Adult Health: Respiratory

Gas Exchange Basics

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Gas exchange occurs in the alveoli, tiny air sacs in the lungs surrounded by capillaries.

• Oxygen (O₂): Oxygen enters the alveoli during inhalation, diffuses across the alveolar-capillary membrane into the bloodstream, and binds to hemoglobin in red blood cells for transport to tissues.
• Carbon Dioxide (CO₂): Carbon dioxide, a waste product of cellular metabolism, diffuses from the bloodstream into the alveoli and is removed from the body during exhalation.

Figure A: Image showing an overview of gas exchange in the body.

High-Yield NCLEX Point: Hypoxia (Inadequate oxygen delivery to tissues) = priority problem. Low SpO₂ + respiratory distress = intervene immediately.

Oxygenation and ABG Interpretation

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Here are normal arterial blood gas (ABG) values:

Value	Normal Range
pH	7.35-7.45
PaCO₂	35-45 mmHg
HCO₃	22-26 mEq/L
PaO₂	80-100 mmHg

• pH: Overall acid–base status
• PaCO₂: Respiratory component (controlled by lungs)
• HCO₃: Metabolic component (controlled by kidneys)
• PaO₂: Oxygenation status

Respiratory Acidosis

Respiratory acidosis is an acid-base disorder occurring when lungs cannot remove enough carbon dioxide produced by the body.

• Low pH
• High CO₂

Cause: Hypoventilation (COPD, overdose)

Respiratory Alkalosis

Respiratory alkalosis is an acid-base imbalance characterized by high blood pH and low carbon dioxide.

• High pH
• Low CO₂

Cause: Hyperventilation (anxiety, PE)

High-Yield NCLEX Point: If CO₂ abnormal → respiratory problem. If HCO₃ abnormal → metabolic problem.

Oxygen Delivery Devices

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Here is a table summarizing various oxygen delivery devices:

Device	Flow Rate	Approximate O₂ %	Notes
Nasal Cannula	1-6 L/min	24-44%	Low-flow device used for mild hypoxia. Comfortable and allows eating/talking.
Simple Mask	5-10 L/min	40-60%	Delivers moderate oxygen concentrations. Must be at least 5 L/min to prevent CO₂ rebreathing.
Non-Rebreather	10-15 L/min	Up to 95%	High-concentration device with a reservoir bag. Delivers near 100% oxygen when properly fitted.

Respiratory Illnesses

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Here is a table summarizing various respiratory illnesses:

Condition	Description	Key Symptoms	Priority Nursing Interventions	Risk Factors / Notes
Pneumonia	Inflammation of lung tissue due to infection.	– Fever – Productive cough – Crackles – Dyspnea – Elevated WBC	– Oxygen – Antibiotics – Incentive spirometer – Early ambulation	Infection-related consolidation of lung tissue
COPD – Chronic Bronchitis	Long-term, irreversible obstructive lung disease characterized by chronic inflammation and mucus production.	– Productive cough – Cyanosis – Edema	– Low-flow oxygen – High Fowler’s position – Avoid respiratory depressants	Often referred to as “blue bloater”
COPD – Emphysema	Chronic, progressive obstructive lung disease caused primarily by smoking; destruction of alveoli.	– Prolonged expiration – Barrel chest – Thin appearance	– Low-flow oxygen – Pursed-lip breathing – High Fowler’s position	Often referred to as “pink puffer”
Asthma	Chronic inflammatory airway disease causing bronchoconstriction and reversible airway obstruction.	– Wheezing – Dyspnea – Chest tightness – Decreased breath sounds	– Short-acting beta agonist (rescue inhaler) – Inhaled corticosteroids – Oxygen	Triggered by allergens, exercise, infection
Pulmonary Embolism (PE)	Sudden blockage in a pulmonary artery, usually from a DVT.	– Sudden dyspnea – Chest pain – Tachycardia – Anxiety – Clear lungs – Hemoptysis	– Oxygen – Anticoagulants – Monitor for shock	– Immobility – Surgery – Cancer – Birth control
Acute Respiratory Distress Syndrome (ARDS)	Rapid-onset inflammatory lung injury causing fluid-filled alveoli and impaired gas exchange.	– Severe hypoxemia (PaO₂ < 60 mmHg) – Refractory to oxygen – Bilateral infiltrates on chest X-ray	– Mechanical ventilation – PEEP – Treat underlying cause	– Often secondary to sepsis, trauma, or pneumonia
Pneumothorax	Air in the pleural space causing partial or complete lung collapse.	– Sudden chest pain – Sudden dyspnea – Decreased or absent breath sounds on affected side – Possible tracheal deviation (tension pneumothorax)	– Oxygen – Chest tube insertion – Needle decompression (if tension pneumothorax)	– Spontaneous – Traumatic – Secondary to mechanical ventilation

Unfamiliar Terms

• Productive Cough: Brings up mucus or phlegm from the lungs or airways.
• Crackles: Rattling lung sounds heard with a stethoscope often indicating fluid or collapsed airways.
• Cyanosis: Bluish discoloration of the skin, lips or nail beds)
• Edema: Abnormal buildup of fluid in body tissues, causing swelling. Common in legs, feet, and ankles.
• Barrel Chest: A rounded, bulging, and enlarged chest.
• Pursed Lip Breathing: A technique that helps control shortness of breath by improving oxygenation and reducing respiratory rate.
• Dyspnea: Shortness of breath.
• Short Acting Beta Agonist: “Rescue” inhaler medications that quickly relax airway muscles to treat acute asthma symptoms, COPD flare-ups, and exercise-induced bronchospasm
• Corticosteroids: Powerful anti-inflammatory and immunosuppressant medications that mimic natural cortisol to treat conditions like asthma
• Tachycardia: Resting heart rate that exceeds 100 beats per minute.
• Hemoptysis: Coughing up of blood.
• PEEP: Positive end-expiratory pressure is the pressure maintained in the lungs at the end of expiration during mechanical ventilation.
• Bilateral Infiltrates on Chest X-Ray: Indicates widespread, fluid-filled or inflamed, air spaces in both lungs.
• Refractory to Oxygen: Hypoxemia that does not improve despite supplemental oxygen.
• Severe Hypoxemia: Low oxygen in the blood (PaO₂ <60 mmHg).

Mechanical Ventilation Basics

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Mechanical ventilation provides breathing support when a patient cannot adequately oxygenate or ventilate on their own. It delivers oxygen under positive pressure through an endotracheal (ET) tube.

Indications

• Respiratory Failure: Elevated CO₂ or low O₂ despite oxygen therapy
• Severe Hypoxemia: Low oxygen in the blood (PaO₂ <60 mmHg)
• Decreased Level of Consciousness (LOC): A decreased LOC with inability to protect airway

Key Priorities

• Assess breath sounds and chest rise (verify tube placement and lung expansion)
• Monitor oxygenation and ABGs
• Prevent ventilator-associated pneumonia (VAP)
  • Oral care every 2-4 hours
  • Elevate head of bed 30-45 degrees
  • Suction as needed using sterile technique

High-Yield Respiratory Medications

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Here is a table of some important respiratory medications you should be familiar with:

Medication Class	What It Does	Example	Key Nursing Consideration
Short Acting Beta Agonist	Rapidly relaxes bronchial smooth muscle to open airways during acute bronchospasm.	Albuterol	Monitor HR
Corticosteroids	Reduce airway inflammation and suppress immune response.	Prednisone	Monitor glucose
Anticholinergics	Block acetylcholine to prevent bronchoconstriction and decrease mucus production.	Ipratropium	Dry mouth
Mucolytics	Thin and loosen respiratory secretions to improve airway clearance.	Acetylcysteine	Thin secretions
Anticoagulants	Prevent formation and extension of blood clots.	Heparin	Monitor bleeding

Priority Assessment Findings

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Here are the most concerning assessment findings:

• Stridor: High-pitched sound on inspiration indicating upper airway obstruction. This is an emergency.
• Absent Breath Sounds: May indicate pneumothorax, severe obstruction, or complete airway compromise.
• SpO₂ <90%: Indicates significant hypoxemia and inadequate oxygenation.
• Altered Mental Status: Restlessness, confusion, or lethargy are early signs of hypoxia.
• Use of Accessory Muscles: Neck and chest muscle retractions signal increased work of breathing and respiratory distress.
• Cyanosis: Bluish discoloration of lips or nail beds = a late and serious sign of hypoxia.

NCLEX High-Yield Point: Airway first. Airway → Breathing → Circulation (ABCs).

Image Source: “Pulmonary Gas Exchange“, by Delldot [CC BY 4.0]