Effects of head and body position on two- and three-dimensional configurations of the upper airway

The need for head rotation and abdominal compressions during bystander cardiopulmonary resuscitation

The current AHA-ECC guidelines for basic life support focus on the provision of good chest compressions with minimal interruptions for patients with presumed out-of-hospital cardiac arrest. Moreover, international consensus guidelines now support the use of chest compression-only cardiopulmonary resuscitation (CPR) instructions for dispatcher-assisted CPR given over the phone to untrained bystanders. However, evidence that strongly challenge these recommendations have been overlooked. A review of this evidence argues for the need for head rotation (a hands-free method of airway control) and abdominal compressions during bystander CPR.

Breathing type and body position effects on sternocleidomastoid and suprahyoid EMG activity

The objective of this study was to determine the effects of breathing type and body position on sternocleidomastoid and suprahyoid electromyographic (EMG) activity. The sample included 18 subjects with upper costal breathing type (study group) and 15 subjects with costo-diaphragmatic breathing type (control group). All individuals had natural dentition and bilateral molar support. EMG recordings at rest and while swallowing saliva were carried out by placing surface electrodes on the left sternocleidomastoid and left suprahyoid muscles. EMG activity was recorded while standing, seated upright, and in the lateral decubitus position. Upper costal breathing type subjects showed a significantly higher suprahyoid EMG activity at rest than costo-diaphragmatic subjects in all body positions studied (mixed model with unstructured covariance matrix). In the lateral decubitus position, both breathing types showed a significantly higher sternocleidomastoid EMG activity at rest and while swallowing saliva. The suprahyoid muscles demonstrated a significantly higher EMG activity at rest as well as in the lateral decubitus position (mixed model with unstructured covariance matrix). These results are relevant because sternocleidomastoid and suprahyoid muscles play an important role in controlling the head posture and mandible dynamics. The neurophysiological mechanisms involved are discussed.

Effectiveness of the jaw-thrust maneuver in opening the airway: a flexible fiberoptic endoscopic study

OBJECTIVE

A prospective study was carried out to find the exact site of obstruction in sleep model and to quantitatively evaluate the effect of Jaw-thrust maneuver (JTM) in opening the obstructed airway using flexible fiberoptic endoscope.

METHODS

Twenty-eight ASA physical status I or II patients with snoring symptom undergoing elective surgery were included. The patients were held in supine position without hyperextension of the neck. Having induced anesthesia, the base of the tongue and laryngeal inlet and/or epiglottis were visualized using endoscope. The patients' epiglottides were classified as leaf-shaped, curved (concaved or omega-shaped) and floppy types. We graded the airway opening at the level of epiglottis into six grades and obstruction at the tongue base level into four grades. The grades during inspiration (GrIns), expiration (GrExp) and after JTM (GrJTM) were recorded and compared with Pearson chi-square test.

RESULTS

The strictly curved (Omega-shaped or concaved) epiglottis supplied a salvage pathway for airflow that resisted collapsing with the posterior movement of the tongue base in 2 patients. When we compared GrIns with GrExp for epiglottis the difference was statistically significant (chi(2) = 0.001), but the difference for tongue base was not (chi(2) = 0.152). After JTM, GrJTM for both epiglottis and tongue base were significantly better than GrIns and GrExp (chi(2) < 0.001).

CONCLUSION

Tongue base was the principal site of obstruction although during the respiratory cycle the position of epiglottis changed prominently and increased the obstruction in inspiration. JTM alone significantly relieved the obstruction at the tongue base and epiglottis levels and increased the retroglossal airway.

Effect of titrated mandibular advancement and jaw opening on the upper airway in nonapneic men: a magnetic resonance imaging and cephalometric study

The aim of this study was to examine adaptive changes in the cross-sectional area of the upper airway during mandibular advancement and jaw opening and to explore whether these changes are directly related to morphologic features of the mandible. Fourteen nonapneic men participated in this study. A custom-made oral device was used to keep the mandible at 0% (F(0)V(0)), 50% (F(50)V(0)), 75% (F(75)V(0)), or 100% (F(100)V(0)) of maximum advancement, and at 50% (F(75)V(50)), 75% (F(75)V(75)), or 100% (F(75)V(100)) of maximum gape at F(75)V(0). Magnetic resonance imaging was used to investigate differences in the upper-airway cross-sectional area in these 7 positions. To eliminate excessive individual variation, changes in the mean (mean%) and minimum (min%) cross-sectional area of the upper airway were calculated as percentages of those at F(0)V(0). Cephalograms were taken to analyze morphologic features of the mandible. A dose-dependent change was seen when the mandible was advanced. The min% in F(100)V(0) was significantly greater than those in F(50)V(0) and F(75)V(0). The change in the upper airway size varied between subjects during jaw opening. At F(75)V(0), the min% of the whole upper airway was significantly associated with morphologic features of the mandible, such as the mandibular plane angle and lengths of the mandibular body and ramus.