DT

Module_8_-_Respiratory

Module 8: Chapter 5 Pathophysiology of Pulmonary Conditions

Respiratory System Overview

Two Divisions:

  1. Air Conduction:

    • Function: Delivers warm and moistened air to the lungs to enhance gas exchange and protect the pulmonary surfaces from irritation.

    • Components: Nose, mouth, trachea, bronchi, and bronchioles, each playing a crucial role in ensuring air is filtered, humidified, and warmed before reaching the alveoli.

  2. Gas Exchange:

    • Function: Exchanges vital gases, oxygen, and carbon dioxide between air and blood to maintain homeostasis and support cellular metabolism.

    • Components: Alveoli and capillaries, where the diffusion of gases occurs across the alveolar membrane into the bloodstream.

Key Structures of the Respiratory System

Anatomy:

  • Nasal Cavity: Filters, warms, and humidifies the air.

  • Throat (Pharynx): A passage that carries air to the larynx and food to the esophagus.

  • Nose and Mouth: Entry points for air, with the nose having a greater role in filtration due to cilia and mucus.

  • Esophagus: Not part of the respiratory system but runs parallel and serves as a food passage.

  • Larynx: Contains vocal cords and acts as a passageway for air while preventing food aspiration.

  • Trachea: Also known as the windpipe, it directs air into the bronchi.

  • Lungs (Left and Right): Main organs of respiration, each comprising lobes and alveoli where gas exchange occurs.

  • Alveoli: Tiny air sacs that increase surface area for gas exchange.

  • Capillary Venule Network: Surrounds alveoli, facilitating gas transport to and from blood.

  • Bronchiole and Bronchi: Airways that lead to the lungs, branching further into smaller bronchioles.

  • Diaphragm: A critical muscle that assists in breathing mechanics by contracting and relaxing to facilitate inhalation and exhalation.

Gas Exchange Mechanism

Requirements:

  • Adequate ventilation (air delivery) and perfusion (blood flow) are essential for effective gas exchange.

Normal Values:

  • Normal ventilation = 4 L/min.

  • Normal perfusion = 5 L/min.

  • Ventilation/perfusion (VQ) ratio: Normal range = 0.8, crucial for determining lung efficiency.

Factors Influencing VQ Ratio:

  • Alveolar and capillary surface area and thickness significantly affect the efficiency of gas exchange and the overall VQ ratio.

Gas Transportation

Oxygen Transport:

  • Mechanism: Oxygen is carried by hemoglobin (forming oxyhemoglobin), which easily releases oxygen to tissues influenced by local pH and temperature changes.

Carbon Dioxide Transport:

  • Carbon dioxide is primarily transported as bicarbonate ions (HCO3-), and its removal from the body is crucial for maintaining acid-base balance.

Lung Compliance

Importance:

  • Lung compliance, defined as the stretchability of lung tissue, is essential. High compliance indicates easier inflation, while low compliance can make breathing laborious.

Role of Surfactant:

  • Surfactant is a lipoprotein coating the alveoli, preventing collapse, reducing surface tension, and promoting reinflation during exhalation.

Pressure System:

  • Lungs function as a negative pressure system, facilitating airflow into the pulmonary pathways.

Breathing Process

Control:

  • The breathing process is largely involuntary, primarily managed by the medulla oblongata, which responds to changes in carbon dioxide and oxygen levels in the blood.

  • Chemoreceptors and Stretch Receptors: These regulate breathing rhythm and depth based on current physiological demands.

Inspiration:

  • Occurs through the contraction of the diaphragm and intercostal muscles, creating negative pressure that draws air into the lungs.

Expiration:

  • Typically a passive process that relies on the elastic recoil of lung tissue; active components may be involved during forceful expiration.

Hypoxic Drive with Chronic Elevated PCO2 Levels

Mechanism:

  • In patients with chronic elevated carbon dioxide (PCO2) levels, a hypoxic drive can develop, where low oxygen (PO2) levels stimulate increased respiration rates as a compensatory mechanism.

Pulmonary Function Tests (PFT)

Key Measurements:

  • Tidal Volume: ~500 mL, the amount of air inhaled or exhaled in a normal breath.

  • Minute Respiratory Volume: ~6 L, total volume of air inhaled and exhaled in one minute.

  • Inspiratory Reserve Volume: 2–3 L, additional air that can be inhaled after a normal inspiration.

  • Expiratory Reserve Volume: 1–1.5 L, additional air that can be forcibly exhaled after a normal expiration.

  • Vital Capacity: Total of tidal volume plus both reserves, representing the maximum amount of air a person can expel from the lungs.

  • Residual Volume: 1–1.5 L left after forced expiration, indicating the air that remains in the lungs to keep the alveoli open.

  • FEV1 vs. Forced Vital Capacity: Used in diagnosing and classifying obstructive and restrictive lung diseases.

Role in pH Balance

Regulation:

  • The rate and depth of breathing modulate the body’s pH levels by controlling carbon dioxide concentration in the blood.

  • Increased Breathing: Results in the expulsion of CO2, raising pH (alkalosis).

  • Decreased Breathing: Causes CO2 retention, lowering pH (acidosis).

Conditions of the Respiratory System

Lung Sounds:

  • Variations in lung sounds, including rales, crackles, wheezes, rhonchi, pleural friction rubs, and stridor, provide diagnostic insight into underlying conditions.

Influenza Overview

Nature:

  • Influenza is a viral infection affecting both the upper and lower respiratory tracts, leading to systemic symptoms.

Types:

  • Type A: Most severe and prevalent, often responsible for pandemics.

  • Type B: Generally less severe, seasonal outbreaks.

  • Type C: Causes mild respiratory illness, less common than A and B.

US Flu Season:

  • Typically spans from October through March, with peaks in December and February.

Manifestations:

  • Symptoms include low-grade fever, headache, dry cough, body aches, nasal congestion, chills, fatigue, and in some cases, secondary bacterial infections.

Diagnosis:

  • Based on patient history, physical examination, rapid antigen testing, and viral culture.

Treatment:

  • Antiviral medications, hydration, plenty of rest, antipyretics to reduce fever, and analgesics for pain relief.

Prevention:

  • Key methods include proper handwashing, avoiding crowded places during outbreaks, and annual vaccinations.

Pneumonia Overview

Definition:

  • Pneumonia is defined as an infection and inflammation of the lung parenchyma, leading to impaired gas exchange.

Causes:

  • Caused by infectious agents such as bacteria and viruses, and lung secretion stasis.

Types:

  • Viral Pneumonia: Generally mild, but can lead to secondary bacterial pneumonia.

  • Bacterial Pneumonia: Most common type; frequently caused by Streptococcus pneumoniae.

Complications:

  • Can lead to septicemia, pulmonary edema, lung abscess, and Acute Respiratory Distress Syndrome (ARDS).

Diagnosis and Treatment:

  • Diagnosis is based on clinical signs and symptoms, with management focusing on supportive care and antibiotics if bacterial.

Tuberculosis (TB)

Causative Agent:

  • Mycobacterium tuberculosis, a slow-growing, aerobic bacterium.

Transmission:

  • Primarily through airborne droplets generated when an infected person coughs or sneezes.

Manifestations:

  • May include a productive cough, hemoptysis (coughing up blood), night sweats, weight loss, and fatigue.

Diagnosis:

  • Conducted using the Mantoux test, chest X-ray, and sputum culture for confirmation.

Treatment:

  • Involves a combination of antimicrobial therapy for a minimum of six months to eradicate the bacteria and prevent resistance.

Asthma Overview

Definition:

  • Asthma is a chronic disorder characterized by intermittent airway obstruction caused by inflammation, bronchospasm, and increased mucus production.

Types:

  • Types include extrinsic (allergic), intrinsic (non-allergic), nocturnal, exercise-induced, occupational, and drug-induced asthma.

Stages of an Asthma Attack:

  • Stage One: Bronchospasms occur, leading to coughing and shortness of breath.

  • Stage Two: Airway edema and mucus production increase, further obstructing airflow.

Manifestations:

  • Common symptoms include wheezing, dyspnea (difficulty breathing), and chest tightness, which may increase during an attack.

Chronic Obstructive Pulmonary Disease (COPD)

Overview:

  • COPD encompasses a group of debilitating chronic disorders characterized by irreversible tissue degeneration affecting lung function.

Main Types:

  • Chronic Bronchitis: Features include a productive cough with increased mucus due to chronic inflammation.

  • Emphysema: Involves the destruction of the alveolar walls, leading to decreased surface area for gas exchange.

Case Study Analysis

Mr. Lansing:

  • Key Symptoms: Flushed skin, shortness of breath, diminished breath sounds, and no cough despite a significant smoking history.

Key Questions:

  • Diagnostic tests that are likely to be ordered include arterial blood gases (ABGs), complete blood count (CBC), and chest X-ray, aiming to identify underlying disease processes based on presented symptoms and clinical history.

Additional Respiratory Conditions

Pleural Effusion:

  • Refers to the accumulation of fluid in the pleural space, which can impair breathing and gas exchange.

Pneumothorax:

  • Air trapped in the pleural cavity, which can lead to lung collapse (atelectasis) and respiratory distress.

Pulmonary Embolism (PE):

  • A blockage in the pulmonary artery that commonly arises from deep vein thrombosis (DVT), resulting in acute respiratory compromise and possible infarction of lung tissue.

Acute Respiratory Distress Syndrome (ARDS):

  • A severe inflammatory response leading to fluid accumulation in the alveoli, resulting in rapid onset of respiratory failure and requiring intensive medical management.

Cystic Fibrosis:

  • A genetic disorder characterized by thick mucus production that obstructs airflow and leads to recurrent lung infections and damage.

Legionnaire's Disease and Pneumocystis Jirovecii Pneumonia:

  • Specific infectious agents known for causing pneumonia, particularly in immunocompromised patients and individuals with weakened immune systems.