Transcript Monitoring and Management of Ventilatory Support

Monitoring and Management of
Ventilatory Support
Educational Objectives
• List the reasons for monitoring the patient receiving ventilatory
support
• List and describe the methods of evaluating patient oxygenation
• List and describe the methods of evaluating patient ventilation
• List and describe the ventilator parameters monitored
• List the normal hemodynamic values
• Describe the effects that mechanical ventilation may have upon
the hemodynamic parameters
Reasons for Monitoring the Patient
1. Establish baseline measurements
2. Allow trending to be observed in order to
document progress or lack of progress
3. Determine efficacy of treatment in order to
modify as needed
4. Determine limits of alarm parameters
Evaluation of Oxygenation – is There a
Problem?
• Physical Findings
– Heart rate
– Respiratory rate
– Work of breathing
• Use of accessory muscles
• Retractions
Evaluation of Oxygenation – is There a
Problem?
 Physical Findings
– Cyanosis
• Peripheral
• Central or circumoral (surrounding the mouth)
– Level of consciousness/mental status
• Confusion
• Drowsiness
• Anxiety
Evaluation of Oxygenation – is There a
Problem?
 Laboratory Findings
– Arterial blood gases
• PaO2
• SaO2 (measured or calculated?)
• Hemoglobin (Hb)/Hematocrit (Hct)
• Total oxygen content (CaO2)
– Level of consciousness/mental status
• Confusion
• Drowsiness
• Anxiety
– Pulse oximetry
– Lactic acid levels
Determine Cause of Hypoxemia
 CO-Oximetry Results
– Oxyhemoglobin (HbO2)
– Carboxyhemoglobin (HbCO)
– Methemoglobin (MetHb)
– Hemoglobin (Hb)/Hematocrit (Hct)
Determine Cause of Hypoxemia
 Laboratory Findings
– Oxygen consumption (O2)
• Normal value – 250 mL/min
• Determined by Fick Equation
Where
is cardiac output, CaO2 and
are arterial
and mixed venous O2 content
• Increase in oxygen consumption necessitates increase in
oxygen delivered
Determine Cause of Hypoxemia
– Alveolar-arterial Gradient [P(A-a)O2]
• Normal value – 5 to 15 mm Hg while breathing room air;
increases to 100 to 150 mm Hg while breathing 100%
oxygen
• Determined by subtracting arterial value from arterial
blood gas result from alveolar value using alveolar air
equation
Determine Cause of Hypoxemia
– Arterial to Alveolar Oxygen Ratio (PaO2/FIO2)
• Normal Value – 400 to 500 mm Hg while breathing
room air
• Used to define acute lung injury (ALI) and acute
respiratory distress syndrome (ARDS)
– PaO2/FIO2 < 300 mm Hg in ALI
– PaO2/FIO2 < 200 mm Hg in ARDS
Determine Cause of Hypoxemia
 Radiologic Findings
– Consolidation
– Fluid
– Free air
Management Options – FIO2
• If FIO2 < 0.6, increase oxygen concentration;
if no PEEP is employed, may add 5 cmH2O of
PEEP first
• If FIO2 > 0.6, consider reducing as soon as
patient’s condition permits to avoid
complications
Management Options – FIO2
 Titration of Oxygen Level
– If the patient’s oxygenation status is unknown or critical,
always start ventilatory support with an FIO2 of 1.0
– General goal – maintain PaO2 between 60 and 80 mmHg
or SpO2 greater than 90%
– Determination of desired PaO2
Desired PaO2 = Desired FIO2 x Actual PaO2
FIO2 (Actual)
Management Options – FIO2
– General guideline for reduction of FIO2
• Decrease in increments of 5 to 10%
• Follow each reduction by drawing arterial
blood gases or oximetry; allow at least
fifteen minutes after the change for
equilibration of blood
Management Options – PEEP
Positive End Expiratory Pressure (PEEP)
Maintenance of baseline pressure above atmospheric level
• Minimum PEEP
– Least amount of PEEP necessary to achieve and
maintain a PaO2 of at least 60 mmHg
Management Options – PEEP
• Optimal PEEP
– The level of PEEP at which oxygen delivery is
maximized while minimizing hemodynamic side
effects
– Generally only employed on patients requiring
> 10 cm H2O
Management Options – PEEP
 Method for Determination of Optimal PEEP
– Determine baseline values of blood pressure,
mixed venous oxygen level, arteriovenous oxygen
content difference, PaO2, static compliance, and
cardiac output
– Increase level of PEEP in increments of 2 cmH2O,
measuring values at each increment
– When a decline in oxygen delivery is observed, the
optimal PEEP has been exceeded
– Return PEEP level to previous increment
Management Options – PEEP
 General Guidelines for Reduction of PEEP
– Decrease in increments of 2 cm H2O
– Follow each reduction by drawing blood gases or
oximetry; allow at least fifteen minutes after the
change for equilibration of blood
– Reduction of PEEP to zero prior to extubation
may be neither necessary nor advantageous
Management Options – Tidal Volume
 Increasing Tidal Volume (VT) may be used for
recruitment of alveoli if hypoventilation
contributes to hypoxemia
Normal Value – 6 to 12 mL/kg IBW
Management Options – Inspiratory Time
 Prolongation of inspiratory time to a point
where inspiratory time exceeds expiratory
time
Normal I:E ratio – 1:1.5 to 1:2
Management Options – Inspiratory Time
 Principle of Use
– Increase in inspiratory time (TI) causes increase
in
– Increase in
aids in maintaining integrity of
alveoli and recruiting atelectatic alveoli
– Associated with improvement in
– Associated with improvement of PaO2 in patients
with ARDS
Management Options – Bronchial
Hygiene
• Postural drainage
• Percussion
• Adequate humidification
• Ambulation, sitting up, turning patient
Management Options – Patient
Positioning
• Ambulation, sitting up helpful in improving
oxygenation
• Turning patient from side to side aids in
bronchial hygiene
Management Options – Patient
Positioning
 Prone Positioning
– May result in dramatic improvement in
oxygenation in patients with ARDS and ALI
– Care must be taken to ensure tubes and lines are
not displaced during turning
– May improve
and reduce shunting by
removing pressure of the heart on the dorsal
regions
Evaluation of Ventilation – Physical
Findings
 Breathing Patterns
– Apnea
– Tachypnea
– Bradypnea
– Abnormal breathing patterns
 Work of Breathing
– Use of accessory muscles
– Retractions
Evaluation of Ventilation – Physical
Findings
 Heart Rhythms
– Abnormal rhythms
– Tachycardia
– Bradycardia
 Chest excursion
 Altered Mental State
– Anxiety
– Confusion
– Combativeness
– Somnolence
Evaluation of Ventilation – Diagnostic
Findings
 Arterial Blood Gases
– Increased PaCO2
– Decreased pH
– Decreased PaCO2
 Bedside Spirometry Results
– Negative inspiratory force (NIF) – < -20 cmH2O
– Spontaneous tidal volume – < 5 mL/kg IBW
– Vital capacity – < 10 mL/kg IBW
Evaluation of Ventilation – Determine
Cause of Problem
 Hypoventilation
– Inadequate alveolar ventilation –
A
= (VT – VDS) (f)
– Increase in physiologic dead space –
VD/VT = (PaCO2 – PECO2)/PaCO2
Evaluation of Ventilation – Determine
Cause of Problem
 Increase in Carbon Dioxide Production
– Stress
– Shivering
– Pain
– Asynchrony with ventilator
– High carbohydrate diet
Evaluation of Ventilation – Determine
Cause of Problem
Change in Lung and Chest Mechanics
– Compliance – C = ∆V/∆P
• ∆V = VT Corrected for Tubing Compliance
• ∆P = Pplat – PEEP
Causes of decreased lung compliance
– Atelectasis
– Pulmonary edema
– ALI/ARDS
– Pneumothorax
– Fibrosis
Evaluation of Ventilation – Determine
Cause of Problem
 Causes of decreased thoracic compliance
– Obesity
– Pleural effusion
– Ascites
– Chest wall deformity
– Pregnancy
Evaluation of Ventilation – Determine
Cause of Problem
Cause of increased lung compliance
• COPD
Evaluation of Ventilation – Determine
Cause of Problem
 Causes of increased thoracic compliance
– Flail chest
– Loss of chest wall integrity
– Change in patient position
Evaluation of Ventilation – Determine
Cause of Problem
 Change in Lung and Chest Mechanics
– Airway Resistance – RAW = ∆P/∆
• ∆P = (Ppeak – Pplat)
• ∆ = flow
Evaluation of Ventilation – Determine
Cause of Problem
 Causes of increased resistance
– Bronchospasm
– Mucosal edema
– Secretions
– Excessively high rate of gas flow
– Small endotracheal tube
– Obstruction of endotracheal tube
– Obstruction of the airway
Evaluation of Ventilation – Determine
Cause of Problem
 Causes of decreased resistance
– Bronchodilator administration
– Decrease in flow of gas
– Administration of bronchial hygiene
Evaluation of Ventilation – Determine
Cause of Problem
• Loss of Muscle Strength/Neurological Input
– Rapid Shallow Breathing Index (RSBI)
• Indication of whether patients have the
ability to breathe without ventilatory
support
Evaluation of Ventilation – Determine
Cause of Problem
 Loss of Muscle Strength/Neurological Input
– Rapid Shallow Breathing Index (RSBI)
• f/VT
– If < 100 breaths/min/L, patient has ability to
breathe without ventilator
– If > 100 breaths/min/L, patient will likely not
be able to sustain spontaneous breathing
– Maximal inspiratory pressure
– Maximum voluntary ventilation
Evaluation of Ventilation –
Management Options
Increase Alveolar Ventilation
– Increase in Mechanical Tidal Volume
• Normal Volume – 6 to 12 mL/kg IBW
• Most direct way to change alveolar ventilation
• Should normally not exceed 12 to 15 mL/kg IBW
• Associated with increase in peak inspiratory pressure
which has increased risk of trauma to lung
Evaluation of Ventilation –
Management Options
– Increase in spontaneous ventilation
• More advantageous to patient than increasing
mechanical tidal volume
• Augmentation by pressure support mode helps
overcome resistance of ventilator circuit and
artificial airway
Evaluation of Ventilation –
Management Options
 Increase Alveolar Ventilation
– Increase in Mechanical Rate
• Normal Value – 12 to 18 Breaths per Minute
• Should Normally not Exceed 20 Breaths per Minute
• Prediction of Desired Rate
New rate =
Evaluation of Ventilation –
Management Options
 Decrease Carbon Dioxide Output (Production)
– Medicate patient to relieve pain, stress, and prevent
asynchrony, decreasing work of breathing
– Maintain patient’s temperature within normal range
– Provide appropriate nutrition
Evaluation of Ventilation –
Management Options
 Treat Underlying Pulmonary Pathophysiology
 Maintain airway in patent state
– Prevent accumulation of secretions in airway
– Use properly sized artificial airway
– Prevent occlusion of airway by patient; use
bite block
Considerations in Management –
Permissive Hypercapnea
 Allowing PaCO2 level to remain elevated above
45 mmHg
• Purpose
– Maintain plateau pressure at an acceptable level (<
30 cm H2O) by decreasing tidal volume to less than
6 mL/kg and increasing respiratory rate, thereby
minimizing trauma and cardiovascular side effects
Considerations in Management –
Permissive Hypercapnea
 Method
– Decrease tidal volume and increase respiratory
rate, while maintaining minute volume
– If PaCO2 increases and pH decreases, either permit
normal metabolic compensation or administer
medications to maintain level at 7.25 to 7.35
– Institute gradually to allow PaCO2 to increase
gradually over hours or days
Considerations in Management –
Permissive Hypercapnea
 Relative Contraindications or Cautions
–
–
–
–
–
–
–
Presence of cardiac ischemia
Presence of pulmonary hypertension
Compromised left ventricular function
Right heart failure
Head trauma
Intracranial disease
Metabolic acidosis
Considerations in Management –
Permissive Hypercapnea
 Absolute Contraindication
– Intracranial lesions
Considerations in Management –
Creation of Intrinsic PEEP
 Intrinsic PEEP
– Alveolar pressure above the applied PEEP at the
end of exhalation
Considerations in Management –
Creation of Intrinsic PEEP
 Contributing factors
• Pressure support ventilation
• Airway obstruction
• Rapid respiratory rate
• Insufficient flow rate
• Relatively equal I:E ratio
• High minute volume
• History of air trapping
Considerations in Management –
Creation of Intrinsic PEEP
 Problems associated with intrinsic PEEP
– Increase in work of breathing – patient must
overcome PEEP in order to trigger breaths
– Underestimation of mean airway pressure
– Increase in hemodynamic side effects
– Increase in volutrauma
Considerations in Management –
Creation of Intrinsic PEEP
 Determination of Intrinsic PEEP
– Esophageal balloon
– End-expiratory hold by ventilator
Considerations in Management –
Creation of Intrinsic PEEP
 Correction or Reduction of Intrinsic PEEP
– Improve ventilation and reduce air trapping
by use of bronchodilators
– Prolong expiratory time by increasing flow or
reducing tidal volume or frequency
Considerations in Management –
Inverse Ratio Ventilation (IRV)
IRV - Mode of ventilation in which the
inspiratory time is longer than the expiratory
time
 Purpose
– Treatment of patients with refractory
hypoxemia not responsive to conventional
modes of mechanical ventilation
Considerations in Management –
Inverse Ratio Ventilation (IRV)
 Physiology
– Overcome non-compliant lung tissue
– Recruitment of collapsed alveoli
– Increase in time for diffusion of oxygen across
the alveolar-capillary membrane
– Increase in mean airway pressure
Considerations in Management –
Inverse Ratio Ventilation (IRV)
 Method
– Decrease inspiratory flow
– Increase in inflation hold time
– In APRV mode, can be created when
pressure release rate is less than 20/minute
Considerations in Management –
Inverse Ratio Ventilation (IRV)
 Because of the increase in mean airway pressure,
there is an increased potential for hemodynamic
side effects; these are usually limited during acute
administration because the pressure is not
communicated to the cardiovascular system
Considerations in Management –
Extracorporeal Membrane Oxygenation
(ECMO)
 Modified form of cardiopulmonary bypass
used to provide relatively long-term support
for the function of oxygenation of the tissue
using an extracorporeal machine capable of
gas exchange
Considerations in Management –
Extracorporeal Membrane Oxygenation
(ECMO)
 Purpose
– Intrinsic recovery of the lungs
– Support gas exchange
– Provide adequate tissue perfusion
– Support cardiac function
Considerations in Management –
Extracorporeal Membrane Oxygenation
(ECMO)
 Indications
– Failure of advanced ventilator strategies
– Oxygen Index (OI) greater than 40 –
OI = (Mean Airway Pressure x FIO2 x100)/PaO2
– Acute deterioration
Considerations in Management –
Extracorporeal Membrane Oxygenation
(ECMO)
 Technique
– A cannula is inserted into the right atrium via
the right jugular vein
– Blood is withdrawn through the cannula
– The blood passes through a membrane
oxygenator where oxygen and carbon dioxide
are exchanged
– The blood is then warmed and reinfused into
the right common carotid artery
Considerations in Management –
High Frequency Ventilation (HFV)
 High Frequency Positive Pressure
Ventilation (HFPPV)
– Mode of ventilation in which a conventional
ventilator delivers a rapid rate at a low tidal
volume
Technique:
• Respiratory rate is set at minimum of 60
breaths per minute
• Tidal volume is set at less than 5 mL/kg IBW
Considerations in Management –
High Frequency Ventilation (HFV)
 High Frequency Jet Ventilation (HFJV)
– Mode of ventilation in which a pulse of high
velocity blended gas is introduced through a side
port of the endotracheal tube
– Conventional ventilator provides PEEP and
intermittent breaths
– Rate of jet pulses set between 60 and 600 breaths
per minute
– Inspiratory time of jet is 20 to 40 milliseconds
Considerations in Management –
High Frequency Ventilation (HFV)
 High Frequency Oscillatory Ventilation (HFOV)
– Mode of ventilation in which 180 to 3000 pulses
per minute are delivered to the airway
Technique
• Ventilator frequency is set usually between 5 and
6 Hz; the lower the hertz (Frequency), the higher
the tidal volume
• Flow is continuous at 15 to 20 Lpm
• Inspiratory time is set at 33%
Considerations in Management –
High Frequency Ventilation (HFV)
 High Frequency Oscillatory Ventilation
• Lung volume is determined by observing chest
“wiggle” (visible vibration from shoulder to midthigh area)
• Mean airway pressure should start at
5 cm H2O above the mean airway pressure
observed during conventional ventilation
• Chest X-ray should be done within four hours
of initiation of HFOV to evaluate lung volume
• No breaths are delivered at conventional
volumes
Considerations in Management –
High Frequency Ventilation (HFV)
Comparison of High Frequency Techniques
HFPPV
HFJV
HFOV
Expiration
Passive
Passive
Active
Pressure
Waveform
Variable
Triangular
Sine
> Dead Space < Dead Space < Dead Space
Ventilation
Ventilation
Ventilation
180 –
Frequency 60 – 150/min 60 – 600/min
3000/min
Tidal
Volume
Considerations in Management –
High Frequency Ventilation (HFV)
 Advantages of HFV
– Lung protection – limits overdistention of alveoli by
means of smaller volumes and lower peak
inspiratory pressures; decrease in barotrauma
– Decrease in complications including compromised
cardiac output and increased intracranial pressure
– Increases mean airway pressure; improves alveolar
recruitment with PEEP, both set and intrinsic
– Improved gas exchange; improvement in
ventilation/perfusion matching from rapid flow
pattern
Considerations in Management –
High Frequency Ventilation (HFV)
 Contraindications and Hazards
– No absolute contraindications
– Relative contraindication or caution
• Chronic obstructive lung disease
• Non-homogenous
Hazards
•
•
•
•
•
Air trapping
Inadequate humidification
Tracheal injury from high flow velocity
Inadequate monitoring
lung disease
Hemodynamic Monitoring – Arterial
Blood Pressure Monitoring
 Assessment of overall cardiovascular tone and
dependability of oxygen delivery
Normal Value
– Systolic – 100 to 140 mmHg
– Diastolic – 60 to 95 mmHg; many
cardiologists are now stating that the
diastolic should be maintained no higher
than 80 mmHg
Hemodynamic Monitoring –
Catheterization
 Arterial Catheter
– Site of Insertion
•
•
•
•
Radial artery (preferred)
Brachial
Femoral
Dorsalis pedis
– Site of Placement
• In systemic artery in proximity of insertion site
– Purpose
• Measurement of systemic arterial pressure
• Source of sample for arterial blood gases
Hemodynamic Monitoring –
Catheterization
 Central Venous Catheter
– Site of insertion
• Subclavian
• Internal jugular vein
– Site of placement
• Superior vena cava or in or near right atrium
– Purpose
• Measurement of central venous pressure
• Administration of fluid and/or medication
Hemodynamic Monitoring –
Catheterization
 Pulmonary Artery Catheter (Swan-Ganz or FlowDirected Catheter)
– Site of insertion
• Subclavian
• Internal jugular vein
– Site of Placement
• Branch of pulmonary artery
– Purpose
• Measurement of CVP, PAP, and PCWP
• Collection of mixed venous blood gas samples
• Monitoring of mixed venous oxygen saturation
• Measurement of cardiac output
• Provision of cardiac pacing
Hemodynamic Monitoring – Values
Monitored
Value
Arterial Blood
Pressure
MAP– Mean Arterial
Blood Pressure
ECG –
Electrocardiogram
Normal Range
90-140/60-90
mmHg
80 – 100 mmHg
Abnormal Value
> 140/90 – Hypertension
< 90/60 - Hypotension
> 100 mmHg – Hypertension
< 80 mmHg - Hypotension
PR interval > 0.2 sec.,
Tachycardia, Bradycardia, First-,
Second- , and Third-Degree
Heart Block, Premature
Normal Heart Rate
Ventricular Contractions,
and Rhythm
Atrial Fibrillation, Atrial
Flutter, Elevated S-T Segment,
Inverted T Wave, Ventricular
Tachycardia, Ventricular
Fibrillation, Asystole
Hemodynamic Monitoring – Values
Monitored
Value
CVP – Central
Venous
Pressure
PAP –
Pulmonary
Artery
Pressure
Normal
Range
Abnormal Value
2 – 6 mmHg
> 6 mmHg: Fluid Overload, Right Ventricular
Failure, Pulmonary Hypertension, Valvular
Stenosis, Pulmonary Embolism, Cardiac
Tamponade, Pneumothorax, Positive
Pressure Ventilation, PEEP, Left Ventricular
Failure
< 2 mmHg: Hypovolemia, Blood Loss, Shock,
Peripheral Vasodilation, Cardiovascular
Collapse
20-35/5-15
mmHg
> 35/15 mmHg: Pulmonary Hypertension,
Left Ventricular Failure, Fluid Overload
< 20/5 mmHg: Pulmonary Hypotension,
Hypovolemia, Cardiovascular Collapse
Hemodynamic Monitoring – Values
Monitored
Value
– Mean
Arterial
Pressure
PCWP –
Pulmonary
Capillary
Wedge
Pressure
Normal
Range
Abnormal Value
10 – 20 mmHg
> 20 mmHg: Same as ↑ PAP
< 10 mmHg: Same as ↓ PAP
5 – 10 mmHg
(< 18 mmHg)
> 18 mmHg:
Overload
> 20 mmHg:
> 25 mmHg:
> 30 mmHg:
Left Ventricular Failure, Fluid
Interstitial Edema
Alveolar Filling
Frank Pulmonary Edema
Hemodynamic Monitoring – Values
Monitored
Value
Normal Range
CO –
Cardiac
Output
4 – 8 L/min
CI – Cardiac
Index
2.5 – 4 L/min/m2
Abnormal Value
> 8 L/min: Elevated
< 4 L/min: Decreased
> 4 L/min/m2: Elevated due to Stress, Sepsis,
Shock, Fever, Hypervolemia, or Medications
< 2.5 L/min/m2: Decreased due to Left
Ventricular Failure, Myocardial Infarction,
Pulmonary Embolus, High Levels of PPV,
PEEP, Blood Loss, Pneumothorax,
Hypovolemia
Hemodynamic Monitoring – Values
Monitored
Value
SVR –
Systemic
Vascular
Resistance
PVR –
Pulmonary
Vascular
Resistance
Normal Range
900 – 1400
Dynes-Sec/cm5
(11.25 – 17.5
mmHg/L/min
Abnormal Value
> 1400 Dynes-sec/cm5: Increased due to
Vasoconstrictors, Late Septic Shock,
Hypovolemia
< 900 Dynes-sec/cm5: Decreased due to
Vasodilators, Early Septic Shock
> 250 Dynes-sec/cm5: ↓pH, ↑PCO2,
110 – 250 DynesVasopressors, Emboli, Hypoxemia,
sec/cm5
Emphysema, Interstitial Fibrosis, Pneumo1.38 – 3.13
thorax
mmHg/L/min
< 110 Dynes-sec/cm5: Pulmonary Vasodilators,
Nitric Oxide, Oxygen, Calcium Blockers
The End
Considerations in Management –
Open Lung Ventilation
• Purpose - optimize lung mechanics and
minimize phasic damage by placing PEEP
above Pflex
• Pflex is the point on the pressure-volume
curve below which the alveoli begin to
collapse during exhalation
Considerations in Management –
Open Lung Ventilation
• Rationale
– Reinflation of atelectatic alveoli on a breath-bybreath basis increases lung injury
– Determination of the Pflex on the pressure-volume
curve signifies the pressure at which alveolar
collapse occurs
– PEEP is applied just above the Pflex level
Considerations in Management –
Open Lung Ventilation
• Rationale
– This is a higher than conventional level of PEEP
allowing use of a lower tidal volume
– Respiratory rate is increased incrementally to
maintain an acceptable PaCO2, at times as high
as 35 breaths per minute