Chapter 31: Disorders of Ventilation and Gas Exchange

Gases of Respiration Primary function of respiratory system Remove CO2 Addition of O2 Insufficient exchange of gasses Hypoxemia Hypercapnia

Hypoxemia Hypoxemia results from An inadequate O2 in the air Disease of the respiratory system Dysfunction of the neurological system Alterations in circulatory function Mechanisms Hypoventilation Impaired diffusion of gases Inadequate circulation of blood through the pulmonary capillaries Mismatching of ventilation and perfusion

Manifestations of Hypoxemia #1 Mild hypoxemia Metabolic acidosis Increase in heart rate Peripheral vasoconstriction Diaphoresis Increase in blood pressure Slight impairment of mental performance

Manifestations of Hypoxemia #2 Chronic hypoxemia Manifestations of chronic hypoxia may be insidious in onset and attributed to other causes. Compensation masks condition. Increased ventilation Pulmonary vasoconstriction Increased production of red blood cells Cyanosis

Hypercapnia Increased arterial PCO2 Caused by hypoventilation or mismatching of ventilation and perfusion Effects Acid–base balance (decreased pH, respiratory acidosis) Kidney function Nervous system function Cardiovascular function

Disorders of the Pleura Pleural effusion: abnormal collection of fluid in the pleural cavity Transudate or exudate, purulent (containing pus), chyle, or sanguineous (bloody) Hemothorax Pleuritis Chylothorax Atelectasis Empyema

Types of Pneumothoraxes Spontaneous Pneumothorax Occurs when an air-filled blister on the lung surface ruptures Traumatic Pneumothorax Caused by penetrating or nonpenetrating injuries Tension Pneumothorax Occurs when the intrapleural pressure exceeds atmospheric pressure

Causes of Disorders of Lung Inflation Conditions that produce lung compression or lung collapse Compression of the lung by an accumulation of fluid in the intrapleural space Complete collapse of an entire lung as in pneumothorax Collapse of a segment of the lung as in atelectasis

Characteristics and Symptoms of Pleural Pain Abrupt in onset Unilateral; localized to lower and lateral part of the chest May be referred to the shoulder Usually made worse by chest movements Tidal volumes are kept small. Breathing becomes more rapid. Reflex splinting of the chest may occur.

Pleural Effusion Definition An abnormal collection of fluid in the pleural cavity Types of fluid Transudate Exudate Purulent drainage (empyema) Chyle Blood

Diagnosis and Treatment of Pleural Effusion Chest radiographs, chest ultrasound Computed tomography (CT) Treatment: directed at the cause of the disorder Thoracentesis Injection of a sclerosing agent into the pleural cavity Open surgical drainage

Atelectasis Definition The incomplete expansion of a lung or portion of a lung Causes Airway obstruction Lung compression such as that occurs in pneumothorax or pleural effusion Increased recoil of the lung due to loss of pulmonary surfactant

Types of Atelectasis Primary Present at birth Secondary Develops in the neonatal period or later in life

Question #1 Which of the following is a disorder caused by abnormal accumulation of fluid in the pleural space? Pneumothorax Pleural effusion Atelectasis Hypercapnia

Answer to Question #1 B. Pleural effusion Rationale: Pleural effusion can be caused by transudate, exudate, chyle, or other fluid.

Physiology of Airway Disease Upper respiratory tract Trachea and major bronchi Lower respiratory tract Bronchi and alveoli Creation of negative pressure Effects of CO2/pH Role of inflammatory mediators Increase airway responsiveness by: Producing bronchospasm Increasing mucus secretion Producing injury to the mucosal lining of the airways

Functions of Bronchial Smooth Muscle The tone of the bronchial smooth muscles surrounding the airways determines airway radius. The presence or absence of airway secretions influences airway patency. Bronchial smooth muscle is innervated by the autonomic nervous system. Parasympathetic: vagal control Bronchoconstrictor Sympathetic: β2-adrenergic receptors Bronchodilator

Factors Contributing to the Development of an Asthmatic Attack Allergens Respiratory tract infections Exercise Drugs and chemicals Hormonal changes and emotional upsets Airborne pollutants Gastroesophageal reflux

Factors Involved in the Pathophysiology of Asthma Genetic Atopy Early versus late phase Environmental Viruses Allergens Occupational exposure

Classifications of Asthma Severity Mild intermittent Mild persistent Moderate persistent Severe persistent

Question #2 Which of the following has not been implicated in the development of asthma? Allergens Respiratory tract infections Diet Drugs and chemicals Hormonal changes and emotional upsets Airborne pollutants Gastroesophageal reflux

Answer to Question #2 C. Diet Rationale: Diet does not affect the respiratory tract other than via allergic reactions.

Chronic Obstructive Airway Disease Inflammation and fibrosis of the bronchial wall Hypertrophy of the submucosal glands Hypersecretion of mucus Loss of elastic lung fibers Impairs the expiratory flow rate, increases air trapping, and predisposes to airway collapse Alveolar tissue Decreases the surface area for gas exchange

Causes of Chronic Obstructive Airway Disease Chronic bronchitis Emphysema Bronchiectasis Cystic fibrosis

Types of Chronic Obstructive Pulmonary Disease Emphysema Enlargement of air spaces and destruction of lung tissue Types: centriacinar and panacinar Chronic Obstructive Bronchitis Obstruction of small airways

Characteristics of Type A Pulmonary Emphysema Smoking history Age of onset: 40 to 50 years Often dramatic barrel chest Weight loss Decreased breath sounds Normal blood gases until late in disease process Cor pulmonale only in advanced cases Slowly debilitating disease

Characteristics of Type B Chronic Bronchitis #1 Smoking history Age of onset 30 to 40 years Barrel chest may be present Shortness of breath, a predominant early symptom Rhonchi often present Sputum frequent, an early manifestation

Characteristics of Type B Chronic Bronchitis #2 Often dramatic cyanosis Hypercapnia and hypoxemia may be present. Frequent cor pulmonale and polycythemia Numerous life-threatening episodes due to acute exacerbations

Bronchiectasis Permanent dilation of the bronchi and bronchioles Secondary to persisting infection or obstruction Manifestations Atelectasis Obstruction of the smaller airways Diffuse bronchitis Recurrent bronchopulmonary infection Coughing; production of copious amounts of foul- smelling, purulent sputum; and hemoptysis Weight loss and anemia are common.

Cystic Fibrosis Definition An autosomal recessive disorder involving fluid secretion in the exocrine glands and the epithelial lining of the respiratory, gastrointestinal, and reproductive tracts Cause Mutations in a single gene on the long arm of chromosome 7 that encodes for the cystic fibrosis transmembrane regulator (CFTR), which functions as a chloride (Cl−) channel in epithelial cell

Manifestations of Cystic Fibrosis Pancreatic exocrine deficiency Pancreatitis Elevation of sodium chloride in the sweat Excessive loss of sodium in the sweat Nasal polyps Sinus infections Cholelithiasis

Diffuse Interstitial Lung Diseases Definition A diverse group of lung disorders that produce similar inflammatory and fibrotic changes in the interstitium or interalveolar septa of the lung Types Sarcoidosis The occupational lung diseases Hypersensitivity pneumonitis Lung diseases caused by exposure to toxic drugs

Occupational Lung Diseases Pneumoconioses The inhalation of inorganic dusts and particulate matter Hypersensitivity diseases The inhalation of organic dusts and related occupational antigens Byssinosis: cotton workers; has characteristics of the pneumoconioses and hypersensitivity lung disease

Pulmonary Embolism Development A blood-borne substance lodges in a branch of the pulmonary artery and obstructs the flow Types Thrombus: arising from DVT Fat: mobilized from the bone marrow after a fracture or from a traumatized fat depot Amniotic fluid: enters the maternal circulation after rupture of the membranes at the time of delivery

Pulmonary Hypertension Signs and Symptoms of Secondary Pulmonary Hypertension Dyspnea and fatigue Peripheral edema Ascites Signs of right heart failure (cor pulmonale) A disorder characterized by an elevation of pressure within the pulmonary circulation Pulmonary arterial hypertension

Cor Pulmonale Right heart failure resulting from primary lung disease and long-standing primary or secondary pulmonary hypertension Involves hypertrophy and the eventual failure of the right ventricle Manifestations include the signs and symptoms of the primary lung disease and the signs of right-sided heart failure.

Acute Respiratory Distress Syndrome A number of conditions may lead to ALI/ARDS. They all produce similar pathologic lung changes that include diffuse epithelial cell injury with increased permeability of the alveolar–capillary membrane.

Causes of ARDS Aspiration of gastric contents Major trauma (with or without fat emboli) Sepsis secondary to pulmonary or nonpulmonary infections Acute pancreatitis Hematologic disorders Metabolic events Reactions to drugs and toxins

Causes of Respiratory Failure Impaired ventilation Upper airway obstruction Weakness of paralysis of respiratory muscles Chest wall injury Impaired matching of ventilation and perfusion Impaired diffusion Pulmonary edema Respiratory distress syndrome

Treatment of Respiratory Failure Respiratory supportive care directed toward maintenance of adequate gas exchange Establishment of an airway Use of bronchodilating drugs Antibiotics for respiratory infections Ensure adequate oxygenation

Question #3 Which of the following has been implicated as a causative factor in right ventricular failure? Cor pulmonale Pneumothorax Cystic fibrosis ARDS

Answer to Question #3 A. Cor pulmonale Rationale: Cor pulmonale will result in RV failure due to the increase in workload that will result.