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Predicting difficult airways: 3-3-2 rule or 3-3 rule?

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Abstract

Background

The goal of this study was to assess the value of the 3-3 rule and the 3-3-1 rule in predicting difficult airways.

Methods

The authors conducted an observational study over a 6-month period. For each consenting adult patient undergoing general anesthesia, preoperative patient characteristics and data regarding difficult airway assessments and airway outcomes were collected. The 3-3-2 rule, 3-3-1 rule and 3-3 rule were included in preoperative difficult airway assessments. The 3-3-1 rule is defined as an interincisor distance (IID) less than three fingers, a hyoid-mental distance (HMD) less than three fingers, and a hyoid-thyroid cartilage distance (HTD) less than one finger.

Results

Among the 732 patients who were successfully recruited in this study, 67 patients had difficult laryngoscopy (DL) (9.2 %), and 25 patients had difficult intubation (DI) (3.4 % of the total). All of the DI patients were also DL patients (25/67, 37.3 %). The AUC of the 3-3-2, 3-3, and 3-3-1 rules for predicting difficult laryngoscopy were 0.702, 0.709, and 0.631, respectively. Significant differences between the 3-3-2 and 3-3-1 rules as well as between the 3-3 and 3-3-1 rules were evident. The AUC values for the 3-3-2, 3-3, and 3-3-1 rules for predicting DI were 0.830, 0.822, and 0.725, respectively.

Conclusions

The 3-3 rule and the 3-3-2 rule are similar regarding their ability to predict difficult airways. A HTD less than two fingers or one finger is not predictive of DV or DI.

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Acknowledgments

We are gratified to our colleague of Department of Anesthesiology and Intensive Care Unit, Wannan Medical College First Affiliated Hospital, Yijishan Hospital for help with samples. This study was supported by the young and middle-aged scientific research funds of Wannan Medical College (No. WK2014F03, WK2014F38) and Provincial Quality Project of higher school (No. AH201410368106).

Conflict of interest

The authors have no potential conflicts of interest to disclose.

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Authors and Affiliations

  1. Department of Anesthesiology and Intensive Care Unit, Wannan Medical College First Affiliated Hospital, Yijishan Hospital, Wuhu, Anhui, China

    T. Yu, B. Wang, X. J. Jin, R. R. Wu, H. Wu, J. J. He & W. D. Yao

  2. Department of Anesthesiology, The First Affiliated Hospital of Anhui Medical University, Hefei, Anhui, China

    Y. H. Li

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  1. T. Yu
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  2. B. Wang
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  3. X. J. Jin
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  4. R. R. Wu
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  5. H. Wu
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  6. J. J. He
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  7. W. D. Yao
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  8. Y. H. Li
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Corresponding author

Correspondence to W. D. Yao.

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Yu, T., Wang, B., Jin, X.J. et al. Predicting difficult airways: 3-3-2 rule or 3-3 rule?. Ir J Med Sci 184, 677–683 (2015). https://doi.org/10.1007/s11845-015-1276-7

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  • DOI: https://doi.org/10.1007/s11845-015-1276-7

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