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DYSPNEA Dyspnea is subjective experience of breathing discomfort that consists of qualitatively distinct sensations that vary in intensity . Dyspnea , a symptom , must be distinguished from signs of increased work of breathing.

Mechanisms of Dyspnea:

Mechanisms of Dyspnea Respiratory sensations are the consequence of interactions b/w the efferent , motor output from the brain to the ventilatory muscles & afferent, sensory input from receptors throughout the body & integrative processing of this information that we infer must be occurring in the brain.

Motor Efferents:

Motor Efferents Disorders of ventilatory pump – increased work of breathing When muscles are weak/fatigued , greater effort is required even though other mechanics of system are normal.

Sensory Afferents:

Sensory Afferents Chemoreceptors in carotid bodies & medulla activated by hypoxemia, acute hypercapnia and acidemia . Mechanoreceptors in lungs – stimulated by bronchospasm – chest tightness J-receptors – sensitive to interstitial edema Pulmonary vascular receptors – activated by acute changes in Pul.A pressure – air hunger. Metaboreceptors – skeletal muscle - exercise

Efferent & Reafferent Mismatch:

Efferent & Reafferent Mismatch Mimatch b/w feed forward message to ventilatory muscles & feedback from receptors that monitor response of ventilatory pump increases dyspnea (asthma, COPD)

Physiological basis :

Physiological basis Increased ventilatory drive – 1. increase PaCo2—COPD 2. decreasePaO2—asthma,COPD, acidemia– diabetic ketoacidosis , lactic acidosis 3. fever 4. exercise

Physiological basis:

Physiological basis Reduced ventilatory capacity - 1. decrease lung vol – restrictive lung ds (pneumonia,pul.edema,ILD) 2. Pleural pain 3. Increase resistance to airflow – asthma, COPD, upper airway &laryngeal obstruction.

Assessing quality of dyspnea:

Assessing quality of dyspnea Descriptor Chest tightness Increased work of breathing Air hunger Cannot get a deep breath/ unsatisfying breath Rapid breathing Pathophysiology Bronchoconstriction,interstital edema Airway obst , neuromuscular ds Increase drive to breathe-CHF, pul.embolism , airway obst Hyperinflation( asthma,copd ) , restricted tidal vol ( pul.fibrosis ) deconditioning


History Timing, Place, Position at onset of symptoms. Mode of onset, duration , progression, severity Precipitating factors Ameliorating/ aggravating factors Associated symptoms ( wheezing, cough,sputum prod, pleuritic chest pain, excessive daytime sleepiness, peripheral /prox muscle weakness) Exposures – work place , tobacco , inhalants, pets, toxins Medications- beta blockers, methotrexate , bleomycin, nitrofurantoin, amiodarone Alterations in overall health status


Dyspnea Intemittent dyspnea – reversible process (CHF,asthma,pul.embolism) Nocturnal dyspnea – CHF,GERD, asthma Orthopnea – (recumbent position)– CHF, ascites,pregnancy,obst.lung ds, resp.muscle weakness Platypnea – (upright position)- AVmalformations at lung bases, interatrial shunts, cirrhosis Dyspnea on exertion – cardiac/pulmonary


Dyspnea Dyspnea independent of activity – mech (aspiration), allergic , psychological Trepopnea -(dyspnea in one lateral position but not the other) – pleural effusion , obst of prox tracheobronchial tree Paroxysmal nocturnal dyspnea – dyspnea, cough, frothy sputum streaked with blood, sweating, pallor , tachycardia , crackles – IHD, Aortic valve ds, AF, HTN, Cardiomyopathy.

NYHA Classification:

NYHA Classification Class 1 – No limitations.Ordinary physical activity does not cause dyspnea Class 2 – Slight limitation of physical activity. Class 3 – Marked limitation of physical activity. Class 4 – dyspnea at rest

Physical Examination:

Physical Examination Respiratory Rate Body habitus – cachexia / obesity Posture – leaning forward on elbows with COPD, supine in bed Use of Accessory muscles Pursed lips Lower extremity edema – b/l – CHF & u/l – thromboembolism Clubbing – malignancy Cyanosis – insensitive sign of severe hypoxemia Extent & Symmetry of chest expansion

Physical Examination:

Physical Examination Crackles, wheeze ( localised / diffuse ) Decreased breath sounds – pneumothorax , pleural effusion RV heave , increased P2 – pul.htn Elevated JVP , hepatojugular reflex, pedal edema – RV Failure Diffuse,lateral displaced pt of max impulse, S3 gallop ,crackles , elevated JVP – LV Failure

Causes – Acute Severe Dyspnea:

Causes – Acute Severe Dyspnea Cardiac : Pul.edema from myocardial dysfn,including ischemia & valvular dysfn. Pulmonary : Acute severe asthma, Acute exacerbation of COPD, Pneumothorax, Pneumonia, Pul.embolism, ARDS, Inhaled Foreign body , Laryngeal edema, Lobar Collapse, Pul.H’age, Aspiration, Bronchiolitis obliterans , inhaled toxins Others : Metabolic acidosis , Psychogenic Hyperventilation

Investigations For Acute Severe Dyspnea:

Investigations For Acute Severe Dyspnea ABC – establish airway and ensure oxygenation CXR PA View Arterial Blood Gases measurements ECG V/Q Scan Echocardiogram Spirometry HRCT CT pulmonary angiography


Remember Pulse Oximetry is not sufficient : Pt with N oxygenation & metabolic / resp acidosis can be dyspneic, -- need to exhale Co2 to raise pH. In Methemoglobinemia, the apparent O2 saturation is high , but actual PO2 is low.

Causes of Chronic Dyspnea:

Causes of Chronic Dyspnea Cardiac : CHF, Myocardial dysfn- cardiomyopathies, cong.anomalies, intracardiac Rt to Lt shunts, arrhythmias. Valvular heart ds, Constrictive pericarditis Pulmonary : COPD, Chr.asthma, Bronchial.Ca, ILD, Chr.pul.thromboembolism, Large Pleural Effusion, Neuro muscular weakness Others : Severe Anaemia , Obesity, Extra- pulmonary restrictions ( kyphoscoliosis, pleural effusion, fibro thorax )

Causes of Chronic Dyspnea:

Causes of Chronic Dyspnea Altered central ventilatory drive : central sleep apnea, obesity hypoventilation syn, idiopathic hyperventilation Metabolic : Increased metabolic needs (hyperthyroidism, obesity), Metabolic Acidosis ( renal failure ) Physiological : high altitude, vigorous exercise, pregnancy.

Investigations For Chronic Dyspnea:

Investigations For Chronic Dyspnea Careful & Comprehensive history & phy.ex to limit broad Diff.diagnosis. PFT, ABG, CXR PA View ECG Blood chemistries & CBC V/Q Scan Chest CT Thyroid Functioning Tests

Investigations For Chronic Dyspnea :

Investigations For Chronic Dyspnea Bronchoscopy Lung Biopsy Laryngoscopy


Management Distinguishing Cardiovascular from Respiratory System Dyspnea : If the pt has both pul & cardiac ds , a Cardiopulmonary Exercise Test – to determine which system is responsible for exercise limitation. If ,at peak exercise , pt achieves predicted max ventilation – increase in dead space / hypoxaemia / bronchospasm – RS inv.


Management If HR >85% of predicted max , if BP becomes very high / drops during exercise, ischemic changes in ECG – CVS inv. 1 st goal of treatment is to correct the underlying problem responsible for dyspnea. If not possible , atleast lessen the intensity of dyspnea & its effect on pt’s quality of life


Management Supplemental O2 – if resting O2 sat <90% COPD pts – pulmonary rehabilitation prog

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