Radiology Rounds – 2/22/22

This week we’re sharing a distinct radiology pattern on chest X-ray and CT scans that should raise its own differential. Make sure to listen to our case episode next week to hear more about this patient and the diagnostic workup.

References and links for further reading

  1. Raoof S, Amchentsev A, Vlahos I, Goud A, Naidich DP. Pictorial essay: multinodular disease: a high-resolution CT scan diagnostic algorithm. Chest. 2006;129(3):805-815. doi:10.1378/chest.129.3.805
  2. Sharma BB. Miliary nodules on chest radiographs: A diagnostic dilemma. Lung India. 2015;32(5):518-520.
  3. Threadcraft MA, Case R. Vape-Associated Pulmonary Injury (VAPI) Presenting With a “Miliary” Pattern on Imaging. Cureus. 13(2):e13385. doi:10.7759/cureus.13385
  4. Purek L, Laroumagne S, Dutau H, Maldonado F, Astoul P. Miliary mesothelioma: a new clinical and radiological presentation in mesothelioma patients with prolonged survival after trimodality therapy. J Thorac Oncol. 2011;6(10):1753-1756. doi:10.1097/JTO.0b013e31822e295a

9. Top Consults: Interstitial Lung Disease Diagnosis

This week we are absolutely thrilled to be joined by three Interstitial Lung Disease experts to discuss the workup and differential for a patient with a new presentation of suspected ILD. This is also our first episode in a collaboration between the Pulm PEEPs and the American Thoracic Society Clinical Problems Assembly. In a series of episodes, we will be joined by pulmonary experts from around the country who are leaders in the ATS CP Assembly to provide content on common and cutting-edge topics in PCCM.

Meet Our Guests

Sonye Danoff is an Associate Professor of Medicine at Johns Hopkins and is Co-Director of the John Hopkins Interstitial Lung Disease and Pulmonary Fibrosis program. She also serves as the Assembly Chair of the Clinical Problems Assembly for the American Thoracic Society.

John Kim is an Assistant Professor of Medicine at UVA and has both clinical and research expertise in interstitial lung disease with a focus on pulmonary fibrosis.

Shweta Sood is an Assistant Professor of Medicine at Penn Medicine whose expertise is in Interstitial Lung Disease. She is an integral part of fellowship training where she leads the monthly ILD conference for fellows as well as provides didactics for ILD cases.

Consult Patient

A 66-year-old man who is a never smoker with a past medical history of hypertension and osteoarthritis was admitted to the hospital after presenting with progressive dyspnea on exertion to dyspnea at rest and was found to be hypoxemic. He reports 4 months of progressive dyspnea on exertion but on further questioning, thinks he was last normal about 1.5 years ago when he could walk 2 miles at a time. Currently, he can only walk 0.25 to 0.5 miles before needing to stop. He reports an intermittent, dry cough throughout the day that is not associated with eating, position, or sleeping. A full ROS is negative including for rashes or joint pains. His family history is notable only for hypertension and hyperlipidemia. He is a never smoker, drinks in moderation 1-2 x a week, and lives in the suburbs with his wife. His house has central heating and air conditioning, they have no pets, and they have carpeted floors. He is a retired police detective.

His physical exam is notable for fine crackles at the bilateral bases on pulmonary auscultation, and he is breathing comfortably on nasal cannula although mildly tachypneic to 18 breaths per minute. He has no signs of volume overload, no peripheral clubbing, no rashes, and joint exam does not reveal swelling or synovitis.

Key Learning Points

Take away points from our guests:

— ILD is a symptom, not a diagnosis

— The first time a patient is evaluated for interstitial lung disease is the best chance for making the diagnosis so take the time to evaluate them thoughtfully

— Start the physical exam with the hands first. The hands can reveal a lot about the patient (clubbing, cyanosis, joint, skin, and nailbed findings) and it establishes a personal connection

— When doing the pulmonary exam, percuss first from top to bottom to learn the size of the lungs, and then listen from bottom to top

— When reading a CT scan the simplest approach is “Is it a UIP pattern or not?”. This can be your first diagnostic divide. UIP is consistent with IPF, and in select circumstances connective tissue disease, occupational lung disease, or advanced hypersensitivity pneumonitis. Non-UIP patterns have a broader differential

— A multi-disciplinary interstitial lung disease conference is the gold standard for establishing an ILD diagnosis

Gathering the history:

— Ask about onset: acute or chronic. “When was the last time your breathing was entirely normal?”

— Symptoms can be shortness of breath, a lingering cough, or often fatigue and decreased energy. Occurrence is important! Do symptoms occur only with exertion or at rest too?

— “Have you ever had chest imaging before?”

— Take a thorough exposure history, and the weird questions are all necessary! Ask about birds and feathers (pet birds, bird feeders, down pillows or blankets, hunting, taxidermy), mold or water damage, organic or inorganic compounds from work (landscaping, ship yards, coal mines)

American College of Chest Physicians – Interstitial Lung Disease Patient Questionnaire

Physical Exam:

— Assess stability first and foremost

— Lung findings: crackles, inspiratory squeaks (often in hypersensitivity pneumonitis)

— Look for evidence of alternative diagnoses: volume overload, liver disease, signs of infection

— Evaluate for signs of connective tissue disease: examine the skin around the forehead and mouth for signs of scleroderma, look for rashes, perform a thorough joint examination and look at their hands, and assess muscle strength

Imaging:

— Order a high-resolution CT scan without contrast. High resolution means thin slices that are 1-2 mm thick. Contrast should be avoided if possible because it makes looking for subtle reticulations or ground-glass opacities harder

— Inspiratory and expiratory films help evaluate for gas trapping. If present, this may indicate hypersensitivity pneumonitis

— Prone films allow you to distinguish reticular changes in the dependent portions of the lungs from atelectasis

Reading the CT scan:

— Look at the distribution first. Is it uniform from top to bottom or not? Is it subpleural, peripheral predominant, or central?

— Identify key features: reticulation, traction bronchiectasis, honeycombing, ground-glass opacities, cysts, and nodules

Laboratory evaluation:

— ANA, Scl-70, DS DNA, anti-RNP, anti-centromere, RF, CCP, SSA, SSB, RNA pol 3, HIV, myositis panel, Hypersensitivity pneumonitis panel

Pulmonary function tests:

— A restrictive ventialtory defect is the classic pattern and can tell you about severity. In ILD, TLC, VC, FRC, and RV are generally all reduced in proportion

— Identify if there is obstruction or not, because if present this may indicate coexisting emphysema or hypersensitivity pneumonitis

–The DLCO can be helpful for disease severity, and for raising concern about other co-existing diagnoses such as pulmonary vascular disease, or emphysema

— A DLCO < 50% predicted may predict that the patient will need oxygen with exertion and the patient should be walked

6 Minute Walk Test:

— This should be performed for all new patients because it is important for prognosis

— In the first year after diagnosis, a 6MWD should be performed every 3 – 4 months to assess disease trajectory. It can be done every 6 – 12 months after that.

Differential Diagnosis:

Silo ILDs into two large buckets

1) An exposure, trigger, or underlying cause is present: hypersensitivity pneumonitis, medication-induced, occupational lung disease, connective tissue disease, granulomatous disorder

2) Idiopathic interstitial pneumonia

References and links for further reading

  1. Raghu G, Collard HR, Egan JJ, et al. An official ATS/ERS/JRS/ALAT statement: idiopathic pulmonary fibrosis: evidence-based guidelines for diagnosis and management. Am J Respir Crit Care Med. 2011;183(6):788-824. doi:10.1164/rccm.2009-040GL
  2. Raghu G, Brown KK. Interstitial lung disease: clinical evaluation and keys to an accurate diagnosis. Clinics in Chest Medicine. 2004;25(3):409-419. doi:10.1016/j.ccm.2004.05.007
  3. Bradley B, Branley HM, Egan JJ, et al. Interstitial lung disease guideline: the British Thoracic Society in collaboration with the Thoracic Society of Australia and New Zealand and the Irish Thoracic Society. Thorax. 2008;63 Suppl 5:v1-58. doi:10.1136/thx.2008.101691
  4. American Thoracic Society, European Respiratory Society. American Thoracic Society/European Respiratory Society International Multidisciplinary Consensus Classification of the Idiopathic Interstitial Pneumonias. This joint statement of the American Thoracic Society (ATS), and the European Respiratory Society (ERS) was adopted by the ATS board of directors, June 2001 and by the ERS Executive Committee, June 2001. Am J Respir Crit Care Med. 2002;165(2):277-304. doi:10.1164/ajrccm.165.2.ats01
  5. Lederer DJ, Martinez FJ. Idiopathic Pulmonary Fibrosis. New England Journal of Medicine. 2018;378(19):1811-1823. doi:10.1056/NEJMra1705751
  6. Travis WD, Hunninghake G, King TE, et al. Idiopathic nonspecific interstitial pneumonia: report of an American Thoracic Society project. Am J Respir Crit Care Med. 2008;177(12):1338-1347. doi:10.1164/rccm.200611-1685OC
  7. Wijsenbeek M, Cottin V. Spectrum of Fibrotic Lung Diseases. New England Journal of Medicine. 2020;383(10):958-968. doi:10.1056/NEJMra2005230
  8. Hariri LP, Roden AC, Chung JH, et al. The Role of Surgical Lung Biopsy in the Diagnosis of Fibrotic Interstitial Lung Disease: Perspective from the Pulmonary Fibrosis Foundation. Annals ATS. 2021;18(10):1601-1609. doi:10.1513/AnnalsATS.202009-1179FR
  9. Exposures. hpLung. Accessed February 12, 2022. https://www.hplung.com/

8. A Case of Dyspnea and Lymphadenopathy

Dave Furfaro, Kristina Montemayor, and Ansa Razzaq are back to tackle another pulmonary case! Listen in and solve the case yourself, and we’ll share some diagnostic pearls along the way. Let us know any additional thoughts on Twitter.

Patient Presentation

The is patient is 57-year-old man with hypertension and asthma who presents with dyspnea and left-sided pleuritic chest pain for 3 weeks. He was in his usual state of health until 3 weeks prior to admission, when he developed dyspnea and sharp left-sided chest pain that worsens with deep breathing. His symptoms are accompanied by unintentional 30-pound weight loss over the past several months as well as an intermittent cough that is nonproductive.

On physical exam, he is mildly tachypneic and saturating well on room air with otherwise normal vital signs. He has decreased breath sounds at the right lung base.

Initial labs

Key Learning Points

**Spoilers Ahead** If you want to think through the case on your own we advise listening to the episode first before looking at the infographics below

Physical Exam Pearls

Reasons for decreased breath sounds on physical exam

1. Increased thickness of chest wall

2. Reduced airflow to part of the lung

3. Overinflation to part of the lung

4. Something between the lung and chest wall — air or fluid

Determine bradypnea and tachypnea quickly by matching your breahting rate to the patient’s respiratory rate

Pleural Effusions

Transudative effusion partial differential: heart failure, nephrotic syndrome, hepatohydrothorax, fluid overload, hypoalbuminemia, urinothorax, amyloidosis*, chlothorax*, hypothyrodism*, malignancy*, sarcoidosis*

*these effusions often present as exudates but can be transudates

Exudative effusion partial differential: Infection, hemothorax, malignancy, connective tissue disease, chylothorax, pancreatitis, esophageal perforation.

Sarcoidosis

Key Elements of Diagnosis:

1. Is there a compatible presentation (imaging, physical exam)

2. Detection of non-necrotizing granulomatous inflammation in one or more tissue samples

3. Exclusion of other disease that may present similarily

Pulmonary stages of sarcoidosis:

Key to remember that patients don’t always progress through these stages. The system is useful for prognosticating and determining treatment based on the risk for disease progression.

Image source: Gupta Et Al. J Fam Pract. 2021 April;70(3):E4-E15 | 10.12788/jfp.0177

Treatment for pulmonary sarcoidosis

Patients with stage 1, and even many with stage 2, often don’t require treatment

The first-line agent is oral glucocorticoids and the typical starting dose is prednisone 20 – 40 mg by mouth daily. The patient should be evaluated closely, and ideally, this dose can be tapered starting at about 4 – 6 weeks. Following this, the prednisone dose is tapered slowly over 6 months – 1 year while monitoring for symptom recurrence.

Second-line steroid-sparing agents are methotrexate, azathioprine, or mycophenolate. These are often used if the patient relapses, or is on more then 10mg daily for 3 months after the initial taper with intolerance of steroids

Third-line agents: tumor necrosis factor (TNF)- alpha antagonists (small molecule or monoclonal antibody therapy)

References and links for further reading

  1. Light RW. Pleural Effusion. New England Journal of Medicine. 2002;346(25):1971-1977. doi:10.1056/NEJMcp010731
  2. Feller-Kopman D, Light R. Pleural Disease. New England Journal of Medicine. 2018;378(8):740-751. doi:10.1056/NEJMra1403503
  3. Sarcoidosis: An FP’s primer on an enigmatic disease. MDedge Family Medicine. 2021;70(3). doi:10.12788/jfp.0177
  4. Iannuzzi MC, Rybicki BA, Teirstein AS. Sarcoidosis. New England Journal of Medicine. 2007;357(21):2153-2165. doi:10.1056/NEJMra071714
  5. Drent M, Crouser ED, Grunewald J. Challenges of Sarcoidosis and Its Management. New England Journal of Medicine. 2021;385(11):1018-1032. doi:10.1056/NEJMra2101555

Radiology Rounds – 1/25/22

This week for radiology rounds we’re looking at some classic imaging signs of lobar collapse. Take a look, respond to our polls on Twitter, and make sure to subscribe to our podcast to get all of the Pulm PEEPs content!

References

  1. Kumaresh A, Kumar M, Dev B, Gorantla R, Sai PV, Thanasekaraan V. Back to Basics – ‘Must Know’ Classical Signs in Thoracic Radiology. J Clin Imaging Sci. 2015;5:43. doi:10.4103/2156-7514.161977
  2. Algın O, Gökalp G, Topal U. Signs in chest imaging. Diagn Interv Radiol. 2011;17(1):18-29. doi:10.4261/1305-3825.DIR.2901-09.1
  3. Gupta P. The Golden S Sign. Radiology. 2004;233(3):790-791. doi:10.1148/radiol.2333021407

7. Top Consults: Severe Asthma Exacerbation

We are excited to bring you another episode in our Pulm PEEPs Top Consults series! Kristina Montemayor and David Furfaro, are joined by Sandy Zaeh to discuss the assessment and management of a patient with a severe asthma exacerbation. We’ll follow a consult patient from the emergency department to the ICU, and cover everything from the physiology of pulsus paradoxus in asthma to how to manage the ventilator in status asthmaticus. Listen today and please send any questions our way on Twitter @pulmPEEPS.

Meet Our Guests

Sandy Zaeh is an Instructor of Medicine and Pulmonary & Critical Care Medicine physician at Yale School of Medicine.

Key Learning Points

References and links for further reading

  1. Chung KF, Wenzel SE, Brozek JL, et al. International ERS/ATS guidelines on definition, evaluation and treatment of severe asthma. European Respiratory Journal. 2014;43(2):343-373. doi:10.1183/09031936.00202013
  2. Rodrigo GJ, Rodrigo C, Hall JB. Acute asthma in adults: a review. Chest. 2004;125(3):1081-1102. doi:10.1378/chest.125.3.1081
  3. Godwin HT, Fix ML, Baker O, Madsen T, Walls RM, Brown CA. Emergency Department Airway Management for Status Asthmaticus With Respiratory Failure. Respir Care. 2020;65(12):1904-1907. doi:10.4187/respcare.07723
  4. Althoff MD, Holguin F, Yang F, et al. Noninvasive Ventilation Use in Critically Ill Patients with Acute Asthma Exacerbations. Am J Respir Crit Care Med. 2020;202(11):1520-1530. doi:10.1164/rccm.201910-2021OC
  5. Brenner B, Corbridge T, Kazzi A. Intubation and Mechanical Ventilation of the Asthmatic Patient in Respiratory Failure. Proc Am Thorac Soc. 2009;6(4):371-379. doi:10.1513/pats.P09ST4
  6. Laher AE, Buchanan SK. Mechanically Ventilating the Severe Asthmatic. J Intensive Care Med. 2018;33(9):491-501. doi:10.1177/0885066617740079
  7. Leatherman J. Mechanical ventilation for severe asthma. Chest. 2015;147(6):1671-1680. doi:10.1378/chest.14-1733

6. PEEP in ARDS Roundtable

This week on Pulm PEEPs, Dave Furfaro and Kristina Montemayor are joined by experts in the field of critical care medicine and ARDS to discuss all things PEEP! Drs. Roy Brower, Sarina Sahetya, Todd Rice, and Elias Baedorf-Kassis discuss everything ranging from PEEP basics to their approach to optimizing PEEP in patients with ARDS.

Meet Our Guests

Roy Brower is a Professor of Medicine at Johns Hopkins where he served as the MICU director for over 33 years, and he has been one of the pioneers for lung-protective ventilation for patients with ARDS.

Elias Baedorf-Kassis is an Assistant Professor of Medicine at Beth Israel Deaconess Medical Center and Harvard Medical School. He is the Medical Director of Respiratory Care at BIDMC, and helps lead the VV-ECMO program.

Todd Rice is an Associate Profess of Medicine in the Division of Allergy, Pulmonary, and Critical Care Medicine at Vanderbilt University and Vice President for Clinical Trial Innovation and Operations in the Vanderbilt Institute for Clinical and Translational Research.

Sarina Sahetya is an Assistant Professor of Medicine at Johns Hopkins Hospital and does research in the diagnosis and treatment of ARDS.


Key Learning Points

Driving Pressure figure from Amato et al. 2015. Stress index figure from Hess 2014.
  • The plateau pressure can be measured on the ventilator with an inspiratory hold maneuver
  • Extrinsic PEEP is applied by the ventiilator, while intrinsic PEEP, or auto-PEEP, occurs when there is incomplete emptying of the lungs due to inadequate time for exhalation. This often happens with obstructive lung disease. Intrinsic PEEP can be measured on the ventilator with an end-expiratory hold maneuver
  • We utilize PEEP in all intubated patients to minimize atelectasis. When patients are supine, the heart moves back 2 cm and the diaphragm raises by 2 cm, so often the left lower lobe of the lung is compressed and there is atelectasis there. This is often seen on CXR:

References, Image Sources, and Further Reading

  1. Higher versus Lower Positive End-Expiratory Pressures in Patients with the Acute Respiratory Distress Syndrome. New England Journal of Medicine. 2004;351(4):327-336. doi:10.1056/NEJMoa032193
  2. Amato MBP, Meade MO, Slutsky AS, et al. Driving Pressure and Survival in the Acute Respiratory Distress Syndrome. New England Journal of Medicine. 2015;372(8):747-755. doi:10.1056/NEJMsa1410639
  3. Writing Group for the Alveolar Recruitment for Acute Respiratory Distress Syndrome Trial (ART) Investigators. Effect of Lung Recruitment and Titrated Positive End-Expiratory Pressure (PEEP) vs Low PEEP on Mortality in Patients With Acute Respiratory Distress Syndrome: A Randomized Clinical Trial. JAMA. 2017;318(14):1335-1345. doi:10.1001/jama.2017.14171
  4. Beitler JR, Sarge T, Banner-Goodspeed VM, et al. Effect of Titrating Positive End-Expiratory Pressure (PEEP) With an Esophageal Pressure-Guided Strategy vs an Empirical High PEEP-Fio2 Strategy on Death and Days Free From Mechanical Ventilation Among Patients With Acute Respiratory Distress Syndrome: A Randomized Clinical Trial. JAMA. 2019;321(9):846-857. doi:10.1001/jama.2019.0555
  5. LaFollette R, Hojnowski K, Norton J, DiRocco J, Carney D, Nieman G. Using pressure–volume curves to set proper PEEP in acute lung injury. Nursing in Critical Care. 2007;12(5):231-241. doi:10.1111/j.1478-5153.2007.00224.x
  6. Hess DR. Respiratory mechanics in mechanically ventilated patients. Respir Care. 2014;59(11):1773-1794. doi:10.4187/respcare.03410
  7. Sahetya SK, Hager DN, Stephens RS, Needham DM, Brower RG. PEEP Titration to Minimize Driving Pressure in Subjects With ARDS: A Prospective Physiological Study. Respir Care. 2020;65(5):583-589. doi:10.4187/respcare.07102
  8. Umbrello M, Chiumello D. Interpretation of the transpulmonary pressure in the critically ill patient. Ann Transl Med. 2018;6(19):383. doi:10.21037/atm.2018.05.31
  9. Kenny JES. ICU Physiology in 1000 Words: Driving Pressure & Stress Index. PulmCCM. Published February 13, 2016. Accessed January 1, 2022. https://pulmccm.org/review-articles/icu-physiology-in-1000-words-driving-pressure-stress-index/

Radiology Rounds – 12/28/21

Today we’re bringing you a special edition of Radiology Rounds complete with classic imaging, and some key critical care and ventilator physiology. This case is a perfect lead-in for next week’s Pulm PEEPs Roundtable on PEEP titration, so make sure to tune in!

How would you best describe the imaging findings?


There are bilateral, diffuse alveolar infiltrates noted on imaging with evidence of an air bronchogram on the CT image.

The patient develops worsening hypoxemia requiring mechanical intubation. The patient has multifocal pneumonia and requires intubation. ABG is performed and the calculated PaO2:FIO2 ratio is 150. How would you describe the severity of ARDS?


This patient has moderate ARDS based on a PaO2:FIO2 ratio that is between 100 and 200. The patient’s initial ventilator settings on volume control are:

Based on these parameters, we can also calculate the driving pressure. Driving pressure is calculated by using Pplat-PEEP. In this case, Pplat (30)-PEEP (10), would give a driving pressure of 20.

5. A Case of Chronic, Productive Cough

The Pulm PEEPs are joined again by Natalie West to discuss a patient who presented with a chronic, productive cough. Listen in today as we work through our differential diagnosis, interpret basic pulmonary testing, and share our clinical reasoning along the way. We have some fantastic diagnostic and treatment teaching points, so once you’ve solved the case check out the takeaways and infographics below. Please let us know any additional insights you have on Twitter!

Patient Presentation

A 50-year-old woman, who is a never smoker, with a past medical history of recurrent pancreatitis presents to the pulmonary clinic with a chronic, productive cough. Her cough has been present for 3 years and has increased in frequency to now being present daily. In the last three months, the cough has also worsened and is productive of small amounts of yellow to green sputum. She has a history of chronic post-nasal drip and sinus infections, and uses intranasal steroids, but has not noted changes in these symptoms. There is no significant family history of pulmonary disease, and an exposure history review of symptoms is negative.

On physical exam, she was a thin woman who appeared her stated age and was breathing comfortably on room air. Her exam was notable for mild expiratory wheezing, primarily on auscultation of the right posterior lung field. She had no cyanosis, clubbing, evidence of volume overload, or abdominal tenderness.

Basic Spirometry Values
Chest X-ray

Key Learning Points

**Spoilers Ahead** If you want to think through the case on your own we advise listening to the episode first before looking at the infographics below.

Differential Diagnosis of Chronic Cough

Three most common causes: upper airway cough syndrome, GERD, cough variant asthma

Additional etiologies to consider: chronic bronchitis, post-infectious after a respiratory tract infection, bronchiectasis, ACE inhibitors, lung cancer, eosinophilic bronchitis, interstitial lung disease


Imaging Pearl


Evaluating Bronchiectasis


Making a New Diagnosis of Cystic Fibrosis in an Adult

Sweat testing

Sweat testing should be done in CF accredited center. Inform patients that there are no needles involved. Pilocarpine and electrical stimulation are applied to the arm or leg to stimulate the sweat gland, and then sweat is collected on filter paper, a gauze, or a plastic coil. From there, the amount of chloride in the sweat is calculated

Results

< 30 normal

31 – 60 indeterminate

> 60 is positive and Cystic Fibrosis is likely

What do you do with an Indeterminate test?

Patients with milder phenotypes of Cystic Fibrosis can have a normal or indeterminate sweat chloride level, and 10% of adults diagnosed with CF have a normal sweat chloride. If the sweat chloride test is indeterminate or normal, but suspicion is high for CF, then genetic testing for the whole array of mutations should be performed

References and links for further reading

  1. Morice AH, Millqvist E, Bieksiene K, et al. ERS guidelines on the diagnosis and treatment of chronic cough in adults and children. European Respiratory Journal. 2020;55(1). doi:10.1183/13993003.01136-2019
  2. Barker AF. Bronchiectasis. New England Journal of Medicine. 2002;346(18):1383-1393. doi:10.1056/NEJMra012519
  3. Bronchiectasis: a case-based approach to investigation and management | European Respiratory Society. Accessed November 23, 2021. https://err.ersjournals.com/content/27/149/180016
  4. Rowe SM, Miller S, Sorscher EJ. Cystic Fibrosis. New England Journal of Medicine. 2005;352(19):1992-2001. doi:10.1056/NEJMra043184
  5. Shteinberg M, Haq IJ, Polineni D, Davies JC. Cystic fibrosis. The Lancet. 2021;397(10290):2195-2211. doi:10.1016/S0140-6736(20)32542-3
  6. Jain R. Diagnosing Cystic Fibrosis in Adults: Better Late Than Never. Annals ATS. 2018;15(10):1140-1141. doi:10.1513/AnnalsATS.201806-432ED