Background: Knowledge of the influence of age on laryngeal dimensions is essential for all practitioners whose interest is the pediatric airway. Early cadaver studies documented that the larynx is conically shaped, with the apex of the cone caudally positioned at the nondistensible cricoid cartilage. These dimensions change during childhood, as the larynx assumes a more cylindrical shape. The authors analyzed laryngeal dimensions during development to determine if this relationship continues in unparalyzed children in whom laryngeal muscles are tonically active. The authors determined the relationships between the vocal cord, sub-vocal cord, and cricoid ring dimensions and the influence of age on these relationships. Methods: Infants and children undergoing magnetic resonance imaging with propofol sedation had determinations of the transverse and anterior-posterior (AP) dimensions of the larynx at the most cephalad level of the larynx (vocal cords) and the most caudad level (cricoid). Most patients had an additional measurement (sub-vocal cord) at a level between the vocal cords and the cricoid ring. Relationships were obtained by plotting age against laryngeal dimensions and the ratio of laryngeal dimensions at different levels within the larynx. Results: The authors measured transverse and AP laryngeal dimensions in 99 children, aged 2 months-13 yr. The relationship between the transverse and AP dimensions at all levels of the larynx did not change during development. Transverse and AP dimensions increased linearly with age at all levels of the larynx. In all children studied, the narrowest portion of the larynx was the transverse dimension at the level of the vocal cords. Transverse dimensions Increased linearly in a caudad direction through the larynx (P < 0.001), while AP dimensions did not change relative to laryngeal level. The shape of the cricoid ring did not change throughout childhood. Conclusions: In sedated, unparalyzed children, the narrowest portions of the larynx are the glottic opening (vocal cord level) and the immediate sub-vocal cord level, and there is no change in the relationships of these dimensions relative to cricoid dimensions throughout childhood.

Developmental Changes of Laryngeal Dimensions in Unparalyzed, Sedated Children

Ventilator-associated pneumonia is the most common nosocomial infection in the intensive care unit, and it is associated with prolonged hospitalization, increased health care costs, and high attributable mortality. During the past several decades, numerous studies focused on the crucial role of the endotracheal tube (ETT) in the pathogenesis of ventilator-associated pneumonia. Tracheal intubation thwarts the cough reflex, compromises mucocilliary clearance, injures the tracheal epithelial surface, provides a direct conduit for rapid access of bacteria from upper into the lower respiratory tract, and allows the formation of biofilm on the ETT surface. The combination of these factors puts the mechanically ventilated patient at great jeopardy of developing ventilator-associated pneumonia. Many preventive strategies have arisen from this understanding: control of intracuff pressure, aspiration of subglottic secretions, decontamination of subglottic area, use of antiseptic impregnated ETTs, and elimination or prevention of the ETT biofilm formation. The authors review the role of ETT management for the prevention of the ventilator-associated pneumonia.

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Ventilator-associated Pneumonia or Endotracheal Tube-associated Pneumonia?An Approach to the Pathogenesis and Preventive Strategies Emphasizing the Importance of Endotracheal Tube

A low-pressure cuff for tracheostomy tubes to minimize tracheal injury. A comparative clinical trial.

Eight commercially available soft cuff endotracheal tubes were studied to determine the relationship between inflation pressure distention of the cuff. Although the balloon cuff may be easily distensible in open air, when confined within the trachea small increments in the inflation volume may produce high pressures. This means that continuous external control of cuff pressure is required to prevent ischemia of the tracheal wall. Major tracheal complications in a busy ICU were examined before and after the introduction of a controlled pressure tube. Control of intratracheal cuff pressures decreased major tracheal complications tenfold and eliminated complications specifically related to the cuff.

Prevention of complications from prolonged tracheal intubation

Development of tracheal surgery: a historical review. Part 1: techniques of tracheal surgery

SUMMARY The pressures exerted on the tracheal wall by cuffed endotracheal tubes were measured in patients on intermittent positive pressure ventilation. It was found that these pressures can easily be made excessive and sufficient to encourage tracheal necrosis. These pressures exerted by the cuffs were not equally distributed around the tracheal circumference and varied also with the position of the head and with the level of consciousness.

G.T.G. Knowlson

Papers

The pressures exerted on the trachea by endotracheal inflatable cuffs