Blog Author

Hi!  My name is Richard Johnston.  Pulmonary Function testing is an often overlooked and under-appreciated field.  I first started working in a Pulmonary Function Lab with manual test systems in 1973 where I had to measure pen traces on kymograph paper and hand-calculate test results.  I’ve built, maintained, repaired and modified test equipment since I started in this field.  I started working with computers in the 1970’s and designed and wire-wrapped my own hardware interfaces for them because that’s what you had to do at the time.  I’ve programmed computers for research and routine clinical testing and somehow managed to have one of the first networked PFT labs in Boston. Over the years I’ve learned a lot about equipment but that’s because I broke a lot of things along the way too.  

Against my inclination and better judgement I have been a lab manager for over 30 years.  I found that my job description changed every year and that my hospital managers always seemed to feel that I was supposed to have figured what the changes were on my own.  Although I’ve done my share of research I’ve come to feel that a clinical Pulmonary Function Lab is where the rubber hits the road and far more enjoyable for that reason. I feel fortunate that I’ve always worked in teaching hospitals with physicians that were interested in education.  I’ve learned a bit about teaching and have taught numerous students, technicians and physicians about Pulmonary Function and Cardiopulmonary Exercise testing. The most important thing I’ve learned however, is that there is always something new to learn.

I am primarily a technologist.  For that reason my interest starts with the tests and the test equipment, but the reality is that you can’t consider these things in isolation. What’s also important is the physiology and anatomy of what the tests are supposed to be measuring; how you decide what’s normal and what’s abnormal; how the information is stored and reported; what purpose the tests have for the patient and the ordering physician; and how to run a testing facility effectively.

Because I’ve personally built test systems and programmed computers I’ve learned how hard it can be to get equipment to do what you want it to do.  In order to find out how to do tests and build things I’ve had to read a lot of textbooks and research papers by authors who seemed to delight in making them obscure and hard to understand.  Worst of all I’ve had to become a skeptic since I’ve known some of the researchers who bent the results to fit their preconceptions and still got published.  Despite the negatives I feel fortunate that I’ve had to opportunity to do these things.

I am now semi-retired which has given me the time to work on projects that interest me, one of which is this blog.  I’m presently involved in a number of PFT-related projects and I don’t have time to be bored because there are just too many interesting things to do.

Feel free to contact me at

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47 thoughts on “Blog Author

  1. According to 2005 ATS-ERS Standards, it is not recommended that more than 5 DLCO SB tests be taken in a short period of time (even if spaced ~5 minutes apart). Is there a particular CO back-pressure that renders the test useless, even if your system allows you to input in current COHB levels? More specifically, in testing smokers and those with obstructive disease, what limitations should we put on the testing in terms of the number of tests, and time between tests, if we can intermittently test for COHB backpressure using Smokerlyzer systems? The current recommendations are quite “loose” for this.

    • Josh –

      There are two issues that are affected by increasing COHb and PACO levels during DLCO testing; patient safety and test accuracy. You are right that the ATS/ERS standards on DLCO testing are “loose” and don’t provide good guidelines about these issues. My lab has used an upper limit of 4 DLCO tests (and an inhalation of the DLCO gas mix is counted as a test even if the patient didn’t finish the test correctly) for the last 25 years. This is somewhat arbitrary but is based on the observation that each inhalation of the DLCO gas mixture causes an increase in COHb of ~0.7%. Four tests means you’ve raised a patient’s COHb by ~2.8% which I think is enough (waiting even 30 minutes between tests won’t make much difference since the half life of CO is ~3-4 hours). As far as safety goes I think there is a big difference between a healthy 20 year old and a hypoxic 70 year old with COPD but it is not really possible to quantify this. If you wanted to go (way, way) out on a limb I could point out that the recent ATS/ERS statement on walking tests says the test should be terminated when SpO2 decreases below 80% so theoretically you could do a dozen DLCO tests without reducing a patient’s SaO2 below that level. Is this safe or advisable? I really don’t think so particularly since what are you getting out of a DLCO test that is worth compromising a patient so badly? So, a limit of 4 tests may be arbitrary but my feeling is that if you haven’t been able to get an acceptable test after 4 tries the chances of getting one with even more tries isn’t very good.

      As far as test accuracy, measuring a patient’s exhaled CO can help correct the test but COHb is more important. You can estimate COHb from exhaled CO but I’d emphasize the word estimate and would have to say that the accuracy of the estimate is only so-so. Even so, patients have to exhale to RV at the start of a DLCO test and I’d like to see the PFT equipment manufacturers measure the patient’s exhaled CO just before the test starts in order to determine the starting CO back pressure. Not perfect, but it would improve test accuracy a bit. BTW, strictly speaking if you know what the patient’s COHb and PACO are there is no particular upper limit other than patient safety on their baseline pre-test values that prevents you getting accurate results. Having said that I’ve seen at least one theoretical study that indicated that the anemia affect from COHb is not the same as actual anemia but their correction for this wasn’t significantly different from the ATS/ERS standards except at high COHb levels (and it was theoretical after all).

      The ability to correct DLCO results by measuring PACO and estimating COHb probably reduces the error bar in DLCO testing but Hb, PAO2, pulmonary capillary blood volume and cardiac output probably affect them at least as much and probably a fair amount more. My experience is that even when you try to control all these factors DLCO still can change significantly from one test to another for no readily apparent reasons. Doesn’t mean you don’t try to get reproducible results as best you can but also you need to recognize there are limits on your ability to do so.

      – Richard

  2. Hello Richard! I must say I truly love your blog and it’s great to see others take an interest in PFT’s. I’m currently working at the PFT lab at UCLA Medical Center, and was in the process of opening my own mobile lab. Do you believe this is a worthwhile investment? How much can I expect to receive from billing for a PFT? I have checked the CMS and medicare and have a rough estimate but I wanted to confirm that the amount I see of 140-170$ per test is an accurate representation.
    Thanks in advance!

    • Emin –

      For a full panel of tests (spirometry, lung volumes, DLCO) you’re probably in the right ball park but spirometry alone is a lot less and that is what most physicians will order.

      Before starting an independent PFT Lab there are a number of questions you will need to answer. First, where are your patients going to come from and why would anybody send them to your lab rather than a hospital-based PFT Lab? What do you expect your test mix to be? (You’re not going to get a lot of spirometry patients, office spirometers are inexpensive and office spirometry is lucrative). How many patients a day do you expect (and what are you going to do when they show up late?). Who is going to do the test interpretation (you can’t, has to be a board certified pulmonary physician) and how are you going to pay them? How are you going to get results to the ordering physician? You mentioned a mobile lab. What are your operational costs going to be? How do you get wheelchair patients into your vehicle? How are you going to meet state and local regulations? When are you going to take time off and who’s going to take your place when you’re not available (sickness, vacation, jury duty)? Finally, most importantly, who’s going to do your billing and how are you going to get insurance companies to do business with you in the first place?

      I’m not trying to rain on your parade. I’ve taken small business courses and written business plans. These (and many, many more) are the kinds of questions that any bank is going to be asking you. I would be very interested in hearing your answers. Other than OSHA testing I don’t know of any independent PFT Labs (doesn’t mean there aren’t any, I just haven’t run across one yet).

      Best wishes,

      – Richard

  3. Thank you so much Richard for your outstanding blog & wonderful educational resource for anyone in the field. I have worked performing PFT’s for nearly 10 yrs and your blog posts cover many of the issues i have pondered over that time. You have validated my constant questioning & it makes me feel so much better knowing i am not alone in the way my brain works 🙂

  4. I agree with Kim B., Richard you are a great resource and much appreciated. Working in a small occupational setting I really appreciate having someone like you to turn to with my questions. Thanks so much !

    • Thank you all for your kind words. I am fortunate not only to have the time to write but also to be able to write about things that interest me. It’s nice to know that there are many people who, like myself, are interested in the nuts and bolts of Pulmonary Function testing and even nicer that they appreciate what I have to say. I have a good-sized list of topics and new ones keep popping up so I suspect I’ll continue to be at it for a while. Warm regards to you all.

  5. Mr. Johnston thank you for a very interesting, useful and educational blog.
    Keep up the excellent work. I am happy people still find this physiology interesting.

  6. Mr Johnston,
    Thanks in advance for your useful information presented in this forum. I`m Ignacio writing from Argentina and I worked as a technician in pulmonary laboratory. I was wondering if you can tell me which is the best way to apply the methacholine challenge test. I`ve been reading and provocholine seems to be the best supply, can you recommend me the best nebulizers and dosimeters for this practice, currently used? Because we find that the English Wright Nebulizer for breathing method and the De Vilbiss model 646 for the five-breath dosimeter method require a very precisely calibration.
    Thanks for your time,

    • Ignacio –

      I’ve avoided methacholine challenges as a topic so far partly because there is a lot of conflicting research concerning it, partly because I’ve re-written the procedure for methacholine far more often than for any other test my lab performs (and even now I’m not sure I’ve got it right) and partly because the ATS/ERS is supposedly releasing a new statement/standard on methacholine challenges soon and I’ve been waiting to see what’s in it. I’m probably going to catch some flak from other readers about my recommendations, but here goes.

      My first recommendation is to not use a dosimeter at all and instead go for a 2-minute tidal breathing technique. It’s my opinion that the use of dosimeters is pseudo-science because they really don’t control the received dose. I’d also recommend using any standard disposable nebulizer since any re-usable nebulizer’s characteristics change every time they are cleaned. It’s also my opinion that characterizing nebulizers by measuring their change in weight after a specific time period to determine their output in microliters/min is looking at the wrong thing since what this process doesn’t do is to measure the particle size distribution which is far more important for determining deposition in the airways. Finally, it’s my opinion that reporting cumulative dose (i.e. PD20) is also pseudo-science since there is no way whatsoever to determine it with any accuracy other than a guess (take a close look at how it’s calculated) and because it’s also my opinion that airways are sensitive to concentration, not cumulative dose.

      I’ve been doing methacholine challenge tests for over 35 years and quite honestly when I read the literature on it, I still get confused. I think there is a big disconnect with the physical details of how the test is performed, the measurements researchers are reporting and what measurements I think they can really get. Having said all of this I still think there is a clinical value in performing the test. It is usually fairly clear who is a responder and who isn’t no matter how you go about it. There are always going to be some patients who have an equivocal response where it’s not going to be clear whether they are truly positive or negative and that’s also going to happen no matter how you perform the test, and for these patients I always report them as a “maybe” rather than worrying about how far above or below the threshold they may be.

      Regards, Richard

  7. Thank you for your informative posts! I was just doing a test run of single breath nitrogen washout and found out that the system in my hospital’s lab, a medgraphics ultima pf with breezesuite, is able to generate values of TLC and RV from the test manouvre!
    This was really surprising to me and my other colleagues. Have you had any experience on this?

    • Anthony –

      I wasn’t aware that MGC Diagnostics was doing this with SBN2, but a number other manufacturers have been generating lung volumes using the VA from the DLCO test which is also a single-breath test and there’s no particular reason you couldn’t do the same with a SBN2. Is it accurate? Depends on how good the gas mixing is inside the lung of the individual performing the test. The more obstructed they are (and this happens with aging as much as it does with airway disease) the less likely it’s going to be accurate. I wrote about single-breath lung volumes several years ago ( and I will also mention in passing that Crapo’s lung volume reference equations (Crapo RO, Morris AH, Clayton PD, Nixon CR. Lung volume in healthy nonsmoking adults. Bull Eur Physiopathol Respir 1983; 18: 419-425) were generated using a single-breath test.

      – Richard

  8. Hello Richard:

    I just wanted to say thank you for the time and energy you put forth in developing and maintaining your blog. You have been and continue to be a huge asset to the PFT community.

  9. Richard,

    I absolutely agree with the comments above, your blog is fantastic and a much needed resource for us “PFT-people”.

    I wonder if your or one of your readers could help me – I am currently on the look-out for equipment to replace our dry air challenge system. We do semi-standardized exerice testing in combination with dry air and have used an Aiolos asthma test for “dosing” the air, but need to find an alternative. After asking around and googling I have come up with nothing. Any advice on method or equipment is greatly appreciated.

    • Jenny –

      Could you tell me a bit more about how you perform your challenge testing and what you’re looking for? I found a couple of articles referencing the Aiolos asthma test but it appears to be nothing more than eucapnic hyperventilation (which is not a commonly performed test). Do you need to measure minute ventilation or do you need a new gas source or is it something different?

      – Richard

      • Sorry for being unclear.
        We let the patients run on a threadmill and breathe dry air at the same time, as a combination test where the aim (usually) is to look for exercise induced bronchoconstiction.

        The Asthma test equipment has been useful for setting a flow adapted to the patients size. After giving it some thought, I think it would probably do with a one way valve to the mouth piece and a large enough flow of dry air. Since the technical department is not too keen on non-standardized home built devices, I thought it could be worth it to ask arounfdthough. Thanks for responding!


  10. Hello –

    I am looking for the manual for a Spirotech S400 spirometer. I would also be interested in purchasing another dry rolling seal or fan type spirometer (as long as they have the manuals with them. Any suggestions? All the mechanical volume spirometers on eBay do not have the manuals with them (or the supplies).


    • Janet –

      The normal lifespan of PFT equipment is on the order of 7-10 years and most PFT manufacturers (assuming they are still in business) will not support equipment any older than that. You can try looking on and Both are used medical equipment re-sellers and occasionally older systems like the S400 come up for sale. Realistically however, SpiroTech ceased manufacturing somewhere around 15-20 years ago and trying to find manuals or parts is going to be very difficult. MEK and Associates appears to have bought the rights to the SpiroTech line of equipment. They sell the SpiroTech S780 and S700 and may be able to help (at least in terms of parts). If you have your heart set on a rolling-seal volume-displacement spirometer that will probably be supported (parts and manuals) for years to come, I’d look at Morgan Scientific’s SpiroAir and TransAir systems.

      I’m not sure what you mean by a “fan type” spirometer but if you’re thinking of a bellows spirometer like a Vitalograph then you’re out of luck since nobody is manufacturing this type of spirometer any more.

      – Richard

      • Thanks, I will look at MEK. I can still get pens and paper for my Spirotech, but I have to make my own paper for my Collins water seal spirometer. I need a spirometer that I can demonstrate leak testing on. I was trying to find an old Jones spirometer, but have been unsuccessful. It can be a dry rolling seal or a bellows, either one would be fine. I don’t need any more water seal spirometers, I’m tired of filling and emptying them all the time. If you know where I might find a Jones (or one like it), let me know.

  11. Hi Mr. Johnston,
    Nice work.
    In defining obstruction, how can we correlate the post bronchodilator Fev1/FVC ratio <70 (as per GOLD) with GLI Z-scores, which are based on the prebronchodilator values?

    • Sateesh –

      Comparing the GOLD and Z-score standards for airway obstruction is like comparing apples and oranges; they are not the same thing at all. GOLD uses an observed FEV1/FVC ratio of less than 0.70 as an indication of airway obstruction. The advantage of this is that it is completely independent of any reference equation and this matters because selecting the correct reference equations for different ethnicities (even when it’s Caucasian!) can be difficult. Where it fails is that it does not recognize that the FEV1/FVC ratio declines with age and for this reason it greatly overestimates the incidence of airway obstruction in the elderly and greatly underestimates in the the young. The Z-score, on the other hand, is tied to the standard error of the estimate (SEE) of a specific reference equation. A Z-score (for any specific reference equation) of -1.645 is, by definition, the LLN since it is the 90% confidence interval. The actual value of the Z-score and the LLN will therefore vary according to which reference equation you are referring to. The reason that the GOLD standard is only applied to the post-bronchodilator FEV1/FVC ratio is that it is specifically attempting to diagnose COPD where the assumption is that bronchodilators will not/cannot reverse the underlying airway obstruction. The GLI (or whatever reference equation you are using) Z-score of -1.645 is simply a useful working clinical definition of airway obstruction without regard to which condition is causing it and for this reason it doesn’t matter whether you are looking are pre- or post-bronchodilator results.

      My personal opinion is that neither is perfect but that the GOLD standard, most particularly since it fails to recognize the changes in the FEV1/FVC that occur with age, is actually considerably more misleading than the Z-score. The Z-score may be more “scientific” but its accuracy depends on selecting the right reference equation in the first place.

      – Richard

  12. I am a RPFT working in the state of NJ & NY.
    I work part time in the field. Recently, I have been looking for a full time position.

    I was contacted by a pulmonologist who wanted me to train his staff of medical assistants on the Carefusion/ VMAX pulmonary equipment.

    At first I was very flattered and excited about this offer.
    However, I realized expecting a medical assistant to do an accurate PFT study
    ( spirometry pre/post, sbDLCO and lung volumes) is not realistic. Medical assistants have NO training in respiratory care or the physiology of the lungs.

    In NJ, it is my understanding that you need to be licensed healthcare worker to give a bronchodialator.

    This MD wants to hire medical assistants to do PFT testing because their pay is
    significantly less the a RCP.

    I was recently made aware that this is not an isolated situation.
    I think it is wrong for anyone besides a RCP to do a full pulmonary test.
    When medical assistants are given the responsibility of doing this testing with no
    supervision……..standards will fall and the quality of care for patients will deteriorate.

    Does our association have laws about who should do pulmonary testing ?

    Your feed back would be greatly appreciated

    • Susan –

      New Jersey requires an individual to have an RRT or CRT in order to perform pulmonary function testing and this is fairly clearly stated in the New Jersey Administrative Code Title 13 Law and Public Safety Chapter 44F (page 6, item 12). Having said that I’ve yet to hear of any physician, clinic or hospital ever being brought to court over this issue anywhere in the country (may have happened, just never heard of it). I presume that this is occurring in the pulmonologist’s private offices and not in a hospital (since the Joint Commission at least would probably ding the hospital for it) and for this reason there is likely little recourse. The only institutions that are likely to care about this kind of situation are insurance companies since they would be paying for sub-par testing but even then I can’t see them getting overly excited since it is being done under the supervision of a board certified physician. So, it’s legally suspect, it’s morally and ethically reprehensible, and it certainly doesn’t say much about a pulmonary physician that is more interested in a revenue stream than test quality, but I think you’re going to have trouble finding anybody who cares.

      As far as the AARC is concerned pulmonary function testing is a niche specialty and I would guess that probably less than 5% of AARC members work full time in pulmonary function labs. Despite the fact that the AARC is the sole organization for pulmonary function personnel in the USA I do not think they’ve been particularly good advocates for our profession. The AARC has been good about getting laws passed to have pulmonary function testing performed by CRTs and RRTs, but not particularly good about including CPFTs and RPFTs in this. You have concerns about poorly educated and trained MA’s but there are many labs where RT’s with no training or prior experience in PFT’s are routinely rotated through PF testing and the quality of their testing is probably not going to be much better.

      The current sorry state of affairs in pulmonary function testing did not happen overnight. It’s taken decades of neglect to get here. It hasn’t been helped by the fact that many of those working in the field of pulmonary function testing do not consider it a profession, just something they’re doing for a while. And those of us that do remain in the field have been remarkably poor advocates for our profession.

      I don’t want to sound hopeless, however, since there are many people in our field who care deeply about test quality and this means you aren’t alone. My recommendation would be that you bring it to the attention of AARC’s advocate for New Jersey’s legislature and the New Jersey Society for Respiratory Care. Through them you can at least find out if they share any concerns about this type of situation.

      Regards, Richard

  13. In response to the issue of MA’s doing PFT’s…….
    I’m a retired RCPT/RPFT/RRT , been in the field since ’71. Before I retired the last 12-15 years was working for the private sector (care fusion, nee’ sensormedics, Collins, others, before that I managed the lab at a couple large MC’s in Seattle.

    When Pfizer started the clinical trial for inhaled insulin, Exubera, they had to do full PFT’s on all the people in the trial, thousands of subjects. They had 250 to 300 sites around the world testing subjects. Spiro, DL and Vols, pre and post BD.
    They made the decision, before they even chose the sites, not to use trained PFT
    techs. A deliberate decision, based on the idea that trained techs had “their own habits in doing tests”.

    I was in on those discussions with Pfizer and Collins, the vendor, and asked if they’d pick a plumber or doctor the same way, but that made no difference.
    I was asked, along with another RPFT, to design a two day program to teach totally untrained MA-type people to do full tests. Collins designed software that made the testing as simple as possible, and did a pretty good job.

    The two day training initially contained a half day of physiology and lung anatomy, the rest was hands-on testing of each other. After a few months we cut out the half day lecture, and made it a 30 minute brief talk. The results were the same., in terms of how many people passed the training.

    The results, after nearly two years testing and nearly 100K subject tests, were that roughly 80% of them met ATS standards.

    Did the ‘trained’ people know what they were doing? What the results meant? They knew if they were reproducible, because the software told them, but did they know if they were accurate? No to all questions.

    So, the answer perhaps to your question is ‘depends’. Do they have oversight that will QA/QC their work? Do the docs know enough to recognize data that looks screwy?
    The vendors/manufacturers with the help of people like me, have made the tests so easy to do and software that tells them if it meets ATS standards, we’ve worked our way out of the job. In some ways.

    I’m glad I retired when I did.

    Mike Mulligan

    • Phil –

      Water vapor, not liquid water. The partial pressure of water vapor in the lung (considered to be fully saturated at 37 degrees C) is nominally 47 mmHg. During exhalation the partial pressure of water vapor decreases as temperature decreases (hence the rain-out on pneumotach meshes) but is always above zero and must be taken into consideration when measuring the viscosity of exhaled air.

      – Richard

  14. Richard- I found your blog when I was looking for information on measuring CO2 response. I have a 17 year old with a novel mutation in the PHOX2B gene that has not been described before (so the clinical significance is unknown although it appears to be in a significant portion of the gene) and we are interested in measuring his CO2 response. He has some chronic lung disease and a trach but has been off the ventilator and there is some debate among our group whether he should receive nighttime ventilation. Your blog post on CO2 response testing suggests that if we used the rebreathing method we might have trouble interpreting it if I read it correctly. He clearly has an abnormal response since he walks around quite happily during the day with etCO2’s in the low 50’s!

    • Dennis –

      Measuring CO2 response for your patient would be problematic. The first problem is regardless of whether you’d be looking to measure changes in ventilation or the P100 pressure the fact the your patient is trached would make either kind of measurement difficult (airway resistance around/through the trach, pressure leaks around the trach). Second, there really aren’t any normal values. Almost all studies have compared groups against each other rather than against some kind of norm, so interpreting the results in a single patient in a one-off situation would be difficult.

      I assume you’re asking because you’re concerned your patient may be hypoventilating at night and retaining CO2. In a sense, it doesn’t matter what his CO2 response is partly because I don’t think that’s going to tell you whether or not he’s likely to hypoventilate. But partly also because if he is hypoventilating he is also becoming hypoxic and that can be measured relatively easily with a pulse oximeter. Unless he’s chronically hypoxic too?

      I would suggest that you look into a RIP (Respiratory Inductive Plethysmograph) system. If one’s available you can monitor his actual ventilation noninvasively with reasonable accuracy. Also, years ago (and because I haven’t been in an ICU in ages I don’t know if these are still around or not) bedside monitors included an “apnea” monitor that sent a HF signal through the ECG electrodes to monitor expansion/contraction of the chest. It wasn’t accurate in any way, but it did let you monitor the fact that the patient’s chest was expanding/contracting and gave a respiratory rate.

      I’m curious though. Do you ascribe his possible hypoventilation to the PHOX2B mutation or just to his chronic respiratory disease or are the two connected?

      Regards, Richard

  15. Perhaps you could help me, or point me to someone who can; I’ve been looking for more information about some pictures in a book I came across of some experiment (probably done in France, before 1960) involving a man in a head out plethysmograph device, though I’m not sure if it was for pulmonary fitness testing. I can send more information including pictures, but I thought I should ask first.

    • Peter –

      Take a look at this webpage on plethysmographs. Is it like the Haldane & Priestly plethysmograph (second picture) or the Mead & Emerson plethysmograph (sixth picture)? I will be interested in any photos or other additional information you may have.

      – Richard

      PS: I tried replying to your email address but it bounced.

  16. Hello! I would love to questioning u about something, if u could help me.

    Usually, in VO2, when authors says they exclude errant breaths (cough,sneeze, speak) by removing the values what are patters they are falling? Where i can read about this subject?

    • Ana –

      Generally a cough or sneeze shows up as very small tidal volumes and may elevate the apparent respiratory rate. Removing them (and the possibility of doing this depends on the software of the CPET system you’re working with) will reduce the respiratory rate but probably won’t change the minute ventilation, VO2 and VCO2 all that much. If the patient is able to talk then they’re not on the mouthpiece and the system is missing their respirations so removing that really isn’t in the cards (and you can’t add it back in either). This is from experience and I don’t remember reading this anywhere in particular. If you want to read up on exercise testing I’d suggest the ATS/ACCP CPET standards (Amer J Respir Crit Care Med 2003; 167(3): 211-277) or Wasserman’s textbook (‘Principles of exercise testing and interpretation’. Wasserman K, Hansen JE, Sue DY, Stringer WW, Whipp BJ, published by Lipincott, Williams & Wilkins. You can get a used copy of this on fairly inexpensively). Both are a little dry but to really understand exercise testing you’ve got to get the basics of physiology down-pat before it all starts to make any sense.

      Regards, Richard

  17. Hi Richard,

    So nice to stumble upon your blog! I am hoping you can help me. I am an RRT. Have been one for about 30 years. I also have asthma (since age 7). I perform methacholine tests twice a week. I do the 5 breath technique. I am trying to find information as to if this could be harmful to me (my lungs) as I have had a decline in my PFTs? Do you have any information/thoughts or know where I could find any info? Please let me know. Thanks!

    • Cyndi –

      I am unable to find anything in the literature about the effects of chronic occupational exposure to methacholine. FYI, my lab has had a policy of not allowing technologists with asthma to perform methacholine challenges. The ATS guidelines to methacholine challenge testing (woefully out of date and everybody has been waiting for the new standards to be released “any day now” for several years) state “The safety of both patients and technicians should be considered in the design of the test room and the testing procedures.” but do not provide any suggestions on how this should be done. I know that some PFT labs perform methacholine challenges in front of the intake for a HEPA filter to prevent exposure to aerosolized methacholine to anybody but the patient. I won’t say you shouldn’t be doing methacholine challenges but if you’re having to use your inhalers or other asthma meds more frequently after performing one then you should consider getting somebody else to do them.

      Best wishes, Richard

    • Lyle –

      You’re right, I somehow missed out on Rhode Island. I’ve searched the government website and although they do have licensure information about respiratory therapists, it’s almost entirely about licensure and continuing education, not scope of practice. In one sentence it does mention “spirometry testing” in the section on “Advanced knowledge and/or skills” but nowhere is there any language concerning a requirement that pulmonary function testing can only be performed by a CRT, RRT, CPFT or RPFT that I’ve seen in other states RT scope of practice. Unless somebody in Rhode Island can speak to this, I’ll have to go with licensure not being a requirement there.

      – Richard

  18. Richard, really enjoy your articles. I am a retired RPFT. I looked for articles on your blog about exhaled nitric oxide but could not locate any. What is your take on this testing device, usefulness as one of many diagnostic tools for following asthmatics?
    Thanks David

    • David –

      It’s one of the topics I’ve avoided, partly because I have no personal experience with it (although that hasn’t stopped me from writing on other subjects) but more because I think the evidence in it’s favor is both somewhat equivocal and not universally applicable to all asthmatics. There’s also the problem that what results you get are dependent on how you measure it. The current NO standards require that exhalation occurs at flow rates within a narrow target range and that’s because the amount of NO you measure changes with the expiratory flow rate and to me this raises the question of what exactly is being measured. I will agree that there is a relationship with airway inflammation and NO in some asthmatics, but not all of them, and I suspect that the differences are because in asthma there is probably a number of biochemical cascades from different genetic and environmental causes that all present similarly as airway hyperresponsiveness. (BTW, I would also bet that there is a strong relationship between an elevated NO, elevated exhaled air temperature and elevated DLCO in asthmatics but this a guess on my part and has not been studied). I’ll probably get around to discussing exhaled NO eventually but I keep finding other topics that I find more interesting.

      Regards, Richard

  19. Hi Richard,
    First i would like to thank you for your blog, very well made and fully interesting!
    I have a question concerning the justification of doing the post bronchodilator in spirometry. We always refer to the value of the pre FEV1 in % of the predicted value to evaluate the need of the post bronchodilator but after multiples discussions with colleagues and different center performing pulmonary function test it seem that there is different approach in the normal % of the pre FEV1 value. Some center use 90%FEV1 of the normal value and other use 80 or 85% FEV1 always in considering the FEV1/FVC ratio above 0.70. I cannot find in the 2005 ATS guidelines anything supporting the %pred FEV1 value to justify doing the the post- bd other than FEV1/FVC ratio and by my experience I have noticed patients to have a big response in the FEV1(above 12%) with a FEV1 above 90%pred but with a FEV1/FVC under 0.80 and considering that the value of the pre FEV1 is within the LLN. So my question is would it be more appropriate to take in reference the pre FEV1/FVC ratio than the % pred FEV1 to evaluate the need to do the post bd spirometry.
    Best regards!

    • Andre –

      You’re correct when you say that there are no ATS/ERS guidelines for performing post-BD spirometry based on FEV1 or the FEV1/FVC ratio. We sidestep this problem in my lab by not performing pre- and post-BD spirometry unless there is a physician order for it so I can’t share our guidelines since we don’t have any.

      Any guideline that is based on the presence of some airway obstruction, whether this is determined by the FEV1/FVC ratio, the percent predicted FEV1/FVC ratio, the LLN of the FEV1/FVC ratio, the FEV1 percent predicted or the FEV1 LLN is always going to miss those patients that do have a significant bronchodilator response even though the have reasonably normal spirometry. Another problem with any guideline for performing post-BD spirometry based on airway obstruction is that it shares the same problems with diagnosing airway obstruction in the first place (i.e. percent predicted, LLN or GOLD?).

      You could base your guideline on your department’s criteria for the diagnosis of airway obstruction but that pre-supposes that the only patients who will have a positive response to a bronchodilator are those with airway obstruction in the first place and we know that’s not true. One way around this would be to perform pre- and post-BD spirometry on every patient’s first visit, and then only with a physician order thereafter. Or, do what we do, only perform pre- and post-BD spirometry when there is a physician order for it (we do this partly because of concerns about possible legal issues but also because we couldn’t come up with a guideline that all of the pulmonary physicians would agree to).

      Regards, Richard

  20. Richard,
    Thank you for all you do for our PFT community! It is so nice to have a place to reference and others to talk to. I have 2 seemingly simple questions, yet I am unsure how to proceed.
    I do quarterly spirometries on a post Lung Transplant CF patient. I believe she is close to 10 years post transplant. During one of times she came in for testing, she stated that the lungs she received are from a male. Obviously our references are based off height, age, ethnicity, and gender. So, when I put her gender as female, are her references understated? It is something I didn’t find out until she already had multiple spirometries done, so I have not changed anything because I want the tests to be comparable percentage wise.

    My next question, which I have not encountered yet, is if a patient should come in in the future that is transgender, and they either inform us or it is in the chart for us to know, do we use the gender they were born as? I am afraid that patient’s would become offended that their “old” gender is being used. I am sure this will be an interesting and touchy subject in the future and I hope to be prepared for it.

    Thank you again for all you do!

    • Jessica –

      I’m not sure the gender of the lung that was transplanted matters all that much since it’s the recipient’s rib cage and the position of the diaphragm that will determine the maximum vital capacity. It is possible the FEV1 could be affected by the comparative sizes of the airways but since you don’t know the height and age of the donor lung it’s hard to say it would be any different than would be expected for the recipient. What I don’t know is how well a donor lung is supposed to match the recipient in terms of size. If it’s smaller it should expand to some extent, since that’s what happens to the remaining lung after a pneumonectomy. If it’s larger however, how much larger does it have to be before it’s “trimmed” back in size or is it ever? Regardless, I would think that the trends in FVC and FEV1 are more important for lung transplant patients than the percent predicteds.

      I’ve discussed transgender patients previously, but basically changing gender does not change lung characteristics and it is the original gender’s predicteds that need to be used. The biggest problem is in the patient demographics of PFT lab and hospital information systems. I think we should all be aware by this time that recording gender with the sole choices of Male or Female is not accurate even if only individuals who are intersex are considered (depending on how intersex is defined this is as many as 1 birth per thousand or even higher) let alone those who are transgender. I would suggest that all medical records at least have separate fields for an original/physiologic gender and a preferred/assigned gender.

      Glad you like the blog.

      Warm regards, Richard

  21. Richard,
    I have really enjoyed reading your blog and being new to the PFT community I have found a lot of helpful information here. I was recently hired to start a PFT lab in an out patient facility. I have prior PFT experience, but it was for a short period of time and inconsistently. I worked at a small hospital and we performed PFT’s on patients as they were scheduled and they were few and far between if that makes since. Since I have started our lab I have gotten some help from other facilities and the manufactures of our equipment. I am still learning a lot and generally only see maybe five patients a week. I have seen you post about biological quality control and I was wanting to see if you could provide me with some information about it. I am the only respiratory therapist in my office so it is to difficult to perform quality control on myself. I could perform it on one of the medical assistance I work with but we have a pretty high turn over rate and I am confused on weather it needs to be the same patient consistently or not. I don’t mean to sound misinformed, I am just wanting to make sure I am putting out accurate testing and that I am doing everything I need to do to make sure my lab runs correctly. It is just difficult when you don’t have anyone to train you or to pass along current protocols. I have pretty much had to do everything from scratch. I would appreciate any information you could send me or any advice you could provide! Thank you! Jessica

    • Jessica –

      Quality control is documented and analyzed using Levey-Jennings charts which are easy to set up using any spreadsheet software. However, recommendations are that you use at least 12 test results to generate the baselines for +/-1SD and +/-2SD. Since you have so much turnover in MA’s they don’t seem to be a good option for you but I’m not sure why you don’t think you can do the tests on yourself. I did my own QC for years and only needed assistance with plethysmographic lung volumes. Is it an issue of where the test system controls are placed versus where you have to sit to do the tests?

      Regards, Richard

      • Yes, I do not have a button set up with my pft machine and have to use the F1 on my key board. I thought about asking one of the girls I work with to just press the button for me and I can turn the screen to see the prompts.

  22. Richard

    I have to say I’ve learned so much after reading your blog. I would recommend anyone to read it, very educational and useful on various levels. I’m a inventor and a Sarcoidosis Patient/Oxygen user. Thank you for sharing your many years of experiences.

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