Non-invasive mechanical ventilation (NIMV) is an accepted supportive strategy widely used in patients with acute respiratory failure from both hypercapnic and hypoxemic origin.1–4 NIMV can also prevent re-intubation in some cases and might provide comfort at the end of life.5,6 Nevertheless, NIMV can fail because many factors including inappropriate selection of individual cases and patient–ventilator asynchrony.7 Conversely to invasive mechanical ventilation, NIMV is characterized by an open and non-hermetic circuit that is intrinsically leaky. These air leaks pose a challenge for respiratory support because they create a mismatch between the flow provided by the ventilator and the flow effectively delivered to the patient, leading sometimes to considerable asynchrony, discomfort, and ultimately, to fail of NIMV support.

Critically ill patients often require enteral tubes to provide nutritional support or administering medications.8–11 These tubes can increase the risk of air leaks when NIMV is provided through oro-nasal interfaces.12,13 Although air leaks can be clinically challenging, their magnitude might sometimes be reduced by adjusting the patient interface but it can increase the patient's discomfort and cause skin lesions.15 Similarly, specific algorithms for leak compensation have been incorporated into the latest generation of ventilators to reduce these adverse effects with non consistent clinical results.14 Thus, we develop a new tube adaptor for NIMV (TA-NIMV) designed to minimize air leaks by improving the adjust of the oro-nasal interfaces in patients in whom an enteral tube has been placed. In this first report, we evaluate the impact of such TA-NIMV on the reduction of air leaks and the subjective comfort perceived by the patient during NIMV support.

There were 196 patients studied between October 2012 and January 2014. The mean age was 61.2 years (SD, 18.4 years) and 102 (52.0%) were women. The reasons for NIMV were hypoxemia in 113 patients (57.7%), post-operative respiratory distress in 24 (12.2%), pulmonary oedema in 20 (10.2%), hypercapnia in 16 (8.2%) and others in 12 (6.1%). Ninety-nine patients (50.5%) had a naso-enteric tube and 68 (34.7%) a naso-enteric tube. The size of the naso-enteric tube was 12F in 99 patients (50.5%), 14F in 12 (6.1%), 16F in 29 (14.8%), 18F in 15 (7.7%) and 20F in 12 (6.1%). There were 29 patients (14.8%) who required simultaneous use of more than one naso-enteric tube.

The mean washout period between the two interventions was 5.48h (SD, 2.94h). The ventilator mode was control pressure in 142 patients (72.4%), support pressure in 42 (21.4%) and continuous positive airway pressure in 12 (6.1%). The mean FiO2 was 44.6% (SD, 12.3%), and the median PEEP was 7 (IQR, 5–8). Dental prostheses were used in 59 patients (30.1%), and abundant beard was noticed in five patients (2.6%) (Table 1).

Comparisons of the respiratory and hemodynamic parameters between interventions are presented in Table 2. The mean duration was similar (p=0.23) between the TA-NIMV [1.96h (SD, 2.33h)] and the CT-NIMV [1.8h (SD, 2.13h)]. Compared with the CT-NIMV group, the TA-NIMV group had significantly higher mean ITV [496.4 (SD, 98.7) vs. 452.3 (SD, 102.0); p<0.001]; mean ETV [502.6 (SD 101.0) vs. 457.7 (SD, 98.8); p<0.001)] and mean SO2 [97.6% (SD, 1.9%) vs. 96.0% (SD, 2.7%); p<0.001)]. The mean respiratory rate and heart rate were significantly lower in the TA-NIMV group than in the CT-NIMV group (Table 2).

Evaluating comfort after the intervention was possible in 99 patients with a GCS of 15. After TA-NIMV 59 patients (59.6%) reported being comfortable, and 25 patients (25.3%) reported being very comfortable. After CT-NIMV, 14 patients (14.1%) reported being comfortable, while only three patients (3.0%) reported being very comfortable. The use of TA-NIMV was significantly more comfortable than CT-NIMV when PCV or PSV modes were used (Fig. 4).

Fig. 4.

Comparisons comfort between interventions. (a) Percentage of comfort perception during TA-NIMV and CT-NIMV in all patients evaluated (n=99), p<0.001. (b) Percentage of comfort among patients on pressure support mode, (n=67), p<0.001. (c) Percentage of comfort among patients on pressure control mode, (n=26), p<0.001. (d) Percentage of comfort among patients on continuous positive airway pressure ventilation mode, (n=6), p<0.261. Differences between groups were tested using the marginal homogeneity test (Stuart–Maxwell).

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In all patients (n=196), the mean air leak percentage was 9.2% (SD, 7.7%) during TA-NIMV and 32.5% (SD, 12.5%) during CT-NIMV (p<0.001). Subgroup analyses by the numbers and sizes of naso-enteric tubes showed that the air leak percentages were significantly lower with TA-NIMV than with CT-NIMV (Table 3).

In this study, we presented the feasibility and actual effectiveness of a device designed by our hospital ICU staff. Our results suggested that using the new tube adaptor for NIMV administered, via an oro-nasal mask in patients with one or two naso-enteral tubes, improved patient comfort and significantly decreased the air leakage volume. The statistically significant lower sir leak percentages with TA-NIMV than with CT-NIMV were consistent among all subgroup analyses.

NIMV had been shown to significantly decrease mortality,21 but the factors that determine its success are based on adequate tolerance and the patient's comfort. Previously conducted studies have proved that the magnitude of air leaks is correlated with the number of ineffective breaths and severity of delayed cycling, both of which play important roles in generating patient–ventilator asynchrony and discomfort.19 We designed our device aiming to decrease air leaks to improve patient comfort. Moreover, we observed that patients who were placed on TA-NIMV had higher comfort levels than those who were not placed on TA-NIMV. Our device possibly had beneficial effects even though we did not measure patient–ventilator asynchrony metrics.

Significant air leaks can induce a pressure drop or generate flows that are perceived as patient inspiratory effort. These inevitably results in auto-triggering, which is a highly undesirable phenomenon that can be resolved only by reducing triggering sensitivity. This reduction in triggering sensitivity reportedly leads to late cycling or failure to trigger in 12%–23% of patients.19

When a tube adaptor was added to the NIMV, approximately 85% of patients with GCS of 15/15 confirmed that they felt comfortable or very comfortable. By utilising a special mask that engaged the naso-enteric tubes based on a scale of 1 to 5, our results were consistent with those obtained by Gregoretti et al.,22 who reported significant improvement with respect to patient comfort levels.

We described the effects of a new device that decreased air leak in cases treated with NIMV via an oro-nasal mask with concomitant use of one or two naso-enteric tubes. These findings were consistent regardless of the number and size of the naso-enteric tubes. Few articles have reported using tube adaptors in NIMV.22 Moreover, much less is known about the comparative effectiveness between a mask prototype with a port for the naso-enteric tube and a conventional mask. A case report demonstrated that using a special endoscopy mask with a 16F probe for the enteral tubes reduced the risks of failure and improved NIMV quality in two patients.23 At the moment, there had been no reports on using NIMV oro-nasal mask in patients who needed more than one enteric tube.

Our results showed using the tube adaptor maintained the air leak percentage below 10%, except in the subgroup of patients with 20F enteric tubes; in that group, the air leak percentage reached slightly above 10%. Nevertheless, the differences between TA-NIMV and CT-NIMV were statistically significant, and the air leak percentage was much higher with CT-NIMV. Reducing the air leak percentage with our new device may improve the outcomes of critically ill patients who usually require multiple interventions.

Current ventilators can be programmed to deliver between 40L/min and 65L/min to compensate for air leaks.24 However, excessive air leaks cannot be well compensated, and the use of NIMV becomes ineffective when air leaks exceed 20%.25,26 In particular, this is an important finding for institutions in low- to middle-income countries, which rarely have such technology.

The use of a tube adaptor to adjust NIMV mask interfaces in patients in whom oro- or naso-enteral tubes are in place, significantly reduces air leaks and improves subjective comfort perceived by the patient during NIMV support.

Oscar I. Quintero: Conception and design of the study, writing the core content of the study, analysis and interpretation of data, drafting the article or revising it critically for important intellectual content.

Alvaro I. Sanchez: Writing the core content of the study, coordinated delivery of interventions, analysis and interpretation of data, preparation and critical review of the manuscript.

Paola A. Chavarro: Writing the core content of the study, coordinated delivery of interventions, analysis and interpretation of data, preparation and critical review of the manuscript.

Isabel C. Casas: Writing the core content of the study, analysis and interpretation of data, preparation and critical review of the manuscript.

Gustavo A. Ospina Tascón: Writing the core content of the study, coordinated delivery of interventions, analysis and interpretation of data, preparation and critical review of the manuscript.

All authors declare their approval for the current version of the manuscript.

This work was funded by Fundación Valle del Lili (Centro de Investigaciones Clínicas), Grand 00576/12.

The authors declare one conflict of interest. Fundación Valle del Lili has the device patent of the tube adapter for non-invasive mechanical ventilation. The patent number 1165 is registered at the Colombian Patent and Trademark Office (Superintendencia de Industria y Comercio de la Republica de Colombia). International publication is WO2014188242A1 of World Intellectual Property Organization.