Respiratory Investigation — Viva Defence

Opening statement (SASPOP, delivered aloud)

"Mrs Marsh is a 63-year-old never-smoker with 14 months of progressive exertional dyspnoea, dry cough, Velcro crackles and early clubbing — a presentation I would frame as suspected fibrotic interstitial lung disease until proven otherwise. My problems are: first, confirming and staging the physiological severity of what is likely a restrictive, gas-transfer-impaired lung disease; second, establishing the radiological and, if needed, histological pattern, because pattern determines treatment; third, hunting an underlying cause — connective tissue disease, drug or exposure-related; and fourth, doing all of this through the least invasive sequence that still answers each question. I would like to begin with full pulmonary function tests and an HRCT, then bring her to a multidisciplinary discussion before any tissue diagnosis is considered." [1]

Structured problem list

1. Progressive dyspnoea with Velcro crackles and clubbing — fibrotic ILD is the working diagnosis; the differential includes hypersensitivity pneumonitis, connective-tissue-disease-related ILD and drug-induced fibrosis [1].
2. Unquantified physiological severity — no baseline numbers yet; severity and progression are tracked with PFTs, especially DLCO.
3. Unknown pattern and cause — radiological pattern (UIP versus non-UIP) and serological/exposure workup are pending; both change treatment.
4. The tissue question — whether BAL, cryobiopsy or surgical biopsy would change management, weighed against procedural risk in a possibly fibrotic lung [3].

Integrated management plan (the investigation chain, defended)

• Full pulmonary function tests first: spirometry with a flow-volume loop, lung volumes and haemoglobin-adjusted DLCO. I expect a restrictive spirometric pattern confirmed by a low TLC with a disproportionately low DLCO — but I insist on the TLC before I ever say the word "restriction", and on haemoglobin adjustment before I interpret the DLCO [1] [2].
• HRCT chest next: it defines the pattern — usual interstitial pneumonia, probable UIP, or an alternative such as NSIP or hypersensitivity pneumonitis — and a confident UIP pattern in the right context can make tissue diagnosis unnecessary [1].
• Cause hunt in parallel: connective tissue disease serology, a meticulous drug and occupational/avian/mould exposure history, and baseline oxygenation assessment (walk test) for prognostic staging.
• Multidisciplinary discussion before tissue: BAL cellular analysis in selected phenotypes (for example, to support hypersensitivity pneumonitis or exclude infection), with transbronchial cryobiopsy or surgical lung biopsy reserved for the case where histology would change treatment — not as a reflex [3].
• Then management and monitoring: antifibrotic or immunomodulatory therapy per the final diagnosis, with serial PFTs and DLCO to track trajectory and treatment response [2].

Probing questions with model answers

"Why PFTs before the CT? Surely the scan gives you more?" — "They answer different questions, and I need both. The CT gives pattern and distribution; the PFTs quantify severity and give me the baseline against which every future decision — progression, treatment response, transplant timing — is measured. DLCO in particular is often the earliest abnormal number in ILD and the most sensitive to change. I would order them together, but I interpret the scan in the light of the physiology" [1] [2].

"Her spirometry shows an FVC of 65% with a normal ratio. Restrictive lung disease?" — "Not yet. That is a spirometric pattern consistent with restriction — it could also be a submaximal effort, obesity, or early neuromuscular disease. Restriction is a TLC diagnosis, so I would confirm with lung volumes, and then use DLCO to separate parenchymal restriction, where gas transfer falls, from extrapulmonary restriction, where the membrane is intact and KCO is preserved or high" [1].

"When would you take her to bronchoscopy?" — "For two defined reasons. BAL, if the HRCT and serology leave the phenotype uncertain — a lymphocytic cellular pattern would support hypersensitivity pneumonitis, and BAL also excludes infection before any immunosuppression. And EBUS-TBNA, not mediastinoscopy, if she had mediastinal or hilar nodes that needed sampling — endosonography is first-line there, and in sarcoidosis it roughly doubles the granuloma yield of conventional bronchoscopic biopsy. What I would not do is bronchoscope her without a question the result would answer" [3] [4].

"Would you biopsy her lung?" — "Only through the multidisciplinary meeting, and only if the answer changes treatment. If HRCT and serology give a confident UIP pattern, biopsy adds risk without changing management — I would not do it. If the pattern is indeterminate and she is fit, I would discuss transbronchial cryobiopsy or surgical lung biopsy, being explicit about the risk of precipitating an acute exacerbation in a fibrotic lung" [3].

"How will you follow her?" — "With serial physiology, not serial radiation: FVC and DLCO every three to six months, a walk test for oxygenation, and symptoms and exacerbations as clinical anchors. A declining FVC or DLCO trajectory is itself a treatment decision point, and it is far more sensitive to change than repeating CTs" [2].

Communication points

• Explain the chain to the patient: "Each test answers one question — the breathing tests measure how much work the lungs can do, the scan shows what pattern the disease has, and only then do we decide whether a sample of lung would change your treatment."
• Consent for any bronchoscopy covers sedation, the specific risks of the planned sampling (bleeding with biopsy, pneumothorax with transbronchial sampling), and the possibility of a non-diagnostic result [3].
• A fibrotic ILD diagnosis is life-changing news: deliver the working diagnosis honestly, name the uncertainties, and set the expectation of a defined answer after the multidisciplinary review — with early discussion of goals and support needs rather than crisis-driven conversations.