Because they still have poor head control and often experience flexion of the head
while in a sitting position, infants younger than 1 month in sitting devices might be at increased risk of upper
airway obstruction and oxygen desaturation.128, — , 132 In addition, there is increasing concern about injuries from falls resulting from car seats being placed on elevated surfaces.133, — , 137 An analysis of CPSC data revealed 15 suffocation deaths between 1990 and 1997 resulting from car seats overturning after being placed on a bed, mattress, or couch.136 The CPSC also warns about the suffocation hazard to infants, particularly those who are younger than 4 months, who are carried in infant sling carriers.138 When infant slings are used for carrying, it is important to ensure that the infant's head is up and above the fabric, the face is visible, and that the nose and mouth are clear of
obstructions.
While the small conducting
airways less than 2 mm in diameter are the major site of resistance to airflow in COPD, collapse greater than 50 percent of the larger central
airway during exhalation has been hypothesized to cause additional airflow
obstruction and respiratory morbidity.