Objectives List the indications for ventilatory support List
the factors analyzed to determine initial ventilator modes and
settings Define the current modes of ventilation, listing The
advantages and disadvantages of each Basic intro to settings
Slide 3
First a Review of Ventilation formulas
http://www.youtube.com/watch?v=mF4OvuzlfXc&fea ture=related
http://www.youtube.com/watch?v=mF4OvuzlfXc&fea ture=related Ve,
VA, Compliance
Slide 4
Indications for Ventilatory Support Respiratory failure (type I
or II) Exacerbation of COPD Neuromuscular disease Coma
Slide 5
The volume of carbon dioxide eliminated per minute (which in a
steady state is equal to that produced by the body (V' CO2 ) is
dependent on the concentration of carbon dioxide in alveolar gas
and n V' A. V' CO2 =V' A alveolar CO 2 concentration or alveolar CO
2 concentration=V' CO2 /V' A.
Slide 6
Hypoxemia The condition of hypoxemia refers to the low partial
pressure of oxygen in the arterial blood. Hypoxemia is often
confused with either anoxia, asphyxia, hypoxia or anemia. Although,
these are in some way related to reduction in the levels of oxygen
in the body, these are distinct medical conditions. Anoxia is the
absence of oxygen supply in the body. This implies extremely low
levels of oxygen in the body. Asphyxia is the absence of oxygen
along with the accumulation of carbon dioxide. Hypoxia is the
deficiency of oxygen in some specific part of the body. Anemia
refers to a condition when oxygen content in the arterial blood is
low and the partial pressures in the arterial blood are high.
Hypoxemia refers to refers to a condition when oxygen content in
the arterial blood is low as also the partial pressures in the
arterial blood. http://www.youtube.com/watch?v=f8zIVc9yTMg
Slide 7
Arterial Oxygen Content (CaO 2 ) The arterial oxygen content
can be given by the following equation: Arterial Oxygen Content =
(Hgb x 1.34 x SaO 2 ) + (0.0031 x PaO 2 ) where, Hgb is the
hemoglobin SaO 2 is the percentage of hemoglobin saturated with
oxygen PaO 2 is the partial pressure of arterial oxygen
Slide 8
Clinical Manifestations of Type I Respiratory Failure Clinical
signs of hypoxemia Dyspnea Tachycardia Tachypnea Use of accessory
muscles of ventilation Nasal flaring Cyanosis peripheral and
central Central nervous system dysfunction irritability, confusion,
coma
Slide 9
Symptoms of Hypoxemia (The symptoms of hypoxemia depend on the
severity i.e. the amount by which the partial pressure has
reduced.) Symptoms of mild hypoxemia: Restlessness Anxiety
Disorientation, confusion, lassitude and listlessness
Headaches
Slide 10
Symptoms of Hypoxemia Symptoms of acute hypoxemia: Cyanosis
(Skin appearing bluish due to insufficient oxygen) Cheyne-Stokes
respiration (irregular pattern of breathing) Increased blood
pressure Apnea (temporary cessation of breathing) Tachycardia
(increased rate of heartbeats, more than 100 per min) Hypotension
(abnormally low blood pressure, below 100 diastolic and 40
systolic. Here, as an effect of an initial increase in cardiac
output and rapid decrease later.) Ventricular fibrillation
(irregular and uncoordinated contractions of the ventricles)
Asystole (severe form of cardiac arrest, heart stops beating)
Polycythemia (abnormal increase in RBCs. The bone marrow may be
stimulated to produce excessive RBCs in case of patients suffering
from chronic hypoxemia) Coma
Slide 11
Clinical Manifestations of Acute Ventilatory Failure
Slide 12
Clinical Manifestations of Type I Respiratory Failure
Auscultation Wheezing indicates bronchospasm (asthma?) Diminished
(COPD?) Unilateral wheezing endobronchial lesion, FBAO Unilaterally
diminished or absent atelectasis, infection, effusion
Slide 13
Slide 14
Clinical Manifestations of Type I Respiratory Failure
Radiologic Findings Black radiograph Hyperinflated lungs (COPD) V/Q
mismatch White radiograph Occlusion of alveoli shunt
Slide 15
Slide 16
Slide 17
Clinical Manifestations of Type II Respiratory Failure
Decreased respiratory drive Bradypnea leading to apnea Clinical
signs of decrease in respiratory drive Respiratory rate < 12 bpm
Altered state of consciousness (increase CO2, amonia, blood sugar,
ICB) Rapid, shallow breathing pattern (obesity, neuromuscular)
Evidence of trauma (brain injury) Fatigue (hypothyroidism, sleep
apnea) Radiologic findings atelectasis secondary to
hypoventilation
Slide 18
Clinical Manifestations of Type II Respiratory Failure
Neurological disease Drooling, dysarthria (unable to speak), weak
cough (ALS) Unable to swallow (Dysphagia) Muscle wasting
Diaphragmatic weakness Supine paradoxical breathing (ALS) Lower
extremity weakness, progressing superiorly (Guillain-Barre) Ocular
muscle weakness (myasthenia gravis)
Slide 19
Clinical Manifestations of Type II Respiratory Failure
Increased work of breathing Increasingly rapid, but shallow
breathing (exacerbation of COPD) Diminished breath sounds
Irritability, confusion
Slide 20
Chronic Respiratory Failure Development of respiratory failure
in patients with chronic respiratory conditions over an extended
period of time, as much as years Allows compensatory mechanisms to
adapt to the disease state Most commonly Type II failure with
compensatory metabolic alkalosis (COPD) Compensation for Type I is
polycythemia (Fibrosis/COPD) May be complicated by superimposed
acute respiratory failure
Slide 21
Chronic Respiratory Failure With Superimposed Acute RF
Precipitating factors Bacterial or viral infections Congestive
heart failure
http://www.youtube.com/watch?v=JJAMYHAwCMs&feature=related
http://www.youtube.com/watch?v=JJAMYHAwCMs&feature=related
Pulmonary embolism Chest wall dysfunction Non-compliance with
medical orders Normal blood gases for these patients may be outside
normal limits
Slide 22
Chronic Respiratory Failure With Superimposed Acute RF Goals of
therapy Normalization of pH Elevation of S a O 2 Improvement of
airflow Treatment of infections Maintain fluid status
Slide 23
Indications for Ventilatory Support Acute respiratory failure
Post-Operative respiratory failure (over sedation, complications)
Sepsis (sudden increase in VO2 and CO2 production) Cardiac failure
(MI, CHF)
Slide 24
Indications for Ventilatory Support Acute respiratory failure
ARDS (from PN, Sepsis) Trauma (blood loss, head trauma) Pneumonia
(causing plugs)
Slide 25
Indications for Ventilatory Support Apnea (sedation, drug OD)
Impending respiratory failure Inability to oxygenate
Slide 26
Clinical Manifestations of Acute Ventilatory Failure Rapid,
shallow respiratory pattern frequently have pleural space disease
(pleural effusion, hemothorax, pneumothorax).
Slide 27
Clinical Manifestations of Acute Ventilatory Failure Patients
with end-expiratory effort and wheezes on chest auscultation
frequently have small airway obstructive disease (asthma). Patients
with deep, labored chest movements frequently have pulmonary
parenchymal disease (pulmonary edema, pulmonary contusions,
space-occupying masses). Patients with obvious stridor, minimal air
movement at the nares or mouth, and marked inspiratory effort
typically have upper airway obstruction (laryngeal edema or
paralysis, foreign body aspiration). These patterns are hardly
exclusive: Often patients have multiple problems, and some patients
may have serious underlying respiratory problems and yet clinically
appear normal.
Slide 28
What nonrespiratory conditions can mimic acute respiratory
distress? Numerous disorders cause tachypnea, orthopnea, and other
signs referable to the respiratory system in the absence of true
respiratory disease. These disorders can confuse the clinician.
Disorders such as hyperthermia, shock, metabolic acidosis and
alkalosis, hyperthyroidism, fear or anxiety, pericardial tamponade,
anemia, abdominal organ enlargement or ascites, and abnormalities
with central control of respiration from drugs and metabolic or
organic central nervous system disease are all causes of signs that
may mimic true respiratory distress.
Slide 29
Clinical Manifestations of Acute Ventilatory Failure
Cardiovascular symptoms Tachycardia; when severe bradycardia
Hypertension; when severe, hypotension Vasodilation
Slide 30
Clinical Manifestations of Acute Ventilatory Failure Neurologic
symptoms Headache Drowsiness; when severe non-responsiveness
Convulsions Biots/Cheyne stokes breathing
Slide 31
Clinical Manifestations of Acute Ventilatory Failure Other
signs Sweating Redness of the skin
Slide 32
Goals of Ventilatory Support Maintenance of adequate alveolar
ventilation and oxygen delivery Restore acid-base balance
Slide 33
Goals of Ventilatory Support Reduce the work of breathing
Reduce myocardial work secondary to hypoxemia And increased work of
breathing
Slide 34
Considerations When Initiating Ventilatory Support Type of
airway: endotracheal tube vs. tracheostomy tube Pressure-controlled
vs. volume-controlled ventilation- depends on if patient has
pre-existing congestion, loss of compliance, known lung problems
http://www.youtube.com/watch?v=4O4vGPqM2RM
Slide 35
Pressure-Controlled Ventilation Pressure support ventilation
(PSV) Designed to augment spontaneous ventilation (increases
Spontaneous tidal volume) Patient-triggered, pressure- limited,
flow-cycled ventilation Used to overcome RAW imposed by ETT May be
stand-alone mode or used with SIMV/CPAP
http://www.youtube.com/watch?v=oLZ0fcJ9Rhw&NR=1
Slide 36
Pressure-Controlled Ventilation Pressure control ventilation
(PCV) Delivery of mandatory support breaths at a set inspiratory
pressure (pressure limited/time cycled) May be used in
assist-control mode or with SIMV Set pressure limit (PIP) and
Inspiratory time Volume and flow vary
Slide 37
Pressure-Controlled Ventilation Pressure control ventilation
(PCV) Useful in limiting airway pressure and providing a decreasing
flow, which may improve gas distribution and synchrony Can be set
in any patient, however most often used for patients with low
compliant lungs, especially if high PEEP levels will be used
Slide 38
Volume-Controlled Ventilation Used primarily to maintain
constant tidal volume Useful when lung mechanics are changing due
to pathophysiology Set Tidal volume based on patients IBW in a
range of 8-12 ml/kg and flow rate IBW= men 106 + 6 lbs for every
inch over 60 inches IBW=woman 105 + 5 lbs for ever inch over 60
inches For restrictive disease 5-7 ml/kg
Slide 39
Volume-Controlled Ventilation Volume control is volume limited
and flow cycled Can be set in AC or SIMV modes Direct control over
Ve I-time and pressure vary depending on patients lung
compliance
Slide 40
Pressure-Regulated Volume Control (PRVC) Ventilation Offers
pressure-controlled ventilation while guaranteeing a volume
Pressure and flow fluctuate to maintain a constant minimum TV May
not work well with restrictive lungs
Slide 41
Non-Invasive (NPPV) vs. Invasive PPV Advantages of NPPV
Avoidance of intubation Preservation of natural airway defenses
Patient comfort
Slide 42
Non-Invasive (NPPV) vs. Invasive PPV Advantages of NPPV
Maintenance of speech and swallowing Intermittent use
Slide 43
Non-Invasive (NPPV) vs. Invasive PPV Disadvantages of NPPV
Patient cooperation essential Limited access to airway during
ventilation Discomfort from mask
Slide 44
Non-Invasive (NPPV) vs. Invasive PPV Disadvantages of NPPV
Ulceration, face sores, eye irritation, rhinitis, dry nose Stomach
pain from gastric inflation Leak from improper fit Aspiration
risk
Slide 45
Non-Invasive (NPPV) vs. Invasive PPV Disadvantages of NPPV
Transient hypoxemia from mask disconnection BiPAP limited to
maximum of 30 cmH 2 O Time consuming procedure Drying of
secretions/plugs
Slide 46
Partial vs. Full Ventilatory Support Partial ventilatory
support Use of ventilator settings requiring patient to provide
portion of the ventilation
Slide 47
Modes of Partial Ventilation Synchronized intermittent
mandatory ventilation (SIMV) Pressure support ventilation (PSV)
Volume support ventilation (VSV), PSV will fluctuate depending on
set minimum VT
Slide 48
Modes of Partial Ventilation Adaptive pressure ventilation
(APV) Adaptive support ventilation (ASV) Mandatory minute volume
ventilation (MMV) WE WILL TALK ABOUT THE ADAPTIVE MODES IN A
SEPARATE LECTURE
Slide 49
Full Ventilatory Support Ventilator provides the full minute
ventilation; no patient contribution Assist-control mode
Slide 50
Initial Ventilator Settings Choice of mode (AC, IMV/SIMV, PCV,
PRVC, APRV) Tidal volume (V T ) 8 to 12 ml/kg IBW Rate (f)
typically backup rate of 8-12 breaths /min
Slide 51
Initial Ventilator Settings Trigger sensitivity (either flow or
pressure) Typically -0.5 to -2.o cmH 2 O to minimize effort May
need to be adjusted to avoid auto-cycling on some ventilators
Applies only to patient triggered breaths
Slide 52
Initial Ventilator Settings Trigger sensitivity Flow triggering
may have slightly less work than pressure triggering
Slide 53
Initial Ventilator Settings Inspiratory flow 60 to 80 L/min. to
achieve an inspiratory time of 1 second and an I:E ratio of 1:2 or
better May require higher flows in patients with COPD to lengthen
expiratory time, allowing improved gas exchange
Slide 54
Initial Ventilator Settings Flow waveform Decelerating or
decreasing flow waveform generally delivered in pressure
ventilation Decelerating waveforms generally decrease peak
inspiratory pressure, but increase mean airway pressure
Slide 55
Decelerating set in VC, automatic in PC
Slide 56
Constant Flow VC only Increases MAP, decreased I-time
Slide 57
Initial Ventilator Settings Oxygen percentage (F I O 2 ) If
little is known concerning patient, begin with F I O 2 of 1.0,
decreasing to 0.4 to 0.5 as quickly as possible Patients with known
blood gas results should be given F I O 2 consistent with the known
data
Slide 58
Initial Ventilator Settings Positive end-expiratory pressure
(PEEP) PEEP of 5 cmH 2 O is advocated by some as physiologic PEEP
Should be adjusted as necessary to allow F I O 2 to be reduced to
0.4 as quickly as possible
Slide 59
Initial Ventilator Settings Pressure limit Start at 50 cmH 2 O
Adjust to 10 to 20 cmH 2 O above peak pressure when patient is
stable