Background - Methods - Results - Characteristics of Included Studies - References - Data Tables & Graphs
A number of measures have been suggested to assist in the maintenance of body temperature for infants in open cots. These have included extra clothing/bedding, warming up the nursery and heating the cot mattress. Metabolic effects were studied in infants in an open nursery cot provided with a small electric heating element below the mattress (Hey 1970). Oxygen consumption and heat loss fell compared to when the infants were studied in an unheated cot. In more recent years, a heated water-filled mattress (HWM) has been developed to maintain the temperature of a preterm infant who would otherwise be nursed in an air heated incubator (Tunell 1986). The mattress can be placed in a standard baby cot. With the HWM there is conductive heat transfer to the baby and indirect heating of the air around the baby (limiting convective heat loss), thus tending to keep the baby at a normal temperature. Preliminary clinical results indicated that during treatment in the heated cot, the skin temperature was generally found to be 35-37 degrees C in all parts of the body covered by a blanket, while the skin of the face exposed to room air was 3-4 degrees C lower (Tunell 1986). This may be beneficial, as it has been suggested that a lower skin face temperature may have a positive effect on thermal comfort and behavioural state (Bruck 1968).
Parents experience a feeling of loss following the birth of a preterm infant. This is compounded by the separation of an infant in an incubator from its mother. Stress and anxiety are frequently experienced by new mothers (Shields-Poe 1997). Maternal perceptions of their infants may influence infant development (Watt 1989). Maternal perceptions and feelings towards their infants may be more positive in the case of infants receiving cot-nursing because of greater maternal access to babies in open cots. Furthermore, nursing staff may perceive that better care may be provided to infants nursed in open cots due to increased accessibility.
The cost of an air-heated incubator is substantial compared to the relatively cheap alternative of an open cot. If it could be demonstrated that nursing an infant in an open cot instead of an incubator could be achieved without adverse effect, then considerable benefit could accrue in economic terms both in developing and developed countries.
Although there may be benefits of nursing infants in open cots, there may be potential risks. It is possible that infants nursed in cots may be handled more due to easier access, which could result in an increased risk of nosocomial infection. Conversely, there may be risks of nursing infants in incubators, such as exposure to excessive noise, resulting in negative effects on behavioural state and longer term development (Benini 1996).
Secondary:
1. To conduct subgroup analyses on infants <1500g and those small
for gestational age.
2. To conduct subgroup analyses in which differing types of cot-nursing,
i.e. cot-nursing with extra clothing/bedding, cot-nursing with warming
of the nursery, cot-nursing with a heating element placed below the mattress
and cot-nursing with a heated water-filled mattress, will be compared with
incubator care using manual temperature control or servo-control and with
the infants being either naked or clothed.
3. To conduct subgroup analyses according to the age at which cot-nursing
was introduced (from birth or later during the neonatal period).
Secondary:
Oxygen consumption (ml/kg/min)
Length of hospital stay (days)
Breast feeding at hospital discharge
Episodes of nosocomial sepsis
Maternal perceptions of infant's condition
Maternal stress and anxiety
Nursing perceptions of ability to provide care
Cost
Death
Planned sub-group analyses:
Birth weight <1500g
Infants small for gestational age
Interventions:
- cot-nursing with extra clothing/bedding
- cot-nursing with warming of the nursery
- cot-nursing with heating element below the mattress
- cot-nursing with heated water-filled mattress
All publications retrieved from the search were assessed for inclusion independently by the two reviewers. The methodological quality of each trial was assessed and data were extracted independently by the two reviewers. Differences were resolved by discussion. Additional information was requested from the authors of each trial as necessary for clarification of methodology or data (Green-Abate 1994, Sarman 1989a, Sarman 1989b, Sarman 1992, Sarman 1993).
Standard methods of Cochrane Neonatal Review Group were used to synthesise the data. For individual trials, mean differences (and 95% confidence intervals) are reported for continuous variables. For categorical outcomes, the relative risk and number needed to treat where appropriate (and 95% confidence intervals) are reported. For the meta-analysis, weighted mean differences (and 95% confidence intervals) are reported for continuous variables, and the typical relative risk and number needed to treat where appropriate (and 95% confidence intervals) for categorical outcomes. A fixed effects model was used.
The crossover trial (Sarman 1992) in this review reported data taken from the end of the first observation period before the one crossover, therefore these data were included in the meta-analysis. The means and standard deviations from the Green-Abate 1994 trial on weight gain for the two intervention groups were combined for the overall comparison using methods as described in Armitage 1994. Subgroup analyses were performed as proposed when data permitted.
Included trials:
Four trials involving 173 infants are included in this review. One
trial of 12 infants (Sarman 1992) utilised a
cross-over design.
Participants in the studies were quite diverse with the weight in the studies of Green-Abate 1994 and Sarman 1989b ranging from 1000 - 1999g, thus including some lighter babies than the Sarman 1989a and Sarman 1992 studies where mean weights were 1582g and 1458g. The Sarman 1989b study also included babies who were hypothermic at the time of enrolment. Furthermore the setting for the Green-Abate 1994 and Sarman 1989b studies was in a developing country compared to a developed country for the other two studies.
The intervention in the four trials was cot-nursing with a heated water-filled mattress. The control babies received routine care in an air heated incubator. The study of Green-Abate 1994 was a three-arm trial that also studied cot-nursing in a room heated with a manually controlled space heater. In all included trials infants in the incubator groups were nursed naked apart from wearing a nappy.
Primary outcomes in the studies included weight gain (g/kg/day) and body temperature measurements. Body temperatures were variably obtained from the forehead, axilla, abdomen, foot and rectum (Green-Abate 1994, Sarman 1989a, Sarman 1989b). Green-Abate 1994 reported the core-to-skin temperature gradient. The secondary outcome of oxygen consumption was measured by indirect calorimetry (Sarman 1989a, Sarman 1992).
Information was sought from the authors of three trials (Sarman 1989a; Sarman 1989b; Sarman 1992) concerning the method of randomisation blinding. In the case of Sarman 1989a and Sarman 1989b, information was sought concerning mean body temperature as it was presented in graphical form only in the publications. Furthermore information was requested from Green-Abate 1994 on the number of babies that had hypothermic and hyperthermic episodes. However, at the time of undertaking this review, no additional information had been received.
For further details refer to table, Characteristics of Included Studies
Trials not included:
Three trials were excluded from this review. One trial studied infants
randomised to care with and without a heated water mattress (Marks
1984), but both groups were nursed in an incubator. Two trials assessed
a water bed compared to a standard mattress (Darragh
1994; Deiriggi 1990), but again both groups
were nursed in incubators.
One report (Sarman 1993) is awaiting assessment pending further information, as it was unclear whether or not the infants were subsets of other trials (Sarman 1989a; Sarman 1989b). This report concerned mothers' perceptions of preterm infants treated in an incubator or on a heated water-filled mattress. In addition to mothers completing a questionnaire, a semi-structured interview was undertaken. The first part of the study was performed in Sweden, while the second part was performed in Turkey.
One ongoing trial was identified (Gray 1999).
Blinding of intervention and outcome was not achieved.
Completeness of follow-up
In the Green-Abate 1994 study five
infants were excluded from the analysis in the publication due to death
related to incidental illnesses. Two had been randomised to the incubator
group, two to the heated water-filled mattress group and one to the space-heated
group. The five infants have been included in this review for the outcome
of death prior to hospital discharge. In the Sarman
1989a study, there were fewer babies examined in weeks two and three
compared to week one as babies were transferred to an ordinary cot when
the study endpoint for an individual baby had been reached (mattress temperature
of 36 degrees C for those randomised to the heated water-filled mattress
group and an air temperature of 30 degrees C in the incubator for the incubator
group).
1. Comparison of cot-nursing vs incubator care
Four trials of 173 infants contributed to this comparison. Data were
available for two of the pre-specified primary outcome measures, body temperature
and weight gain, and for the secondary outcomes of oxygen consumption,
not breast feeding at hospital discharge and death prior to hospital discharge.
Primary outcomes:
Body temperature
A statistically significant higher mean body temperature was shown
for the infants in the cot-nursing group when compared to the incubator
group (data from one cross-over trial, Sarman 1992)
- [mean difference (MD) 0.30 degrees C; 95% confidence interval (CI) 0.10,
0.50]. However, the clinical importance of this difference is questionable.
Weight gain
The Green-Abate 1994 and Sarman
1989a trials provided data on weight gain (g/kg body weight/day) subgrouped
by week. The results showed no significant differences between the cot-nursing
and incubator groups in either weeks one, two or three, either in the individual
trials or in the meta-analysis (week one WMD -2.05 g/kg/day; 95% CI -5.97,
1.87; week two WMD 0.89 g/kg/day; 95% CI -0.69, 2.47; week three WMD 0.35g/kg/day;
95% CI -4.41, 5.11). While the Green-Abate
1994 trial did not report any statistically significant differences
in caloric intake between the groups during the trial period, these data
were not provided by Sarman 1989a.
Secondary outcome measures:
Oxygen consumption (ml/kg/min)
Two trials contributed data for the outcome of oxygen consumption (Sarman
1989a; Sarman 1992). Neither trial found
evidence of effect, and no significant difference between the two groups
was found in the meta-analysis (WMD -0.17 ml/kg/min; 95% CI -0.47, 0.13).
Not breast feeding at hospital discharge
The Sarman 1989a and Sarman
1989b trials collected data on breast feeding on discharge. Sarman
1989b found no evidence of effect, but Sarman
1989a found a reduction in the number of infants not breast feeding
at discharge that was of borderline statistical significance. In the meta-analysis,
cot-nursing resulted in a reduction in the number of infants not breast
feeding at discharge [typical relative risk (RR) 0.52; 95% CI 0.28, 0.94;
typical risk difference (RD) -0.24; 95% CI -0.44, -0.04]. The number needed
to treat (NNT) was 4 (95% CI 2, 25).
Death prior to hospital discharge
No significant difference was shown for the outcome of death prior
to discharge, either in the individual trials (Green-Abate
1994, Sarman 1989b) or in the meta-analysis
(typical RR 0.64; 95% CI 0.30,1.47).
2. Comparison of cot-nursing with heated water-filled mattress and incubator
care
Four trials with 149 infants were included in this comparison.
Primary outcomes:
Body temperature
Data on mean body temperature were obtained from the Sarman
1992 trial with the results being the same as for the overall comparison.
Weight gain
No statistically significant difference was shown in weight gain in
either weeks one, two or three of treatment, either in the individual trials
involving a total of 69 infants (Green-Abate
1994; Sarman 1989a) or in the meta-analyses:
weighted mean difference (WMD) and 95% CI for weeks one, two and three
were 0.16 g/kg/day (-4.58, 4.91), 0.80 g/kg/day (-0.83, 2.44) and 1.21g/kg/day
(-3.77, 6.18) respectively.
Secondary outcomes:
For the secondary outcome measures of breast feeding at hospital discharge
and oxygen consumption, the same trials were included as for the overall
comparison and hence the same results were obtained. No statistically significant
difference was shown for death, the only other reported secondary outcome,
either in the individual trials (Green-Abate
1994, Sarman 1989b) or in the meta-analysis:
(typical RR 0.68; 95% CI 0.31, 1.48), (two trials involving 137 infants).
3. Comparison of cot-nursing using warming of the nursery vs incubator
care
One trial involving 45 infants was included in this analysis (Green-Abate
1994). Infants receiving cot-nursing with warming of the nursery had
less weight gain than those in the incubator group during week one (MD
-5.90 g/kg/day; 95% CI -11.13, -0.67. No statistically significant differences
were shown for weight gain in weeks two (MD 1.40 g/kg/day; 95% CI -2.70,
5.50) or three (MD -6.00 g/kg/day; 95% CI -18.82, 6.82). Data on temperature
control were not presented in a way that could be included in the review.
The only secondary outcome that could be analysed was death and there was
no significant difference between the groups (RR 0.44; 95% CI 0.04, 4.49).
There were no available data for the primary outcome measures of episodes of cold stress or hyperthermia. Data were not available for the secondary outcome measures of length of hospital stay, nosocomial infection, maternal perceptions, maternal stress and anxiety, and nursing perceptions and cost. Due to insufficient data, other planned sub-group analyses could not be performed (for detail please refer to the secondary objectives of the review included under "Objectives").
The protocol did not place strict a priori definitions for the primary or secondary outcomes. Hence we used the operational definitions as reported by the investigators in the eligible trials.
This review has a number of limitations. The numbers of babies enrolled in the included trials are relatively small and data were not available for many of the pre-specified important clinical outcomes for this review. Some of the trials had outcomes presented only in a graphical form and thus these outcomes could not be included in the meta-analyses. Importantly, outcome measures related to safety including episodes of nosocomial sepsis were not addressed apart from the one study (Green-Abate 1994) that reported on mortality.
No trials were identified that compared care in newborn cots with additional warmth provided by extra clothing/bedding or a heated element below the mattress. Furthermore, comparisons of cot nursing interventions with varying methods for incubator care e.g. servo-controlled incubators, naked babies in incubators, could not be performed due to lack of available trials. In all included trials, babies in incubators were nursed in nappies only. Two trials (Sarman 1989b, Green-Abate 1994) took place in developing countries (Ethiopia and Turkey) where major differences in medical and nursing care were evident in comparison to developed countries. In the study carried out in Turkey (Sarman 1989b), a limited number of nurses was available in the nursery, with care largely being provided by the mothers. Accordingly the results may not be generalizable.
Due to a lack of data, this review was unable to assess the effect of cot-nursing on maternal perceptions. One study that is awaiting assessment (Sarman 1993) reported mothers' perceptions of their preterm infants treated in a cot with a heated water-filled mattress versus in an incubator. This pilot study suggested that the babies treated in a cot on a heated water-filled mattress were healthier and more vigorous than those in an incubator and that the mothers felt that their babies 'belonged to them'.
The heated water-filled mattress was designed as a cheap and technically simple device that when placed in a cot could be used as an alternative to incubator care (Tunell 1986). No studies were identified which compared the costs of cot-nursing compared to nursing a baby in an incubator.
While the results of the review do not provide reliable evidence that cot nursing is of benefit when compared to incubator care, neither do they suggest that there is an increased risk of adverse outcome. As included trials involved very small numbers of participants, caution is required in interpreting the results and applying them to current practice. One on-going trial (Gray 1999), designed to assess the benefits and risks of cot nursing with a heated water-filled mattress, may provide useful information in determining its role in current practice.
| Study | Methods | Participants | Interventions | Outcomes | Notes | Allocation concealment |
| Green-Abate 1994 | Blinding of randomisation - Yes Blinding of intervention - No
Complete follow-up - No Blinding of outcome measure - No |
67 infants of birthweight 1000 - 1999g. Exclusions were infants who needed respiratory support or parenteral feeding. | 1. Cot-nursing (SHR)
24 infants nursed in cots in a special care neonatal ward with space heating to maintain a room temperature between 27 and 32 degrees C. The babies were dressed with a cotton shirt and diaper and wrapped in a flannel blanket with the baby then being covered with a synthetic quilted blanket. Additional covering of the cot was given if body temperature fell <36 degrees C. A layer of clothing was removed if body temperature exceeded 37.5 degrees C. 2. Cot-nursing (HWM) 22 infants. Each infant was dressed with a cotton shirt and diapers and wrapped in a flannel blanket with the baby then being covered with a synthetic quilted blanket. The water temperature was adjusted to maintain a core body temperature of 36 -37.5 degrees C. 3. Controls: Incubator care. 21 infants nursed in air-heated incubators. with the temperature being adjusted manually to maintain a body core temperature of 36 -37.5 degrees C. Each infant was naked apart from diapers. |
Weight gain (g/kg body weight/day), energy intake, rectal, forehead, abdominal wall and dorsal foot temperature, mortality | 5 deaths were excluded in the publication but have been included in this review for the outcome of death. | A |
| Sarman 1989a | Blinding of randomisation - Can't tell
Blinding of intervention - No Complete follow-up - Yes Blinding of outcome measure - No |
34 preterm infants of weight 1400 - 1999g. Exclusions were infants
with infection, cardiopulmonary disease, gross malformations, requirement
for supplemental oxygen.
Gestational age across the groups was 28-35 weeks with a birthweight of 904 - 1980g. |
1. Cot-nursing (HWM).
17 infants nursed in cots on heated water-filled mattresses with temperature adjustment made so that rectal temperature was maintained at 35.5 - 37.5 degrees C. Each infant was dressed in a cotton shirt, nappy, cotton dress and a cotton cap for babies <1500g. 2. Controls: Incubator care. 17 infants nursed in air-heated incubators with temperature adjustment so that rectal temperature was maintained at 35.5-37.5 degrees C. The infants were naked apart from nappies. |
Weight gain (g/kg body weight /day), breast milk feeding volume, oxygen consumption - minimal and average, rectal, forehead, foot and mean skin temperature | B | |
| Sarman 1989b | Blinding of randomisation - Can't tell
Blinding of intervention - No Complete follow-up -Yes Blinding of outcome measure -No |
60 infants weighing 1000-2000g, not older than 7 days who were cared for in air-heated incubators Exclusions were infants with serious malformations, seizures, severe symptoms of respiratory distress requiring treatment with supplemental oxygen. | 1.Cot-nursing (HWM).
28 infants nursed in cots with HWM with temperature adjustment made to obtain a rectal temperature of 36.5 - 37.5 degrees C. Each infant was dressed in a nappy, cotton shirt, dress and cotton cap for infants <1500g. The infant was covered with a blanket. 2. Controls: Incubator care. 32 infnats nursed in air-heated incubators with temperature adjustment with the aim of obtaining a rectal temperature of 36.5-37.5 degrees C. The infants were naked apart from nappies. |
Rectal and axillary temperature on first to third days after hospital admission, mortality, breast feeding on discharge | B | |
| Sarman 1992 | Blinding of randomisation - Can't tell
Blinding of intervention - No Complete follow-up -Yes Blinding of outcome measure - No |
12 healthy infants of weight 1310-1635g being treated in air-heated incubators without supplemental oxygen | Crossover design. 12 infants were studied for a 6 hour period in 2
environments on consecutive days.
I. Cot-nursing (HWM)
2. Single-walled air-heated incubator with infant wearing a diaper only. |
Axillary, abdominal wall, dorsal foot temperatures, heart rate and resting oxygen consumption | B |
| Study | Reason for exclusion |
| Darragh 1994 | Both groups of infants were studied in incubators |
| Deiriggi 1990 | Both groups of infants were studied in incubators |
| Marks 1984 | Both groups of infants were studied in incubators |
| Study | Trial name or title | Participants | Interventions | Outcomes | Starting date | Contact information | Notes |
| Gray 1999 | KanMed Baby Warmer trial: an evaluation of thermal responses, weight gain and maternal perceptions | Babies of weight 1300-1500g at least 3 days of age, fully enterally fed being cared for in an air heated incubator | Nursing in cots on heated water-filled mattresses with the temperature adjusted to maintain an axillary temperature of 36.5 -37.0 degrees C. The babies will wear disposable nappies, cotton jackets, bonnets and booties. They will be swaddled in a cotton wrap and covered with a blanket. | Weight gain (g/kg body wt/day), duration to achieve body weight 1750g, mean skin temperature, number of temperature recordings <36.2 degrees C, number of episodes of apnoea, maternal perceptions of their preterm infants | February 1998 | Dr Peter Gray
Mater Mothers' Hospital South Brisbane Queensland Australia E-mail: pgray@mater.org.au |
Data analysis being undertaken |
Green-Abate C, Tafari N, Rao MR, Yu KF, Clemens JD. Comparison of heated water-filled mattress and space-heated room with infant incubator in providing warmth to low birthweight newborns. Int J Epidemiol 1994;23:1226-1233.
Sarman 1989a {published data only}
Sarman I, Tunell R. Providing warmth for preterm babies by a heated, water filled mattress. Arch Dis Child 1989;64:29-33.
Sarman 1989b {published data only}
Sarman I, Can G, Tunell R. Rewarming preterm infants on a heated, water filled mattress. Arch Dis Child 1989;64:687-692.
Sarman 1992 {published data only}
Sarman I. Thermal responses and heart rates of low-birth-weight premature babies during daily care on a heated, water-filled mattress. Acta Paediatr 1992;81:15-20.
Darragh J, Piper M, Byrne P, Watt MJ. The use of waterbeds for very low-birthweight infants: effects on neuromotor development. Dev Med Child Neurol 1994;36:989-999.
Deiriggi 1990 {published data only}
Deiriggi PM. Effects of waterbed flotation on indicators of energy expenditure in preterm infants. Nurs Res 1990;39:140-146.
Marks 1984 {published data only}
Marks KH, Calder PD, Nardis EE, Ultman JS. A warming mattress for premature infants. Pediatr Res 1984;18:333A.
Sarman I, Tunell R, Vastberg L, Carlquist U, Can G, Toparlak D. Mothers' perceptions of their preterm infants treated in an incubator or on a heated water-filled mattress: a pilot study. Acta Paediatr 1993;82:930-933.
Gray PH, Paterson S, Finch G, Hayes M. KanMed baby warmer trial: an evaluation of thermal responses, weight gain and maternal perceptions.
* indicates the primary reference for the study
Armitage PA, Berry G. Statistical Methods in Medical Research. 3rd edition. Oxford: Blackwell, 1994 p207-11.
Benini F, Magnavita V, Lago P, Arslan E, Pisan P. Evaluation of noise in the neonatal intensive care unit. Am J Perinatol 1996;13:37-41.
Bruck K. Which environmental temperature does the premature infant prefer? Pediatrics 1968;41:1027-30.
Glass L, Silverman WA, Sinclair JC. Relationship of thermal environment and caloric intake to growth and resting metabolism in the late neonatal period. Biol Neonate 1969;13:324-340.
Hey EN, O'Connell B. Oxygen consumption and heat balance in the cot-nursed baby. Arch Dis Child 1970;45:335-43.
Shields-Poe D, Pinelli J. Variables associated with parental stress in neonatal intensive care units. Neonatal Network 1997;16:29-37.
Sutter TWK, Phan D, Pierchala CE, Rishel W. Weaning of premature infants from the incubator to the open crib. J Perinatol 1988;8:193-198.
Tunell R, Sarman I. The water-filled heated mattress. An alternative to incubator care in developed and developing countries? In: Rolfe P, editor(s). Neonatal Physiological Measurements. London: Butterworths, 1986:419-23.
Watt J. Mothers' perceptions of their preterm neonates: Some possible consequences. NZ Family Physicians 1989;14:95-97.
02 Cot-nursing using heated water-filled mattress (HWM) vs incubator
care
02.01 Body temperature (degrees C)
02.02 Weight gain (g/kg/day)
02.03 Oxygen consumption (ml/kg/min)
02.04 Not breast feeding at hospital discharge
(survivors)
02.05 Death prior to hospital discharge
03 Cot-nursing using space heated room (SHR) vs incubator care
03.01 Weight gain (g/kg/day)
03.02 Death prior to hospital discharge