Enteral Nutrition During Noninvasive Ventilation: We Should Go Deeper in the Investigation—Reply

In reply:

We thank Stefano Bambi and colleagues for highlighting these common concerns regarding the introduction of enteral nutrition during noninvasive ventilation (NIV) for acute respiratory failure. In our protocol, we use a nasogastric tube 8–12 French in diameter. Nasogastric tubes were inserted only in the enteral nutrition group. According to the guidelines,¹ we use prokinetic agents for patients at high risk for aspiration, including those who have had an episode of vomiting or a high gastric volume, although we could not confirm the details of this point retrospectively.

As Bambi et al² have mentioned, the recent enteral nutrition guideline by the American Society for Parenteral and Enteral Nutrition no longer recommends using gastric residual volume as a routine care criterion for withholding enteral nutrition inappropriately. However, there is a trial suggesting an association between vomiting and a gastric residual volume of > 250 mL.³ We also need to emphasize that the enteral nutrition protocol we use for ventilated subjects was mainly intended for those receiving invasive ventilation. Vomiting is much more critical for patients with NIV than for those with invasive ventilation, so we routinely assessed gastric residual volume and selected 250 mL as the tolerability threshold.

We use morphine or fentanyl to relieve patient dyspnea. In our protocol, we started morphine at 0.02 mg/kg/h and fentanyl at 0.05–0.1 μg/kg/h by continuous infusion and increased or decreased the rate depending on the subject's symptoms.⁴ To treat acute changes in dyspnea, we also use bolus infusion at 1-h doses intermittently as tolerated. Although an emetic adverse effect is associated with opioids, one of the 2 subjects who vomited during enteral nutrition was not being administered opioids. Our study also showed no relationship between airway complications and opioid use in univariate analysis. For these reasons, we concluded that enteral nutrition was an independent risk factor of airway complications, although the number of vomiting events was too small to confirm the actual effect of opioids.

In our study, 67 of 107 subjects (63%) used bi-level NIV mode (spontaneous/timed) and the rate of spontaneous/timed mode to CPAP mode was not significantly different between the enteral nutrition and no-enteral nutrition group (63% vs 61%, P = .86). There was no difference in the rate of airway complications between spontaneous/timed mode and CPAP mode (49% vs 35%, P = .15).

As we showed in Table 1, the median (interquartile range) of inspiratory positive airway pressure was 10 (8–14) cm H₂O in the no-enteral nutrition group, and 10 (8–12) cm H₂O in the enteral nutrition group (P = .93).⁵ Bambi and colleagues suggested the benefit of a helmet interface to reduce airway complications of NIV. The helmet pressurizes gas flow indirectly to the airway and allows patients to expectorate. It could improve clearance of sputum and reduce the risk of aspiration when patients vomit.⁶ In fact, recent evidence suggested a lower intubation rate with a helmet than with a face mask among subjects with ARDS, where half of the included subjects had pneumonia or aspiration.⁷ However, there have been only a limited number of trials, and large, randomized, controlled trials are still needed to provide more robust evidence.

In conclusion, we are confident about our scientific data on enteral nutrition and airway complications in subjects with NIV and our emphasis on the need for special concern. There is no validated strategy, including the helmet or nursing care suggested by Stefano Bambi, to reduce the critical complications of enteral nutrition among patients with NIV. We need more evidence about this topic.

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