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PLEASE NOTE: The chapter "Findings" in this article will be accessible after acceptance process of the doctoral thesis is concluded - or after publication!
DIESE WEB-VERSION ENTHÄLT KEINE ABBILDUNGEN! DEMNÄCHST VERFÜGBAR!
* Dept. of Neonatology and Pediatric Intensive Care, Ulm University Children´s Hospital, Ulm, Germany
** Dept. of Medical Statistics and Documentation, Ulm University, Ulm, Germany
Background: The purpose of this study was to examine whether feeding difficulties in VLBW infants could be reduced by consistent swallowing through drip and nipple feedings contrary to gavage feedings. The Pilot Study aimed for measurements of drinking quantities in the different groups; a re-examination will investigate effects on feeding behaviour. Methods: 20 VLBW infants < 29 weeks of gestation and 750 – 1250 g birth weight were randomized into an intervention- (‚drip’-) and a control- (‚gavage‘-) group. After exclusive gavage feedings the application started at 2 p.m. at an infant´s age of 5 days ± 12 hours and ended on day 28 after birth. Exceeded the dropped volume 3 ml per kg and meal, an instant change to nipple feeding followed – underpassed the sucked volume this limit on the average over the last 24hours registration sheet, a swift back to drip feeding occurred. Two types of nipple units were used: until day 13 after birth a Nuk-type nipple unit (Mapa), from day 14 till 28 a standard nipple unit (Milupa). On days 14, 21 and 28 the drinking volumes taken by standard nipple in 5 minutes were registered. Findings: The median drinking quantities in ml (min.-max.) in 5 minutes per meal, kg and infant were registered for the intervention- / control group as follows: day 14 2,1 (0,7-3,9) / 2,6 (0,6-4,7), day 21 2,5 (1,1-4,6) / 3,5 (0,5-5,2), day 28 3,75 (2,8-6,6) / 3,5 (1,8-5,7).
Conclusion: The pilot study could not demonstrate that more drinking instead of gavage feeding during the first four weeks of life results in a greater drinking quantity taken by standard nipple. (p=0,42 on day 28). The re-examination will analyse whether VLBW infants of the intervention group show less feeding difficulties than control group infants.
Keywords: drip, dropper feeding, sucking, swallowing, nasogastric tube, volume, VLBW infants
Since decades the use of nasogastric tubes in feeding of VLBW infants unable to suck at breast or bottle is widespread [76 Pereira et al. 1986, 77 Whitfield 1982]. Re-examining preterm infants ≤ 1000g birth weight in an age between 2 5/12 and 5 7/12, Wittek et al. recognised problems in swallowing and drinking in 25,5% of the infants [EK2 Wittek et al. 1998]. Feeding difficulties make up a remarkable portion of the problems of otherwise healthy preterm infants [78 Bu´Lock, 92 Selley et al. 1990]. As Hawdon et al. report, almost 50% of the parents describe difficulties in feeding their infants at an age of 12 months – even in infants known as good feeders during the lenght of stay in hospital [2 Hawdon]. For preterm infants having been fed by nasogastric tube for the first two years oral food intake represents an ensemble of various difficulties: oral dyscoodination, unfamiliar nutrition, oral hypersensitivity and a lack of confidence in own oral mechanisms to cope with the food [64 Kamen 1990, 37 Fernandez et al. 1988].
The fetus is able to swallow fluid in utero without considerable effort for sucking as the positive pressure difference makes the fluid pour into its mouth when being opened [148 DeVries et al. 1982, 60 Medoff-Cooper et al. 1995, 61 Conway 1994]. Therefore a study seems reasonable investigating the impact of an alternative feeding method on appearence of feeding difficulties. VLBW infants receive drip feeding and are allowed to swallow actively. Cautious dropping shall prevent choking and coughing. Thus conditions in utero are simulated.
Only few publications deal with alternative feeding methods:
William A. Silverman desribes drip feeding as one feeding method already used in the very beginnings of neonatology in the 1880s [75 Silverman 1979, 73 Herbst]. Malhotra et al. compared feeding by bottle with cup and a traditional Indian feeding device, the ‘paladai’. The paladai is a sort of bowl with a long-streched nose containing a volume of 30 ml. Compared to the other methods using the paladai resulted in the largest volume intake with the infants being quiet the longest [1 Malhotra]. Fernandez et al., an author also from India, describes the possibility of ‘dropper feeds’ with a device similar or identical to Malhotras paladai [37 Fernandez et al.].
Aim of this study was examine whether infants fed primarily by drip and nipple (= intervention group) show a greater quantity of milk intake on specific days than those mostly being fed by nasogastric tube (control group). A re-examination will reveal whether intervention group members demonstrate less feeding difficulties than control group infants.
All infants < 29 weeks of gestation and 750 – 1250 g birth weight with parental approval were included into the study. Atresia or perforation within the gut system led to the exclusion of the infant. Intraventricular hemorrhage degree 3 or 4 and necrotising enterocolitis and transfer of an infant resulted in discontinuance of the study.
The feeding methods started when the infant was at an age of 5 days ± 12 hours, on day 5 or 6 after birth. Up to this point all infants received nutrition entirely through nasogastric tube to prevent aspiration. Receiving 12 meals daily feeding methods on day 5 or 6 began at 2 p.m., at 8 meals daily at 3 p.m.. On the day of beginning infants were given glucose 5% until 0 a.m. in order to minimize the risk of aspiration. The study period ended on day 28 after birth - at 9 p.m. for infants receiving 8 meals per day, at 10 p.m. for infants with 12 daily. Days 14, 21 and 28 after birth served to compare drinking quantities between the infants of both groups.
The amount meals given by drip or nipple followed a given feeding rhythmicity: at 12 meals per day by a 2-hours alteration between drip/nipple and tube feeding whereas 8 daily meals required feeding by drip/nipple or tube at each meal (all three hours). For nipple feedings a new nipple had to be used for each single meal. Banked human milk or formula (Beba-FG, Nestlé) served as main diet. Substitution of protein was allowed at a maximum of 3 g FM 85 (Nestlé) per 100 ml milk or formula (Beba-FG, Nestlé). Infants also received calcium-glycerophosphat or calcium-gluconat when indicated. No additions to milk or formula were allowed on comparison days 14, 21 and 28 after birth. For each meal application of sedatives was controlled. Minimum feeding time by drip or nipple was 5 minutes, standardized by timers. Ordered food volume per meal was increased by 20 ml per kg and day.
These infants were fed according to the feeding rhythm. As soon as intaken volume by drip feeding reached or exceeded 3 ml per kg and meal (‘3 ml-limit’) an instant change to feeding by nipple took place. Dropped the volume intake by nipple under the 3 ml-limit in average over the last 24hours documentation sheet feeding continued by drip. A chart showing the 3 ml-limit in dependence on weight was printed in each documentation book and hung out in each ward. The following nipple units had to be used: until day 13 after birth (incl.) the Nuk-type nipple for preterm infants of “Mapa”, from day 14 till 28 the blue standard-type nipple for preterm infants of Milupa. In case of a difference between drank and ordered volume, this quantity given by continuously lying nasogastric tube.
After beginning of the study on day 5 or 6 infants of the control group were fed by nasogastric tube. Once daily (2 or 3 p.m.) willingness to drink by nipple was tested by non-nutritive sucking. Being positive nipple feeding was allowed also in this group (no drip feeding) with the following nipple units: until day 13 after birth (incl.) the Nuk-type nipple for preterm infants of Mapa, from day 14 until day 28 the blue nipple for preterm infants of Milupa. On days 14, 21 and 28 after birth, the days drinking quantities of both groups were compared, the infants of the control group followed the feeding rhythmicity of the intervention group. Infants received the differences between actively and ordered volume over continuously lying nasogastric tube.
In case the minimum feeding time of five minutes could not be reached the reasons had to be noted on the “Documentation sheet for complications for drip and nipple feeding”. Each meal on the documentation sheets for the intervention or control group had an equivalent on this documatation sheet. Thus, i.e. bradycardia, apnea, decreased oxygen-saturation, choking/coughing, vomiting or gastric residuals as reason for no feeding or feeding less than five minutes were documented. On this sheet the breathing method for each meal was registered: spontaneous, CPAP or mechanical ventilation.
Main criterion was volume intake on days 14, 21 and 28 after birth. The results of an infant were included into the final evaluation if at least five meals were given by nipple on day 28. According for the feeding rhythm at 12 daily meals six had to be fed by nipple over a minimum of five minutes on day 28 – at eight meals per day this was the case for all eight meals. The median volumes were tested with a two-side Wilcoxon-Test at α = 0,05. As a statistical estimation of the minimum number of infants required was not possible due to lack of studies on drinking quantities at VLBW infants after drip feeding, this study was designed as pilot study with 10 infants per group.
BITTE BEACHTEN: Der Ergebnisteil in diesem Artikel wird nach abgeschlossenem Promotionsverfahren bzw. nach Veröffentlichung zugänglich!
PLEASE NOTE: The chapter "Findings" in this article will be accessible after acceptance process of the doctoral thesis is concluded - or after publication!
Unfortunately, literature in the last almost 40 years does not give any indication of the drinking volume of VLBW infants after having been drip fed. Therefore a direct comparison of our results is not possible.
One reason for the median volume intake being larger in control group both on day 14 and day 21 might be the small number of infants examined. On basis of drinking quantities measured on day 28 a statistical minimum of about 300 VLBW infants per group would be necessary to achieve significance with 80% probability. Looking at this large figure, a reasonable realisation seems to require multi-center study design.
Nevertheless, median drinking quantity on day 28 in intervention group exceeds the results of the control group infants. This could lead to the assumption of intervention group infants surpassing controls provided that the study was continued over day 28.
Another factor taking influence on the result may be immaturity of sucking and swallowing processes in the VLBW infants. Between gestation week 13 and 14 fetuses are in position to swallow fluid pouring into its mouth [148 DeVries et al. 1982, 61 Conway 1994, 60 Medoff-Cooper et al. 1995]. The isolated ability to suck and swallow appears in gestation week 28 [139 Goldson 1987, 140 Shaker 1990]. At this stage there often is a lack in synchronization between suck and swallow resulting in the infant tiring and thus making oral feeding difficult [141 Volpe 1987]. Swallowing reflex first appears around gestation week 18 though protection from aspiration arises at a later point [149 Humphrey 1970]. It takes until 32nd week of gestation for sucking and swallowing to be coordinated [139 Goldson 1987, 140 Shaker 1990, 9 Tudehope et al. 1996]. The infants included into this study regularly were younger than 29 weeks of gestation. For this reason observed infants reached gestation week 32 only after oder with the end of the observation period, reaching until day 28 after birth. Hence, immature coordination of suck and swallow in study infants can be presumed.
Drinking of the diet is one of the first complex senso-motoric skills of the neonate [68 Iwayama et al. 1997]. Effective feeding is characterised by a well-coordinated ensemble of sucking, swallowing and breathing – let alone the infant´s interest for food intake [62 Ramsay et al. 1996, 60 Medoff-Cooper et al. 1995, 92 Selley et al. 1990]. Apart from that other factors have to be taken into consideration to reach efficient food intake: e.g. heart- and ventilation frequency, muscle tone or behavioural status of the infant [144 Case-Smith 1988, 61 Conway 1944].
Efficient sucking in the VLBW infant consists of strong sucking bursts, high sucking pressure and long sucking periods [118 Mathew 1991, 60 Medoff-Cooper et al. 1995]. In bottle feeding an average sucking rate of one burst per second can be anticipated [95 Pollitt, 62 Ramsey, 66 Daniëls et al. 1986]. This sucking frequency in VLBW infants shows a correlation neither to specific feeding experience of the infant nor to its feeding efficiency [66 Daniëls et al. 1986, 62 Ramsey]. In a normal, coordinated sucking cycle the infant breathes in between swallowing [114 Balint et al. 1948, 78 Bu´Lock et al. 1990] – in an ideal cycle sucking, swallowing and breathing are in a ratio of 1:1:1 [115 Halverson 1944, 116 Wolff 1968, 140 Shaker 1990].
Inefficient sucking patterns, though, steadily show an interruption of breathing through the act of swallowing [115 Halverson 1944] and breathing even seems to be subordinate [78 Bu´Lock et al. 1990]. Inefficient sucking composed of shorter sucking bursts, lower sucking pressure and shorter sucking periods indicates an impairment of the ability to ingest food – caused either by immaturity, desinterest, oral malformation or other medical disturbance [62 Ramsay et al. 1996].
Bu´Lock et al. demonstrated that VLBW infants of longer gestation at birth (37-40 weeks) have a considerably more stable coordination between sucking and swallowing at their disposal than infants of earlier gestation at birth have. At the latter sucking interrupts the continuous and quiet breathing rhythm in the awake infant. Typically, sucking periods in latter infants are associated with asynchronic ventilation being interrupted by series of rapid breaths (“breath attacks”). This sort of “apneic pauses” during food intake do not occur in VLBW infants of older gestation [78 Bu´Lock et al. 1990]. Considering the fact that VLBW infants in the study had were of early gestational age (< 29 weeks at birth) unstable ventilation is likely to have had a negative effect on sucking performance and therefore on the overall turnout of volume measurement.
Feeding in VLBW infants is considerably more difficult than in term infants [117 Gryboski et al. 1969]. It serves as a suitable example to demonstrate coordination of vital functions [33 Paul et al. 1989, 60 Medoff-Cooper et al. 1995]. Sucking infants experience exertion through the process of feeding [42 Glass et al. 1994, 33 Paul et al. 1989]. Whereas term infants usually can cope with this effort without showing major effects on ventilation or circulation, VLBW infants more frequently demonstrate serious changes in those parameters [129 Daniëls et al. 1988, 130 Rosen et al. 1984]. For immature and unstable infants feeding may represent a negative stressor [42 Glass et al. 1994] leading to physiological impairment such as apnea, bradycardia, hypoxemia, hypothermia or deterioration of medical status [136 Als et al. 1982, 142 Benda 1979]. A rapid milk flow during bottle feeding due to variation in hole size can lead to apnea and bradycardia likewise [86 Mathew et al 1990]. Lack in coordination of vital functions resulting in worsening of parameters caused by effort through feeding is a probable explanation for apnea, bradycardia and decrease of oxygen saturation monitored during the study. The role of the used nipple units also have to taken into account: Nuk-type nipples with laser-cut holes show little variation in hole size – in standard nipple units with mechanically drilled holes, however, notable differences in hole size have been measured [91 Mathew 1988, 89 Schindler]. During the study a Nuk-type nipple of Mapa had been utilized from day 5 until 13 after birth - a standard nipple of Milupa, though, over a longer period, from day 14 until 28 after birth. A number of irregularities in vital parameters may have been caused through substantially inconstant hole diameters.
On days 14 and 21 after birth infants of the control group achieved a greater median volume intake than intervention group infants. On day 28 after birth, however, a greater median drinking quantity was measured at intervention group members. Nevertheless, at a p-value of 0,42 on day 28, it statistically could not be demonstrated that drinking instead of nasogastric tube feeding during the first four weeks of life results in a larger volume intake by standard nipple. On basis of the results on day 28 after birth a minimum of about 300 infants per group would be necessary to obtain significance with an 80% probability. Considering the high number of infants realising such a study seems to require multi-center study design.
A re-examination of study infants will determine whether infants of the intervention group show feeding difficulties in a lesser extent than control group infants. In addition, it will investigate whether drip feeding during the first 28 days of life is positively effective on later drinking performance.
The authors are grateful to all nursing and medical staff on the concerned wards for their active support and interest in realising the study as well as to Milupa and Mapa for their kind cooperation.
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