![]() Anxiety and strenuous exercise in healthy individuals are more benign considerations.Ģ. Other etiologies of hypoventilation and hypercarbia include mechanical causes such as chest wall deformities, obesity hypoventilation syndrome ( OHS), and metabolic causes outlined below.Ĭ) Metabolic: This includes sensation of breathlessness caused by nonrespiratory acidosis (eg, lactic acidosis, diabetic ketoacidosis, renal tubular acidosis), thyrotoxicosis, stimulation of the respiratory center by endogenous toxins (toxins originating in the liver, uremic toxins) and exogenous toxins (salicylates).ĭ) Other: Abnormal tissue gas exchange can result from impaired oxygen binding by hemoglobin (eg, carbon monoxide poisoning and methemoglobinemia) or decreased cellular oxygen utilization (eg, with cyanide poisoning). ![]() Neuromuscular causes of hypoventilation can arise at the level of the muscle (myopathy or respiratory muscle/diaphragmatic weakness), neuromuscular junction (neuromuscular conduction abnormalities such as myasthenic crisis), or nerve conduction abnormalities (Guillain-Barré syndrome). ![]() Further categorization of specific causes includes cardiac ischemia, cardiac arrhythmia, valvular disease, and myopericardial disease.ī) Neuromuscular: This predominantly affects ventilatory drive and effort in the absence of gas exchange abnormalities. Pleural disease includes pleural effusions and malignancy, while pulmonary arterial diseases include pulmonary hypertension and pulmonary embolism.Ī) Cardiovascular: Dyspnea in cardiovascular disease is often driven by decreased cardiac output (shock or heart failure). Examples of parenchymal disease include infection, inflammatory or collagen vascular diseases, malignancy, and interstitial lung disease. Bronchial disease processes include inflammatory conditions such as chronic obstructive pulmonary disease ( COPD) and asthma. Alveolar disease processes may include infection, inflammation, and alveolar fluid (eg, in congestive heart failure). Underlying mechanisms can be broadly categorized as impaired gas exchange (both at the level of the lungs and tissue) or impaired ventilatory drive, in either case leading to perception of breathlessness.ġ) Pulmonary: Abnormal gas exchange may arise from dysfunction at the level of the alveoli, bronchi, lung parenchyma, pleura, or pulmonary vasculature. Causes of dyspnea according to the underlying pathophysiology: The pathophysiology of dyspnea is complex and often involves interaction between pulmonary and extrapulmonary (cardiovascular, neuromuscular, and oxygen delivery) systems. Examples:ġ) Modified Medical Research Council ( mMRC) dyspnea scale (available at ): A 4-point scale for evaluating activities that generate dyspnea as ranging from strenuous exercise (0 points) through walking up a slight hill (1 point), walking slower than peers (2 points), running out of breath after a few minutes’ walk on level ground (3 points), to getting dyspneic when dressing (4 points).Ģ) Borg scale (0, no dyspnea 5, severe dyspnea 10, maximal dyspnea).ģ) Disease-specific scales: The New York Heart Association ( NYHA) scale used to evaluate dyspnea in heart failure (see Table 3.8-1), ranging from dyspnea with strenuous exertion (stage 1) through dyspnea with ordinary physical activity (stage 2) to dyspnea with less than ordinary activity (stage 3) and dyspnea at rest (stage 4).ġ. Dyspnea can be characterized by its acuity and association with exertion and positioning as:ġ) Acute, intermittent or paroxysmal, and chronic dyspnea.Ģ) Dyspnea at rest and exertional dyspnea.ģ) Orthopnea, which refers to dyspnea occurring in the recumbent position and improving when sitting or standing.Ĥ) Platypnea, which refers to dyspnea increasing in the sitting or standing position.ĭyspnea severity scales help quantify breathlessness or disability associated with breathlessness. ![]() Authors: Wojciech Szczeklik, Miłosz Jankowskiĭyspnea is a subjective sensation of breathlessness or difficulty breathing.
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