Clinical performance and safety profile of the RAM cannula as an interface for post-extubation noninvasive ventilation: an observational study in preterm newborns

Introduction

Preterm newborns frequently present with hyaline membrane disease due to immaturity and surfactant deficiency, which leads to respiratory failure. The incidence of respiratory distress syndrome is inversely related to gestational age and is highest among preterm infants born at less than 29 weeks of gestation, with the consequent need for endotracheal intubation and surfactant administration. Avoiding mechanical ventilation in these patients results in a reduction in lung injury, bronchopulmonary dysplasia, hypoxia, and brain damage, as well as airway injuries and infections associated with mechanical ventilation.

The RAM cannula is a binasal interface with a larger-than-usual internal diameter. It is designed specifically for the early application of continuous positive airway pressure. Owing to its unique design, it allows for the delivery of sufficient flow and pressure according to the requirements of the newborn. The objective of this study was to describe the clinical performance and safety profile of noninvasive ventilation with a RAM cannula in preterm infants with respiratory distress and to analyze its relationship with the clinical outcomes observed in our population, specifically ventilation failure and the occurrence of associated nasal injury. We also evaluated the incidence of nasal injuries linked to the use of the RAM cannula compared with that reported in the literature.

Despite the resistance observed in some neonatal units to adopting the RAM cannula as a noninvasive ventilation interface, the available evidence suggests that, by optimizing ventilatory parameters, its effectiveness could be comparable to that of conventional interfaces.

Objective

To describe the clinical performance and safety profile of the RAM cannula used as a postextubation ventilatory support strategy in preterm infants and to analyze the clinical and demographic factors associated with failure of the technique in our population.

Materials and Methods

An observational, analytical, and retrospective study was conducted in a Level IIIB maternity ward. The data collection period was from May 2023 to May 2025 and included 32 newborns weighing less than 1500 g who used postextubation ventilatory support with the RAM cannula interface during their hospitalization.

The ventilatory support protocol was initiated using a resistance-compensating strategy, with parameters set to 2 to 3 cmH₂O higher than the standard levels. Specifically, a peak inspiratory pressure of 17/18 cmH₂O and an end-expiratory positive pressure of 7/8 cmH₂O were set, with the aim of ensuring an effective distal pressure equivalent to a 15/5 cmH₂O setting in conventional noninvasive ventilation.

Under these conditions, the effectiveness and complications associated with the use of the RAM cannula were evaluated, and associations with adverse clinical outcomes were established. Special attention was given to skin integrity, and the severity of nasal septum lesions was classified through standardized clinical inspection for erosions, ulcerations, or deformities attributable to the interface.

Failure of RAM cannula use was defined as the need for therapeutic escalation to invasive mechanical ventilation within the first 48 hours. This outcome was determined by the presence of gasometric failure—defined as respiratory acidosis with a pH less than 7.20 and hypercapnia with a partial pressure of carbon dioxide greater than 60 mmHg—persistent requirements for an inspired oxygen fraction greater than or equal to 0.40 or significant clinical deterioration.

Maternal variables (hypertension, diabetes, cholestasis, and preterm birth), perinatal variables (delivery mode and antenatal corticosteroid treatment), and neonatal variables (gestational age, birth weight, sex, and Apgar score) were collected. With respect to clinical variables, the need for surfactant, days of cRAM use, total days of mechanical ventilation, and maximum values of PCO₂ and FiO₂ were recorded. Continuous variables are expressed as the mean ± standard deviation. Comparisons were performed using the χ² test or Fisher’s exact test for categorical variables and Student’s t test for continuous variables. A p value < 0.05 was considered to indicate statistical significance.

Results

A total of 32 preterm newborns who met the inclusion criteria during the study period were included in the analysis. The population had a mean gestational age of 28.06 ± 1.9 weeks and a mean birth weight of 1063 ± 178 g.

With respect to perinatal history, 59% of the births were by cesarean section, and 69% received full lung maturation with antenatal corticosteroids. The need for exogenous surfactant was high, with 91% of the cohort receiving it. The baseline demographic and clinical characteristics of the population are detailed in Table 1.

Clinical outcomes and NIV failure

The RAM cannula was used as a postextubation support interface, with a mean duration of use of 11.7 ± 8.9 days. The failure rate, defined as the need for reintubation and escalation to invasive mechanical ventilation within the first 48 hours, was 19% (6/32 patients). The remaining 81% (26/32) successfully maintained noninvasive ventilation.

Analysis of Factors Associated with Failure

When the baseline demographic variables, such as birth weight (978 g vs 1083 g; p=0.20) and gestational age (28.1 weeks vs 28.0 weeks; p=0.88), did not significantly differ between the groups of patients who experienced NIV failure (n=6) and the group of patients who did not experience NIV failure (n=26). No significant differences were found in the Apgar scores or in the incidence of maternal conditions (hypertension, diabetes, and cholestasis) (Table 2).

Bivariate analysis revealed significant associations between perinatal history and developmental complications. First, a history of premature rupture of membranes (PROM ≥ 18 h) was significantly more frequent in the successful group (32% vs. 0%; p=0.003) and was associated with tolerance of extubation.

The group in which NIV failed had a significantly higher incidence of intraventricular hemorrhage (IVH) than the group in which NIV was successful (33% vs. 0%; p=0.002). Similarly, a strong association was found between method failure and the presence of nasal injuries: 33% of patients who required reintubation had some degree of injury, while no such events were recorded in the group that successfully continued with the RAM cannula (p=0.002).

Finally, although it did not reach statistical significance (p=0.11), a clinically relevant percentage difference was observed in retinopathy of prematurity (ROP), which was more prevalent in the failure group (67%) than in the success group (31%).

Safety profile

The overall incidence of nasal injuries in the total cohort was low, occurring in only 2 of the 32 patients (6%). No serious adverse events directly attributable to interface malfunction were recorded.

*Statistical significance determined using Fisher’s exact test.

Study limitations: The retrospective, single-center design, along with the small sample size, limits the generalizability of the results and causal inference. The absence of a

control group, the lack of an internationally validated scale for injury grading, and the reliance on ventilatory settings based on local clinical practice constitute potential sources of bias.

Discussion

In this retrospective observational study, the use of the RAM cannula as a postextubation noninvasive ventilation interface was associated with a failure rate of 19%, which is comparable to the failure rate reported in the literature for CPAP in preterm infants, which ranges from 12% to 25% depending on the series [5, 7].

After the perinatal history was analyzed, a statistically significant difference in the incidence of premature rupture of membranes (PROM ≥ 18 h) (p=0.003) was observed. Interestingly, this history was exclusive to the success group (32% vs. 0%), which could suggest a possible effect of stress-induced pulmonary maturation in these patients, favoring tolerance to extubation.

On the other hand, with regard to morbidities, the pattern of retinopathy of prematurity (ROP) stands out. Although the difference did not reach statistical significance (p=0.11), likely because of the small sample size of the failure group (n=6), a clinically relevant percentage difference was observed: 67% of patients in the failure group had ROP, compared with only 31% in the success group. These findings suggest that the failure group consists of patients with greater systemic instability and greater exposure to oxygen fluctuations, although a larger sample size is needed to confirm the statistical association.

The most relevant finding and the main strength of this interface in our study lies in its favorable safety profile, particularly regarding the low incidence of nasal injury observed. The incidence of nasal injury was 6%. This figure is notably lower than that historically reported for short binasal prongs or masks, which can reach 40–50% in some reports [8]. Our findings are consistent with those of a recent meta-analysis by Kumar et al. [9] and a clinical trial by Al-Lawama et al. [2], who described the RAM cannula as a significantly less traumatic interface (RR 0.34 for nasal injury). Although we observed a significant association between the presence of nasal injury and NIV failure (p=0.002), the low overall event rate suggests that this interface effectively protects the integrity of the nasal septum.

From a physiological standpoint, we acknowledge that the RAM cannula is not the “gold standard” because of its high-flow-resistance design, which can result in lower-than-programmed distal pressure delivery [1]. However, our results suggest that this mechanical limitation can be successfully overcome in clinical practice by adjusting respiratory parameters in a compensatory manner.

The need to use higher set pressures (PIP 18/PEEP 8) in our cohort is due to the intrinsic mechanical properties of the interface. As demonstrated by Claassen et al. (2020), compared with a set value, a RAM cannula acts as a high-resistance interface that can attenuate distal pressure transmission by up to 35% [10]. In their in vitro and clinical trials, these authors concluded that a compensatory increase in set pressure is essential for achieving effective lung inflation and reducing the failure rate of noninvasive ventilation, a finding that aligns with the high success rate observed in our study when this compensation strategy was applied.

This strategy could allow the RAM cannula to offer clinical performance comparable to that of other interfaces in daily practice but with the critical advantage of causing less nasal injury. This position makes it a potentially useful tool within the therapeutic arsenal, especially in settings with a high incidence of readmission to the ICU due to severe nasal trauma caused by rigid devices.

Finally, this combination of a low injury rate and ease of placement positions the RAM cannula as a pragmatic and valuable alternative for healthcare settings with limited resources or a low nurse-to-patient ratio. In these settings, where the continuous and meticulous monitoring required by stiffer interfaces to prevent septal necrosis is difficult to sustain, the RAM cannula offers a safe option that could facilitate nursing care, without showing an increase in ventilatory failure in our cohort.

Conclusion

In this cohort of preterm infants, the use of the RAM cannula as a postextubation noninvasive ventilation interface was associated with a failure rate of 19%, comparable to that reported in the literature, and with a very low incidence of nasal injury (6%).

Although the resistance of the cannula is greater than that of traditional interfaces, our findings suggest that, with appropriate parameter adjustment, the RAM cannula may constitute an effective alternative for postextubation ventilatory support, with a low risk of nasal injury.

Its ease of use makes it a potentially useful alternative, especially in healthcare settings with limited resources or understaffing, where minimizing care-related trauma is a priority for treatment success.

References

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