Principles of Mech Vent

Respiratory Review and the Principles of Mechanical Ventilation Videos

Complex areas of clinical practice, such as developing an understanding of Mechanical Ventilation are challenging to grasp for those new to critical care. Be you a Doctor, a Nurse, or a Respiratory Therapist, skill, knowledge, and mastery of Mechanical Ventilation are developed and acquired over time. We grasp the principles, revisit theory in clinical practice and develop tacit experience, all on our own learning trajectory. I know I have often had to revisit the foundation principles of Mechanical Ventilation throughout my career, re-integrating the core theory and have often found I’ve been left to leaf through textbooks and search broadly for unfiltered content online.

Enter Oli Poole @RespReview, Respiratory Therapist practicing in Canada and provider of some of the best FOAMed, FOANed and FOAMcc content around on mechanical ventilation and associated clinical topics. If you like what you see below, please go and visit the Respiratory Review YouTube Channel https://www.youtube.com/channel/UCtaRF58UDVthvH36YYCttng This channel is a repository to an expanding library of top notch, Khan Academy style videos on Ventilation and related topics.

On this Injectable Orange page, with Oli’s permission, I am providing a second home/portal and a mini curriculum of sorts, around the foundational content. These videos run sequentially alongside the common induction knowledge pathways for those new to Intensive Care, and Critical Care in the ED or Respiratory Wards.

Principles of Mechanical Ventilation 1: Goals and Indications for MV

Content: This video provides an introduction into the goals of mechanical ventilation, as well as categorising the indications for mechanical ventilation into 3 major categories.

Learning Outcomes: At the end of this video the learner should be able to:
1) Describe the goals of mechanical ventilation
2) Understand the major indications for mechanical ventilation
3) Describe the primary ABG disturbance for Type I and Type II respiratory failure

Principles of Mechanical Ventilation 2: Phases of a breath

Content: This video briefly outlines the 4 major phases of a mechanically ventilated breath:

1. Start of Inspiration;
2. Inspiration;
3. End-Inspiration;
4. Baseline.

Learning Outcomes: At the end of this video learners should be able to demonstrate knowledge of the 4 phases of a mechanically ventilated breath.

Principles of Mechanical Ventilation 3: Total Cycle Time and I:E ratio

Content: This video builds upon the video on phases of a breath, introducing the topics of total cycle time, and I:E ratio.
Learning Outcomes: By the end of this video learners should be able to:
1) Define Total Cycle Time and I:E ratio.
2) Calculate the I:E ratio using varying respiratory rates and inspiratory times.

Principlies of Mechanical Ventilation 4: Modes – Assist Control (AC)

Content: This video introduces the topic of modes of ventilation. Identifying the different breath types that can be delivered by a ventilator the video explores the ‘Assist/Control’ mode.

Learning Outcomes: After watching this video the learner should be able to:
1) Identify the 3 types of ventilator breath
2) Differentiate between a control breath and an assisted breath
3) Explain what happens when the patient triggers an additional breath in an assist control mode.

Principle of Mechanical Ventilation 5: Assist Control Volume Control

Content: This video specifically explores the features of Volume targeted breath delivery, including ventilator waveforms in Assist Control Mode.

Principles of Mechanical Ventilation 6: Phase variables

Content: A video on the 3 key phase variables: Trigger Variable, Limit Variable, and Cycle Variable.

Principles of Mechanical Ventilation 7: Calculating I:E ratio in Volume Control (VC)

Content: This video demonstrates how to calculate IE ratio, Ti, Te, and TCT in volume control.
It should be noted that some modern Ventilators allow Ti to be selected in “Volume Control”. Such modes are not truly volume control, but Pressure Regulated Volume Control (PRVC), or a version of it. We will cover PRVC in later videos.

Principles of Mechanical Ventilation 8: I:E ratio example 2 in VC constant flow

Content: This video builds, with another case upon Video 7. Second example of how to calculate I:E ratio in volume control with constant flow.

Principles of Mechanical Ventilation 9: Pressure Volume relationship in VC

Content: A video on the relationship between pressure and volume in volume control ventilation. A really important concept!
Key points:
1) Pressure is variable in volume control, the pressure generated will depend on the lung mechanics of the patient, the size of the breathing tube etc.. think of anything that changes COMPLIANCE or RESISTANCE
2) A high pressure alarm can be set to cycle high pressure breaths, this protects the lungs from the deleterious effects of high pressures
Compliance is key! Watch the video on compliance, up next.

Principles of Mechanical Ventilation 10: Compliance

Content: A video on lung compliance. Hopefully this will give you a good intuitive idea of what compliance is, and how it relates to mechanical ventilation.

Principles of Mechanical Ventilation 11: Modes – Pressure control

Content: This videos aims to provide and intuitive look at pressure control. This is simple an introduction to the pressure controlled breath delivery. We will be delving much deeper into the details later on.

Related homework: Inspiratory Time in Pressure Control: How to use the Flow Waveform! https://www.youtube.com/watch?v=8WzOqLg2j3E

Principles of Mechanical Ventilation 12: Inspiratory Time in Pressure Control: How to Use the Flow Waveform!

Content: This video looks into how we can adjust our inspiratory time in pressure control based on the flow waveform. Using the pattern of flow decay (specifically the flow at end inspiration) to guide our decision on Ti setting. In some situations, we can actually gain some tidal volume without having to increase the PC level simply by adjusting the inspired time. In other settings we may wish to “crop” of inspiratory time if the flow has decayed to zero before the end of the inspiratory time. 

Principles of Mechanical Ventilation 13: Pressure Support Ventilation

Content: This video details the principles of spontaneous mode pressure support ventilation. An excellent resource to teach sensing/triggering and cycling in spontaneous mechanical ventilation.

Principles of Mechanical Ventilation 14: SIMV

Content: In this video Oli discusses the principles of Synchronised Intermittent Mandatory Ventilation. He refers to a number of references:

SIMV increases weaning failure versus PSV:
Ref: Brochard L, Rauss A, Benito S, et al: Comparison of three methods of gradual withdrawel from mechanical ventilation. Am J Respir Crit Care Med 1994; 150:896-903

SIMV slower at weaning than PSV or T-piece:
Ref: Esteban A, Frutos F, Tobin MJ, et al: A comparison of four methods of weaning patients from mechanical ventilation: Spanish Lung Failure Collaborative Group. N Eng J med 1995; 332:345-350

Reference for the video in general:
Papadakos and Lachman. Mechanical Ventilation: Clinical Applications and Pathophysiology. 1st ed. Elsevier. Chapter 22: Basic Modes of Mechanical Ventilation.

I hope this serves as a gateway to Oli’s brilliant work. Please check out his other videos covering physiology topics related to ventilation. Oli has a talent for distilling the complex, into simplicity.

Hat Tip: I was first directed to Respiratory Review via the Critical Care Practitioner Podcast. Check out Jonathan Downham’s two interviews with Oli:

http://www.jonathandownham.com/ccp-podcast-018-mechanical-ventilation/

http://www.jonathandownham.com/ccp-podcast-024-mechanical-ventilation-basics/