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MSII Practice of Medicine > Unit 4 - Dyspnea > Flashcards

Unit 4 - Dyspnea Flashcards

1
Q

what is the definition of dyspnea?

A

sensation of breathlessness or SOB experienced by both normal subjects and patients with diseases affecting respiratory system

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2
Q

what are components of dyspnea?

A
  • increased work/effort
  • unrewarded inspiration
  • inspiratory difficulty
  • shallow breathing
  • rapid breathing
  • tight chest
  • suffocating feeling
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3
Q

what are psychometric measurements of dyspnea?

A
  • MMRC (modified medical research council) dyspnea scale
  • visual analogue scale
  • modified Borg category scale
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4
Q

what is the modified Borg category scale to rate dyspnea?

A

scale from 0 (nothing at all) to 10 (maximal)

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5
Q

what is the modified medical research council scale?

A

Grade 0 (breathless with strenuous exercise) to Grade 4 (breathless when dressing, cannot leave house)

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6
Q

what is the mechanism of dyspnea?

A
  • several sensory receptors located throughout respiratory system are responsible; no one is solely responsible
  • afferent info from sensory receptors is processed at cortex along with respiratory motor command from cortex and brainstem
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7
Q

how are chemoreceptors involved in dyspnea?

A

induction of hypercapnia or severe hypoxemia causes dyspnea

-patients with the above aren’t invariably dyspneic

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8
Q

what do chest wall mechanoreceptors have to do with dyspnea?

A

located in muscle spindles and tendon organs in respiratory muscles

  • innervated by anterior horn cells of spinal motor neurons
  • project to somatosensory cortex
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9
Q

what are metaboreceptors? how are they involved in dyspnea?

A
  • located in skeletal muscle
  • respond to local changes in tissue environment with respect to by-products of metabolism
  • source of afferent neurological signals that lead to perception of dyspnea during exercise w/o hypoxemia and hypercapnia
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10
Q

what are vagal receptors?

A
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11
Q

how are slowly adapting stretch receptors involved in dyspnea?

A

found in smooth muscle of larger airways

  • correspond to myelinated afferent nerve fibers in vagus
  • SARs activity is affected by:
  • -inhalation of CO2 - inhibit activity
  • -volatile anesthetics - may inhibit or stimulate receptors depending on concentration
  • -furosemide - improve experimentally induced dyspnea
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12
Q

how are rapidly adapting stretch receptors involved in dyspnea?

A

receptors adapt rapidly to maintained inflation or deflation of the lungs

  • AKA irritant receptors
  • activated by mechanical and chemical irritant stimuli, inflammatory/immunological mediators, and by airway and lung pathological changes
  • pneumothorax or other disease that distorts lung architecture can stimulate these receptors to cause dyspnea
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13
Q

how are C-fiber receptors involved in dyspnea?

A

juxta-pulmonary capillary receptors or J receptors

  • localized close to alveolar capillaries in pulmonary and bronchial circulation
  • respond to increased interstitial fluid outside capillaries
  • pulmonary congestion is strong stimulator of C-fiber receptors
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14
Q

what receptors does hypercapnia act on? the quality of dyspnea?

A

acts on central chemoreceptors –> air hunger

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15
Q

what receptors does hypoxia act on? the quality of dyspnea?

A

acts on peripheral chemoreceptors –> air hunger

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16
Q

what receptors does respiratory motor command act on? the quality of dyspnea?

A

central corollary discharge, metaboreceptors –> work/effort

17
Q

what receptors does bronchoconstriction act on? the quality of dyspnea?

A

RARs, C-fiber receptors –> chest tightness

18
Q

what receptors does lung inflation act on? the quality of dyspnea?

A

SARs –> dyspnea relief

19
Q

what is the systematic approach to dyspnea?

A

3 components

  1. controller - determines rate/depth of breathing
  2. ventilatory pump - facilitates movement of gas into and out of alveolus
  3. gas exchanger - consists of pulmonary vasculature and alveolus
20
Q

dyspnea caused by ventilatory controller and gas exchanger problems is associated with what?

A

increased respiratory drive

  • stimulation of chemoreceptors, pulmonary receptors (irritant, mechanical, vascular)
  • behavioral factors
21
Q

dyspnea caused by ventilatory pump problems is associated with what?

A

increased effort or work of breathing

  • muscle weakness
  • decreased compliance of chesst wall
  • airflow obstruction (increased resistive load from narrowing of airways and increased elastic load from hyperinflation)
22
Q

what are conditions that lead to acute hypoxemia?

A
  • impaired gas exchange (asthma, pulmonary embolism, pneumonia, CHF)
  • environmental hypoxia (altitude, fire)
23
Q

what are conditions leading to increased dead space and/or acute hypercapnia?

A
  • impaired gas exchange (acute, severe asthma; exacerbation of COPD; severe pulmonary edema)
  • impaired ventilatory pump (muscle weakness, airflow obstruction)
24
Q

what is metabolic acidosis-induced dyspnea caused by?

A

renal disease (renal failure, tubular acidosis)

25
Q

what is decreased release of O2 to tissues due to?

A

hemoglobinopathy

26
Q

how can pulmonary receptors be stimulated?

A

by irritants, mechanical, or vascular

  • interstitial lung disease
  • pleural effusion (compressive atelectasis)
  • pulmonary vascular disease (thromboembolism, idiopathic pulmonary HTN)
  • CHF
  • mild asthma
27
Q

what are muscle weakness disorders that can cause dyspnea?

A
  • myasthenia gravis
  • Guillain-Barre
  • spinal cord injury
  • myopathy
  • post-poliomyelitis syndrome
28
Q

what diseases with decreased compliance of chest wall can cause dyspnea?

A
  • severe kyphoscoliosis
  • obesity
  • pleural effusion
29
Q

how does airflow obstruction cause dyspnea?

A

increases restrictive load from narrowing of airways, and increases elastic load from hyperinflation

  • asthma
  • COPD
  • laryngospasm
  • aspiration of foreign body
30
Q

what is intermittent dyspnea probably caused by?

A

reversible conditions

  • bronchoconstriction (asthma)
  • CHF
  • pleural effusion
  • acute pulmonary emboli
31
Q

what is persistent/progressive dyspnea probably caused by?

A

chronic conditions

  • COPD
  • interstitial fibrosis
  • chronic pulmonary emboli
  • dysfunction of diaphragm or chest wall
32
Q

what is nocturnal dyspnea probably caused by?

A
  • asethma
  • CHF
  • GERD
  • obstructive sleep apnea
  • nasal obstruction
33
Q

what is orthopnea probably caused by?

A

(dyspnea in recumbent position)

  • LV failure
  • abdominal processes
  • diaphragmatic dysfunction
34
Q

what is platypnea probably caused by?

A

(dyspnea in upright position)

  • orthodeoxia (decrease in PO2 if upright)
  • cirrhosis
  • pulmonary arteriovenous malformations
  • interatrial shunts
35
Q

what diseases are associated with generalized VS localized decrease in breath sounds?

A

GD: emphysema, moderate/severe bronchoconstriction
LD: pneumothorax, pleural effusion, localized airway obstruction

36
Q

what will cardiac exam show in dyspnea?

A
  • pulmonary HTN (RV heave or prominent P2)
  • RV failure (JVD, right-sided S3 gallop)
  • LV failure (left-sided S3 gallop)
37
Q

how to treat symptoms of dyspnea?

A

reduce sense of effort and improve respiratory muscle function

  • energy conservation
  • breathing strategies
  • position
  • correct obesity/malnutrition
  • inspiratory muscle exercise and rest
  • medications (theophyline)
38
Q

how to decrease respiratory drive?

A
  • supplemental O2
  • -reduce carotid body activation
  • -improved ventilatory muscle function
  • -stimulation of LV contractility
  • -reduced pulmonary artery pressure
  • vagal nerve or carotid body resection not done anymore
39
Q

how can opiates alter central perception to treat dyspnea?

A
  • reduce severity of dyspnea (including reduction in ventilation)
  • respiratory depression is concern
  • palliation of dyspnea in terminal malignant disease or chronic respiratory failure

MSII Practice of Medicine (13 decks)

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