10/2/2015
When
Ventilation Fails
John Maher, MD
How to Optimize Success
of Ventilation Strategies
Conflict of Interest Disclosure
• The planners/committee members and speakers for this CME activity have no
relevant financial relationships with commercial interests to disclose.
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10/2/2015
• Recognizing Lung Pathology
• Gas Exchange Derangements
• Tools
• Management Issues
• When Strategies Fail
Content
Recognizing Lung Pathology
• Types of lung disease in children
• Restrictive lung disease
• Obstructive lung disease
• Time constant
Types of Lung
Disease in Children
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RDS
• Restrictive Lung Disease?
• Obstructive Lung Disease?
RESTRICTIVE LUNG DISEASE
• Abnormal Airway Resistance?
• Abnormal Lung Compliance?
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DECREASED LUNG COMPLIANCE
C=ΔV/ΔP
P-V
LOOPS
Diagnosis?
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OBSTRUCTIVE LUNG DISEASE
• High Airway Resistance
• R = Δ P / Flow
FLOWVOLUME
LOOPS
TIME CONSTANT
T.C. = C X R
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Time Constant
• T.C. = C X R
= Δ V / Δ P X Δ P / Flow
= ml / cm H20 X cm H20 / ml t -1
= 1 / t-1
=t
Time Constants
• Restrictive Lung Disease
• Obstructive Lung Disease
• T.C. = c X R = small #
• T.C. = C X
• Short time constant
• Long time constant
R
= large #
Time Constant vs. Air Exchange
• Individual time constant for any lung unit
• Takes 4 – 5 time constants to move about 96% of gas in & out of any lung unit
• Restrictive lung disease = short respiratory cycles for gas exchange
• Obstructive lung disease = long respiratory cycles for gas exchange
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Two Lung Functions
1) Ventilation
2) Oxygenation
Where Does Gas
Exchange Occur?
LUNG VOLUME TRACING
*→
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AIR TRAPPING
In Lung Pathology FRC = EEV
E
E
V
V/Q Matching
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INTERPRETING ABG
Lung’s Role in Acid-Base Disburbances
ABG
ABG
pH / PaCO2 / PaO2 / HCO3
7.25 /
/
/?
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ABG
ABG
ABG
Acidemia
7.50 /
/
/?
Alkalemia
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ABG
7.24 / 40 / 85 / 16 ?
ABG
Metabolic Acidosis
ABG
7.24 / 58 / 80 / 24
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ABG
Respiratory Acidosis
ABG
7.55 / 25 / 80 / 24 ?
ABG
Respiratory Alkalosis
(Hyperventilation)
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ABG
ABG
ABG
7.50 / 40 / 80 / 32 ?
Metabolic Alkalosis
(Usually iatrogenic)
7.30 / 58 / 80 / 32 ?
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ABG
Acidemic
Respiratory Acidosis
Metabolic Alkalosis
TOOLS
Tools
• Respiratory Mechanics
• Non-invasive monitors
• Supplemental Gas Therapies
• CXR
• Modes of Ventilation
• Patient positioning
• Sedation
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RESPIRATORY MECHANICS
Ventilator Graphics
• Dynamic lung compliance
- Pressure / Volume Loop
• Airway resistance
- Flow / Volume Loop
DYNAMIC LUNG COMPLIANCE
• Compliance = D volume / D pressure
• Pressure / Volume Loop:
- vertical axis = tidal volume
- horizontal axis = airway pressure
PRESSURE/VOLUME LOOP
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ALVEOLAR COLLAPSE
OVERDISTENSION
SLOPE COMPLIANCE CURVE
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AIR LEAK
VOLUME
PRESSURE
FLOW / VOLUME LOOP
• Evaluate inspiratory and expiratory flow patterns
• Detect increased inspiratory or expiratory resistance
• Determine efficacy of intervention
FLOW/VOLUME LOOP
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AIRWAY OBSTRUCTION
AIR LEAK
FLOW
VOLUME
Non-Invasive
Monitors
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Non-Invasive Monitors
• Pulse oximetry
• Capnography
• Transcutaneous C02 monitoring
PULSE OXIMETRY
HISTORY
• Technology existed since 1930’s
• Widely available clinically since mid 1980’s
- microprocessor technology
- light-emitting diodes
- plethysmography
- spectrophotometry
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LIMITATIONS
• Dyshemoglobinemias
• Dyes and pigments
• Low perfusion
• Optical interference and optical shunt
• Motion artifact
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CAPNOGRAPHY
End-Tidal CO2
SCIENCE
• Mass spectrometry – impractical clinically
• Infrared spectroscopy
INFRARED SPECTROSCOPY
• Infrared light source
• Gas chamber
• Detector
• Each gas unique absorption characteristics
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ETCO2
MONITOR
EtCO2
• Peak CO 2 during expiration
• Dependent on pulmonary capillary flow
• Need adequate right and left heart function
• Normal ETCO 2 < 5mm Hg lower than PaCO 2
• Delta between EtC02 : PaC02 will not change significantly in 24 hrs from
fluctuating alveolar function!
• Only one clinical scenario where delta changes dramatically
CASE SCENARIO
• Infant s/p cardiac surgery
• Unable to ventilate despite hand-bagging
• “ETC02 is broken” “It does not correlate”
• SITUATION CRITICAL
• Patient will arrest unless immediate change in management occurs
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CASE DATA
• Initial: PaCO2 45, ETCO 2 40, BP 70/35
• ½ hr.: PaCO2 55, ETCO 2 35, BP 62/30
• 1 hr. : PaCO2 70, ETCO 2 32, BP 55/28
• Patient taken off ventilator, hand-bagged
INTERVENTION
• Increase ventilatory support
- WRONG
• Volume expander / inotrope
- CORRECT
DIAGNOSIS
• Increase shunt perfusion
- WRONG
• Increase deadspace ventilation
- CORRECT
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V/Q MATCHING
Shunt Perfusion
Zero
Low V/Q
Normal
Deadspace Ventilation
V/Q ~ 0.8
High V/Q
Infinity
PRACTICAL USES OF ETCO2
• Adequacy of alveolar ventilation
• Monitor spontaneous respirations
• Help assess patient-ventilator synchrony
• ETT patency
• ETT placement
• Adequacy of CPR
CPR and ETCO2
• Constant relationship between ETCO 2 and coronary perfusion2
• Must maintain coronary PP at
30 mm Hg
• If ETCO 2 does not rise > 10 mm Hg, not likely CPR successful3
2Gudipati C, Weil M, Bisera J, et al. Expired carbon dioxide: a noninvasive monitor of
cardiopulmonary resuscitation. Circulation 1988;77:237
3Weil M,
Bisera J, Trevino R, Rackow E. Cardiac output and ETCO 2. Crit Care
Med 1985;13:907.
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Transcutaneous C02
Monitoring
Transcutaneous C02
C02
Transcutaneous C02
• Very close correlation to PaC02
• Correlation close in in adults as well.
A. Nicolini, M. Ferrari; Ann Thorac Med. 2011 Oct-Dec;
6(4): 217–220
• Advantage continuous estimate adequacy of ventilation
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Supplemental Gas
Therapies
Supplemental Gas
• N2 / C02
• Oxygen
• Helium
• iNO
N2 / 02
• Cardiac patients – increase PVR
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Oxygen
• Aerobic support
Helium
Helium
• Mostly in conjunction with NIV
• Decreases WOB in UAO
• Only effective if < 30% Fi02 requirement
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iNO
Balanced V/Q
Dead Space
Ventilation
iNO Target
CXR
• ETT position
• Early warning
• Lung volumes!!
Modes of Ventilation
• NIV / negative pressure ventilation
• Conventional positive pressure ventilation
• High frequency ventilation
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Prone Positioning
SEDATION
• WORK OF BREATHING
• Metabolic cost of labored breathing in child much more significant in child vs.
adult
• Therefore, sedation a/o paralysis more often indicated in pediatric patient on the
ventilator
Bedside Lung Recruitment
RespCare. Oct 2014; vol 59 Issue 10, poF18,
59(10): pOF 18
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Lung Lavage 1
Lung Lavage 2
Lung Lavage 3
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Lung Lavage 4
Albuterol Toxicity
• Pediatric Critical Care Medicine:
• November 2014 - Volume 15 - Issue 9 - p e389–e392
• Online Brief Report
• Increase in Oxygen Consumption After Albuterol Inhalation in Ventilated Infants and Children
• Ross, Patrick A. MD; Newth, Christopher J. L. MD, FRCPC; Hugen, Cindy A. C. MD; Maher, John K.
MD; Deakers, Timothy W. MD, PhD
• Abstract
• Objective: To determine if inhaled albuterol (salbutamol) increases oxygen consumption (V′O 2) in
children and, if so, the duration of this effect.
• Conclusion: There is a large increase in V′O2 after albuterol inhalation. This effect lasts up to 3 hours.
• ©2014The Society of Critical Care Medicine and the World Federation of Pediatric Intensive and Critical
Care Societies
Respiratory Failure Management
• Strategies
• Obstructive lung disease
• Restrictive lung disease
• Pulmonary hypertension
• High frequency ventilation
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Goals on Ventilator
• Ventilation
• Oxygenation
Ventilation
• Increase ventilator rate
• Increase PIP – delta P
• Lengthen IT
• Increase Vt
Oxygenation
• Increase Fi02
• MawP
• Optimal PEEP
• Longer IT
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Obstructive Lung Disease
• Avoid intubation
• Attempt NIV
• If intubate – deflate chest
• Higher pressures, low rate, long ET (long time constant)
• Pure obstructive lung disease – never HFV!
STRATEGIES IN RLD MANAGEMENT
• Low Vt – 4 – 6 ml /kg
• Limit plateau pressure
• Minimize Fi02 (Pa02 60 – 80 mmHg)
• Optimal PEEP
• Permissive hypercapnea
• HFV – short time constant
• Longer I time; inverse I : E ratio
STRATEGIES IN RLD MANAGEMENT
• PC SIMV (PRVC will switch to same mode – optimal flow pattern delivery)
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Pulmonary Hypertension
• iNO
• HFV
• PPHN – exogenous surfactant
ARDS / iNO
• Not indicated
• Small percentage responders
• Minimal response – short duration
• Responders – heterogeneous disease
• Tachyphylaxis!
• Desperate use to avoid ECMO
Actual Case – Tracheomalacia / Bronchiolitis
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Flow-Volume Loop
Adjusted Distending Pressure
F/U CXR with Recruitment - Hyperinflation
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When Strategies Fail
• What is failure?
• ECMO
What is Failure?
• Permissive hypercarbia
• Permissive hypoxia
• Non-viable hypoxia – OI, P/F
ECMO
• V-V if adequate hemodynamic status
• V-A cardiac insufficiency
• Reversible lung injury!
• Optimal transition within 10 days of aggressive ventilator support
• Newborn concerns – obstructed TAPVR, ACD
• Poor outcomes pertussis, adenovirus
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ECMO Circuit
Infantile Pertussis Pneumonia
Pertussis Pneumonia
Normal Lung
ELSO Registry
• 1992 – 2009; Case fatality rate infant pertussis = 69.8%; < 6 wks age = 83.6%
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PEDIATRICS®
• Impact of Rapid Leukodepletion on the Outcome of
Severe Clinical Pertussis in Young Infants. (H. E. Rowlands,
MBBSa, A.P. Goldman,MBBChBa , et al. Pediatrics. October 1, 2010; 126(4): 816 -827).
Decision Algorithm from Study
Study Results
• 2001–2004 predicted survival (4.4 [49%] of 9.0); equivalent to observed mortality
(4.0 [44%] of 9.0).
• 2005 - 2009 observed mortality (1.0 [10%] of 10.0); significantly better than
predicted (4.7 [47%] of 10.0).
• Flaws – single center, low numbers, not randomized
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CONCLUSION
• Practice makes perfect – Use your skills
• Freedom of thought, not action – Challenge the team with your thoughts
• Thought leads to discourse;
• Discourse leads to attention to detail;
• Attention to Detail always leads to BETTER OUTCOME!
• Vigilance in monitoring / observation (not complacency) is “doing something for your child!”
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