mech vent cardio 13dec08.ppt111111111111

Inadequate respiratory drive
Inability to maintain adequate alveolar ventilation
Hypoxia
Decision to provide MV should be based on clinical examination and assessment of gas exchange by blood gas analysis. The principal goal of MV in the setting of respiratory failure is to support gas exchange while underlying diseased process is reversed.

1. Mechanical Ventilation:
When And How To Apply
Prof. AnupamGoswami.
Department of Anaesthesiology.
IPGME & R, Kolkata

2. Clinical Applications
With the use of muscle relaxants in anaesthesia
Respiratory/Ventilatory failure
Neural/muscular disorders
Thoracic cage problem
Upper airway obstruction
Bronchospasm/obstruction
Lung parenchymal problems i.e. ARDS, infection & oedema
To increase CO2 excretion
LVF
Pulmonary Hypertension
Intracranial Hypertension

3. Indications of mechanical ventilation
Inadequate respiratory drive
Inability to maintain adequate alveolar ventilation
Hypoxia
Decision to provide MV should be based on clinical
examination and assessment of gas exchange by blood
gas analysis. The principal goal of MV in the setting of
respiratory failure is to support gas exchange while
underlying diseased process is reversed.

4. Parameters to guide
Respiratory rate>35
Inspiratory force≤25 cm H2O
Vital capacity<10-15 ml/kg
PaO2 (< 60 mm Hg with FIO2 > 60%)
PaCO2 ( > 50 mm Hg with pH < 7.35)
Absent gag or cough reflex

5. Currently used modes of mechanical
ventilation
Controlled mechanical ventilation (CMV)
Assist controlled ventilation (ACV)
Intermittent mandatory ventilation (IMV)
Synchronized IMV (SIMV)
Pressure controlled ventilation (PCV)
Pressure support ventilation (PSV)

6. CMV
Patient making no respiratory effort at all
Patient is entirely under control of preset tidal
volume (VT) and respiratory frequency (f)

7. ACV
ACV is a form of triggered inspiratory assistance
which has been used to support patients who are
breathing spontaneously
The triggered asistance is in the form of volume
controlled breath which is triggered by patient’s
inspiratory effort

8. IMV
Allows patient to breathe at a spontaneous rate and
tidal volume without triggering the ventilator
Ventilator adds additional mechanical breaths at a
preset rate and tidal volume which may not
synchronize with the inspiratory effort

9. SIMV
Allows patient to breathe at a spontaneous rate
and tidal volume
Ventilator adds additional mechanical breaths at
a preset rate and tidal volume triggered by the
patient’s inspiratory effort ( i.e. synchronized )

10. SIMV : Potential advantages
Less respiratory alkalosis
Fewer adverse cardiovascular effects due to
lower intra thoracic pressures
Less requirement of sedation and paralysis
Maintenance of respiratory muscle function
Facilitation of long term weaning
In some patients respiratory muscle fatigue may
cause failure to wean from ventilator

11. PCV
It refers to CMV in which all breaths are
pressure limited and time sited with no
possibility of pt. triggering
The required tidal vol. may/ may not be
achieved

12. PSV
It is pt. triggered pressure supported mode
where each inspiratory effort of the pt. is
augmented by the ventilator at a preset level of
inspiratory pressure
During PSV the pt. decides the resp. rate, insp.
time and tidal vol.

13. PEEP
Defined as maintenance of positive airway pressure at
the end of expiration
Can be applied on spontaneously breathing patient as
CPAP or during mechanical ventilation
Appropriate application of PEEP improves lung
compliances, oxygenation, shunt fraction and work
of breathing

14. PEEP cont…..
PEEP peak and mean airway pressure which can increase
possibilities of barotrauma and cardiovascular compromise
Used primarily in hypoxic resp failure (ARDS, cardiogenic
pulm edema)
In COPD prevents dynamic airway collapse during expiration
Main goal is to achieve P
aO
2> 60 mm Hg with FIO
2 < 60%
while avoiding significant cardiovascular sequelae

15. PEEP cont…..
Patients receiving significant amount of PEEP
( > 10 cm H2O ) should be weaned off the
PEEP ( by 3-5 cm H2O ), as sudden withdrawal
can lead to collapse of distal lung units causing
worsening shunt and hypoxemia

16. CPAP
Definition
Application of constant positive pressure throughout
the spontaneous ventilatory cycle
No mechanical inspiratory assistance is provided
Requires active spontaneous respiratory drive
Same physiologic effects as PEEP

17. BiPAP
Providestwolevelsofpressures:
Thehigheronetoassistpatientswithinspiratorypositiveairway
pressure(IPAP)toreducetheinspiratoryworkofbreathing.
Theloweronetomaintainexpiratorypositiveairwaypressure
(EPAP).
ThevariationofairwaypressuresduringIPAPandEPAPsimulatesa
controlledventilation.
ThetermBiPAPisoftenusedinterchangeablywithnon-invasive
positivepressureventilation(NIPPV)andbi-levelnon-invasive
pressuresupportventilation(NIPSV).
CPAPisactivewhenIPAP=EPAP

18. CPAP/BiPAP

19. Ventilator management
FIO2
Initial FIO2 should be 100%
Adjustments of FIO2 to achieve P
aO
2> 60 mm
Hg or SaO2 > 90%
Hypoxia is more dangerous than high inspired
O2 level

20. Ventilator management Contd..
Respiratory rate & tidal volume:
Initially set at 10-15 breath/min with 10-12
ml/kg tidal
Decreased in ARDS to 6ml/kg to minimize
peak airway pressure
PIFR 60 L/min
I:E ratio 1:2
PEEP 3 to 5 cm H20
Trigger sensitivity -1 to -2 cm H20

21. Weaning
Methods:
Abrupt discontinuation
T-tube spontaneous breathing trial
SIMV
SIMV + PSV

22. Weaning
Nutrition–ensure adequate nutrition,
correct electrolytes
Secretions ---clear regularly, avoid dehydration
Neuromuscular factors---avoid NMBs, and
unnecessary corticosteroids
Obstruction of airway–bronchodilator where
necessary, exclude foreign body
Wakefulness---avoid over sedation, wean in the
morning when the patient is most awake

23. Weaning contd.
Guidelines for assessing withdrawal form mech.vent.:
P
aO
2> 60 mm Hg with FIO
2 < 40%
PEEP ≤5cm H2O
Pa CO2<45 mm Hg and pH acceptable
Spontaneous tidal volume>5ml/kg
Vital capacity > 10 ml/kg

24. Weaning contd.
MV <10 l/min
Negative inspiratory presure ≥25 cm H2O
Resp. rate <30/ min
Rapid shallow breathing index (ratio of resp rate to tidal
volume)< 100 breaths/min/ L
Stable vital signs after 1-2 hr spontaneous breathing
trial
No significant arrhythmia

25. Weaning contd.
The underlying disease process should have
improved.
The patient must be stable haemodynamically
and psychologically, without sepsis and overt
CNS depression.

26. Extubation
Should be performed early in the day when full ancillary staffs
are available
Patient should be clearly educated about thessss procedure
and possible need for re-intubation
Elevation of head by 30-45 degrees to improve diaphragmatic
function , re-intubation equipments should be ready at hand
Oropharyngeal suction prior to extubation
High humidity oxygen should be administered after
extubation
To encourage coughing and deep breathing