Which measurement is most helpful for evaluating a patient's compliance with a smoking cessation program?

The measurement that is most helpful for evaluating a patient's compliance with a smoking cessation program is multiple wave-length spectrophotometry. This method allows for the assessment of carboxyhemoglobin levels in the blood, which is indicative of carbon monoxide exposure. When patients smoke, carbon monoxide binds to hemoglobin more effectively than oxygen, leading to elevated levels of carboxyhemoglobin.

By utilizing multiple wave-length spectrophotometry, healthcare providers can accurately determine the extent of smoking exposure and monitor changes in carboxyhemoglobin levels over time. This information can reflect the patient's adherence to the smoking cessation program, as a successful cessation would typically lead to a decrease in these levels.

Other measurements, such as PaO2 and SPO2, while providing valuable information regarding oxygenation and overall lung function, do not specifically indicate smoking compliance. Similarly, methemoglobin levels can also be assessed using spectrophotometry, but this measurement does not correlate directly with smoking habits or adherence to cessation programs. Thus, the utilization of multiple wave-length spectrophotometry offers a direct assessment of smoking impact and is the most effective choice in this context.