Do you favor the use of Fick or thermodiluation to measure cardiac output in patients with interstitial lung disease with suspected pulmonary hypertension?

Unless the patient has a left to right shunt or a metabolic cart is used to calculate direct Fick, thermodilution cardiac output (TDCO) is the preferred method of cardiac output measurement in all patients with pulmonary hypertension. This is supported by current guidelines. It's important to take the average of 3 TDCO measurements that are within 10% of each other. Severe tricuspid regurgitation does not appear to affect this measurement (Hoepper et al., PMID 10430725). Additionally, as you mention, supplemental oxygen, particularly at high FIO2, will interfere with this measurement as the dissolved oxygen content is typically not accounted for. I make a routine habit of performing 100% oxygen challenges on all patients with underlying lun...

I completely agree with all of the above. There are too many assumptions during the indirect Fick CO calculation, including which formula will be used to estimate O2 consumption. Similarly if at any point an exercise challenge is undertaken, once again TD CO would be the more accurate measurement.

On the other hand, if you have the ability to routinely measure direct Fick, then you could argue for that strategy as the more accurate, but as noted above a metabolic cart and added support staff is required.