5. Background.
• 1929 was one of the first
negative-pressure
ventilators widely used for
mechanical ventilation. This
metal cylinder completely
covered the patient up to
the neck.
5
6. • known as the iron lung, this
device used negative
pressure to cause a drop in
the intrapulmonary pressure
and to allow ambient airflow
into the patient's lungs.
6
7. • In the 1950s, the intensive
use of mechanical ventilation
started during the polio
epidemic in Scandinavia and
the United States. In
Copenhagen, Denmark.
7
8. • ventilating patients with
polio and respiratory
paralysis by manually forcing
50% oxygen through a
tracheostomy reduced the
mortality rate from 80% to
25%.
8
9. Definition :
Ventilators are: specially
designed pumps that can
support the ventilator
function of the
respiratory system.
9
10. They improve oxygenation
through application of high
oxygen content gas and
positive pressure.
10
12. Classifications.
• The signal to terminate the
machine's inspiratory activity
can be:
• (volume-cycled ventilator),
• (pressure-cycled ventilator),
• (time-cycled ventilator).
12
13. volume-cycled ventilator
• a preset volume
• is the most common form of
ventilator cycling used in
adult medicine
• because it provides a
consistent breath-to-breath
tidal volume.
13
14. Indications:
• Mechanical ventilation should
not be initiated without
thoughtful consideration
because intubation and
positive-pressure ventilation
could have potentially harmful
effects.
14
15. Indications:
• Many factors are considered
in the decision to institute
mechanical ventilation.
• Respiratory failure is the
primary indication
15
16. Indications:
• Apnea with respiratory arrest
• Acute lung injury
-R.R more than 30 BPM
-Minute ventilation>10 L/min
-PaO2, with supplemental (FIO2)
less than 55 mm Hg
16
17. • Chronic obstructive lung disease
- Blood gases - Persistent
hypoxemia, PCO2 (acutely) greater than
50 mm Hg with pH less than 7.25
_ Clinical deterioration
Respiratory muscle fatigue, coma,
hypotension, or tachypnea or bradypnea
17
18. • Neuromuscular disease
• Clinical judgment should be used ;
An increasing severity of the illness is
a sign that should alert the clinician
to consider instituting mechanical
ventilation.
18
19. Physiologic aspects.
• Most modern mechanical ventilators
function by providing warmed and
humidified gas to the airway
opening in conformance with various
specific volume, pressure, and time
patterns. The ventilator serves as
the energy source for inspiration,
19
20. • replacing the muscles of the
diaphragm and chest wall.
Expiration is passive, driven by
the recoil of the lungs and
chest wall
20
21. Ventilator mode:
• This setting specifies the
manner in which ventilator
breaths are triggered,
cycled, and limited .
21
22. • Assist Control Mode Ventilation
(ACMV)
An inspiratory cycle is initiated
either by the patient's inspiratory
effort or, if no patient effort is
detected within a specified time
window,
22
23. • Every breath delivered consists of
the operator-specified tidal
volume.
• ACMV is the recommended mode for
initiation of mechanical ventilation
because it ensures a backup minute
ventilation in the absence of an intact
respiratory drive.
23
24. • ACMV is not effective for
weaning patients from
mechanical ventilation because
it provides full ventilator
assistance on each patient-
initiated breath.
24
25. • Synchronized Intermittent
Mandatory Ventilation
(SIMV)
The major difference between SIMV
and ACMV is that in the former
the patient is allowed to breathe
spontaneously, i.e., without
ventilator assist
25
26. • If the patient fails to initiate
a breath, the ventilator
delivers a fixed-tidal-volume
breath and resets the internal
timer for the next inspiratory
cycle.
26
27. • SIMV is a useful mode of
ventilation for both supporting and
weaning intubated patients
• SIMV may be difficult to use in
patients with tachypnea because
they may attempt to exhale during
the ventilator-programmed
inspiratory cycle.
27
28. • Continuous Positive Airway Pressure
(CPAP)
.This is not a true support-mode of
ventilation, since all ventilation
occurs through the patient's
spontaneous efforts.
28
29. • CPAP is used to assess extubation
potential in patients who have been
effectively weaned and are
requiring little ventilator support
29
30. • Pressure-Control Ventilation
(PCV)
This form of ventilation is time triggered,
time cycled, and pressure limited. During
the inspiratory phase, a given pressure
is imposed at the airway opening, and
the pressure remains at this user-
specified level throughout inspiration
30
31. • PCV is the preferred mode of
ventilation for patients with
documented barotrauma, since
airway pressures can be
limited,
•
31
32. • Pressure-Support Ventilation
(PSV)
This form of ventilation is patient
triggered, flow cycled, and
pressure limited; it is specifically
designed for use in the weaning
process.
32
33. PSV is well tolerated by most
patients who are being weaned:
PSV parameters can be set in such
a way as to provide full or nearly
full ventilatory support and can be
withdrawn slowly over a period of
days in a systematic fashion to
gradually load the respiratory
muscles.
33
34. COMPLICATIONS:
• Endotracheal intubation and positive-
pressure mechanical ventilation have
direct and indirect effects on several
organ systems
• Including:
-the lung and upper airways, the
cardiovascular system, and the gastrointestinal
system.
34
35. • barotrauma, nosocomial pneumonia,
oxygen toxicity, tracheal stenosis,
and deconditioning of respiratory
muscles.
• emphysema, pneumomediastinum,
subcutaneous emphysema, or
pneumothorax.
35
36. • Patients intubated for longer than 72 h
are at high risk for nosocomial
pneumonia as a result of aspiration from
the upper airways via small leaks around
the endotracheal tube cuff
• enteric gram-negative rods,
Staphylococcus aureus, and anaerobic
bacteria.
36
37. • Oxygen toxicity is a potential
complication when an FIO2 of 0.6 or
greater is required for more than 72 h.
• Hypotension resulting from
elevated intrathoracic pressures
with decreased venous return
37
38. • Gastrointestinal effects of
positive-pressure ventilation include
stress ulceration and mild to
moderate cholestasis. It is common
practice to provide prophylaxis with
H2-receptor antagonists or
sucralfate for stress-related
ulcers.
38
39. Weaning.
• Many approaches to weaning patients
from ventilator support have been
advocated.
• T-piece and CPAP weaning are best
tolerated by patients who have
undergone mechanical ventilation for
brief periods
39
40. Weaning.
• SIMV and PSV are best for
patients who have been intubated
for extended periods and require
gradual respiratory-muscle
reconditioning.
40
