Pharmacology for Nurses Unit 23 Review: Respiratory System Basics for Nurses

Key Concepts and Terminology

• Respiration involves the exchange of gases between the environment and the body's cells to support cellular metabolism and homeostasis
• Ventilation refers to the mechanical process of breathing, which includes inspiration (inhalation) and expiration (exhalation) of air into and out of the lungs
• Gas exchange occurs primarily in the alveoli, where oxygen diffuses from the lungs into the bloodstream and carbon dioxide diffuses from the bloodstream into the lungs to be exhaled
• Oxygenation is the process of providing adequate oxygen to the body's tissues to support cellular function and prevent hypoxia (oxygen deficiency)
• Perfusion involves the delivery of oxygenated blood to the body's tissues through the circulatory system
• Pulmonary ventilation is regulated by the respiratory center in the brainstem, which responds to changes in blood pH, carbon dioxide levels, and oxygen levels
• Key terms include dyspnea (shortness of breath), hypoxemia (low oxygen levels in the blood), hypercapnia (high carbon dioxide levels in the blood), and respiratory failure (inability to maintain adequate gas exchange)

Anatomy and Physiology of the Respiratory System

• The respiratory system consists of the upper and lower respiratory tracts, which work together to facilitate breathing and gas exchange
• The upper respiratory tract includes the nose, nasal cavity, pharynx, and larynx, which filter, warm, and humidify incoming air
• The lower respiratory tract comprises the trachea, bronchi, bronchioles, and alveoli, where gas exchange takes place
• The lungs are the primary organs of the respiratory system, containing millions of alveoli surrounded by capillaries for efficient gas exchange
  • The right lung has three lobes, while the left lung has two lobes to accommodate the heart's position
• The diaphragm is the primary muscle of respiration, contracting during inspiration to increase the volume of the thoracic cavity and relaxing during expiration
• The pleura is a thin, double-layered membrane that surrounds each lung, reducing friction during breathing and maintaining negative pressure within the thoracic cavity
• The respiratory system works in close coordination with the cardiovascular system to ensure adequate oxygenation and removal of carbon dioxide from the body's tissues

Common Respiratory Disorders

• Asthma is a chronic inflammatory disorder characterized by airway hyperresponsiveness, inflammation, and reversible airflow obstruction, often triggered by allergens, irritants, or exercise
• Chronic obstructive pulmonary disease (COPD) is a progressive condition that encompasses chronic bronchitis and emphysema, leading to persistent airflow limitation and respiratory symptoms
• Pneumonia is an infection of the lung tissue caused by bacteria, viruses, or fungi, resulting in inflammation, fluid accumulation, and impaired gas exchange
• Acute respiratory distress syndrome (ARDS) is a severe, life-threatening condition characterized by widespread inflammation and fluid buildup in the lungs, leading to hypoxemia and respiratory failure
• Interstitial lung disease (ILD) refers to a group of disorders that cause scarring (fibrosis) or inflammation of the lung tissue, impairing gas exchange and leading to respiratory symptoms
• Sleep apnea is a disorder characterized by repeated episodes of complete or partial airway obstruction during sleep, leading to intermittent hypoxemia and sleep disturbances
• Respiratory infections, such as the common cold, influenza, and bronchitis, can cause inflammation, increased mucus production, and temporary airway obstruction

Pharmacological Interventions

• Bronchodilators, such as beta-2 agonists (albuterol) and anticholinergics (ipratropium), relax smooth muscles in the airways to improve airflow and relieve bronchospasm
• Corticosteroids, such as inhaled beclomethasone or oral prednisone, reduce inflammation in the airways and prevent exacerbations of asthma and COPD
• Leukotriene modifiers, such as montelukast, block the action of leukotrienes, which are inflammatory mediators that contribute to airway inflammation and bronchoconstriction
• Methylxanthines, such as theophylline, act as bronchodilators and may have anti-inflammatory effects, but their use is limited due to potential side effects and drug interactions
• Mucolytics, such as acetylcysteine, help thin and loosen mucus secretions, making them easier to clear from the airways
• Antibiotics are used to treat bacterial respiratory infections, such as pneumonia and acute exacerbations of chronic bronchitis
• Oxygen therapy is used to treat hypoxemia and improve oxygenation in patients with respiratory disorders, delivered through nasal cannulas, masks, or mechanical ventilation

Drug Classes and Mechanisms of Action

• Beta-2 agonists (albuterol, salmeterol) stimulate beta-2 receptors in the airways, leading to relaxation of smooth muscles and bronchodilation
• Anticholinergics (ipratropium, tiotropium) block the action of acetylcholine on muscarinic receptors, reducing bronchoconstriction and mucus secretion
• Inhaled corticosteroids (beclomethasone, fluticasone) reduce airway inflammation by suppressing the production of inflammatory mediators and immune cell activity
  • Oral corticosteroids (prednisone) are used for more severe exacerbations or when inhaled corticosteroids are insufficient
• Leukotriene modifiers (montelukast, zafirlukast) inhibit the action of leukotrienes, which are potent bronchoconstrictors and inflammatory mediators
• Methylxanthines (theophylline) act as nonselective phosphodiesterase inhibitors, leading to bronchodilation and potential anti-inflammatory effects
• Mucolytics (acetylcysteine) break down mucus by cleaving disulfide bonds in mucoproteins, reducing mucus viscosity and facilitating expectoration
• Antibiotics target specific bacterial pathogens, inhibiting cell wall synthesis, protein synthesis, or DNA replication to prevent bacterial growth and promote clearance

Administration and Dosing Considerations

• Inhaled medications, such as bronchodilators and corticosteroids, are delivered directly to the airways using metered-dose inhalers (MDIs), dry powder inhalers (DPIs), or nebulizers
  • Proper inhaler technique is crucial for optimal drug delivery and effectiveness
• Oral medications, such as corticosteroids, leukotriene modifiers, and antibiotics, are administered in tablet or liquid form and absorbed through the gastrointestinal tract
• Dosing of respiratory medications depends on the patient's age, weight, severity of the condition, and response to treatment
  • Some medications, such as bronchodilators, are used as needed for symptom relief, while others, like inhaled corticosteroids, are used regularly for long-term control
• Patients with renal or hepatic impairment may require dose adjustments or alternative medications to avoid accumulation or adverse effects
• Drug interactions should be considered when prescribing respiratory medications, particularly with antibiotics, corticosteroids, and methylxanthines
• Oxygen therapy is prescribed based on the patient's oxygen saturation levels and clinical presentation, with the goal of maintaining adequate oxygenation while minimizing the risk of oxygen toxicity

Side Effects and Adverse Reactions

• Beta-2 agonists can cause tremors, tachycardia, palpitations, and hypokalemia, particularly at high doses or with prolonged use
• Anticholinergics may cause dry mouth, urinary retention, and constipation, especially in older patients or those with pre-existing urinary or gastrointestinal issues
• Inhaled corticosteroids can cause local side effects, such as oral candidiasis and hoarseness, which can be minimized by using a spacer device and rinsing the mouth after inhalation
  • Long-term use of oral corticosteroids may lead to systemic side effects, including hyperglycemia, osteoporosis, and adrenal suppression
• Leukotriene modifiers may cause headache, gastrointestinal upset, and elevated liver enzymes, requiring monitoring in some patients
• Methylxanthines have a narrow therapeutic window and can cause nausea, vomiting, tachycardia, and seizures at toxic levels
• Antibiotics may cause gastrointestinal side effects, allergic reactions, and potential drug interactions, necessitating careful selection and monitoring
• Oxygen therapy can cause dryness of the nasal passages and, in rare cases, oxygen toxicity, which may lead to lung damage and respiratory failure if not properly monitored

Patient Assessment and Monitoring

• Assess respiratory rate, depth, and effort, as well as the presence of cough, sputum production, and chest pain or discomfort
• Monitor oxygen saturation levels using pulse oximetry to evaluate the effectiveness of oxygenation and guide oxygen therapy
• Perform lung auscultation to identify abnormal breath sounds, such as wheezes, crackles, or diminished breath sounds, which may indicate airway obstruction, fluid accumulation, or atelectasis
• Obtain arterial blood gas (ABG) measurements to assess the patient's oxygenation, ventilation, and acid-base status, particularly in critical care settings
• Monitor peak expiratory flow rates (PEFR) in patients with asthma to assess airflow limitation and response to bronchodilator therapy
• Assess the patient's response to medications, including symptom relief, side effects, and adherence to the prescribed regimen
• Regularly review the patient's medication list and adjust therapy as needed based on clinical response, adverse effects, and changes in the patient's condition

Nursing Considerations and Care Planning

• Educate patients and caregivers about the proper use of inhalers, nebulizers, and oxygen delivery devices to ensure optimal drug delivery and effectiveness
• Teach patients to recognize signs and symptoms of respiratory distress, such as dyspnea, cyanosis, and increased work of breathing, and when to seek medical attention
• Encourage smoking cessation and avoidance of environmental triggers, such as allergens and irritants, to prevent exacerbations of respiratory conditions
• Promote regular exercise, breathing techniques, and pulmonary rehabilitation to improve respiratory function and quality of life
• Ensure adequate hydration and humidification to thin secretions and facilitate expectoration, particularly in patients with COPD or cystic fibrosis
• Implement infection control measures, such as hand hygiene and respiratory isolation, to prevent the spread of respiratory infections in healthcare settings
• Collaborate with the interprofessional team, including physicians, respiratory therapists, and pharmacists, to develop comprehensive care plans and optimize patient outcomes
• Provide emotional support and counseling to patients and families coping with chronic respiratory conditions, addressing concerns about quality of life, treatment adherence, and end-of-life care when appropriate