Pre-discharge "car seat challenge" for preventing morbidity and mortality in preterm infants

Pilley E, McGuire W

Background - Methods - Results - References

Cover sheet

Title

Reviewers

Pilley E, McGuire W

Dates

Date edited: 16/11/2005
Date of last substantive update: 05/11/2005
Date of last minor update: / /
Date next stage expected 30/05/2007
Protocol first published: Issue 3, 2005
Review first published:

Contact reviewer

A/Prof William McGuire
Department of Paediatrics and Child Health
Australian National University Medical School
Canberra
AUSTRALIA
ACT 2606
Telephone 1: +61 2 62443077
Facsimile: +61 2 6244 3112
E-mail: william.mcguire@act.gov.au

Contribution of reviewers

Elizabeth Pilley (EP) and William McGuire (WM) developed the protocol jointly.

WM undertook the electronic and hand searches and screened the title and abstract of all studies identified in the primary search. Both authors completed the final review.

Internal sources of support

None

External sources of support

None

What's new

Dates

Date review re-formatted: / /
Date new studies sought but none found: / /
Date new studies found but not yet included/excluded: / /
Date new studies found and included/excluded: / /
Date reviewers' conclusions section amended: / /
Date comment/criticism added: / /
Date response to comment/criticisms added: / /

Text of review

Synopsis

There is no evidence that undertaking a pre-discharge "car seat challenge" benefits preterm infants.

The "car seat challenge" assesses whether preterm infants who are ready for discharge home are prone to episodes of apnoea (stopping breathing), bradycardia (slow heart rate), or desaturation (low oxygen levels) when seated in their car seat. However, it is not clear whether the level of oxygen desaturation, apnoea, or bradycardia detected in the car seat challenge is actually harmful for preterm infants. Additionally there is concern that the use of the car seat challenge may cause undue parental anxiety about the safety of transporting their infant in a car seat. Despite these uncertainties, and despite the widespread use of the test, we have not identified any randomised controlled trials that assessed whether undertaking a car seat challenge is beneficial or harmful to preterm infants.

Abstract

Background

Physiological monitoring studies indicate that some preterm infants experience episodes of oxygen desaturation, apnoea, or bradycardia when seated in standard car safety seats. The American Academy of Pediatrics recommends that all preterm infants should be assessed for cardiorespiratory stability in their car seat prior to discharge - the "car seat challenge". We aimed to assess the evidence to support this practice, specifically to determine whether the use of the car seat challenge prevents morbidity and mortality in preterm infants.

Objectives

To assess the available evidence from randomised controlled trials that pre-discharge cardiorespiratory monitoring in a car safety seat prevents morbidity and mortality in preterm infants.

Search strategy

We used the standard search strategy of the Cochrane Neonatal Review Group. This included searches of the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 3, 2005), MEDLINE (1966 - September 2005), EMBASE (1980 - September 2005), CINAHL (1982 - September 2005), conference proceedings, and previous reviews.

Selection criteria

Randomised or quasi-randomised controlled trials that compared pre-discharge cardiorespiratory monitoring in a car seat versus no monitoring in preterm infants in the week prior to planned discharge from hospital.

Data collection & analysis

The standard methods of the Cochrane Neonatal Review Group, with separate evaluation of trial quality and data extraction by two review authors, and synthesis of data using relative risk, risk difference and weighted mean difference.

Main results

We did not find any randomised controlled trials that fulfilled the eligibility criteria.

Reviewers' conclusions

It is unclear whether undertaking a pre-discharge car seat challenge is beneficial or harmful to preterm infants. Further studies are needed to determine whether the car seat challenge accurately predicts the risk of clinically significant adverse events in preterm infants travelling in car seats. If this is shown to be the case then a large randomised controlled trial is needed to provide an unbiased assessment of its utility in pre-discharge assessment.

Background

Following hospital discharge, the recommended mode of carriage for neonates and young infants travelling by car is in the semi-upright position in a rear-facing safety seat with a three- or five-point harness (AAP 1990; AAP 1999). Infants who are involved in collisions as car passengers are less likely to die or be seriously injured if they are restrained in a car seat appropriate for their size (Scherz 1976). However, standard car safety seats are designed for the "average" term newborn infant. Preterm infants are usually discharged from hospital when they reach a post-conceptional age of about 35 to 37 weeks, typically weighing less than 2.5 kilograms (Clark 2003). Some infants have a degree of respiratory and neurological immaturity at discharge. A minority has more significant problems; for example, chronic lung disease needing supplemental oxygen therapy. Careful attention to correct positioning in the car seat is essential to provide smaller infants with optimal restraint and protection from impact.

There is also concern that preterm infants may be prone to cardiorespiratory compromise when carried in car seats that are intended for larger term infants. Observational studies undertaken in the United States in the 1980s first highlighted the problems that preterm infants may face when using standard infant car safety seats. Bull and Stroup found that a range of standard car safety seats provided sub-optimal postural support for infants weighing about two kilograms because the strap distances from the seat bottom to the lowest shoulder strap and seat back to crotch strap were too long (Bull 1985). Willett and colleagues hypothesised that the tendency for infants carried in these seats to slouch would compromise respiration. In physiological monitoring studies, these investigators found that 30% to 60% of preterm infants who were otherwise ready for hospital discharge (average weight 2.3 kilograms) had frequent episodes of hypoxia (oxygen saturation less than 85%) during a 90 minutes observation period (Willett 1986; Willett 1989). The incidence of hypoxia was inversely related to birth weight and gestational age at birth. Preterm infants who had a previous history of apnoea were more prone to have episodes of apnoea and bradycardia. Randomly selected term infants (average weight 3.4 kilograms) did not become hypoxic or bradycardic during the same test period.

Largely because for these findings, the American Academy of Pediatrics (AAP) recommended in 1991 (updated 1996, 1999) that preterm infants should be observed and monitored for apnoea, bradycardia, or oxygen desaturation in their car safety seat before hospital discharge - the "car seat challenge" (AAP 1991; AAP 1996; AAP 1999). The guidelines advised that infants who experienced episodes of apnoea for more than 20 seconds, bradycardia (less than 80 beats per minute) or oxygen desaturation (less than 90%) should not travel in the car safety seat. In the United States the car-seat challenge is recommended not only for those preterm infants who have had respiratory problems, but also for infants born "near-term" at 35 to 36 weeks' gestation. Most of these infants are likely to have had no respiratory problems. In support of this very broad inclusion criterion, Merchant and colleagues have reported that about one quarter of "near-term" infants did not fit securely into standard car safety seats. One in eight healthy "near-term" infants had apnoeic or bradycardic events in their car seats (Merchant 2001).

Most neonatal units in North America have incorporated car seat challenges into their routine discharge assessment for preterm infants. In other countries, for example in Europe, use of pre-discharge car seat challenge in standard clinical practice is less established. Even in the United States, however, there is wide variation between units in the way that the test is used. Neonatal units differ in their indications for testing, the duration of observation and monitoring, and the criteria for "passing" the test (Williams 2003; Lincoln 2005). Evidence exists that neonatal unit-to-unit variation in the timing of hospital discharge for healthy preterm infants may be partly explained by differences in criteria for determining cardiorespiratory stability while in a car seat (Eichenwald 2001; Merritt 2003).

There is also variation in the recommended course of action for infants who "fail" the car seat challenge (Williams 2003). The alternatives include:
1. Delaying hospital discharge and re-testing the infant at a later date.
2. Modifying the seat with blanket rolls or inserts to provide sufficient postural support for the infant to pass the test.
3. Positioning the car safety seat at about 30 degrees rather than 45 degrees to reduce slouching and respiratory obstruction. It is not clear whether this position provides optimal restraint in the event of a collision.
4. Transporting the infant in a fully supine or prone position in a carry cot with restraint straps. However, standard carry cots are not designed to withstand the forces generated in a collision. Recumbent car beds and seats that are as effective as conventional car seats in limiting collision impact have been developed recently, but availability and cost has limited their use.
5. Giving the infant a respiratory stimulant such as theophylline.

The car seat challenge has been introduced on the assumption that the test will identify infants who are at risk of avoidable adverse events while in a car safety seat. However, there is little evidence that the degree and duration of episodes of desaturation, bradycardia, or apnoea that are seen in preterm infants who "fail" the car seat challenge are of clinical importance. Preterm infants who are otherwise ready for discharge commonly have self-limiting episodes of obstructive apnoea when not in car seats (often related to feeding) but the existing data indicate that the severity of these episodes is not related to the risk of acute life threatening events in early infancy (Barrington 1996; Cote 1998; Eichenwald 1997).

In common with other screening procedures, it is necessary to consider the effect of using the car seat challenge on all of the infants and families who are tested. Informing parents that their infant has evidence of cardiorespiratory instability during the car seat challenge may increase parental concern about their infant's general health. Even for those infants who "pass" the car seat challenge, but still have some episodes of desaturation or bradycardia while in the car seat, parents may not be fully reassured that their child is not at risk of adverse events in the car seat. It is possible, on the basis of a car seat challenge result, that parents may opt to carry their infants in their or other passengers' arms rather than in a car seat. It may also be important to consider whether the use of the car seat challenge in discharge assessments of all preterm infants has cost implications for health services. Undertaking cardiorespiratory monitoring for all preterm infants will occupy a substantial proportion of nursing time. Delaying hospital discharge for the infants who "fail" the test could have major effects on cot occupancy and availability in neonatal units. This may have consequences on intensive care availability resulting in more inter-hospital or inter-region transfers of preterm or unwell infants.

Objectives

To assess the available evidence from randomised controlled trials that pre-discharge cardiorespiratory monitoring in a car safety seat prevents morbidity and mortality in preterm infants.

Pre-specified subgroup analyses:
1. Infants born before 32 weeks' gestation or with birth weight less than 1500 grams and infants born at or after 32 weeks or with birth weights equal to or more than 1500 grams.
2. Infants who received supplemental oxygen therapy until at least 36 weeks post-conceptional age and infants who did not receive supplemental oxygen therapy until at 36 weeks post-conceptional age or beyond.
3. Infants who received supplemental oxygen therapy at hospital discharge and infants who did not receive supplemental oxygen therapy at hospital discharge.
4. Infants weighing less than 1800 grams or of post-conceptional age less than 35 weeks at hospital discharge and infants weighing at least 1800 grams or of post conceptional age at least 35 weeks at discharge.

Criteria for considering studies for this review

Types of studies

Controlled trials using random or quasi-random patient allocation. Cluster randomised trials where the unit of randomisation is a group of infants (for example, all infants cared for in a participating neonatal unit) were also be eligible for inclusion.

Types of participants

Preterm infants (born at less than 37 weeks gestation) thought to be ready for discharge from hospital within one week.

Types of interventions

1. Intervention:
The "car seat challenge" should consist of an assessment of cardiorespiratory stability in a car safety seat (either the infant's own seat or a similar seat) within one week prior to planned hospital discharge. Infants should be monitored for episodes of apnoea, desaturation, and bradycardia for at least a period of twenty minutes. We did not pre-define criteria for "passing" or "failing" the test or the course(s) of action that followed when an infant "failed" the test but were willing to accept these as defined a priori in individual trials.

2. Control:
Infants who did not have a formal assessment of cardiorespiratory assessment in a car seat prior to hospital discharge. This did not preclude families receiving advise regarding positioning in car seats or using blanket rolls or other inserts to prevent slouching.

Types of outcome measures

Primary:
1. All-cause mortality from randomisation until 12 months post-term.
2. All cases of death while in a car from randomisation until 12 months post-term.
3. All cases of "acute life-threatening events" while in a car (acute cardiorespiratory or neurological compromise that necessitates cardiorespiratory resuscitation (efforts to clear airway, promote pulmonary air entry, or support cardiac output)) from randomisation until 12 months post-term.

Secondary:
1. Post-conceptional age and post-natal age at hospital discharge.
2. Time from randomisation to hospital discharge.
3. Episodes of re-hospitalisation following cardiorespiratory or neurological compromise from randomisation until 12 months post-term.
4. Neurodevelopmental outcomes at greater than 12 months post-term measured using validated assessment tools such as Bayley Scales of Infant Development, and classifications of disability, including auditory and visual disability. The composite outcome "severe neurodevelopmental disability" will be defined as any one or combination of the following: non-ambulant cerebral palsy, developmental delay (developmental quotient less than 70), auditory and visual impairment.

Search strategy for identification of studies

We used the standard search strategy of the Cochrane Neonatal Review Group including electronic searches of the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 3, 2005), MEDLINE (1966 - September 2005), EMBASE (1980 - September 2005), and CINAHL (1982 - September 2005). The search strategy used the following text words and MeSH terms: Infant, Newborn OR Infant, Premature OR Infant, Low Birth Weight, OR Premature Birth, OR preterm OR low birth weight OR LBW OR premature; AND Patient Discharge OR Infant Equipment/ OR car seat OR safety seat. We limited the search outputs with the relevant filters for clinical trials. We did not apply any language restriction.

We undertook Science Citation Index "forward searches" for the physiological monitoring studies that first highlighted concerns about the cardiorespiratory stability of preterm infants in standard car safety seats (Bull 1985; Willett 1986; Willett 1989), and of the AAP publications that recommended use of the car seat challenge in pre-discharge assessments (AAP 1991; AAP 1996; AAP 1999).

We examined references in previous reviews. We handsearched the abstracts presented at the annual scientific meetings of the Society for Pediatric Research, the European Society for Pediatric Research since 1990 until 2004.

Methods of the review

1. William McGuire (WM) screened the title and abstract of all studies identified by the above search strategy and obtained the full articles for all potentially relevant trials. Elizabeth Pilley (EP) and William McGuire (WM) re-assessed independently the full text of these reports and excluded those studies that did not meet all of the inclusion criteria.

2. If eligible trials were found, EP and WM planned to use the criteria and standard methods of the Cochrane Neonatal Review Group to assess independently the methodological quality of these trials in terms of allocation concealment, blinding of parents or carers and assessors to intervention, and completeness of assessment in all randomised individuals.

3. EP and WM planned to extract any relevant information and data from each included study independently.

4. We planned to present outcomes for categorical data as relative risk, risk difference, and number needed to treat, with respective 95% confidence intervals. For continuous data, we planned to use the weighted mean difference with 95% confidence interval.

5. We planned to estimate the treatment effects of individual trials and examine heterogeneity between trial results by inspecting the forest plots and quantify the impact of heterogeneity in any meta-analysis using a measure of the degree of inconsistency in the studies' results (I- squared statistic). If we detected any statistical heterogeneity, we planned to explore the possible causes (for example, differences in study quality, participants, intervention regimens, or outcome assessments) using post hoc sub group analyses. We planned to use a fixed effects model for meta-analyses.

6. Cluster or group trials: We planned to use the inverse variance method to analyse the effect estimate from each individual cluster randomised trial for entry into meta-analyses (Cochrane Reviewer's Handbook). We planned to seek professional statistical advice to ensure that the trial was correctly analysed (for example, the cluster was the unit of analysis). We did not plan to undertake combined meta-analyses of cluster and non-cluster trials.

Description of studies

We did not find any trials for inclusion in this review. We did not find any studies that appeared eligible on the basis of title and abstract, but which were excluded from the review when the full text was examined.

Methodological quality of included studies

No studies were included in the review.

Results

No studies were included in the review.

Discussion

We did not find any randomised controlled trials that assessed the diagnostic utility of the car seat challenge in discharge assessment of preterm infants. Although it is plausible that pre-discharge cardiorespiratory monitoring might identify preterm infants who are prone to cardiorespiratory compromise while seated in a standard car seat, there are not yet any data to indicate whether the use of the test prevents mortality and morbidity. In deciding whether to use the car seat challenge in discharge assessment, it should be acknowledged that apparent cardiorespiratory abnormalities in infants born preterm, are common at the time of hospital discharge and that there are no monitoring criteria that predict an increased risk of sudden and unexpected death in infancy (Southall 1982). Staff in neonatal units and parents of preterm infants who are planning to use the test in discharge planning should also consider whether there are possible adverse consequences of the use of the car seat challenge in hospital discharge assessments.

Reviewers' conclusions

Implications for practice

It is unclear whether undertaking a car seat challenge is beneficial or indeed whether it causes harm.

Implications for research

1. Test validity and diagnostic accuracy: The degree to which the car seat challenge accurately predicts whether an infant will experience clinically important adverse events in a car seat after hospital discharge is not yet established. A study of diagnostic accuracy of this test may, however, be very difficult to undertake. This would require follow up of a large cohort of preterm infants, all of whom have a car seat challenge the findings of which are not known to any parents, carers, and clinicians. Applying the criterion standard would need a method of ascertaining all "clinically important" events (death, acute life-threatening events) for several months following hospital discharge. As a preliminary to such a study (if this was considered appropriate and feasible), it may be possible to determine in a population-based study, how commonly preterm infants experience serious adverse events in car safety seats.

2. Test clinical utility: The least biased assessment of whether the use of the car seat challenge prevents mortality or morbidity (including long term adverse neurodevelopmental outcomes), or causes harm would require a very large randomised controlled trial. It may be useful to determine whether such a trial would be supported by parents and carers. As well as determining the effect of the test on mortality, development and growth, it is important to assess parental satisfaction and health service costs. Qualitative research exploring parental perceptions and concerns might help to determine whether the car seat challenge alleviates or increases parental anxiety and may aid in identifying potential consequences of this.

Acknowledgements

Potential conflict of interest

None.

Characteristics of excluded studies

Study	Reason for exclusion
Khattak 2003	Study of cardiorespiratory monitoring in a car seat or car bed
Salhab 2003	Study of cardiorespiratory monitoring in a car seat or car bed

References to studies

References to excluded studies

Khattak 2003 {published data only}

Khattak A, Salhab W, Tyson J, Crandell S, Goodman B, Fisher L et al. How long should very low birth weight infants (VLBW) be monitored in a car seat or car bed before discharge? "Who is at greatest risk"? Pediatric Research 2003;53:Abstract 2563.

Salhab 2003 {published data only}

Salhab W, Khattak A, Tyson J, Crandell S, Goodman B, Fisher L et al. Should very low birth weight infants be assessed in a car seat or car bed before discharge? A two-center, randomized, cross-over trial. Pediatric Research 2003;53:Abstract 2502.

* indicates the primary reference for the study

Other references

Additional references

AAP 1990

American Academy of Pediatrics Committee on Accident and Poison Prevention. Safe transportation of newborns discharged from the hospital. Pediatrics 1990;86:486-7.

AAP 1991

American Academy of Pediatrics Committee on Accident and Poison Prevention. Safe transportation of premature infants. Pediatrics 1991;87:120-2.

AAP 1996

Committee on Injury and Poison Prevention and Committee on Fetus and Newborn, American Academy of Pediatrics. Safe transportation of premature and low birth weight infants. Pediatrics 1996;97:758-60.

AAP 1999

Bull M, Agran P, Laraque D, Pollack SH, Smith GA, Spivak HR, et al. American Academy of Pediatrics. Committee on Injury and Poison Prevention. Safe transportation of newborns at hospital discharge. Pediatrics 1999;104:986-7.

Barrington 1996

Barrington KJ, Finer N, Li D. Predischarge respiratory recordings in very low birth weight newborn infants. Journal of Pediatrics 1996;129:934-40.

Bull 1985

Bull MJ, Stroup KB. Premature infants in car seats. Pediatrics 1985;75:336-9.

Clark 2003

Clark RH, Thomas P, Peabody J. Extrauterine growth restriction remains a serious problem in prematurely born neonates. Pediatrics 2003;111:986-90.

Cote 1998

Cote A, Hum C, Brouillette RT, Themens M. Frequency and timing of recurrent events in infants using home cardiorespiratory monitors. Journal of Pediatrics 1998;132:783-9.

Eichenwald 1997

Eichenwald EC, Aina A, Stark AR. Apnea frequently persists beyond term gestation in infants delivered at 24 to 28 weeks. Pediatrics 1997;100:354-9.

Eichenwald 2001

Eichenwald EC, Blackwell M, Lloyd JS, Tran T, Wilker RE, Richardson DK. Inter-neonatal intensive care unit variation in discharge timing: influence of apnea and feeding management. Pediatrics 2001;108:928-33.

Lincoln 2005

Lincoln M. Car seat safety: literature review. Neonatal Network 2005;24:29-31.

Merchant 2001

Merchant JR, Worwa C, Porter S, Coleman JM, deRegnier RA. Respiratory instability of term and near-term healthy newborn infants in car safety seats. Pediatrics 2001;108:647-52.

Merritt 2003

Merritt TA, Pillers D, Prows SL. Early NICU discharge of very low birth weight infants: a critical review and analysis. Seminars in Neonatology 2003;8:95-115.

Scherz 1976

Scherz RG. Restraint systems for the prevention of injury to children in automobile accidents. American Journal of Public Health 1976;66:451-6.

Southall 1982

Southall DP, Richards JM, Rhoden KJ, Alexander JR, Shinebourne EA, Arrowsmith WA, et al. Prolonged apnea and cardiac arrhythmias in infants discharged from neonatal intensive care units: failure to predict an increased risk for sudden infant death syndrome. Pediatrics 1982;70:844-51.

Willett 1986

Willett LD, Leuschen P, Nelson LS, Nelson RM Jr. Risk of hypoventilation in premature infants in car seats. Journal of Pediatrics 1986;109:245-8.

Willett 1989

Willett LD, Leuschen P, Nelson LS, Nelson RM Jr. Ventilatory changes in convalescent infants positioned in car seats. Journal of Pediatrics 1989;115:451-5.

Williams 2003

Williams LE, Martin JE. Car seat challenges: where are we in implementation of these programs? Journal of Perinatal and Neonatal Nursing 2003;17:158-63.

Notes

Published notes

Contact details for co-reviewers

Dr Elizabeth Pilley, MB ChB
Senior House Officer
Paediatrics
Royal Free Hospital
Royal Infirmary
Glasgow
UK
G4 0SF
Telephone 1: 0044 0141 211 4000
E-mail: lizi_p@hotmail.com

The review is published as a Cochrane review in The Cochrane Library, Issue 1, 2006 (see http://www.thecochranelibrary.com for information). Cochrane reviews are regularly updated as new evidence emerges and in response to comments and criticisms, and The Cochrane Library should be consulted for the most recent version of the Review.