Pulmonary Medicine Primer

By Lawrence Cheung

This book is aimed primarily at internal medicine residents or senior medical students to help them care for patients with pulmonary disease. This practical book covers the approach to various pulmonary problems, explains some of the devices and procedures used in pulmonary medicine, and reviews the interpretation of common pulmonary tests.

Lawrence Cheung is a respirologist and critical care specialist in Canada. He has worked with hundreds of medical students and residents from internal medicine, respirology, critical care, and other specialties. He has held several roles in medical education advisory committees.

• Language: English
• Publisher: Lulu Publishing Services
• Release date: Jun 27, 2014
• ISBN: 9781483413204

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Primer

Copyright © 2014 Lawrence Cheung

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ISBN: 978-1-4834-1320-4 (e)

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Lulu Publishing Services rev. date: 6/16/2014

Pulmonary Medicine Primer

First Edition

Lawrence Cheung MD, FRCPC

Associate Professor, Department of Medicine

Adjunct Associate Professor, Division of Critical Care Medicine

Director, Respirology Residency Program

University of Alberta

Preface

I have been fortunate enough to work with several hundred medical students and residents throughout my career. Many of these learners have expressed the need for practical learning material to help them care for the pulmonary patients they see during their training.

Thus, I have written this book for medical students and internal medicine residents who, at some point in their training, will look after patients admitted to hospital with pulmonary problems. There are chapters covering the approach to a variety of clinical problems, devices and procedures commonly used in Pulmonary medicine, and interpretation of selected pulmonary tests.

The Pulmonary Medicine Primer is not meant to be an all-inclusive treatise on pulmonary medicine. For extensive discussions of pulmonary diseases, there are many excellent textbooks available. Rather, the Primer is meant to provide practical guidance to junior learners in topics they will almost certainly see in the clinical workplace.

Disclaimer

The information in this book comes from evidence in the literature and the author’s own clinical experience.

Nevertheless, medicine evolves and changes, and information from any source, including this one, should always be verified by the individual clinician before it is used. As well, medicine must be tailored to the individual patient, and there are times when the suggestions in this book should be modified to suit the individual patient’s unique circumstances or the unique availability of local expertise and resources. In other words, if the information in this book does not make sense when applied to your clinical situation, it should not be followed. The author cannot be held responsible for any direct or indirect harm that occurs from the information and suggestions in this book.

Table of Contents

Chapter 1 Approach to Hemoptysis

Chapter 2 Approach to Interstitial Lung Disease

Chapter 3 Interstitial Lung Disease: Making Sense of the Acronyms

Chapter 4 Approach to Pleural Effusion

Chapter 5 Approach to Respiratory Failure

Chapter 6 Mechanical Ventilation Basics

Chapter 7 Approach to Respiratory Distress on a Ventilator

Chapter 8 Non-Invasive Ventilation Basics

Chapter 9 Approach to Chest Tube Problems

Chapter 10 Approach to Tracheostomy Tube Problems

Chapter 11 Common Bronchoscopy Procedures

Chapter 12 Oxygen Delivery Devices

Chapter 13 Approach to Pulmonary Function Test Interpretation

Chapter 14 Approach to Arterial Blood Gas Interpretation

Chapter 1

Approach to Hemoptysis

This chapter will help you answer the following clinically important questions regarding patients with hemoptysis:

1.  What is the overall diagnostic approach to a patient with hemoptysis?

2.  How can you use the CXR to narrow down the differential diagnosis?

3.  What other tests, besides the CXR, can help you determine the cause of hemoptysis?

I’ve illustrated a diagnostic approach to hemoptysis in the flowchart in Figure 1-1, to which I will refer throughout this chapter.

Image01.jpg

Figure 1-1 - An approach to hemoptysis.

Apparent Hemoptysis

Focus your history and physical exam to distinguish hemoptysis from GI or nasal sources of bleeding, determine the severity of the hemoptysis, determine the etiology of the hemoptysis.

Distinguishing hemoptysis from GI or nasal sources of bleeding can sometimes be difficult if the patient is unable to give an accurate description of his symptoms. Figure 1-2 summarizes some of the distinguishing features.

Image02.jpg

Figure 1-2 - Distinguishing hemoptysis from other sources of bleeding.

Massive or Non-Massive?

There is no universally accepted definition of massive hemoptysis and in the literature, volumes ranging from 100mL to 1000mL of expectorated blood in 24 hrs have been cited.

Also, even if there was agreement on the volume of blood needed to define massive hemoptysis, quantifying the amount of blood that a patient expectorates is difficult because blood may be mixed with other secretions (eg. saliva or sputum), patients may overestimate the amount of blood they expectorate, or patients may be unable to expectorate blood due to impaired cough mechanisms or weakness.

Therefore, some use clinical criteria, such as airway compromise or hemodynamic instability, to define massive hemoptysis. I, too, prefer a clinical definition of hemoptysis which includes some amount of expectorated blood significant enough to cause impaired gas exchange or even hemodynamic compromise.

In contrast to gastrointestinal bleeding where heart rate, blood pressure, hemoglobin, or transfusion requirements indicate the severity of bleeding, oxygenation is usually affected more than these other parameters in severe pulmonary bleeding. In other words, asphyxiation, rather than exsanguination, is often the cause of death in massive hemoptysis. This is because blood filling up the alveoli will cause hypoxemia before it causes significant derangements in hemodynamic status or haemoglobin level. Thus, in assessing the severity of pulmonary bleeding, I am equally (or more) concerned about the patient’s oxygen requirements in addition to his blood pressure, hemoglobin level, etc.

Massive hemoptysis requires emergency therapy in parallel with diagnostic workup, and you should consult ICU and/or possibly thoracic surgery.

Patients with non-massive hemoptysis are clinically stable. Minor bleeding (some flecks of blood mixed in with sputum) can usually be worked up as an outpatient.

Moderate bleeding (more than several teaspoons of blood for more than several days) may require hospital admission or, at the very least, an expedited, urgent outpatient workup.

CXR Findings?

There are many ways to group the causes of hemoptysis. For example, we can arbitrarily group hemoptysis according to the site of bleeding origin. These sites include the following:

1.  the tracheobronchial airways, where bleeding occurs from mucosal vessels, with or without inflammation.

2.  the lung parenchyma, where bleeding occurs from the capillaries in the alveoli, with or without inflammation

3.  vascular abnormalities, such as arterio-venous malformations or pulmonary emboli.

Typical causes of hemoptysis based on the site of bleeding are illustrated in Figure 1-3.

Image03.jpg

Figure 1-3 - Causes of pulmonary bleeding by site of origin

Direct your history and physical exam to distinguish the possible causes of hemoptysis listed in Figure 1-3. Integrating the medical history, physical exam, and chest X-ray findings narrows the initial differential diagnosis and site of bleeding. As I explain later, bronchoscopy, chest computed tomography (CT), or both are helpful after initial tests have been performed.

CXR - Normal

The CXR may appear normal in patients with hemoptysis, either because there is truly no radiographic abnormality, or because the abnormality is too subtle to detect by CXR. If the former, this often points to bleeding from the tracheobronchial airways, with the patient able to expectorate the blood out of the airways before it accumulates in the alveoli.

If the patient is young, has no risk factors for malignancy, has a history compatible with acute bronchitis, and has minor hemoptysis, then I think giving antibiotics and following the patient is a reasonable course, reserving further tests (such as bronchoscopy) if the patient’s hemoptysis persists.

If risk factors for malignancy - such as a history of smoking - are present, it is reasonable to perform bronchoscopy. If a CT chest can be obtained quickly, it would also be reasonable to do this first to look for a mass or adenopathy not obvious on the CXR, and then to procede to bronchoscopy.

Occasionally, there are patients who have sudden hemoptysis without preceding symptoms to suggest bronchitis (such as a preceding productive cough) yet, on bronchoscopy, are found to have inflamed and bleeding airways not related to malignancy. We often presume these patients have had bronchitis which was not clinically obvious.

Alternatively, some patients have an unremarkable CXR, CT chest, and bronchoscopy. There are conflicting reports about the future likelihood of cancer eventually developing in these patients. Thus, it is reasonable to warn patients with risk factors for malignancy about the symptoms of lung cancer and, perhaps, follow them for a period of time.

CXR - Mass

A mass on CXR suggests malignancy as the cause of hemoptysis. Chest CT, to further visualize the mass and look for other abnormalities such as adenopathy, other masses, etc, plus bronchoscopy, should be performed.

CXR - Diffuse, non-specific consolidation

Diffuse, non-specific consolidation could indicate material in the alveoli such as blood, pus, or fluid. In these settings, the blood is often coming from the lung. However, it is difficult to determine if all of the consolidation is due to blood or if the airspsace disease represents blood plus the etiologic process (eg. pneumonia, edema, etc).

If symptoms suggest a vasculitic cause (subacute or chronic presentation, unexplained constitutional or systemic symptoms, recurrent or persistent nasal symptoms, etc. ) do the appropriate tests, such as c – and p – ANCA, anti-GBM antibody, urinalysis or urine for cytodiagnostics, ANA, etc.

If pneumonia is suspected and the hemoptysis is minor, treat with appropriate antibiotics and obtain cultures. Also, rule out a co-existing bleeding diathesis by measuring platelet count, PT, and PTT.

Consider a CT chest to look for subtle abnormalities that might suggest a particular diagnosis (e.g. many small areas of microcavitation – ANCA vasculitis, etc).

Bronchoscopy should also be considered, and bloody fluid which persists or increases in successive aliquots suctioned during bronchoalveolar lavage suggests an alveolar source of bleeding.

If evidence of a systemic vasculitis is present clinically, biopsy is ideally needed to confirm the diagnosis. If the patient is too unstable to undergo lung biopsy, consider biopsy of another affected organ, such as a renal biopsy.

CXR - Focal, specific abnormality

Sometimes, the CXR will reveal focal or diagnostic abnormalities such as bronchiectasis, a lung cavity, or a pulmonary arteriovenous malformation (AVM). As opposed to non-specific consolidation, these diagnostic radiologic findings point to the underlying diagnosis.

An AVM will often look like a mass on CXR. CT with contrast will often be able to locate feeding vessels into the mass, revealing its nature as an AVM. This entity is uncommon.

A far more common cause of hemoptysis is bronchiectasis. Inflammation is usually present during an episode of hemoptysis, even in the absence of new/acute symptoms,