Continuing Education Activity
Lung isolation involves utilizing bronchial barrier devices to separate the lungs enabling each lung to function as a separate unit. Lung isolation is used to facilitate surgical exposure during specific intrathoracic procedures or assist in the management of certain pulmonary conditions. This activity describes technical and physiologic principles relevant to lung isolation and the role of an interprofessional team, including anesthesiologists, thoracic surgeons, and operating room (OR) nurses involved in managing these patients.
- Identify the relative and absolute indications for lung isolation.
- Describe the techniques used for achieving lung isolation.
- Summarize the potential complications of lung isolation.
- Explain the importance of effective collaboration and communication between interprofessional team members caring for a patient requiring lung isolation.
Lung isolation describes either anatomic or physiologic separation of one lung from the other using an advanced airway device, typically a bronchial blocker (BB) or double-lumen endotracheal tube (DLT). Anatomical lung isolation separates a diseased lung and prevents it from contaminating the healthy lung. For example, in the case of whole lung lavage, anatomical lung isolation is used to avoid spillage of blood or pus from the diseased lung to the healthy lung. Physiological lung separation ventilates each lung as an independent unit and may be indicated when unilateral lung pathology requires differential ventilatory parameters for each lung. One-lung ventilation (OLV) is the ability to ventilate one lung while allowing the other to collapse either to facilitate surgical exposure or to manage individual disease states. The deflation of one lung can establish an immobile surgical field and create space within the thorax, allowing access to anatomical structures.
A practitioner with advanced airway training (i.e., anesthesiologist or intensivist) should place the DLT or BB. Extensive knowledge of pulmonary physiology is essential for managing lung isolation, particularly during periods of OLV, which can often be complicated by hypoxia. When used to facilitate surgery, lung isolation requires clear communication between the surgical and anesthesiology teams to prevent and manage complications. In the intensive care setting, nurses and respiratory therapists must be aware of the physiologic consequences of differential or one-lung ventilation and detect changes in the patient's condition that may indicate a problem with lung isolation.
Anatomy and Physiology
Comprehensive knowledge of normal and abnormal tracheal and bronchial anatomy is of utmost importance. The trachea is a fibromuscular tube with an internal diameter ranging from 15 to 25 mm in men and 10 to 21 mm in women. It is supported anteriorly by 16 to 20 incomplete cartilaginous rings and posteriorly by a strip of longitudinal smooth-muscle. These landmarks aid in orientation during bronchoscopy. The trachea divides sharply at the carina to give rise to the right and left mainstem bronchi. Because the right mainstem trajectory closely parallels that of the trachea, right mainstem intubation is common when an endotracheal tube is inserted blindly beyond the carina.
Beyond the mainstem bronchi, the airway divides further into (secondary) lobar and (tertiary) segmental bronchial segments. There are three lobar bronchi on the right (upper, middle, and lower) and two on the left (upper and lower). Differentiating the left and right mainstem bronchi using bronchoscopy is critical to ensure the correct placement of DLTs or BBs. The right upper lobar bronchus takes off approximately 15 to 20 mm from the carina. By comparison, the left mainstem bronchus does not divide into its upper and lower lobar segments until 45-50 mm beyond the carina. Its characteristic trifurcation can further distinguish the opening of the right upper lobe into its apical, posterior, and anterior segments, such that it resembles a cloverleaf. However, it is essential to recognize that variations of this classic description are common. Approximately 22% of individuals do not have an apical segmental bronchus of the right upper lobe resulting in the observation of a bifurcation rather than a trifurcation on bronchoscopy.
An accessory cardiac bronchus is present in approximately 0.08% of individuals and appears as an additional branch of the right mainstem typically opposite the right upper lobe bronchus. The cardiac bronchus is usually nonfunctional, petering out into rudimentary bronchioles. Although generally asymptomatic, retained secretions in a cardiac bronchus may become a nidus for infection in certain circumstances. While usually clinically silent, variations in bronchial anatomy can complicate lung isolation techniques, either by leading to disorientation during bronchoscopy or inadequate ventilation.
Another somewhat more common abnormality that may complicate lung isolation is the presence of a tracheal bronchus. A left-sided tracheal bronchus is present in approximately 0.3% to 1% of the population, while a right-sided tracheal bronchus is present in 0.1% to 2%. The majority of these abnormal tracheal bronchi branch within 2cm of the carina, but some may branch 6cm or more proximally. Tracheal bronchi may be displaced or supernumerary, but it is more common for them to be displaced. About 0.2% of the human population has a right upper lobe bronchus originating directly from the trachea; a configuration referred to as a pig bronchus because it resembles the typical anatomical arrangement in swine. Tracheal bronchi can complicate lung isolation by preventing the total collapse of an operative lung or resulting in hypoxia due to the inadequate ventilation of the tracheal bronchus. For example, if a left-sided DLT is placed in a patient with a pig bronchus for a left-sided surgery, the right-sided tracheal bronchus will not be ventilated if it is located either under or proximal to the tracheal cuff of the DLT. Although uncommon, this could be considered a potential cause of unanticipated hypoxia during OLV. Conversely, if a BB is positioned in the right mainstem in a patient with an unrecognized pig bronchus, right lung deflation will be inadequate due to continued ventilation of the right upper lobe.
There are surgical and non-surgical indications for lung isolation, which can be absolute or relative. OLV can facilitate a variety of surgical procedures involving thoracic approaches to anatomical structures. The management of severe unilateral lung disease with either differential ventilation or OLV can also necessitate lung isolation. Some of these disease states, such as severe unilateral infection, require a definitive anatomical separation of the lungs to prevent contamination of the non-diseased lung. Other disease states only need physiologic separation to enable different ventilatory parameters to be used on each side.
Surgical Indications for Lung Isolation and OLV
- Lung resection
- Video-assisted thoracoscopic surgery
- Lung transplantation
- Thoracic diaphragmatic hernia repair
- Pleurodesis or pleurectomy
- Minimally invasive cardiac surgery
- Surgeries involving the thoracic aorta
- Thoracic sympathectomy
- Anterior approach to the thoracic spine
Pathological Indications for Lung Isolation
Unilateral disease states requiring anatomical lung isolation
- Pathology requiring whole lung lavage, e.g., pulmonary alveolar proteinosis
- Excessive infectious or non-infectious secretions
- Pulmonary hemorrhage
Unilateral disease states requiring physiologic lung isolation and differential ventilation
- Parenchymal disease or injury
- Bronchopleural fistula
- Complications following thoracic surgery
- Unilateral bronchospasm
Relative contraindications to lung isolation can be broadly categorized as factors related to DLT placement and patient factors.
Factors Related to DLT
- Difficult airway: Placement and positioning of a DLT in a patient with a difficult airway may be challenging or impossible. Repeated forceful attempts to intubate will increase the likelihood of airway injury. More significantly, loss of the airway during attempted placement of a DLT in a patient with a difficult airway may contribute to dangerous levels of hypoxia.
- Tracheostomy or stoma: Placement of a DLT through a tracheostomy or stoma may lead to excessive risk of iatrogenic injury.
- Intraluminal tumors of the trachea or proximal bronchi: Damage to intraluminal tumors by the placement of a DLT can lead to potential bleeding, tumor embolization, or DLT occlusion.
OLV should only be used in patients who can tolerate its resulting alterations in cardiopulmonary physiology. Several patient factors increase the chance of severe hypoxia during OLV, which, if persistent, will require reinitiating ventilation to both lungs.
- Patients with lung disease resulting in hypoxia during two-lung ventilation with a FiO of 100% are unlikely to be able to tolerate significant periods of OLV.
- Hypoxia is also more likely in patients who have had a previous contralateral lobectomy resulting in a greater than 25% decrease in lung function on that side.
- Morbid obesity may be associated with an increased risk of hypoxia during OLV.
- OLV should be used with caution in those with known pulmonary hypertension. Relative hypoxia and hypercarbia may develop during OLV and exacerbate preexisting pulmonary hypertension. In severe cases, this may precipitate right heart failure and hemodynamic collapse. A recent clinical study showed that a high ratio of minute ventilation to carbon dioxide output, as in pulmonary hypertension and ventilation-perfusion (V/Q) mismatch, is a predictor of hypoxia during OLV and suggests that this could be used for risk stratification.
Surgery on the right lung, which is larger than the left, may also be associated with an increased risk of hypoxia during OLV, but in patients with relatively healthy lungs, surgery on the right lung is tolerated without significant or prolonged periods of hypoxia.
Lung isolation is achieved using either a single-lumen endotracheal tube (SLT), DLT, or BB, depending on the clinical scenario. Fiberoptic bronchoscopy (FOB) is typically used to guide and confirm the placement and positioning of these tubes. It is vital for clinicians performing lung isolation to be familiar with the correct use of FOB in placing, positioning, and troubleshooting these devices. Choosing the appropriate bronchoscope diameter is also critical to prevent an inappropriately sized bronchoscope from becoming stuck, requiring removal of the entire DLT and reintubation or inability to advance the BB.
Single-lumen Endotracheal Tube
An SLT may be advanced into either the left or right mainstem bronchus to achieve lung isolation. This maneuver is typically easier on the right side, given that the trajectory of the right main bronchus closely parallels that of the trachea. The use of an SLT to achieve lung isolation is usually reserved for pediatric populations, as there are no DLTs manufactured for very small children. In emergency situations, such as the sudden development of left-sided pneumothorax or pulmonary hemorrhage in a previously intubated patient, an SLT can be advanced into the right main bronchus and used to achieve lung isolation.
Double-lumen Endotracheal Tube
A correctly positioned DLT will have its bronchial lumen in the mainstem bronchus with the bronchial cuff inflated such that it does not herniate over the carina. The tracheal lumen should be open to the opposite side, enabling selective ventilation of each lung, depending on which lumen is clamped. There are both right and left-sided DLTs, but because of the early branch point of the right upper lobe bronchus, a right-sided DLT has a second opening on the bronchial lumen to allow ventilation of the right upper lobe. Correctly positioning the bronchial cuff such that it does not occlude this bronchus is more challenging than on the left-side, so left-sided DLTs are generally preferred. However, a right-sided DLT is indicated for a left pneumonectomy or any other procedure that involves the proximal left main bronchus that would preclude the placement of a left-sided DLT. Both right and left-sided DLTs are available from several manufacturers ranging in size from 26 to 41 Fr.
There are several different models of BB available from different manufacturers. Each of these includes an inflatable balloon at the end of an introducer that can be advanced either through a standard endotracheal tube or an endotracheal tube with a small separate lumen containing the BB. The BB can be advanced under fiberoptic guidance into either mainstem bronchus to provide lung isolation. The BB can also be advanced into a more distal bronchus to provide selective isolation of a particular lung segment.
Several factors will influence the choice of the airway device. If definitive anatomic lung isolation is required to prevent the spread of purulence from an infected to a non-infected lung, a DLT is typically utilized as it is less likely to be dislodged once correctly positioned compared to a BB. A DLT also allows for suctioning or lavage of the diseased lung through the appropriate lumen, which is impossible with a BB. As mentioned previously, in emergency scenarios, such as the development of unilateral pulmonary hemorrhage in a patient who already has an SLT in place, advancing the SLT into the unaffected lung may be the best choice. This approach is also utilized in small children whose airways cannot accommodate the relatively large DLTs.
Purported advantages of DLTs over BBs include increased ease and rapidity of placement, more complete deflation of the non-ventilated lung, and less frequent need for re-positioning. However, some recent studies have cast doubt on these assumptions. In a study of patients undergoing video-assisted thoracoscopic surgery (VATS) for esophagectomy, the patients were randomized to either BB or DLT. While the time to complete lung-collapse was longer in the BB group, there was no significant difference in the time required to position the devices. Additionally, postoperative hoarseness and sore throat were more frequent in the DLT group. A similar study of VATS patients randomized to an endotracheal tube with a small separate lumen containing a BB or DLT demonstrated superior and more rapid lung collapse using the BB. In this study, surgeons were blinded to the device utilized and unable to distinguish between them.
A new generation of a DLT with an integrated high-resolution camera allows real-time video guidance during placement. This device has been shown to reduce the time to intubate and confirm tube placement after patient surgical positioning. Although this DLT is more expensive than traditional DLTs, it may provide overall cost savings because it typically negates the need for FOB.
The patient with preexisting tracheostomy presents a challenge for lung isolation. If the tracheostomy is less than seven days old, it should not be removed because the stoma may close during the procedure. In this case, a cuffed tracheostomy tube should be utilized as a conduit for a BB. The majority of practitioners also prefer this technique even for mature stomas because of its simplicity and reduction in the opportunity for iatrogenic airway trauma. Other alternatives include introducing an SLT through the tracheostomy stoma and directing it into the desired bronchus or removing the tracheostomy tube and placing the DLT orally.
During residency training, anesthesiologists have traditionally learned how to place DLTs and BBs on surgical patients under the direction and supervision of experienced faculty. However, more recently, simulators have become available for training in advanced airway techniques, including FOB and the placement of DLTs and BBs, such that trainees may have the opportunities to hone their skills outside the high-stakes environment of the operating room. Current accreditation Counsel for Graduate Medical Education (ACGME) requirements include 20 non-cardiac intrathoracic cases. However, there is no specific requirement for lung isolation.
Because inexperienced practitioners attempting lung isolation with either a DLT or BB have increased rates of device malposition and complications, it has been suggested that a deliberate practice model be utilized to augment initial training and maintain expertise. A recent study showed that novices could acquire DLT and BB placement proficiency on a mannequin with 90 minutes of training using either video didactics or a simulator. The authors also found that proficiency declined two months after training, emphasizing the importance of continued practice in maintaining lung isolation airway skills.
When utilizing lung isolation to facilitate surgery, a plan should be mapped out in advance with input from the surgical team. The patient should be well pre-oxygenated before the induction of anesthesia to compensate for underlying lung disease and because the placement of a DLT typically takes longer than an SLT. The anesthesia team should have all necessary equipment available, including that which may be needed for the patient with a difficult airway, if applicable.
Equipment List for DLT Placement
- Several sizes of DLTs
- SLTs as back-up
- A fiberoptic bronchoscope (including antifog solution and lubricating gel or spray)
- Tube exchanger
There is a lack of uniformity and objective guidelines in the selection of DLT sizes. Selecting the proper size DLT reduces the incidence of complications. Tube size recommendations can be based on gender and height. A 39F is recommended for men 165 cm or less in height, and a 41F for men taller than 165 cm. A 35F is recommended for women 160 cm or less in height, with a 37F being used for women taller than 160 cm. Radiologic measurement of the trachea's diameter or left mainstem bronchial diameter measurement from a computer tomographic (CT) scan can also be considered when selecting a left-sided DLT. Hannallah et al. concluded that when the choice of DLT size was based on clinical judgment alone, there was a risk of choosing too large a DLT relative to the patient's airway.
Equipment List for BB Placement
- Preferred BB device
- SLT of adequate diameter
- A fiberoptic bronchoscope (including antifog solution and lubricating gel or spray)
Once anesthesia is induced, and mask ventilation is verified, paralysis is typically administered to facilitate DLT placement. If the patient requiring lung isolation is unlikely to tolerate long periods of hypoxia or hypercarbia, such as those with severe pulmonary hypertension, then the most experienced practitioner available should secure the airway and achieve lung isolation. Bronchodilators should be available for patients with suspected reactive airways, and soft-suction catheters should be utilized to clear excess secretions and promote oxygenation.
If lung isolation is needed urgently or electively in the ICU setting, the approach to preparation should be similar to that described for surgical procedures. However, if lung isolation is needed emergently, such as in the case of significant unilateral pulmonary hemorrhage, the most expedient method to achieve lung isolation should be used with the most readily available equipment. For example, if the hemorrhaging patient is in an ICU remotely located from the operating rooms, procuring a DLT may take too much time; an SLT advanced into the unaffected bronchus should be used instead.
The most common method of DLT placement is direct laryngoscopy, followed by FOB to confirm positioning. Video laryngoscopy can be used successfully to place a DLT in a patient with a difficult airway. Because video laryngoscopes typically leave less room in the oropharyngeal cavity to maneuver, DLT placement may be cumbersome after a view of the vocal cords has been obtained. During direct or video laryngoscopy, the bronchial lumen of the DLT should be positioned anteriorly as it passes through the vocal cords. The DLT should then be rotated 45° clockwise or counter-clockwise for a right- or left-sided DLT, respectively.
Placement can be confirmed using auscultation of the chest during selective clamping of the bronchial and tracheal lumens; however, FOB is more definitive and is typically preferred. Examination with FOB can also confirm that the inflated bronchial cuff is visible but not positioned so proximally that it might herniate over the carina, an error in placement that would not be detected on auscultation alone. Some practitioners advocate using FOB to guide the DLT into the correct bronchus at the time of direct laryngoscopy. However, this typically requires a second practitioner.
Another technique particularly useful in difficult airway patients is to intubate with an SLT and then use a tube exchanger to guide placement of a DLT. The tube exchanger should be at least 83 cm long and slender enough to accommodate a single lumen of the DLT. Most tube exchangers have a central hollow lumen that can be connected to an oxygen source with an adaptor or used as a conduit for a fiberoptic bronchoscope.
Available BBs are dissimilar in design, requiring different techniques for placement.
The different BBs and techniques for placement are:
- Wire-guided device: This involves lassoing the blocker to a fiberoptic bronchoscope, which is then directed into the desired bronchus.
- BB with an incorporated stylet: This is inserted through a standard SLT allowing good control of the catheter tip, which can then be easily directed to block a selective lobar bronchus. The stylet is removed after placement, and the 1.4 mm lumen can be used as a suction port for rapid deflation of lobes or oxygen insufflation to apply continuous positive airway pressure to the deflated lobes.
- SLT with an introducer port through which the BB is inserted: The balloon tip of this blocker is flexed such that it can be more easily directed into the desired bronchus under fiberoptic guidance.
- BB with a unique bifurcated distal end with two separate balloons. This is designed to allow the placement of the cuffs in the left and right bronchi. Using FOB, the desired bronchus to be blocked is identified, and the appropriate cuff is inflated.
Some practitioners have reported success with placing the BB adjacent to the endotracheal tube rather than within it, a technique that may be advantageous in pediatric patients requiring small endotracheal tubes. BBs are usually inserted via an SLT, but placing them through a laryngeal mask airway is also an option in patients with a difficult airway.
Because of its larger caliber than an SLT, a DLT is more likely to cause trauma to the larynx, trachea, or bronchi. Iatrogenic tracheobronchial ruptures are rare but potentially devastating complications of DLT placement. Women, the elderly, patients of small stature, patients taking corticosteroids, and those with certain tracheal pathologies, including tracheomalacia and congenital anomalies, are more likely to experience these injuries. Postoperative hoarseness and sore throat are also more common after DLT compared to BB placement.
Hypoxic Pulmonary Vasoconstriction
Lung isolation and OLV result in a de facto pulmonary shunt, as blood continues to flow through the pulmonary vasculature of the non-ventilated lung. An admixture of the oxygenated and deoxygenated blood from the ventilated and non-ventilated lungs, respectively, causes a decrease in systemic PaO2 for a given FiO2. This reduction in PaO2 is mitigated by hypoxic pulmonary vasoconstriction (HPV), which is the pulmonary vasculature constriction in response to decreased oxygen tension. At its maximum, HPV will reduce perfusion of the non-ventilated lung by 40% to 50%. The remaining pulmonary shunt results in a PaO2, roughly half of that during two-lung ventilation for a given FiO2. Because mechanical ventilation with high FiO2 is typically used during lung isolation and OLV, PaO2 usually remains above 100 mmHg, a level that is well tolerated systemically.
However, the full effect of HPV is only reached after approximately two hours of OLV, such that problems with hypoxemia are more frequent and profound shortly after lung isolation is achieved. Additionally, several factors inhibit HPV and worsen oxygenation during lung isolation and OLV, including hypocapnia and hypothermia. Calcium channel blockers and vasodilators can also inhibit HPV. Volatile anesthetics inhibit HPV, but this effect is minimal with modern agents and is further minimized during OLV because the non-ventilated lung is minimally exposed. However, general anesthesia significantly contributes to decreased PaO2 through the resulting development of atelectasis in the ventilated lung, mainly if chemical paralysis is utilized.
Physiologic Effects of Positioning During Lung Isolation
If lung isolation and OLV are utilized to facilitate surgical exposure, the patient is usually positioned in the lateral decubitus position with the non-ventilated operative side superior to the ventilated non-operative side. During two-lung ventilation in the lateral decubitus position, gravity results in approximately 60% of cardiac output going to the dependent lung while the remaining 40% goes to the nondependent lung. When OLV is initiated, this preferential perfusion of the dependent lung improves VQ matching and oxygenation. Conversely, if lung isolation is used to prevent the spillage of secretions, purulence, or blood from one lung to the other in the intensive care setting, patients are more frequently positioned either supine or with the diseased lung in the dependent position such that gravity helps to prevent contamination of the healthy lung. This positioning worsens VQ matching, and the resulting decrease in PaO2 may be more exaggerated than in the operative setting.
Ventilator Management During Lung Isolation
Principles of lung-protective ventilation should be applied to lung isolation and OLV to minimize acute lung injury and other complications. Low tidal volumes (4 to 6 mL/kg ideal body weight) during OLV have been shown to decrease the incidence of acute respiratory distress syndrome, reduce pulmonary infiltration, and promote oxygenation. While PEEP can also help promote oxygenation, this must be tailored to the individual patient as patients with chronic obstructive pulmonary disease (COPD), for example, may develop alveolar hyperinflation. Recruitment maneuvers can also help promote oxygenation and prevent atelectasis during OLV but should be administered with caution in patients with lung bullae or emphysema. The use of pressure-controlled ventilation (PCV) compared to volume-controlled ventilation (VCV) may be associated with a higher PaO2/FIO2 and lower peak airway pressures; however, evidence for a difference in postoperative complications is lacking. There remains controversy about whether PCV should be recommended over VCV during OLV.
Hypoxemia during OLV should be approached systematically. If lung isolation and OLV are being utilized to facilitate surgery, the surgical team should be made aware of the patient’s hypoxemia and a potential return to two lung ventilation coordinated such that instruments can be withdrawn prior to lung reinflation. If the patient is stable and the hypoxemia is relatively mild, a logical first step is to confirm the correct placement of the airway device being used to achieve OLV using FOB. During bronchoscopy, the patient can be evaluated for the presence of secretions, other obstructions to the airway, or potential anatomical variants, such as a pig bronchus. Other methods to treat hypoxemia during OLV include administering bronchodilators, escalating PEEP, the performance of a recruitment maneuver, and administering oxygen to the non-ventilated lung.
Enhancing Healthcare Team Outcomes
Effective interprofessional communication between the operative and anesthesia teams is essential. A plan for achieving lung isolation, including which devices are most appropriate for the clinical scenario, should be established before starting the procedure. Establishing a plan for lung isolation in a patient with a difficult airway is particularly essential. Emergency airway equipment, including that required for a surgical airway, should be immediately available. It is also vital for perioperative nurses and anesthesia technologists or technicians to ensure that all necessary equipment is ready and working. This type of interprofessional interplay among healthcare team members can significantly improve patient outcomes. [Level 5]
Because there is conflicting evidence regarding whether a DLT or BB provides more rapid achievement of lung isolation or complete lung collapse, equipment choice may hinge upon individual provider preference and experience. Larger medical centers may have dedicated thoracic anesthesia teams comprised of select practitioners who maintain their proficiency and become experts in lung isolation. In smaller centers, this is usually not the case. As a result, relatively inexperienced practitioners will perform lung isolation techniques sporadically. Not only do inexperienced practitioners take 2 to 3 times longer to places these devices, but their positioning failure rates approach 40%. It is unknown whether simulator training could help maintain proficiency in lung isolation techniques for practitioners who only occasionally use these skills in the clinical setting.
Nursing, Allied Health, and Interprofessional Team Interventions
Managing lung isolation patients in the ICU setting requires multiple practitioners, including intensivists, nurses, and respiratory therapists. Usually, when this is needed, a DLT is used to maintain lung isolation, and all members of the care team should be familiar with the device. Because lung isolation in the ICU setting is relatively rare, members of the anesthesiology team should be prepared to provide education and support regarding using a DLT if necessary. If both lungs are to be ventilated, but with different settings, the respiratory therapist will be responsible for providing and maintaining two separate ventilators for each side. Aggressive pulmonary toilet practices, including frequent suctioning of both lumens and meticulous oral care, should be performed consistently by the nursing team. If lung isolation has been implemented due to unilateral infection, care must be taken to avoid contaminating the healthy lung with the diseased lung, including using different suction tubing for each side. Particular attention should be taken during patient transport, turning, or other activities when the DLT is at risk of being dislodged from its correct position.
Nursing, Allied Health, and Interprofessional Team Monitoring
When lung isolation and OLV are performed in the critical care setting, nurses are primarily responsible for monitoring these patients for any signs indicating a problem with lung isolation. A significant change in respiratory statuses such as hypoxemia, hypercarbia, or high peak airway pressures should prompt notification of an intensivist or anesthesiologist to verify correct device placement. Changes in the quality or quantity of suctioned secretions from each lung should also be monitored.