Basic Orientation Of Mechanical Ventilation

1. BASICS OF
MECHANICAL
VENTILATION
Dr Rizwan
Ahmad
Medical
Officer-Cardiac
Surgery
Mayo Hospital

2. OBJECTIVES
Understanding of
• Basic Variables.
• Ventilator Graphs.
• Types of Ventilator Modes.
• Ventilation in Cardiac Surgery.
2

3. BASIC VARIABLES
o Resp rate
o Pressure
o Volume
o PEEP
o Flow
o Inspiratory time/ Inspiratory: Expiratory time

4. GRAPHS
Paw(mbar)
Flow(L/min)
Volume(ml)

5. GRAPHS
Pressure
Volume

6. TYPES OF BREATHS
A. Mandatory/Control
B. Assisted Breath
C. Spontaneous Breath

7. TYPES OF VENTILATOR
MODES

8. TYPES OF VENTILATOR
MODES
Pressure Control Volume Control

9. TYPES OF VENTILATOR
MODES
• CMV (PC/VC)
• AC (PC/VC)
• SIMV (PC/VC)
• SPN-CPAP/PS
• VC-MMV
• PC-BIPAP
• SPN-PPS
• PC-PSV
• PC-APRV

10. CONTINUOUS MANDATORY
VENTILATION
Features
• Clinician-set mandatory breath rate
• Mandatory breaths will be ventilator-triggered
Clinician-Set Parameters
• Mandatory breath rate
• Breath type
• VC
• PC
• Fractional inspired O2 concentration (FIO2)
• Positive end-expiratory pressure (PEEP)

11. CONTINUOUS MANDATORY
VENTILATION
VC-CMV PC-CMV

12. ASSIST CONTROL
Features
• Clinician-set mandatory breath rate
• Mandatory breaths may be patient-triggered or ventilator-triggered
• The patient may trigger any number of additional (spontaneous) breaths
• Mandatory and spontaneous breaths are identical
Clinician-Set Parameters
• Mandatory breath rate
• Breath type
• VC
• PC
• Fractional inspired O2 concentration (FIO2)
• Positive end-expiratory pressure (PEEP)

13. ASSIST CONTROL
VC-AC PC-AC

14. SYNCHRONIZED
INTERMITTENT MANDATORY
VENTILATION
Features
• Clinician-set mandatory breath rate
• Mandatory breaths may be patient-triggered or ventilator-triggered
• The patient may trigger any number of additional (spontaneous) breaths
• Mandatory and spontaneous breaths are always different
Clinician-Set Parameters
• Mandatory breath rate
• Mandatory breath type
• VC
• PC
• Spontaneous breath type
• PS
• FIO2
• PEEP

15. SYNCHRONIZED
INTERMITTENT MANDATORY
VENTILATION
VC-SIMV PC-SIMV

16. SPONTANEOUS-CONTINUOUS
POSITIVE AIRWAY PRESSURE
Features
• No mandatory breaths
• All breaths are spontaneous and patient-triggered
Clinician-Set Parameters
• Breath type
• PS
• FIO2
• PEEP

17. SPONTANEOUS-CONTINUOUS
POSITIVE AIRWAY PRESSURE

18. INITIAL VENTILATOR SETTINGS
FOR POST-OP PATIENTS IN
CARDIAC SURGERY
• FiO2: 70–100%, mode: SIMV.
• Tidal volume: 8–10mL/kg.
•Respiratory rate: 8–14 breaths/min.
•Minute volume: 100–120mL/kg/min.
•PEEP: 5–7.5cmH2O,
•Pressure support: 8–10 cmH2O.
•Inspiratory–expiratory ratio: 1:2,
•inspiratory flow rate: 30–60L/min.

19. CARDIAC SURGERY
• Any patient can be ventilated safely using SIMV.
• A tidal volume of 8–10mL/kg helps prevent atelectasis: but excessive tidal volumes
risk barotrauma, and can place a borderline LIMA graft under tension as it crosses
the upper lobe of the left lung to the LAD.
• A respiratory rate of 8–14 breaths per minute is adequate for most patients, but
patients with higher metabolic demands (shivering, sepsis) may benefit from higher
rates which help prevent respiratory acidosis.

20. CARDIAC SURGERY
•Increasing PEEP to 10cmH2O helps to reverse atelectasis improving oxygenation,
but can reduce venous return and MAPs in patients.
•Higher levels of PEEP are sometimes used in the hemodynamically stable, bleeding
patient to tamponade chest wall bleeding.
•The inspiratory–expiratory (I:E) ratio is 1:2., allowing optimal peak inspiratory
pressures and reducing the risk of air trapping: in selected patients that are diffi cult
to oxygenate the intensivist or anesthesiologist will change or even reverse these
ratios.

21. CARDIAC SURGERY
•Patients with COPD benefit from lower respiratory rates and higher tidal
volumes, allowing time for the longer expiratory phase, avoiding air trapping
(‘autoPEEP’) which can cause high intrathoracic pressures, barotrauma, and reduced
venous return causing hypotension.
•Peak inflation pressures in the adult are usually <30 cmH2O, and the usual
inspiratory fl ow rate is 30L/min, higher peak infl ation pressures occur in obesity,
active resistance from the patient, or a mechanical obstruction to airfl ow such as
bronchospasm, endobronchial intubation or mucus plugging with lobar collapse.

22. REFERENCES
 Chikwe, J., Cooke, D.T and Weiss, A. (2013) Oxford Specialist
Handbook of Cardiothoracic Surgery, 2nd edn., : Oxford University
Press.
 Kreit, J.W. (2017) Mechanical Ventilation: Physiology and Practice, 2nd
edn., : Oxford University Press.
 DRAGER () Instructions for use Evita V300, Available
at: https://www.draeger.com/Library/Content/evita-v300-ifu-9052995-
en.pdf
 icet-nepean () CHEAT SHEETS FOR
VENTILATION, Available at: https://www.icetnepean.org/uploads/5/8/5/
1/58510755/cheat_sheets_for_ventilation_5.pdf.

23. THANK YOU