3-3-2 Rule

The airway is an essential component of the body that requires protection, regardless of the reason for a patient's presence in a hospital, whether it's for outpatient surgery or admission to the intensive care unit (ICU) for observation and therapy. Hence, when contemplating intubation, physicians must carefully assess the potential for intubation failure and strategically optimize various factors to enhance the likelihood of success. Approximately 1%-3% of patients who require endotracheal intubation face challenges due to difficult airways (DAs). Identifying such patients is of utmost importance as it enables clinicians to prepare and mitigate potential complications adequately. The 3-3-2 rule is an assessment tool for predicting difficult intubations (DIs) in the cases of unexpected DAs. According to the American Society of Anesthesiologists, intubation is determined to be difficult to secure when a proficient and skilled anesthesiologist requires more than 3 attempts or exceeds a duration of 10 minutes for successful endotracheal intubation. Likewise, ventilation is considered challenging when a skilled clinician is unable to maintain an oxygen saturation level of above 90% while utilizing a facemask for ventilation, even with a 100% fraction of inspired oxygen (FIO) used for oxygenation. It is essential to manage the airway very promptly, in a very time-sensitive manner, as any delay in adequate oxygenation or ventilation can result in the development of hypoxia and hypercapnic abnormalities, which can be detrimental at the cellular level. Hypoxic brain injury can result in permanent neuronal damage and acidosis due to hypoxia and hypercapnia, which can escalate to cardiac arrest or fatality. Research investigations have examined the correlation between the palpability of the cricothyroid membrane (CTM) and the prediction of DAs based on the 3-3-2 rule. An observational study involved 60 female patients undergoing non-neck surgery, with exclusions made for individuals with neck pathology or a history of neck surgery. The 3-3-2 rule evaluates 3 specific measurements, including the interincisor distance, hyoid-to-mental distance, and thyroid-to-hyoid distance. The study participants were categorized into 2 groups: the non-DA (NDA) and the DA groups. Ultrasonography was used to confirm the accuracy of CTM palpation. The study's findings indicated that the rate of successful CTM palpation was higher in the NDA group than in the DA group. Although there was no significant difference in age between the 2 groups, the DA group had a higher body mass index (BMI). The successful palpation of the CTM was more challenging in patients who exhibited a positive 3-3-2 rule. This result suggests that airway prediction tools, such as the 3-3-2 rule, could play a crucial role in identifying the CTM, ultimately enhancing safety measures for surgical patients. Research studies have examined the relationship between specific patient characteristics and the success rate of CTM palpation, an essential procedure in emergency airway management. It has been observed that patients with shorter interincisor, hyoid-to-mental, or thyroid-to-hyoid distances are at a higher risk of CTM palpation failure. In addition, it was observed that individuals with challenging airway variables often possess a higher BMI. The traditional approach of identifying CTM through palpation between the cricoid and thyroid cartilage has demonstrated imprecise results. Furthermore, factors such as gender, obesity, and neck pathologies can impact the accuracy of CTM palpation. However, despite these complications, it is suggested that weight, height, BMI, neck circumference, and CTM dimensions may not significantly affect the precision of CTM palpation. Ultrasound is emerging as a more accurate diagnostic technique for locating the CTM, particularly in patients with complicated airway anatomy. The 3-3-2 rule, which relies on anatomical information to predict potential challenges in endotracheal intubation, could prove advantageous in identifying the CTM. The findings show promising reproducibility of CTM palpation using the quick, direct palpation method along with the 3-3-2 rule and portable bedside ultrasound equipment.