Intraoperative Management of Obstructive Lung Disease: Avoiding Hyperinflation

Intraoperative management must be tailored to prevent exacerbations, maintain effective ventilation, and minimize the risk of dynamic hyperinflation or barotrauma.

Choice of Anesthetic Technique

The choice of anesthesia in patients with obstructive lung disease depends on the type of surgery and the patient’s respiratory status. While general anesthesia is often required for major procedures, regional anesthesia techniques (e.g., spinal or epidural anesthesia) are preferred for surgeries on the lower extremities or abdomen, as they avoid airway manipulation and minimize the risk of respiratory depression. 

Benefits of regional anesthesia include:

• Reduced postoperative pulmonary complications, such as atelectasis and pneumonia.
• Avoidance of bronchospasm, which can be triggered by airway manipulation during intubation.
• Decreased need for systemic opioids, which can depress respiratory drive.

However, regional anesthesia is not always appropriate, particularly in upper abdominal or thoracic surgeries that require adequate ventilation. In these cases, general anesthesia with controlled ventilation may be necessary.

Airway Management

Airway management in patients with obstructive lung disease requires careful planning to minimize airway reactivity and ensure effective ventilation. Key considerations include:

Preoxygenation: patients with obstructive lung disease are susceptible to rapid desaturation. Although air trapping raises the resting lung volume (functional residual capacity, FRC), much of that volume is poorly ventilated, so ventilation-perfusion mismatch and a high work of breathing leave little usable oxygen reserve. Preoxygenation with 100% oxygen for 3-5 minutes before induction can provide a buffer against hypoxia during intubation.

Anesthesia induction: induction agents such as propofol, which has bronchodilatory properties, are preferred in patients with obstructive lung disease. Ketamine is another option for induction, as it preserves respiratory drive and has bronchodilatory effects. Thiopental, now rarely available, was associated with bronchospasm because light barbiturate anesthesia leaves airway reflexes intact rather than through direct bronchoconstriction; the lesson for any agent is that the airway should not be instrumented until the patient is deeply anesthetized. Intravenous lidocaine 1-1.5 mg/kg given 1-3 minutes before laryngoscopy, or inhaled albuterol 15-30 minutes before induction, further blunts the reflex bronchoconstriction that intubation provokes.

Endotracheal intubation: intubation should be performed gently to minimize airway trauma and reduce the risk of bronchospasm. Tracheal intubation is the most common trigger of intraoperative bronchospasm, so laryngoscopy should be brief and performed only at an adequate depth of anesthesia, after the pretreatment described above. Rapid sequence induction is chosen for aspiration risk, not for airway reactivity; when it is needed, propofol or ketamine with a full dose of rocuronium or succinylcholine still allows intubation at adequate depth.

Supraglottic airway devices (SGAs): while SGAs can be used in select patients to avoid endotracheal intubation, they are not always appropriate for patients with severe obstructive lung disease, particularly in surgeries that require positive pressure ventilation. When the procedure and aspiration risk allow, an SGA is the gentler choice: laryngeal mask insertion produces far less bronchoconstriction than tracheal intubation, and avoiding a tube in the trachea also removes the main stimulus for bronchospasm at emergence.

Ventilation Strategies

The primary goals of mechanical ventilation in patients with obstructive lung disease are to prevent dynamic hyperinflation, minimize barotrauma, and ensure adequate oxygenation. Key strategies include:

Low tidal volumes: Tidal volumes of 6–8 mL/kg of ideal body weight are recommended to avoid overdistension of the alveoli and reduce the risk of barotrauma. Large tidal volumes should be avoided, as they can exacerbate hyperinflation.

Prolonged expiratory times: In patients with obstructive lung disease, prolonged expiratory times are necessary to complete exhalation and prevent air trapping. This is achieved by reducing the respiratory rate (often 8-12 breaths per minute), shortening inspiratory time with a higher inspiratory flow, and lengthening the expiratory side of the inspiratory-to-expiratory (I:E) ratio to about 1:3 to 1:4.

Auto-PEEP (intrinsic PEEP): When expiration is cut short by the next breath, gas is trapped and end-expiratory alveolar pressure stays above the set PEEP. Recognize it on the ventilator's flow-time waveform, where expiratory flow has not returned to zero before the next inspiration begins, and confirm it with an end-expiratory hold, which displays the total PEEP. The consequences are rising peak and plateau pressures, falling venous return with hypotension, and, in the extreme, pulseless electrical activity that mimics tension pneumothorax. Treatment is to let the lungs empty: disconnect the circuit for 20-30 seconds if the patient is hypotensive, then lower the rate and tidal volume, lengthen expiratory time, and treat bronchospasm.

Positive end-expiratory pressure (PEEP): External PEEP does not add to air trapping as long as it stays below the intrinsic PEEP; set at roughly 80% of the measured intrinsic PEEP, it holds small airways open during expiration and, in a spontaneously breathing patient, reduces the work of triggering the ventilator. PEEP above that level adds to hyperinflation. In practice this means modest PEEP, about 5 cmH2O, adjusted to the intrinsic PEEP measured with an expiratory hold, rather than a fixed higher value.

Permissive hypercapnia: Permissive hypercapnia, or allowing the partial pressure of carbon dioxide (PaCO2) to rise slightly, is acceptable in patients with severe obstructive lung disease, as aggressive attempts to normalize PaCO2 can result in high airway pressures and barotrauma. The PaCO2 is allowed to rise as long as arterial pH stays above about 7.20-7.25; hypercapnia is avoided in patients with raised intracranial pressure or severe pulmonary hypertension, in whom it is harmful.

Maintenance of Anesthesia

Volatile anesthetics: Sevoflurane and isoflurane relax airway smooth muscle and are the maintenance agents of choice; sevoflurane is also non-pungent, which makes it the volatile agent for an inhalational induction or for deepening anesthesia during bronchospasm. Desflurane is the exception: it is pungent, raises airway resistance rather than lowering it, especially in smokers and at higher concentrations, and is best avoided in reactive airways. All volatile agents cause dose-dependent respiratory depression and blunt the ventilatory responses to hypoxia and hypercapnia, requiring careful titration when spontaneous ventilation is kept.

Total intravenous anesthesia (TIVA): TIVA, using agents such as propofol and remifentanil, can be an excellent alternative in patients with asthma, as it avoids potential airway irritation associated with volatile agents. TIVA may also reduce the risk of postoperative nausea and vomiting, leading to earlier recovery of respiratory function.

Hemodynamic Management

Hemodynamic stability in patients with obstructive lung disease is important, especially in those with pulmonary hypertension or cor pulmonale. Intraoperative goals include:

• Avoid hypoxemia, hypercarbia, and acidosis, all of which increase pulmonary vascular resistance and strain the right ventricle.
• Ensure adequate preload and afterload management to support right ventricular function.
• Monitor signs of right heart failure, such as hypotension and elevated central venous pressure (CVP), and manage these with vasopressors or inotropes as necessary.

Use of Medications

Some medications should be avoided or used cautiously in patients with obstructive lung disease to minimize bronchospasm and other complications. These include:

Histamine-releasing agents: The neuromuscular blocking agents atracurium and mivacurium, and the opioids morphine and meperidine, release histamine and can trigger bronchospasm. Cisatracurium, rocuronium, or vecuronium, and fentanyl or remifentanil, are preferred. Reversal with neostigmine increases secretions and airway tone through its muscarinic effect, so it is always paired with glycopyrrolate; sugammadex avoids this altogether.

Bronchodilators and intraoperative bronchospasm: Inhaled albuterol or ipratropium can be given through the breathing circuit to maintain airway patency. When bronchospasm occurs (rising peak pressure with a normal plateau pressure, a sloping upstroke on the capnogram, wheeze or a silent chest, and falling tidal volume on pressure-controlled ventilation), first exclude a kinked or obstructed tube, endobronchial intubation, and light anesthesia. Then give 100% oxygen and deepen the anesthetic with sevoflurane, propofol, or ketamine; deliver albuterol 8-10 puffs through a metered-dose inhaler adapter in the inspiratory limb (most of each puff is lost in the tracheal tube, so the dose is far higher than the usual two puffs); for severe or refractory spasm give epinephrine intravenously in 10-100 mcg increments, or by infusion if needed; and add hydrocortisone 100 mg intravenously (its benefit takes several hours), magnesium sulfate 2 g over 20 minutes, and ketamine 0.5-1 mg/kg if spasm persists. Treating bronchospasm is also the moment to lower the respiratory rate and lengthen expiratory time, because gas trapping worsens as airways narrow.

Steroids: Patients with severe asthma or recent COPD exacerbations may benefit from perioperative systemic corticosteroids. In patients on chronic steroids, stress-dose steroids should be administered to prevent adrenal insufficiency.