basic cardiopulmonary interactionsbasic cardiopulmonary interactions • o 2 uptake and co 2...
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Basic Cardiopulmonary Interactions
Melvin C. Almodovar MD
Divisions of Pediatric Cardiology and Pediatric Critical Care
Children’s Heart Center
University of Miami Miller School of Medicine/Holtz Children’s Hospital
PCICS Preconference: Simulation and Cardiopulmonary Interactions, December 13, 2018
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No Disclosures
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Cardiopulmonary interactions
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Overview of heart-lung interactions
• Individual structural & dynamic properties
• Anatomically & physiologically interconnected
• Occupy the same physical space, therefore mechanical interactions
• Interactions are amplified in disease
Basic Cardiopulmonary Interactions
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The ubiquitous & pervasive nature of heart-lung interactions
Basic Cardiopulmonary Interactions
Fetal life, postnatal transition
Normal, healthy activity
Critical Ilness
Cardiopulmonary Interactions
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Outline of Talk #1
• Review basic principles of respiratory function
• Review basic principles of cardiac function
• Discuss the effects of respiration on CV function under normal circumstances
– Spontaneous breathing
– Positive pressure ventilation
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Reference literature on CP interactions
Cardiopulmonary interactions in healthy children and children after simple cardiac
surgery: the effects of positive and negative pressure ventilation.
Shekerdemian LS, Bush A, Lincoln C, Shore DF, Petros AJ, Redington AN.
Heart. 1997 Dec;78(6):587-93.
Cardiovascular effects of mechanical ventilation.
Shekerdemian L, Bohn D.
Arch Dis Child. 1999 May;80(5):475-80
Cardiopulmonary Interactions.
Bronicki RA, Penny DJ, Anas NG, Fuhrman B.
Pediatr Crit Care Med. 2016 Aug;17(8 Suppl 1):S182-93.
Cardiopulmonary Interactions in Children with Heart Failure.
Bronicki RA.
Curr Cardiol Rev. 2016;12(2):104-6
Heart-lung interactions during mechanical ventilation: the basics.
Mahmood SS, Pinsky MR.
Ann Transl Med. 2018 Sep;6(18):349.
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Breathing
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Basic Cardiopulmonary Interactions
Inhalation
During inhalation (active):
• Diaphragm descends
• Rib cage expands
• The lungs expand
• The pressure in the lungs decreases (Boyle’s Law)
• Air flows into the lungs towards lower pressure
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Basic Cardiopulmonary Interactions
Exhalation
During exhalation (passive):
• Lung volume decreases
• Pressure within the lungs increases
• Air flows from the higher pressure in the lungs to the outside
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Basic Cardiopulmonary Interactions
• Pao- atmospheric pressure
• PA- airway pressure
• Ppl- pleural (intrathoracic) pressure
• PL- transpulmonarypressure= PA-Ppl
• ↑PL results in ↑VT
Negative Pressure versus Positive Pressure Breathing
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Basic Cardiopulmonary Interactions
Spirometry and lung capacity
Pulmonary function
measures:
- Volumes
- Air flow
- Diffusion capacity
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Basic Cardiopulmonary Interactions
• Lung compliance= ∆V/∆P
P- airway or alveolar pressure
• FRC- lung volume at which the lung’s recoil is balanced by the chest wall’s tendency to expand outward
Lung compliance, tidal breath, and FRC
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Basic Cardiopulmonary Interactions
• O2 uptake and CO2 elimination in the lungs
• Determined by:
– Alveolar ventilation (minute ventilation - dead space ventilation)
– Diffusing capacity across alveolar-capillary membrane
• Influenced by:
– Ventilation-perfusion matching
– Other factors (alveolar gas conc.; metabolic state, lung mechanics, etc.)
• ABG- pH/PaCO2/PaO2/HCO3-
Gas exchange
lumenlearning.com
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Basic Cardiopulmonary Interactions
Ventilation-perfusion matching
Hypoxemia Hypercarbia
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Basic Cardiopulmonary Interactions
Ventilation-perfusion matching- West zones
↑V/Q
(dead space)
↓V/Q
(shunt)
Zone I
Zone II
Zone III
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Cardiovascular function
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Systemic O2 delivery (DO2) & Cardiac output (CO)
DO2 = CO x CaO2
CO = SV x HR
• Preload• Afterload• Contractility
• Rate• Rhythm
Basic Cardiopulmonary Interactions
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Pressure-Volume relationship of the ventricle
*SV= ED volume - ES volume
• Stroke work
• Stroke volume
• Preload characteristics
• Contractility
• Afterload
• Ventriculo-vascular coupling
(Ees/Ea ratio)Pre
ssu
re
Volume
diastole
systole
EDPV pointED pressure
ED volume
ESPV point
ES volume
DBP (ES pressure)
SBP
Stroke Volume
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Pressure-volume loops: loading conditions & SV
Basic Cardiopulmonary Interactions
Preload Afterload Contractility
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Venous return and CO
Basic Cardiopulmonary Interactions
• Mean systemic venous pressure (PSV)-“pressure in the circulation if blood flow were to cease”
• VR ∞ PSV - RAp
• RAp must be less than Psv
• Influenced by:– Intrathoracic pressure
– Circulatory volume & venous capacitance
– Venous pathway obstruction (resistance)
– Right heart function
– SVR
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Basic Cardiopulmonary Interactions
Hydrodynamics and blood flow within a tube
Poiseuille’s Law
Rigid tube Collapsible tube within a
pressurized chamber
Fuhrman & Bronicki, 2016
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Venous return (VR) =PSV - PRA
RSV
PRAPsv
Thoracic
IVC
Abdominal
IVC
Diaphragm
ThoraxAbdomen
1) PIntrathoracicPABD
Effects of respiration on cardiac function
Variables influencing venous
return:
1) Intrathoracic pressure
2) Circulatory volume & venous
capacitance
3) Venous pathway obstruction
(resistance)
4) Right heart function
5) SVR
2)
3)4)
5)
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RV dysfunction and ventricular interdependence
Basic Cardiopulmonary Interactions
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• The heart sits within a confined pericardial space
• The ventricles share a septum
• A change in geometry of one ventricle affects the geometry of the other
• Diastolic & systolic interactions
• In-series & in-parallel interactions
Ventricular interdependence
Basic Cardiopulmonary Interactions
Haddad, et al
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• Myofiber arrangement within and between the ventricles; shared septum
• Contractility of one ventricle contributes that of the other
• 20-40% RVp results from LV contraction
• Subject to loading conditions; intact pericardium not requiredNaeije and Badagliacca. Cardiovasc Res. 2017
Diffusion tensor MRI
Systolic ventricular interdependence
Basic Cardiopulmonary Interactions
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Effect of respiration on
cardiovascular function
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Venous return (VR) =PSV - PRA
RSV
PRAPsv
Thoracic
IVC
Abdominal
IVC
Diaphragm
ThoraxAbdomen
Pintrathoracic (↑or↓)PABD
Effects of respiration on cardiac function
Intrathoracic (intrapleural) pressure & venous return:
• ↓ Pintrathoracic → ↓ PRA → ↑ VR
• ↑ Pintrathoracic → ↑ PRA → ↓ VR
↑ RIVC →↓ VR
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↑ intrapleural pressure
(Valsalva maneuver)
• ↑ Atrial pressures
• ↓ Venous return
• ↓ RV filling
• ↑ RV afterload (PVR)
• ↓ LV afterload
• ↓ LV wall stress
↓ intrapleural pressure
(Mueller maneuver)
• ↑ Venous return
• ↑ RV filling
• ↑ LV afterload
• ↓ LV stroke volume
• ↑ LV wall stress
• Pulmonary edema
Cardiac effects of changing intrapleural pressure
Basic Cardiopulmonary Interactions
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Basic Cardiopulmonary Interactions
Lung volume-PVR relationship
Fuhrman & Bronicki, 2016
• Mechanical effects of lung
overdistension or atelectasis
• Hypoxic vasoconstriction
• Mainly impacts the RV
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Normal circulation:
• Modest reduction in intrathoracic pressure (-1⇾ -5 cm H2O)
• Diaphragmatic descent:• Increased lung volumes
• increased intraabdominal pressure (drives venous return to the heart)
• Increased venous return (RV preload)
Increased RV stroke volume
“Respiratory pump”
Basic Cardiopulmonary Interactions
Spontaneous breathing and the right heart
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Normal LV function:
• Less impact with modest reduction in intrathoracic pressure (-1⇾ -5 cm H2O)
• However, large negative reduction (to -30 cm H2O) ⇾ acute LV dysfunction,
pulmonary edema
• Increased intrathoracic blood volume
Basic Cardiopulmonary Interactions
Spontaneous breathing and the left heart
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Effects of respiration on the left ventricle
Basic Cardiopulmonary Interactions
Airway obstruction (stridor)Normal respiration
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PEEP and oxygen delivery
Basic Cardiopulmonary Interactions
Ox
yg
en
de
live
ry (
DO
2)
Granton, Can Respir J 1996
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Positive pressure ventilation- impact on cardiac output
Basic Cardiopulmonary Interactions
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Positive pressure ventilation- loading conditions
Basic Cardiopulmonary Interactions
↑ Rap w/ ↓ VR
↑ or ↓ LAp
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Positive pressure ventilation- impact on hemodynamics
Basic Cardiopulmonary Interactions
Preload-dependent condition- VR,
PVR effects dominate
Afterload-dependent condition- LV
afterload effects dominate
Cortes-Puentes, et al. Ann Transl Med 2018
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Autonomic tone:
• ↑ lung volume → decreased HR
• ↑ lung volume → ↑ SVR
Acid-base balance:
• ↓pH, ↑pCO2 → ↑PVR
• ↓pH → ↓ myocardial dysfunction
Basic Cardiopulmonary Interactions
Heart-lung interactions
Neurologic function:
• hypoventilation → cor pulmonale
• muscular → restrictive lung dz
• PNI → atelectasis, ↓ VR (Fontan)
Renal function:
• metabolic, electrolyte disturbance
• fluid retention → CHF, restrictive
lung dz
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• Cyanotic congenital heart disease
• Intracardiac shunts (L→R; R→L)
• Outflow obstruction
• Valvar diseases
• Myocardial dysfunction; pulmonary vascular disease
Add:
• Chronic lung disease, sepsis, nutrition insufficiency,
other organ system failure
• Associated anomalies: airway, lung, chest wall, spine,
muscular, etc.
Basic Cardiopulmonary Interactions
Congenital heart diseases
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Simulation scenarios:
1. HF with ↑ LAp and altered lung compliance
2. Intracardiac shunts (R→L)
3. Single ventricle physiology
Basic Cardiopulmonary Interactions
Cardiovascular disease and respiratory function