Point-of-Care Ultrasound-Based Tongue Thickness for Predicting Difficult Laryngoscopy: Comparison with the Modified Mallampati Score

Before a patient goes under for surgery, anesthesiologists face a critical task: ensuring they can safely open the airway to breathe. This process often involves a procedure called laryngoscopy, where a doctor uses a specialized tool to look down the throat and guide a breathing tube into place. Sometimes, the view is clear and easy, but other times, the anatomy makes it difficult to see the opening to the windpipe. If a doctor cannot see clearly, it can lead to multiple attempts to insert the tube, which risks injury or a lack of oxygen. To prevent this, doctors routinely check a patient's mouth and throat before surgery. One common method is the Modified Mallampati Score, a simple visual test where the patient opens their mouth and sticks out their tongue. The doctor assigns a class from one to four based on what structures are visible. While this test is fast and requires no equipment, it relies heavily on the doctor's judgment and the patient's ability to cooperate, and it often misses patients who will turn out to have a difficult airway.

In recent years, doctors have begun using a small, handheld ultrasound machine at the bedside to look inside the body without using radiation. This technology, known as point-of-care ultrasound, allows them to see soft tissues that are hidden from the naked eye. One specific structure that has drawn attention is the tongue itself. The idea is straightforward: if the tongue is physically thicker, it might take up more space in the mouth, making it harder for the doctor to see past it to the windpipe. Researchers wondered if measuring the actual thickness of the tongue with ultrasound could predict a difficult airway better than the traditional visual check. They set out to test this idea in a group of adults scheduled for elective surgery, comparing the new ultrasound method against the standard visual score to see which one was more reliable at spotting trouble before it happened.

The study took place over a year at a teaching hospital, involving 150 adults who were healthy enough to undergo surgery but required a breathing tube. Before the surgery began, a doctor performed the standard visual check, assigning each patient a score based on how much of their throat they could see. Immediately after, a different doctor used the ultrasound probe, placing it gently under the chin of the patient while they lay on their back. The probe sent sound waves to create an image of the tongue, and the doctor measured the vertical distance from the top of the tongue to the skin underneath. This measurement was recorded in centimeters. The doctors who later performed the actual surgery and looked down the throat did not know the results of either the visual check or the ultrasound measurement, ensuring their observations were unbiased. They recorded the quality of the view they saw, categorizing it as either easy or difficult based on a standard grading system.

The results showed that nearly 37 percent of the patients had a difficult view when the doctors looked down their throats. When the researchers compared the two prediction methods, the difference was clear. The traditional visual score correctly identified a difficult airway in only about 56 percent of the cases where it actually occurred. In contrast, the ultrasound measurement of tongue thickness was much better at spotting these difficult cases, correctly identifying them in roughly 78 percent of instances. Both methods were very good at correctly identifying patients who would not have a difficult airway, with accuracy rates above 97 percent for both. However, the ultrasound method caught significantly more of the difficult cases that the visual test missed. The researchers calculated that a tongue thickness of 5.82 centimeters was the best threshold to separate easy from difficult airways in this group. Patients with tongues thicker than this measurement were far more likely to have a difficult view.

The study also looked at whether factors like diabetes, high blood pressure, or gender changed how well the ultrasound worked. The data suggested that the thickness of the tongue remained a strong predictor regardless of these conditions, though the number of patients in each subgroup was too small to be absolutely certain. The researchers emphasized that while the ultrasound method showed great promise and was more sensitive than the standard check, it was not perfect. It still missed about one in five difficult airways, meaning it cannot be used alone to guarantee safety. Instead, the authors suggest that measuring tongue thickness should be added to the existing routine checks to provide a more complete picture. They noted that the specific number they found, 5.82 centimeters, needs to be tested in larger groups of people from different places to confirm it works everywhere. Until then, this new tool offers a helpful, objective way to refine the assessment of airway risk, potentially giving doctors an extra layer of confidence before they begin a surgery.