1. Mechanical Ventilation: The Basics and Beyond
Presented By:
Diana Gedamke, BSN, RN, CCRN
Marion College - Fond du Lac
Masters of Nursing Student

2. Module 3
Ventilator Wave Forms

3. Positive Pressure Ventilation
Two Main Types of Ventilators with Positive Pressure
Volume-cycled ventilation – With a set volume of air delivered per breath; Pressure to deliver breath will vary
Pressure-preset ventilation – With a set volume of pressure to open airways; Volume delivered will vary

4. Volume-cycled Ventilation
Delivers a preset volume of gas with each machine breath—airway pressures increase in response to the delivered breath
Airway pressures are higher in patients with low compliance or high resistance—high pressures indicate risk of ventilator-induced lung injury

5. Spontaneous Breathing vs. Positive Pressure Ventilation

6. Volume-cycled Ventilation
Assist Control (AC)
Synchronized Intermittent Mandatory Ventilation (SIMV)

7. Assist-control (AC) Most widely used mode of MV
Delivers a minimum number of fixed- volume breaths
Patients can initiate extra assisted breaths (will get full set volume with each effort)

8. Pressure-time Tracings Assist Control Mode

9. Synchronized Intermittent Mandatory Ventilation (SIMV)
Delivers preset number of fixed-volume breaths
Patient can breathe spontaneously between breaths (rate and depth determined by patient)
Patients often have trouble adapting to intermittent nature of ventilatory assistance

10. Pressure-time Tracings SIMV Mode

11. Pressure-preset Ventilation
Delivers a predefined target pressure to the airway during inspiration
Resulting tidal volume (VT) and inspiratory flow profile vary with the impedance of the respiratory system and the strength of the patient’s inspiratory efforts
Includes pressure-control (PC) and Pressure support (PS)

12. Pressure-control (PC) Ventilation
Delivers a preset gas pressure to the airway for a set time and at a guaranteed minimum rate
Patient can breathe in excess of set rate
Tidal volume achieved depends on pressure level, lung mechanics, and patient effort
Inspiratory flow rate variable

13. Pressure Support (PS) Delivers preset airway pressure for each breath
Variable parameters: Inspiratory and expiratory times (respiratory rate), flow rate, and tidal volume (VT)

14. Synchronized Intermittent Mandatory Ventilation (SIMV) + Pressure Support (PS)
A set number of Mandatory breaths are delivered per minute.
Remainder of patients breath are at his own rate and volume
Spontaneous breaths allowed in SIMV are assisted by PS

15. New Modes of MV New modes often introduced
Involves nothing more than a modification of the manner in which positive pressure is delivered to the airway and of the interplay between mechanical assistance and patient’s respiratory effort
Goals: enhance respiratory muscle rest, prevent deconditioning, improve gas exchange, prevent lung damage, improve synchrony, foster lung healing

16. Ventilator Settings Respiratory rate Tidal volume FiO2
Inspiratory:Expiratory (I:E) ratio
Pressure limit
Flow rate
Sensitivity/trigger
Flow waveform

17. Inspiratory Flow (V) Waveform
Square waveform Decelerating Waveform
(constant flow) (decelerating flow)

18. Inspiratory Flow (V) Waveform
Square waveform: volume of gas is evenly distributed across inspiratory time. Has highest peak pressure and lowest mean airway pressure. Ideal for those at risk for autopeeping due to short inspiration time

19. Inspiratory Flow (V) Waveform
Decelerating waveform: Volume of gas flow is high at the beginning of inspiration then tapers off toward the end of the breath. Has lowest peak pressure and highest mean airway pressure. Increased inspiratory time; useful in ARDS.

20. Patient-Ventilator Synchrony
Check for:
Symmetric chest inflation
Regular breathing pattern
Respiratory rate < 30 bpm
Synchrony between patient effort and machine breath
Paradoxical breathing

21. Patient-Ventilator Synchrony
Inspiratory effort expended by patients with acute respiratory failure is x normal
Don’t eliminate respiratory effort: causes deconditioning and atrophy

22. Patient-Ventilator Asynchrony
Possible causes:
Anxiety or pain
Ventilator settings may not be appropriate: check ABG and alert individual responsible for ventilator orders
Auto-PEEP
Pneumothorax

23. Ventilator Alarms and Common Causes
High Pressure
Low Pressure
Low Exhaled Volume
Kink in tubing
Patient biting ETT
Ventilator disconnected from ETT
Pressures exceeding high pressure limit
Secretions
Cuff leak
Coughing
Extubation
Ventilator disconnected
Bronchospasm
Foreign body

24. Definitions
PEEP – positive-end-expiratory pressure applied during mechanical ventilation
CPAP - continuous positive airway pressure applied during spontaneous breathing

25. PEEP
Improves oxygenation - increases functional residual capacity (FRC) above closing volume to prevent alveolar collapse
permits reduction in FIO2
Reduces work of breathing
Increases intrathoracic pressure - decreases venous return to right heart - decreases CO
Titrate to least amt. necessary to achieve O2 sat > 90% or PO2 > 60 mm Hg with FiO2 < 0.6

26. Auto-PEEP
Auto-PEEP/intrinsic PEEP (PEEPi)/inadvertent PEEP/occult PEEP - positive end expiratory alveolar pressure occurring in the absence of set PEEP. Occurs when expiratory time is inadequate.

27. Assessing Flow Waveform for Presence of Auto-PEEP

28. Resistance and Compliance

29. Definitions Peak Airway Pressure (Ppk)
An increase in Ppk indicates either an increase in airway resistance or a decrease in compliance (or both).
Plateau Pressure (Ppl) - end- inspiratory alveolar pressure

30. Airway Pressure Analysis

31. Ventilator-Induced Lung Injury
High volumes and pressures can injure the lung, causing increased permeability pulmonary edema in the uninjured lung and enhanced edema in the injured lung
Alveolar overdistention + repeated collapse and re-opening of alveoli

32. Mechanical Ventilation in Obstructive Lung Disease
resistance to expired flow
results in air trapping/hyperinflation
hyperinflation may result in cardiopulmonary compromise
Goal: meet minimal requirements for gas exchange while minimizing hyperinflation
Allow increased time for expiratory flow

33. Increasing Time for Exhalation
Decrease inspiratory time
Increase flow rate
Square waveform
Decrease minute ventilation (VE)
RR x TV

34. Monitoring Patients with Obstructive Lung Disease Requiring Mechanical Ventilation
Monitor plateau pressure: in general, Pplat < 30 cm H20 to decrease risk of hyperinflation and alveolar overdistension
Permissive hypercapnia

35. Respiratory Failure Due to Asthma
Watch for overventilation post intubation
High Ppk common
May require sedation to establish synchronous breathing with ventilator
Avoid paralytics
Ventilate as stated above (Increase exhalation time by decreasing RR and TV, increasing inspiratory flow rate, and using square waveform)
May want to use SIMV

36. Respiratory Failure Due to COPD
Ppk typically not as elevated as in asthma; when it is, think other pathologic processes
Many patients with COPD have chronic hypercapnia; ventilatory support titrated to normalize pH and not PCO2
Small levels of set PEEP may decrease WOB
May try NIPPV

37. Noninvasive Positive Pressure Ventilation (NIPPV)
Cooperative patient
Functionally intact upper airway
Minimal amount of secretions
Done by full face or nasal mask
Watch for gastric distension; may increase risk of aspiration
May use standard ventilators
Monitor patients closely for decompensation and need for intubation

38. ARDS: A Three Lung Unit Model
Normal
Non-recruitable
Recruitable

39. Respiratory Failure Due to ARDS
Refractory hypoxemia
Avoid ventilator induced lung injury
pressure-limited approach
keep Pplat < 30 cm H20
small tidal volumes (6 ml/kg)
permissive hypercapnia
Avoid O2 toxicity; apply moderate levels of PEEP

40. ARDS May need to increase inspiratory time
Inverse ratio ventilation (IRV)
I:E > 1:1
May require sedation/paralysis
Use as second-line strategy if PEEP fails to improve oxygenation

41. Mechanical Ventilation in Patients with Neuromuscular Weakness
Present with acute or subacute respiratory failure, usually with hypercapnia
progressive neurologic dysfunction (amyotrophic lateral sclerosis, muscular dystrophies, Guillain-Barre, CNS dysfunction due to head injury or drug ingestion)
usually ventilated without difficulty unless RF is complicated by secondary conditions (atelectasis or pneumonia)
lung compliance and gas exchange remain relatively normal