What’s normal about airway resistance?
The question that was actually posed to me a month or so ago was “when is RAW abnormal?” I didn’t have a good answer at the time since airway resistance (RAW) tests are not performed by my lab. The…
Category pftblog
Thinking about the past
This is the time of the year when it’s traditional to review the past. That’s what “Auld lang syne”, the song most associated with New Year’s celebrations, is all about. I too have been thinking ab…
2017 ATS PFT Reporting Standardization
The ATS has released its first standard for reporting pulmonary function results. This report is in the December 1, 2017 issue of the American Journal of Respiratory and Critical Care Medicine. At …
Making Assumptions about TGV and FRC
When lung volumes are measured in a plethysmograph the actual measurement is called the Thoracic Gas Volume (TGV). This is the volume of air in the lung at the time the shutter closes and the subje…
The effect of errors in Inspiratory Volume on DLCO.
Yesterday while reviewing reports I ran across an interesting error in the Inspiratory Volume (VI) from a DLCO test. I’ve probably seen this before but this time I realized what effect it could hav…
DLCO, de-constructed
My wife watches the Food Network a lot and I occasionally watch it with her but I can only take so much of it before I go off and read or work on one of my projects. I’ve noticed however in the var…
COHb and Pulse Oximetry
I was reviewing a report recently that included the results for walking oximetry. These showed that the individual has a resting SaO2 of 97% and desaturated significantly to 86% after walking a cou…
Why the FEV1/FVC ratio LLN as a percent of the predicted FEV1/FVC ratio is important
My medical director and I had a discussion today about where the cutoff for a normal FEV1/FVC ratio would be for a 93 year old patient of his. Part of the problem is that there are almost no refere…
What’s normal about the GLI DLCO reference values?
The Global Lung Initiative (GLI) has been working for several years to develop a universal reference equation for DLCO. Although this endeavor is not necessarily complete, an article describing the…