2. Objectives
Brief physiology on ventilation
Indications for mechanical ventilation
Modes of ventilation
Common waveforms including airway pressure monitoring
Complications of mechanical ventilation
3. Respiratory Physiology
What do the lungs do?
Oxygenation:
Ventilation:
: GAS EXCHANGE
: transfer of oxygen from air to blood
: transfer of CO2 from blood to alveoli then
out of body
4. What is normal breathing?
Negative pressure Positive pressure
or
Negative pressure
5. Spontaneous Respirations vs
Mechanical Ventilation
Spontaneous Respirations Mechanical Ventilation
Negative inspiratory force Positive inspiratory force
Air is pulled into the lung Air is pushed into the lung
INVASIVE NON INVASIVE
“IRON LUNG”
7. Indications for Mechanical Ventilation
Acute Hypoxic Respiratory Failure
Five causes of HYPOXIA
Acute Hypercarbic Respiratory Failure
Airway protection
GCS<8, Angioedema, Elective procedure
8. Goals with mechanical ventilation
Clinical objectives
Reverse hypoxemia
Reverse acute respiratory acidosis
Relieve respiratory distress
Prevent or reverse atelectasis
Reverse ventilatory muscle fatigue
Permit sedation and/or
neuromuscular blockade
Decrease systemic or myocardial
oxygen consumption
Stabilize the chest wall
Airway protection
Physiologic objectives
Support pulmonary gas exchange
based on alveolar ventilation and
arterial oxygenation
Reduce the metabolic cost of
breathing by unloading the
ventilatory muscles
Minimize ventilator-induced lung
injury
Uptodate
10. Modes of Ventilation
(most common)
Pressure cycled or Pressure controlled
The ventilator delivers a preset pressure and inspiration terminates
when that pressure is achieved
Pressure is set; Volumes are variable
Volume cycled or Volume controlled
The ventilator delivers a preset tidal volume and inspiration
terminates when that tidal volume is achieved
Volume and flow rate is set
11. Parameters
RR, Tidal volume, PEEP, FiO2, Inspiratory time, Trigger sensitivity
IDEAL BODY WEIGHT
Normal: 6-8ml/kg; lower 4-6ml/kg for ARDS
How do we know how much tidal volume to set?
16. Modes of Ventilation
Variable Volume Control Pressure Control
Volume • FIXED, Same every breath
• Time triggered but volume cycled
• Depends on pt effort and lung
compliance
• Time triggered and cycled
Pressure • Depends on lung compliance • FIXED, Same every breath
Rate • Minimum set, but pt can trigger
spontaneously
• Minimum set, but pt can trigger
spontaneously
Flow rate • FIXED, Same every breath • Depends on pt effort and lung
compliance
Waveforms • Pressure-time
• Pressure-volume loop
• Volume-time
• Flow-time
17. Troubleshoot for Hypoxia and
Hypercarbia
Oxygenation?
PEEP and Fio2
Ventilation?
RR and Tidal Volume
18. Resistance, Compliance, Elastance
Ohms Law: Voltage = Current X Resistance
Change in P= Flow X Resistance
R= Change in Pressure/Flow
Elastance= reciprocal of compliance ie stiffness
Compliance = Change in Volume/Pressure
19. Peak and Plateau Pressures
Peak Pressure (Ppeak or Total airway
pressure)= Resistance and Plateau pressure
Plateau pressure (Pplat): Pressure at the
alveoli/Compliance
Obtain inspiratory hold (zero flow)
Normal <30
Resistance= Ppeak - Pplat
20. Peak and Plateau Pressures
https://www.ebmedicine.net/topics.php?paction=sho
wTopicSeg&topic_id=378&seg_id=6521
22. Complications of Mechanical Ventilation
Cardiovascular and Renal Complications
Reduced venous return, cardiac output and hypotension
Decline in urine output
Gastrointestinal and Nutritional Complications
Gastritis and ulcer formation
Malnutrition
Neuromuscular and Psychological Complications
ICU acquired weakness, DVT and pressure ulcers
Sleep deprivation, sedation, delirium, depression
(Elliott, Aitken, Chaboyer, 2012, p. 405 and Chang 2014, p. 35-42).
23. Complications of Mechanical Ventilation
Ventilator Induced Lung Injury (VILI)
Ventilator Associated Pneumonia
Intrinsic positive end-expiratory pressure ( also called AutoPEEP) is the over
inflation of the lungs, which can be the result by large tidal volumes, not allowing a
long enough exhalation, or restrictive airways.
(Hess, MacIntyre, Mishoe et. al, 2011, p 465-467)
26. Summary
Mechanical ventilation is defined as the delivery of positive pressure
to the lungs which can be invasive vs non invasive
There are many modes of mechanical ventilation: keep it simple-
Volume and Pressure control
Understanding waveforms and airway pressure monitoring helps
with common ventilator troubleshooting
