Respiratory Investigation: PFTs, Bronchoscopy and Thoracoscopy

The answer first

Respiratory investigation is question-driven, not panel-driven. Every test in this topic answers one named question, and the consultant-level skill is stating the question before stating the test: Is this obstruction or restriction? (spirometry plus lung volumes). Is the gas-transfer membrane diseased? (DLCO). Is this asthma with normal spirometry today? (bronchoprovocation). What is this node, nodule or effusion made of? (bronchoscopy, EBUS or pleural biopsy). The examiner's favourite trap is the candidate who orders everything and interprets nothing ^[1].

Three rules carry you through most DWE questions and every data station ^[1]:

1. Spirometry diagnoses obstruction; it can only suggest restriction. A low FEV1/FVC ratio (below the lower limit of normal) is obstruction. A low FVC with a preserved ratio is suspected restriction — but restriction is a diagnosis of lung volumes, confirmed only when the total lung capacity is low ^[1].
2. DLCO is the membrane test — and it lies when haemoglobin is abnormal. Interstitial lung disease, emphysema and pulmonary vascular disease lower it; asthma, obesity and alveolar haemorrhage raise it; and anaemia lowers the measured value without any lung disease at all, which is why haemoglobin adjustment is built into the standard ^[4].
3. Tissue questions are answered by the least invasive route that reaches the lesion. Mediastinal nodes go to EBUS-TBNA first (not mediastinoscopy), peripheral nodules to navigational or radial-EBUS bronchoscopy, and unexplained exudative pleura to image-guided biopsy or medical thoracoscopy ^{[10] [17]}.

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References18ShowHide

1. [1]Stanojevic S, Kaminsky DA, Miller MR, et al. ERS/ATS technical standard on interpretive strategies for routine lung function tests Eur Respir J, 2022.PMID 34949706
2. [2]Graham BL, Steenbruggen I, Miller MR, et al. Standardization of Spirometry 2019 Update. An Official American Thoracic Society and European Respiratory Society Technical Statement Am J Respir Crit Care Med, 2019.PMID 31613151
3. [3]Pellegrino R, Viegi G, Brusasco V, et al. Interpretative strategies for lung function tests Eur Respir J, 2005.PMID 16264058
4. [4]Graham BL, Brusasco V, Burgos F, et al. 2017 ERS/ATS standards for single-breath carbon monoxide uptake in the lung Eur Respir J, 2017.PMID 28049168
5. [5]Wanger J, Clausen JL, Coates A, et al. Standardisation of the measurement of lung volumes Eur Respir J, 2005.PMID 16135736
6. [6]Coates AL, Wanger J, Cockcroft DW, et al. ERS technical standard on bronchial challenge testing: general considerations and performance of methacholine challenge tests Eur Respir J, 2017.PMID 28461290
7. [7]Crapo RO, Casaburi R, Coates AL, et al. Guidelines for methacholine and exercise challenge testing-1999. This official statement of the American Thoracic Society was adopted by the ATS Board of Directors, July 1999 Am J Respir Crit Care Med, 2000.PMID 10619836
8. [8]Miller RD, Hyatt RE. Evaluation of obstructing lesions of the trachea and larynx by flow-volume loops Am Rev Respir Dis, 1973.PMID 4745245
9. [9]Du Rand IA, Blaikley J, Booton R, et al. British Thoracic Society guideline for diagnostic flexible bronchoscopy in adults: accredited by NICE Thorax, 2013.PMID 23860341
10. [10]Yasufuku K, Pierre A, Darling G, et al. A prospective controlled trial of endobronchial ultrasound-guided transbronchial needle aspiration compared with mediastinoscopy for mediastinal lymph node staging of lung cancer J Thorac Cardiovasc Surg, 2011.PMID 21963329
11. [11]von Bartheld MB, Dekkers OM, Szlubowski A, et al. Endosonography vs conventional bronchoscopy for the diagnosis of sarcoidosis: the GRANULOMA randomized clinical trial JAMA, 2013.PMID 23780458
12. [12]Folch EE, Pritchett MA, Nead MA, et al. Electromagnetic Navigation Bronchoscopy for Peripheral Pulmonary Lesions: One-Year Results of the Prospective, Multicenter NAVIGATE Study J Thorac Oncol, 2019.PMID 30476574
13. [13]Light RW, Macgregor MI, Luchsinger PC, Ball WC Jr. Pleural effusions: the diagnostic separation of transudates and exudates Ann Intern Med, 1972.PMID 4642731
14. [14]Heffner JE, Brown LK, Barbieri CA. Diagnostic value of tests that discriminate between exudative and transudative pleural effusions. Primary Study Investigators Chest, 1997.PMID 9106577
15. [15]Romero-Candeira S, Fernández C, Martín C, et al. Influence of diuretics on the concentration of proteins and other components of pleural transudates in patients with heart failure Am J Med, 2001.PMID 11403751
16. [16]Heffner JE, Brown LK, Barbieri C, DeLeo JM. Pleural fluid chemical analysis in parapneumonic effusions. A meta-analysis Am J Respir Crit Care Med, 1995.PMID 7767510
17. [17]Metintas M, Ak G, Dundar E, et al. Medical thoracoscopy vs CT scan-guided Abrams pleural needle biopsy for diagnosis of patients with pleural effusions: a randomized, controlled trial Chest, 2010.PMID 20154079
18. [18]Havelock T, Teoh R, Laws D, Gleeson F. Pleural procedures and thoracic ultrasound: British Thoracic Society Pleural Disease Guideline 2010 Thorax, 2010.PMID 20696688