Over the last couple of years I’ve run across a number of test systems that do not include tidal loops along with the maximal flow-volume loop. I’ve wondered why this was done and because of this I’ve thought a lot about tidal flow-volume loops and what additional information, if any, they add to spirometry interpretation….
The 2005 ATS/ERS spirometry standard make it permissible and even recommends that the FVC and FEV1 be selected from different efforts. I disagree somewhat with their criteria for selecting the FEV1 but overall reporting composite results makes a lot of sense. In an ideal world we’d always get the best FVC and FEV1 in a…
A couple days ago I pulled my copy of the Intermountain Thoracic Society manual on pulmonary function testing off the bookshelf and thumbed through it a bit. It was first published in 1975 and was the first major attempt towards standardizing the performance and interpretation of PFTs. My first thought was that we’ve come a…
A set of guidelines for grading spirometry quality was included with the recently published ATS recommendations for a standardized pulmonary function report. These guideline are similar to others published previously so they weren’t a great surprise but as much as I may respect the authors of the standard my first thought was “when was the…
One of the limitations of the single-breath DLCO is that the equation used to calculate results implicitly assumes that the entire breath-holding period occurs at TLC. Mathematically, what happens to the diffusion of carbon monoxide (CO) during inspiration and expiration is not a consideration: The different approaches towards measuring breath-holding time (BHT) make allowances for…
One of the recommendations in the 2017 ERS/ATS DLCO standards was that VA should be calculated using a mass balance equation. I’ve discussed this approach previously, but basically the volume of the exhaled tracer gas is accumulated over the entire exhalation and the amount of tracer gas presumed to remain in the lung is used…
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 pulmonary physicians I work with don’t think that RAW is a clinically useful measurement and for…
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 about the past but it’s not been about absent friends, it’s been about trend reports and assessing trends. In the…
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 the present time however, despite its importance it is not an open access article and you must either be a member of the…
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 subject performs a panting maneuver. Ideally, the TGV measurement should be made at end-exhalation and should be approximately equal to…