ventilation understanding for startes

1. BASICS OF MECHANICAL
VENTILATION
BY
Dr C ABHIRAM KUMAR,
Fellow in PICU,Aster CMI

2. OVERVIEW
 INTRODUCTION
 BASIC TERMINOLOGIES
 OXYGENATION
 VENTILATION
 BASIC MODES OF VENTILATION

3. INTRODUCTION
 Ventilation is moving in and out of gases into the
lungs through the airways
 Respiration is process of gas exchange within the
lungs(external) or at the tissue level(internal)

4. Basic parts of
ventilator
Compressor
Blender
Flow meter
Inspiratory circuit
Patient outlet
Expiratory circuit
Expiratory valve
assembly

5. BASIC TERMINOLOGIES
 Fi𝑶𝟐 ∶ fraction of oxygen in inspired air
21%-100%
 Peak Inspiratory Pressure(PIP):
highest pressure in inspiratory cycle
opens up alveoli
PIP α R/C
 Positive End Expiratory Pressure:
pressure at the end of expiration in the lungs
prevents collapse of recruited alveoli

6.  Mean Airway Pressure(Paw)
average pressure attained during the respiratory
cycle
𝑃𝑎𝑤 =
𝑘 𝑃𝐼𝑃×𝑇𝑖 +(𝑃𝐸𝐸𝑃×𝑇𝑒)
𝑇𝑖+𝑇𝑒
 I:E Ratio:
ratio of inspiratory to expiratory time
inspiratory or expiratory time should not be below
Tc

7.  Tidal Volume:
volume going in and out of lungs in each cycle
newborns: 4-6 ml/kg
older children: 5-8 ml/kg
 Rate/Frequency:
number of breaths per minute ventilator delivers
affects minute ventilation
 Flow Rate:
flow of gas through the circuit
minimum of twice the minute ventilation

8. OXYGENATION
 Addition of oxygen to the blood through gaseous
exchange
 Takes place at alveolar capillary membrane

9.  Factors on which oxygenation depends:
 Oxygenation(paO2) α MAP × FiO2
 MAP increases with increase in:
Peak inspiratory pressure
Positive end expiratory pressure
I:E ratio
Flow rate

10.  Oxygenation Indices:
 useful to quantify oxygenation and track the course
of the disease
Alveolar arterial pO2 difference(A-a) pO2
paO2/FiO2 ratio
Oxygenation index: MAP × FiO2 × 100/paO2

11. VENTILATION
 Exchange of gases between the lungs and
atmosphere
 Mainly eliminates carbon-di-oxide from the lungs
 Ventilation α (tidal volume – dead space) × R.R
 Tidal volume α delta p (PIP-PEEP)
 Ventilation increases by:
increasing tidal volume
increasing PIP
decreasing PEEP
increasing frequency/rate

12. BASIC MODES OF VENTILATION
 Variables on which modes depends:
Control variables
Phase variables
 Control variables: remains constant as the ventilator
load changes
They include pressure, volume, flow and time.

13. Phases of respiratory cycle

14.  Phase Variables: respiratory cycle can be divided
into four phases based on these phase variables
 Trigger: variable used to initiate inspiration
triggered by ventilator( time cycled)
triggered by patient(flow or pressure)
Limit variable: ventilator cannot go beyond the limit
during inspiration
inspiration need not be terminated

15.  Cycle variable: termination of inspiration
time, pressure, flow, volume
 Baseline variable: variable controlled during
expiratory phase such as PEEP
 Mandatory breath: breath is triggered and cycled by
ventilator
 Spontaneous breath: breath is triggered and cycled
by patient

16. Mode Trigger Rate Cycle Limit
IMV Ventilator Ventilator Ventilator Ventilator
SIMV Patient Ventilator Ventilator Ventilator
AC Patient Patient Ventilator Ventilator
PSV Patient Patient Patient Ventilator
IMV- Intermittent mandatory ventilation
SIMV- Synchronized intermittent mandatory ventilation
AC- Assist control
PSV- pressure support ventilation

17. THANK YOU