Basic Principles of Critical Care

1. RESPIRATORY SYSTEM ANATOMY &
PHYSIOLOGY
Gradian Health Systems
Basic Principles of Critical Care
RESPIRATORY SYSTEM

2. Disclaimer
Basic Principles of Critical Care Training I Respiratory System Anatomy and Physiology
Disclaimer: Gradian Health Systems cannot provide formal recommendations or indications
regarding medical care and clinical service delivery. The tables, checklists, and other clinical
documents referenced in this training have not been validated in all settings. These documents are
intended to serve as examples only. We recognize that all clinical training content and activities
must be customized to meet the needs of each facility and its clinical staff, factoring in available
resources, practitioner skill level, and other environmental considerations.
For any questions regarding the contents or applications of this training,
please contact Gradian Health Systems:
40 W 25th St, 6th Floor
New York, NY 10010 USA
+1 212-537-0340
training@gradianhealth.org

3. Module 2
Gradian Health Systems
Basics Principles of Critical Care
Respiratory System

4. Module 2: Respiratory System
MODULE OVERVIEW
Lesson 1 I Respiratory System Anatomy and Physiology
Lesson 2 I Oxygen Therapy
Lesson 3 I Evaluation of the Respiratory System
Lesson 4 I Airway Equipment and Management
Lesson 5 I Invasive and Non-invasive Ventilation
Lesson 6 I Basics of Mechanical Ventilation
Lesson 7 I Ventilator Modes and Settings
Lesson 8 I Ventilation Complications
Basic Principles of Critical Care Training I Respiratory System Anatomy and Physiology

5. Components of the Gradian CCV SystemLesson 1: Respiratory Anatomy and Physiology
Lesson Objectives
• Identify and describe relevant anatomy of the respiratory
• Define terms related to respiratory physiology
• Describe the mechanism and control of breathing
• Summarize gaseous exchange
Basic Principles of Critical Care Training I Respiratory System Anatomy and Physiology

6. Components of the Gradian CCV SystemLesson 1: Respiratory Anatomy and Physiology
Key Concepts
• Respiratory anatomy
• Mechanics of breathing
• Control of breathing
Basic Principles of Critical Care Training I Respiratory System Anatomy and Physiology

7. Components of the Gradian CCV SystemRespiratory Anatomy and Physiology
Basic Principles of Critical Care Training I Respiratory System Anatomy and Physiology
Anatomy
The main functions of the respiratory system are to:
• Provide oxygen to body tissues for cellular respiration
• Remove the waste product carbon dioxide
• Help to maintain acid-base balance

8. Components of the Gradian CCV SystemRespiratory Anatomy and Physiology
Basic Principles of Critical Care Training I Respiratory System Anatomy and Physiology
The upper airway is from the nasal
and oral cavities, the pharynx
(nasopharynx, oropharynx, and
laryngopharynx) to the level of the
larynx. The lower airway starts from
the trachea and includes the bronchi,
bronchioles and alveoli.
The respiratory system can also be
divided into a conducting zone and
a respiratory zone. The respiratory
zone is where gaseous exchange
takes place.

9. Components of the Gradian CCV SystemRespiratory Anatomy and Physiology
Basic Principles of Critical Care Training I Respiratory System Anatomy and Physiology
Upper Airway starts…
• Nose
• Pharynx
• Larynx
Lower Airway starts…
• Trachea
• Bronchi
• Bronchioles
• Alveoli

10. Components of the Gradian CCV SystemRespiratory Anatomy and Physiology
Basic Principles of Critical Care Training I Respiratory System Anatomy and Physiology
Upper Airway
• Nose
• Nasal cavity
• Nasal conchae
• Nasal vestibule
• Pharynx
• Nasopharynx
• Oropharynx
• Laryngopharynx
• Larynx
• Epiglottis
• Thyroid cartilage
• Cricoid cartilage
• Vocal folds

11. Components of the Gradian CCV SystemRespiratory Anatomy and Physiology
Basic Principles of Critical Care Training I Respiratory System Anatomy and Physiology
Lower Airway
• Trachea
• Carina of trachea
• Main Bronchi
• Bronchioles
• Alveoli
• Connective tissue
• Alveolar sacs
• Alveolar duct
• Alveoli
• Atrium
• Mucous gland
• Right lung
• Left Lung

12. Components of the Gradian CCV SystemRespiratory Anatomy and Physiology
Basic Principles of Critical Care Training I Respiratory System Anatomy and Physiology
Conducting Zone
Allows the air to flow inside the body
Respiratory Zone
Where gaseous exchange takes place

13. Components of the Gradian CCV SystemRespiratory Anatomy and Physiology
Basic Principles of Critical Care Training I Respiratory System Anatomy and Physiology
Conducting Zone
Includes the organs and structures that
are not directly involved in gas exchange
– from the mouth/nose to the level of the
terminal bronchioles. Functions include:
• Passage of air in and out of the
respiratory system
• Filtration of debris and pathogens
• Warming and humidification of air
These functions are bypassed when an endotracheal tube or tracheostomy is in
use in a patient and must be taken into consideration when a patient is intubated.

14. Components of the Gradian CCV SystemRespiratory Anatomy and Physiology
Basic Principles of Critical Care Training I Respiratory System Anatomy and Physiology
Respiratory Zone
Organs in respiratory zone are directly
involved in gaseous exchange. This
zone begins at the respiratory
bronchioles and extends to the
alveolar sacs.

15. Components of the Gradian CCV SystemRespiratory Anatomy and Physiology
Breathing
The process of inspiration and expiration is dependent on muscles, nerves and
chemicals.
Inspiration is initiated by the contraction of inspiratory muscles – the diaphragm
(the main muscle) and the external intercostal muscles.
By contacting the volume of the thoracic cavities increase resulting in a decrease
in the pressure within the lungs. This causes air to move from the atmosphere –
where the pressure is higher – into the lungs.
Basic Principles of Critical Care Training I Respiratory System Anatomy and Physiology

16. Components of the Gradian CCV SystemRespiratory Anatomy and Physiology
Breathing
During normal breathing, expiration is a passive process initiated by the
relaxation of the muscles of respiration and the air is forced out. Accessory
muscles of respiration may also be involved in breathing:
• Scalene
• Sternocleidomastoid
• Pectotalis (minor and major)
• Serratus anterior
• Latismus dorsi
Active expiration can occur when additional air needs to be expired above that
of normal breathing. This utilizes the anterolateral abdominal wall and the
internal intercostal muscles.
Basic Principles of Critical Care Training I Respiratory System Anatomy and Physiology

17. Components of the Gradian CCV SystemRespiratory System
Control of Breathing
Breathing is spontaneously initiated in the central nervous system by neurons in
the brainstem located in the respiratory center (medulla and pons).
The respiratory center has automaticity but can be modified by input from higher
centers (frontal cortex) and peripheral chemoreceptors. Inspiration is initiated by
firing from the respiratory center resulting in respiratory muscle contraction.
Exhalation results from a reduction of firing of the respiratory center.
Basic Principles of Critical Care Training I Respiratory System Anatomy and Physiology

18. Components of the Gradian CCV SystemRespiratory System
Gaseous Exchange
Gas exchange is the process by which oxygen and carbon dioxide move
between the bloodstream and the lungs.
Two important aspects of gas exchange in the lung are ventilation and
perfusion.
Basic Principles of Critical Care Training I Respiratory System Anatomy and Physiology
Gaseous exchange in alveoli by Domdomegg licenced under CC BY 4.0

19. Components of the Gradian CCV SystemRespiratory System
Ventilation
The movement of air into and out of the lungs
Perfusion
The flow of blood in the pulmonary capillaries.
Gas exchange occurs at two sites in the body:
• In the lungs  where oxygen is picked up and carbon dioxide is released at
the respiratory membrane,
• At the tissues  where oxygen is released, and carbon dioxide is picked up.
Basic Principles of Critical Care Training I Respiratory System Anatomy and Physiology

20. Components of the Gradian CCV SystemRespiratory System
Diffusion
The actual exchange of gases occurs due to simple diffusion. Gases diffuse from
areas of high pressure to areas of low pressure (concentration gradient).
Factors Affecting Diffusion
• Concentration gradient – the greater the gradient, the faster the rate of diffusion.
• Surface area – the greater the surface area, the greater the rate
• Distance/ length – the longer the length the slower the rate
Basic Principles of Critical Care Training I Respiratory System Anatomy and Physiology
Gaseous exchange in alveoli by Domdomegg licenced under CC BY 4.0

21. Components of the Gradian CCV SystemRespiratory System
Partial Pressure
Partial pressure is important in predicting the movement of gases. Changing the
atmospheric concentrations of either oxygen or carbon dioxide will affect their partial
pressures, and thus their absorption and elimination ratios.
• If oxygen levels are low, the partial pressure of oxygen will be low, and less
oxygen will diffuse into the lung tissues.
• If carbon dioxide levels are high, the partial pressure of carbon dioxide will be
high, causing less carbon dioxide to diffuse out of the lung tissues.
Basic Principles of Critical Care Training I Respiratory System Anatomy and Physiology
Gaseous exchange in alveoli by Domdomegg licenced under CC BY 4.0

22. Components of the Gradian CCV SystemRespiratory System
Transport of Gases
The absorbed oxygen is transported in blood bound to hemoglobin. Persons with
normal hemoglobin levels have hemoglobin saturation in the ranges of 95-99%.
Anemia, therefore, compromises the blood's oxygen carrying capacity.
Carbon dioxide is transported dissolved in the blood, in the form of bicarbonate
(HCO3–) and within the red blood cells
Basic Principles of Critical Care Training I Respiratory System Anatomy and Physiology
Gaseous exchange in alveoli by Domdomegg licenced under CC BY 4.0