Sustained Inflations as the Initiating Positive Pressure Support for Preterm Infants—Not Yet Ready for Prime Time
2014; Elsevier BV; Volume: 165; Issue: 5 Linguagem: Inglês
10.1016/j.jpeds.2014.07.029
ISSN1097-6833
Autores Tópico(s)Infant Development and Preterm Care
ResumoSee related article, p 903The use of prolonged inflations for the support of newborn infants was first reported over 30 years ago with the observations of Vyas et al.1Vyas H. Milner A.D. Hopkin I.E. Boon A.W. Physiologic responses to prolonged and slow-rise inflation in the resuscitation of the asphyxiated newborn infant.J Pediatr. 1981; 99: 635-639Abstract Full Text PDF PubMed Scopus (160) Google Scholar They reported that when giving positive pressure breaths to intubated infants in need of resuscitation, air continued to inflate the lung at 1 second. Prolonging the inspiration to 5 seconds also resulted in improved lung inflation and improved the establishment of a functional residual capacity. Using an inflation pressure that increased over 3 to 5 seconds also avoided an opening pressure. Subsequently, these authors compared face mask breaths with those delivered by an endotracheal tube and found the face mask delivered only one-third of the measured expired volume compared with an endotracheal breath, and was rarely associated with adequate alveolar ventilation.2Milner A.D. Vyas H. Hopkin I.E. Efficacy of facemask resuscitation at birth.Br Med J (Clin Res Ed). 1984; 289: 1563-1565Crossref PubMed Scopus (61) Google Scholar This same group has also shown that preterm infants required more endotracheal breaths to establish adequate ventilation than similarly treated term infants, and had less spontaneous respiration in response to such breaths.3Hoskyns E.W. Milner A.D. Boon A.W. Vyas H. Hopkin I.E. Endotracheal resuscitation of preterm infants at birth.Arch Dis Child. 1987; 62: 663-666Crossref PubMed Scopus (24) Google Scholar More recently, several animal studies have tested the use of much longer inflations of 20 to 30 seconds. The animal studies deliver the sustained/prolonged breaths via an endotracheal tube usually following drainage of lung fluid.4te Pas A.B. Siew M. Wallace M.J. Kitchen M.J. Fouras A. Lewis R.A. et al.Effect of sustained inflation length on establishing functional residual capacity at birth in ventilated premature rabbits.Pediatr Res. 2009; 66: 295-300Crossref PubMed Scopus (126) Google Scholar, 5Klingenberg C. Dawson J.A. Gerber A. Kamlin C.O. Davis P.G. Morley C.J. Sustained inflations: comparing three neonatal resuscitation devices.Neonatology. 2011; 100: 78-84Crossref PubMed Scopus (35) Google Scholar These results are not easily translated to the support of spontaneously breathing preterm infants supported by mask continuous positive airway pressure (CPAP). In the most recent Pediatric Academic Societies meeting, Vancouver, May 2014, one such animal study evaluated prolonged durations of sustained inflation (SI) for up to 97 seconds.6Zonneveld E, Lavizzari A, Rajapaksa A, Black D, Perkins E, Sourial M, et al. A Volumetric-response sustained inflation at birth; towards a patient-defined strategy? e-PAS2014:1180.22014.Google Scholar The delivery of an inflation using an endotracheal tube is much more direct than that delivered using a mask, as there is almost always some degree of leak of the delivered breath around the mask. In addition, it is necessary to ensure that the airway is patent, which is difficult to determine during active human resuscitation. Indeed, the occurrence of airway obstruction during positive pressure inflations immediately following delivery has only been recently described and confirmed.7Leone T.A. Lange A. Rich W. Finer N.N. Disposable colorimetric carbon dioxide detector use as an indicator of a patent airway during noninvasive mask ventilation.Pediatrics. 2006; 118: e202-e204Crossref PubMed Scopus (61) Google Scholar We reported that 18 infants receiving positive pressure inflations had a median of 14 obstructed breaths (range: 4-37 breaths) delivered over a mean and median interval of 56.7 and 45.0 seconds,8Finer N.N. Rich W. Wang C. Leone T. Airway obstruction during mask ventilation of very low birth weight infants during neonatal resuscitation.Pediatrics. 2009; 123: 865-869Crossref PubMed Scopus (137) Google Scholar and Schmolzer et al noted that such obstruction can persist for more than 20 consecutive attempted inflations.9Schmolzer G.M. Dawson J.A. Kamlin C.O. O'Donnell C.P. Morley C.J. Davis P.G. Airway obstruction and gas leak during mask ventilation of preterm infants in the delivery room.Arch Dis Child Fetal Neonatal Ed. 2011; 96: F254-F257Crossref PubMed Scopus (135) Google Scholar The use of such prolonged (sustained) inflations remains controversial and such breaths have not been recommended in the International Liaison Committee on Resuscitation/Neonatal Resuscitation Program consensus statement.10Perlman J.M. Wyllie J. Kattwinkel J. Atkins D.L. Chameides L. Goldsmith J.P. et al.Part 11: Neonatal resuscitation: 2010 International consensus on cardiopulmonary resuscitation and emergency cardiovascular care science with treatment recommendations.Circulation. 2010; 122: S516-S538Crossref PubMed Scopus (535) Google Scholar In this issue of The Journal, van Vonderen et al provide useful and highly relevant information that performing SI on preterm infants <32 weeks gestation is not effective unless the infants breathed during that inflation.11van Vonderen J.J. Hooper S.B. Hummler H.D. Lopriore E. Te Pas A.B. The direct effect of a sustained inflation in preterm infants at birth.J Pediatr. 2014; 165: 903-908Abstract Full Text Full Text PDF PubMed Scopus (72) Google Scholar This kind of observational data acquired during actual resuscitations as opposed to a research study has not been possible in the past because of the lack of clinical instrumentation required to determine if gas actually entered the lung. Such measurements require the use of a gas flow detector or measurements of carbon dioxide during exhalation. The authors have been using flow detectors for a number of years and are thus able to make such observations using a Florian respiratory monitor (hot-wire anemometer; Acutronic Medical Systems AG Zug, Hirzel, Switzerland). These recordings were made on infants who required respiratory support with a face mask and received a SI for 10 seconds at 25 cm H2O, which was the initial strategy utilized at this institution. The authors concluded that although a large mask leak occurred in at least one-third of failures, the majority of failures could be due to active glottis adduction. Data from human trials evaluating the role of SI have been limited as well. A prospective randomized controlled trial compared a 10-second SI delivered via T-piece followed by CPAP through a nasopharyngeal tube with repeated manual inflations using a bag and mask.12te Pas A.B. Walther F.J. A randomized, controlled trial of delivery-room respiratory management in very preterm infants.Pediatrics. 2007; 120: 322-329Crossref PubMed Scopus (202) Google Scholar Twenty cm H2O for the first SI and 25 cm for the second SI were used if the infant was not breathing or had a low heart rate. The control group received an initial peak inspiratory pressure of 30-40 cm H2O using a self-inflating bag and mask with no positive end expiratory pressure. The SI/CPAP group had fewer infants intubated at 72 hours. This result, however, is confounded by the fact that the non-SI group was treated with a face mask initially compared with a nasopharyngeal tube, received higher initial starting peak inspiratory pressure, and received ventilation with a self-inflating bag, which does not provide any positive end expiratory pressure. Thus, although the study reported positive results for the intervention group, this may have been related to the less than optimal management of the control group, and possibly less airway obstruction in the SI group because of the use of a nasopharyngeal tube. Recently, the largest randomized controlled trial of the use of SI during resuscitation was presented.13Gianluca Lista LB, Fabio Scopesi, Fabio Mosca, Daniele Trevisanuto, Hubert Messner, Giovanni Vento, et al. A randomized multicenter clinical trial of sustained lung inflation (SLI) in preterm infants at birth. e-PAS2014:4680.62014.Google Scholar Two hundred ninety-one infants of 25 + 0 to 28 + 6 weeks gestation were randomized to an SI (25 cm H2O for 15 seconds) followed by CPAP or nasal CPAP alone (5 cm H2O). Infants receiving SI had a decreased need for mechanical ventilation in the first 72 hours compared with CPAP alone (53% vs 65%, unadjusted OR 0.57; 95% Cl, 0.38-0.99, P = .043). The incidence of pneumothorax was 6% in the SI group, 1% in the control group (P = .061), a trend that is worrisome.13Gianluca Lista LB, Fabio Scopesi, Fabio Mosca, Daniele Trevisanuto, Hubert Messner, Giovanni Vento, et al. A randomized multicenter clinical trial of sustained lung inflation (SLI) in preterm infants at birth. e-PAS2014:4680.62014.Google Scholar In both of these trials, the number of infants who were not breathing at the time of SI was not recorded. The major implications of the findings by van Vonderen et al is the lack of significant gas exchange and change in functional residual capacity during an SI in an infant with apnea. In a recent study, this same group showed that manual inflations associated with spontaneous breaths were larger for both conventional inflation and SI during resuscitation.14Schilleman K. van der Pot C.J. Hooper S.B. Lopriore E. Walther F.J. te Pas A.B. Evaluating manual inflations and breathing during mask ventilation in preterm infants at birth.J Pediatr. 2013; 162: 457-463Abstract Full Text Full Text PDF PubMed Scopus (68) Google Scholar Of interest, the inflations alone were much smaller during an attempted SI compared with a conventional inflation. Another recent study utilizing the same measurement methods demonstrated that infants with apnea in the neonatal intensive care unit may not recruit lung with positive pressure nasal ventilation.15Louise S. Owen CJM, Davis PG. Effect of synchronized SiPAP-generated nasal intermittent positive pressure ventilation (NIPPV) on tidal volume in preterm infants. e-PAS2014:2936.5052014.Google Scholar The authors of the current study state that obstruction could not have occurred at the pharyngeal level because this would also cause obstruction during inspiration and, in their study, air flow was seen during inspiration. However, an obstruction caused by the tongue falling against the posterior pharyngeal wall could allow air to pass out of the mouth and would be noted as flow and could be interpreted as a leak. In addition, a complete obstruction at the pharyngeal or laryngeal level would result in no air entering the lung and any flow seen during such an attempted inflation could have been a leak. Because such infants are resuscitated in the supine position and many are depressed at birth, it would not be surprising that the flaccid tongue, a respiratory muscle, could easily fall against the posterior pharyngeal wall, particularly in the very preterm infant, who has a degree of macroglossia/micrognathia. It has been reported that airway obstruction in preterm infants is most probably the result of a decrease of upper airway tone, which normally occurs with the cessation of a central respiratory stimulus.16Idiong N. Lemke R.P. Lin Y.J. Kwiatkowski K. Cates D.B. Rigatto H. Airway closure during mixed apneas in preterm infants: is respiratory effort necessary?.J Pediatr. 1998; 133: 509-512Abstract Full Text Full Text PDF PubMed Scopus (36) Google Scholar The site of such obstruction has been previously evaluated in preterm infants, and Matthew et al reported that the obstruction was pharyngeal whereas others have suggested the site to be laryngeal.17Matthew O.P. Roberts J.L. Thach B.T. Pharyngeal airway obstruction in preterm infants during mixed and obstructive apnea.J Pediatr. 1982; 100: 964-968Abstract Full Text PDF PubMed Scopus (63) Google Scholar, 18Ruggins N.R. Milner A.D. Site of upper airway obstruction in preterm infants with problematical apnea.Arch Dis Child. 1991; 66: 787-792Crossref PubMed Scopus (46) Google Scholar As previously noted, an anatomic airway obstruction, as detected by either a colorimetric carbon dioxide detector or a gas flow sensor, is very common, particularly in infants <32 weeks gestation during attempted positive pressure inflations. Armed with this knowledge, resuscitators can use these devices to determine if they are delivering effective inflations. If there is a concern that the airway is obstructed, the operators can then take steps to potentially reestablish a patent airway by mask reapplication, gentle anterior movement of the jaw, and the potential use of small airways or nasopharyngeal tubes in such instances. Without knowledge of the site of the airway obstruction in this trial, the suggestion made by the authors that glottic obstruction could be overcome with higher pressures or a longer duration of SI is somewhat concerning. Their own previous work suggests that the achieved inflation volume is indeed lower with an attempted SI compared with a conventional inflation. That may suggest that prolonged inspiratory pressure or perhaps the preparation for the delivery of SI could potentially alter the holding and positioning of the face mask or the force of application to the infant's face, and these maneuvers could potentially further compromise the airway patency. In addition, higher pressures could theoretically increase the risk of pulmonary air leak as has been noted in the most recent study by Lista et al.13Gianluca Lista LB, Fabio Scopesi, Fabio Mosca, Daniele Trevisanuto, Hubert Messner, Giovanni Vento, et al. A randomized multicenter clinical trial of sustained lung inflation (SLI) in preterm infants at birth. e-PAS2014:4680.62014.Google Scholar Before recommending the use of higher pressures or durations of SI, we suggest that clinicians and investigators consider the use of colorimetric detectors or air flow detectors to rapidly determine if there is an airway obstruction, and that for now, the use of longer inflations should remain an unproven intervention to be evaluated in properly designed and conducted clinical trials. Such trials should include the recording of the delivered volumes and the infants' own respirations, and should consider evaluating both face mask and properly placed nasopharyngeal tubes. We need more prospective evaluations of the physiologic responses to an SI and are grateful for the information provided by van Vonderen et al. Effects of a Sustained Inflation in Preterm Infants at BirthThe Journal of PediatricsVol. 165Issue 5PreviewTo assess the clinical effect of an initial sustained inflation of 10 seconds and 25 cmH2O in preterm infants at birth. Full-Text PDF Open Access
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