Ch 40: Oxygenation and Perfusion

Overview

This chapter explores the essential components and processes of the respiratory and cardiovascular systems, focusing on oxygenation, perfusion, and the maintenance of normal respiratory function. Understanding these concepts is crucial for medical terminology students, as they form the basis for interpreting clinical terms and patient care strategies.

Factors Essential to Normal Respiratory Function

• Integrity of the Airway System: Ensures air is transported to and from the lungs efficiently.

• Properly Functioning Alveolar System: Responsible for oxygenating venous blood and removing carbon dioxide.

• Effective Cardiovascular and Blood Supply: Delivers nutrients and removes wastes from body cells.

Anatomy of the Respiratory System

Upper Airway

• Function: Warms, filters, and humidifies inspired air.

• Components: Nose, pharynx, larynx, epiglottis.

Lower Airway (Tracheobronchial Tree)

• Functions: Conducts air, mucociliary clearance, produces pulmonary surfactant.

• Components: Trachea, right and left mainstem bronchi, segmental bronchi, terminal bronchioles.

Anatomy of the Lungs

• Main Organs of Respiration: Extend from the diaphragm base to the apex above the first rib.

• Lobes: Right lung has three lobes; left lung has two.

• Alveoli: Small air sacs where gas exchange occurs.

• Surfactant: Reduces surface tension, preventing alveolar collapse.

• Pleura: Serous membrane lining the lungs (visceral) and thoracic cavity (parietal).

Respiratory Function

Pulmonary Ventilation

• Definition: Movement of air into and out of the lungs (inspiration and expiration).

• Inspiration: Active phase; diaphragm contracts and descends, external intercostal muscles lift ribs, increasing thoracic volume and decreasing pressure.

• Expiration: Passive phase; relaxation of muscles decreases thoracic volume, increasing pressure and expelling air.

Gas Exchange (Respiration)

• Definition: Intake of oxygen and release of carbon dioxide.

• Mechanism: Occurs via diffusion between alveoli and capillaries.

• Perfusion: Oxygenated capillary blood passes through body tissues.

Key Question Example

• Which respiratory organ is the site of gas exchange? Answer: Alveoli. Rationale: Alveoli are clusters at the end of terminal bronchioles, with thin walls allowing gas exchange with capillaries.

Factors Influencing Gas Diffusion in the Lungs

• Surface area available for diffusion

• Thickness of the alveolar–capillary membrane

• Partial pressure of gases

• Solubility and molecular weight of the gas

Transport of Respiratory Gases

• Oxygen: Carried in plasma and red blood cells, mostly as oxyhemoglobin (97%).

• Carbon Dioxide: Carried by hemoglobin as carboxyhemoglobin.

• Internal Respiration: Exchange of gases between circulating blood and tissue cells.

Alterations in Respiratory Function

• Hypoxia: Inadequate oxygen available to cells.

• Dyspnea: Difficulty breathing.

• Hypoventilation: Decreased rate or depth of air movement into the lungs.

Cardiovascular System and Oxygenation

• Heart: Main organ of circulation; two atria and two ventricles.

• Hemoglobin: Binds and transports oxygen and carbon dioxide.

• Electrical Impulses: Control heart contraction (SA node, AV node, AV bundle).

Alterations in Cardiovascular Function

• Dysrhythmia or arrhythmia

• Myocardial ischemia

• Angina

• Myocardial infarction

• Heart failure

Factors Affecting Cardiopulmonary Functioning and Oxygenation

• Level of health

• Developmental considerations

• Medication considerations

• Lifestyle considerations

• Environmental considerations

• Psychological health considerations

Respiratory Activity Across the Lifespan

Infants

• Lungs transition from fluid-filled to air-filled at birth.

• Small chest, short airways; risk of aspiration.

• Rapid respiratory rate; primarily abdominal breathing.

• Synthetic surfactant may be administered to reopen alveoli.

• Crackles at end of deep respiration are normal.

Children

• Chest wall landmarks less prominent due to subcutaneous fat.

• Eustachian tubes, bronchi, and bronchioles become elongated and less angular.

• Frequency of infections decreases with age and immune system development.

• Hand hygiene and tissue etiquette are important preventive measures.

Older Adults

• Bony landmarks more prominent due to fat loss.

• Kyphosis and barrel chest may develop.

• Tissues and airways become more rigid; diaphragm less efficient.

• Increased risk for diseases, especially pneumonia.

Assessment of Respiratory System

Nursing History

• Usual respiratory patterns

• Medications and health history

• Recent changes, lifestyle, and environment

• Cough, sputum, pain, dyspnea, fever, fatigue

Physical Assessment

• Inspection: General appearance, color, chest structure, respiratory rate, rhythm, depth

• Palpation: Temperature, chest expansion, tenderness, masses, pulsations

• Percussion: Lung position, tissue density

• Auscultation: Breath sounds

Normal Breath Sounds

• Vesicular: Low-pitched, soft, heard over most lungs during expiration

• Bronchial: High-pitched, longer, heard over trachea

• Bronchovesicular: Medium pitch, heard over upper anterior chest and intercostal area

Abnormal (Adventitious) Breath Sounds

• Crackles: Intermittent sounds from air moving through fluid-filled airways; classified as fine, medium, or coarse

• Wheezes: Continuous, musical sounds from air passing through constricted airways; classified as sibilant or sonorous

Diagnostic Methods for Cardiopulmonary Function

• Electrocardiography (ECG)

• Pulmonary function studies (e.g., spirometry)

• Peak expiratory flow rate

• Pulse oximetry

• Capnography

• Thoracentesis

• Laboratory studies: arterial blood gas, cardiac biomarkers, CBC, cytologic studies

Pulmonary Function Test Values

Promoting Optimal Respiratory Function

• Healthy lifestyle choices (e.g., smoking cessation, exercise)

• Vaccinations (influenza, pneumococcal, COVID-19)

• Pollution-free environment

• Reducing anxiety and maintaining good nutrition

• Promoting comfort and proper breathing techniques

• Controlling coughing and performing chest physiotherapy

• Meeting oxygen needs with medications

Proper Breathing Techniques

• Deep breathing

• Incentive spirometry

• Pursed-lip breathing

• Diaphragmatic breathing

Medications for Respiratory Support

• Cough suppressants, expectorants, lozenges

• Bronchodilators: Open narrowed airways

• Mucolytic agents: Break down mucus

• Corticosteroids: Reduce inflammation

• Antihistamines: Reduce allergic responses

• Leukotriene receptor antagonists: Block inflammatory mediators

Administering Inhaled Medications

• Bronchodilators: Open airways

• Nebulizers: Disperse fine particles of medication

• Meter-dose inhalers (MDI): Deliver controlled dose with each compression

• Dry powder inhalers: Breath-activated delivery

Oxygen Therapy and Airway Management

Providing Supplemental Oxygen

• Oxygen source, flow rate, humidification

• Delivery systems: nasal cannula, simple mask, nonrebreather, Venturi mask

Managing Chest Tubes

• Assist with insertion/removal

• Monitor respiratory status and vital signs

• Check dressing and maintain drainage system integrity

Precautions for Oxygen Administration

• Avoid open flames

• Post "no smoking" signs

• Ensure electrical equipment is safe

• Avoid synthetic fabrics and oils

Types of Artificial Airways

• Oropharyngeal and nasopharyngeal airways

• Endotracheal tube

• Tracheostomy tube

Nursing Skills to Support Respiration

• Tracheal suctioning

• Assisting with mechanical ventilation

• Clearing obstructed airway

• Administering cardiopulmonary resuscitation (CPR)

Key Equations and Definitions

• Partial Pressure of Oxygen (PaO2): Where: = fraction of inspired oxygen, = atmospheric pressure, = water vapor pressure, = partial pressure of CO2, = respiratory quotient. Additional info: This equation is used to estimate alveolar oxygen pressure.

• Oxygen Content in Blood: Where: = hemoglobin concentration, = arterial oxygen saturation, = partial pressure of oxygen.

Summary Table: Normal vs. Abnormal Breath Sounds

Conclusion

Understanding the structure and function of the respiratory and cardiovascular systems, as well as the terminology associated with oxygenation and perfusion, is essential for effective patient care and communication in medical settings. Mastery of these concepts supports accurate assessment, diagnosis, and intervention in clinical practice.