Michele Ghezzi, Michela Silvestri, Girolamo Mattioli, Giovanni A. Rossi. Dear Editor, in their article, L. Corvaglia[1] et al. simultaneous recorded polysomnography and pH-impedance monitoring (pH-MII) in very preterm infants and showed that apnoeas can be triggered by GER. They detected during 151 h pH-MII registration 1,065 GER episodes [502(47.1%) acid and 563(52.9%) non-acid] and found that the frequency of apnoeas occurring after the onset of GER was higher compared with the frequency in the GER-free period or before the onset of GER. The authors did not analyze whether apnoeas were more frequently triggered by acid or by non- acid GER. We recently evaluated by pH-MII children with GER and respiratory symptoms and, similarly to what described in very preterm infants by L Corvaglia[1] et al., we found an elevated percentage of non- acid GER (>30%) in a high proportion of infants (70.2%). Interestingly, in the “non-acid GER population” apnoea and arterial oxygen desaturation episodes were more often detected in the 0-1 yr group, as compared to the 1-2 yr group (table 1). In humans, infusion of fluids into the larynx causes apnoea episodes, laryngeal closure, cough and swallowing, mediated by the laryngeal chemoreflexes (LCR) through stimulation of the superior laryngeal nerve.[2] LCR are also specifically induced by contact of acids and/or non-acid low-chloride-content solutions (such as gastric fluid and saliva) with the epithelium surrounding the laryngeal airway entrance.[3] Studies in animals indicate that with maturation, apnoea and swallowing components of the LCR decrease while cough becomes prominent.[3] The observation here reported which confirms that also non-acid GER can induce apnoeas and other respiratory disorders in children[4] may be even more relevant in newborns and young infants, whose gastric acidity is often buffered by milk meals, and may explain the failure of acid suppression treatments in these patient populations.[5]

References

1. Corvaglia L, Zama D, Gualdi S, et al. Gastro-oesophageal reflux increases the number of apnoeas in very preterm infants. Arch. Dis. Child. Fetal Neonatal Ed. 2009;94:188-92.

2. Pickens DL, Schefft GL, Thach BT. Prolonged apnea associated with upper airway protective reflexes in apnea of prematurity. Am Rev Respir Dis 1988;137:113–8.

3. Thach BT. Maturation and transformation of reflexes that protect the laryngeal airway from liquid aspiration from fetal to adult life. Am J Med 2001;111:69s–77s.

4. Mattioli G, Pini-Prato A, Gentilino V, et al. Esophageal impedance/pH monitoring in pediatric patients: preliminary experience with 50 cases. Dig Dis Sci. 2006;51:2341-7.

5. Salvatore S, Hauser B, Salvatoni A, et al. Oral ranitidine and duration of gastric pH >4.0 in infants with persisting reflux symptoms. Acta Paediatr 2006;95:176-81.

The authors have no conflict of interest to declare

In this study it was reported that, the "frequency of apnoea in the 30 seconds after GER (GER-triggered apnoeas) was greater than that detected in the 30 seconds before (p = 0.01). ..A strong correlation between total number of apnoeas and the difference between apnoeas detected 30 seconds after and before GER was found (p = 0.034)"(1).

These data are consistent with both apnoea and GER being caused by an enrgy deficit. The presence of an energy deficit in adults, identified from the presence of a gastric intramucosal acidosis, is predictive of weaning failure (2).

1. L Corvaglia, D Zama, S Gualdi, M Ferlini, A Aceti, and G Faldella Gastro-oesophageal reflux increases the number of apnoeas in very preterm infants Arch. Dis. Child. Fetal Neonatal Ed. 2009; 94: F188-F192

2. Mohsenifar; Angela Hay; Jeffrey Hay; Michael I. Lewis; and Spencer K. Koerner. Gastric Intramural pH as a Predictor of Success or Failure in Weaning Patients from Mechanical Ventilation Annals of Internal Medicine. Gastric Intramural pH as a Predictor of Success or Failure in Weaning Patients from Mechanical Ventilation