alfred I. duPont Hospital for Children, Wilmington, Delaware
c Christiana Care Health System, Newark, Delaware
d St Peter's University Hospital, New Brunswick, New Jersey
e Departments of Physiology and Pediatrics, Temple University School of Medicine, Philadelphia, Pennsylvania
ABSTRACT
Our aim for this study was to report pulmonary mechanics in a neonate with a severe case of Barnes syndrome, a rare form of thoracolaryngopelvic dysplasia, and to use these data to guide ventilatory support and serve as a presurgical screening tool. A comprehensive pulmonary function evaluation was performed on a 36-day-old patient with Barnes syndrome who was being mechanically ventilated because of severe pulmonary distress secondary to thoracic dystrophy. The measurements consisted of respiratory volumes including functional residual capacity, ventilatory mechanics including compliance and resistance, and thoracoabdominal synchrony. Chest wall compliance was 64% below normal, and the thoracoabdominal motion was indicative of predominantly abdominal displacement during inspiratory breaths. The lungs were functioning at a low functional residual capacity, resulting in low lung compliance and increased pulmonary resistance. As a result of the evaluation, the patient was recommended for lateral thoracic expansion surgery and the ventilatory management was adjusted to focus on end-distending pressure support.
Key Words: thoracolaryngopelvic dysplasia • chondrodystrophy • asphyxiating thoracic dystrophy • thoracic expansion • thoracoabdominal motion • functional residual capacity
Abbreviations: FRC, functional residual capacity
Barnes syndrome is a rare, autosomal dominant form of thoracolaryngopelvic dysplasia, whereby chondrodystrophy of the thoracic cage can result in death by asphyxiation. First described in case reports by Barnes et al1 in 1969, Barnes syndrome is distinct from the better-known form of asphyxiating thoracic dystrophy (Jeune syndrome) in that rib shortening is less severe and the thoracic dystrophy is complemented by laryngeal stenosis and reduced pelvic dimensions.2 Key features of the infants described with Barnes syndrome are a small, rigid, bell-shaped thorax with horizontal ribs; however, their lungs are typically not hypoplastic. In addition, these infants have abnormal laryngeal cartilage configurations and expanded costochondral junctions.3 Beyond the reduced thoracic and pelvic cavity sizes, the heads, limbs, hands, and feet of these infants were of normal proportions.1
Although Barnes syndrome can result in severe respiratory distress and death, it has been identified in a less-severe, non–life-threatening form in family members of infants who did not survive.1,4 In that lungs of infants with reduced thoracic size are not hypoplastic, surgical intervention to expand the thoracic volume has been shown to be successful.3 In this report, we present a case study of the pulmonary mechanics for a neonate with severe respiratory limitations subsequent to clinically prominent Barnes syndrome. The results of the pulmonary evaluation were used to assist in establishing acceptable ventilator settings and serve as a presurgical screening tool before consideration of lateral thoracic expansion.
MATERIALS AND METHODS
Case History
This protocol was approved by the institutional review board of Nemours Biomedical Research, and the study was performed at the Alfred I. duPont Hospital for Children. The infant was a term, 36-day-old girl weighing 3.2 kg. She was born with obvious thoracic dystrophy and, at the time of the evaluation, was breathing through a 3.5-mm internal diameter tracheostomy tube (Mallinckrodt, St Louis, MO) with mechanical ventilatory assistance (Bird VIP, Viasys, Palm Springs, CA). The ventilator was set for intermittent mechanical breaths (40 breaths per minute) with pressure-limited setting as follows: peak inspiratory pressure = 26 cmH2O, positive end-expiratory pressure = 7 cmH2O, inspiratory time = 0.4 seconds, and fraction of inspired oxygen = 0.4. There were no other reported cases of Barnes syndrome in the family history.
Measurement of Ventilatory Mechanics
Ventilatory mechanics were assessed by simultaneous measurement of transpulmonary pressure and respiratory airflow with esophageal and airway manometry and pneumotachography, as previously described.5,6 The patient was instrumented with a 6F esophageal pressure-monitoring catheter,7,8 and transpulmonary pressure was derived from proximal airway pressures and esophageal pressure by a differential pressure transducer (Validyne DP15-28; Validyne, North Ridge, CA). Optimum placement of the esophageal water-filled catheter was confirmed by real-time monitoring of pressure tracings using criteria of maximum negative deflection during inspiration with minimum cardiac artifact. Airflow was measured with a low dead-space volume pneumotachometer (No. 00, Fleish, Eplinges, Switzerland) and differential pressure transducer (Validyne MP45). Respiratory volumes were determined by integration of time and flow signals, and respiratory compliance and resistance were calculated by least-mean-square algorithms incorporated into a well-calibrated computerized pulmonary-function system (PeDs; MAS, Inc, Hatfield, PA).6 Lung compliance (CL) was differentiated from total respiratory compliance (Ctotal) by using esophageal pressures or ambient pressure, respectively, to derive transmural pressures with respect to proximal airway pressure. Compliance of the chest wall (CCW) is represented as the inverse of the difference between Ctotal–1 and CL–1. As an objective measure for pulmonary overinflation, the compliance value from the last 20% of the inspired volume relative to the Ctotal (C20/Ctotal) was calculated.9 Respiratory resistance is represented as total resistance (Rtotal) and subdivided into resistance for the inspiratory (Rinsp) and expiratory (Rexp) phases. Reported mechanics measurements were based on the average of at least 10 breaths.
Measurement of Functional Residual Capacity
Functional residual capacity (FRC) was measured using a helium dilution system (Panda; MAS, Inc) based on a previously described protocol.5,10–12 Briefly, a valve device was placed inline between the endotracheal tube and the ventilator. At end expiration, the valve device was activated to connect and ventilate the patient inline with a closed-circuit gas reservoir of known volume and helium concentration. On the basis of the new equilibrium helium concentration reached from 30 to 45 seconds and encompassing numerous breaths, FRC was calculated. Helium loss through inherent gas leaks was accounted for by distinguishing between the equilibration and leak phases of the helium concentration curve and adjusting the FRC calculation accordingly.11,12 FRC determinations were performed in triplicate and averaged.
Measurement of Thoracoabdominal Motion
The relationship between thoracic and abdominal contributions to the respiratory effort was assessed by using respiratory inductive plethysmography (Respitrace; Nims, Inc, North Bay Village, FL).13,14 Bands containing inductive coils were placed around the ribcage at the level of the axillae and around the abdomen midway between the xiphisternal junction and the umbilicus. The Respitrace device was used in the uncalibrated mode in which voltage changes in response to changes in band inductance were used to construct Lissajous loops and for calculation of phase angle between the ribcage and abdominal movement associated with respiration.5,15,16 Reported phase-angle measurements were based on the average of at least 10 breaths.
RESULTS
The infant tolerated the pulmonary function evaluation with no remarkable changes in vital signs, oxygen saturation, or blood chemistries around the time of the test procedures. Oxygen saturation remained >95%, with a fraction of inspired oxygen of 0.6. Averaged pulmonary-function measures for the patient along with predicted normal values are given in Table 1, and typical pressure-volume and flow-volume loops are presented in Fig 1. Ctotal, CL, and CCW values were notably reduced from predicted values17,18; however, the C20/Ctotal was appreciably greater than predicted. Rtotal, Rinsp, and Rexp were all >300% of the predicted values. FRC was only 37% of predicted values, and the phase angle for thoracoabdominal motion was much greater (200%) than normal values for an infant of this age.
|
|
DISCUSSION
The major aim of this report was to use pulmonary-mechanics measurements with esophageal manometry to determine the relative contribution of the chest wall and lungs to the decrease in total thoracic compliance experienced by a newborn with Barnes syndrome. All indications from this evaluation are that the patient was ventilating at the low end of the lung pressure-volume relationship curve subsequent to a noncompliant chest wall.
The prognosis of ribcage chondrodystrophy was confirmed here by a chest wall compliance value that was only 64% of the predicted norm. As a result, this infant had a thoracoabdominal phase angle much greater than the predicted normal,19 indicating that the respiratory work was being accomplished predominantly by displacement of the abdomen and not the ribcage.
Subsequent to the limitation on thoracic expansion, the lungs were functioning at a greatly reduced and inefficient FRC. The measurement of FRC as only 37% of the predicted value was confirmed in that the C20/Ctotal is relatively high and the inflation limb of the pressure volume curve (Fig 1A) demonstrates that one third of the tidal volume falls below the lower inflection point. Thus, the CL was also reduced from the expected normal level because of a low FRC and contributed to an overall low Ctotal. In addition, the high C20/Ctotal ratio can be taken to indicate that the lungs are not hypoplastic, which supports the conclusion that the reduced compliance is secondary to thoracic volume complications.
The elevation in pulmonary resistance is likely secondary to the low FRC. Collapse of the lung below the lower inflection point on the pressure-volume curve can also result in collapse of the intrapulmonary airways. This reduction in airway diameter results in a resistive load contributing to the greater-than-normal thoracoabdominal phase angle.20,21 In addition, this resistive load can contribute to complications on expiration, as indicated on the expiratory limb of the flow-volume curve (Fig 1B) by an early spike and subsequent degeneration in flow.
This case demonstrates the use of proactive pulmonary function assessment in the early stabilization and management of a patient destined to require long-term respiratory care. Whereas there is not a widespread availability of the current instruments used to perform this thorough evaluation, we are using new commercial instruments to operate an infant pulmonary diagnostics laboratory to make this clinical service more readily available. On the basis of these data, the ventilatory management plan was directed toward reducing peak inspiratory pressure support, increasing positive end-expiratory pressure for FRC management, and emphasizing chest wall stabilization to allow growth and maturation. This patient was recommended for lateral thoracic expansion surgery and serial pulmonary function studies, which are warranted after surgery.
ACKNOWLEDGMENTS
We gratefully acknowledge the support of National Institutes of Health Centers of Biomedical Research Excellence grant 1 P20 RR020173-01 (the Center for Pediatric Research).
We thank Barbara E. Gray, BA, CPM (Administrative Manager, Nemours Research Lung Center), for editing of this manuscript.
FOOTNOTES
Accepted May 23, 2006.
Address correspondence to Thomas L. Miller, PhD, Nemours Biomedical Research, AR-282, Alfred I. duPont Hospital for Children, 1600 Rockland Rd, Wilmington, DE 19803. E-mail: thmiller{at}nemours.org
The authors have indicated they have no financial relationships relevant to this article to disclose.
REFERENCES
1. Barnes ND, Hull D, Symons JS. Thoracic dystrophy.
Arch Dis Child. 1969;44
:11
–17
2. Burn J, Hall C, Marsden D, Matthew DJ. Autosomal dominant thoracolaryngopelvic dysplasia: Barnes syndrome.
J Med Genet. 1986;23
:345
–349
3. Barnes ND, Hull D, Milner AD, Waterston DJ. Chest reconstruction in thoracic dystrophy.
Arch Dis Child. 1971;46
:833
–837
4. Bankier A, Danks DM. Thoracic-pelvic dysostosis: a "new" autosomal dominant form.
J Med Genet. 1983;20
:276
–279
5. Miller TL, Palmer C, Shaffer TH, Wolfson MR. Neonatal chest wall suspension splint: a novel and noninvasive method for support of lung volume. Pediatr Pulmonol. 2005;39 :512 –520[CrossRef][Web of Science][Medline]
6. Bhutani VK, Sivieri EM, Abbasi S, Shaffer TH. Evaluation of neonatal pulmonary mechanics and energetics: a two factor least mean square analysis. Pediatr Pulmonol. 1988;4 :150 –158[Web of Science][Medline]
7. Baydur A, Behrakis PK, Zin WA, Jaeger M, Milic-Emili J. A simple method for assessing the validity of the esophageal balloon technique. Am Rev Respir Dis. 1982;126 :788 –791[Web of Science][Medline]
8. Beardsmore CS, Helms P, Stocks J, Hatch DJ, Silverman M. Improved esophageal balloon technique for use in infants.
J Appl Physiol. 1980;49
:735
–742
9. Fisher JB, Mammel MC, Coleman JM, Bing DR, Boros SJ. Identifying lung overdistention during mechanical ventilation by using volume-pressure loops. Pediatr Pulmonol. 1988;5 :10 –14[Web of Science][Medline]
10. Koen PA, Moskowitz GD, Shaffer TH. Instrumentation for measuring functional residual capacity in small animals.
J Appl Physiol. 1977;43
:755
–758
11. Schwartz JG, Fox WW, Shaffer TH. A method for measuring functional residual capacity in neonates with endotracheal tubes. IEEE Trans Biomed Eng. 1978;25 :304 –307[Web of Science][Medline]
12. Fox WW, Schwartz JG, Shaffer TH. Effects of endotracheal tube leaks on functional residual capacity determination in intubated neonates. Pediatr Res. 1979;13 :60 –64[Web of Science][Medline]
13. Duffty P, Spriet L, Bryan MH, Bryan AC. Respiratory induction plethysmography (Respitrace): an evaluation of its use in the infant. Am Rev Respir Dis. 1981;123 :542 –546[Web of Science][Medline]
14. Stick SM, Ellis E, LeSouef PN, Sly PD. Validation of respiratory inductance plethysmography ("Respitrace") for the measurement of tidal breathing parameters in newborns. Pediatr Pulmonol. 1992;14 :187 –191[Web of Science][Medline]
15. Miller TL, Blackson TJ, Shaffer TH, Touch SM. Tracheal gas insufflation-augmented continuous positive airway pressure in a spontaneously breathing model of neonatal respiratory distress. Pediatr Pulmonol. 2004;38 :386 –395[CrossRef][Web of Science][Medline]
16. Wolfson MR, Greenspan JS, Deoras KS, Allen JL, Shaffer TH. Effect of position on the mechanical interaction between the rib cage and abdomen in preterm infants.
J Appl Physiol. 1992;72
:1032
–1038
17. Bhutani VK, Sivieri EM, Abbasi S. Evaluation of pulmonary function in the neonate. In: Polin RA, Fox WW, eds. Fetal and Neonatal Physiology. WB Saunders; 1998:1143–1164
18. Gerhardt T, Hehre D, Feller R, Reifenberg L, Bancalari E. Pulmonary mechanics in normal infants and young children during first 5 years of life. Pediatr Pulmonol. 1987;3 :309 –316[Web of Science][Medline]
19. Allen JL, Greenspan JS, Deoras KS, Keklikian E, Wolfson MR, Shaffer TH. Interaction between chest wall motion and lung mechanics in normal infants and infants with bronchopulmonary dysplasia. Pediatr Pulmonol. 1991;11 :37 –43[Web of Science][Medline]
20. Deoras KS, Greenspan JS, Wolfson MR, Keklikian EN, Shaffer TH, Allen JL. Effects of inspiratory resistive loading on chest wall motion and ventilation: differences between preterm and full-term infants. Pediatr Res. 1992;32 :589 –594[Web of Science][Medline]
21. Allen JL, Wolfson MR, McDowell K, Shaffer TH. Thoracoabdominal asynchrony in infants with airflow obstruction. Am Rev Respir Dis. 1990;141 :337 –342[Web of Science][Medline]
PEDIATRICS (ISSN 1098-4275). ©2006 by the American Academy of Pediatrics
CiteULike 
Connotea 
Del.icio.us 
Digg 
Facebook 
Reddit 
Technorati 
Twitter What's this?
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
