Endotracheal intubation is a procedure used to secure the airway in patients who are unable to breathe adequately on their own. It is commonly performed in emergency, surgical, and intensive care settings to ensure airway patency and allow for effective oxygenation and ventilation. Whenever there is a concern for a patient’s ability to breathe properly on their own, intubation is considered to prevent airway collapse. Intubation is also a helpful option for elderly or frail patients who are at risk of aspirating (accidentally inhaling) food, water, or regurgitated contents. Over time, clinicians have refined the process of intubation to increase speed and decrease the risk of complications.
Successful intubation requires thorough preparation and adherence to a structured approach. The process of intubation begins with an assessment of the airway for potential difficulties, often using the LEMON assessment mnemonic (Look, Evaluate the 3-3-2 rule, Mallampati scoring, Obstruction, Neck mobility). The 3-3-2 rule measures inter-incisor distance, hyoid-to-mental distance, and thyroid-to-hyoid distance using a clinician’s finger width. The Mallampati score is a four-point scale assessing the ease with which a skilled clinician can introduce an ETT to the respiratory tract. Patients with a greater degree of anatomic airway obstruction receive higher scores. Additional preprocedural assessments include atlantooccipital extension, mandibular spacing, the warning sign of Delikan (upper lip bite test), and the prayer sign. These exams in the context of a patient’s BMI help clinicians anticipate an easy or difficult intubation process.
Specialized equipment is necessary to complete intubation including a laryngoscope, endotracheal tube (ETT), stylet, suction device, and bag-valve-mask. To begin the procedure, patients must be pre-oxygenated with a 100% oxygen face mask. This increases the level of oxygen in the patient’s blood, allowing their vital organs to remain fully nourished while the intubation procedure is under way. Once adequately pre-oxygenated, an average healthy adult can avoid hypoxic injury for 8-10 minutes before requiring more oxygen (Azam Danish 2021). This gives clinicians ample time to visualize the trachea, insert the ETT, check for proper placement, and start the ventilator. While pre-oxygenation is underway, the patient is sedated and often given a neuromuscular blocking agent to prevent the patient from moving, gagging, and breathing throughout the intubation process.
After adequate pre-oxygenation, indicated by an end-tidal oxygen level above 90%, the ETT must be introduced. Currently, orotracheal intubation using video laryngoscopy is widely used and preferred, but skilled anesthesiologists are also capable of intubating using direct laryngoscopy, which does not have video assistance. During this step, the clinician attempts to visualize the patient’s vocal cords. Next, the ETT is guided through the glottis and into the trachea (windpipe). Clinicians pay close attention to ensure that the ETT has not entered the esophagus, which would inappropriately send oxygen to the stomach rather than the lungs. Proper placement of the ETT is confirmed through chest auscultation, capnography (presence of exhaled CO₂), and chest X-ray if necessary. Once proper placement is confirmed patients are monitored with arterial blood gas, pulse oximetry, and ventilator read-outs.
While the process of intubation is facilitated by clear guidelines and technological advancements, it carries potential complications and variability. These include dental trauma, hypoxia, esophageal intubation, aspiration, and hemodynamic instability. Difficult or failed intubation may result in airway compromise and necessitate alternative techniques such as surgical airway access. Additionally, these risks increase in patients who fall outside of average metrics of good health (elderly, obese, diabetic, etc.). With proper preparation and technique, intubation is a highly effective way to support breathing in most patients. While it is not without risks, advances in airway assessment tools, training, and technology have made the procedure safer and more reliable in both emergency and surgical settings.
References
Azam Danish M. Preoxygenation and Anesthesia: A Detailed Review. Cureus. 2021;13(2):e13240. Published 2021 Feb 9. doi:10.7759/cureus.13240
Hendrix JM, Patel R, Friede R. 3-3-2 Rule. [Updated 2023 Aug 17]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK493235/
Mahmoodpoor A, Soleimanpour H, Nia KS, Panahi JR, Afhami M, Golzari SE, Majani K. Sensitivity of palm print, modified mallampati score and 3-3-2 rule in prediction of difficult intubation. Int J Prev Med. 2013 Sep;4(9):1063-9.
