Question about PFT

Status
Not open for further replies.

KimT

Extremely helpful member
Forum Supporter
Joined
Nov 18, 2014
Messages
4,873
Reason
PALS
Diagnosis
08/2015
Country
US
State
South
City
The Beach
My FVC has increased slightly since 2014 but my total lung volume went down and then stayed at 60-70 for the past year.

My MVV is at 95% It was 120% in 2014 but it varies. 95% is the lowest. After the 95% was done, I did one that was 118%.

Why is my PI max negative? I'm not short of breath, even lying on my back.

I'm hoping Laurie can give me an answer.

I did the slow FVC (not sure what it's actually called but it is breathing out slowly, then in slowly and that was 95%.

Attached is my last test, done in December.
 

Attachments

  • scan0001.jpg
    scan0001.jpg
    27.4 KB · Views: 417
The big number we tend to look at is FVC, the top number. It says 77%. Not awesome, but not worrysome either. Below 50 and we are looking bipap, feeding tube, that sort of thing. Having said that, You can stay at that level for a long time. You can also be in the low 30s and not feel air hunger. The PI max is a negative becaues you are drawing air in, negative pressure.It is a strange disease.
Vincent
 
I'm more interested in my respiratory muscle strength since my FVC has been about the same for two years.
Also, my surpine FVC is the same as sitting or standing.
 
The big number we tend to look at is FVC, the top number. It says 77%. Not awesome, but not worrysome either. Below 50 and we are looking bipap, feeding tube, that sort of thing. Having said that, You can stay at that level for a long time. You can also be in the low 30s and not feel air hunger. The PI max is a negative becaues you are drawing air in, negative pressure.It is a strange disease.
Vincent

So does that mean I'm at 213% ABOVE normal for my PI max? I just don't understand why the Reference is 73 and my actual is (155). It looks like the expected is a positive number and my actual is a negative number.
 
Expected PImax number is negative as Greg notes but often on reports shows as positive due to poor app design. No way yours is 155. I'd completely discount it.
 
But what would (155) mean?

The technician repeated it 10 times and repeated my PE max 5 or 6 times. He made me squeeze my cheeks a few times.
 
That's the thing. It's meaningless. It can't be that far outside range. It's a mouthpiece test so I can only presume it was done or recorded incorrectly, perhaps with the wrong mouthpiece for you or the wrong switch flipped -- I don't know. Disappointing not to see a SNIP value, where there are data to suggest complementary prognostic value in ALS.

For those who may be browsing the scan, note the test values in parens are not "negative," they are just the ones below predicted range. I really hate that format.

To Vincent's post, I also wanted to add color commentary that increasingly ~75% rather than 50% FVC is seen as a threshold for considering BiPAP, and that the position of the stomach is more important than FVC for a RIG (feeding tube placed in radiology) since PAP can be used during the procedure and studies have shown safety in that scenario.
 
Kim, I think your mip and mep are more indicative of diaphragm and accessory muscle function.
 
Yes, but it appears the tech made a mistake in my MIP. I think he might have plugged the MEP into it somehow. It doesn't make sense in light of my MVV being so high (95 was the lowest and a subsequent test showed 120%)

I'm so disgusted I ordered medical equipment so I can test myself. No more PFT in hospital for me. My FVC is just as good lying down as it is sitting or standing. The only number that worries me is my total lung capacity and I'm using a cough assist machine and inspiratory training device to see if I can get it up. I've always been a shallow breather and slow breather.
 
Also, the machine I ordered will do the SNIP value with less than + or - 5%.
 
Hi Kim,

Knowing PFT/spirometry numbers does no harm if it is not an effort, but none is reliably correlated with near-term progression as yet. We say treat the patient, because as we have seen here, PALS here with similar FVCs have vastly different clinical pictures (e.g. of two people with the same FVC, one might not be on BiPAP at all and another might be on it nearly full time) based on differences in which muscles are driving the numbers, and their other symptoms. We also see that bulbar dysfunction skews the numbers quite a bit, as can simple pre-existing things like blocked sinuses. Thus, the delta between intervals is in truth non-linear.

Best,
Laurie
 
Steph, the MIP and PImax are the same thing, as are MEP and PEmax.
 
So I did a SNIP test with my new toy. It was between 110 and 120 which looks to be very strong. It was stronger than Fred's. I did it multiple times in each nostril and used the reference range I found online. The serial number on the software is not plugging in correctly so I have to call the company tomorrow.

My MIP was also way above normal.
 
Hi

If your FVC (forced vital capacity) is 77% of predicted and hasn't significantly changed in two years then it would indicate that your respiratory muscle status is stable at this time and therefore you should have not a reason for concern. In contrast, a trend of decreasing FVC over time would mirror the decline of respiratory muscle strength in ALS. I wouldn't be concerned about total volume changes since they are not a good marker for respiratory muscle strength and are mostly affected by lung disease, obesity and many other factors that are not relevant to ALS.
Your FVC value will decline if your muscles involved in expiration or inspiration significantly weaken, although pulmonary disease such as asthma, COPD or interstitial pulmonary fibrosis would also cause a decrease in FVC.
The maximum inspiratory pressure MIP (PImax) and SNIP values primarily reflect diaphragm muscle strength in ALS and are the most sensitive tests for early detection of weakening of the diaphragm. Your MIP and MEP values are essentially normal, ignore the parentheses that they are outside of the normal range, but they do not represent numerically negative values
Your PEF (PEFR) of 115% of predicted as well as your normal MVV (96%) support that your respiratory muscles are functioning adequately or you would not be able to achieve such values. In addition, if you have no shortness of breath at rest, lying down, and during moderate exertion this would support that you do not have a significant decline in your respiratory muscle strength and therefore you need not be worried about declining respiratory function at this point.
The accuracy of pulmonary function results is dependent upon proper calibration of the equipment, the pulmonary function technician's ability to get the greatest effort possible from the patient, the patient's ability to maintain a good seal around the mouthpiece, and finally patient’s cooperation. Any problem with the foregoing will affect the validity of the results.

If you plan to do pulmonary function testing on yourself I suggest that you also purchase calibration equipment and practice your maneuvers until they are consistent however, I do think that performing too much testing at home could lead to a lot of anxiety and that you would be better off having your pulmonary function tests performed in a professional environment. If you still have concerns about this matter I suggest you go to a different pulmonary lab, preferably one at a university hospital, and get a second opinion.
I am curious about the Brand of equipment you plan to use at home and if it meets ATS standards? I have used a simple and inexpensive peak flow meter and oximeter to keep objective track of my respiratory function at home since they will able to help me to objectively keep track of what is going on should I sense that my breathing has deteriorated.


Best wishes

Eliot
 
My home assessment equipment is professional grade and recommended by a pulmonary doctor who is a friend. The disposable mouthpieces are pre-calibrated. The results were very close to what they measured at my last test. I'm confident that I have good equipment.....especially after I get the software loaded.

I've had PFT done at Mayo Clinic and Johns Hopkins as well as Florida Hospital.

For me, there is more anxiety in not knowing. I also do periodic grip strength testing.

I understand that many people prefer not to know or not to dwell on it. I'm focused on keeping measurements for as long as I can because I've started inspiratory strength training based on results of a clinical trial. I'm also using a cough assist machine to help expand my lungs.
 
Status
Not open for further replies.
Back
Top