2. • There are 2 common ways to change PaO2:
1. FIO2.
2. PEEP (when a shunt is present)….
HOW To improve oxygenation ..?
1.Increase fio2
2.Increase PEEP
3.Increase inspiratory time
HOW to manage increased Paco2 .. ?
1. Increase TV
2. Increase RR
Ventilator New rate for desired Pco2= (current RR *
paco2) /desired Paco2
3. • Constant ventilator settings according to Mode of
Ventilation.
In VCV settings include ..
• TV
• RR
• Fio2
• PEEP
• Flow inspiratory Time
In PCV settings include ..
• Fio2
• Inspiratory pressure
• RR
• Inspiratory time or I:E ratio
4. Tidal Volume
• In general, the programmed TV is recommended to be 8 to 15
ml/kg with an associated minute ventilation of 150 to 250
ml/kg/min
According to the cause of ventilation .. .
• A larger tidal volume and lower rate (12-15 mL/kg IDW ) suitable
for patient with neuromuscular disease or post-operative patients
with normal lungs
• A slightly smaller tidal volume (8-10 mL/kg IBW) has been
suggested for patients with obstructive lung disease as COPD.
• A smaller initial tidal volume (6-8 mL/kg IBW) is appropriate for
patients with acute lung injury or ARDS ( low tidal volume
strategy )
5. • Formula to calculate IBW …
• MEN: Ideal Body Weight (in kilograms) = 50 +
2.3 kg per inch over 5 feet.
• WOMEM: Ideal Body Weight(in kilograms) = 45.5 +
2.3 kg per inch over 5 feet.
• For females: PBW = 45.5 + 0.91 * (height - 152.4)
• For males: PBW = 50 + 0.91 * (height - 152.4)
6. Frequency (RR)
• Normal adult spontaneous respiratory rate is 12-
20 per minute.
• If the patient has no spontaneous respirations,
the range of 12 to 20 should be used.
• If the patient is “triggering” the machine a safe
RR of 10-12 should be used.
7. Fio2
• Setting of FIO2 depends on the patient’s previous PaO2 and
FIO2.
• A safe starting point is 40% for most situations
• Further adjustment is based upon ABG, oximetry, and other
clinical measurements.
• If the FIO2 is 60% or greater, an increase in CPAP or PEEP may
be indicated to minimize oxygen toxicity complications.
8. INSPIRARTORY FLOW RATE VI
• The rate at which gas is delivered to the patient during the
inspiratory phase .
• Normal level 40-100 L/ m
• VI = VT / TI
• Used to provide the desired TI, I:E ratio, and inspiratory
pattern.
• Proper VI = VE x (I +E)
• Slower VI is generally used in patients with ↑ Raw and/or
poor gas distribution
• Fast VI may ↓ WOB and improve patient comfort in
patients with high inspiratory demand.
9. • Flow Precautions …
• Slow VI may not meet the patient's demand
(flow-starvation), resulting in ↑ WOB, patient
discomfort, and possibly hypoventilation
• Slow VI results in long TI and short TE, leading
to patient discomfort and/or air-trapping
(auto-PEE P).
• Fast VI may cause ↑Raw, ↑ PIP, and/or ↓
distribution of ventilation.
10. PEEP
• DEFINITION — Positive end-expiratory pressure
(PEEP) is the alveolar pressure above atmospheric
pressure that exists at the end of expiration. There
are two types of PEEP:
●Extrinsic PEEP – PEEP that is provided by a mechanical
ventilator is referred to as applied PEEP
●Intrinsic PEEP – PEEP that is secondary to incomplete
expiration is referred to as intrinsic PEEP or auto-
PEEP
11. • typically, a small amount of PEEP is applied
routinely in most patients undergoing
mechanical ventilation (3 to 5 cm H2O; also
known as physiologic PEEP)
• In select populations (eg, acute respiratory
distress syndrome), it is increased to maintain
adequate oxygenation (>5 cm H2O;
supraphysiologic PEEP
12. PEEP indications
• Acute respiratory distress syndrome
Applied PEEP, usually at levels ≥5 cm H2O, are
indicated in most patients with acute respiratory
distress syndrome (ARDS) and
other types of hypoxemic respiratory failure.
Routine mechanical ventilation.
Patients with auto-peep.
Cardiogenic pulmonary edema.
Intraoperative patients.
Postoperative patients.
13. Action of PEEP
• Reduces trauma to the alveoli
• Improves oxygenation by ‘recruiting’ otherwise closed alveoli,
thereby increasing the surface area for gas exchange.
• Increases the functional residual capacity- the reserve in the
patients lungs between breaths which will also help improve
oxygenation.
• Ventilation/perfusion mismatches are improved.
• Increases the compliance of the lung- compliance is the
relationship between the change on volume and the change
in pressure in the lung. With PEEP, less pressure is needed to
get the same volume of air into the lung as the alveoli are
already partially inflated and therefore do not need that high
initial pressure to open them. (Remember the balloon
analogy- hard to blow up initially, but then much easier to
inflate after the initial breath)
14. • 0.9 - 1.2 sec
• In VV, TI is commonly the result of VT/VI
• In PV, TI is commonly a set parameter.
• Short TI's are commonly used in patients with ↓
CLT (short TC).
• Longer TI's are commonly used in patients with ↑ Raw
• Long TI's are used to ↑ Paw (↑ TI → ↑ Paw → ↑
PaO2).
The longer the TI, the more time available to deliver
the VT, hence ↑ alveolar distension and ↑ gas
exchange
INSPIRATORY TIME
16. • TI Precautions
Short TI (and slow VI) may cause ↓
VT resulting in hypoventilation and
hypoxemia.
Long TI may cause patient discomfort, patient-
ventilator asynchrony and hypoventilation.
The longer the TI the greater the mean Paw
and effects on the heart and lungs .
