seminar on mechanical ventilation and respiratory failure

1. Introduction to mechanical
ventilation and respiratory failure
Presenter: Dr Getaye S. ACCPR2
9/8/2022 1

2. Outlines
Introduction
Type and working principle of MV
Modes of ventilation and initial ventilator setting
Common alarm settings and MV Troubleshooting
Respiratory failure
References
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3. Objectives
Understanding basic principles of mechanical
ventilations.
Know types RF, their cause and management
principles
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4. Introduction
Mechanical ventilation
Used to replace fully or partially the functions of
spontaneous breathing by performing the WB and
gase exchange
Apart from its supportive role in OR, MV support
is indicated when spontaneous ventilation is
inadequate for the sustenance of life
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5. Cont,
History of MV
Galen’s observations on the respiratory and
circulatory systems in the 2nd century
The Drinker Respirator,
“iron lung” was offered by John Emerson in 1932.
In the 1940s and 1950s, polio epidemics
Copenhagen in 1952, when Bjorn Ibsen…positive
pressure ventilation
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7. Cont,
As a result two basic methods have been
developed to replace the normal mechanisms
of breathing:
Negative pressure ventilation
Positive pressure ventilation
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9. Cont,
Positive Pressure Ventilation
PPV occurs when a MV is used to deliver air into
the patient’s lungs by way of an endotracheal tube
or positive pressure mask.
During inspiration the pressure in the alveoli
progressively builds and becomes more positive.
At the end of inspiration, the ventilator stops
delivering PPV mouth pressure returns to ambient
pressure.
And the direction of airflow changes then
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10. 9/8/2022
3.monitor
2. Main mechanical
ventilator part
Inspiratory and
expiratory port
1. Power
source and
medical gases
supply
4. Corrugated
tube, Y-piece
with patient
interface
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11. Cont,
Power Source Or Input
Power
 an electrical or
 pneumatic (compressed
gas) source.
 Pneumatic Circuit:
 is a series of tubes that
allow gas to flow inside the
ventilator and between the
ventilator and the patient.
 Divided as internal and
external pneumatic circuits
Control Systems And
Circuits:
 Can be open closed loop
system
 Closed-loop systems
The control panel, or user
interface,
 is located on the surface of
the ventilator
 It is monitored and set by
the ventilator operator.
Adjuncts?
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12. Cont,
Pressures In PPV:
Baseline Pressure:
Airway pressures are measured relative to a baseline
value.
The baseline pressure is zero (or atmospheric).(ZEEP)
The baseline pressure is higher than zero when non
zero value is set(PEEP)
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13. Cont,
Positive end expiratory pressure
PEEP increases the volume of gas remaining in the
lungs
At the end of a normal exhalation PEEP increases the
FRC.
PEEP applied by the operator is referred to as extrinsic
PEEP.
Auto-PEEP (or intrinsic PEEP), is air that is accidentally
trapped in the lung.
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14. Cont,
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15. Cont,
Peak Pressure:
This is the highest pressure recorded at the end of
inspiration.
PinP is also called peak inspiratory pressure (PIP) or
peak airway pressure.
These pressures measured during inspiration are the
sum of:
a) the pressure required to force the gas through the
resistance of the airways (PTA)
b) and the pressure of the gas volume as it fills the alveoli
(Palv).
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16. To assist a breath, the ventilator drops the pressure below baseline by 1cm H2O. The
assist effort is set at +9cm H2O.
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17. Cont’d
Plateau Pressure :
The plateau pressure is measured after a breath
has been delivered to the patient and before
exhalation begins.
Exhalation is prevented by the ventilator for a
brief moment (0.5 to 1.5 s).
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21. Modes of mechanical ventilations
Each ventilator-controlled respiratory cycle
can be divided into four phases
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22. Cont,
Variables
Variables are elements of a breath that a ventilator
can control during breath delivery.
There are two kinds of variables, control variables and
phase variables.
Control(targeted) Variables
Only one of the three control variables – volume, pressure,
or flow – can be used to control the shape of a breath.
Accordingly the MV mode become volume, pressure, or
flow controlled
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23. Cont,
Phase Variables
How the ventilator controls the phases of the
respiratory cycle .
Can be trigger variable, cycle variable, and
baseline variable.
The Triggerring Variable
Triggering is the mechanism that the ventilator uses to
cycle from expiration to inspiration.
A ventilator-driven breath
 patient initiated (patient-triggered).
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24. Cont,
Cycle Variable
The changeover from inspiration to expiration and
from expiration to inspiration is called cycling.
different ways to cycle between inspiration and
expiration
• time, volume or flow cycled
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25. Cont,
Baseline Variable
 This is the variable that is controlled at end
exhalation.
Most often, the baseline variable controlled is
pressure.
The end expiratory pressure may be set to zero
(ZEEP), or may be non zero PEEP
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26. Cont,
Waveforms
 are graphical representation of data collected by the
ventilator.
 Waveform analysis can help in determining & early pick
ventilation problems
 Two types of waveforms
a) Scalars - variables plotted against time.
Pressure Vs time
Flow Vs time
Volume vs time.
b) Loops - two variables plotted against each other.
Pressure-volume loop,
Flow-volume loop
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27. Cont,
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28. Cont,
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29. Control Variable - Either Pressure or Volume targeted
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30. Cont,
 Mode is the method of
inspiratory support
 Common Conventional
modes: CMV, AC,
IMV/SIMV
 Others: PSV, CPAP/BPAP,
APRV
 New modes: HFV,
adaptive modes, NAVA,
IRV
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32. Cont,
Controlled mechanical
ventilation(CMV)
 Does not need any patient
effort
 Paralysed, heavily sedated
and comatose pts are
candidates
 Can be either pressure or
volume targeted
 Most Modern Mechanical
ventilators have no this
mode, Why?
Asisst control (AC) mode:
 Has risk of hyperventilation
and VILI when the patient
has breathing effort
 Can be volume or pressure
controlled
 Better option for critically
ill patients who requires
constant VT or full support
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33. Cont,
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34. Cont,
 Synchronized intermittent
mandatory ventilation
(SIMV)
 Variation of IMV in which the
ventilators breath is
synchronized with the
patients inspiratory effort
 The support ranges from zero
to full supports and is
important for weaning from
MV
 was introduced to avoid the
problems associated with
IMV.
 Advantages over AC modes?
 Intermittent mandatory
ventilation (IMV)
 the spontaneous breath is not
machine supported and
mandatory breathes are not
synchronized with patient
effort
 Has risk of of asynchrony,
breath stacking and increased
work of breathing
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35. Pressure-Regulated
Volume Control(PRVC)
is designed to deliver a
volume-targeted, pressure-
control breath.
the ventilator automatically
adjusts pressure between
breaths to reach the targeted
volume in response to varying
patient conditions.
The pressure-control value is
then gradually increased or
decreased until the target tidal
volume .
Advantages?
dual Modes and
Adaptive Control
 best characteristics of
both pressure-and volume-
control ventilation.
When using a single
variable as the control, with
pressure control, volume
varied and with volume
control, pressure varied.
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36. Cont,
High-Frequency Ventilation
 have been in use since the 1960s.
High-frequency ventilation employs very low VT,
less than physiologic VD (about 3rd of VT) and very
rapid RR (> 60 breaths/min).
Used for:
 patients in the face of large air leaks with major airway
disruption
rescue technique in adult ARDS
in infants with RF unresponsive to conventional MV
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37. Cont,
There are four major types of HFV that differ
based on breath delivery design.
High-frequency positive pressure ventilation
(HFPPV)
High-frequency jet ventilation (HFJV)
High-frequency oscillatory ventilation (HFOV)
High-frequency percussive ventilation (HFPV)
 Neurally adjusted ventilatory assist (NAVA)
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38. Cont,
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39. Cont,
Spontaneous Modes
There are three basic means of providing support
for continuous spontaneous breathing (CSV)
during MV:
Spontaneous breathing
Continuous positive airway pressure (CPAP)
Pressure support ventilation (PSV)
APRV
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40. cont,
PSV
is a special form of assisted ventilation.
provides a constant pressure during inspiration
once it senses that the patient has made an
inspiratory effort
the patient must have a consistent, reliable
spontaneous respiratory pattern
The operator sets the inspiratory pressure, PEEP,
flow cycle criteria, and the sensitivity level.
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41. Cont,
CPAP
Ventilators can also provide CPAP for spontaneously
breathing patients.
In the acute care setting, CPAP may be helpful for
improving oxygenation in Pts with refractory hypoxemia .
The ventilator can provide a means of monitoring the
patient.
 BPAP
also called bilevel pressure assist, often used in NIV. .
The operator sets two pressure levels:
 Inspiratory positive airway pressure
Expiratory positive airway pressure
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42. Cont,
The Indications for Mechanical Ventilation
Hypoxic RF
Hypoventilation(hypercarbic RF)
Increased Work of Breathing
Airway protections
Other Indications
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43. Initial ventilator settings
Regardless of the method used for selecting the
VT ,be aware of risks below:
a) Overdistention of lung tissue
b) Repeated opening and closing
c) Inadequate VT setting
modes of ventilation are frequently chosen based
on:
 the lung pathology & hemodynamics,
oxygenation,
lung mechanics,
clinician familiarity
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44. Initial ventilator settings
The MV monitor screen
contains mainly 3 data
types:
 The set data value, alarm
settings and patient data
What we set on MV:
 VT/Pinsp, RR
 PEEP, FIO2
 I:E ratio, Flow rate
 Trigger sensitivity
 Flow triggers
 Alarm setting
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45. Cont,
PCV
 Lower PAP?
 Homogenous gas
distributions
 Improved pt-vent
synchrony
 Earlier liberation from
MV
VCV
 Can guarantee constant
VT
 Good forlung protective
ventilation protocol
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46. Specific considerations
COPD and asthma an initial VT of 6 to 8 mL/kg
with a rate of 8 to 12 breaths/min
chronic or acute restrictive disease, such as
pulmonary fibrosis or ARDS, an initial VT of 4
to 6 mL/kg +rate 15 to 25bpm
The VT should be adjusted to maintain Ppl <30
cm H2O and RR adjusted to minimize auto-
PEEP
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47. Cont,
 ARDS pts…VC/PC?
COPD/asthma…VC/PC?
 intracranial pathology?
Significant air leak?
For those with bariatric surgery?
o No statistically significant difference in mortality,
oxygenation & WB b/n VCV &PCV in general
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48. Cont,
Ventilator alarm setting
Low Expired Minute Volume Alarm
High Expired Minute Volume Alarm
Upper Airway Pressure Limit Alarm
Low Airway Pressure Limit Alarm
Oxygen Concentration Alarm
Low Oxygen Concentration (FIO2 ) Alarm
Upper Oxygen Concentration (FIO2 ) Alarm
Power Failure
Apnea Alarm
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50. Cont,
Hypoxia:
occurs when oxygen supplies are
insufficient to meet oxygen demands in a
particular compartment (PaO2<80%)
Tissue hypoxia may be subdivided into four
main Types: hypoxaemic, anaemic, stagnant
or histotoxic.
Oxygen therapy may only correct hypoxia
due to hypoxaemia,
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51. Hypoxemic respiratory failure
 is a consequence of gas exchange failure and is
recognized by hypoxemia (PaO2<60mmHg)
Hypoxaemic hypoxia( hypoxic hypoxia):
 is present when the oxygen content in the blood
is low due to low PaO2.
This occurs naturally at high altitude or occurs
secondary to right-to-left shunts, V/Q mismatch,
alveolar hypoventilation or diffusion impairment.
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52. Causes of hypoxemia
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53. Cont,
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54. Cont,
Anaemic hypoxia:
Anaemic hypoxia results from a reduced level of Hbn
available for oxygen transport.
Circulatory (Stagnant hypoxia):
s a low level of oxygen in the tissues due to
inadequate blood flow (either globally or regionally).
Histotoxic hypoxia:
Due to inability of the tissues to use oxygen due to
interruption of normal cellular metabolism..
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55. Cont,
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Hypercapnic respiratory failure: is a consequence of
ventilatory failure and is recognized by an elevated PaCO2 >45 mm
Hg at sea level).
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56. Cont,
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58. Cont,
Treatment of Acute Respiratory Failure
 find and treat the underlying cause, if possible.
Support can be given to the patient during the workup
and treatment and should not be delayed.
Noninvasive support measures including supplemental
oxygen, inhaled bronchodilators and NIV with CPAP&BPAP
More severe manifestations of respiratory failure like
ARDS, multilobar pneumonia, neuromuscular diseases,
and cardiogenic shock usually require intubation and
mechanical ventilation.
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is not a therapeutic intervention.
The goal of ventilation is to simply maintain
adequate gas exchange and metabolic function
while the underlying disease process gets treated
or resolves on its own.
Focus be on treating reversible causes of RF and
minimizing further injury to the patient.

60. Acute Respiratory Distress Syndrome
 is a diffuse inflammatory injury of the lungs responsibl
for 10% of ICU admission and 25% of cases of
prolonged MV worldwide
 Chxzed by acute onset, severe hypoxemia, and bilateral
pulmonary infiltrates without evidence of left HF
Pathogenesis:
 activation of circulat neutrophils W/C attach to the
endothelium… migrate into the lung parench …
degranulati and release inflamm cytokine
 damages the capillary endothelium,
 exudation of protein-rich fluid that fills the distal airspaces
and impairs pulmonary gas exchange
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62. Cont,
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63. Cont,
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64. Cont,
CLINICAL FEATURES:
The earliest signs of ARDS
are the sudden appearance
of hypoxemia and signs of
RD
The chest x-ray can be
unrevealing in the first few
hours after symptom onset,.
 Progressive hypoxemia
requiring mechanical
ventilation often occurs in
the first 48 hours of the
illness.
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65. Cont,
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66. Diagnostic criteria
 Many clinical features of ARDS are nonspecific, and
are shared by other conditions that cause hypoxemic
respiratory failure.
 This creates a tendency for misdiagnosis
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67. Cont,
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68. ARDS management
MECHANICAL VENTILATION
about 80% of patients with ARDS require
mechanical ventilation.
There are two general goals of mechanical
ventilation in ARDS:
(a) limit the stretch imposed on the distal airspaces
during lung inflation,
(b) prevent the distal airspaces from collapsing during
lung deflation.
Lung protective ventilation
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69. Cont,
Conventional Mechanical Ventilation uses large
VT(10-15ml/Kg).
In patients with ARDS, such VT are delivered into
compromised lungs leading to increased risk of
VILI
So the the ARDS Clinical Network developed MV
protocol consisting of low VT and application of
optimal PEEP w/c showed decreased mortality
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71. Cont,
REFRACTORY HYPOXEMIA
10 to 15% of patients with ARDS develop severe
hypoxemia that is refractory to oxygen therapy
with conventional MV.
 immediate threat to life, and need quick “rescue
therapies”
But the rescue measures available often provide
little or no survival benefit.
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72. Cont,
 High Frequency Oscillatory Ventilation
 delivers small VT (1–2 mL/kg) using rapid pressure
oscillations (300 cycles/min)
 improve arterial oxygenation, but there is no documented
survival benefit
 Inhaled Nitric Oxide (5–10 ppm)
 improve arterial oxygenation in ARDS temporarily(1-4days)
and has no associated survival benefit
 Prone Positioning
 Improve oxygenation but has little impact on mortality in
ARDS,
 ECHMO: last resort and has variable success
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73. Nonventilatory management
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Underlying cause treatment
Fluid management
Avoid positive fluid balalance and correct deficit
Steroid therapy
Early severe ARDS and Unresolving ARDS
Provide Multi-organ Supportive care
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74. References
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75. Thank you!
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