Overview of Airway Monitoring
Checking a patient’s breathing or ‘airway monitoring’ is an important part of a full physical check-up. This helps the doctor understand how well a patient’s body is moving air in and out (ventilation) and how well the body is able to exchange gases like oxygen and carbon dioxide. During this test, the doctor looks at the condition of the patient’s airways and also uses extra devices to gather more data.
Even though this check-up is crucial for patient care, the doctor must be careful when interpreting information from the devices used. This is because these devices may have limitations and may not always provide complete information. This review takes a look at different methods for monitoring a patient’s airways, what these methods do, and what their limits might be.
Anatomy and Physiology of Airway Monitoring
When a doctor is looking after a patient who is having breathing trouble, they collect both personal and observable information. They check the patient’s ability to protect their own airway by using their personal medical history and completing a physical examination. It’s important for the doctor to understand the anatomy of the airway, which is split into two parts: the upper airway, including the nasal cavity, throat, and voice box, and the lower airway, which begins at the windpipe and extends to the lungs.
During an airway examination, the doctor will look at the patient’s ability to open their mouth, the state of their teeth, the size of their neck, the distance between their thyroid and jaw, their Mallampati score (a way to predict if putting a breathing tube might be difficult), and the flexibility of their head and neck. A helpful acronym used to remember these steps is “LEMON”: Look, Evaluate, Mallampati scoring, Obstruction check, and Neck mobility assessment.
Doctors prepare for a potentially difficult airway when patients have a hard time opening their mouth, have a large neck, a shorter distance between thyroid and jaw, a Mallampati score of 3 or 4, or a limited head and neck movement.
Different tests can be used to examine the airway, but their accuracy can vary. Some of these common tests include:
1. Mallampati Test: This simple, harmless test helps predict if putting a breathing tube might be tough by looking at the back of the throat. Its accuracy varies, predicting correctly from 24% to 62% of the time.
2. Thyromental Distance: This test measures the space between the thyroid notch and the lower jaw. A shorter gap suggests a difficult airway with an accuracy of 44%-55% and a specificity of 85% to 89%.
3. Sternomental Distance: This measures the distance between the sternum (center of chest) and the mentum (point of the chin). A shorter distance can suggest a difficult airway; the test correctly predicts this from 50% to 62% of the time.
4. Inter-incisor Gap: This is the distance between upper and lower front teeth when the mouth is fully open. A smaller gap suggests a difficult airway; the test correctly predicts this from 29% to 61% of the time.
5. Neck Mobility: Head and neck movement limitations can cause difficulty managing the airway; the test detects such conditions from 29% to 54% of the time.
6. Upper Lip Bite Test: Here, the patient is asked to bite their upper lip with their lower front teeth; the test correctly predicts difficulty from 68% to 93% of the time.
An ultrasound of the airway can also help predict if a patient’s intubation may be challenging. The most accurate sign that placing a breathing tube may be difficult is if the distance between the upper and lower front teeth is less than 3 cm. When the tube is inserted, things like mist in the tube, the chest rising with each breath, and hearing breath sounds on both sides suggest successful insertion. Although a chest x-ray can help see the placement, it’s not absolutely necessary. Clinical observation is more often recommended.
Aside from the Lemon evaluation, the doctor also looks out for how alert the patient is, their breathing rate, their oxygen level and whether the muscles required for breathing are overused. Listening to the breathing can help identify issues such as wheezing, a high-pitched sound when breathing, crackling sounds, or reduced breathing sounds.
Why do People Need Airway Monitoring
Devices that monitor your breathing are crucial in understanding your health condition and what medical care you require. Certain symptoms may suggest that you need a procedure known as endotracheal intubation to secure your airway. These symptoms include problems speaking, sitting in a hunched over position, drooling, struggling to breathe, nose flaring, rapid breathing, a drop in mental clarity, skin turning a bluish color, and needing more oxygen.
Finding out a full medical history and performing a physical examination
can be difficult with patients who are unresponsive or children. In situations like these, medical professionals need to use different methods to examine the patient’s airway. Checking vital signs and carrying out lab tests can provide important information and help identify possible breathing failure.
While a test analyzing the gas in your arteries can be trusted, it is an invasive procedure. Relying only on physical examination findings, like the sounds of your breath, may not accurately confirm the need for endotracheal intubation in patients with pre-existing lung conditions. To be sure that the endotracheal tube (a breathing tube placed in your airway) is in the right spot, the most reliable method is using a technique called waveform capnography.
Equipment used for Airway Monitoring
Capnography is a technique that helps observe a patient’s breathing, ideal for both those who can breathe naturally and those who are mechanically ventilated. It measures how much carbon dioxide is expelled from the body during each breath, providing a concentration value. We can analyze the results visually through a waveform (shape of the data over time) or by specific number values, better known as alveolar end-tidal carbon dioxide (ETCO2).
Waveform capnography offers insights into how air is flowing through your lungs. It shows four phases: the start of a breath without air in the lungs (inspiratory baseline), the start of exhaling (expiratory upstroke), the steady exhalation (expiratory plateau), and the start of another breath (inspiratory downstroke). Changes in these phases can indicate potential issues.
For instance, high levels of ETCO2 could suggest several problems like difficulty in breathing, ineffective ventilation, certain life-threatening conditions such as blood infection (sepsis) or abnormal body temperature regulation (malignant hyperthermia), and other medical interactions. Low levels can point to hyperventilation, low body temperature, or critical conditions like pulmonary embolism or cardiac arrest, among others. Changes in the waveform can indicate blockage in the airways, a common occurrence with conditions like asthma, chronic obstructive pulmonary disease (COPD), or during pregnancy. The capnography tool is crucial for patients with tubes in their windpipe to help them breathe, as the information it provides is critical for their proper ventilation.
Capnography does, however, have some limitations. If the patient is not fitted with a proper, secure breathing tube, it might not be as effective. Also, things like recent intake of a bicarbonate solution or a fizzy drink could alter the ETCO2 readings. It’s less useful when the patient doesn’t have a pulse because it needs the heart to be functioning properly, yet it can guide heart massage therapy where a sudden rise in ETCO2 could suggest return of heart function.
Another monitoring tool, the pulse oximeter, continually measures the amount of oxygen in the blood and the heart rate. It works by using light of different wavelengths. The absorption of this light can tell us how much oxygen is binding to our red blood cells. While being very handy, it also has limitations, such as inaccuracies due to certain conditions like carbon monoxide poisoning, severe lack of oxygen, severe cold or low blood flow, or even due to practical issues like dark nail polish or excessive movement.
Capnography has been further developed and has proved its worth in various clinical settings, like when you’re sedated for a procedure, in early detection of respiratory failure, and even to prevent events caused by lack of oxygen or inadequate respiration. Recent technology advancements have led to new capnography devices that are portable, easy-to-use, and more versatile, allowing for widespread use in multiple clinical scenarios.
Airway monitors are crucial in identifying the need for airway management. When a patient is uncommunicative due to unconsciousness or age, alternatives like imaging methods (such as chest x-ray or ultrasound) could help in checking the lungs and airways. Monitoring tools that track a patient’s breath and advanced ventilators also help in assessing the patient’s respiratory condition. Techniques like electric impedance tomography (a method to measure regional lung ventilation and blood flow) can provide more detailed information about a patient’s airway health.
In conclusion, capnography is a valuable method for monitoring breathing in patients. It provides realtime insights into a patient’s breathing situation, making it a vital tool in various clinical settings. Although it has limits, recent tech advancements have expanded its uses and improved its practicality. Both capnography and pulse oximetry can provide important information to guide doctors in their actions.
Who is needed to perform Airway Monitoring?
Everyone taking care of a patient should know how to spot the signs of breathing problems. If these signs are noticed, they need to quickly consult with a medical expert who knows a lot about handling breathing problems. This expert will then first thoroughly evaluate the patient’s condition. In cases where it’s expected that managing the patient’s breathing might be challenging, it’s a good idea to have a special tool called a video-assisted laryngoscope on standby. This tool helps doctors to see your throat better during check-ups or procedures. Moreover, all patients who might have difficulty being put on a ventilator or having a breathing tube placed, should be assessed according to a set guide known as a ‘difficult airway algorithm’. This guide helps in providing appropriate breathing support and care.
How is Airway Monitoring performed
Understanding transpulmonary pressure is key to checking the stress levels in the lungs. This is a key sign of how the lungs are functioning and the pressure inside the tiny air sacs in the lungs known as alveoli. Air pressure in the esophagus, the tube that connects your throat to your stomach, is measured via a technique known as esophageal manometry. This technique uses special balloon catheters – flexible tubes with small inflatable balloons at the end. It’s important to make sure these balloons are properly calibrated or adjusted to measure correctly. Esophageal manometry has many uses, including checking how flexible the lungs and chest wall are, estimating the amount of effort needed to wean a patient off a ventilator, spotting any blockages in the upper airways post-extubation (once the breathing tube has been removed), and identifying any issues with the synchronicity between the patient and the ventilator.
Several studies have suggested that monitoring during surgery can reduce the risk of leftover neuromuscular block (when muscles are purposely paralyzed during surgery) and improve patient’s breathing after the surgery by minimizing any negative effects. This is why many international societies that focus on anesthesia recommend using this method of monitoring when using neuromuscular blocking agents in surgical settings.
Capnography is a highly useful tool for patient monitoring. It measures the amount of carbon dioxide (CO2) a patient exhales, in real time. This is especially important during anesthesia, in the emergency room, and in intensive care units. This technology has many uses, such as checking if a breathing tube has been placed correctly, assessing how severe a disease is and how a patient is responding to treatment, and monitoring sleep apnea in non-hospital settings. With the advent of smaller sensors, this tool can be used in various settings including in the field for first responders, and in military planes.
In cases of a difficult airway, nerve blocks (where specific nerves are numbed) can be highly beneficial for a procedure known as awake tracheal intubation (ATI), which is when a doctor inserts a tube into a patient’s trachea, or windpipe, while the patient is awake. These nerve blocks significantly speed up the intubation process, improve the quality of anesthesia, and reduce overall complications. Overall, nerve blocks provide superior anesthesia quality for ATI, thereby improving the conditions for intubating and improving patient satisfaction and reducing complications.
Different types of surgery need specific ventilation techniques and they come with challenges. For example, laparoscopic surgery (where the surgeon operates through tiny holes in the abdomen) often requires a pneumoperitoneum, or inflatable space in the abdomen, which can decrease lung flexibility and increase breathing pressures due to the diaphragm moving upwards. Though laying a patient on their front can help their respiratory system, it requires careful management of the airway to prevent disconnection of the endotracheal tube. Those undergoing lung surgery often need to only use one lung during surgery, and it’s very important to protect the lung and ensure adequate oxygen and carbon dioxide exchange. Jet ventilation is a special technique that can be used in certain procedures, but it needs careful consideration to make sure airway pressures are correct and gas exchange is sufficient. Understanding these various ventilation strategies across different surgeries can improve patient care and outcomes.
What Else Should I Know About Airway Monitoring?
Keeping a close eye on a patient’s breathing tube involves looking at a variety of factors. The breathing machine shows how a patient’s lungs are expanding and contracting, and can pinpoint any sudden changes. Medical images, like x-rays, can be used to spot developing lung problems or issues with the diaphragm, a muscle that helps you breathe. When a patient is being prepared to stop using the breathing machine, it’s very important to check their airway to ensure they can still breathe and protect their lungs on their own. There are certain guidelines that need to be followed to make it safe to remove the breathing tube and help avoid the need to put it back in.