Basic Principles of Critical Care

1. OXYGEN THERAPY
Gradian Health Systems
Basic Principles of Critical Care
RESPIRATORY SYSTEM

2. Disclaimer
Basic Principles of Critical Care Training I Oxygen Therapy
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 Oxygen Therapy

5. Components of the Gradian CCV SystemLesson 2: Oxygen Therapy
Lesson Objectives
• Differentiate between anoxia, hypoxia and hypoxemia
• Explain the major causes of hypoxia
• Describe the indications for oxygen therapy
• Distinguish the devices that are used in oxygen therapy
Basic Principles of Critical Care Training I Oxygen Therapy

6. Components of the Gradian CCV SystemLesson 2: Oxygen Therapy
Key Concepts
• Hypoxia
• Hypoxemia
• Oxygen therapy
Basic Principles of Critical Care Training I Oxygen Therapy

7. Oxygen Therapy
Hypoxia
• State in which there is insufficient oxygen at the tissue level
• Can result from:
• Inadequate oxygen reaching the tissues (oxygen delivery)
• Reduced amount of oxygen in the blood (hypoxemia)
Hypoxemia
• Low partial pressure of oxygen in the blood
Anoxia
• Total deprivation of oxygen supply
Basic Principles of Critical Care Training I Oxygen Therapy

8. Oxygen Therapy
Causes of hypoxia
Reduced oxygen tension
Occurs in areas of altitude
Hypoventilation
Can be due to reduced respiratory rate or depth of breathing (reduced tidal
volume). Common causes include sedation, coma (low GCS), airway obstruction,
neuromuscular disease, etc.
Ventilation
Perfusion mismatch – areas of the lungs are not being ventilated (collapse,
airway obstruction) or being adequately perfused (e.g. pulmonary embolism)
Basic Principles of Critical Care Training I Oxygen Therapy

9. Oxygen Therapy
Causes of hypoxia
Right to left shunt
Blood passing from the right side of the heart to the left without being
oxygenated. Examples include anatomical (VSD, ASD, PDA) or physiologic
(atelectasis, pneumonia, ARDS)
Impaired diffusion
Diffusion id dependent on the distance and the surface area. If the area is
decreased and the distance is increased, gaseous exchange in the alveolar will
be impaired (e.g. interstitial disease, fibrosis, edema).
Basic Principles of Critical Care Training I Oxygen Therapy

10. Oxygen Therapy
Presentation of hypoxia
Acute symptoms include:
• Tachycardia
• Tachypnea
• Sweating
• Hypotension
• Cyanosis
• Restlessness
• Dyspnea on exertion
A physical examination will point to the cause of hypoxia
Basic Principles of Critical Care Training I Oxygen Therapy

11. Oxygen Therapy
Evaluation of hypoxia
Hypoxia is indicated by:
• SpO2 ≤ 95%
• ABGA PaO2≤ 80mmHg
• PaO2:FIO2 ratio < 300 (normal 300-500)
PaO2:FIO2 ratio is important in defining ARDS
Basic Principles of Critical Care Training I Oxygen Therapy

12. Oxygen Therapy
Management of hypoxia
1. Maintaining a patent airway
• Suctioning
• Use of OPA (not tolerated in conscious patients) or NPS
• Head-tilt and jaw thrust (only jaw thrust if cervical spine injury
suspected)
• Positive pressure ventilation using CPAP or BiPAP can be used to
keep an open airway
• Bronchoconstriction can be relieved using bronchodilators
Basic Principles of Critical Care Training I Oxygen Therapy

13. Oxygen Therapy
Management of hypoxia
2. Increasing FiO2
• Can be achieved by using devices to deliver oxygen
Basic Principles of Critical Care Training I Oxygen Therapy

14. Oxygen Therapy
Oxygen Delivery Devices I Low Flow Devices
Nasal cannula
• Flow rate 1-6 L/min
• FiO2 24-45%
• Estimation of FiO2 (20% + (4 x O2 L/min))
• Advantages:
• Less claustrophobia
• Convenient for patient (can eat / talk)
• Disadvantages
• Dry mucous membrane if giving >4 L/min
• Limited value with mouth breathers
Basic Principles of Critical Care Training I Oxygen Therapy

15. Oxygen Therapy
Oxygen Delivery Devices I Low Flow Devices
Reservoir cannulas
• Nasal cannula with a reservoir providing 10 mls
• Reservoir can be pendant (on chest) or moustache
(around nostril) shaped
• Reservoir allows for increased FiO2 and flow rates
• Flow rate 1-16 L/min; FiO2 up to 90%
• Advantages
• Higher FiO2 compared to simple nasal cannula
• Disadvantages
• Will entrain air if patient flow rate is high
Basic Principles of Critical Care Training I Oxygen Therapy
Image source: https://thoracickey.com/medical-gas-therapy/

16. Oxygen Therapy
Oxygen Delivery Devices I Low Flow Devices
Simple face mask
• Flow rate 6-10 L/min
• FiO2 40-60%
• Advantages:
• Higher FiO2
• Disadvantages
• Not convenient for patient
• Claustrophobia
• Dry mucous membrane if giving >4 L/min
Basic Principles of Critical Care Training I Oxygen Therapy

17. Oxygen Therapy
Basic Principles of Critical Care Training I Oxygen Therapy
Oxygen Delivery Devices I Low Flow Devices
Face mask - partial rebreather
• No one-way inhalational valve
• Flow rate 10-12 L/min
• Bag must always be partially inflated
• FiO2 80-90%
• Advantages:
• Higher FiO2
• Disadvantages
• Expired air mixed with inhaled air
• Claustrophobia

18. Oxygen Therapy
Basic Principles of Critical Care Training I Oxygen Therapy
Oxygen Delivery Devices I Low Flow Devices
Face mask – non-rebreather
• One-way inhalational valve between mask and reservoir; allows for oxygen to
flow from tubing to reservoir and mask; one-way valve in exhalation ports
• Flow rate 10-15 L/min (bag must always be partially inflated to avoid
suffocation)
• FiO2 80-90%
• Advantages:
• Higher FiO2 (used if >40% is needed)
• Disadvantages
• Claustrophobia (must be well-fitted to get high FiO2)
• Humidification is difficult

19. Oxygen Therapy
Basic Principles of Critical Care Training I Oxygen Therapy
Oxygen Delivery Devices I Low Flow Devices
Face tent
• Flow rate minimum 15 L/min
• FiO2 28-100%
• Advantages:
• Higher FiO2
• Use in patient who can’t wear a mask (claustrophobia,
facial trauma, etc.)
• Disadvantages
• No seal – difficult to achieve high FiO2

20. Oxygen Therapy
Basic Principles of Critical Care Training I Oxygen Therapy
Oxygen Delivery Devices I Low Flow Devices
Oxygen tent / hood
• Covers patient’s head and/or upper body
• Flow rate minimum 8-10 L/min
• FiO2 25-70%
• Advantages:
• Patient not encumbered
• Can be humidified
• Disadvantages
• FiO2 may vary and not higher than other devices

21. Oxygen Therapy
Basic Principles of Critical Care Training I Oxygen Therapy
Oxygen Delivery Devices I High Flow Devices
Venturi mask
• Can be used on face mask, tracheostomy, t-piece, or face tent
• Entrains room air to achieve FiO2
• Flow rate minimum 4-12 L/min
• FiO2 24-60% using different sized and colored ports
• Advantages:
• More precise FiO2 despite respiratory rates and tidal volumes
• Useful in COPD and CO2 retention is a problem
• Humidification not required due to ambient patient air entrainment
• Disadvantages
• Claustrophobia
• Interferes with talking and eating

22. Oxygen Therapy
Basic Principles of Critical Care Training I Oxygen Therapy
Oxygen Delivery Devices I High Flow Devices
High flow nasal cannula (HFNC)
• Air / oxygen blender is used
• Flow rate minimum 10-60 L/min
• FiO2 up to 100% set on blender
• Advantages:
• Heated and humidified
• Provide PEEP (1 cmH2O for every 10L of flow)
• Reduces anatomical deep space
• Disadvantages
• May delay escalation to intubation for patients requiring intubation
Nishimura, Masaji. (2015). High-flow nasal cannula oxygen
therapy in adults. Journal of Intensive Care. 3. 10.1186/s40560-
015-0084-5.