Dynamic anatomy of upper airway: an essential paradigm

Lateral neck radiography for prediction of difficult orotracheal intubation

BACKGROUND AND OBJECTIVES

Failed endotracheal intubation is a principal cause of morbidity and mortality in anesthetized patients. The aim of this study was to investigate the efficiency of lateral neck radiography in predicting difficult intubation.

METHODS

In a prospective triple-blind study, 100 patients (aged 18-89 yr), scheduled for elective surgery were randomly selected. Lateral neck X-ray was obtained from each of the patients before operation. Several angles and parameters on the X-ray were proposed to illustrate a relationship with easy or difficult intubation. A radiologist recorded these angles before the operation. An anaesthesiologist also determined the Mallampati score preoperation. At the time of intubation, two other anesthesiologists performed a laryngoscopy and, according to established criteria, identified the patients as easy or difficult intubation. The results were then compared with each other.

RESULTS

Fifteen patients were identified as having difficult intubation (laryngoscopy Grades III and IV). Sensitivity and specificity of the Mallampati Class test were 26% and 100%, respectively. The sensitivity and specificity of the lateral neck X-ray for three measured angles were 100%. The positive and negative predictive values (NPVs) for those angles were 100% and for Mallampati classification were 100% and 80%, respectively.

CONCLUSIONS

Compared to the Mallampati Class test, our method of analyzing the lateral X-ray, although not as easy and universally applicable as Mallampati Class test, proved to be a suitable method for predicting difficult intubation.

The pediatric airway

Good airway management technique is an essential skill for physicians in most specialties. This article begins with a review of basic airway anatomy and the physiology of the uninstrumented airway. This subject is of particular importance given the increasing use of procedural sedation and the increased recognition of sleep-disordered breathing in infants and children. A discussion of the various artificial airways and their advantages and disadvantages follows. The difficult airway is an important contributor to both patient morbidity and mortality. It is important to have a planned management approach available for the anticipated and, more importantly, the unanticipated difficult airway. The recommendations of the American Society of Anesthesiologists Taskforce on the Management of the Difficult Airway have good application for this important problem. The fetus with the prenatal diagnosis of a lesion that predicts a difficult airway presents a particular challenge. The utilization of an ex-utero intrapartum treatment method is presented as an important approach for the delivery and airway management of these infants. This section closes with a discussion of the prehospital airway management of the pediatric patient.

Design evaluation of commonly used rigid and levering laryngoscope blades

BACKGROUND

The shape of a laryngoscope blade affects the exposition of the larynx. This study evaluates and compares some rigid and levering blade designs based on previous investigative X-ray laryngoscopic studies.

METHODS

Five rigid laryngoscope blades (Miller #3, Standard Macintosh #3, Classical Macintosh #4 and English-Macintosh #3 and #4) and two levering laryngoscope blades (McCoy in neutral and maximally elevated positions and Flexiblade in three basic positions: straight, neutral, and maximally curved) were evaluated. This study assesses two parameters derived from the depth of insertion: the eye line deviation from the ideal straight view line to the vocal cords, and the space occupied by the blade behind the mandible, which affects the contact of the blade tip with the base of the tongue.

RESULTS

The best results on larynx exposition were produced by the English-Macintosh #4 at all insertion depths between 5 and 14 cm. It surpassed the Classical Macintosh #4 and both the English and Standard Macintosh #3. Although the Miller and the Flexiblade in a straight position afford a nearly ideal view line, both blades reduce the space reserved for the tongue behind the mandible. The McCoy with its tip maximally elevated provides limited view, while activation of the Flexiblade provides various ranges of larynx exposition.

CONCLUSION

The difference in shape and design of Macintosh blades affects their performance. The distal portion of a large-sized curved blade is more effective than the full length of a shorter blade. The #4 English Macintosh is a better choice for routine clinical use. The Flexiblade performs as a multiblade device and can therefore be used for both routine and difficult intubations.