Predicting difficult airways: 3-3-2 rule or 3-3 rule?
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.
Department of Anesthesiology and Intensive Care Unit, Wannan Medical College First Affiliated Hospital, Yijishan Hospital, Wuhu, Anhui, China.
T
T
Yu
B
B
Wang
X J
XJ
Jin
R R
RR
Wu
H
H
Wu
J J
JJ
He
W D
WD
Yao
Y H
YH
Li
D000293:Adolescent; D000328:Adult; D000368:Aged; D058109:Airway Management / Q000379:methods; D000768:Anesthesia, General; D005260:Female; D006801:Humans; D007442:Intubation, Intratracheal / Q000379:methods*; D007828:Laryngoscopy / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011300:Preoperative Care / Q000379:methods*; D011446:Prospective Studies; D012307:Risk Factors; D013957:Thyroid Cartilage / Q000473:pathology*