An expandable endotracheal device includes: an elongated body configured to change from smaller-size state to a larger-size state； where in the smaller-size state, a perimeter, and thus a cross-sectional area, of the elongated body is restricted to facilitate insertion of the elongated body within a passageway of an in-use endotracheal tube； and where the elongated body is configured to: have at least a portion of the perimeter of the elongated body seal to a trachea of a subject； or provide an inner passageway extending through the elongated body along a length of the elongated body and with a boundary defining the inner passageway being configured to slidably receive a ventilation mechanism； or a combination thereof.
