Flashcards in Pulmonary Physiology Deck (78):
Major functions of the pulmonary system?
-Gas exchange (O2 delivery, CO2 removal)
-Maintenance of acid base balance (CO2 is the major source of hydrogen ions in the blood).
How many lobes are in the left lung?
2, upper and lower
How many lobes are in the right lung?
3, upper, middle and lower.
What is the ventilatory capacity of the L and R lung, respectively?
What are the functions of the conducting airways?
-Warm air to body temp
-Filter air via mucus and cilia
How is ventilation distributed?
Not uniform, smooth muscle directs inhaled air to well perfused regions.
The functional unit of the lung: a respiratory bronchiole and all its associated alveolar ducts and sacs.
Describe the structure of alveoli
-Large surface area to volume ratio for gas exchange.
-Structures are not totally separated, moire like bubbles than grapes.
What are the two types of pneumocytes?
Type 1: squamous epithelium
Type 2: surfactant producers
What is the relationship between circulatory system and airways?
-Capillaries and lymphatics are closely intertwined with alveoli, allowing for very short diffusion distances.
What is the energy expenditure at rest for a healthy person?
What is the energy expenditure for a healthy person at heavy exercise intensity?
How high can energy expenditure at exercise be for individuals with a pulmonary pathology?
25%. Goal of PT: Decrease this.
T/F: Intrapleural pressure is usually negative.
True. This keeps alveoli inflated.
What is the transmural pressure?
P-alv - P ip
This is the pressure difference across the alveolar wall.
Determines alveolar size.
How does alveolar pressure change during a normal respiratory cycle?
Negative during inspiration, positive during expiration. Very small (1->2 mmHg) changes.
What is the normal intrapleural pressure and how does it change during the respiratory cycle?
-Becomes more negative (-6) during inspiration which increases their volume. Returns to -4 during expiration.
What are the main inspiratory muscles?
-Diaphragm, external intercostals.
What are the main expiratory muscles?
None, passive. Relaxed inspiratory muscles allow for expiration.
What is the role of surfactant in the alveoli?
Decreases the surface tension on the alveolar surface, requires less work to change volume of alveoli.
What does surface tension do to breathing?
Increases the work required, makes it more difficult. Inserts itself between water molecules. Lowers surface tension drastically in smaller alveoli to keep the pressures very similar across all alveoli.
What is surfactant?
An amphipathic phospholipoprotein synthesized and secreted by type II alveolar cells.
What is dynamic compression?
-during forced expiration, abs and internal intercostals contract which increases intra-abdominal and intra-thoracic pressure.
-Pip becomes positive
-As Pip approaches or exceeds airway pressure, (Palv), there is a collapse of the airways which limits expiratory flow.
What is compliance?
Stretchability. Lung tissue has a ton of this.
What is the formula for compliance?
change in volume/change in pressure
What can decrease compliance?
Scarring and fibrosis. This results in more pressure change/muscle action being needed to breathe.
What is elasticity?
The ability to recoil when stretched.
What is the formula for elasticity?
Change in pressure / change in volume
How does lung volume impact surfactant concentration?
-At high lung volume, surfactant molecules are spread out and have a low concentration, increasing surface tension. The inverse applies.
What controls pulmonary perfusion?
Bronchiolar and arteriolar smooth muscle responding to PO2 concentrations.
High PO2 leads to arteriole dilation and perfusion.
Low PO2 leads to arteriole constriction.
What is a lung capacity?
The sum of two or more lung volumes.
What is TV?
Tidal volume. Normally inhaled.
What is IRV?
Inspiratory reserve volume. Additional air that can be forcibly inhaled after a normal inhalation.
What is inspiratory capacity?
TV + IRV
What is expiratory reserve volume?
Air remaining in the lung after you normally exhale. Can be forced out.
What is the residual volume?
Air left in the lung after forcible exhale
What is the vital capacity?
ERV + TV + IRV
What is the Total lung capacity?
IRV + TV + ERV +RV
What is the functional residual capacity?
ERV + RV; buffer volume that helps maintain gas composition in alveoli.
What is a flow volume loop?
Way of visualizing pulmonary function. Flow rate on vertical axis, lung volume on horizontal axis.
What is FEV1?
Forced expiration volume in 1 sec
What should FEV1 be?
80% of FVC
What should FEV3 be?
96% of FVC.
What should FEV6 be?
Equal to FVC
What is dead space?
Volume of gas that fills airways but doesn't participate in gas exchange.
Where is anatomical dead space?
Trachea and conducting airways
Where is alveolar dead space?
Anywhere that there is ventilation without perfusion.
What is physiologic dead space?
Anatomic dead space + alveolar dead space
T/F: Inspired air is high in CO2
False. Very low. Negligible amounts 150mmhg of oxygen. (vs .2)
What is the PO2 of alveolar gas?
What is the PCO2 of alveolar gas?
Why is gas exchange effective at capillaries and alveoli?
Large surface area, small diffusion distance, presence of diffusion gradients
What is the composition of veinous blood in pulmonary capillaries?
46 mmHg PCO2
What is the composition of blood in pulmonary veins?
What impacts gas exchange at lungs?
What is the ideal ventilation perfusion ratio?
T/F: Most oxygen is bound to hemoglobin while little is free and dissolved.
What determines whether oxygen is bound or not?
If O2 is readily available, it is likely to be bound. If O2 conc is low, it binds loosely and can dissolve.
What is the PO2 and HG concentration in arterial blood?
What is the PO2 and HG conc in veinous blood?
What causes hemoglobin to give up O2 more readily (shift curve right)?
-Increases in PCO2
-Increased H+ conc
-Increased 2,3-DPG conc.
What causes hemoglobin to be less likely to give up O2? (shift curve left)?
-Decreased H+ conc
-Decreased 2,3-DPG conc.
How does anemia impact blood-oxygen?
-Decreases the amount of hemoglobin available to carry O2 , so overall carrying content and concentration drops, but not saturation.
How does the majority of CO2 travel?
-90% as bicarbonate ions in blood.
-Metabolically, 60% as bicarbonate in blood, 30% bound to hemoglobin, 10% dissolved.
What buffers hydrogen ions in veinous blood?
Hemoglobin (deoxy>oxy) carries HCO3. Releases H+
What controls the normal breathing rate?
Brainstem, has 4 centers:
-Dorsal Respiratory Group
-Ventral respiratory group
What often impacts the four breathing centers in the brainstem?
-Meds. DRG is particularly easily influenced.
What do lung receptors impact ant how?
Impact the DRG neurons.
-Irritant receptors: limits inspiration of irritant molecules.
-Juxtacappilary centers: sensitive to congestion as a result of fluid accumulation.
What is the Hering-Breuer reflex?
Stretch during large inspiration inhibits DRG, resulting in loss of inspiration ability.
How is ventilation chemically modulated?
Peripheral chemoreceptors in the aortic and carotid bodies.
-Sensitive to PO2, PCO2, pH
What is the negative feedback loop for the chemical modulation of ventilation?
-PO2 decreases, PCO2 increases, pH decreases
-Chemoreceptors stimulate respiratory centers to increase rate and depth of respiration
Where are central chemoreceptors and how do they work?
-Located near respiratory centers in brainstem.
-Respond only to arterial CO2.
-CO2 crosses blood-brain barrier, decreasing pH of CSF.
-Breathing rate increases and deepens. Raises pH.
What triggers an increased breathing rate in exercise?
-Increased arterial CO2
-Decreased pH in plasma
-Muscle and joint afferents.
What occurs up until the lactic threshold?
-Linear relationship between intensity of exercise and ventilation
-PCO2 and pH remain constant
What happens after the lactic threshold?
What is Cheyenne-Stokes breathing?
-Occurs in CNS damage, heart failure.
-Apnea followed by increasing and then decreasing respiratory pattern
What is apneustic breathing?
-Occurs with brainstem damage
-deep sigs due to excessive DRG damage