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What are the muscles for inspiration and expiration and how do they function?
- Inspiration - Diaphragm (skeletal muscle), external intercostals, and accessory muscles of inspiration
- Expiration - muscles of the abdominal wall (rectus abdominus, internal and external obliques and transverse abdominus); Internal intercostal muscles
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How does the diaphragm move during inspiration and exhalation?
- On inspiration - diaphragm contracts and moves down
- On exhalation - diaphragm relaxes and moves up
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How does the anatomy of the thoracic cage, ribcage respond to contraction of muscles during inspiration and expiration?
- Inhalation - scalenes elevate the first 2 ribs and sternomastoids raise the sternum
- Expiration - internal intercostal muscles pull the ribs downward and inward (opposite the external intercostal muscles) decreasing the thoracic volume and allowing air to flow outward
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Why is expiration passive during "quiet" breathing?
- During inspiration it actively contracts and for expiration it just relaxes
- Active when exercising
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What are the elastic properties of the lung and chest wall?
- Can automatically recoil
- Wants to collapse
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What is alveolar pressure?
Pressure inside the thoracic cavity (essentially pressure inside the lungs)
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What is intrapleural pressure?
- Pressure w/in the pleural sac
- Less than intra-thoracic pressure
- Pressure exerted outside the lungs w/in the thoracic cavity, usually less than atmospheric pressure at 756 mmHg
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What is transpulmonary/transmural pressure?
Difference between the pressure of the respired gas at the mouth and the pleural pressure around the lung
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What are the changes for intrapleural pressure, alveolar pressure, airflow, and lung volume during the breathing cycle?
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What are the consequences of dynamic compression of the airways during expiration?
Won't be able to fill the lungs with air
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What is compliance? And what is compliance of the lung and chest wall?
- Look at Δ in volume w/ Δ in pressure
- Represents elasticity of the lungs
- High Compliance - large increase in lung volume for small decrease in ip pressure
- Low Compliance - small increase in lung volume for large increase in ip pressure
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What 2 factors does compliance depend on?
- Distensibility
- Surface tension of the alveoli
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Under what conditions is the compliance of the lung increased or decreased?
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How does Emphysema/ COPD alter the lungs mechanical properties? Are they restrictive or obstructive diseases?
- Loss of elastic fibers = ↑ lung compliance = ↑ (steeper) slope of the volume-vs.-pressure curve for the lung
- At a given volume, the collapsing (elastic recoil) force on the lungs is ↓
- Breathes at higher lung volumes
- Barrel shaped chest
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How does Chronic bronchitis/ COPD alter the lungs mechanical properties? Are they restrictive or obstructive diseases?
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How does Asthma alter the lungs mechanical properties? Are they restrictive or obstructive diseases?
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How does Pulmonary fibrosis alter the lungs mechanical properties? Are they restrictive or obstructive diseases?
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What is the role of surfactant in lung mechanics?
Reduces surface tension and the collapsing pressure for a given radius
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What secretes surfactant?
Type II alveolar cells
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What is the difference between minute ventilation (VE) and alveolar ventilation (VA) and how are each calculated?
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What is the difference between alveolar and physiological dead space?
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How does rate and depth of breathing specifically alter alveolar ventilation?
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What is the relationship between alveolar ventilation and alveolar levels of CO2 and O2?
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What are the steps involved in respiration, gas laws, and how the lung is supported and moved?
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Compare and contrast the efficiency of the apex and base of the lung in regard to ventilation, blood supply?
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What is airway resistance and what factors play a role in changing it?
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What is ventilation-perfusion mismatch and how does it relate to disease states?
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What are the physical factors controlling gas diffusion?
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Quantify the pressure gradients driving the O2/CO2 exchange in both lung and tissues
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Define (Va/Q) ventilation/ perfusion ratio
Alveolar ventilation rate over pulmonary blood flow
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What is ventilation?
Amount of air that reaches the lungs
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What is perfusion?
Amount of blood that reaches the lungs
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How does abnormal Va/Q affect pulmonary gas exchange?
AV shunting process will occur making the underventilated area also underperfused
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What is PaO2 and PaCo2 and what are the normal values and the determinants?
- PaO2 -
- PaCO2 - Arterial carbon dioxide
- Normal: 40 mmHg
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What is A-a gradient and what does it mean and how do you calculate it?
- A - alveolar O2
- a - arterial O2
- (Age + 10)/4
- Increasing A-a gradient = hyoxemia
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What does a normal A-a gradient mean?
- No diffusion defect
- No V/Q mismatch
- No right to left shunting
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What does ventilation/ perfusion vary from the apex to the base of the lung?
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What Pulmonary Disorders increase the V/Q ratio?
- Pulmonary emboli
- Partial or complete obstruction in the pulmonary artery or some of the arterioles (atherosclerosis, collagen disease, Marfans)
- Extrinsic pressure on the pulmonary vessels (pneumothorax, hydrothorax, presence of tumor)
- Destruction of the pulmonary vessels (emphysema)
- Decreased CO
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What Pulmonary Disorders decrease the V/Q ratio?
- Obstructive lung disorders
- Restrictive lung disorders
- Hypoventilation from any cause
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What is the respiratory quotient and what is its purpose?
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What is Alveolar PO2 in relation to inspired oxygen?
Alveolar PO2 is 5x the % of inspired oxygen
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