The laryngeal neuromuscular mechanisms for modulating glottal posture and fundamental frequency are of interest in understanding normal laryngeal physiology and treating vocal pathology. The intrinsic laryngeal muscles in an in vivo canine model were electrically activated in a graded fashion to investigate their effects on onset frequency, phonation onset pressure, vocal fold strain, and glottal distance at the vocal processes. Muscle activation plots for these laryngeal parameters were evaluated for the interaction of following pairs of muscle activation conditions:(1) cricothyroid (CT) versus all laryngeal adductors (TA/LCA/IA),(2) CT versus LCA/IA,(3) CT versus thyroarytenoid (TA) and,(4) TA versus LCA/IA (LCA: lateral cricoarytenoid muscle, IA: interarytenoid). Increases in onset frequency and strain were primarily affected by CT activation. Onset pressure correlated with activation of all adductors in activation condition 1, but primarily with CT activation in conditions 2 and 3. TA and CT were antagonistic for strain. LCA/IA activation primarily closed the cartilaginous glottis while TA activation closed the mid-membranous glottis.

Fundamental to the pathogenesis of obstructive sleep apnea (OSA) is the interaction of physiologic and anatomic alterations of the upper airway. However, many patients with OSA have no identifiable abnormality of the upper airway, and they have been termed idiopathic. In an attempt to find a structural deviation in upper airway anatomy, we performed acoustic echography and cephalometric roentgenograms in 9 male patients with OSA and no clinical evidence of upper airway abnormality. Mean cross-sectional area of the pharynx by acoustic reflection was less in these patients (3.7 +/- 0.8 cm2) than in subjects in a control group (5.3 +/- 0.6 cm2)(p less than 0.001). Mean glottic cross-sectional area was less in the patient group (1.5 +/- 0.5 cm2) than in the control group (2.7 +/- 0.5)(p less than 0.001). There was a significant correlation between the number of apneas per sleep hour and pharyngeal cross-sectional area (r = 0.87, p less than 0.01). Cephalometric analysis indicated that the patients had smaller mandibles by a mean of 5.4 +/- 6.6 mm (p less than 0.05). The overall posterior displacement of the mandibular symphysis, which is representative of the skeletal support of the anterior pharyngeal wall and is dependent on both mandibular size and position, was highly significant (6.4 +/- 4.7 mm)(p less than 0.01). Furthermore, there was a significant correlation between the number of apnea episodes per sleep hour and the total posterior displacement (r = 0.67, p less than 0.05). This study indicates that patients with so-called idiopathic OSA may have an anatomic predisposition to the development of upper airway occlusion that may not be detectable on clinical examination.

PURPOSE: To evaluate a new videolaryngoscope and assess its ability to provide laryngeal exposure and facilitate intubation. METHODS: Five centres, involving 133 operators and a total of 728 consecutive patients, participated in the evaluation of a new video-laryngoscope [GlideScope (GS)]. Many operators had limited or no previous GS experience. We collected information about patient demographics and airway characteristics, Cormack-Lehane (C/L) views and the ease of intubation using the GS. Failure was defined as abandonment of the technique. RESULTS: Data from six patients were incomplete and were excluded. Excellent (C/L 1) or good (C/L 2) laryngeal exposure was obtained in 92% and 7% of patients respectively. In all 133 patients in whom both GS and direct laryngoscopy (DL) were performed, GS resulted in a comparable or superior view. Among the 35 patients with C/L grade 3 or 4 views by DL, the view improved to a C/L 1 view in 24 and a C/L 2 view in three patients. Intubation with the GS was successful in 96.3% of patients. The majority of the failures occurred despite a good or excellent glottic view. CONCLUSIONS: GS laryngoscopy consistently yielded a comparable or superior glottic view compared with DL despite the limited or lack of prior experience with the device. Successful intubation was generally achieved even when DL was predicted to be moderately or considerably difficult. GS was abandoned in 3.7% of patients. This may reflect the lack of a formal protocol defining failure, limited prior experience or difficulty manipulating the endotracheal tube while viewing a monitor.

Magnetic resonance imaging was used to quantify the vocal tract morphology of 129 normal humans, aged 2-25 years. Morphometric data, including midsagittal vocal tract length, shape, and proportions, were collected using computer graphic techniques. There was a significant positive correlation between vocal tract length and body size (either height or weight). The data also reveal clear differences in male and female vocal tract morphology, including changes in overall vocal tract length and the relative proportions of the oral and pharyngeal cavity. These sex differences are not evident in children, but arise at puberty, suggesting that they are part of the vocal remodeling process that occurs during puberty in males. These findings have implications for speech recognition, speech forensics, and the evolution of the human speech production system, and provide a normative standard for future studies of human vocal tract morphology and development.

Two hundred and fifty patients were assessed preoperatively using the Mallampati classification and by measuring their thyromental distances. The ease or difficulty of direct laryngoscopy was assessed at the time of induction of anaesthesia. Retrognathia was seen in 15.6% of patients and the incidence of difficult laryngoscopy without external laryngeal pressure was 8.2%. It was found that both assessments predicted less than two in three difficult laryngoscopies and had high false positive rates. It was found that external laryngeal pressure often improved the view of the glottis in difficult laryngoscopies.

We measured the separation of the vocal folds, the glottis chink, on inspiration and expiration during quiet breathing in 34 patients with varying degrees of airflow obstruction as measured by forced expired volume in one second, Width of the glottis chink was calculated from photographs of the vocal folds taken via a fiberoptic bronchoscope. To adjust the differences in photographic image size caused by variations in instrument position, we predicted the internal anteroposterior (A.P) diameter of the glottis in each patient. This was made possible by the observed high correlation (r = 0.79) between A.P diameter of the glottis and height demonstrated in a separate study in 49 adult cadavers. In patients with airflow obstruction, the glottis chink was narrowed during quiet breathing, particularly on expiration. Such differences in glottis width between patients could not be attributed to frequency of breathing or tidal volume. Indeed, during high frequency breathing (panting) at 1 to 3 Hz studied in 18 patients, further glottis narrowing was commonly observed in those with airflow obstruction. Furthermore, when 13 patients performed a maximal exhalation, in those with airflow obstruction, the glottis remained narrowed, whereas in patients with FEV1 greater than 80% predicted, the glottis opened to an inspiratory width.l These observations suggest that narrowing of the glottis potentially plays an important part in controlling airflow in patients with airway obstruction.

BACKGROUND Direct laryngoscopy frequently is modified in patients with known or suspected cervical spine injury. The goals of this study were to measure the degrees of head extension required to expose the arytenoid cartilages and glottis if neck flexion were not possible and to determine whether in-line stabilization maneuvers alter the amount of head extension. METHODS The subjects were anesthesized patients with normal cervical spines and Mallampati class 1 oropharyngeal views. Head extension was measured relative to a line drawn perpendicular to the table. Stabilization consisted of either passive immobilization, with the head held flat against a rigid board, or axial traction. RESULTS Without stabilization, arytenoid cartilage exposure and the best view of the glottis was achieved with a 10 +/- 5 degree (mean +/- SD) head extension and a 15 +/- 6 degree head extension, respectively (n = 31). Head immobilization reduced extension angles 4 +/- 5 degrees for arytenoid exposure and 5 +/- 6 degrees for best view compared with no stabilization. CONCLUSIONS Head immobilization reduced head extension necessary for laryngoscopy. If head extension is construed to be potentially dangerous in patients with cervical spine injuries, head immobilization without traction might be the preferable stabilization technique.