Introduction:
One-lung ventilation separates the two lungs; each lung functions independently by preparing the airway. It involves ventilation through only one lung, allowing the other lung to collapse for further surgical exposure into the thoracic cavity. The main purpose of single-lung ventilation is to protect the lung from the harmful effects of the other lung. Therefore, it is important to ensure that the tube is placed perfectly with the help of a bronchoscope because if it is wrongly placed, it fails to serve its purpose. It allows many procedures on the same side of the thoracic and mediastinal structures and lung isolation. This is ensured by using double-lumen tubes, bronchial blockers, and endobronchial tubes. The procedure requires a skillful team of anesthetists because of the difficulty in placing the lung isolation equipment, the ability to overcome hypoxic pulmonary vasoconstriction, and the patient population being comparably sicker.
What Are the Indications of One Lung Ventilation?
One-lung ventilation is necessary in cases of
Lung isolation:
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Severe pulmonary hemorrhage.
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Infection with purulent secretions.
Ventilation control:
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Tracheobronchial trauma.
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Bronchopleural or bronchocutaneous fistula.
Surgical exposure:
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Video-assisted thoracoscopic surgery in wedge resection, segmental resection, or pneumonectomy.
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Lung resection involving pneumectomy and lobectomies.
What Are the Contraindications for One-Lung Ventilation?
The contraindications for one-lung ventilation are:
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Patients depend on bilateral ventilation.
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Intraluminal airway masses make it difficult to place the double-lumen tube.
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Severe hypoxia.
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Severe chronic obstructive pulmonary disease (COPD).
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Severe pulmonary hypertension.
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Difficulty in intubation.
What Are the Devices Available to Achieve One-Lung Ventilation?
There are several devices available to achieve one-lung ventilation. The most commonly used device is the double-lumen tube, the Robertshaw design being the most widely used. It is available for both sides, and the size ranges from twenty-six Fr to forty-one Fr. The tubes' size depends on the tube's external diameter. Prepare and check the tube, and ensure the cuffs inflate and deflate. Insert the tube along with rigid stylet and distal concave curvature facing anteriorly. Remove the style once vocal cords are reached. Rotate the tube perpendicular to the direction of the desired lung. Advancement of the tube is stopped when resistance is felt. The average lip line is 29+/-2 cm. If a cardinal hook is present, then it should be carefully advanced to avoid trauma. The left double-lumen tube is the most commonly used. The bronchial lumen is longer, and a simple round opening and symmetric cuff are present. It has a better margin of safety than the right double-lumen tube. There is a risk of tube change and airway damage if kept in position for postoperative ventilation.
Contraindications of Double Lumen Tube Are
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Presence of lesion along double lumen tube pathway.
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Difficult/impossible conventional direct vision intubation.
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Critically ill patients with a single lumen tube in situ who cannot tolerate even a short period of off mechanical ventilation.
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Full stomach or high risk of aspiration.
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Patients, too small, less than 25-35 kg, or too young, less than eight to 12 years.
Check Tube Placement by Auscultation:
Inflate the tracheal cuff and verify equal breath sounds or bilateral inflation. Clamp the white side or the tracheal lumen and remove the cap from the connector. Expect some left-sided ventilation through the bronchial lumen and some air leak past the bronchial cuff, which is not yet inflated. Slowly inflate the endobronchial cuff until minimal or no leak is heard at the uncapped right connector. Remove the clamp and replace the cap on the tracheal side. Check that both lungs are ventilated. Selectively clamp each side, and expect visible chest movement and audible breath sounds only on the right when the left is clamped and vice-versa.
Check Tube Placement With the Fiberoptic Bronchoscope:
Several situations exist where auscultation maneuvers are impossible. Patients do not provide reliable information about pre-existing lung disease because breath sounds are not audible or if the tube is only slightly malpositioned. The double-lumen tube's precise position can be most reliably determined with the help of a fiberoptic bronchoscope. Most patients with double-lumen tubes whose position seemed appropriate for auscultations had some malposition. So always check the position with a fiberoptic bronchoscope. After advancing the fiberoptic scope through the tracheal tube, one should see the bronchial blue balloon in a semilunar shape, just peeking out of the bronchus. To ensure the correct position of the double-lumen tube, clinical breath sounds should be normal (not diminished) and follow the expected unilateral pattern with unilateral clamping; the chest rises and falls by the breath sounds.
Lung separation can be achieved using a single-lumen endotracheal tube and a fiberoptic bronchoscope-placed bronchial blocker. It impedes the main-stem bronchus, preventing ventilation distal to the occlusion. Bronchial blockers can be used to provide selective lobar collapse. Many children need double-lumen tubes. Balloon-tipped luminal catheters can allow suctioning and oxygen injection down the central lumen.
What Are the Complications of One Lung Ventilation?
The most common complication is hypoxia. Immediately after the beginning of one-lung ventilation, there is a drop in arterial oxygenation and saturation, which gradually increases as hypoxic pulmonary vasoconstriction increases. This can be prevented by:
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Increase in the fraction of inspired oxygen (FiO2).
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Recheck the position of the double-lumen tube or bronchial blocker.
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Check if the patient is hemodynamically stable with optimal cardiac output.
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Insufflation of oxygen followed by application of 1-5 cm H20 of CPAP to the non-ventilated lung.
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Perform recruitment maneuvers to the ventilated lung. This may result in transient hypotension and hypoxemia if more blood is diverted to the non-ventilated lung.
Conclusion:
Lung isolation techniques are being extensively used to allow lung ventilation in patients undergoing surgeries of the esophagus, aorta, or thoracic spine. In addition, with the increase in minimally invasive combined procedures for upper gastrointestinal surgeries, one-lung ventilation has gained popularity. Therefore, in-depth knowledge of various techniques available and their use for initiating and maintaining one-lung ventilation is essential for anesthesiologists.
