CPT® Code 94400

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This pulmonary function test, identified by CPT® Code 94400, is designed to assess the patient's respiratory response to elevated levels of carbon dioxide (CO2) in the air they breathe, a condition known as hypercapnia. During the procedure, a mask is securely placed over the patient's mouth and nose to ensure that the gas mixture is inhaled effectively. The test utilizes a controlled gas mixture that gradually increases the concentration of CO2, ranging from 1% to 7%. As the patient inhales this gas mixture, the exhaled air is collected and analyzed using specialized gas analyzers. These analyzers measure the composition of the exhaled gases, allowing for the evaluation of how the patient's respiratory system reacts to the increased CO2 levels. The data collected during the test is used to create a CO2 hypercapnic response curve, which is generated by a computer. This curve illustrates the relationship between the levels of CO2 inhaled and the corresponding changes in the patient's breathing response. Following the test, the physician interprets the results, reviewing the variations in the exhaled gas values and the generated CO2 response curve, and subsequently provides a written report detailing the findings. This test is crucial for understanding the patient's respiratory function and can aid in diagnosing various pulmonary conditions.