/*Old .. i have written it in my first year of residency… my contains some errors but i left them for memories :)*/
Controlled Modes
Ventilator delivers at present frequency . this may be pressure or volume TARGETED
Volume Controlled
Ventilator delivers at present frequency preset Tidal volume
example
Vt 500
F=12
in one minute = cycles in 60 seconds =60/12 5 secs thus cycle = 5 sec
set I:E Ratio
Limitations
no patient interaction So the Patient should be paralyzed
ventilator does not respect peak inspiratory pressure
pressure Controlled
according to preset inspiratory pressure Ventilator delivers Vt until it reaches the desired pressure
if peak inspiratory pressure increased (tube block for example ) small tidal volume will be delivered … hypoxemia and hypo ventilation may occur
example
insp.pressure =20 rr=12
set I:E Ratio
Limitations
no patient interaction So the Patient should be paralyzed
if peak inspiratory pressure increased (tube block for example ) small tidal volume will be delivered … hypoxemia and hypoventilation may occur
Assisted Controlled (A/C) –volume or pressure controlled
Ventilator Delivers preset Tidal Volume in response to patient initiated breath
example
(A/C) pressure controlled
inspiratory pressure = 20 cmh2o
set trigger sensitivity
back up mode ( apnea parameters) should be set
(A/C) volume controlled
Vt = 500
set trigger sensitivity
I:E Ratio
back up mode ( apnea parameters) should be set
limitations
Respiratory alkalosis
air trapping may occur
SIMV ( Synchronized Intermittent Mandatory ventilation)
–volume or pressure controlled
Ventilator delivers Synchronized breaths at preset Vt or Insp.pressure..in addition to allowing patient to breath spontaneously –usually accompanied with pressure support in spontaneous breathes
adjustment
SIMV volume controlled
for mandatory cycle
Vt 500
RR 12/min or less than 8 as weaning mode
I:E ratio
trigger Sensitivity
For spontaneous cycles
pressure support may be adjusted
SIMV volume controlled
insp.pressure 20 cmh2o
RR 12/min or less than 8 as weaning mode
I:E ratio
plateau Time may be added to control i: Ratio
trigger Sensitivity
For spontaneous cycles
pressure support may be adjusted
So we have 3 types of breath
mandatory cycle
spontaneous cycles
assisted cycle (patient initiate breath and ventilator delivers Vt as Assisted mode
Pressure Support ventilation (PSV)
patient initiate breath and ventilator delivers preset positive pressure
pressure is maintained till inspiratory flow rate decreases to specified level
I:E ratio is determined by Patient
BackUP mode have to be Adjusted
Setting I:E Ratio
Volume Controlled Mode
Most of Ventilators you adjust Peak Flow Rate
example
500 ml could be delivered in eg. 1 sec or 2 sec
So you adjust ventilator peak flow rate in L/min unit (eg. 60L/min)
Pressure controlled Mode
Most of Ventilator you just enter I:E Ratio Manually as digital value either by ratio or time
setting Trigger sensitivity
pressure triggering :usually -1 to -1.5 cmh2o
Flow-by : instead of patient generating -ve insp. pressure to trigger ventilator patient inspiratory flow cause flow to decrease that make inspiration easier for patient as delay in initiationof inspiration is minimized
Adjustment
Basal Flow : eg. 5L/sec
triggering flow : eg. 3L/sec ( half of Basal )
if triggering value is too sensitive auto cycling will occur
If to Insensitive Work of breathing will increase
Positive End Expiratory Pressure (PEEP )
Ventilator applies a positive pressure at the end of exhalation thus supra atmospheric pressure is maintained throughout th breathing cycle
used for improve oxegenation and lung compliance
problems
Decrease Cardiac output
Decrease renal blood flow
Increase Intra cranial pressure
Increase risk of Barotrauma