The Car Seat Tolerance Screen (CSTS) is a routine observation period required for certain infants before hospital discharge. This screening is primarily conducted for babies born prematurely (less than 37 weeks gestation) or those with a low birth weight (under 5 pounds, 8 ounces or 2,500 grams). The test ensures the infant can safely travel home in a semi-upright car seat position without difficulty breathing or heart function. Failing the screen does not necessarily indicate a long-term medical problem, often reflecting a temporary issue with cardiorespiratory stability.
The Purpose of the Car Seat Tolerance Screen
The Car Seat Tolerance Screen assesses an infant’s ability to maintain a clear airway and stable vital signs when placed in the angled position of a car seat. The semi-reclined angle, typically between 30 and 45 degrees, can cause a small baby’s head to slump forward into a “chin-to-chest” posture. This position can compress the trachea, restricting the airway and compromising cardiorespiratory function.
During the test, the baby is placed in their own car seat and continuously connected to medical monitoring equipment for a minimum of 90 to 120 minutes, or for the duration of the car ride home if it is longer. Hospital staff closely track three specific physiological parameters to determine a pass or fail result. Failure is defined by an episode of apnea (a pause in breathing lasting more than 20 seconds), a sustained drop in heart rate (bradycardia below 80 beats per minute for at least 10 seconds), or oxygen desaturation. Oxygen desaturation occurs when the infant’s blood oxygen level falls below 90% for 10 seconds or longer, indicating the baby is struggling to manage the positional stress.
Immediate Medical Response to a Failed Screen
When an infant fails the Car Seat Tolerance Screen, the immediate result is a delay in the anticipated hospital discharge. The medical team’s first action is to remove the baby from the car seat and return them to a flat, supine position in a crib or warmer, which helps immediately stabilize their airway and vital signs. The infant is placed back on continuous cardiorespiratory and pulse oximetry monitors for a period of observation to ensure all vital signs return to and remain within the normal range.
A comprehensive medical evaluation begins to determine the underlying cause of the cardiorespiratory instability. This assessment may investigate various factors, including the immaturity of the respiratory control center, undiagnosed gastroesophageal reflux, or subtle issues with muscle tone that affect positioning. Sometimes a failed screen points to an underlying condition that requires further treatment or observation. The hospital staff communicates the results to the parents, explaining that the delayed discharge is a necessary safety measure to protect the infant during transport.
This period of heightened medical observation allows the care team to address any potential contributing factors before attempting the screen again. The infant remains hospitalized, often in a monitored environment like the Neonatal Intensive Care Unit (NICU) or a step-down nursery, until stability is confirmed. While a single failed test can be concerning, it primarily serves as an indicator that the baby needs additional time or intervention to safely manage the semi-upright position required for travel.
Corrective Measures and Retesting Protocol
Corrective measures focus on optimizing the infant’s positioning and the fit within the specific car seat the family plans to use. A certified Child Passenger Safety Technician or trained hospital staff will check that the car seat is set at the correct recline angle, typically around 45 degrees from the vertical, to prevent the head from slumping forward.
The fit of the infant in the seat is meticulously checked, ensuring the baby’s bottom is situated at the lowest point and their back is flat against the seat. Rolled blankets or washcloths, used only as directed by the hospital staff, may be placed alongside the infant’s head and trunk to provide lateral support and prevent side-to-side slumping. It is important that these supports are placed only at the sides and not under the infant, and that no aftermarket products are used, as these have not been crash-tested with the seat.
If the medical evaluation suggests an underlying issue, such as reflux contributing to the instability, the team may implement a temporary medical intervention. This could involve adjusting feeding schedules, administering medication to manage reflux symptoms, or starting a short course of supplemental oxygen therapy. Once adjustments are made, the infant is typically retested with the Car Seat Tolerance Screen after 12 to 24 hours to allow for recovery or the effect of medical changes to take hold. For infants who fail multiple retests, a rare alternative is discharge in a specialized car bed that allows them to lie flat, though this requires passing a screen in the car bed and a plan for eventual transition back to a traditional car seat.