An assessment of introducers used for airway management.

Different introducers are available to assist with tracheal intubation. Subtle differences in the design of introducers can have a marked effect on safety and performance. The Difficult Airway Society's Airway Device Evaluation Project Team proposal states that devices should only be purchased for which there is at least a case-control study on patients assessing airway devices. However, resources are not currently available to carry out a case-control study on all introducers available on the market. This study comprised a laboratory and manikin-based investigation to identify introducers that could be suitable for clinical investigation. We included six different introducers in laboratory-based assessments (design characteristics) and manikin-based assessments involving the participation of 30 anaesthetists. Each anaesthetist attempted placement in the manikin's trachea with each of the six introducers in a random order. Outcomes included first-time insertion success rate; insertion success rate; number of attempts; time to placement; and distance placed. Each anaesthetist also completed a questionnaire. First-time insertion success rate depended significantly on the introducer used (p = 0.0016) and varied from 47% (Armstrong and P3) to 77% (Intersurgical and Frova). Median time to placement (including oesophageal placement) varied from 10 s (Eschmann and Frova) to 20 s (P3) (p = 0.0025). Median time to successful placement in the trachea varied from 9 s (Frova) to 22 s (Armstrong) (p = 0.037). We found that the Armstrong and P3 devices were not as acceptable as other introducers and, without significant improvements to their design and characteristics, the use of these devices in studies on patients is questionable. The study protocol is suitable for differentiating between different introducers and could be used as a basis for assessing other types of devices.

Fluoroscopic and radiographic assessment of variations in tracheal height during inspiration and expiration in healthy adult small-breed dogs.

The objective of this study was to document tidal variations in tracheal height during normal respiration in 19 healthy adult (> 1 y old) small-breed dogs (< 10 kg) using fluoroscopy and radiography. Each dog underwent tracheal fluoroscopic examination on inspiration and expiration while in a standing position (F-S) and in right lateral recumbency (F-RL), followed by radiographic projections obtained in right lateral recumbency. The percent variation in tracheal height during maximal inspiration and expiration was determined at 3 different locations [cervical region (CR), thoracic inlet (TI), and intrathoracic (IT) region]. When all imaging procedures and sites of measurement were considered, tracheal height varied during physiologic inspiration and expiration from 0% to 21.1%, with a mean of 4.5%. The mean percent variation in tracheal height was not significantly different among imaging modalities (F-S versus F-RL versus radiography) (P = 0.16) or measurement sites (CR versus TI versus IT) (P = 0.89). The body condition score (BCS) (P = 0.96), age (P = 0.95), and breed (P = 0.19) did not significantly influence the mean percent variation in tracheal height. The average variation in tracheal height during maximal physiological inspiration and expiration is small (< 6%) in most healthy adult small-breed dogs as assessed by fluoroscopy and radiography, although tracheal height may vary by as much as 21.1% in some healthy individuals. Inspiratory and expiratory radiographs acquired in right lateral recumbency provide an accurate assessment of tracheal height as an alternative to fluoroscopy.

L'objectif de la présente étude était de documenter les variations de la hauteur de la trachée durant la respiration normale chez 19 chiens adulte en santé (> 1 an) de petites races (< 10 kg) à l'aide de la fluoroscopie et de la radiographie. Chaque chien a été soumis à un examen fluoroscopique de la trachée lors de l'inspiration et de l'expiration alors qu'il était en position debout (F-S) et en décubitus latéral droit (F-RL), suivi d'images radiographiques obtenues en décubitus latéral droit. Le pourcentage de variation de la hauteur de la trachée durant l'inspiration et l'expiration maximales fut déterminé à trois endroits différents [région cervicale (CR), l'entrée thoracique (TI), et la région intrathoracique (IT)]. Lorsque toutes les procédures d'imagerie et les sites de mesure étaient considérés, la hauteur de la trachée variait durant l'inspiration et l'expiration physiologique de 0 % à 21,1 %, avec une moyenne de 4,5 %. Le pourcentage de variation moyen de la hauteur de la trachée n'était pas significativement différent parmi les différentes modalités d'imagerie (F-S versus F-RL versus radiographie) (P = 0,16) ou les sites de mesure (CR versus TI versus IT) (P = 0,89). Le score de condition corporelle (BCS) (P = 0,96), l'âge (P = 0,95), et la race (P = 0,19) n'influençaient pas significativement le pourcentage de variation moyen de la hauteur de la trachée. La variation moyenne de la hauteur de la trachée durant l'inspiration et l'expiration physiologique maximale est petite (< 6 %) chez la plupart des chiens adultes de petites races en santé telle qu'évalué par fluoroscopie et radiographie, bien que la hauteur de la trachée puisse varier jusqu'à 21,1 % chez certains individus en santé. Les radiographies à l'inspiration et à l'expiration obtenues en décubitus latéral droit fournissent une évaluation précise de la hauteur de la trachée comme alternative à la fluoroscopie.(Traduit par Docteur Serge Messier).

Assessment of three placement techniques for individualized positioning of the tip of the tracheal tube in children under the age of 4 years.

BACKGROUND: Accurate positioning of the tip of the tracheal tube (tube tip) is challenging in young children. Prevalent clinical methods include placement of intubation depth marks, palpation of the tube cuff in the suprasternal notch, or deliberate mainstem intubation with subsequent withdrawal. To compare the predictability of tube tip positions, variability of the resulting positions in relation to the carina was determined applying the three techniques in each patient. METHODS: In 68 healthy children aged ≤4 years, intubation was performed with an age-adapted, high-volume low-pressure cuffed tube adjusting the imprinted depth mark to the level of the vocal cords. The tube tip-to-carina distance was measured endoscopically. Thereafter, placements using (I) cuff palpation in the suprasternal notch and (II) auscultation to determine change in breath sounds during withdrawal after bronchial mainstem intubation were completed in random order. RESULTS: Tube tip position above the carina was higher when using depth marks (mean = 36.8 mm) compared with cuff palpation in the suprasternal notch (mean = 19.0 mm). Variability, expressed as sd, was lowest with the mainstem intubation technique (5.2 mm) followed by the cuff palpation (7.4 mm) and the depth mark technique (11.2 mm) (P < 0.005). CONCLUSION: Auscultation after deliberate mainstem intubation and cuff palpation resulted in a tube tip position above the carina that was shorter and more predictable than placement of the tube using depth markings.

Assessment of the mechanics of a tissue-engineered rat trachea in an image-processing environment.

OBJECTIVES: Despite the recent success regarding the transplantation of tissue-engineered airways, the mechanical properties of these grafts are not well understood. Mechanical assessment of a tissue-engineered airway graft before implantation may be used in the future as a predictor of function. The aim of this preliminary work was to develop a noninvasive image-processing environment for the assessment of airway mechanics. METHOD: Decellularized, recellularized and normal tracheas (groups DECEL, RECEL, and CONTROL, respectively) immersed in Krebs-Henseleit solution were ventilated by a small-animal ventilator connected to a Fleisch pneumotachograph and two pressure transducers (differential and gauge). A camera connected to a stereomicroscope captured images of the pulsation of the trachea before instillation of saline solution and after instillation of Krebs-Henseleit solution, followed by instillation with Krebs-Henseleit with methacholine 0.1 M (protocols A, K and KMCh, respectively). The data were post-processed with computer software and statistical comparisons between groups and protocols were performed. RESULTS: There were statistically significant variations in the image measurements of the medial region of the trachea between the groups (two-way analysis of variance [ANOVA], p<0.01) and of the proximal region between the groups and protocols (two-way ANOVA, p<0.01). CONCLUSIONS: The technique developed in this study is an innovative method for performing a mechanical assessment of engineered tracheal grafts that will enable evaluation of the viscoelastic properties of neo-tracheas prior to transplantation.

Simulated annealing implementation with shorter Markov chain length to reduce computational burden and its application to the analysis of pulmonary airway architecture.

A new way to implement the Simulated Annealing (SA) algorithm was developed and tested that improves computation performance by using shorter Markov chain length (inner iterations) and repeating the entire SA process until the final function value meets the solution criterion. The new approach coupled with the adaptive neighborhood method was tested on the Rosenbrock function in 4 and 13 dimensions. This implementation significantly improved the computation speed without degrading solution quality. The proposed implementation was used to characterize pulmonary architecture from micro CT image data demonstrating the algorithm's effectiveness especially for problems with high computational demand and when the solution quality requirement can be pre-specified. Using this implementation, detailed statistics of the morphometry of conducting airways from 12 male Sprague Dawley rats were obtained for each lobe.

[Endotracheal tube cuff and nitrous oxide: bench evaluation and assessment of clinical practice]. / Sondes d'intubation et protoxyde d'azote : étude sur banc et évaluation de la pratique clinique.

OBJECTIVE: To evaluate the risk of over-inflation of endotracheal tube cuffs (ETC) when used with nitrous oxide (N(2)O); to assess the rate of under and over-inflation of ETC when they are inflated without a manometer; to survey anesthesiologists about how they prevent these risks. METHODS: Nine types of endotracheal tube were studied on bench using various N(2)O concentrations; airway pressure levels and two sizes of trachea. Then, the rate and magnitude of over and under inflation pressure of ETC was assessed in our clinical practice. Finally, a national survey assessed how anesthesiologists prevented misuse of endotracheal tube with N(2)O. RESULTS: Pressure in ETC rose sharply using N(2)O, up to more than 40 cmH(2)O in six over nine tube types. Only two tube types (Mallinckrodt Hi-Lo Brandt and Lanz) were immune regarding N(2)O. Pratice study showed that ETC over inflation (>30 cmH(2)O) and under inflation (<20 cmH(2)O) was observed in 50 and 31 % of patients, respectively when cuff was inflated without a manometer. In France, a minority of anesthesiologists inflated ETC with a manometer (41 %) because in 61 % of theatres only manometers were available. CONCLUSION: There are risks induced by the use of N(2)O with tracheal tubes. This study provides data to sensitize users to these risks.

Stochastic morphometric model of the BALB/c mouse lung.

The laboratory mouse is often used as a human surrogate in aerosol inhalation studies. Morphometric data on the tracheobronchial geometry of three in situ lung casts of the Balb/c mouse lung produced by the Air Pollution Health Effects Laboratory were analyzed in terms of probability density functions and correlations among the different airway parameters. The results of this statistical analysis reveal significant differences in diameters and branching angles between major and minor progeny branching off from the same parent airway at a given airway bifurcation. Number of bronchial airways generations along a given path, expressed by the termination probability, branching angles, and daughter-to-parent diameter ratios indicate that the location of an airway with defined linear airway dimensions within the lung is more appropriately identified by its diameter (or its parent diameter) than by an assigned generation number. We, therefore, recommend classifying the mouse lung airways by their diameters and not by generation numbers, consistent with our previous analysis of the rather monopodial structure of the rat lung (Koblinger et al., J Aerosol Med 1995;8:7­19; Koblinger and Hofmann, J Aerosol Med 1995;8:21­32). Because of lack of corresponding information on respiratory airways, a partly stochastic symmetric acinar airway model was attached to the tracheobronchial model, in which the number of acinar airways along a given path was randomly selected from a measured acinar volume distribution. The computed distributions of the geometric airway parameters and their correlations will be used for random pathway selection of inhaled particles in subsequent Monte Carlo deposition calculations.

[Radiographic assessment of accuracy of tracheal tube placement in children]. / Ocena prawidlowego polozenia rurki dotchawiczej u dzieci na podstawie radiogramu klatki piersiowej.

BACKGROUND: Accidental migration of endotracheal tubes has been recognized by the European Resuscitation Council (ERC) as an important morbidity factor in ventilated children. Several equations have been proposed for prediction of the ideal position of the endotracheal tube, but none of them was found to be ideal. METHODS: We have retrospectively assessed the positions of endotracheal tubes in 108 intubated children. Infants were nasally intubated and oral intubation was used in older children. We compared the measured distances with theoretical lengths, obtained from various equations. RESULTS: We found that if the tube was placed according to the Lau equation (age/2+13 mm) or the ALS group equation (age/2+12 mm), the estimation was correct in 83% (Lau equation) and in 94.7% (ALS recommendations). CONCLUSION: Since results depended very much on the age and route of intubation, we suggest that extended studies may be recommended.

Use of human nasal cannulas during bronchoscopy procedures as a simple method for maintaining adequate oxygen saturation in pigtailed macaques (Macaca nemestrina).

Rising concerns over respiratory illnesses caused by agents such as avian influenza viruses and SARS coronavirus have prompted intensive research efforts and the resurgence of nonhuman primates as models for these human diseases. In the context of studying influenza infection and vaccine development, serial bronchoscopic procedures, including bronchial brush biopsies and bronchoalveolar lavage, were performed in pigtailed macaques (Macaca nemestrina). The possible need for oxygen supplementation during these procedures was anticipated because of the size of the animals relative to the 5-mm bronchoscope. We therefore monitored oxyhemoglobin saturation, a measure of arterial blood oxygen content, before and after insertion of the bronchoscope, during bronchoalveolar lavage, and after initiation of oxygen supplementation. Although more data are required to draw definitive conclusions, our findings suggested the need for oxygen supplementation during such procedures in nonhuman primates, despite the fact that human patients undergoing bronchoscopy and lavage do not routinely get oxygen unless they are already compromised. Our data also suggested that the need for supplementation could not be predicted from simple parameters such as size of the animal, presence of respiratory clinical signs, or experimental treatment. Finally, we show a simple and cost-effective method of using human nasal cannulas for delivering oxygen to pigtailed macaques during bronchoscopic procedures, and we believe that, after further testing, this method could be used safely and effectively in other nonhuman primate species.

Tracheal tube-tip displacement in children during head-neck movement--a radiological assessment.

BACKGROUND: Aims of this study were to assess the maximum displacement of tracheal tube tip during head-neck movement in children, and to evaluate the appropriateness of the intubation depth marks on the Microcuff Paediatric Endotracheal Tube regarding the risk of inadvertent extubation and endobronchial intubation. METHODS: We studied children, aged from birth to adolescence, undergoing cardiac catheterization. The patients' tracheas were orally intubated and the tracheal tubes positioned with the intubation depth mark at the level of the vocal cords. The tracheal tube tip-to-carina distances were fluoroscopically assessed with the patient supine and the head-neck in 30 degrees flexion, 0 degrees neutral position and 30 degrees extension. RESULTS: One hundred children aged between 0.02 and 16.4 yr (median 5.1 yr) were studied. Maximum tracheal tube-tip displacement after head-neck 30 degrees extension and 30 degrees flexion demonstrated a linear relationship to age [maximal upward tube movement (mm)=0 0.71 x age (yr)+9.9 (R(2)=0.893); maximal downward tube movement (mm)=0.83 x age (yr)+9.3 (R(2)=0.949)]. Maximal tracheal tube-tip downward displacement because of head-neck flexion was more pronounced than upward displacement because of head-neck extension. CONCLUSIONS: The intubation depth marks were appropriate to avoid inadvertent tracheal extubation and endobronchial intubation during head-neck movement in all patients. However, during head-neck extension the tracheal tube cuff may become positioned in the subglottic region and should be re-adjusted when the patient remains in this position for a longer time.

CT assessment of tracheal carinal angle and its determinants.

The aim of this study was to investigate the effect of body habitus, dimensions of the thoracic cavity, location of the carina within the mediastinum, and left atrial size on tracheal carinal angle using CT scan. The study population was drawn from the patients referred to CT scan for various indications. A total of 120 patients (65 men and 55 women; age range 17-85 years; mean age 56 years) who denied a history of prior thoracic surgery, and in whom CT scan excluded pulmonary fibrosis, moderate or severe emphysema, atelectasis, intrathoracic mass or adenopathy, pericardial or pleural effusion were prospectively enrolled. The interbronchial (IBA) and subcarinal (SCA) angles were measured on coronal reformatted images. The presternal and retrovertebral fat thickness, the anteroposterior and transverse diameters of the thorax, the distances from carina to the sternum and to the vertebral column were obtained at the level of carina. Three orthogonal dimensions and the volume of the left atrium were also assessed. The mean interbronchial angle was 77 degrees +/-13 degrees (range 49-109 degrees ) and subcarinal angle was 73 degrees +/-16 degrees (range 34-107 degrees ). IBA positively correlated with the female gender (r=0.25, p=0.007), body mass index (r=0.28, p=0.002), presternal (r=0.40, p=0.001) and retrovertebral fat thickness (r=0.31, p=0.001). The interbronchial angle was significantly greater in obese patients compared with lean patients (p=0.02). Both IBA and SCA were positively correlated with the left atrial volume (r=0.40, p=0.001 and r=0.34, p=0.001, respectively), and its transverse and craniocaudal dimensions. The carina-vertebral column distance inversely correlated with IBA (r=-0.42, p=0.001) and SCA (r=-0.41, p=0.001). The size of the thoracic cavity did not show significant relation to tracheal bifurcation angle. Tracheal bifurcation angle ranges widely in normal subjects, and absolute measurements of the carinal angle is of little diagnostic value. In addition to left atrial enlargement, female gender, obesity and close situs of carina relative to vertebral column are associated with greater tracheal bifurcation angle.

Computed tomographic assessment of the trachea in the German shepherd dog.

Computed tomographic (CT) examination of the trachea was performed in 10 German shepherd dogs to determine the normal value of some tracheal measurements under general anesthesia and in sternal recumbence position. Measurements obtained from nine segments were evaluated in four groups as the cranial cervical, caudal cervical, thoracic inlet and the thoracal tracheas. The inner transverse (T) and vertical (V) diameters were measured with the aid of electronic calipers from the software of the CT scanner. The cross-sectional lumen area (CSA) was calculated by using vertical and transverse diameters. The ratio of the transverse and vertical diameters (T/V) was also calculated. There was not any significant difference between thoracic inlet and thoracic tracheas, however, the mentioned regions were found to be significantly different from both cranial and caudal cervical regions in all measurements except the ratio of T/V. The ratio of T/V between 0.92 and 1.06 gradually changed and there was not any statistical difference between subsequent regions while differences were found among further regions. The largest CSA, seen in cranial cervical trachea was as 364.62 mm2 and decreased gradually to 309.29, 245.69 and 226.50 mm2 in caudal cervical, thoracic inlet and thoracic tracheas, respectively. From the point of view of technique, CT examination of the dog trachea was very easy and it was possible to take sensitive and repeated measurements. It, however, may be accepted as expensive and that it is disadvantageous to require general anesthesia. The data presented in this study represent tracheal values in the healthy German shepherd dog under the conditions of the study.

Evaluation of systematic errors in thyroid monitoring.

In this manuscript the thyroid is described by a new model. Efficiencies of a NaI(Tl) detector, for 364 keV photons, are calculated using Monte Carlo simulation. Contributions from thyroid size, detector placement and tissue overlay thickness, to the efficiency uncertainty, are evaluated considering the thyroid of a 12 year old subject as a limit for the adult thyroid. For a shielded 3" x 3" NaI(Tl) detector, placed at 20 cm from the neck, a contribution of 18% to the efficiency uncertainty was found.

A method of endotracheal intubation and pulmonary functional assessment for repeated studies in mice.

The ability to successfully intubate the trachea of mice and control their ventilation is important for longitudinal studies requiring recovery from anesthesia and repeated pulmonary function measurements or other evaluations, such as the use of radiological imaging (e.g., computed tomography or magnetic resonance imaging). We describe a method for rapid and repeated intubation of mice, with subsequent pulmonary function measurements at baseline and after an agonist challenge. We describe a simply constructed metal blade used as a laryngoscope to facilitate oropharyngeal exposure, transillumination of the neck to facilitate visualization of the trachea through the oropharynx, readily available polyethylene tubing to intubate the trachea, and a simple solenoid ventilator to maintain physiological ventilation and assess respiratory resistance and compliance. Brief infusions of acetylcholine through a needle into the jugular vein are used to assess the responsiveness of the airway smooth muscle.

Is there a better right-sided tube for one-lung ventilation? A comparison of the right-sided double-lumen tube with the single-lumen tube with right-sided enclosed bronchial blocker.

UNLABELLED: Anatomic variation between tracheal carina and the take-off of the right upper bronchus often makes the use of a right-sided double-lumen tube (R-DLT) or a single-lumen tube with right-sided enclosed bronchial blocker tube (R-UBB) (Univent) undesirable. This study compared the R-DLT with the R-UBB to determine whether there was any advantage of one over the other during anesthesia with one-lung ventilation (OLV) for right-sided thoracic surgeries. Forty patients requiring right lung deflation were randomly assigned to one of two groups. Twenty patients received a right-sided BronchoCath double-lumen tube, and 20 received a Univent tube with a bronchial blocker placed in the right mainstem bronchus. The following were studied: 1) time required to position each tube until satisfactory placement was achieved; 2) number of times that fiberoptic bronchoscopy was required (including one with the patient supine and one in lateral decubitus position); 3) number of malpositions after initial confirmation of tube placement; 4) time required until lung collapse; 5) surgical exposure; and 6) cost of tubes per case. No differences were found with any of these variables except that the cost of acquisition overall was greater for the R-UBB than for the R-DLT. No right upper lobe collapse was observed in the postoperative period in the chest radiograph in any of the patients studied. We conclude that either tube can be used safely and effectively for right-sided thoracic surgeries that require anesthesia for OLV. IMPLICATIONS: In this study, right-sided double-lumen tubes were compared with the Univent with right-sided bronchial blockers. The results indicate that either tube can be used for right-sided thoracic surgery.

Percutaneous tracheostomy: how to do it.

Percutaneous tracheostomy has become a commonly used technique in the management of the critically ill. It is a relatively simple procedure to perform at the bedside but it does have, as with any practical procedure, potential pitfalls and complications. Two commonly used methods are described.

Assessment of agonist- and cell-mediated responses in airway microsections by computerized videomicrometry.

The objective of this investigation was to develop a method for real-time measurement of changes in luminal area in microexplants of airways during pharmacological and physiological interventions. After guinea pigs were killed, tracheal rings (1- to 2-mm thick) were excised and placed in 300-microliters chambers. The area of the airway lumen was calculated as pixel number with the use of computerized videomicrometry. In 29 epithelium-intact airways, 10(-3) M acetylcholine (ACh) caused decrease in luminal area of 38.1 +/- 2.80% (P < 0.001 vs. 10(-9) M). Spontaneous tone also was demonstrated in 34 preparations from 4 guinea pigs; decrease in area of 17.0 +/- 1.45% after 60-min incubation in buffer alone was blocked completely by 10(-5) M indomethacin (P = 0.01). Luminal narrowing caused by < or = 10(-6) M ACh was reversed completely by 10(-6) M albuterol (P = 0.002). Addition of 100,000 activated human eosinophils caused 24.7 +/- 4.41% decrease in luminal area vs. 7.24 +/- 5.51% for nonactivated cells (P = 0.048). We demonstrate a real-time method for the assessment of auxotonic changes in airway caliber that utilizes microsections of explanted airways and permits the use of extremely small numbers of isolated cells to achieve physiological activation. Concentration-response characteristics and spontaneous tone are similar to those of large chamber preparations, and narrowing is reversed by beta 2-adrenoceptor activation.

Predicting difficult laryngoscopy for tracheal intubation: an approach to airway assessment.

Tracheal intubation by direct laryngoscopy is an essential skill for physicians working in the operating room, emergency room or intensive care unit settings. While tracheal intubation can usually be accomplished with ease by direct laryngoscopy, it is sometimes difficult or impossible because of coexisting disease or abnormal physical features. When recognized before attempts at tracheal intubation, virtually all difficult airways can be secured by the selected use of specialized tracheal intubation techniques, although many of these methods require special training, experience, assistance and equipment. When a difficult airway is unrecognized before attempts at intubation the results can be catastrophic because the personnel and equipment necessary for utilizing the specialized tracheal intubation techniques may not be immediately available and the patient's spontaneous respiratory efforts may have been eliminated by anesthetics or muscle relaxants. Thus, identifying patients who are likely to harbor an airway that cannot reliably be secured by simple direct laryngoscopy is an important skill for all acute or critical care physicians. There is an extensive research data base describing historical information, physical examination findings and radiographic features that are associated with the difficult airway. Reviewed collectively, one of the most important underlying concepts suggested by this body of research literature is that the difficult airway is a product of many anatomic and pathologic variables. A surprisingly wide variety of historical, physical examination and radiographic features associated with difficult direct laryngoscopy have been described. A rational approach to airway assessment, therefore, naturally includes a detailed history, a careful physical examination and inspection of relevant x-rays whenever time permits. As outlined in Table 5, there are specific questions to address that may warn the physician about possible airway difficulty. A number of airway assessment schemes based on physical examination findings have been proposed and tested. These schemes vary in their complexity and their clinical convenience. The simpler schemes fail to address the multifactorial nature of the problem, while the more complex systems are clinically impractical. Schemes combining the distance of the thyromental space and the visibility of the oropharyngeal structures, such as that proposed by Frerk, are perhaps the most practical and reliable of the methods proposed to date. Clearly, no one scheme is ideal. At present, preintubation airway evaluation remains a poorly quantified gestalt estimate of the chances for difficulty based on a complex juxtaposition of historical information and physical findings.(ABSTRACT TRUNCATED AT 400 WORDS)