Dyspnea on Exertion (DOE)


Article Author:
Sandeep Sharma


Article Editor:
Madhu Badireddy


Editors In Chief:
Wanda Wright
Cynthia Oster


Managing Editors:
Avais Raja
Orawan Chaigasame
Carrie Smith
Abdul Waheed
Khalid Alsayouri
Frank Smeeks
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Trevor Nezwek
Radia Jamil
Patrick Le
Sobhan Daneshfar
Anoosh Zafar Gondal
Saad Nazir
William Gossman
Pritesh Sheth
Hassam Zulfiqar
Navid Mahabadi
Steve Bhimji
John Shell
Matthew Varacallo
Heba Mahdy
Ahmad Malik
Mark Pellegrini
James Hughes
Beata Beatty
Nazia Sadiq
Hajira Basit
Phillip Hynes
Tehmina Warsi


Updated:
6/22/2019 7:55:07 AM

Introduction

Dyspnea, also called shortness of breath, is a patient's perceived difficulty to breathe. Sensations and intensity can vary and are subjective. It is a prevalent symptom impacting millions of people. It may be the primary manifestation of respiratory, cardiac, neuromuscular, psychogenic, or systemic illnesses, or a combination of these. Dyspnea on exertion is a similar sensation. However, this shortness of breath is present with exercise and improves with rest. Exercise is defined here as any physical exertion which increases metabolic oxygen demand above the body’s ability to compensate. Oxygen is vital to the human body as its used for oxidative phosphorylation, and it is the last acceptor of an electron in electron transport chain. The sensation of dyspnea mostly comes when our body is lacking the oxygen delivery.[1]

Oxygen Delivery:  Hb x 1.39 x SaO2 x Cardiac Output + 0.003 x Pao2

  • Hb is hemoglobin concentration in grams per liter
  • 1.39- oxygen binding capacity of hemoglobin per gram
  • SaO2 is hemoglobin oxygen saturation expressed as a fraction ( like- 98% will be 0.98)
  • Cardiac output is the amount of blood heart is pumping in liter per minute
  • 0.003 x pao2 is the amount of dissolved oxygen in the blood in milliliters

If a body has low Hb, hemoglobinopathies, some toxicities affecting Hb (like carbon monoxide toxicity), low cardiac output (congestive heart failure [CHF], myocardial infarction [MI], arrhythmia) a person will feel dyspneic.[2]

Etiology

Dyspnea on exertion is a symptom disease, rather than a disease itself. As such, its etiology can be designated as arising from two primary organ systems: the respiratory system and the cardiac system. Other systemic illnesses may by culprit as well as a combination of different etiologies.

Respiratory causes may include asthma, acute exacerbation of chronic obstructive pulmonary disorder (COPD), pneumonia, pulmonary embolism, lung malignancy, pneumothorax, or aspiration.[1]

Cardiovascular causes may include congestive heart failure, pulmonary edema, acute coronary syndrome, pericardial tamponade, valvular heart defect, pulmonary hypertension, cardiac arrhythmia, or intracardiac shunting.

Other systemic illnesses may include anemia, acute renal failure, metabolic acidosis, thyrotoxicosis, cirrhosis of the liver, anaphylaxis, sepsis, angioedema, and epiglottitis.

Epidemiology

The epidemiology of dyspnea on exertion is highly variable depending on etiology.[1]

Pathophysiology

Dyspnea on exertion is the sensation of running out of the air and of not being able to breathe fast or deeply enough during physical activity. It results from multiple signal interactions with receptors in the central nervous system (CNS), peripheral receptors chemoreceptors, and mechanoreceptors in the upper airway, lungs, and chest wall.

The respiratory center of the brain is comprised of 3 neuron groupings in the brain: the dorsal and ventral medullary groups and the pontine grouping. The pontine grouping further classifies into the pneumotaxic and apneustic centers. The dorsal medulla is responsible for inhalation. The ventral medulla is responsible for exhalation. The pontine groupings are responsible for modulating the intensity and frequency of the medullary signals where the pneumotaxic groups limit inhalation and the apneustic centers prolong and encourage inhalation. Each of these groups communicates with one another to unify the efforts as the pace making potential of respiration.

Mechanoreceptors located in the airways, trachea, lung and pulmonary vessels exist to provide sensory information to the respiratory center of the brain regarding the volume of the lung space. There are 2 primary types of thoracic sensors: slow adapting stretch spindles and rapid adapting irritant receptors. Slow-acting spindle sensors convey only volume information.

However, the rapid-acting receptors respond to both volume of the lungs and chemical irritation triggers such as harmful foreign agents that may be present. Both types of mechanoreceptors signal via cranial nerve X (the Vagus nerve) to the brain to increase the rate of breathing, the volume of breathing, or to stimulate errant coughing patterns of breathing secondary to irritants in the airway.

Peripheral chemoreceptors consist of the carotid and the aortic bodies. Both sites function to monitor the partial pressure of arterial oxygen in the blood. However, hypercapnia and acidosis increase the sensitivity of these sensors and play a partial role in the receptor’s function. The carotid bodies are located at the bifurcation of the common carotid arteries, and the aortic bodies are located within the aortic arch. Once stimulated by hypoxia, they send a signal via cranial nerve IX (the glossopharyngeal nerve) to the nucleus tractus solitarius in the brain, which in turn, stimulates excitatory neurons to increase ventilation. It has been estimated that the carotid bodies comprise 15% the total driving force of respiration.[3]

Central chemoreceptors hold the majority of control over respiratory drive. They function through sensing pH changes within the CNS. Primary locations within the brain include the ventral surface of the medulla and the retrotrapezoid nucleus. pH changes within the brain and surrounding cerebrospinal fluid is derived primarily from increases or decreases in carbon dioxide levels. Carbon dioxide is a lipid-soluble molecule that freely diffuses across the blood-brain barrier. This characteristic proves to be useful in that rapid changes in pH within the cerebrospinal fluid are possible. Chemoreceptors responsive to pH change are located on the ventral surface of the medulla. As these areas become more acidic, sensory input is generated to stimulate hyperventilation, and carbon dioxide within the body is reduced through the increased ventilation. When pH rises to more alkalotic levels, hypoventilation occurs, and carbon dioxide levels decrease secondary to decreased ventilation.

Respiratory centers located within the medulla oblongata and pons of the brainstem are responsible for generating the baseline respiratory rhythm. However, the rate of respiration is modified by allowing for aggregated sensory input from the peripheral sensory system which monitors oxygenation, and the central sensory system which monitors pH and indirectly carbon dioxide levels along with several other portions of the cerebellar brain modulate to create a unified neural signal. The signal is then sent to the primary muscles of respiration, the diaphragm, external intercostals, and scalene muscles along with other minor muscles of respiration.[4]

History and Physical

The history and physical exam should ascertain whether there are any chronic underlying cardiovascular or pulmonary illnesses. Key components of the history include onset, duration, aggravating factors, and alleviating factors. Presence of a cough may indicate the presence of asthma, chronic obstructive pulmonary disease (COPD), or pneumonia. A severe sore throat could indicate epiglottitis. Pleuritic quality chest pain may indicate pericarditis, pulmonary embolism, pneumothorax, or pneumonia. Orthopnea, nocturnal paroxysmal dyspnea, and edema suggest a possible diagnosis of congestive heart failure. Tobacco use is a common history finding that increases the likelihood of COPD, congestive heart failure, and pulmonary embolism. If indigestion or dysphagia is present, consider gastroesophageal reflux disease or gastric secretion aspiration in the lungs. A barking quality cough, especially in children may suggest croup. Presence of fever strongly suggests an infectious etiology.

The physical exam should begin with a rapid assessment of the ABCs (airway, breathing, and circulation). Once determined to be stable, a full physical exam can be done. To determine the severity of dyspnea, carefully observe respiratory effort, use of accessory muscles, mental status, and ability to speak. Distention of the neck veins may imply cor pulmonale caused by severe COPD, congestive heart failure, or cardiac tamponade. Thyromegaly may indicate hyperthyroidism or hypothyroidism. Percussion of the lung lobes for dullness can determine the presence or absence of consolidation and effusion. Hyperresonance on percussion is a worrisome finding that indicates possible pneumothorax or severe bullous emphysema. Lung auscultation may reveal absent breath sounds indicating the presence of region occupying mass such as pleural effusion or malignancy. The presence of wheezing is highly consistent with the diagnosis of an obstructive lung disease such as asthma or COPD. However, wheezing may be associated with pulmonary edema or pulmonary embolism. Pulmonary edema and pneumonia may present with rales on auscultation. Auscultation of the heart may reveal the presence of dysrhythmia, cardiac murmurs, or aberrant heart gallops. An S3 gallop indicates cardiac overfilling seen in left ventricular systolic dysfunction and congestive heart failure (CHF). An S4 gallop suggests left ventricular dysmotility and dysfunction. A loud P2 indicates possible pulmonary hypertension. Murmurs may indicate valvular dysfunction. Diminished heart sounds may indicate cardiac tamponade. Pericarditis may present with a rubbing cardiac sound on auscultation. On abdominal examination, hepatomegaly, ascites, positive hepatojugular reflux may suggest a diagnosis of CHF. Lower extremity edema is associated with CHF, and extreme swelling of the extremities suggests possible deep venous thrombosis that can lead to a pulmonary embolism. Digits clubbing is present in some forms of lung malignancy or severe chronic hypoxia. Cyanosis of the extremities indicates hypoxia. [5]

Evaluation

Every evaluation should begin with a rapid assessment of the ABC status of the patient. Once these are determined to be stable and no life-threatening status present, a complete history and physical exam can be collected. Vital signs should be assessed for heart rate, respiratory rate, body temperature, body mass index (BMI), and oxygen saturation. Oxygen saturation may be normal at rest, so oxygen saturation with physical exertion should be obtained. In normal physiological conditions, the pulse oximetry improves as V/Q matching improves. Fever may indicate an infectious etiology. A chest x-ray is the first diagnostic test that should be utilized in evaluating dyspnea on exertion. If abnormal the disease process is likely cardiac or a primary pulmonary process. An echocardiogram is needed to evaluate cardiac function, pericardial space, and valvular function.

Additionally, an electrocardiogram should be obtained to evaluate for myocardial infarction or right-sided heart pattern strain. Elevated pro-brain natriuretic peptide (BNP) levels can further a congestive heart disease diagnosis. Exercise stress testing is also beneficial to determine cardiac function along with exercise oxygenation. If the chest x-ray is normal, then spirometry is needed to determine lung function. Abnormal spirometry can indicate either an obstructive pathology such as asthma, COPD, or physical airway obstruction or restrictive disease processes such as interstitial fibrosis. Spirometry can also indicate the presence of respiratory muscle weakness from muscular or neurological abnormalities. Normal spirometry indicates a need to evaluate for hypoxia as a source of dyspnea. The restrictive pathology can be confirmed with lung volumes, which will show reduced total lung capacity (TLC). In obstructive lung disease, the TLC is increased, and RV/TLC ratio is increased. Diffusion capacity is reduced in disease processes which affect the alveolar membrane area and or thickness. For example, it will be reduced with interstitial lung disease (ILD), emphysema, pulmonary embolism (PE), CHF, and obesity.

Arterial blood gas testing is used for this purpose as well as to calculate the A-a gradient and assess for an acidotic state. If hypoxic at PaO2 is low with a normal chest x-ray, then pulmonary embolism should be considered. The pH is mostly alkalotic in the setting of PE. This is to blow carbon dioxide to relatively increase the partial pressure of oxygen. In a pregnant female d-dimer with leg ultrasound and V/Q scan should be ordered first. Detection of a mismatch in 2 or more areas indicates pulmonary embolism. D-dimer testing has a low specificity and a high sensitivity. Spiral CT of the chest is an alternative to V/Q scanning. In acute settings, the CT chest with PE protocol is the gold standard. If the dyspnea on exertion is chronic, then chronic thromboembolic pulmonary hypertension (CTEPH) should be considered, and VQ scan is the test of choice and is considered the gold standard. The VQ scan in this setting has a “moth-eaten” appearance.

A normal scan necessitates cardiac catheterization to determine pulmonary hypertension, intracardiac shunting, or coronary artery disease. A normal cardiac catheterization diagnosis idiopathic dyspnea. If hypoxia is not present with a PaO2 greater than 70 mm Hg, correlation with oxygen saturation is needed. Abnormal oxygen saturation indicates possible carbon monoxide poisoning, methemoglobinemia, or an abnormal hemoglobin molecule.

Normal oxygen saturation requires a complete blood count (CBC) to evaluate hemoglobin content and hematocrit values. The white blood count also assesses for an immune response to possible infection. Hematocrit less than 35% is anemia.

  • Oxygen Delivery:  Hb x 1.39 x SaO2 x Cardiac Output + 0.003 x Pao2

If one cannot determine the etiology of dyspnea, then we should order a cardiopulmonary exercise test (CPET). If the CPET does not show any cardiac or pulmonary etiology, then likely diagnosis for dyspnea on exertion is physical deconditioning.

All testing modalities should target toward clinical suspicion and the history and physical exam to avoid overtesting and minimize cost to the patient.[6]

Treatment / Management

Treatment for dyspnea on exertion depends on its underlying etiology. The first intervention is to determine that there are no life-threatening etiologies present on an acute presentation by monitoring the ABC’s (airway, breathing, and circulation) of the patient. Once determined to be stable and that no immediate lifesaving interventions are necessary to further treatments can be assessed. If a patient is using smoking tobacco, this should be discontinued. Various inhaler therapies may be used in respiratory disease including short-acting or long-acting bronchodilators, inhaled antimuscarinics, and inhaled corticosteroids. Continuous supplemental oxygen therapy is used to ease discomfort associated with dyspnea on exertion if oxygen saturation is shown to decrease with exercise. [7] Cardiac function should be optimized when a cardiac illness is identified. If a myocardial infarction is suspected based on ST changes on electrocardiogram or troponin marker evaluation, rapid percutaneous intervention should be performed by a cardiologist.  Aspirin, statin, ACE inhibitor, beta-blocker, heparin, and nitro therapy should be initiated immediately if no contraindications. Occasionally, medications such as beta blockers and calcium-channel blockers can induce dyspnea on exertion by decreasing cardiac function, which can be picked up on a CPET. These should be decreased or discontinued when possible. In CHF, diuretic medications should be used to decrease vascular congestion from fluid overloading. If the dyspnea on exertion is due to obesity or deconditioning physical therapy and an exercise regimen should be pursued. If psychological problems are causing dyspnea on exertion, a selective serotonin receptor inhibitor can be trialed along with counseling sessions [8]. Weight loss in obses patients, especially women will improve outcome. [9]

Differential Diagnosis

Acute dyspnea on exertion is most likely caused by acute myocardial ischemia, heart failure, cardiac tamponade, pulmonary embolism, pneumothorax, pulmonary infection in the form of bronchitis or pneumonia, or upper airway obstruction by aspiration or anaphylaxis.

Chronic dyspnea is most likely caused by asthma, chronic obstructive pulmonary disease, congestive heart failure, interstitial lung disease, myocardial dysfunction, obesity, or deconditioning.

The most common diagnosis underlying dyspnea on exertion is CHF.

Prognosis

In itself, dyspnea on exertion is harmless and a normal physiological finding; however, as it is a symptom and not an illness, it may indicate an underlying disease. The prognosis is highly variable and depends on the underlying etiology and comorbidities.

Complications

If left untreated, dyspnea on exertion can progress to acute respiratory failure with hypoxia and/or hypercapnea further leading to life-threatening respiratory or cardiac arrest or both.

Consultations

Based on possible underlying etiology after initial evaluation, a Cardiologist or a Pulmonologist needs to be consulted.

Deterrence and Patient Education

Patients needs to be educated about seriousness dyspnea on exertion and needs to be advised to get immediate medical help for recurrence of his symptoms as this can life-threatening. In paptients with CHF needs to be educated about fluid restriction, dietary modifications, daily weights and take all medications including diuretics as advised. CHF management can be overwhelming for patients and can lead to high emotions and even depression[10][11]. Patients needs to be screened for mood disorders and referred to a Psychiatrist if needed. 

Pearls and Other Issues

Dyspnea on exertion is a symptom of an underlying condition rather than a diagnosis. 

Enhancing Healthcare Team Outcomes

Most common cause of dyspnea on exertion is CHF. Management of CHF is complicated and a multidisciplinary approach is very important. Patient and his family needs to be educated by heart failure nurse prior to discharge from the hospital. Patient needs close follow up with their primary care physician, Cardiologist, heart failure nurse, and dietician. Patient would also benefit from home health serives after discharge from hospital to help monitor weight and make sure they are taking all their medications. This would help reduce hospital readmission. 


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Dyspnea on Exertion (DOE) - Questions

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Which of the following is considered a primary organ system that may induce dyspnea on exertion?



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Which of the following factors does not determine peripheral oxygen delivery within the body?



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A 51-year-old female presents with a 2-month history of progressively worsening dyspnea on exertion. She has not received any treatment and denies fever, chills, or rigors. She has been smoking cigarettes since 14 years of age and currently smokes 2 packs per day. She has lost 8 pounds of weight in the last 2 months, and her appetite is poor. Her family history is unremarkable. What is the best next step in management?



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A 62-year-old male is referred by his primary care provider to the pulmonary clinic for evaluation of dyspnea on exertion. He can walk two to three city blocks without dyspnea but lately has been dyspneic when walking up hills or climbing stairs. He is a nonsmoker and worked in coal mines from 20 to 25 years of age. Since then, he has been a school teacher. He has no history of weight loss or night sweats and no family history of any type of cancer. His father had emphysema diagnosed at 50 years of age and mother at 62 years of age. His father was a heavy smoker and worked in coal mines. His primary care office sent his echocardiogram and chest x-ray reports. The echocardiogram shows an ejection fraction of 50%, with mild elevation of pulmonary artery pressures at 30 mmHg. The chest x-ray shows emphysema in both lower lobes. What are the best next tests to order?



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A 42-year-old adult with a known history of asthma, hypertension, diabetes, and stage 3 chronic kidney disease presented with a five-day history of progressively worsening exertional dyspnea. She denies any difficulty breathing at rest and also denies orthopnea. She recently came back from a 2-week vacation in Europe trip. Physical examination revealed a heart rate of 110/min, respiratory rate of 22/min, and oxygen saturation of 89% on room air. Lungs were clear to auscultation without any wheeze or rales or rhonchi. She also has swelling of the left leg and calf tenderness. Chest x-ray is negative for any acute abnormalities. EKG revealed sinus tachycardia. Labs revealed creatinine of 1.5 mg/dL and normal B-type natriuretic peptide (BNP). What is the most likely diagnosis?



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A 22-year old male with a known history of asthma as a child and type 1 diabetes presented with a 1-week history of progressively worsening dyspnea on exertion. He denies any orthopnea, leg swelling, or wheezing but reports of non-productive cough. He was unable to walk more than two blocks at a time and gets short of breath even going up 1 flight of stairs at home. He is currently on insulin but no other medications. On examination, he is tachycardic, tachypneic, and hypoxic with oxygen saturation of 88% on room air. On exam, there is decreased breath sounds but no wheezes or rales. His chest x-ray was clear, and EKG revealed sinus tachycardia. Laboratory data reveals normal CBC, basic metabolic profile, B-type natriuretic peptide, and D-dimer. What is the most likely cause of patient's dyspnea on exertion and what workup is needed at this time?



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Dyspnea on Exertion (DOE) - References

References

Zhuravleva MV,Prokofiev AB,Shih EV,Serebrova SY,Gorodetskaya GI, [Novel Possibilities in Pharmacotherapy of Patients With Chronic Heart Failure]. Kardiologiia. 2018 Oct     [PubMed]
Bernhardt V,Babb TG, Weight loss reduces dyspnea on exertion in obese women. Respiratory physiology & neurobiology. 2014 Dec 1     [PubMed]
Zahid I,Baig MA,Ahmed Gilani J,Waseem N,Ather S,Farooq AS,Ghouri A,Siddiqui SN,Kumar R,Sahil,Suman,Kumar R,Kumar R,Mulla AA,Siddiqi R,Fatima K, Frequency and predictors of depression in congestive heart failure. Indian heart journal. 2018 Dec     [PubMed]
Marines-Price R,Bernhardt V,Bhammar DM,Babb TG, Dyspnea on exertion provokes unpleasantness and negative emotions in women with obesity. Respiratory physiology & neurobiology. 2019 Feb     [PubMed]
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Rawat D,Sharma S, Dyspnea 2018 Jan;     [PubMed]
Marcus BS,McAvay G,Gill TM,Vaz Fragoso CA, Respiratory symptoms, spirometric respiratory impairment, and respiratory disease in middle-aged and older persons. Journal of the American Geriatrics Society. 2015 Feb;     [PubMed]
Janssen R,Piscaer I,Franssen FM,Wouters EF, Emphysema: looking beyond alpha-1 antitrypsin deficiency. Expert review of respiratory medicine. 2019 Feb 14;     [PubMed]
Parshall MB,Schwartzstein RM,Adams L,Banzett RB,Manning HL,Bourbeau J,Calverley PM,Gift AG,Harver A,Lareau SC,Mahler DA,Meek PM,O'Donnell DE, An official American Thoracic Society statement: update on the mechanisms, assessment, and management of dyspnea. American journal of respiratory and critical care medicine. 2012 Feb 15     [PubMed]

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