Exercise 37B Respiratory System Mechanics: Computer Simulation Activity 1 ? Measuring Respiratory Volumes Your first experiment will establish the baseline respiratory values MRV = TV (500) x BreathsPM (15) MRV = 7500 ml/min Does expiratory reserve volume include tidal volume No, ERV is not part of tidal volume Activity 2 ? Examining the Effect of Changing Airway resistance on Respiratory volumes Obstructive problem ? expiratory flow is affected Restrictive problem ? might indicate reduced inspiratory volume FEV1 ? is the forced volume exhaled in 1 second. In obstructive disorder like chronic bronchitis and asthma, air way resistance is increased and FEV1 will be low What happened to the FEV1 (%) as the radius of the airways was decreased? It decreased because always were smaller/reduced and flow or air was redistricted Activity 3 ? Examining the Effect of Surfactant At any gas ? liquid boundary, the molecules of the liquid are attracted more strongly to each other than they are to the air molecules. This unequal attraction produces tension at the liquid surface called surface tension Surfactant increase total flow What happened to the FEV1 (%) as the radius of the airways was decreased Decreased because not as much air flow ? How has the airflow changed compared to the baseline run? Increase aprox. 40 % because surfactant releases surface tension Premature infants often have difficulty breathing. Why? Lack of surfactant Activity 4 ? Investigation Intrapleural Pressure The pressure within the flexural cavity, Intrapleural pressure, is less than the pressure within the alveoli caused by the tendency o the lung to recoil due to its elastic properties and the surface tension of the alveolar fluid (These two forces act to pull the lungs away from the thoracic wall creating a partial vacuum in the pleural cavity) Because the pressure in the Intrapleural space is lower that atmospheric pressure, any opening created in the thoracic wall equalizes the Intrapleural pressure with the atmospheric pressure by allowing air to enter the pleural cavity, a condition called pneumothorax. Which allows lunch collapse, a condition called atelectasis What happened to the lung in the left side of the bell jar? Deflated How did the pressure in the left lung differ from that in the right lung? Went to O. Right stayed the same because by opening valve Intrapleural pressure became equal to lung pressure How did the total air flow in this trial compare with that in the previous trial in which the pleural cavities were intact? Total airflow decreased by about half. Only right cavity was intact What do you think would happen if the two lungs were in a single large cavity instead of separate cavities? We would have problems because we wouldn?t have an extra lung if one collapsed Now close the valve you opened earlier, Did the deflated lung reinflate? No because you have not created pressure gradient ? you need to remove excess air from pleural cavity Why did lung function in the deflated (left) lung return to normal after you clicked reset? It had no surface tension anymore Simulation variations in Breathing Hyperventilation ? causes the lungs to breathe faster than normal Rebreathing ? small bag covers mouth Breath holding ? causes the lungs to stop respiring Normal breathing ? at any time to resume respiring Activity 5 ? Exploring various Breathing Patterns What happens to Pco2 during rapid breathing? Down, expelling air faster than your taking it in Rebreathing What happens to Pco2 during the entire time of the Rebreathing activity? Slowly climbs Did the depth of the breathing pattern change during Rebreathing? (rate and depth changes?) Rise in co2 is detected by respiration center, rate increases, depth increases, to expel extra co2 Breath Holding What happened to the Pco2 during breath holding? Increased What happened to the breathing pattern when normal respiration resume? Rate increased, depth increased Activity 6 ? Comparative Spirometry Normal Breathing What do you think is the clinical importance of the FVC and FEV1 values? To distinguish between obstructive and restrictive Why do you think the ratio of these two values is important to the clinician when diagnosing respiratory disease? Lungs unable to inflate, obstruction, restriction FEV1/FVC X 100% = 80% Emphysema breathing (obstructive) Is the FVC reduced of increased? Reduce IS the FEV1 reduced of increased? Reduce Which of these two changed more? FEV1 Explain the physiological reasons for the lung volumes and capacities that changed in the spirogram for this condition? Person is having trouble exhaling. Lung recoil decreases in emphysema and increase in airway restriction Acute Asthma Attack Breathing During acute asthma attack, bronchiole smooth muscle will spasm and thus the airways become constricted (that is, they have a reduced diameter). They also become clogged with thick mucus secretions Airways collapse and pinch closed before a forced expiration is completed Volumes and peak flow rates are significantly reduced during an asthma attack, however the elastic recoil is not diminished in an acute asthma attack Is the FVC reduced or increased? Reduced Is the REV1 reduced or increased? Reduced Which of these two changed more? FEV1 Explain the physiological reasons for the lung volumes and capacities that changed in the spirogram for this condition? Diameter so small they can?t exhale properly How is this condition similar to having emphysema? How is it different? Has higher FVC levels than emphysema but still have low FEV1/ FVC ratio Emphysema and asthma are called obstructive lung diseases as they limit expiratory flow and volume. How would a spirogram look for someone with a restrictive lung disease, such as pulmonary fibrosis? Higher numbers because they can get air out but can?t get air in What volumes and capacities would change in this case, and would these values be increased or decreased? VC decrease, TV decrease, IRV decrease, Total lung capacity decrease In an acute asthma attack, the compliance of the lung is decreased, not increased as it was for emphysema, and air flows freely through the bronchioles. Therefore, will the FEV1/FVC percentage be Less than normal Acute Asthma attack breathing with inhaler medication applied Usually the medication includes a smooth muscle relaxant that relieves the bronchospasms and induces bronchiole dilation. The medication may also contain an anti-inflammatory agent such as a corticosteroid that suppresses the inflammatory response Has the FVC reduced or increased, is it normal? Increased, no Has the FEV1 reduced or increase, is it normal Reduced? (guess), yes Which of these two changed more? FEV1 Explain the physiological reasons for the lung volumes and capacities that changed in the spirogram with the application of the medication Lungs able to exhale more, muscles relaxed How much of an increase in FEV1 do you think is required for it to be considered significantly improved by the medication Breathing during exercise In moderate aerobic exercise, which do you predict will change more the ERV or IRV? IRV Do you predict that the respiratory rate will change significantly in moderate exercise? Yes Comparing heavy exercise to moderate exercise, what values do you predict will change when the body?s significantly increased metabolic demands are being met by the respiratory system? IRV increased, ERV increases, TV increased During heavy exercise, what will happen the lung volumes and capacities that have been considered thus far? Go up Will the respiratory rate change? If so, how? Yes, increase Now consider the accuracy of you prediction what changed versus what you expected to change? IRV decrease, 2000 to 600 Which volumes changed the most and when? ERV decrease, TV increase, 1815 to 3605 Compare the respiratory rate during moderate exercise with that seen during heavy exercise? Heavy
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