Overview of Lung Isolation Anesthesia
Lung isolation is a medical technique used to separate one lung from the other. This is done using special airway tools like bronchial blockers or double-lumen endotracheal tubes. Lung isolation is very important when one lung is diseased and needs to be protected from the healthy one. Imagine the scenario where the entire lung needs a thorough cleanse, known as lung lavage. In such cases, we need to prevent any blood or pus from the diseased lung from contaminating the healthy one. This is where lung isolation comes into play.
Moreover, lung isolation allows each lung to breathe independently. This becomes necessary when one lung has a disease that needs different breathing situations compared to the other lung. There’s also a procedure called one-lung ventilation. This is when one lung is made to breathe while the other one is allowed to deflate. This can be helpful in creating a steady environment for surgery and making it easier to access parts inside the chest.
Lung isolation should be carried out by a professional with advanced airway training. This could be an anesthesiologist or an intensivist. They need to have a deep understanding of how lungs work – their physiology – because managing lung isolation can be complex, especially during one-lung ventilation when there’s a risk of low oxygen levels. Lung isolation is used during surgery, so the surgical and anesthesia teams need to communicate clearly to avoid and handle any complications. In an intensive care circumstance, nurses and respiratory therapists should understand the effects of ventilating one or different lungs. They need to watch out for any changes in a patient’s condition that might signal a problem with lung isolation.
Anatomy and Physiology of Lung Isolation Anesthesia
The trachea and the bronchi are key parts of our body’s respiratory system. The trachea, often called the windpipe, is a firm, flexible tube that carries air to the lungs. It’s a bit thicker in men (between 15 to 25 millimeters wide) than in women (10 to 21 millimeters). The trachea has visible lines, or rings, around it made of cartilage, which make it easier for doctors to navigate during procedures like bronchoscopy. The trachea eventually divides into two tubes, the left and right mainstem bronchi, which lead to the left and right lungs respectively.
The bronchi then further subdivide into smaller airways called lobar and segmental bronchial segments. On the right side, there are three lobar bronchi (upper, middle, and lower), whereas, on the left side, there are two (upper and lower). Properly identifying these during bronchoscopy procedures is essential for doctors to safely insert tubes or bronchial blockers. Other anatomical variations of the bronchi exist, albeit these are less common. For instance, some people have an additional branch from the right bronchus, called the accessory cardiac bronchus. This branch is usually nonfunctional and is found in around 0.08% of people.
Another rare abnormality is the presence of a tracheal bronchus. The tracheal bronchus is an extra branch that comes off the trachea. It’s found on the left in around 0.3% to 1% of people and on the right in about 0.1% to 2% of people. Most tracheal bronchi originate close to where the trachea divides into the left and right bronchi. These bronchial abnormalities can complicate lung isolation during bronchoscopy by making it difficult to ventilate the lungs correctly or causing hypoxia, which is a deficiency in oxygen.
Normally, both lungs receive air and blood flow equally. However, during certain procedures like one-lung ventilation, only one lung is ventilated, which can potentially lead to oxygen deficiency due to abnormal blood flow. However, the body has various mechanisms to deal with this, like restricting blood flow to those areas that have reduced oxygen supply and directing it instead towards those with ample oxygen.
Why do People Need Lung Isolation Anesthesia
There are different reasons why doctors may need to perform lung isolation, which is a medical procedure that isolates one lung from the other. These reasons can be surgical or non-surgical, and they can be categorized as either absolute or relative based on their level of urgency or importance. Lung isolation plays a critical role in procedures which require access to certain body structures near the chest. Furthermore, it might be needed to manage severe conditions affecting just one lung. This can be achieved through one lung ventilation or different rates of ventilation for each lung. For instance, if there’s a severe infection in one lung, lung isolation can help avoid contaminating the healthy lung. In some cases, the lungs might need to be separated physiologically to apply different breathing parameters on each side.
Situations where lung isolation might be required for surgery could include:
1. In operations related to the chest, such as:
– Lung removal
– Procedures using a small video camera inserted through the chest wall (video-assisted thoracoscopic surgery)
– Lung transplants
– Fixing a hole in the diaphragm (the muscle that helps you breathe)
– Treatment or removal of lung lining (pleurodesis or pleurectomy)
– Removal of part of the food pipe (esophagectomy)
2. In heart-related surgeries, such as:
– Less invasive heart surgeries
– Removal of the sac around the heart (pericardiectomy)
– Procedures on the main artery in your chest (thoracic aorta)
3. In nerve-related surgeries, such as:
– Removal of nerves to reduce excessive sweating (thoracic sympathectomy)
– Operations relating to the spine in your chest area
Conditions where lung isolation might be required due to disease in one lung include:
1. Conditions requiring physical separation of the lungs. These could include:
– Conditions requiring washing out the whole lung (like pulmonary alveolar proteinosis, a condition where a certain type of protein builds up in the air sacs, or alveoli, of the lungs)
– Too much secretion, either due to infection or other causes
– Lung hemorrhage (bleeding)
2. Conditions requiring physiological separation of the lungs and different ventilation. These could include:
– Disease or injury to the lung tissue
– Hole between the bronchus (air tube) and the pleura (lung lining)
– After-effects of chest surgeries
– One-sided bronchospasm (tightening of the muscles that line the airways)
When a Person Should Avoid Lung Isolation Anesthesia
There are some situations where isolating the lungs for medical reasons may not be advisable, due to factors related to the procedure itself or the patient’s health condition.
When it comes to procedure-related issues, these can occur when using a double-lumen endotracheal tube, a special tube used to manage airflow during surgery. For instance, inserting and positioning this tube can be challenging or even impossible in patients who have difficult passageways for breathing. Forceful tries can harm the windpipe and if airway access is lost during the process, dangerously low oxygen levels might result. Using this tube in an existing breathing hole or stoma could also wound the airway unintentionally. When using this tube, tumors present inside the airway may get damaged, causing possible bleeding, movement of the tumor to different sites or blockage.
For patient-related considerations, using single-lung ventilation, which means breathing with only one lung when under medical procedure, should only be practiced in patients who can handle the changes it causes to heart and lung functions. Certain patient factors can raise the risk of a severe lack of oxygen, which if sustained, will demand restarting ventilation to both lungs.
Patients with lung diseases that cause low oxygen levels, even when both lungs are working with maximum oxygen supply, may not be able to handle significant periods of breathing with only one lung. The situation can worsen in patients who have had previous surgery on the opposite lobe leading to more than 25% loss of lung function or in morbidly obese patients.
In patients with lung hypertension, oxygen deficiency and accumulation of carbon dioxide can worsen the existing condition. In extreme cases, this might trigger heart failure on the right side and collapse of the circulatory system. A recent study showed that a high rate of minute-long breathing to the amount of carbon dioxide produced, as seen in lung hypertension and differences in oxygen ventilation and blood flow, predicts a lack of oxygen and demands risk assessment.
Surgery on the larger right lung may also heighten the risk of oxygen deficiency when using one-lung ventilation. However, if the lungs are in good health, the risks from hypoxia are typically managed and may not last for long.
Equipment used for Lung Isolation Anesthesia
Sectioning off one part of the lungs, known as lung isolation, is done in certain medical situations. This can be achieved using different types of tubes which can either be a single-lumen, double-lumen, or bronchial blocker. A device called a fiberoptic bronchoscope is usually used to assist in placing these tubes in the right location in the lungs. It’s really important for doctors to get this right, to avoid complications such as the need for removal and reintubation, or problems in advancing the bronchial blockers, which could happen if the bronchoscope is not the right size.
A single-lumen tube can be used to achieve lung isolation. This can be done by advancing the tube into the main airway branches (known as bronchus) of either the left or right lung. This is generally easier to do on the right side, since the main airway of the right lung has a similar direction to the trachea. This method is primarily used in children, whereas double-lumen tubes are not used in very young kids. In emergencies such as sudden lung injury or bleeding in a patient who’s already intubated, a single-lumen tube can be advanced into the right bronchus to achieve lung isolation.
A double-lumen tube is another way to achieve lung isolation. This type of tube allows doctors to ventilate each lung separately, as each lumen (or channel in the tube) can be clamped individually. This is achieved by putting one end of the tube in the mainstem bronchus while the part of the tube called the tracheal lumen faces the other side. Right- and left-sided double-lumen tubes are available, but usually, the left-sided tubes are preferred unless the procedure involves the left main bronchus, which would prevent a left-sided tube from being inserted.
To help the doctor know which part of the tube goes where, the tubes are usually color-coded. For example, blue is universally used to denote the endobronchial-lumen cuff, which is a small balloon-like part of the tube that helps to seal off the lung. To ensure proper placement and to avoid complications, the position of the tube is confirmed after the patient is in their final position for the procedure.
Bronchial blockers are another method of achieving lung isolation. These devices consist of an inflatable balloon at the end, and can be inserted into one of the main airways under the guide of a fiberoptic bronchoscope. They can even be advanced further down the path of the airway to isolate a specific section of the lung.
The choice of the method of lung isolation often depends on the condition of the patient and the requirements of the surgical procedure. For instance, in the case of spreading lung infection, a double-lumen tube is usually utilized as it is less likely to be dislodged and also allows for cleaning of the diseased lung, which isn’t possible with a bronchial blocker. However, each method of isolation has its benefits, and studies have shown that both types of tubes can achieve sufficient lung isolation without a significant difference in complications.
For cases where the patient already has a tracheostomy (which is a surgical procedure to create an opening in the neck for direct access to the trachea), lung isolation can pose a challenge. There are different ways to handle this, but using a cuffed tracheostomy tube as a bronchial blocker is often preferred due to its simplicity and lower risk of causing additional airway injury.
Who is needed to perform Lung Isolation Anesthesia?
Anesthesiologists, or the doctors responsible for putting patients to sleep during surgeries, usually learn to place special tubes (double-lumen endotracheal tubes and bronchial blockers) in patients’ airways during their residency training. This is typically done under the guidance of more experienced doctors. Nowadays, training tools called simulators are also used. These allow the doctors in training to practice advanced airway techniques, like using fiberoptic bronchoscopy (a small tube with a light and camera) in a less stressful setting than an actual operation room.
The regulations from the Accreditation Council for Graduate Medical Education (ACGME) state that these doctors need to participate in 20 non-heart cases inside the chest, but there is no specific rule saying they must practice lung isolation, a technique used in some surgeries to only ventilate one of the patient’s lungs.
However, since beginners in this field who try to carry out lung isolation might face a higher likelihood of incorrectly positioning the tube or causing other complications, regular practice models can be helpful for new doctors to start learning and retain their skills. A recent study found that beginners could achieve a good level of proficiency in carrying out these procedures on dummies, using either video lessons or a simulator, after 90 minutes of training. This study also discovered that this skill might fade if not practiced regularly, two months post-training, highlighting the importance of continuous practice in keeping up lung isolation skills.
Preparing for Lung Isolation Anesthesia
People who are about to undergo a procedure that requires them to breathe with one lung often have some kind of lung disease. It’s important that these patients are thoroughly checked for any issues with their lungs before the surgery. This can include checking their heart function using an ultrasound and studying their lung images (from x-rays or scans) to plan for the surgery.
If a patient has issues in their lung like fluid buildup, atelectasis (lung collapse), or consolidation (part of the lung is filled with liquid instead of air), they might have problems getting enough oxygen during the surgery. If there are any bulges in the non-surgical lung, this raises the risk of a pneumothorax (the lung collapsing) during or after the surgery.
It’s important to check for any abnormal symptoms related to tumors as these can change the plan for anesthesia (the drugs that make the patient unconscious during surgery). It’s shown that following specific protocols can help avoid problems during single-lung surgery.
Older patients or patients having a part of their lung removed should be carefully checked as they are more likely to have complications. There are two important tests for this: the FEV1 test, which measures how much air a person can force out of their lungs in one second, and the DLCO test, which measures how well the lungs transfer oxygen to the bloodstream. A low score on either of these tests can predict complications after surgery.
The American College of Chest Physicians suggests that doctors estimate the post-surgery results using these tests:
– If results show that FEV1 or DLCO are predicted to be above 60%, then no further testing is needed
– If either FEV1 or DLCO are predicted to be between 30% and 60%, patients must do extra tests like climbing stairs or a shuttle walk test.
– If both FEV1 and DLCO are predicted to be less than 30%, patients must do a test that measures their maximum oxygen intake during intense exercise.
In preparation for the surgery, the equipment needed to place a double-lumen endotracheal tube (a tube that goes into the windpipe to allow airflow to each lung) should be ready. The size of the tube should fit the patient perfectly, taking into account their gender, height, and the size of their windpipe and bronchi. An over-sized tube can cause problems during surgery.
In an emergency situation where a patient is bleeding heavily from one lung, the priority is to quickly isolate that lung. In these situations, especially if the patient is far from the operating room, it might be faster to insert a single-lumen tube into the healthy bronchus (the tube through which air enters and exits the lung) to isolate that lung. This is super important to avoid any complications during the surgery and for a better recovery.
How is Lung Isolation Anesthesia performed
Placing a double lumen endotracheal tube (a special tube allowing healthcare providers to control the flow of air and oxygen) in a patient involves a careful process usually performed under direct laryngoscopy, where the throat is visually examined with a lighted instrument. In specific situations, this procedure is done with the help of a fiberoptic bronchoscopy or video laryngoscopy. These are tools that provide a more in-depth view of the throat and lungs. However, bear in mind, working with a video laryngoscope might be more difficult due to less maneuvering room in the patient’s throat.
Once the tube is introduced and past the vocal cords, the rigid stylet (a slim medical instrument) is removed. The tube is then slowly turned and advanced in either a clockwise or counterclockwise manner, depending on which lung it is being directed towards until it meets resistance.
Afterward, the cuffs on the tube are inflated to ensure a sealed and secure fit, the connector is attached, and ventilation (breathing assistance) is started. Medical personnel will then watch for the chest rising equally on both sides (indicating successful ventilation) and listen to the breath sounds in your lungs. This is done by clamping different parts of the tube, to ensure that it is positioned correctly and air is going to the right places.
Fiberoptic bronchoscopy is typically preferred to double-check the placement of the tube. This test can confirm that everything is in the right position and the cuff of the tube is not pushing against something it shouldn’t, a problem you wouldn’t be able to detect just by listening. Sometimes, some healthcare providers use a fiberoptic bronchoscope to guide the tube into the right place from the very beginning, but this usually requires two healthcare providers.
If there are difficulties with inserting the double lumen endotracheal tube, another approach involves using a simpler single-lumen tube at first. A long device known as an exchanger is then used to switch out the single tube for the double-lumen one. This tube exchanger can also be connected to an oxygen source or used to provide a path for the fiberoptic bronchoscope.
A different tool, called a bronchial blocker, can be used when more precise control is required for blocking air or gas from reaching specific parts of the lung. The particular method for placement of a bronchial blocker varies depending on the exact design of the blocker. Some of them are wire-guided, meaning they can be guided into the desired location like threading a needle. Others have an incorporated stylet that is placed through a standard single-lumen tube, giving good control and allowing easy direction into a specific bronchus.
Some bronchial blockers have a unique dual-balloon tip allowing them to seal off both left and right bronchi for lung isolation. Selecting the right kind of blocker and technique depends on the needs and circumstances of the patient. For instance, in pediatric patients, placing the bronchial blockers outside of the endotracheal tube rather than inside could be beneficial.
Possible Complications of Lung Isolation Anesthesia
There can be some complications related to the structures in our body (anatomical complications) when a double-lumen tube – a tube with two openings – is used. Because of its size, it can cause harm to the voice box (larynx), windpipe (trachea), or the branches of the windpipe (bronchi). Although rare, if the tube causes a tear or rupture in these areas, it can be very serious. Some groups of people like women, older adults, smaller individuals, people on steroids and those with certain windpipe conditions are more likely to face these complications. Therefore, having a sore throat or a hoarse voice is more likely after using a double-lumen tube, compared to other methods like bronchial blockers.
There can also be complications related to how our body functions (physiological complications) when using a method called single-lung ventilation. In this method, one lung is put off while the other one continues to function. However, the circulation of blood with oxygen (perfusion) still continues in the non-working lung, which is not ideal, as this causes some misuse of the oxygen supply leading to a “waste” perfusion. There are mechanisms like hypoxic pulmonary vasoconstriction that can protect against lack of oxygen to some extent. But the doctor performing the procedure has to watch out for and manage low oxygen levels that might occur during the procedure. The balance between airflow in and out of the lungs and circulation of blood (V/Q matching) greatly influences oxygen levels in such cases.
While doing single-lung ventilation, doctors might use more percentage of oxygen in the inhaled air to maintain a safety margin; this can also help broaden blood vessels, which could improve the blood flow to the working lung. However, using 100% oxygen can lead to lung tissue collapse (atelectasis), so doctors start with less than 100% oxygen and increase it if needed.
If oxygen levels drop while doing single-lung ventilation, doctors take the following steps:
1. They double-check the position of the double-lumen tube. They may also remove secretions that may contribute to low oxygen levels.
2. They increase the amount of oxygen delivered.
3. They use special techniques on the working lung to overcome any lung tissue collapse, apply positive pressure at the end of oxygen exhale (PEEP) to prevent atelectasis, and improve the oxygen level.
Applying continuous pressure to the non-working lung can also improve oxygen levels. However, this can make the surgery difficult and is done only when other methods have failed.
If, despite the above steps, the lack of oxygen becomes severe, the doctor might have to allow both lungs to work again. This severe low oxygen level should be a cue to look for other serious issues like a collapsed lung. People with chronic obstructive pulmonary disease (COPD) are more likely to face this situation, which requires stopping the surgery and immediate placement of a chest tube on the side of the collapsed lung. Using standard protocols can help in sticking to strategies that protect the lung.
What Else Should I Know About Lung Isolation Anesthesia?
In some medical settings, a patient may need to utilize only one lung for breathing. This can occur during specific surgeries or due to certain conditions where it’s beneficial to keep one lung nonactive. But, when this happens, it creates a sort of ‘shortcut’ for blood flow.
How does it work? Blood continues to flow through both lungs, but one is not contributing to oxygenating the blood. Because of this mix of oxygen-rich and oxygen-poor blood, the body’s overall oxygen level may drop. To counteract this, your body uses a mechanism called ‘Hypoxic Pulmonary Vasoconstriction’. This is when your lung blood vessels tighten up or constrict due to low oxygen levels. This response can decrease blood flow to the non-ventilated lung by almost 50%, reducing the drop in the body’s oxygen level.
Naturally, it does take time for this full effect to kick in – usually achieved after about two hours of using only one lung for ventilation. This lag can result in lower oxygen levels shortly after moving to one-lung operation. Certain factors, such as low carbon dioxide levels or low body temperature, may also interfere with this constriction mechanism and cause more oxygen loss.
The pressure of blood flow also shifts depending on the patient’s position. If patients lie on their side during surgery, gravity can help by directing more blood flow to the active lung, improving oxygen levels. In contrast, if the patient needs to lie flat or need to prop up the ‘unhealthy’ lung, it can lead to less optimal oxygen levels.
In the same way, managing the ventilator during this one-lung isolation is crucial to prevent lung damage and possible complications. Certain techniques like applying low amounts of pressure to pump less air (low tidal volumes), using pressure control settings, or using periodic high pressure inflations (recruitment maneuvers) can help protect the lung and increase oxygen level.
The ventilator settings should be personalized for each patient. For instance, the optimal oxygen level for most patients is between 88% and 95%. If a person shows lower oxygen levels during one-lung ventilation, the medical team should be alerted, and steps should be taken to check the airway device’s placement or adjustments in ventilator settings.
In summary, one-lung ventilation necessitates a balance between assuring enough oxygen supply to the body while protecting the lung from unnecessary strain or damage. Regular checks by the surgical team and medical staff help ensure optimal patient care in such cases.
