There are a variety of restrictive respiratory diseases, such as interstitial lung diseases, parenchymal lung diseases, extrinsic lung disorders and neuromuscular diseases that can cause reduction in lung volume, reduction in pulmonary function and impairment of gas exchange at the alveolar membrane. Patients with restrictive lung disease are at increased risk of morbidity and mortality in the perioperative setting requiring anesthesia, as their lung disease may compromise tissue oxygenation and the state can be exacerbated by an anesthetic. Patients with extrinsic factors often undergo surgical procedures due to the underlying conditions. However, regardless of the lung disease being due to an intrinsic or extrinsic factor, special care, such as special surgical positioning should be included in the risk for impaired gas exchange care note. Surgical positioning during general anesthesia and mechanical ventilation can have significant physiologic effects on ventilation, pulmonary perfusion, and intrathoracic pressure. Patients with severe restrictive respiratory disease may benefit from specific positioning during surgery to ensure adequate tissue perfusion.
Here is a helpful guide to surgical positioning in patients with restrictive lung disease.
The supine position does not seem to be an ideal position for patients with restrictive lung disease. The position can have a negative effect on the functional residual capacity (FRC), which is further reduced by the general anesthetic. Patients in supine position are at risk for airway closure, atelectasis, and V/Q mismatch. To improve oxygenation and to increase lung volume, clinicians may choose to change patients from supine to semi-recumbent position by raising the head up by 30 degrees.
The lateral decubitus position may naturally result in V/Q mismatch, particularly during general anesthesia, due to the gravitational forces. It may decrease FRC, ventilation, and compromise oxygenation during anesthesia, as well as it may have negative effects on the dependent lung, with changes in perfusion and possible fluid accumulations. Nurses should avoid administering large volumes of fluid in these patients as it can further exacerbate fluid overload which can have detrimental effects.
The prone position, unlike the supine position, rather affects the pulmonary compliance which results in higher peaks of airway pressure. During prone position, the venous return to the heart is also decreased, while the pulmonary and systemic vascular resistance is increased as there is naturally a pressure to the chest and abdomen. If the abdominal compression can be avoided, this position may have a beneficial effect on pulmonary function, seen by an increase in FRC, improved V/Q matching and improved oxygenation.
Sitting position may be the optimal position for patients on mechanical ventilation. During a sitting position the intrathoracic pressure is lowest, optimizing the mechanical ventilation process. During sitting position, FRC and lung compliance increase, unlike in supine, lateral, and prone positions. The negative aspect of this position is that the cardiac output tends to decrease in this position, overall affecting the oxygenation of the body.
The Trendelenburg position, during which a patient is placed with their head down and feet elevated is associated with increased venous return, increased central blood volume and increased mean arterial pressure. The movement of abdominal viscera against diaphragm decreases FRC and overall lung compliance, possibly resulting in complete or partial collapse of the entire lung, also known as atelectasis. This position seems less than ideal for surgical patients with restrictive lung disease.
The reverse Trendelenburg position, with the patient laying down with the head tilted up and feet down naturally, due to gravitational forces, results in blood pooling in the lower extremities and abdomen. This leads to a reduction in central blood volume and venous return, often resulting in a decrease in stroke volume and decrease in cardiac output. Because of this, extreme caution should be taken in patients with decreased cardiac output. On the other hand, the reverse Trendelenburg position can naturally relieve the pressure from the abdominal area, especially diaphragm and chest wall, increasing the FCR and lung compliance.
The lithotomy position-with legs flexed at 90 degrees at the hips can cause small increases in venous return and cause decrease in the FRC and pulmonary compliance.
- Gruenbaum, Shaun, Viji Kurup, and Helen Hollingsworth. “Anesthesia for patients with interstitial lung disease or other restrictive disorders.” Uptodate, January 2021