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(3) Respiratory (Compensatory Responses (Respiratory Effort (Airway…
(3) Respiratory
Compensatory Responses
pH Change
- Blood slightly alkaline (7.35 - 7.45)
- Respiratory (Alkalosis/Acidosis): Lung remove
- Metabolic (Alkalosis/Acidosis):
High Altitude
- Low PO2, Increased ventilation
- Increased 2,3DPG
- Increased Erythropoietin (Kidney)
- Secondary polycythemia
Exercise
- Increased PCO2, H+
- Increased ventilation
- Normal parameters
- In a state of reduced Hb affinity, H+, Temperature
Respiratory Effort
Airway Resistence
- Bronchoconstriction
- Parasympathetic
- Irritation / Cold / Dry
- Bronchodilation:
- Sympathetic
- B2 adrenegic antagonist
- Sabutamol
- Mucous accumulation
- Asthma: Treatment (B2 adrenegic agontist + Steroid)
Compliance of Chest wall & lungs (Increased respiratory effort)
- Fibrosis
- Lack surfactant + pus + fluid
- Edema
- Surfactants work to
- Reduce surface tension
- Allow more expansion
- Increase compliance
- Osteoarthritis / Kyphosis
Limitations
1) Ventilation Inadequacies
- Reduced alveolar ventilation
- Increased dead space
- Decreased TV
- Decreased BR
2) Ventilation perfusion mismatch
- Shunt
- Alveolar dead space
3) Depression of control mechanisms
- Morphine overdose
- Alcohol poisoning
- Anesthetic & Sedative
- Narctic
- Opoids
- Depresses response to incease PCO2
Clinical Application
- Be weary of patients taking opoids
- Administering LA
- Depressed respiratory system
General
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Anatomy
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6) Alveolar cells (Epithelial)
- Interstitial Space (CT, Fibroblast)
- Capillaries
- Macrophages
- Type 1
- Type 2 Produces Surfactant - protein & phospholipids
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Protection
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Lungs
- Mucous
- Cillary Escalator
- Alveolar Macrophages
- Airway reflexes (cough, sneeze)
- Artificial respiration, mucous and escalator impaired
Efficacy of Respiration
1.Ventilation
Expiration/Inspiration
Expiration
- Passive / Active (Forced)
- Relaxation / Recoil
- Decrease Volume
- Increase Pressure
Inspiration
- Active
- Contract / Expand
- Dec volume
- Inc pressure
Pressure Changes
Before:
Intra-alveolar: 760mmHg
Intra-pleural: 757mmHg (-3)
Created by lungs recoil
Suction force, prevent collapse
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Terminologies
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2) Inspiratory Reserve Volume
- Reserve outside of tidal
- Max insiration
3) Expiratory Reserve Volume
- Reserve outside of tidal
- Max expiration
4) Residual Volume
- Minimum amount of air
- Cannot exhale
- Kids have less RV
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Pathological
Tidal Volume
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Chest Wall
- Kyphosis (Muscular/Skeletal)
- Pectus Excavatum
Lungs
- Resistance to airflow (Asthma)
- Stiffness (Lung elasticity)
- Collapse
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2. Gas exchange @ Alveoli
- Air that participates in GE
Pathological
Physiological Deadspace (No blood)
- Not all inspired air undergoes Gas Exchange
- Air (Yes) Blood Perfusion (No)
- eg. Pulmonary Embolism
Shunt (Not included in Alveolar Ventilation)
- Less air encountering blood
- Air (No) Blood Perfusion (Yes)
- eg. Water in lungs, Emphesyma, Pneunomia
Tidal Volume
Chest Wall
- Kyphosis (Muscular/Skeletal)
- Pectus Excavatum
Lungs
- Resistance to airflow (Asthma)
- Stiffness (Lung elasticity)
- Collapse
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Diffusion across barrier
Partial Pressure of gases
- Calculation: Total Pressure x % gas in air
- Diffusion occurs until equilibrium
- Different gases equiliberate at different rates
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Perfusion of Lungs
- L /R Pulmonary Artery
- 4 Pulmonary Veins
Low Pressure vs Systemic Circulation
Pulmonary: 24 / 10
Systemic: 120 / 80
High Volume
- Whole cardiac output goes through
Distribution is not uniform
- Gravity: More upright more flow to bottom
- Muscular tone: Pulmonary arterioles more distensible, less muscular, (increase flow)
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Regulation
Ventilation
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PCO2 7% (Arterial)
- 23% Hb, 70% HCO3-
- Sensed by
- Medullary Chemoreceptors: PCO2 only (CNS)
- Carotid Body Chemoreceptors: PO2, PCO2, H+ (PNS)
- Aortic Body Chemoreceptor: PO2, PCO2, H+ (PNS)
- Hypercapnia: More PCO2
- Hypocapnia: Less PCO2
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Gas Exchange @ Alveoli
Gas Related
1) Difference in PP (Altitude Sickness)
2) Barrier (Edema / Fibrosis)
3) Surface Area (Shunt)
4) Diffusion property of gas (CO2 > O2)
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General
Parameters
PO2
- 100mmHg
- <60mmHg (Increase ventilation)
PCO2
- 35-45mmHg
- 45-70mmHg (Increase ventilation)
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