1. Mechanical Ventilation 101
An Introduction to Ventilatory Support

2. OBJECTIVES The student will be able to:
State the two purposes of mechanical ventilation.
List three indications for mechanical ventilation.
State the primary reason for oxygenation failure.
List three complications of mechanical ventilation.
Differentiate between positive and negative pressure ventilation.
Differentiate between invasive and non-invasive ventilation.
Differentiate between pressure- and volume-based breaths.
Describe how the mode of ventilation is related to patient-ventilation interaction.
Differentiate between minute ventilation and alveolar ventilation.
Describe the relationship between alveolar ventilation and PaCO2.

3. OBJECTIVES State the two purposes of mechanical ventilation.
The student will be able to:
State the two purposes of mechanical ventilation.
List three indications for mechanical ventilation.
State the primary reason for oxygenation failure.
List three complications of mechanical ventilation.
Differentiate between positive and negative pressure ventilation.
Differentiate between invasive and non-invasive ventilation.
Differentiate between pressure- and volume-based breaths.
Describe how the mode of ventilation is related to patient-ventilation interaction.
Differentiate between minute ventilation and alveolar ventilation.

4. OBJECTIVES
The student will be able to:
Describe the relationship between alveolar ventilation and PaCO2.
State the two primary methods for controlling alveolar minute ventilation.
State the normal range for spontaneous tidal volume.
State the normal range for tidal volume during mechanical ventilation.
List the four primary causes of hypoxemia.
State two methods for improving PaO2.
Describe how PaCO2 is managed in patients with chronic airflow obstruction.
Describe how PaO2 is managed in patients with chronic airflow obstruction.

5. Purposes of Mechanical Ventilators
TWO FUNCTIONS:
Remove Carbon Dioxide
Deliver Oxygen
Ventilate (Decrease PaCO2)
WOB is excessive
Increased airway resistance
Reduced lung compliance
Defect with neuromuscular control
Post-operative support
Oxygenate (Increase PaO2 [SaO2])
Shunt

6. Effects of Positive Pressure Ventilation
Increased airway pressures
Reduction in venous return/cardiac output.
Reduced renal blood flow.
Cerebral blood flow issues.
Airway related issues

7. Ventilator Settings Positive vs. Negative Pressure
Invasive vs. Non-Invasive
Breath Type
What is our focus: Volume or Pressure
Mode
Who is in control: Patient or Ventilator
Is support full or partial?
A/C, SIMV, Spontaneous
Control of Alveolar Minute Ventilation

8. Alveolar Minute Ventilation.
PaCO2 levels are inversely related to VA
Increase minute volume, decrease PaCO2.
Decrease minute volume, increase PaCO2.
Minute Volume (VA) is (Tidal Volume minus Deadspace Volume) x respiratory rate.
(Vt – Vd) x f
Deadspace includes anatomic (doesn’t change), mechanical (stuff we add), and alveolar ( without ).
We can control alveolar minute ventilation by:
Changing Respiratory Rate (f)
Changing Tidal Volume .

9. Tidal Volume Spontaneous tidal volume is 5-8 mL/kg.
Set tidal volume on ventilator is patient dependent:
Higher tidal volumes may lead to higher delivery pressures and lung damage.
Use as small of a tidal volume as possible to reduce the PaCO2 to desired levels.
A setting of 7-10 mL/kg of Ideal Body Weight (IBW) is considered a safe place to start.
ARDS: 6-7 mL/kg
Some simulations “like” mL/kg
Evaluate CST to determine if setting is appropriate.

10. Oxygenation Issues Causes of Hypoxemia
Reduced barometric pressure (move)
Hypoventilation (ventilate)
V/Q imbalance (responds to increased FiO2)
Diffusion Defect (find cause and correct?)
Intrapulmonary Shunt
RECRUIT COLLAPSED ALVEOLI . .

11. Steps in Correcting PaO2
Increase FiO2
Increase Mean Airway Pressure
“Space under the table”
Increase starting pressure (PEEP)
Increase delivery (ending) pressure (PIP)
Lengthen inspiratory time (tI)

12. tI
PIP
PEEP

13. Mechanical Ventilation: COPD & Asthma
Treat increased PaCO2 (and low pH)
Use caution with increasing tidal volume.
Increased RV leads to overdistension.
Extend expiratory time.
Auto PEEP
Shorten inspiratory time (increase inspiratory flow rate).
Use respiratory rate to control PaCO2.
Control patient (?) pharmacologically.
Permissive hypercapnia and acidosis.
Treat reduced PaO2
Usually a result of hypoventilation and V/Q imbalance.
Responds well to increase in FiO2. . .

14. Determine Ventilator settings
5’10” male admitted to ICU.
Determine Ventilator settings
Mode
Tidal Volume
Respiratory Rate
FIO2
PEEP

15. ABG
pH: 7.31, PaCO2: 50, PaO2: 60, HCO3: 26

16. ABG:
pH: 7.38, PaCO2: 38, PaO2: 62, HCO3: 27