Lengthening of the Trachea During Neck Extension: Which Part of the Trachea Is Stretched?
Bibliographic record
Abstract
BACKGROUND: We sought to determine the distances of the three segments of the airway from upper incisors to carina in intubated patients in three different neck positions. METHODS: Twenty patients undergoing elective surgery were studied. The airway was divided into three segments: upper incisor to vocal cords (UI-VC), vocal cords to sternal notch (VC-SN), and sternal notch to the carina (SN-CA). After general anesthesia and tracheal tube placement, the circuit was connected and the lungs ventilated. A bronchoscope was inserted through a ported elbow adapter until the tip just contacted carina. A marker tape was placed on the bronchoscope immediately above the adapter port. As the bronchoscope was withdrawn to the sternal notch (by transillumination), vocal cords and upper incisor (endoscopic visualization), three corresponding markers were placed along the bronchoscope. The three segments of the airway were obtained by measuring the distances between the four markers. Measurements were taken with the patient's neck in flexion (10 cm pillow), neutral (5 cm pillow), and extension (no pillow) positions. Repeated measure analysis of variance and paired t-tests were used for analysis of the data. RESULTS: The UI-VC, VC-SN, and SN-CA distances were 12.01 +/- 1.49, 5.37 +/- 0.95, 8.24 +/- 1.16 cm. From neck flexion to extension, UI-VC and VC-SN increased by 0.36 +/- 0.68 cm (P = 0.027) and 1.74 +/- 0.48 cm (P < 0.001) respectively; SN-CA decreased by 0.12 +/- 0.70 cm (NS). Overall, UI-CA increased by 1.99 +/- 0.70 cm (P < 0.001). SN-CA represented 64%, 61%, 56% of the VC-CA distance with the neck in flexion, neutral, and extension respectively. SN-CA did not change significantly among the head positions (NS). CONCLUSIONS: From neck flexion to extension, the UI-CA distance increased by 1.99 cm. The major contribution to this lengthening was an increase of the VC-SN distance by 1.74 cm; UI-VC increased by 0.36 cm whereas SN-CA did not change significantly. Averaging the three neck positions, SN-CA represented 60% of the VC-CA distance. Our findings may explain why tracheal tubes fixed at the mouth ascend in the trachea with neck extension.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".