Respiratory Physiology II PDF

2 Ola Qutaiba Rawan Asrawi Yanal shafagoj Respiratory system To make diagnosis, prognosis, or even seeing the development of any medication, physicians always attend to make some tests by using different devices, one of them is the Spirometer. Spirometer: A device that is used to measure volume of t...

2 Ola Qutaiba Rawan Asrawi Yanal shafagoj Respiratory system To make diagnosis, prognosis, or even seeing the development of any medication, physicians always attend to make some tests by using different devices, one of them is the Spirometer. Spirometer: A device that is used to measure volume of the air coming in and out (inspired or expired). Ventilation: We can find in a normal lung (before inspiration) about 2.2L of air, and by inhaling (quite breathing) it’ll reach 2.7L, about 0.5L (500ml), we call that amount as the Tidal Volume (VT) in case of a forceful inspiration, the inspiration muscles are going to inhale an additional 3L (5.7L), and that one is called the Inspiratory Reserved Volume (IRV), which is reached only in doing exercises. Same thing if we make a forceful expiration, the expiration muscles of the abdomen and diaphragm are going to exhale half of the resting volume (2.2L), which gives a (1.1L), we call that mechanism as the Expiratory Reserved Volume (ERV). The volume of air remaining after the forceful expiration (we can’t expire it) is called the Residual Volume (RV). Notice that we ended up with 4 volumes, VT, IRV, ERV, RV. Knowing that the last one (RV) can not be measured by the Spirometer, because it stays in the lungs without moving. If we add more than one lung volume together, we get a lung capacity, which could be containing 2,3, or4 volumes, (Maximum 4 volumes). It’s known to have 4 lung capacities in that system. We use these volumes and capacities to know which lung disease we are dealing with. 1-Inspiration Capacity (IC): the maximum amount of air that can be inspired following a normal expiration. IC= VT+IRV 2-Functional Residual Capacity (FRC): the amount of air remaining in the lungs following a normal expiration (before inhaling or after exhaling). FRC=ERV+RV 3-Vital capacity (VC): the maximum amount of air that can be expired following a maximal inspiration. VC=IRV+VT+ERV 4-Total Lung Capacity (TLC): the amount of air in the lungs at the end of a maximal inspiration =6L. TLC=IRV+VT+ERV+RV A question to ask!!! Which of the following capacities, does the Spirometer measure??? Answer: the ones that do not deal with the Residual Volume (RV), which are the IC & VC. ——————————————————————————————————— The values giving above could vary between different countries and different regions, you’re going to find that these values could be higher (like in German), or lower (like in Japan), as their biological composition vary but in a few amounts. The type of tests that shows how good the lungs are, are called the Pulmonary Function Test (PFT), we also have the Kidney Function Test (KFT), and the Liver Function Test (LFT). Mechanics of Breathing (How do we breathe in): Of course, containing the inspiration (), and the expiration (), and these 2 terms are indicating the Flow, which happens per unit of time like (L/min) … -Flow is directly proportional to the Driving Force (DF), and inversely proportional to the Resistance. F=DF/R Take a note the driving force could be expressed as the difference in concentrations (if we are talking about ions), or as the difference in the pressure (if we are referring to the blood movement) & that term is also used in the air movement (DF=ΔP). If the pressure in A = the pressure in B, then ΔP (Driving Force) Is ZERO, and that means there’s No Flow. ————————————————————————————Ok, now pay attention, you know that the Patm=760mmHg, Right? That’s true, but here to avoid big numbers you have to consider It as Zero, Ok? So, whenever we say the Patm is zero, deep down you know it’s 760mmHg. More or less than the actual number, we’ll use signs. Patm =760 0, Patm=759 -1, Patm=761 +1 ———————————————————————————————————— If we want to make a driving force between A and B, we could Do one of two options, either by increasing the PA or increasing the PB, in order to make a Flow. Option 2 Option 1 PA =+1 Flow PB=0 PA =0 Flow PB =+1 However, we can’t do such a thing in normal breathing it’s impossible, but we can insert an endotracheal tube (intubation) and connect it with a machine to control the pressure (by increasing (we call it positive pressure breathing) or decreasing (negative pressure breathing), such a mechanism is called the Artificial breathing. Btw, this machine is called a Respirator/Ventilator/Resuscitator. You can find it inside the hospital’s ICU, or if you love watching Some medical Dramas, you’ll notice this machine a lot in Grey’s Anatomy ;) Now, in order to understand how we breath in or out, we use Boyle’s law, which describes the relationship between pressure and volume as if we multiplied them in a closed chamber, it’ll give a constant, so any increase in one the other will decrease. P x V = Constant The lungs are surrounded by 2 membranes (Visceral & Parietal), and between them we have the plural cavity, which Pintraplural = -4 mmHg (below the Patm). A comparison between Inspiration and Expiration: Inspiration Active process (ATP) 1-The diaphragm contracts (it is a skeletal muscle) and that contraction needs ATP. Expiration Passive process The diaphragm relaxes. 2-There’ll be increasing in the There’ll be decreasing in the volume of thoracic cavity. volume of thoracic cavity. Plural cavity The numbers are for 5-The intrapulmonary /alveolar The intrapulmonary /alveolar pressure becomes negative. pressure becomes positive. 4-Lung inflates increases) (its volume Lung volume decreases 3-Intrathoracic/intraplural pressure is more negative = -6mmHg Intrathoracic/intraplural pressure is less negative = -4mmHg 6-Air enters the lungs. Air is pushed out of lungs. Ranking!!! Notes: 1- The muscles of a respiratory system consume 2% of total Oxygen consumption (very efficient), and that’s because we only need them in contraction, so it’s a one way ticket, but if the lungs suffer from certain disease, it’ll affect the whole mechanism, in which we have to make a lot of effort in Oxygen consumption and ATP usage, and that could use about 80% of Oxygen, and so the body could die from a Fatigue. 2- The air isn’t inflating the lungs, it is the lungs that inflate to make the air enters them. Schematic View of Respiration Po2 in ADS =150mmHg, Pco2 in ADS =0mmHg Po2 in Respiratory zone = 100, Pco2 =40mmHg Pco2 in venous side =45, Pco2 in arterial side =40mmHg Pco2 in interstitial fluid/tissue =45mmHg Intercellular Pco2 must be >45mmHg, in order to make The diffusion out the cell. ‫تم تغيير ارقام الجدول الموجود في ساليدات الجزء األول‬.‫ إلى األرقام المعتمدة من قبل د ينال‬، A Revision from the Cardiac System CO = SV x HR = 70 x 70 = 4900~5000 ml/min And that is applying on the Respiratory system as well. Respiratory Minute Ventilation (RMV), which is the volume of air inhaled or exhaled per minute. RMV=RR * VT Every time a person breath, he inhales and exhale 0.5 L, which is equal to the Tidal Volume (Vt). When multiplying it to 12 (RR), it gives 6L/min, which is the total amount of air moved into and out of respiratory system per minute, ( close to the number above). Respiratory rate or frequency RR: Number of breaths taken per minute. …‫ هههههههه‬، ‫ركزوا اللي جاي يعتبر أهم المهم‬ Ok, when we exhale the air (breathing out), the air composition in the ADS will be the same as the alveolar air, because the air is coming directly from that zone, End of Exhaling so the values of pressure in the ADS are Po2=100mmHg, Pco2=40mmHg. Same thing with the inhalation (breathing in), the air Composition in the alveolar zone will be the same as The ADS zone, so the values of pressure are Po2 =150mmHg, Pco2 =0mmHg Po2=100, Pco2=40 End of Inhaling Po2=150, Pco2=0 * Tidal volume is used to describe the volume of air that is exhaled or inhaled at rest which = 500 ml. During inspiration: If an adult male is 75 kg, Anatomic dead space volume is 150 ml. As this 500 ml enters, the first 150 ml will push the air that is present in Anatomic dead space (the remaining expired air) Into the alveoli as if nothing happened (PO2 100, PCO2 40). After that, the fresh air which is inhaled will displace the expired air that has been pushed (in the ADS). This fresh air has a PO2 = 150, PCO2 = 0 So, the first 150 LITERALLY did nothing. The second 150 ml will push the first 150 into the alveoli and the other 150 will displace the 2nd one. Therefore, the fresh air that entered is 350 ml. -Alveolar ventilation: the amount of volume of fresh air that enters the lungs per minute. Alv. Ventilation = 350 ml * 12 = 4.2 L ADS ventilation = 150 ml *12 = 1.8 L Inside the thorax, we find that the heart is neighbouring the lungs, and that site is actually helping the lungs in receiving air and blood (ventilation and perfusion), and these two are a Must for the lungs to work properly, as we have a ratio between them (V/Q), any volume that reaches the alveoli without being per fused is a Wasting Volume (we can’t benefit from it as it does not have any blood in it). Physiological dead space is equal to anatomic plus wasted volume, which is the volume of air in the respiratory zone that does not take part in gas exchange, knowing that is usually equal to zero, leaving the physiological dead space equal to the Anatomical dead space. A suggested question from Dr. Yanal!!!! Can the PDS be smaller than the ADS????? (Think about it) Some information from the slides (Read them): End of sheet 2