The document outlines the principles, goals, and indications for mechanical ventilation, including methods of invasive and non-invasive ventilation. It details various ventilator settings, modes of operation, and complications associated with mechanical ventilation. Additionally, the document provides information on weaning criteria and procedures for patients requiring respiratory support.

1. Mechanical Ventilation
Dr. Abhijit Diwate
(Associate Professor)
Cardio-Vascular & Respiratory PT
DVVPF College of Physiotherapy,
Ahmednagar 414111

2. Objectives
Indications
Goals
Physiology of breathing
Principles of mechanical ventilation
 modes of ventilators
Settings of ventilators
Ventilator complications
Weaning criteria

3. Indications
Acute Respiratory Failure
Hypoxemia
Neuromuscular Disorders
Pulmonary edema
Over Sedation
reduce ICP
stabilize the chest wall
Aspiration
ARDS
Pulmonary embolism

4. Goals
Increase efficiency of breathing
Increase oxygenation
Improve ventilation/perfusion relationships
Decrease work of breathing

5. PHYSIOLOGY OF NORMAL BREATHING V/S
MECHANICAL VENTILATION
Normal breathing
1. Breathing by muscles is governed by
requirement of body.
2. Initiation and termination of breathing depend
on levels of PO2, PCO2, PH and lung inflation.
3. Air gets sucked in because of negative intra
pleural pressure created by the respiratory
muscles
4. Increase in pulmonary pressures are in the
range of 3to 5cms. Of water.
5. Venous return increases during respiration
6. Expiration is passive.

6. Mechanical ventilation
1 work of the respiratory muscles is done by
ventilator
2 Initiation, termination may be machine
determined (mandatory breath) or patient
determined (spontaneous breath).
3 Air is pushed in by positive pressure given
by the ventilator.
4 Pressures generated are in the range of 15
to 40cms of water
5 Venous return decreases during respiration
6 Expiration is passive

7. PRINCIPLES OF MECHANICAL
VENTILATION
A ventilator is a machine that generates the
pressure necessary to cause a flow of gas
that increases the volume of the lungs.
The three variables involved are
- Pressure
- Volume
- Flow
- One can be fixed or pre determined and the
other two will depend on the compliance of
the lungs and the chest wall and the
resistance offered by the airways.

8. Mechanical Ventilation
Non Invasive: Ventilatory support that is given
without establishing endo- tracheal intubation or
tracheostomy is called Non invasive mechanical
ventilation
Invasive: Ventilatory support that is given through
endo-tracheal intubation or tracheostomy is called
as Invasive mechanical ventilation
Non Invasive Invasive

9. NON INVASIVE
Negative
pressure
Producing Neg.
pressure intermittently
in the pleural space/
around the thoracic
cage
Positive pressure
Delivering air/gas with
positive pressure to
the airway

10. Invasive
Positive Pressure
Pressure cycle Volume cycle Time cycle

11. Positive Pressure Ventilators
Pressure Cycled
A pre determined and preset pressure terminates
inspiration. Pressure is constant and volume is
variable.
Small, portable, inexpensive
Ventilation volume can vary with changes in airway
resistance, pulmonary compliance
Used for short-term support of patients with no pre-
existing thoracic or pulmonary problems

12. Positive Pressure Ventilators
Volume cycled
Most widely used system
A pre determined and preset volume -on
completion of its delivery , terminates the
inspiration. Pressure is variable and volume is
constant
Delivers volume at whatever pressure is required
up to specified peak pressure
May produce dangerously high intrathoracic
pressures

13. Positive Pressure Ventilators
Time cycled
Delivers air/gas over a set time (Insp. Time) after
which the inspiration ends.
Volume determined by
Length of inspiratory time
Pressure limit set
Patient airway resistance
Patient lung compliance
Common in neonatal units

16. MODES
Synchronis
ed
intermittant
mandatory
ventilation
(SIMV)
CPAP Controlle
d (CMV)
Assist
control
ventilatio
n
(ACV)
Intermittent
Mandatory
Ventilation
(IMV)

17. Controlled Mechanical Ventilation
Patient does not participate in ventilations
Machine initiates inspiration, does work of breathing,
controls tidal volume and rate
Useful in apneic or heavily sedated patients
Useful when inspiratory effort contraindicated (flail chest)
Patient must be incapable of initiating breaths
Rarely used

18. Assist/Control (A/C)
Patient triggers machine to deliver breaths but machine
has preset backup rate
Patient initiates breath--machine delivers tidal volume
If patient does not breathe fast enough, machine takes
over at preset rate
Tachypneic patients may hyperventilate dangerously

19. Assist Mode
Intermittent Mandatory Ventilation (IMV)
Patient breathes on own
Machine delivers breaths at preset intervals
Patient determines tidal volume of spontaneous
breaths
Used to “wean” patients from ventilators
Patients with weak respiratory muscles may tire
from breathing against machine’s resistance

20. Assist Mode
Synchronized Intermittent Mandatory
Ventilation (SIMV)
Similar to IMV
Machine timed to delay ventilations until end of
spontaneous patient breaths
Avoids over-distension of lungs
Decreases barotrauma risk

21. Positive End Expiratory Pressure
(PEEP)
Positive pressure in airway throughout expiration
Holds alveoli open
Improves ventilation/perfusion match
Decreases FiO2 needed to correct hypoxemia
Useful in maintaining pulmonary function in non-
cardiogenic pulmonary edema, especially ARDS

22. Positive End Expiratory Pressure
(PEEP)
High intrathoracic pressures can cause decreased
venous return and decreased cardiac output
May produce pulmonary barotrauma
May worsen air-trapping in obstructive pulmonary
disease
DANGERS

23. Continuous Positive Airway Pressure
(CPAP)
PEEP without preset ventilator rate or volume
Physiologically similar to PEEP
May be applied with or without use of a
ventilator or artificial airway
Requires patient to be breathing spontaneously
Does not require a ventilator but can be performed
with some ventilators

24. Noninvasive pressure support
ventilation
Bi-level positive airway pressure ventilation
Set level of inspiratory positive airway pressure
and expiratory positive airway pressure
Flow triggered system
Applied through nasal mask
Tidal vol., flow rate, insp. Time vary with pt. effort,
set pressure and changes in compliance and
resistant

25. Pressure control
Pressure control with inverse inspiratory to
expiratory ratio ventilation

26. High Frequency Ventilation (HFV)
Small volumes, high rates
Allows gas exchange at low peak pressures

27. High Frequency Ventilation (HFV)
Useful in managing:
Tracheobronchial or bronchopleural fistulas
Severe obstructive airway disease
Patients who develop barotrauma or decreased
cardiac output with more conventional methods
Patients with head trauma who develop increased
ICP with conventional methods
Patients under general anesthesia in whom
ventilator movement would be undesirable

28. Ventilator Settings
Tidal volume--10 to 15ml/kg (std = 12 ml/kg)
Respiratory rate--initially 10 to 16/minute
FiO2--0.21 to 1.0 depending on disease process
100% causes oxygen toxicity and atelectasis in less than 24
hours
40% is safe indefinitely
PEEP can be added to stay below 40%
Goal is to achieve a PaO2 >60
I:E Ratio--1:2 is good starting point
Obstructive disease requires longer expirations
Restrictive disease requires longer inspirations

29. Ventilator Settings
Ancillary adjustments
Inspiratory flow time
Temperature adjustments
Humidity
Trigger sensitivity
Peak airway pressure limits
Sighs

30. Ventilator Complications
Mechanical malfunction
Keep all alarms activated at all times
If malfunction occurs, disconnect ventilator and
ventilate manually

31. Ventilator Complications
Airway malfunction
Suction patient as needed
Keep condensation build-up out of connecting tubes
Auscultate chest frequently
End tidal CO2 monitoring
Maintain desired end-tidal CO2
Assess tube placement

32. Ventilator Complications
Pulmonary barotrauma
Avoid high-pressure settings for high-risk patients
(COPD)
Monitor for pneumothorax
Anticipate need to decompress tension
pneumothorax

33. Ventilator Complications
Hemodynamic alterations
Decreased cardiac output, decreased venous return
Observe for:
Decreased BP
Restlessness, decreased LOC
Decreased urine output
Decreased peripheral pulses
Slow capillary refill
Pallor
Increasing Tachycardia

34. Ventilator Complications
Renal malfunction
Gastric hemorrhage
Pulmonary atelectasis
Infection
Oxygen toxicity
Loss of respiratory muscle tone

35. Weaning
Is the cause of respiratory failure gone
or getting better ?
Is the patient well oxygenated and
ventilated ?
Can the heart tolerate the increased
work of breathing ?

36. Weaning Criteria
Clinical assessment
Investigation
Mode and parameter change
CPAP
Venturi

37. Physiological parameters
Ventilatory pump
TV > 5ml/kg body wt.
RR </= 30
Driving force
Pressure inspiratory = -20 to -30 mm of Hg
Compliance <25 ml/ cm H2O
Breathing pattern – synchronous stable
WOB – near to normal
Oxygen status PaO2 > 60 mm of Hg
Carbondioxide PaCO2 < 50 mm Hg

38. WEANING PROCEDURE
T- tube trials
SIMV
Pressure support

39. Summary
Indications
Goals
Physiology of breathing
Principles of mechanical ventilation
 modes of ventilators
Settings of ventilators
Ventilator complications
Weaning criteria

40. QUESTIONS
1. WRITE THE INDICATIONS AND GOALS OF
MECHANICAL VENTILATION. 5MARKS
2. WRITE THE PRINCIPLES OF MECHANICAL
VENTILATIONS. 3 MERKS