Shortness of Breath

Below is a **complete, concise but fully detailed medical reference** for **Shortness of Breath (SOB / Dyspnea)** in the exact structured format you prefer.

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# **SHORTNESS OF BREATH (SOB / DYSPNEA)**

A complete medical reference (definition → pathophysiology → causes → clinical features → investigations → differential diagnosis → management with full drug details).

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## **1. Definition**

Shortness of breath (dyspnea) = **subjective sensation of difficult or uncomfortable breathing**.
It reflects mismatch between ventilatory demand and respiratory capacity.

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## **2. Pathophysiology**

SOB occurs due to one or more of:

* ↑ **respiratory drive** (hypoxia, acidosis, fever, pain)
* ↓ **lung compliance** (pneumonia, ARDS, fibrosis)
* ↑ **airway resistance** (asthma, COPD)
* ↓ **respiratory muscle function** (neuromuscular disorders)
* ↑ **cardiac preload/afterload** (heart failure)
* **V/Q mismatch** (PE, pneumonia)
* **Hypoxia or hypercapnia**

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## **3. Common Causes**

### **A. Respiratory Causes**

* Asthma
* COPD
* Pneumonia
* Pulmonary embolism
* Pneumothorax
* Pleural effusion
* Interstitial lung disease
* ARDS
* Upper airway obstruction
* Foreign body aspiration

### **B. Cardiac Causes**

* Congestive heart failure
* ACS / MI
* Arrhythmias
* Pericardial tamponade
* Valvular heart disease
* Cardiomyopathy
* Pulmonary hypertension

### **C. Non-Cardiac Non-Respiratory Causes**

* Severe anemia
* Metabolic acidosis (DKA, sepsis)
* Anxiety/panic attack
* Neuromuscular weakness (GBS, MG)
* Renal failure (uremia)

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## **4. Clinical Features**

### **Symptoms**

* Difficulty breathing
* Chest tightness
* Wheezing
* Orthopnea (heart failure)
* PND
* Cough ± sputum
* Fever (infection)
* Sudden pleuritic pain (PE, pneumothorax)

### **Signs**

* Tachypnea
* Tachycardia
* Use of accessory muscles
* Cyanosis
* Low SpO₂
* Wheeze (asthma/COPD)
* Crackles (pneumonia/CHF)
* Absent breath sounds (pneumothorax)
* Edema, JVP rise (heart failure)

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## **5. Investigations**

### **Immediate**

* **SpO₂**, ABG
* Chest X-ray
* ECG
* CBC (look for anemia/infection)
* Troponin, BNP
* Blood glucose, electrolytes

### **Further**

* CT chest (suspect PE/ILD)
* D-dimer
* Echocardiography
* PFTs
* Ultrasound thorax
* Sputum culture

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## **6. Differential Diagnosis (Important)**

* Asthma vs COPD
* Pneumonia vs heart failure
* Pulmonary embolism vs ACS
* Anxiety vs organic cause
* Pneumothorax vs pleural effusion
* Metabolic acidosis vs respiratory disease

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## **7. Management (Stepwise)**

### **A. Immediate Stabilization**

1. **ABC assessment**
2. **Oxygen therapy**

* Nasal cannula 2–4 L/min → Simple mask → NRBM
3. **If severe respiratory distress**

* NIV (BiPAP)
* Intubation if needed

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## **B. Cause-Specific Management (with full drug details)**

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### **1. Asthma**

**Drugs:**

#### **Salbutamol (Albuterol)**

* **Indication:** Acute asthma relief
* **MOA:** β2 agonist → bronchodilation
* **Dose:** 2–4 puffs OR nebulization 2.5 mg q20 min × 3
* **ADRs:** Tremor, tachycardia, hypokalemia
* **Contra:** Arrhythmias
* **Interactions:** Beta-blockers reduce effect
* **Monitoring:** HR, symptoms, SpO₂
* **Counseling:** Use spacer, step-up therapy if frequent use

#### **Ipratropium**

* **MOA:** Anticholinergic
* **Dose:** Neb 0.5 mg q20 min × 3
* **ADRs:** Dry mouth
* **Monitoring:** Resp improvement

#### **Steroids (Prednisolone / Methylprednisolone)**

* **MOA:** Anti-inflammatory
* **Dose:** Prednisolone 40–60 mg/day PO × 5 days
* **ADRs:** Hyperglycemia, mood changes
* **Contra:** Uncontrolled infections
* **Monitoring:** BP, glucose
* **Counseling:** Take with food

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### **2. COPD Exacerbation**

Same as asthma + **Antibiotics** if infective.

#### **Amoxicillin-Clavulanate**

* **Indication:** Bacterial COPD/pneumonia
* **MOA:** Cell wall inhibition + β-lactamase inhibition
* **Dose:** 625 mg TID × 5–7 days
* **ADRs:** Diarrhea, rash
* **Interactions:** Warfarin ↑ INR
* **Monitoring:** CBC, LFTs

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### **3. Heart Failure (CHF)**

#### **Furosemide**

* **Indication:** Pulmonary edema
* **MOA:** Loop diuretic
* **Dose:** 20–40 mg IV
* **ADRs:** Hypokalemia, dehydration
* **Monitoring:** Electrolytes, urine output

#### **ACE inhibitors (Enalapril)**

* **MOA:** Vasodilation → ↓ afterload
* **Dose:** 2.5–5 mg BID
* **ADRs:** Cough, hyperkalemia
* **Monitoring:** K+, creatinine

#### **Nitroglycerin (if BP OK)**

* **Dose:** 5–10 µg/min IV
* **ADRs:** Headache, hypotension

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### **4. Pulmonary Embolism**

#### **Enoxaparin**

* **Dose:** 1 mg/kg SC q12h
* **Monitoring:** Anti-Xa
* **ADRs:** Bleeding

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### **5. Pneumonia**

Antibiotics such as **Azithromycin**, **Ceftriaxone** depending on severity.

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### **6. Pneumothorax**

* Small → O₂ + observation
* Large → Needle decompression / chest tube

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### **7. Metabolic Acidosis**

Treat underlying cause (DKA → insulin, fluids; sepsis → antibiotics).

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### **8. Anxiety**

#### **Clonazepam**

* **Dose:** 0.25–0.5 mg
* **Caution:** Dependency, sedation

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## **8. Non-Pharmacologic Measures**

* Breathing exercises
* Positioning (tripod position)
* Steam inhalation (upper airway infections)
* Avoid smoke/allergens
* Weight reduction (if obese)
* Pulmonary rehab

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## **9. When to Seek Emergency Care**

* SpO₂ < 92%
* Severe chest pain
* Silent chest in asthma
* Sudden collapse
* Hemoptysis
* Severe cyanosis
* Not responding to inhalers
* Altered sensorium

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