Respiratory distress syndrome (RDS) is a major problem of preterm births and remains an important contributor to morbidity and mortality [1,2]. Mortality can be as high as 50% in low-income countries. Infants with RDS needing mechanical ventilation (MV) can require inter-hospital transfers [3-5].

Current international recommendations for the treatment of preterm infants with respiratory distress syndrome (RDS) suggest early administration of surfactant and continuation of non-invasive modalities instead of elective intubation [6,7].

There are some well-known practices for delivering surfactant while continuing non-invasive respiratory support. These include intubation followed by early extubation (INSURE), or the use of a thin catheter to administer surfactant during ongoing nasal CPAP support (known as less invasive surfactant administration, LISA, or minimally invasive surfactant therapy, (MIST). These practices involve laryngoscopy to visualize the vocal cords in order to pass an endotracheal tube or catheter [8-10].

The European RDS consensus guideline, recommend MIST as the preferred mode of surfactant administration to surfactant deficient babies who are spontaneously breathing on CPAP [11]. This is on the premise that clinicians have the requisite expertise.

Due to the changing practice with increased emphasis on non-invasive support, the number of clinicians with adequate experience in intubation has reduced markedly. In addition, quite a number of adverse events are associated with intubations, particularly when laryngoscopy is performed without pre-medication [12,13].

The use of the laryngeal mask airway (LMA) in new-born resuscitation is well recognised and taught in Neonatal Life Support training by Resuscitation Council UK. The laryngeal mask airway can be easily passed to form a seal over the laryngeal inlet without laryngoscopy. The adverse effects attributable to the use of this supraglottic device are rare. Available reports show that the LMA can be successfully inserted to give surfactant by a wide range of health practitioners including paediatricians, and neonatal nurse practitioners with little training [14-17].

Limited studies available regarding surfactant administration via the laryngeal mask airway has included moderately preterm babies, at least 28 weeks gestational age, weighing greater than 1000g [18-21].

We introduced LaMAS to treat eligible babies with RDS, who were at least 25 weeks gestation, with birth weight ≥ 750 grams. All grades of medical staff and advanced neonatal nurse practitioners received training during the period. We present the outcomes of the 26 babies treated in the first year starting March 2024.

All the infants had clinical and/or radiological evidence of RDS on optimal CPAP. RDS requiring surfactant is defined as per European consensus as all babies requiring Fio2 ≥ 0.30 to maintain oxygen saturation in target range for gestation. Surfactant could also be delivered to babies with significant work of breathing and chest x-ray showing severe RDS, on clinician discretion. Infants requiring CPAP up to 8cm were eligible for LaMAS. Contraindications to LaMAS included imminent need for intubation and ventilation, maxillo-facial, airway or pulmonary malformations and pneumothorax.

All infants were adequately swaddled and most infants received atropine premedication intravenously. An appropriately sized, well lubricated LMA was then passed and optimal position verified with a colorimetric carbon dioxide detector. Babies weighing < 1500g required a size 0 Air-Q LMA and those weighing > 1500 grams required size 1 igel passed. Intermittent positive pressure ventilation was provided as required. Surfactant was administered at a dose of 200mg/kg (not exceeding 480mg) via a catheter inserted through a neopuff T-piece circuit with a duckbill port over 2-3 minutes.

We recorded the number of attempts at LMA insertion, proportion of surfactant aspirated from the stomach, adverse events during the procedure (bradycardia <100/min, pneumothorax) as well as the clinical response to surfactant administration. We also documented the need for intubation within 72 hours of the procedure.

Setting

Our neonatal intensive care unit based in Swansea, is one of three tertiary centres in Wales that manages non-surgical patients from 22 weeks gestation.

The median (range) gestational age and birthweight were 34 weeks (25+5 to 40+5) and 2464g (770 to 4115g). There was a 100% success rate in LMA insertion, 96 % of which were on first attempt. The grade of clinician carrying out the procedure had no bearing on successful placement of the LMA.

Table 1: Demographics.

The median (range) postnatal age at surfactant administration was 7.8 hours (0.6 to 22.5 hours). Premedication (intravenous atropine 20 microgram/kg) was given to 24 babies, while one was performed in the labour ward successfully without premedication.

Oxygen requirement FiO2 ≥ 0. 30, was the indication for surfactant administration in 80% of the cases, while the remaining were a combination of increased work of breathing, respiratory acidosis and RDS changes on chest radiograph.

The proportion of surfactant aspirated from the stomach post-procedure is the means of determining surfactant delivery to lungs. In this cohort, 21 (80%) had 100% delivery into the lungs, the median (range) of aspirated surfactant was 2.9% (0 to 35%). In terms of cardiorespiratory stability during the procedure, two infants (8%) had significant bradycardia, which were promptly addressed by providing IPPV. In our experience, reflux of the surfactant through the LMA was quite common and this was managed by slow administration over three to five minutes with provision of IPPV to disperse the surfactant.

Table 2: Adverse events.

With respect to the clinical response, 22 (85%) of the babies had significant improvement within two hours of treatment and were maintained on CPAP, while four (15%) of the babies required intubation subsequently. The indications for intubation include pneumothorax, meconium aspiration syndrome and persistent respiratory acidosis. None of the very low birth weight babies (< 1500g) required intubation.

The babies in this cohort include extremely low birth weight babies, smaller than those in other studies [18-21]. The success rate on first attempt of LMA insertion was higher than that reported in a recent report, this may be attributed to the fact that we had a size 0 LMA available [20].

The intubation rate following LaMAS in this cohort is similar to that of MIST [8,9]. When compared to other LaMAS reports, the intubation rate was identical to or lower than previously documented [19-21]. Although the numbers were small, babies with significant increased work of breathing and marked respiratory acidosis were more likely to be intubated post LaMAS.

In LaMAS, as well as MIST, inadvertent oesophageal administration of small amounts of surfactant is well recognised. In this cohort we demonstrated 100% delivery to the lungs in 80% of the cases and minimal gastric aspirates in 20%. Other studies have not provided this information, to demonstrate the effectiveness of surfactant delivery via LaMAS.

This relatively novel technique for surfactant administration, is easy to perform and effective with minimal adverse events. This case series included smaller, more premature babies than previously reported with similarly good outcomes. In our experience, LaMAS provides better cardiorespiratory stability than MIST due to the provision of IPPV. There is ongoing work to compare the effectiveness and cardiorespiratory stability with MIST.

A notable limitation of LaMAS is the restriction in volume of surfactant that can be given. Smee who had a larger cohort recommend a maximum dose of 480mg. Our findings corroborate this, it was observed that administering doses greater than 480mg (6 ml) can be challenging, as this is associated with bradycardia and significant regurgitation of surfactant. Therefore, babies weighing > 2500g end up getting less than 200mg/kg of surfactant.

The training and additional equipment required to perform this procedure is minimal. This method may be the ideal way to give early surfactant even in extreme preterm babies ≥ 750g, who are relatively stable on CPAP to avoid intubation. For moderate to late preterm babies with RDS in non-tertiary neonatal units, LaMAS can be a good option of administering surfactant, to maintain non-invasive respiratory support, thereby avoiding inter-hospital transfer for invasive ventilation.

More adequately powered trials are required to determine the effectiveness and safety of LaMAS in the early treatment of RDS in extremely low birth weight infants.

What is Already Known: Surfactant can be administered effectively via laryngeal mask airway in VLBW infants with RDS.

What this Study Adds: LMA surfactant administration is feasible and effective in ELBW infants. Surfactant delivery to the lungs through this technique is excellent.

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