Trip Answers

Question answered:16/05/08

Unfortunately, we cannot answer this question.

 

We searched the NLH Respiratory Specialist Library and the TRIP and Medline databases but found no guidelines or studies to help answer this question.

 

However, during the course of our literature search we did locate the following information of a general nature that may be of interest.

 

In an e-Medicine article on pulmonary function testing, McCarthy discusses causes of obstructive and restrictive defects as indicated by spirometry testing. He does not specifically mention how pulmonary emboli might change parameters measured by spirometry.

 

“Obstructive defects: Disproportionate reduction in the FEV1 as compared to the FVC (and therefore the FEV1-to-FVC ratio, also called FEV1%) is the hallmark of obstructive lung diseases. This physiologic category of lung diseases includes but is not limited to asthma, acute and chronic bronchitis, emphysema, bronchiectasis, cystic fibrosis, pneumonia, alpha1-antitrypsin deficiency, and bronchiolitis. The expiratory flow at any given expiratory volume is reduced. The mechanism responsible for the reduction in airflow can be bronchial spasm, airway inflammation, increased intraluminal secretions, and/or reduction in parenchymal support of the airways due to loss of lung elastic recoil.
Restrictive defects: Reduction in the FVC with a normal or elevated FEV1-to-FVC ratio defines the classification of restrictive lung diseases as assessed by spirometry. Because the FEV1 is a fraction of the FVC, it also is reduced, but the FEV1-to-FVC ratio is preserved at a normal or elevated level. Measuring the TLC and residual volume (RV) can confirm restriction suggested by spirometry...
A reduced FVC on spirometry in the absence of a reduced FEV1-to-FVC ratio suggests a restrictive ventilatory problem. An inappropriately shortened exhalation during spirometry can (and often does) result in a reduced FVC. Causes of restriction on spirometry include obesity, cardiomegaly, ascites, pregnancy, pleural effusion, pleural tumors, kyphoscoliosis, pulmonary fibrosis, neuromuscular disease, diaphragm weakness or paralysis, space-occupying lesions, lung resection, congestive heart failure, inadequate inspiration or expiration secondary to pain, and severe obstructive lung disease.” [1]

 

In addition, we found one small study examining microembolism and its role in COPD exacerbation. The authors report in the abstract of the article:

 

“Pulmonary embolism often coexists with chronic obstructive pulmonary disease (COPD) and it is difficult to diagnose because of similar clinical symptoms. IN OUR STUDY: To try to answer the question if basic laboratory investigations reveal hypercoagulability and if so, if it has any impact on the course of COPD exacerbation. MATERIAL AND METHODS: 28 patients (11F, 17M) with COPD exacerbation were enrolled to the study. Hematocrit, hemoglobin concentration, platelet count, the level of fibrinogen and D-dimers and arterial blood gases were investigated. Lung function was assessed by spirometry. Risk factors of pulmonary embolism, the number of COPD exacerbation in the past 12 months and the exacerbation triggering factors were established with the help of a questionnaire. RESULTS: On admission, abnormalities of the analysed parameters were found in 18 patients. This group was compared with the rest of the study group. There were no statistically significant differences in arterial blood gases and spirometrical values. There was a differences in the level of fibrinogen and D-domers. CONCLUSIONS: The data suggest that in some patients COPD may be accompanied by intravascular coagulation but the influence of this process on the course of the exacerbation is unclear. Further studies on hemostasis impairment and its impact on exacerbation in patients with COPD are required.” [2]

 

Given the lack of specific and robust information to answer this question, we would recommend seeking further assistance from a local specialist.

 

References
1. McCarthy K. Pulmonary function testing. November 2006.
(http://www.emedicine.com/med/topic2972.htm)
2. Karwat K, Koœciuch J and Chazan R. [Is microembolism present and is it important element of COPD exacerbation?]. Pol Merkur Lekarski. 2005 Apr;18(106):385-8. (http://www.hubmed.org/display.cgi?uids=16161916)

---

DISCLAIMER: TRIPanswers is a collection of clinical questions and answers.  Each provider will have their own methodology in answering questions and these are likely not to be as rigorous as systematic review.  If you have any doubt as to the implications of this contact the Q&A Service Provider for further information. This document is presented for information purposes only. This document cannot and should not be used as a basis of diagnosis or choice of treatment, and is in no way intended to replace professional medical care or attention by a qualified practitioner. TRIPanswers and TRIP Database Ltd are not responsible or liable for, directly or indirectly, ANY form of damage whatsoever resulting from the use/misuse of information contained in or implied by this document.  Also, ensure you have read the terms and conditions for using the site.