Manometry results for no CPAP and nCPAP₆ conditions in newborn lambs.

<p>Data are expressed as mean ±SD; P>0.1 for all comparisons. nCPAP₆ =  nasal CPAP+6 cmH₂O; P_GB =  basal intragastric pressure; P_LES =  resting end-expiratory lower esophageal sphincter pressure; P_b =  barrier pressure; P_TD =  transdiaphragmatic pressure; P_es =  resting esophageal pressure. All pressures are referenced to atmospheric pressure.</p><p>Manometry results for no CPAP and nCPAP₆ conditions in newborn lambs.</p

Changes in swallow-induced esophageal peristaltic wave amplitude and duration in newborn lambs.

<p>Data are expressed as mean ±SD; P>0.1 for all comparisons. nCPAP₆ =  nasal CPAP+6 cmH₂O. All pressures are referenced to atmospheric pressure.</p><p>Changes in swallow-induced esophageal peristaltic wave amplitude and duration in newborn lambs.</p

Number of reflux events during the 6 h-period following recording in the sling with either nCPAP₆ application (right) or control condition (left).

<p>The overall greater number in refluxes compared to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0107736#pone-0107736-g001" target="_blank">figure 1</a> is related to the lamb being now allowed to move and feed at will in the Plexiglas chamber. Abbreviations: nCPAP₆ =  nasal CPAP+6 cmH₂O.</p

pH-Impedancemetry results for no CPAP and nCPAP₆ conditions during six hours in newborn lambs.

<p>Data are expressed as mean ±SD<i>;</i> nCPAP₆ =  nasal CPAP+6 cmH₂O; z1 =  impedance channel 1 (proximal esophagus); BEI =  Bolus Exposure Index; NS =  non-significant.</p><p>pH-Impedancemetry results for no CPAP and nCPAP₆ conditions during six hours in newborn lambs.</p

Effects of nasal ventilation on gastroesophageal refluxes.

<p>Fig 2-A represents the total number of GERs, 2-B the bolus exposure index and Fig 2-C the number of proximal GERs. Both liquid- and gas-containing gastroesophageal refluxes are included. Box and whisker plots represent interquartile ranges (upper = Q3, middle line = median, bottom = Q1) with maximum and minimum values, respectively. **: p < 0.05; *: p < 0.1.</p

Inhibitory Effect of Nasal Intermittent Positive Pressure Ventilation on Gastroesophageal Reflux

<div><p>Non-invasive intermittent positive pressure ventilation can lead to esophageal insufflations and in turn to gastric distension. The fact that the latter induces transient relaxation of the lower esophageal sphincter implies that it may increase gastroesophageal refluxes. We previously reported that nasal Pressure Support Ventilation (nPSV), contrary to nasal Neurally-Adjusted Ventilatory Assist (nNAVA), triggers active inspiratory laryngeal closure. This suggests that esophageal insufflations are more frequent in nPSV than in nNAVA. The objectives of the present study were to test the hypotheses that: i) gastroesophageal refluxes are increased during nPSV compared to both control condition and nNAVA; ii) esophageal insufflations occur more frequently during nPSV than nNAVA. Polysomnographic recordings and esophageal multichannel intraluminal impedance pHmetry were performed in nine chronically instrumented newborn lambs to study gastroesophageal refluxes, esophageal insufflations, states of alertness, laryngeal closure and respiration. Recordings were repeated without sedation in control condition, nPSV (15/4 cmH₂O) and nNAVA (~ 15/4 cmH₂O). The number of gastroesophageal refluxes recorded over six hours, expressed as median (interquartile range), decreased during both nPSV (1 (0, 3)) and nNAVA [1 (0, 3)] compared to control condition (5 (3, 10)), (p < 0.05). Meanwhile, the esophageal insufflation index did not differ between nPSV (40 (11, 61) h^-1) and nNAVA (10 (9, 56) h^-1) (p = 0.8). In conclusion, nPSV and nNAVA similarly inhibit gastroesophageal refluxes in healthy newborn lambs at pressures that do not lead to gastric distension. In addition, the occurrence of esophageal insufflations is not significantly different between nPSV and nNAVA. The strong inhibitory effect of nIPPV on gastroesophageal refluxes appears identical to that reported with nasal continuous positive airway pressure.</p></div

Number gas-containing gastroesophageal refluxes with nasal pressure support ventilation and nasal neurally-adjusted ventilatory assist.

<p>Despite the presence of esophageal insufflations during nasal pressure support ventilation (nPSV) and nasal neurally adjusted ventilatory assist (nNAVA), but not during the control condition, no significant increase in gas-containing gastroesophageal refluxes was observed in nPSV or nNAVA compared to the control condition.</p

Liquid gastroesophageal reflux during (A) nasal pressure support ventilation (B) nasal neurally-adjusted ventilatory assist.

<p>From top to bottom: EEG, electroencephalogram; EOG, electrooculogram; ECG, electrocardiogram; EAdi, electrical activity of the diaphragm; EAta, thyroarytenoid muscle (laryngeal constrictor) electrical activity; ∫EAta, moving time averaged EAta; P_mask, mask pressure; SpO₂, pulse oximetry; V_lung, lung volume variations = sum signal of respiratory inductance plethysmography; Z1 to Z6, impedance channels of the esophageal multichannel intraluminal impedance-pHmetry (MII-pH). The decrease in esophageal impedance progressing from Z6 up to Z1 (the most proximal channel of the MII-pH) illustrates a proximal gastroesophageal reflux.</p

Esophageal insufflations during nasal pressure support ventilation in quiet and active sleep.

<p>Two successive periods of quiet and active sleep in the same lamb are represented. The most frequent pattern of esophageal insufflation and EAta recording is illustrated. In active sleep (AS), all five successive ventilator insufflations (see mask pressure) were accompanied by an increase in esophageal impedance progressing from the oral (Z1) down to caudal (Z6) channels of the MII-pH, depicting the insufflation of gas into the esophagus (= esophageal insufflations); in this example, esophageal insufflations were present in AS only. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0146742#pone.0146742.g001" target="_blank">Fig 1</a> for abbreviations.</p