Transient tachypnea of the neonate (TTN) is diagnosed in approximately 2% of live births, accounting for the majority of respiratory distress cases in term and late preterm babies. Transient tachypnea of the neonate is a benign, self-limited condition characterized by abnormal fluid overload resulting from delayed clearance of fetal lung fluid. Its management is generally supportive and oxygen is usually provided by hood or nasal cannula.1 On the other hand, some newborns with TTN demonstrate increased work of breathing under supplemental oxygen, and cannot maintain their oxygen saturation above 90%. Given its pathophysiology, nasal continuous positive airway pressure (nCPAP) could be a useful support for neonates with TTN.2

Non-invasive ventilation (NIV) strategies have become the standard for respiratory support in spontaneously breathing newborns.3–5 Various nasal interfaces including bi-nasal short prongs, long nasopharyngeal prongs or nasal masks are currently available to provide nCPAP. Bi-nasal short prong devices are known to be more effective than single prongs in reducing the likelihood of short-term adverse outcomes of re-intubation and respiratory failure in newborns.6,7 Although various nasal interfaces are available to provide nCPAP in newborns, only few studies have compared these devices with respect to effectiveness and side effects, including nasal skin breakdown.8–11

Monitoring functional residual capacity and trans-pulmonary pressure (PTP) represents an opportunity to individualize the interpretation of lung mechanics, and guide development of a ventilator strategy tailored to a given patient.12 Esophageal pressure (Pes) has been proposed as a surrogate for pleural pressure and allows the calculation of PTP, and provides a mean to guide the management of ventilated patients.13

Physiological principles of nCPAP are established on the generated continuous distending pressure by the device and the pressure transmitted to the proximal and the distal airways by the nasal interface used. Up to now, clinical studies on nasal interfaces have generally evaluated their efficacy and safety with respect to clinical outcomes.6–11 In this study, we aimed to prove the hypothesis that nasal mask can be as effective as bi-nasal prong which is the most effective interface. For this purpose, Pes and calculated PTP (cPTP) measurement with clinical results were evaluated with both interfaces in infants with TTN who were assisted with nCPAP.

During the study period, of the 483 infants admitted to the NICU, 178 had respiratory distress, 116 of them were excluded: 36 for requiring only free flow oxygen (O2), 20 for requiring intubation, 35 for being born before 32 weeks of gestation and diagnosed as RDS and/or pneumonia, 4 for having congenital airway malformations and 21 for refused informed consent. Sixty-two of the patients needed nCPAP for TTN and were eligible for the study. They were subsequently randomized to two study groups so as to have 31 infants in each group (Fig. 1).

The mean GA and BW of study infants were 36.7±2.31 weeks and 2900±755g, respectively. Male to female ratio was 1.95. The study groups were comparable with respect to GA, BW, gender, being born by cesarean section, having received antenatal steroids and positive pressure ventilation in the delivery room, as well as 1st and 5th minute Apgar scores (Table 1).

Mean Pes and calculated PTP values with nasal mask and bi-nasal short prongs during inspiratory and expiratory courses of breathing at the 1st, 6th, 12th and 24th hours are given in Table 2. Inspiratory and expiratory Pes (Fig. 3) and cPTP values (Fig. 4) at the 1st, 6th, 12th and 24th hours were similar in the study groups. Applied PEEP and FiO2 values were not significantly different in the study groups at the designated time intervals (Supplementary material 1 Table 3).

Fig. 3.

Esophageal pressure measurements during inspiratory and the following expiratory.

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Fig. 4.

Calculated trans-pulmonary pressure measurements during inspiratory and the following expiratory phase at 1st, 6th, 12th, and 24th hours.

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The incidence of nasal trauma was 6.4% in the entire study group. Although the incidence of any stage nasal trauma was higher in the bi-nasal short prong group, the difference between groups was insignificant (P=.113). Four patients with nasal trauma in the bi-nasal prong group had only mild (Stage I) injury. Durations of oxygen supplementation and nCPAP were similar. Pneumothorax requiring a chest tube developed in one patient in the bi-nasal prong group, and one patient in the nasal mask group had pneumomediastinum (Supplementary material 2 Table 4).

Our data demonstrates that a nasal mask is similarly effective as bi-nasal short prongs during a brief period of respiratory support by nCPAP in late preterm and term neonates. Pes and cPTP values during both the inspiratory and expiratory phases of breathing at the 1st, 6th, 12th and 24th hours were similar in patients who were treated with nCPAP via nasal mask and bi-nasal short prongs at similarly applied PEEP and FiO2. Nasal injury was insignificantly less with the nasal mask. Respiratory care was performed as standard in all patients treated with NIV in both nasal mask and bi-nasal prong groups. Standard respiratory care and similar PEEP were applied to each patient in both groups, and cPTP and Pes pressures were determined to be similar in the same patient treated with different interfaces. PEEP values between groups were found to be similar. In the same patient, cPTP and Pes values were measured similarly at both interfaces. Visual differences in the distributions seen in Figs. 3 and 4 were given as mean±standard deviation, and the measured values were not statistically different. These results showed that there was no difference in similar PEEP pressure in terms of cPTP and Pes pressures measured in the lungs via both interfaces. Our results showed that nasal mask was as effective as bi-nasal prong. Unlike the studies comparing the efficacy of the two interfaces, our study was the first to evaluate clinical outcomes as well as lung pressure.

There is insufficient data on the effectiveness of the interfaces for nCPAP in late preterm and term infants in the literature. Although a meta-analysis showed that bi-nasal short prong devices were more effective than single prongs in reducing the rate of re-intubation in preterm infants, there is only scant information on nasal mask application.7 Kieran et al. reported that nCPAP with a nasal mask was more effective in prevention of intubation and mechanical ventilation within 72h of starting therapy than bi-nasal short prongs in preterm infants (52% vs. 28%, P=.007).10 The effectiveness of nCPAP via nasal mask was evaluated with respect to clinical outcomes in their preterm population. Our study groups mostly comprised late preterm and early term infants with TTN. Due to the generally benign and self-limited nature of TTN, the number of patients who needed respiratory support with nCPAP was small, the duration of nCPAP was short and the probability of either intubation or nasal trauma was low. Therefore our primary aim was to evaluate the efficacy of transmission of positive pressure to distal airways via either nasal interface.

Esophageal pressure measures pleural pressure in the lung surrounding the esophagus reliably. It may therefore underestimate pleural pressure of the dependent regions and overestimate pleural pressure of the nondependent zones.15 It has been proposed as a surrogate for pleural pressure that allows the calculation of PTP. Pleural pressure ranges widely and unpredictably in elderly patients with acute respiratory distress, due to factors such as obesity and abdominal fluid accumulation, which influence the mechanical behavior of the chest wall.13 It is well accepted that the respiratory changes in Pes are representative of changes in pleural pressure applied to the lung surface.13,18 Esophageal pressure can be used to estimate the PTP during static maneuvers, as a guide to setting PEEP in the adult studies.13 Lavizzari et al. used Pes and PTP in infants with RDS for lung mechanics to compare the efficacy of heated, humidified, high flow nasal cannula and nCPAP. They concluded that both methods provided similar effects on pleural pressure estimated by esophageal pressure.19 Although the results of only a very few studies appear encouraging, data fostering the clinical usefulness of Pes to support decision-making during acute respiratory distress are very limited.15 We used Pes measurements with two different interfaces to determine the effect of each interface on PTP values in the same patient. When the nasal mask was on, expiratory cPTP yielded a statistically insignificant but lower pressure value than bi-nasal short prongs. We can speculate that the work of breathing during the expiratory phase of breathing might be less with a nasal mask.

Assessment of PTP is a minimally invasive technique that allows better assessment of the physiological effects of two separate modes of respiratory support on lung mechanics.15 We used Pes and calculated PTP as surrogates for the pressure transmitted to the proximal and distal airways by two different interfaces used for the same mode of respiratory support (nCPAP), and compared their effectiveness. We found that Pes and PTP were similar with nasal and short bi-nasal prongs during a brief period of respiratory support with nCPAP in infants with TTN. We can conclude that the nasal mask is similarly effective as short bi-nasal prongs in transmitting the pressure generated by the nCPAP device in late preterm and term newborns. To our knowledge, this is the first study performed using Pes and PTP for comparing the effectiveness of nasal interfaces used for non-invasive respiratory support.

The incidence of skin breakdown associated with nasal CPAP in the neonate is high and has been reported to be between 20 and 60%.11 Type of the nasal interface, incorrect sizing and positioning of the prongs, length of therapy, ambient humidity and temperature are the most commonly reported risk factors for nasal injury. Specifically smaller infants, who are prone to longer duration of respiratory support are at the greatest risk.11,20,21 The onset of injury to the nasal columella has been reported to occur within a mean of 2–3 days after commencement of nCPAP, with some cases occurring as early as 18h after commencement.20,21 Overall incidence of nasal injury was low (6.4%) in our study group. This may be attributed to the brief duration of nCPAP in relatively larger infants with higher gestational age and birth weight. Compared to bi-nasal prongs, the nasal mask has been reported to cause less or equivalent nasal injury.11 Incidence of mild (Stage 1) nasal injury was insignificantly higher with bi-nasal short prongs in our study. Four patients in the bi-nasal prong group and none of the patients in the nasal mask group had nasal injury. This finding cannot enable a conclusion that the nasal mask is safer than bi-nasal prongs, but we can at least conclude that the nasal mask is as safe as bi-nasal prongs.

However, our study has some limitations. First, due to the usual favorable outcome of TTN, the number of subjects for direct measurements decreased at later time intervals. This prevents us from making any conclusions with respect to measurements and nasal injury for the interfaces during prolonged nCPAP. Second, because our patient population consisted of relatively mature newborns, we could not make any conclusions especially for extremely preterm infants who are the primary candidates for long-term respiratory support.

This is the first study done using esophageal pressure and transpulmonary pressure for comparative effectiveness of nasal interfaces used for respiratory support. Our study demonstrates that nCPAP therapy with a nasal mask is as effective as bi-nasal short prongs in neonates in late preterm and term infants.

The trial supported by Ankara University Research Fund. Project number: 13B3330008.

The authors declare no conflict of interest.