Transcript Systemic Lupus Erythematosus

Mechanical Ventilation
BY: Jonathan Phillips
Introduction

Conventional mechanical ventilation refers to
the delivery of full or partial ventilatory support
by a volume –cycled mechanical ventilator or by
pressure support. It can include the maintenance
of positive airway pressure at the end of
exhalation i.e.. PEEP.
Indications



The decision to initiate mechanical ventilation
entails potentially serious complications.
The main indication for mechanical ventilation
is ARF.
The parameters needed include respiratory rate
>35, inspiratory force < 25cm H2O, vital
capacity < 10-15ml/kg, PaO2 <60 mm Hg with
FIO2 >60%, PaCO2 >50mmHg, with pH <
7.35. and an absent gag or cough reflex.
Common disorders for Mechanical
ventilation




Acute pulmonary parenchymal diseases,
pneumonia, ARDS
Cardiogenic pulmonary edema
Neuromuscular disorders: myasthenia gravis,
Guillian Barre syndrome, poliomyelitis, and
spinal cord trauma
Systemic illnesses include shock and sepsis
Volume cycled ventilation




The controlled variables of tidal volume and
inspiratory flow determine airway pressure and
inspiratory time. Variations in airway resistance
or lung compliance alter airway pressures but do
not affect minute ventilation.
Controlled mechanical ventilation
Assist-control
Intermittent mandatory ventilation
Controlled mechanical ventilation


Minute ventilation is completely dependent
upon the rate and tidal volume set on the
ventilator. Any respiratory efforts made by the
patient do not contribute to minute ventilation.
CV is required in patients who are not making
respiratory effort, spinal cord injury, OD or
pharmacologic paralysis
CMV


Combined neuromuscular paralysis and
controlled mechanical ventilation can also be
used to avoid volutrauma in patients with ARDS
and to avoid baratrauma in asthmatics who are
difficult to ventilate.
In these settings hypercapnia is accepted
provided that oxygenation is maintained.
Assist control





In A/C mode the ventilator senses an inspiratory effort by the patient and
responds by delivering a preset tidal volume.
Every inspiratory effort that satisfies the ventilators demand valve trigger
threshold, initiates delivery of the preset tidal volume.
A control mode back up rate is set on the ventilator to prevent
hypoventilation
Patient work is required to trigger the ventilator, and continues during
inspiration. In the presence of auto-peep the effective trigger threshold is
increased by the amount of auto-peep present.
An ACCP consensus statement cautioned against the initial use of A/C in
awake patients with obstructive airway disease, since this can lead to
progressive hyperinflation.
Intermittent Mandatory ventilation


IMV, the degree of ventilator support is
determined by the select IMV rate. At regular
intervals, the ventilator delivers a breath based
upon a preset tidal volume and rate.
The patient is allowed to breathe spontaneously
through the ventilator circuit at a tidal volume
and rate according to need and capacity.
IMV


Most present day ventilators synchronize the
intermittent mandatory ventilation breaths with
inspirtatory effort by the patient, a modality
termed synchronized IMV or SIMV.
This modification requires a trigger modality,
either a demand valve or flow-by, both of which
need patient effort to trigger and therefore
increase the work of breathing.
Pressure Support Ventilation




PSV is flow-cycled in that, once triggered by a demand
valve, the preset pressure is sustained until the
inspiratory flow tapers, usually to 25% of its maximal
value.
PSV tends to be a comfortable ventilatory modality
because the patients has greater control over ventilator
cycling and flow rates.
Close monitoring is required whenever PSV is used
alone because neither tidal volume or minute ventilation
is guaranteed.
PSV is more appropriate during weaning from
mechanical ventilation.
Vent management





FIO2-hypoxia is more dangerous than is brief exposure
high levels of O2.
The initial FIO2 should be 100%
FiO2 can be made to achieve a PaO2 greater than
60mmHg or SaO2 >90%.
Attempts should be made to utilize the lowest possible
fraction of FIO2 that maintains the arterial oxygen
saturation >90% or PO2 >60%
An FIO2 below 0.5 is preferable to minimize oxygen
toxicity.
Vent Management
Respiratory rate of 10-15 breaths per minute to begin.
 In COPD patients, minute ventilation should be adjusted to
achieve baseline PaCO2 and not necessarily a normal PaCO2.
Hyperventilation with resultant metabolic alkalosis in these patients
may be associated with serious electrolytes shifts and
arrhythmias.
Initial tidal volumes usually can be set at 10-12 ml/kg
Patients with decreased ling compliance (ARDS)
Often need smaller lung volumes 6-8 to minimize peak airway
pressures.

Vent management
PEEP



Positive end-expiratory pressure is defined as the
maintenance of positive airway pressure at the
end of expiration.
It can be applied in both CPAP and continuous
positive pressure pressure ventilation.
PEEP increases lung compliance and
oxygenation while decreasing the shunt fraction
and the work of breathing.
Vent Management
PEEP



The main goal of PEEP is to achieve a PaO2
greater than 55-60 mm HG with a FIO2 less
than or equal to 60%.
PEEP is applied in 3-5 cm H2O increments.
PEEP >10 should not have their PEEP
removed abruptly, because removal can result in
collapse of distal lung units, worsening of shunt,
and potentially life threatening hypoxemia.
Vent management
Inspiratory flow rate


Low flow rates can be associated with prolonged
inspiratory times that can lead to the
development of auto-PEEP.
The resultant hyperinflation can affect patient
hemodynamics adversely by impairing venous
return to the heart.
Vent Management
Trigger sensitivity



Pressure triggering to initiate either a machine assisted
breath or to permit spontaneous breathing between
IMV breaths, or during trials of CPAP.
The patient must generate a decrease in the airway
circuit pressure equal to the selected pressure sensitivity.
The smallest trigger sensitivity should be selected,
allowing the patient to initiate mechanical or
spontaneous breaths without causing the ventilator to
autocycle.
Vent Management
Flow-by
Refers to triggering of the ventilator by changes in
airflow as opposed to changes in airway pressure.
▪ Flow sensitivity, the rate of inhaled flow that triggers the
ventilator to switch from base flow to either a machine
delivered or a spontaneous breath.
▪Flow by triggering requires less work of breathing when
used with patients receiving CPAP.
▪However it offers no advantage over demand valve
triggering when using pressure support ventilation.

Weaning Strategies


The level of support ventilation is decreased
gradually, and the patient assumes more of the
work of ventilation.
IMV –allows a change from mechanical
ventilation to spontaneous breathing by
decreasing the ventilator rate gradually.
Weaning strategies



T-Tube intersperses periods of unassisted
spontaneous breathing through a T-Tube with
periods of ventilator support.
Short daytime periods 5-15 minutes 2-6 times a
day with increasing periods.
Extubation may be appropriate when the patient
can tolerate more than 30-90 minutes of T-tube
ventilation
Weaning strategies



PSV is used when respiratory muscle weakness
appears to be compromising weaning success.
A decrease in respiratory rate with achieved tidal
volumes of 10-12 ml/kg signals that the optimal
PSV level has been reached. At this point PSV
can be reduced.
Once PSV level 5-8 cm H2O is reached the
patient can be extubated.
Extubation







Should be performed early in day
Patient should be told to cough
Elevate head to 30-45 degrees
Oropharynx should be suctioned
Cuff deflated
Patient extubated and face mask placed
Patient encouraged to deep breath and cough
with HHN to follow
Competency Exam
Questions





1. Which is the main indication for vent
management?
A. Acute respiratory failure
B. Severe COPD
C. CO2 retention
D. Severe pneumonia
Questions





1. Which is the main indication for vent
management?
A. Acute respiratory failure
B. Severe COPD
C. CO2 retention
D. Severe pneumonia
Questions





2. Which is not a guideline for withdraw of
mechanical ventilation?
A. PaO2 >60
B. FIO2<50%
C.PEEP >10
D.Vital capacity >10
Questions





2. Which is not a guideline for withdraw of
mechanical ventilation?
A. PaO2 >60
B. FIO2<50%
C.PEEP >10
D.Vital capacity >10
Questions





3. An FIO2 below this value is preferable to
minimize oxygen toxicity?
A.80%
B.70%
C.60%
D.50%
Questions





3. An FIO2 below this value is preferable to
minimize oxygen toxicity?
A.80%
B.70%
C.60%
D.50%
End of Lecture