What Causes Low DLCO?

Posted on Sat, 2 Apr 2016

Medically reviewed by Ask A Doctor - 24x7 Medical Review Team

Sat, 2 Apr 2016 Answered on

Thu, 2 Jun 2016 Last reviewed on

Question : I had a pulmonary function test done and my doctor told me I had a low DLCO. I had a CT scan and it was negative for PE or fibrosis. I am not anemic. What other things could cause this? Also is a low predictive value for residual volume (70% of predicted) and VE XXXXXXX (58% of predicted) significant? Could you please explain what a VE XXXXXXX (peak ventilatory response) is? My oxygen stats are normal. All other things are normal on the test, except a flat blood pressure response. My main complaints are SOB with activity, having to take in deep breaths when active (it takes effort almost like I have a plastic bag over my head) and tachycardia when going up stairs and inclines. I used to exercise regularly but over the past year my activity has gradually decreased due to symptoms.

Answered by Dr. Drkaushal85 (7 hours later)

Brief Answer:
Do you smoke?

Detailed Answer:
Thanks for your question on Healthcare Magic.
I can understand your concern.
Your low DLCO is mostly due to right to left shunt.
Low DLCO means oxygenation is low.
Since your CT scan is normal, we can rule out lung pathology.
Right to left shunt in heart can cause mixing of deoxygenated blood with oxygenated blood.
And this can give rise to low DLCO.
Your low residual volume and VE XXXXXXX are low.
RV (residual volume) is amount of air remain in the lungs even after maximal forceful expiration.
VE XXXXXXX is maximal volume expired during maximal exercise (effort).
So if your VE XXXXXXX is low then RV should be high.
And if VEmax is high then RV should be normal.
So I think you might have low effort in performing PFT (pulmonary function test). This might give you lower values.
Please let me know, do you smoke?
I will be happy to help you further. Wish you good health. Thanks.

Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar

Follow up: Dr. Drkaushal85 (14 minutes later)

I do not smoke. I gave it my all when performing the test. I had an echo done and it said a minimal left to right shunt, no right to left shunt with bubble test. Normal O2 stats with exercise. The doctor did not say anything about the RV. It just said it was less than predicted value. What would cause a low VE XXXXXXX and do you ever consider it significant? The only other thing they doctor said is I had a flat blood pressure response to exercise.

Sorry I was confused. I guess the low RV was on the PFT but the VE XXXXXXX was low on the exercise test.

Answered by Dr. Drkaushal85 (10 hours later)

Brief Answer:
Sorry for late reply.

Detailed Answer:
Thanks for your follow up question on Healthcare Magic.
I can understand your concern.
Sorry for late reply.
In my practice, I consider low RV significant only when patient is smoker or patient is in need for lung resection.
In non smokers, as such there is no much role of RV.
Same true with VE XXXXXXX It is also not much significant.
Please let me know
1. What were your FEV1, FVC and FEV1 /FVC ratio?
2. How's your lung parenchyma on CT?
Please reply me answers of above asked questions, so that I can guide you better. I will be happy to help you further. Wish you good health. Thanks.

Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar

Follow up: Dr. Drkaushal85 (10 hours later)

They were all ok, CT was good too. My shortness of breath seems to be more cardiac related I guess. The only thing that was mentioned on both PFTs was the reduced DLCO. I am going to get a right heart XXXXXXX with exercise. Thanks for the info!

Answered by Dr. Drkaushal85 (31 minutes later)

Brief Answer:
Yes, cardiac issue is more likely in your case.

Detailed Answer:
Thanks for your follow up question on Healthcare Magic.
I can understand your concern.
Yes, you are right. Possibility of heart related cause is more likely in your case.
Since your FEV1, FVC, and FEV1/FVC are normal, no need to worry for lung disease despite of low DLCO.
Do let me know your diagnosis and progress as I am eager to know it.
Hope I have solved your query.
If you are not having further queries, then please close the conversation and rate my answer.
You can ask me directly on bit.ly/askdrkaushalbhavsar.
Wish you good health. Thanks.

Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar