PEDIATRICS Vol. 108 No. 3 September 2001, pp. 759-761

COMMENTARY:
Nasal Prongs Continuous Positive Airway Pressure: A Simple Yet Powerful Tool

The recent article by Van Marter et al,¹ discussing the association between barotrauma, oxygen toxicity, and chronic lung disease (CLD) in the very low birth weight infant (VLBWI) weighing <1500 g was of great interest. They observed a significantly lower incidence of CLD in the VLBWI at Children's Hospital of New York-Columbia University compared with 2 other centers affiliated with Harvard University in Boston. The difference in incidence of CLD was wide, 4% versus 22%. The lower incidence of CLD was true for all gestational age and birth weight subcategories. Columbia University is recognized for its strategy of early use of nasal prongs continuous positive airway pressure (NP-CPAP).² The association of low incidence of CLD and the use of NP-CPAP was reported earlier in 1987 by Avery et al.² This association was confirmed in a survey of other 11 American neonatal centers.³ In Sweden, a citywide survey in neonatal units in Stockholm confirmed the feasibility of the early use of NP-CPAP.⁴

The early use of NP-CPAP is not only successful in the VLBWI, but also in the extremely low birth weight infant (ELBWI) weighing <1000 g. In September 1997, at the George Washington University Department of Newborn Service we emphasized the use of NP-CPAP as the primary mode of respiratory support in all premature infants. In our practice, infants are supported by NP-CPAP from the very first minutes of life. Only 7 out of 48 (14.6%) surviving ELBWIs required early intubation and surfactant application with mechanical ventilation. The mean duration of mechanical ventilation in the ELBWI deceased significantly from 12.7 to 7.4 days (P < .05).⁵ As our staff became more familiar with the NP-CPAP system, current mechanical ventilation days further decreased to 4.0 days. A recent experience in Germany with the early use of NP-CPAP reported a significant decrease in mechanical ventilation (40% vs 84%), lower incidence of CLD (12% vs 32%), lower incidence of grades III and IV intraventricular hemorrhage (16% vs 38%), and shorter hospitalization (91 vs 102 days).⁶

Continuous positive airway pressure (CPAP) splints the airway and diaphragm of the premature infant. It also improves functional residual capacity, ventilation/perfusion matching, and prevents collapse of the surfactant-deficient alveoli.⁷ Moreover, inflation through CPAP appears to stimulate the growth of the immature lung.⁸ NP-CPAP reduces lung volutruma and CLD, and is associated with a lower incidence of acute airleak syndrome.^6,9 Whether the intact vocal cords in the spontaneously breathing infant play a role in preventing overdistension of the lungs needs to be explored. If proven true, bypassing this mechanism could be the major triggering factor in the pathogenesis of both acute airleaks and CLD in the mechanically ventilated infant. CPAP nasal prongs have a significantly larger internal diameter compared with a standard endotracheal tube. The increase in diameter of nasal prongs reduces the flow resistance and work of breathing in the NP-CPAP supported infants by more than fourfold.¹⁰ Finally, during endotracheal intubation the cilliary movements are decreased. This impairs the clearance of secretions and bacteria, thus triggering an inflammatory response. This could, in part, explain the inflammatory mediators found in bronchial aspirate in the early stage of CLD.¹¹

Hyaline membrane disease (HMD) is not necessarily the primary factor responsible for the development of CLD. Analysis of available literature implicates ventilation strategy more than HMD. Because CLD develops mainly in premature infants, either the change of the environment of the lungs or the iatrogenic ventilatory management are the 2 likely possibilities for the development of CLD. In animal studies, fetal lambs did not develop lung diseases when placed on apneic oxygenation (flowing oxygen into the trachea while keeping the animal apneic) and extracorporeal carbon dioxide removal.¹² On the other hand, mature healthy sheep developed acute lung injury and respiratory failure after pharmacologically-induced hyperventilation (infusing sodium salicylate into cisterna magna).¹³ Lung injury was documented in premature lambs after brief resuscitation with large tidal volumes.¹⁴ One may question why infants of the same degree of prematurity have a widely variable incidence of CLD with a range of 4% to 42%. This variability is true even when the same criteria are used to define CLD in infants with similar birth weight and/or gestational age in the same time frame.^1,2,3 The variability in pulmonary outcomes could be explained by differences in management between neonatal centers, even among neonatologists in the same center. Despite the advent of new strategies targeting HMD such as prenatal steroids, surfactant therapy, high-frequency oscillation, and postnatal steroids, CLD remains a major complication in neonatal units. In fact, some recent data reveal an increasing incidence of CLD.¹⁵ On the other hand, strategies that avoid the iatrogenic trauma of mechanical ventilation, such as NP-CPAP, could dramatically lower the incidence of CLD. These issues, when considered together, support the association of CLD and mechanical ventilation.

The water-seal CPAP system is currently used at the George Washington University, Columbia University, and many other centers. In this simple system, a gas mixture flows to the infant from the wall source after it is warmed and humidified. The free expiratory limb of the tube is immersed under the surface of sterile water (or 0.25% acetic acid) to produce the required CPAP (usually 5 cm H₂O; Fig 1).

View larger version (49K): [in this window] [in a new window]   Fig. 1.   Water-seal CPAP.

The time has come to conduct a randomized, controlled trial to evaluate the efficacy of NP-CPAP over conventional mechanical ventilation. Mechanical ventilation, with its known complications, should not be considered the default strategy. This can be likened to the use of 100% oxygen therapy for the treatment of apnea in premature infants in the 1940s. That approach cost the nation an epidemic of blindness, until William Silverman conducted a randomized trial and implicated 100% oxygen as the offending agent. The use of NP-CPAP requires meticulous attention to the airway. To succeed with NP-CPAP, it is important to use the correct size prongs, to properly position the neck, to provide frequent suction of the airway secretions, and observe for the patterns of breathing. NP-CPAP will fail without attention to these issues. A more standardized and rigorous training of physicians and nurses in the use of this technique is needed as a first step before such randomized trials are started. This would ensure uniform application of this simple, yet most powerful tool.

ACKNOWLEDGMENT

I thank Dr Theodor Kolobow at the National Institutes of Health for the critical review of this commentary.

Hany Z. Aly, MD, FAAP
Departments of Pediatrics, Obstetrics and Gynecology
Division of Newborn Service
George Washington University Medical Center
Children's National Medical Center
Washington, DC 20037

FOOTNOTES

Received for publication Jan 3, 2001; accepted Mar 29, 2001.

Reprint requests to (H.Z.A.) George Washington University Medical Center, 901 23rd St, NW, Rm 3-246 S, Washington, DC 20037. E-mail: haly{at}cnmc.org

ABBREVIATIONS

CLD, chronic lung disease; VLBWI, very low birth weight infant; NP-CPAP, nasal prongs continuous positive airway pressure; ELBWI, extremely low birth weight infant; CPAP, continuous positive airway pressure; HMD, hyaline membrane disease.

REFERENCES

1. Van Marter LJ, Allerd EN, Pagano M, Do clinical markers of barotrauma and oxygen toxicity explain interhospital variation in rates of chronic lung disease? Pediatrics 2000; 105:1194-1201 [Abstract/Free Full Text]
2. Avery ME, Tooley WH, Keller JB, Is chronic lung disease in low birth weight infants preventable? A survey of eight centers. Pediatrics 1987; 79:26-30 [Abstract/Free Full Text]
3. Horbar JD, McAuliffe TL, Adler SM, Variability in 28-day outcomes for very low birth weight infants: an analysis of 11 neonatal intensive care units. Pediatrics 1988; 82:554-559 [Abstract/Free Full Text]
4. Nonsson B, Katz-Salamon M, Faxelius G, Neonatal care of very-low-birthweight infants in special-care units and neonatal intensive-care units in Stockholm. Early nasal continuous positive pressure versus mechanical ventilation: gains and losses. Acta Paediatr Suppl 1997; 419:4-10 [Medline]
5. Aly HZ, Ades AM, El-Mohandes AN, Early use of nasal prongs continuous positive airway pressure (NP-CPAP) in the extremely low birth weight infants (ELBWI) [abstract]. Pediatric Res 2000; 48:350
6. Lindner W, Vobeck S, Hummler H, Delivery room management of extremely low birth weight infants: spontaneous breathing or intubation? Pediatrics 1999; 103:961-967 [Abstract/Free Full Text]
7. Carlo WA, Martin RJ, Fanaroff AA. Assisted ventilation and complications of respiratory distress. In Fanaroff AA, Martin RJ, eds. Neonatal-Perinatal Medicine: Diseases of the Fetus and Infant. 6th ed. 1997:1028-1111, 1463-1471
8. Zhang S, Garbutt V, McBride JT Strain-induced growth of the immature lung. J Appl. Physiol 1996; 81:1471-1476 [Abstract/Free Full Text]
9. Madansky DL, Lawson EE, Chernick V, Pneumothorax and other forms of pulmonary air leak in newborns. Am Rev Respir Dis 1979; 120:729-737 [Medline]
10. Wung JT. Continuous positive airway pressure. In: Wung JT, Polin RA eds. Respiratory Care of the Newborn: A Practical Approach. New York, NY: Babies and Children's Hospital; 2000
11. Ogden BE, Murphy SA, Saunders GC, Neonatal lung neutrophils and elastase/proteinase inhibitor imbalance. Am Rev Respir Dis 1984; 130:817 [Medline]
12. Pesenti A, Kolobow DK, Pierce JE, Prevention of hyaline membrane disease in premature lambs by apneic oxygenation and extracorporeal carbon dioxide removal. Intensive Care Med 1982; 8:11-17 [CrossRef][Medline]
13. Mascheroni D, Kolobow T, Fumagalli R, Acute respiratory failure following pharmacologically induced hyperventilation: an experimental animal study. Intensive Care Med 1988; 15:8-14 [Medline]
14. Wada K, Jobe AH, Ikegami M Tidal volume effect on surfactant treatment with the initiation of ventilation in preterm lambs. J Appl Physiol 1997; 83:1054-1061 [Abstract/Free Full Text]
15. Young TE, Kruyer LS, Marshall DD, et al. Population-based study of chronic lung disease in very low birth weight infants in North Carolina in 1994 with comparisons with 1984. Pediatrics. 1999;104(2). Available at: http://www.pediatrics.org/cgi/content/full/104/2/e17