Standard Car Seat Research Articles

Analysis of Head Movement in KPSIT Dummies and the Impact of Seats and Seat Belts during Low-Speed Collisions 20 km/h.

The aim of this study was to compare the head displacement of the KPSIT C50 dummy, representing a 50th percentile male, with the KPSIT C5 dummy, representing a 5th percentile female, during low-speed collisions. Low-speed collisions, such as those occurring in urban traffic jams, are increasingly common. The research was conducted on a dedicated educational workstation designed to measure forces in seat belts. This study is part of a comprehensive research project on crash tests involving both volunteers and physical KPSIT dummies. The tests were conducted at a speed of 20 km/h to simulate real-world low-speed collision scenarios. The findings demonstrate that using a sports bucket seat with four-point or five-point harnesses significantly reduces head displacement compared with standard car seats. Such seating configurations enhance safety by minimizing the risk of head injuries, which can occur when airbags do not deploy during low-speed collisions. Moreover, the study highlights that standard three-point seat belts allow for greater forward head movement, increasing the risk of head contact with the vehicle's interior during collisions at speeds too low to trigger airbag deployment.

Effects of seat back height and posture on 3D vibration transmission to pelvis, trunk and head

Vibration transmission is essential in the design of comfortable vehicle seats but knowledge is lacking on 3D trunk and head motion and the role of seat back and posture. We hypothesized that head motion is reduced when participants’ upper back is unsupported, as this stimulates active postural control. We developed an experimental methodology to evaluate 3D vibration transmission from compliant seats to the human body. Wide-band (0.1–12 Hz) motion stimuli were applied in fore-aft, lateral and vertical direction to evaluate the translational and rotational body response in pelvis, trunk and head. A standard car seat was equipped with a configurable and compliant back support to test 3 support heights and 3 sitting postures (erect, slouched, and preferred) where we also tested head down looking at a smartphone.Seat back support height and sitting posture substantially affected vibration transmission and affected low frequency responses in particular for body segment rotation. According to our hypothesis a low support height proved beneficial in reducing head motion. Relevance to industryOur methodology effectively evaluates 3D wide-band vibration transmission from compliant seats to the human body. The lowest back support height reduced head motion but was perceived as least comfortable. This calls for seat designs which support but do not so much constrain the upper back. The head down posture enlarged head motion, pleading for computer system integration allowing heads up postures in future automated cars. The biomechanical data will serve to validate human models supporting the design of comfortable (automated) vehicles.

Laboratory Tests of the Control of the Child Seats using Method for the Vibration Comfort of Children Transported in Them

The article presents results of the laboratory studies of the impact of the child seats mounting method on the vibration comfort of children transported in them. The tested child seats were mounted forward facing the rear seat of a passenger car. The A seat was fastened with the ISOFIX base, while the B seat was fastened with standard car seat belts. During the tests, values of the vertical vibrations were measured on the seat of the child seat, the rear seat of the vehicle and the ISOFIX base. It was noted that the analyzed system, may be characterized by two different vibration transmission chains, which depend on the child seat mounting system (classic seat mounting system and ISOFIX system). These studies show the negative impact of using the ISOFIX base, which is confirmed by the Root Mean Square (RMS) values and the Vibration Dose Value (VDV), determined for the "A" seat secured with the ISOFIX base that were higher than the RMS and VDV for the "B" classic mounted seat.

Design of indenter rig for measuring seat cushion dynamic stiffness

Vibration induced on the car floor is transmitted to human body through seat structure, affecting both comfort and health. Seat structure components are mainly comprised of rigid frame and seat cushion. Previous studies have shown and suggested that the indenter is preferable option for replacing human subject in seat vibration experimental work when assessing the seat cushion dynamic characteristics. Indenter method offers more control, cheaper and less time intensive compare to other methods such as passive dummies, sandbag, and rigid mass. This paper proposes a design of indenter testing rig to measure the dynamic stiffness of seat cushion material. The rig was designed to operate at frequencies between 2 to 100 Hz and applied load of maximum 50 kg. The size of bed is proposed to be able to fit the size of standard sedan car seat. Modal analysis was conducted on indenter rig structure design to ensure the suitability of the design. Structural frame was designed to fit the mounting of the shaker used in this study. Six modes shapes were extracted from the modal analysis and its corresponding frequencies ranging from (121.63Hz – 507.3Hz). The lowest natural frequency for the proposed design of indenter testing rig occurs in the first mode of vibration with peak displacement of 174.04mm. From this result, it can be concluded that the proposed design met the criteria set and produces a fundamental frequency of greater than the operating range of the rig.

Exploring infant hip position and muscle activity in common baby gear and orthopedic devices.

Infant positioning in daily life may affect hip development. While neonatal animal studies indicate detrimental relationships between inactive lower extremities and hip development and dysplasia, no research has explored infant hip biomechanics experimentally. This study evaluated hip joint position and lower extremity muscle activity of healthy infants in common body positions, baby gear, and orthopedic devices used to treat hip dysplasia (the Pavlik harness and the Rhino cruiserabduction brace). Surface electromyography(EMG) and marker-based motion capture recorded lower extremity muscle activity and kinematics of 22 healthy full-term infants (4.2±1.6 months, 13M/9F) during five conditions: Pavlik harness, Rhino brace, inward-facing soft-structured baby carrier, held in arms facing inwards, and a standard car seat. Mean filtered EMG signal, time when muscles were active, and hip position (angles) were calculated. Compared to the Pavlik harness, infants exhibited similar adductor activity (but lower hamstring and gluteus maximus activity) in the Rhino abduction brace, similar adductor and gluteus maximus activity (but lower quadriceps and hamstring activity) in the baby carrier, similar but highly variable muscle activity in-arms, and significantly lower muscle activity in the car seat. Hip position was similar between the baby carrier and the Pavlik harness. This novel infant biomechanics study illustrates the potential benefits of using inward-facing soft-structured baby carriers for healthy hip development and highlights the potential negative impact of using supine-lying container-type devices such as car seats for prolonged periods of time. Further study is needed to understand the full picture of how body position impacts infant musculoskeletal development.

Clinically Asymptomatic Sleep-Disordered Breathing in Infants with Single-Ventricle Physiology

To assess clinically asymptomatic infants with single-ventricle physiology (SVP) for sleep-disordered breathing (SDB) in the supine and car seat positions using polysomnography. Polysomnography results also were compared with results of a standard Car Seat Challenge to measure the dependability of the standard Car Seat Challenge. This was an observational study of 15 infants with SVP. Polysomnography data included Obstructive Index, Central Index, Arousal Index, Apnea Hypopnea Index, and sleep efficiency. Polysomnography heart rate and oxygen saturation data were used to compare polysomnography with the standard Car Seat Challenge. Polysomnography demonstrated that all 15 infants had SDB and 14 had obstructive sleep apnea (Obstructive Index ≥1/hour) in both the supine and car seat positions. Infants with SVP had a statistically significant greater median Obstructive Index in the car seat compared with supine position (6.3 vs 4.2; P=.03), and median spontaneous Arousal Index was greater in the supine position compared with the car seat (20.4 vs 15.2; P=.01). Comparison of polysomnography to standard Car Seat Challenge results demonstrated 5 of 15 (33%) of infants with SVP with abnormal Obstructive Index by polysomnography would have passed a standard Car Seat Challenge. Infants with SVP without clinical symptoms of SDB may be at high risk for SDB that appears worse in the car seat position. The standard Car Seat Challenge is not dependable in the identification of infants with SVP and SDB. Further studies are warranted to further delineate its potential impact of SDB on the clinical outcomes of infants with SVP.

On the assessment of vibroloading of vehicle drivers in agricultural production

In order to ensure safe working conditions for drivers, strict requirements are imposed on the smooth running of agricultural vehicles. The purpose of this research was to study the vibration load on the driver’s seat when driving vehicle under agricultural conditions. Studies have revealed that the standard KamAZ-43255 car seat string system effectively damps vibrations with the frequency of more than 16 Hz, and practically does not damp vibrations below 4 Hz. It was determined that: at all speeds, the maximum values of vibration acceleration in the vertical plane are located in the second octave at the frequency of 2.0 Hz; peak values of vibration acceleration of the driver’s seat in the horizontal plane are located in the third octave at frequencies of 3.15 4.1 Hz; maximum mean square accelerations in the vertical plane are 3.76 times higher than the maximum permissible standards; at vehicle speed of V = 20 km/h, the acceleration of the driver’s seat in the vertical plane exceeds the permissible values in 3.9 times, in the horizontal plane it exceeds the permissible values in 2.75 ... 2.79 times. Therefore, on agricultural vehicles, it is necessary to install spring systems that are adaptive to operating conditions.

The impact of the unbalanced rear wheel on the vibrating comfort of the child seat

Abstract The paper presents the results of research on the assessment of vibration comfort of child seats in a passenger car. The research involved the impact of wheel unbalance on the size and frequency characteristics of vibrations to which a small passenger is exposed - a child transported in a standard car seat placed on the back of a car. The studies recorded the acceleration of the car floor, the seat of the child seat and the seat of the car under the child seat, for various speeds. The results were analysed to determine the intensity of the vibrations generated by the unbalanced wheel. Based on the obtained results, the degree of vibration comfort of the child seat has been assessed.

Use of car beds for infant travel: a review of the literature.

Discharging neonates in a proper car safety seat is standard of care in the United States and many other countries. However, not every neonate can be safely positioned in a standard semi-upright car seat. In these cases, providers may opt for a travel device that allows the infant to lie flat, either supine or prone, known as a car bed. Minimal evidence exists to guide providers on car bed safety and help determine which infants would benefit from discharge in a car bed. In this article, we provide a comprehensive summary of existing literature on the safety of car beds for motor vehicle travel, car bed use in specific patient populations, and car beds vs. car seats for infants at risk of adverse cardiorespiratory events, including preterm infants with Hg-O2 desaturations in the car seat. We discuss recommendations for the follow-up of infants discharged in a car bed in order to safely transition back to a car seat.

Impact of muscle contraction upon head stabilisation during forward acceleration

Introduction: The impact of muscle contraction upon head movements induced by a forward acceleration was studied as a model for low impact car-accidents. The purpose of our research is to examine: (i) whether and by which mechanism neck muscle contraction is induced after onset of the movement; and (ii) if voluntary neck muscle contraction prior to the movement affects head motion. Subjects and methods: Eight healthy volunteers (mean age 21.4 years) were included in this study. Volunteers were sitting on a standard car seat mounted on a sled. The computer-controlled, motor-driven sled was forward accelerated with 0.6 g. In test series 1, head and body movement were detected with a standard video camera (20 ms per frame) and accelerometers mounted on the head without interference with muscle activity. Muscle activation was detected by simultaneous measurement of surface EMG of m. splenius capitis, m. trapezius (descending part), m. scalenis medius, m. sternocleido mastoideus, m. digastricus (anterior belly), m. mylohyoideus, m. pectoralis major, m. quadriceps, tibialis anterior and triceps surae. The subject's movements and muscle activity were examined during forward sled acceleration when: (i) the subjects were relaxed and could not anticipate the precise start of sled acceleration; (ii) when they contracted all body muscles for about 4 s prior to and during the sled acceleration; and (iii) when head and trunk were fixed to the chair. The same subjects were accelerated in test series 2, but now head and trunk movements were measured with a better time resolution by use of a high-speed video camera (500 Hz) and accelerometers mounted on the head (bite board), body and sled. Head and body movements were measured under conditions 1 and 2 as described above. Reproducibility was tested by repeating each test condition once, including repositioning of the subjects, the accelerometers and body fixed sell spot markers. Results and conclusions: The current experimental set-up allows a low-cost evaluation of head and body movements induced by low impact velocity impulses. We observed that sudden whole body acceleration induces head accelerations that exceed the acceleration of the impact by a factor of 2–3-fold. After the impact, the head first remains stationary in space while the sled and trunk move forward (relative head and upper trunk translation). Subsequently, head and trunk rotate backwards, ultimately followed by an additional retroflexion of the head alone. Precontraction and anticipation of the impact leads to a faster increase of general muscle tone. It does not affect the initial translation but leads to a reduction of about 30–35% of head rotations and head angular velocities. The muscle contraction is most like a generalised alerting response. It should be noted that the current results were obtained at a loading level of 0.7 g, which is far below the 5–12 g levels observed in rear-end collisions. Since the current study shows only small influences of the muscle contraction, it is assumed that the contraction will not be strong enough to limit the larger head and trunk motion with greater impacts and does not reduce the probability of getting a whiplash injury.

Car Seat Safety for High-Risk Infants

Most neonates discharged from the hospital are able to go home in a standard car safety seat. Some infants, though, require special devices to ensure their safe travel. NICU nurses must have the knowledge and skills to comfortably and competently give vital information to parents preparing to take their infant home. This article is intended to increase awareness among NICU nurses of the potential dangers babies face when placed in a car seat. It provides a basic overview of car seat safety for infants being discharged home from an NICU and includes references for those who seek further information on this topic.

The Effect of Seat Belt Use on the Cervical Electromyogram Response to Whiplash-Type Impacts

Objective The objective of this study was to determine the effect of a standard 3-point lap-and-shoulder seat belt and car seat on the electromyogram (EMG) response of the cervical muscles to increasing low-velocity impacts in comparison with that of a rigid seat and 5-point restraint. Methods Seventeen healthy volunteers were subjected to rear, frontal, right and left lateral and bilateral anterolateral, and posterolateral impacts with an acceleration varying from 4.4 to 16.8 m/s 2 while in a car seat with lap-and-shoulder seat belt. Results For rear-end impacts, whether straight on, right posterolateral, or left posterolateral, all muscles generated 50% or less of the maximal voluntary contraction (MVC) EMG. In straight-on rear impacts, the sternocleidomastoid was symmetrically the most active; however, in posterolateral impacts, the sternocleidomastoid contralateral to impact direction was more active than its counterpart. For a right lateral impact, at the highest acceleration, the left splenius capitis generated 47% of its MVC and the left trapezius did 46% of its MVC. In a left lateral impact, the right splenius capitis generated 48% of its MVC and the right trapezius did 57% of its MVC. In a straight-on frontal impact, the left trapezius generated 35% of its MVC and the right trapezius did 48% of its MVC. In a left anterolateral impact, the right splenius generated 60% of its MVC and the right trapezius did 66% of its MVC. Similarly, in a right anterolateral impact, the contralateral splenius muscle increased its activity to 52% of its MVC and the left trapezius was at 52% of its MVC. Conclusions Compared with previously reported impact studies with a rigid seat and 5-point harness, the use of a 3-point lap-and-shoulder seat belt with a standard car seat did not appear to adversely affect cervical muscle response. In very-low-velocity and low-velocity impact experiments, seat belt and seat type may not significantly alter cervical EMG and kinematics.

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

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

The Effect of a 3-Point Harness Restraint and Car Seat in Whiplash-Type Lateral Impacts

Seventeen healthy volunteers were subjected to right and left lateral impacts 5.0, 6.8, 9.2, and 16.8 m/s acceleration while positioned in a Volvo car seat with lap and shoulder seat belt restraint in laboratory setting. The purpose of this study was to determine the effect of using a standard 3-point lap and shoulder seat belt and Volvo car seat on the response of the cervical muscles to increasing low-velocity lateral impacts. A previous study of lateral impacts in a 5-point harness restraint with head and trunk in neutral posture suggests that the burden of impact is borne primarily by the splenius capitis muscle contralateral to the direction of impact. That study, however, used a nonstandard harness for automobiles, and other studies suggest that a lap-and-shoulder seat belt may increase the risk of whiplash injury. Triaxial accelerometers recorded the acceleration of the 1) sled, 2) torso at the shoulder level, and 3) head of the participant, while bilateral electromyograms of the sternocleidomastoids, trapezii, and splenii capitis were also recorded. For participants experiencing a right or left lateral impact, the muscle responses increased with increasing levels of acceleration (P < 0.05). The time to onset and time to peak electromyogram for most muscles also showed a trend to progressively decrease with increasing levels of acceleration. The peak head accelerations relative to the sled ranged from 2.5 to 10.6 m/s. When the impact was a right lateral impact, at the highest sled acceleration, the left splenius capitis generated 47% of its maximal voluntary contraction (MVC), and the left trapezius also 46% of its MVC; the left and right sternocleidomastoid, right splenius capitis, and right trapezius generated 29% or less of their MVC. For the highest level of acceleration in a left lateral impact, the right splenius capitis generated 48% of its MVC and the right trapezius 57% of the MVC, the left and right sternocleidomastoid, left splenius capitis, and left trapezius generated 29% or less of their MVC. In both directions of impact, the contralateral splenius capitis and trapezius showed a statistically significant difference in the EMG response compared with other muscles (P < 0.05). For participants experiencing a frontal impact, whether straight-on, right or left anterolateral, the muscle responses increased with increasing levels of acceleration (P < 0.05). The time to onset and time to peak electromyogram for most muscles also showed a trend to progressively decrease with increasing levels of acceleration. In a straight-on frontal impact, the trapezii (TRPs) muscles showed the greatest EMG response compared with the remaining muscles (P < 0.05). Compared with previously reported impact studies with a 5-point harness and rigid seat, the use of a 3-point lap and shoulder seat belt with car seat does not appear to adversely affect the cervical muscle response. In very-low- and low-velocity impact experiments, seat belt and seat type may thus not be particularly relevant to cervical EMG and kinematics.

Aspects of seat modelling for seating comfort analysis

The development of more comfortable seats is an important issue in the automotive industry. However, the development of new car seats is very time consuming and costly since it is typically based on experimental evaluation using prototypes. Computer models of the human–seat interaction could accelerate this process. The objective of this paper is to establish a protocol for the development of seat models using numerically efficient simulation techniques. The methodology is based on multi-body techniques: arbitrary surfaces, providing an accurate surface description, are attached to rigid bodies. The bodies are connected by kinematic joints, representing the seat back recliner and head restraint joint. Properties of the seat foam and frame have been lumped together. Further, experiments have been defined to characterise the mechanical properties required for the seat model for comfort applications. The protocol has been exemplified using a standard car seat. The seat model has been validated based on experiments with rigid loading devices with human-like shapes in terms of force–deflection characteristics. The response of the seat model agrees well with the experimental results. Therefore the presented method can be a useful tool in the seat development process, especially in early stages of the design process.

Development of a damping seat slide to reduce whiplash injury

To prevent whiplash injury, a new seat slide was developed. In the case of a rear-end impact, the device allows the vehicle seat to slide backwards while damping this motion. Deformable steel profiles serve as damping elements. To activate the device, a trigger system is used which detects an acceleration threshold. Sled test experiments were performed to analyse the behaviour of the new system. The tests were conducted to mimic rear-end collisions with a delta-V of 16 km/h. A BioRID dummy was used as a human surrogate. The results indicate the beneficial influence of the damping seat slide on the occupant kinematics. In particular, the so-called S-shape deformation of the neck assessed by the neck injury criterion (NIC) is reduced. Comparing a standard car seat with and without the damping seat slide, it was shown that the NIC is reduced by approximately 40 per cent. Hence it was shown that besides the head restraint and the recliner that are used in other whiplash protection systems, the seat slide has the potential to prevent whiplash injury.

Estimation of spinal loading in vertical vibrations by numerical simulation

Objective. This paper describes the prediction of spinal forces in car occupants during vertical vibrations using a numerical multi-body occupant model. Background. An increasing part of the population is exposed to whole body vibrations in vehicles. In literature, vertical vibrations and low back pain are often related to each other. The cause of these low back pains is not well understood. A numerical human model, predicting intervertebral forces, can help to understand the mechanics of the human spine during vertical vibrations. Methods. Numerical human and seat models have been used. Human model responses have been validated for vertical vibrations (rigid and standard car seat condition): simulated and experimental seat-to-human frequency response functions have been compared. The spinal shear and compressive forces have been investigated with the model. Results. The human model seat-to-pelvis and seat-to-T1 frequency response functions in the rigid seat condition and all seat-to-human frequency response functions in the standard car seat condition approach the experimental results reasonably. The lumbar and the lower thoracic spine are subjected to the largest shear and compressive forces. Conclusions. The human model responses correlate reasonable with the volunteer responses. The predicted spinal forces could be used as a basis for derivation of hypothetical mechanisms and better understanding of low back pain disorders. Relevance In order to solve the problem of whole body vibration related injuries, knowledge about the interaction between human spinal vertebrae in vertical vibrations is required. This interaction cannot be measured in volunteer experiments. This paper describes the application of a numerical human model for prediction of spinal forces, that could be used as a basis for derivation of hypotheses regarding low back pain disorders.

Evaluation of a new visco-elastic foam for automotive applications

The geometry and mechanical characteristics of the automotive seat greatly influences the occupant kinematics in rear-end collisions. The head restraint is important particularly with respect to soft tissue neck injuries. While several studies analysed the effect of geometrical properties of head restraints, little is reported on the potential to reduce such injury by changing the material of the head restraint padding, i.e. the underlying foam. This study investigates whether the head restraint foam alone can be tailored to reduce whiplash injury. A newly developed visco-elastic (VE) foam was chosen, because advanced energy absorption properties are expected to produce beneficial effects on the occupant motion. The behaviour of the visco-elastic foam was evaluated by performing impact pendulum tests. The most important novel property of the foam thereby consists of its broad temperature range over which it keeps its advantageous visco-elastic deformation properties, while sustaining the ability to dissipate energy. The tests indicated in particular a broad glass transition temperature resulting in a stable impact behaviour over a temperature range of 5°C to 35°C. Applying this foam as a head restraint padding material, several sled tests using a standard car seat were performed. The tests were conducted to mimic rear-end collisions with a delta-v of 16 km/h. A BioRID dummy was used as a human surrogate. For the seat tested, the change of the foam resulted only in minor changes at room temperature, while the standard foam exhibited adequate performance. Additional changes of the head restraint geometry were shown to have a larger beneficial influence on the occupant kinematics.

CAD/CAM Concept of a Crash-Proofed, Light-Weighted Wheelchair to be Used as Driving and Transportation Seat by Disabled Users

An innovative wheelchair is developed within TRANSWHEEL (DE3013) project, with enhanced safety, comfort and maneuverability. It will be used as driver's or passenger's seat within private cars and other transportation means. Its safety against crash and its comfort will be first provided by using a standard car seat on the wheelchair mainframe. Then, a computer crash simulation will follow of CAD/CAM models of the wheelchair, the surrounding compartment of the car and their connecting mechanisms, together with the ergonomic design of the wheelchair. Comparison to actual crash-tests will lead to the final design of the initial wheelchair concept

Premature infants in car seats: effect of sleep state on breathing

Previous studies have shown that premature infants may be at risk for hypoxemia and bradycardia when placed in standard car seats. However, the relationship of such breathing abnormalities to sleep state have not been studied. The purpose of the present study was to investigate the effect of car seat positioning on respiratory patterns in preterm infants during sleep and to evaluate their relationship to sleep state. Complete polysomnography, including sleep and breathing parameters, was performed on twenty-eight premature infants. Each infant was randomly assigned to the car seat or prone (crib) position for the first recording period. Following the recording of at least two sleep cycles, the position was reversed. The percentage of active and quiet sleep was calculated and breathing parameters were measured. In the car seat, the infants spent significantly more time in active sleep and less time in quiet sleep than in the prone position, of the respiratory parameters, periodic breathing (PB) was significantly higher in the car seat. The presence of at least one abnormal breathing events (bradycardia, desaturation, PB apnoea) was also significantly higher in the car seat. An analysis of variance (ANOVA) of PB revealed significant sleep-state effect (active vs. quiet sleep), but no significant condition or interaction effects, indicating that PB was more frequent in active sleep regardless of the sleeping condition. It is concluded that increased active sleep in the car seat condition, rather than the positioning of the infant in the seat per se, may account for the increase in periodic breathing and possibly other breathing abnormalities reported in car seats.