Methodological considerations in combined noninvasive ventilation and mechanical in-exsufflator.

It is our pleasure to read the comments sent to the journal by Equinas et al. regarding our article “Combined noninvasive ventilation and mechanical in-exsufflator in the treatment of pediatric acute neuromuscular respiratory failure.” The exciting field of critical care of acute respiratory failure (ARF) in pediatric patients with neuromuscular diseases (NMD) is clearly challenging because of its unique, heterogeneous, and vulnerable features. Thus, we are glad that other centers are interested in these populations. We thank Equinas et al. for their valuable comments, which enabled us to better address some important issues in our article. To datemethodological data regarding combined use of noninvasive ventilation (NIV) and mechanical in-exsufflator (MIE) are limited, especially in the setting of the pediatric intensive care unit (PICU). Even though the present study is the largest cohort to date in neuromuscular patients with ARF in PICU, we agree that its sample size is small compared with most reports in adults, with dispersed age distribution and heterogeneous NMD. However, these features are common in most pediatric studies of NMD, reflecting their relatively low incidence in general populations. We also thank that Equinas et al. discussed about the prevalence of bulbar weakness, which raised an important point. It has been well known that bulbar weakness may lead to the risk of a aspiration of food and saliva, raising the risk of NIV failure, such as in patients of spinal muscular atrophy type 1 (SMA1) or bulbar amyotrophic lateral sclerosis. Therefore, in our study, we have excluded patients with profound bulbar weakness. However, we did enroll patients with SMA1, because all of them had received gastrostomy and Nissen fundoplication to avoid potential respiratory insults caused by reflux, as suggested by a recent guideline for standard care of SMA. We agree that lung function test (LFT) may be an objective tool to assess the responses to interventions in stable patients with respiratory insufficiency. However, we did not perform LFT in the present study due to several reasons. First, LFT is frequently unpractical in children with NMD, as a previous study has demonstrated that even in stable children forced vital capacity could not be obtained in 40% of them. Indeed, a recent guideline of respiratory care for children with NMD established by the British Thoracic Society recommends the measurement of peak cough flow only in children older than 12 years old. In addition, in the setting of PICU, and for infants like those with SMA1, LFT may be difficult or impossible. Thus, in our experience we believe that, unlike the role of LFT in adults or stable older children, clinical parameters such as blood gas analysis, respiratory rate, and heart rate may be more practical to assess the acute changes of respiratory status and the effective clearance of secretions after NIV/MIE interventions in critically ill children with acute pulmonary infections. Hypercapnic respiratory failure is common in patients with NMD as shown in our study. Equinas et al. are also concerned about the hypercapnia in the NIV/MIE failure group in our study. However, since there was also hypercapnia in the successfully treated group and there was no statistically significant difference between them, we believe that it is not a risk factor for intubation in the present study. Sedation is a major issue in methodological considerations of NIV. We understand that most intensivists are reluctant to use sedation and analgesics for patients on NIV due to concern of respiratory drive depression. However, our experiences suggest that mild sedation in infants and younger children may improve patient–ventilator