Sudden infant death syndrome (SIDS) is the leading cause of death among infants between 1 month and 1 year of age in the developed world. SIDS continues to be a phenomenon of unknown cause. The best approach to for prevention in high risk infants is unclear. Several substantial lines of evidence indicate that pacifiers have a protective effect on the incidence of SIDS. These studies were significantly powered and the results were consistent world-wide. The explanation for the protective effects of pacifiers on SIDS prevalence is unclear. A recent case report from New Zealand showed by means of nasopharyngeal films of a baby with and without a pacifier the possibility that sucking on a pacifier is associated with a forward movement of the tongue with enlargement of the upper airways' cross sectional area. Indeed, this hypothesis was originally postulated 30 years ago by Cozzi et al.

Working hypothesis and aims: Our hypothesis is that since the upper respiratory tract is that portion of the airway that imposes the greatest resistance to ventilation, sucking on a pacifier results in upper airway dilatation, thus greatly reducing upper airway obstruction and improving ventilation at a stage when infants are virtually obligate nasal breathers. It should be stressed that airway resistance is proportional to the 3rd power of the radius of the airway, thus even a relatively small increase in airway diameter may have a profound effect on airway resistance and respiratory mechanical work of breathing! In young infants and those with underdeveloped respiratory center drive, this decrease in the work of breathing could certainly be sufficient to minimize the risk of SIDS as described above.Thus, the aim of this study is to demonstrate the effect of sucking on a pacifier on upper airway patency.

Ten to 12 infants' parents who have been referred for clinical examination of MR (or CT with and without contrast) of the brain and neck and who require sedation to perform this examination will be asked to participate in the study. These infants represent a potentially ideal population in which to study the upper airway. They are already undergoing MR/CT, their upper airways images are recorded, are asleep, and do not typically have airway abnormalities. In these children, 2 images of the upper airways -one obtained while with and one obtained while without a pacifier -will be analyzed and compared. In no case will additional sedation be given to obtain the MR/CT images of the airway. If the patient begins to wake up during the investigational sequence, the sequence will be aborted.

To test our hypothesis using the functional method, we will compare LRT aerosol penetration with and without a pacifier.

Infants who are regular pacifier users and are receiving therapeutic aerosols regularly (e.g., ventolin, budicort) will be studied. Labeling the aerosol particles with a gamma emitting isotope marker and quantifying its deposition scintigraphically by means of a gamma camera is a simple, safe and commonly used method to assess aerosol deposition throughout the URT and LRT.

Inclusion Criteria:

-Infants who have been referred for clinical examination of MR (or CT with and without contrast) of the brain and neck -

• Regular (at least 2 hours a day) of a pacifier

Exclusion Criteria:

-Infants who have histories and/or signs, or symptoms of airway abnormalities -

primary care clinic, community sample