Before a pneumonectomy, split lung function testing is indicated when a patient has:

In evaluating a patient for pneumonectomy, split lung function testing is critical when there is a concern for the functioning capacity of the remaining lung after the surgical removal of a lung. The patient's arterial blood gas values provide insights into their respiratory function, specifically the levels of carbon dioxide (PaCO2) and oxygen (PaO2).

A PaCO2 level of 49 mm Hg indicates hypercapnia, reflecting potential respiratory insufficiency and a compromised ability to effectively eliminate carbon dioxide from the body. Such elevated levels suggest that the patient's remaining lung function might not be adequate to support normal ventilation post-surgery. Therefore, split lung function testing is crucial in this scenario to assess the respiratory reserve and overall lung function, which helps ensure that the patient can tolerate the loss of lung volume without jeopardizing their overall gas exchange capabilities.

This thorough evaluation allows for a proactive approach to managing the patient's respiratory health and minimizes the risks associated with significant lung resections. Understanding the potential impact of altered lung function on postoperative outcomes is essential for making informed decisions regarding the surgery.