Bolus Transport Research Articles

Tongue Strength and Swallowing Dysfunction in Head and Neck Cancer Patients after Radiation Therapy

High dose radiotherapy (RT) and chemotherapy have been utilized as primary treatment for tumors of the oral cavity and oropharyngeal to preserve organ function. RT to the oral cavity and oropharynx can cause changes in swallowing resulting in reduced ability to propel foods and liquids through the oral cavity and pharynx. Oral phase impairment can include reduced bolus formation, impaired bolus transport through the oral cavity, prolonged oral transit times, and increased oral residue percentages.

Multiple Intraluminal Impedance Measurement and Manometry in the Jejunum of Healthy Subjects: A New Tool for Diagnosis of Small Bowel Motility

Background: The relationships between contractile activity and transport of intraluminal contents in the human small intestine are not well understood. Aim: To study both phenomena by combined measurements of intraluminal impedance and pressurein the jejunum of healthy subjects. Methods: 12 healthy volunteers (m 4, f 8), mean age 32.3 years (24–49 years), underwent jejunal combined impedance/manometry recordings (six channels at 2-cm intervals). Fasting (one MMC cycle) and postprandial motility were recorded. Results: Intestinal transport differed with the phases of motility. No transport was seen in phase I, regular bolus transport occurred during phase III. The longest duration of transport was observed in late phase II preceding phase III. Irregular and intermittent bolus transport occurred during early phase II and in the postprandial period. Three types of relationship between contractions and bolus transport were identified: transport with single contractions or migrating clustered contractions and transport without contractile activity. The frequency of these events differed with the direction of bolus transport, and a relationship between propagation velocity and bolus presence time was established. Conclusion: Combined simultaneous measurement of intraluminal impedance and manometry is a promising new method to elucidate the relationships between bolus transport and contractile activity in the human small bowel.

The preterm piglet – a model in the study of oesophageal development in preterm neonates

Preterm infants have difficulty in attaining independent oral feeding. This can ensue from inadequate sucking, swallowing and/or respiration. In impeding bolus transport, immature oesophageal motility may also be a cause. As studies on the development of oesophageal motility are invasive in preterm infants, the preterm piglet was investigated as a potential research model. Oesophageal motility (EM) of term (n = 6) and preterm (n = 15) piglets were monitored by manometry for 10 min immediately following bottle feeding on days 1-2 and 3-4 of life. Piglets' oral feeding performance and EM were similar to those of their human counterparts. Term piglets readily completed their feeding, whereas their preterm counterparts did not. They also presented with greater peristaltic activity and propagating velocity. Peristaltic activity remained unchanged over time in preterm piglets, but an increase in synchronous and decrease in incomplete motor activity were noted. Preterm piglets that developed symptoms analogous to necrotizing enterocolitis (NEC) demonstrated uncharacteristic oesophageal activity. Immature EM may cause oral feeding difficulties. NEC-like symptoms may adversely affect EM. The piglet is a valid research model for studying human infant oral feeding and oesophageal development.

Neural Mechanisms of Swallowing and Effects of Taste and Other Stimuli on Swallow Initiation

Swallowing involves several motor processes such as bolus formation and intraoral transport of a food bolus (oral stage) and a series of visceral events that occur in a relatively fixed timed sequence but are to some degree modifiable (pharyngeal stage or swallow reflex). Reflecting the progressive aging of society, patients with swallowing disorders (i.e., dysphagia) are increasing. Therefore, there is expanding social demand for the development of better rehabilitation treatment of dysphagic patients. To date, many dysphagia diets have been developed and are available commercially to help bring back the pleasure of mealtimes to dysphagia patients. Texture modification of food to make the food bolus easier to swallow with less risk of aspiration is one of the important elements in dysphagia diets from the viewpoint of safety assurance. However, for the further development of dysphagia diets, new attempts based on new concepts are needed. One of the possible approaches is to develop dysphagia diets that facilitate swallow initiation. For this approach, an understanding of the mechanisms of swallow initiation and identification of factors that facilitate or suppress swallow initiation are important. In this review, we first summarize the neural mechanisms of swallowing and effects of taste and other inputs on swallow initiation based on data mainly obtained from experimental animals. Then we introduce a recently established technique for eliciting swallowing using electrical stimulation in humans and our ongoing studies using this technique.

Endoscopy vs. Standard Manometry vs. High Resolution Esophageal Pressure Topography (HREPT) for Detection of Hiatal Hernia

Purpose: Gastroenterologists routinely diagnose hiatal hernia with an upper endoscopy (EGD). However, the diagnostic yield of endoscopy for the detection of hiatal hernia when compared to manometry has been scarcely assessed. HREPT provides information on esophageal manometry, topography and bolus transport in the supine and upright positions. Hypothesis: HREPT is more accurate than EGD for the detection of hiatal hernia. Aim: To examine the diagnostic yield of EGD, supine esophageal manometry and HREPT in the standing upright position for the detection of hiatal hernia and to examine changes in esophageal function. Methods: 50 patients (m/f=24/26; mean age 49 yr) with GERD and/or dysphagia underwent both EGD and HREPT. Endoscopist reported the presence and length of hiatal hernia. HREPT was performed by placing a 36 sensor (Sierra Scientific) probe, 1 cm apart from the pharynx to stomach, and the manometric/ topographic changes were examined in supine (standard) and upright positions. A hiatal hernia was identified on HREPT as two separate bands of HPZ, at least 1cm apart. Also LES pressure, length and HPZ length were assessed. Results: (Table, mean+SEM Bold=p<0.05): EGD detected significantly fewer (p=0.0001) subjects with hiatal hernia when compared to HREPT, but its yield was similar to standard supine manometry (see Table). HREPT in the standing position detected twice as many subjects (p=0.0001) with a hiatal hernia when compared to standard supine manometry (see Table). The length of hiatal hernia was significantly longer (p=0.0001) with HREPT in the standing position when compared to EGD. LES pressure was higher (p=0.0001), mean length was longer (p=0.0003), and length of HPZ was longer (p=0.0001) in upright than supine position.TableConclusion: HREPT when performed in the standing position is superior to endoscopy or supine manometry for the detection of hiatal hernia, and should be the preferred approach for identifying hiatal hernia in subjects with GERD. Esophageal function and manometric parameters are significantly affected by body position.

Struck Dysphagic

Struck Dysphagic

Brain Stem Control of the Phases of Swallowing

The phases of swallowing are controlled by central pattern-generating circuitry of the brain stem and peripheral reflexes. The oral, pharyngeal, and esophageal phases of swallowing are independent of each other. Although central pattern generators of the brain stem control the timing of these phases, the peripheral manifestation of these phases depends on sensory feedback through reflexes of the pharynx and esophagus. The dependence of the esophageal phase of swallowing on peripheral feedback explains its absence during failed swallows. Reflexes that initiate the pharyngeal phase of swallowing also inhibit the esophageal phase which ensures the appropriate timing of its occurrence to provide efficient bolus transport and which prevents the occurrence of multiple esophageal peristaltic events. These inhibitory reflexes are probably partly responsible for deglutitive inhibition. Three separate sets of brain stem nuclei mediate the oral, pharyngeal, and esophageal phases of swallowing. The trigeminal nucleus and reticular formation probably contain the oral phase pattern-generating neural circuitry. The nucleus tractus solitarius (NTS) probably contains the second-order sensory neurons as well as the pattern-generating circuitry of both the pharyngeal and esophageal phases of swallowing, whereas the nucleus ambiguus and dorsal motor nucleus contain the motor neurons of the pharyngeal and esophageal phases of swallowing. The ventromedial nucleus of the NTS may govern the coupling of the pharyngeal phase to the esophageal phase of swallowing.

Esophageal Clearance Patterns in Normal Older Adults as Documented with Videofluoroscopic Esophagram

Normal esophageal bolus transport in asymptomatic healthy older adults has not been well defined, potentially leading to ambiguity in differentiating esophageal swallowing patterns of dysphagic and healthy individuals. This pilot study of 24 young (45–64 years) and old (65+years) men and women was designed to assess radiographic esophageal bolus movement patterns in healthy adults using videofluoroscopic recording. Healthy, asymptomatic adults underwent videofluoroscopic esophagram to evaluate for the presence of ineffective esophageal clearance, namely, intraesophageal stasis and intraesophageal reflux. Intraesophageal stasis and intraesophageal reflux were visualized radiographically in these normal subjects. Intraesophageal stasis occurred significantly more frequently with semisolid (96%) compared with liquid (16%) barium, suggesting that a variety of barium consistencies, as opposed to only the traditional fluids, would better define the spectrum of esophageal transport. Intraesophageal reflux was observed more frequently in older males than in their younger counterparts. The rates of intraesophageal stasis and intraesophageal reflux were potentially high given that successive bolus presentations were spaced 10 seconds apart. These findings suggest a need for a more comprehensive definition regarding the range of normal esophageal bolus transport to (a) prevent misdiagnosis of dysphagia and (b) to enhance generalization to functional eating, which involves solid foods in addition to liquids.

Identification of impaired oesophageal bolus transit and clearance by secondary peristalsis in patients with non‐obstructive dysphagia

Impaired secondary peristalsis has been shown in non-obstructive dysphagia (NOD). The relationship between such changes and alterations in bolus transport has not been studied. The aim of this study was to evaluate the integrity and characteristics of oesophageal bolus transit by secondary peristalsis in NOD patients with multichannel intraluminal impedance (MII). Eleven healthy volunteers and 10 consecutive patients underwent combined MII recording and manometry. Secondary peristalsis was stimulated by mid-oesophageal injections of saline. Values for bolus presence time at each of the recording sites and bolus transit time were calculated. Bolus transit was considered to be complete when impedance defined complete bolus clearance at all recording sites. Secondary peristaltic responses were triggered significantly less frequently in patients with NOD than in controls (P < 0.001). The proportion of secondary peristalsis demonstrating complete bolus transit was lower in NOD patients than in controls (P < 0.001). Oesophageal bolus transit time by secondary peristalsis was longer in NOD patients than in controls (P = 0.005), as was bolus presence time at each of the recording sites (P < 0.05). When compared with controls, NOD patients demonstrated a higher proportion of incomplete bolus transit in response to normal secondary peristalsis (P < 0.001). Abnormal bolus transit occurred more often associated with ineffective and synchronous responses than normal responses in both groups studied (P < 0.001). Multichannel intraluminal impedance identifies functional defects of oesophageal bolus clearance by secondary peristalsis in NOD patients and such defects are characterized by a longer oesophageal dwell and a prolonged clearance time.

Physiology of the oesophageal transition zone in the presence of chronic bolus retention: studies using concurrent high resolution manometry and digital fluoroscopy

Distinct contraction waves (CWs) exist above and below the transition zone (TZ) between the striated and smooth muscle oesophagus. We hypothesize that bolus transport is impaired in patients with abnormal spatio-temporal coordination and/or contractile pressure in the TZ. Concurrent high resolution manometry and digital fluoroscopy were performed in healthy subjects and patients with reflux oesophagitis; a condition associated with ineffective oesophageal contractility and clearance. A detailed analysis of space-time variations in bolus movement, intra-bolus and intra-luminal pressure was performed on 17 normal studies and nine studies in oesophagitis patients with impaired bolus transit using an interactive computer based system. Compared with normal controls, oesophagitis patients had greater spatial separation between the upper and lower CW tails [median 5.2 cm (range 4.4-5.6) vs 3.1 cm (2.2-3.7)], the average relative pressure within the TZ region (TZ strength) was lower [30.8 mmHg (28.3-36.5) vs 45.8 mmHg (36.1-55.7), P < 0.001], and the risk of bolus retention was higher (90%vs 12%; P < 0.01). The presence of bolus retention was associated with a wider spatial separation of the upper and lower CWs (>3 cm, the upper limit of normal; P < 0.002), independent of the presence of oesophagitis. We conclude that bolus retention in the TZ is associated with excessively wide spatial separation between the upper and lower CWs and lower TZ muscle squeeze. These findings provide a physio-mechanical basis for the occurrence of bolus retention at the level of the aortic arch, and may underlie impaired clearance with reflux oesophagitis.

W1803 High Resolution Manometry with Large Volume Multiple Repeated Swallows AIDS the Detection of Oesophageal Pathology

Conventional manometry does not provide a diagnosis in many patients referred with esophageal symptoms because, in part, it fails to predict effective bolus transport.[1,2] High resolution manometry (HRM) measures contractile activity and the intra-bolus pressure (IBP) gradient that drives fluidmovement.[3] In the pharynx, the position of maximum IBP gradient following 10-20ml swallows identifies pathology causing clinically significant resistance to flow.[4] A similar approach with larger volumes has not been tested in the relatively wide lumen of the esophagus. AIMS & METHODS: To assess whether HRM during multiple repeated swallows of water (MRS) can help identify esophageal pathology and quantify functional and structural resistance to flow in the esophageal body and lower esophageal sphincter (LES). A prospective study of 160 consecutive patients undergoing investigation of esophageal symptoms was performed. HRM for ten water (10ml) and five bread swallows were obtained in the upright position. Peristaltic pressure, baseline and nadir LES pressure, IBP, and IBP gradient were recorded. Patients then drank 200ml water by MRS. Symptom events were recorded. RESULTS: 125 studies provided complete data for analysis (78%). Failed swallows (p 20mmHg (p<0.01 vs. lower values). CONCLUSION: HRM with 200ml MRS is a simple, physiological test that helps to localize and quantify the severity of esophageal pathology by increasing IBP above and IBP gradient across the lesion compared to 10ml water swallows. Functional and structural disease were identified by this technique. In addition, raised IBP during MRS was associated with the occurrance of typical, clinically relevant symptoms. REFERENCE(S): 1.Fox NGM 04, 2.Tutuian AJG 04, 3.Pandolfino AJP 06., 4.Pal AJP 03

Clinical correlates of dysphagia to oesophageal dysmotility: studies using combined manometry and impedance

This study aimed to elucidate the mechanism of dysphagia by determining the simultaneous relationships between subjective perception of swallow with oesophageal motility and bolus transport in patients with non-obstructive dysphagia (NOD). Combined oesophageal manometry and impedance was performed in 18 consecutive NOD patients and 14 healthy controls. Swallow was abnormal if the amplitude of distal oesophageal contractions was less than 30 mmHg or simultaneous contractions occurred. Bolus transit was abnormal if bolus exit was not found at one or more of the measuring sites. Perception of each swallow was assessed using a standardized scoring system and was enhanced if score was >1. The prevalence of complete bolus transit was lower in NOD patients compared with healthy controls (P = 0.001). Abnormal liquid bolus transit was found in 40% of patients with normal motility and 38% of patients with abnormal motility, whereas abnormal viscous bolus transit was observed in 38% of patients with normal motility and 70% of patients with abnormal motility. Agreement between enhanced perception and impedance was poor during liquid (kappa = 0.12, 95% CI: -0.003 to 0.233) and viscous swallowing (kappa = 0.12, 95% CI: -0.004 to 0.244). Agreement between enhanced perception and manometry was even poorer during liquid (kappa = -0.16, 95% CI: -0.302 to 0.022) and viscous swallowing (kappa = -0.12, 95% CI: -0.25 to 0.002). NOD patients show poor correlation between dysphagia and oesophageal motility parameters. The results suggest that, in patients with NOD, oesophageal motor dysfunction may play a limited role, if any, in the generation of dysphagia.

Combined multichannel intraluminal impedance and manometry testing

Oesophageal manometry has been considered the "gold standard" test for the evaluation of oesophageal motility. Oesophageal manometry allows physicians to assess peristalsis by using informations about the shape, amplitude and duration of the oesophageal contraction, but it does not offer direct information about bolus transit through the oesophagus. Recent studies demonstrate that combined impedance-manometry provides important additional information about oesophageal motility as compared to conventional manometry such as: (1) monitoring of bolus transport patterns without the use of radiation, (2) calculation of bolus transit parameters, (3) evaluation of bolus clearance and (4) investigation of the relationships between bolus transit and LES relaxation. These changes could potentially improve diagnostic accuracy of oesophageal motility testing, advancing both clinical and basic research. This review focuses on current aspects of the novel technology of combined impedance-manometry for oesophageal motility testing.

Application of Tongue Pressure Measurement to Rehabilitation of Dysphagic Patients with Prosthesis

Tongue plays an important role by making contact with palate in swallowing. This study was aimed for investigating the utility of originally developed measuring system of tongue pressure in the rehabilitation of dysphagic patients with prosthesis. Subject was a 68 years old male post-surgical laryngeal cancer patient who underwent percutaneus endoscopic gastrostomy because of dysphagia. Tongue pressure during dry swallow was recorded by using our original sensor sheet system (Nitta, Japan) with five measuring points (Chs.1-5) attached on the palatal surface of maxillary denture (RPD). Tongue impression was taken by his maxillary denture and the palatal contour was changed into palatal augmentation prosthesis (PAP), then tongue pressure with PAP was recorded and compared with that with RPD. Magnitude of tongue pressure on median line (CHs.1-3) of palatal surface of RPD was nearly 0 and that on the circumferential part (Chs.4 and 5) had laterality. In PAP, however, magnitude of tongue pressure on the median line increased and showed normal pattern (Ch.1>Ch.2>Ch.3) and that on the circumferential part showed no laterality. Improvement of the tongue pressure production described by our system might contribute to the bolus transport in oral phase of swallowing.

Challenging the Limits of Esophageal Manometry

After steady improvement until about 1980, the technology behind esophageal manometry saw little change until recent years. A variety of sensor technologies existed including solid-state strain gauge transducers, circumferentially sensitive transducers, multilumen perfused catheters with external pressure transducers, and the Dentsleeve device. However, irrespective of transducer design, the basic format of manometric studies was of multiple line-tracings representing pressure change versus time at several discrete esophageal loci. Furthermore, of the sensor designs available, only the Dentsleeve device provided a validated method for assessing sphincter relaxation. However, the Dentsleeve accomplished this at the expense of pressure response rate and spatial resolution leading some experts to focus instead on these limitations. In brief, little standardization existed in methodology among centers and there was no agreement regarding optimal assembly design or study interpretation.

Swallowing difficulties in Duchenne muscular dystrophy: Indications for feeding assessment and outcome of videofluroscopic swallow studies

Feeding difficulties are known to occur with advancing age in Duchenne muscular dystrophy (DMD). We evaluated the role of videofluoroscopy swallow study (VFSS) in a group of 30 DMD patients with feeding difficulties. Indications for feeding assessment were: respiratory infections potentially attributable to aspiration ( n=10) and/or episodes of choking ( n=24) subdivided into isolated choking events ( n=8) and regular choking during swallowing ( n=16). Indications for assessment were analysed in relation to the VFSS results. Median age at assessment was 17.13 years (range 6–31.4). Twenty-four VFSS were performed. Prolonged chewing and effortful bolus transport for solids increased with age. Swallow trigger was normal in the majority of cases. All patients had some post-swallow pharyngeal residue around the laryngeal inlet increasing in volume with age. Although this residue did not result in aspiration, it was worse in patients that were frequently choking. Three patients intermittently had penetration of the supraglottic space that did not reach the vocal folds during the swallow. Our results suggest that reported swallowing problems when assessed are not always associated with difficulties on VFSS. It is the oral phase of swallowing that is most significantly affected in DMD. The pharyngeal phase is well triggered but is weak with incomplete pharyngeal clearance leaving pharyngeal residue. Insufficient or effortful chewing coupled with weak clearance may predispose them to choking episodes either as a one off event or with increasing frequency with age. This study suggests that VFSS may not be of additional benefit to careful feeding history and observation in DMD with feeding difficulties.

Functional and Radiological Evaluation of Free Jejunal Transplant Reconstructions After Radical Resection of Hypopharyngeal or Proximal Esophageal Cancer

Cancer of the pharyngoesophageal junction (PEJ) is associated with late onset of symptoms, high morbidity, and a dismal prognosis. Radical surgery with pharyngolaryngectomy and reconstruction with a free vascularized jejunal transplant has been increasingly practiced in the treatment of these patients. This strategy is not devoid of challenges, and the present study is aimed at evaluating the long-term functional outcome among patients who have undergone such surgical treatment. Ten patients (mean age 59 years) with a mean follow-up time of 54 months were included. Clinical assessment, health-related quality of life (HRQL) questionnaires, and a standardized radiography examination were used for evaluation. The Karnofsky index ranged from 60 to 90 (mean 82). Global QL scores (EORTC QLQ-C30) had a mean value of 74, and the mean scores for dysphagia-related items of the EORTC QLQ OES-18 questionnaire were within the lower range. Radiographic signs of disturbed bolus transport through the jejunal transplant were found in all patients examined despite the grading of dysphagia from 0 to 1. The Watson dysphagia score varied between 0.5 and 45.0 (mean 16.2). No correlations were found between radiographic findings and the clinical evaluations or the outcomes assessed by the HRQL questionnaires. HRQL was found to be generally good after cancer of the PEJ and jejunal transplant insertion. Most patients reported mild dysphagia. Radiologic signs of disturbed bolus passage were common, but their clinical impact seemed questionable.

Non-achalasic motor disorders of the oesophagus

Motor abnormalities of the oesophagus are characterised by a chronic impairment of the neuromuscular structures that co-ordinate oesophageal function. The best-defined entity is achalasia, which is discussed in a separate chapter. Other motor disorders with clinical relevance include diffuse oesophageal spasm, oesophageal dysmotility associated with scleroderma, and ineffective oesophageal motility. These non-achalasic motor disorders have variable prevalence but they could be associated with invalidating symptoms such as dysphagia, chest pain and gastro-oesophageal reflux disease. New oesophageal diagnostic techniques, including high-resolution manometry, high-frequency intraluminal ultrasound and intraluminal impedance, allow (1) better definition of peristalsis and sphincter function, (2) assessment of changes in oesophageal wall thickness, and (3) evaluation of pressure gradients within the oesophagus and across the sphincters that can produce normal or abnormal patterns of bolus transport. This chapter discusses recent advances in physiology, pathophysiology, diagnosis and treatment of non-achalasic oesophageal motor disorders.

Chewing and Food Consistency: Effects on Bolus Transport and Swallow Initiation

Preswallow bolus formation usually occurs in the mouth for liquids and in the oropharynx for solid foods. We examined the effect of chewing on the relationship between bolus transport and swallow initiation. Fifteen healthy subjects were imaged with lateral projection videofluorography while eating liquids, solid foods, and a mixture of liquid and solid foods in upright and facedown postures. Videotapes were reviewed to measure the location of the leading edge of the barium at swallow initiation. Chewing and initial consistency each altered the relationship between food transport and swallow initiation. In particular, when chewing liquid (or consuming foods with both liquid and solid phases), a portion of the food commonly reached the hypopharynx well before swallow onset. This transport to the hypopharynx was highly dependent on gravity, but transport to the valleculae for chewed solid food was active, depending primarily on tongue-palate contact. Chewing appeared to reduce the effectiveness of the posterior tongue-palate seal, allowing oral contents to spill into the pharynx. Consuming two-phase foods with both solid and liquid phases may increase the risk of aspiration in dysphagic individuals with impaired airway protective reflexes.

Multichannel intraluminal impedance to detect relationship between gastroesophageal reflux and apnoea of prematurity

Background The association between gastroesophageal reflux and apnoea of prematurity is still controversial. Available data are biased by the heterogeneity of the infants enrolled as regard to some confounding factors and by the use of the traditional pH monitoring that is unable to detect non acid reflux events which might be prevalent in infants receiving frequent milk feeding. Multichannel intraluminal impedance has been recently introduced as a pH-independent method to investigate the bolus transport in hollow organs. Objective To assess if combined multichannel intraluminal impedance-pH study could be useful to detect an association between gastroesophageal reflux and apnoea of prematurity. Methods We prospectively evaluated a group of premature infants with apnoea of prematurity in absence of any confounding factors (ventilatory support, treatment with caffeine, permanent nasogastric tube, post-natal age older than 30 days) by simultaneous recording of 24-h multichannel intraluminal impedance-pH and cardiorespiratory monitoring. A temporal relationship between an apnoea and a reflux event was considered if both commenced within 20 s of each other. Results Six premature infants [three male; median gestational age 31 weeks (range 27–36); birth weight 1335 g (range 1200–2350); age at study 17 days (range 7–28)] were studied. A total of 405 reflux events [306 (76%) weakly acid and 99 acid reflux] and 142 apnoeas were detected. The frequency of apnoeas occurring during the reflux events period was significantly greater than the one calculated for reflux-free period [0.42/min (0.00–1.28) versus 0.016/min (0.003–0.028); p < 0.05]. The sub-analysis based on chemical composition and duration of refluxate showed that the frequency of apnoeas associated with weakly acid reflux events was significantly greater than the one calculated for reflux-free period [0.416/min (0.00–1.30) versus 0.016/min (0.003–0.028), respectively; p < 0.05] and that the frequency of apnoeas occurring during reflux events longer than 30 s was significantly higher than those occurring during shorter reflux events (22% versus 11%; p < 0.004). Conclusion Our data show that weakly acidic reflux events are more prevalent than acid reflux events in premature infants, confirming the need for the use of multichannel intraluminal impedance-pH monitoring for diagnosis of gastroesophageal reflux in those patients. Gastroesophageal reflux and apnoea of prematurity are both common occurrences and, in our experience, may be temporally related especially as regard to weakly acid refluxate and reflux events longer than 30 s.