Categories: Respirology/ ICU

PFTs: What is pseudorestriction?

Sometimes when interpreting spiromtery, a patient may have what appears to be a mixed obstructive/ restrictive picture. (Reduced FEV1/FVC and Reduced FVC).

Patients with an obstructive process (i.e COPD) may have gas trapping, which will reduce their FVC due to increased residual volume (RV). This may falsely lead a clinician to interpret it as a mixed obstructive/ restrictive process, while it is truly just obstructive.

NOTE: The next step to confirm pseudo-restriction, is to get a TLC. If normal (and therefore not restrictive) it highly suggests this pathology. Also look at the RV and RV/TLC ratio.

REFERENCES

  1. Sorino, C et al. Physician’s mistakes in the interpretation of spirometry. European Respiratory Journal 2012 40: P1131
  2. Ranu H, Wilde M, Madden B. Pulmonary Function Tests. The Ulster Medical Journal. 2011;80(2):84-90.
  3. As-Ashkar, F, Mehra, R, Mazzone, PJ. Interpreting pulmonary function tests: recognize the pattern, and the diagnosis will follow. Cleve Clin J Med. 2003;70:866–881.
Get Medical Pearls directly to your inbox every week!
Weekly posts with high yield medical knowledge, directly to your mailbox!
Dr. C Humphreys

Internal Medicine

Recent Posts

Older Age and Obstructive Sleep Apnea (OSA): Mechanism

Older age is recognized as a risk factor for obstructive sleep apnea.[1] But why? Suspected…

1 month ago

How does Weight Affect Obstructive Sleep Apnea (OSA): Mechanism

Being overweight (BMI ≥ 25 kg/m2)/Obese (BMI ≥ 30 kg/m2) is one of the most…

1 month ago

Nocturia and OSA: Mechanism

Nocturia is a common symptom associated with obstructive sleep apnea. [1] Img Cred: Am J…

1 year ago

ASD vs. VSD Murmur Difference

ASD (Atrial Septal Defect) Wide, Fixed split S2 (in contrast to the normal variation in…

1 year ago

Mechanism of a Mixed Apnea

Mixed apneas are characterized by absent respiratory effort and airflow in the first section of…

2 years ago

How Does Hypothyroidism Cause Hypoventilation?

Although rare, the differential diagnosis of hypoventilation and hypercapnia respiratory failure includes hypothyroidism. It is…

2 years ago

This website uses cookies.