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58 Cards in this Set

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 Barometric Pressure (PB) PB=760mmHg What contributes to PB Partial pressures of each gas contributes to PB Dalton's Law PB=PN2+PO2+PH2O+PCO2 (each gas contributes to the overall PB) Partial Pressure of O2 PO2=PB x FO2=760mmHg x 0.2094=~160mmHg; FO2 is the fraction of oxygen in the atmosphere What must we account for in the trachea? Must account for water vapor pressure (47mmHg) in the trachea The PO2 in the alveolar=? The PO2 in the alveolar=PCO2 in the arterial blood What is PA(alveolar pressure) immediately prior to inhalation? PA=760mmHg immediately prior to inhalation In order for air to flow into the lungs, what must happen? In order for air to flow into the lungs= PA < atmospheric pressure What does diaphragmic contraction during inspiration lead to? Diaphragmic contraction increases the vertical dimensions of the thoracic cavity. What happens to the pleural cavity during inspiration? The Pleural cavity decreases which increases the volume of the lungs. During inspiration, air flows according to? Air flows according to Boyle's Law. Boyle's Law Pressure of the gas varies inversely with the volume. EX: if we cut volume in 1/2, the pressure doubles. P=1/V What moves air into and out of the lungs? Changes in alveolar pressure move air in and out of lungs. Describe the steps leading to when the alveolar pressure=atmospheric pressure. 1. Inspiratory muscles contract 2. Thoracic cavity expands 3. Pleural pressure becomes more negative 4. Transpulmonary pressure increases 5. Lungs inflate 6. Alveolar pressure becomes subatmospheric 7. Air flows into lungs until alveolar pressure equals atmospheric pressure Minute Ventilation (V) Volume of air inhaled and exhaled per minute Expired Minute Ventilation (VE) Amount of air expired per minute; VE=VT x f; 500mL x 14 = 7L/min. Not all of tidal volume (VT) you being in participates in gas exchange, what happens to VT? Dead space ventilation in the coducting zone. VT is distributed between conducting and respiratory zones. If there is a tidal volume of 500mL. How much participates in gas exchange and how much remains in the conducting airways? 350mL participates in gas exchange, and 150mL remain in the conducting airways (VD) What is the equation for Tidal Volume (VT)? VT= VD + VA (dead space volume and alveolar volume) What is VD a function of? VD is a function of body size. Crude estimation: 1mL/lb body weight Is all air new during inspiration? No, not all air is new, it is air that was in the conducting zone being pushed to the respiratory zone. Alveolar Dead space (VD) 1. Air in alveoli without blood flow 2. Ventilation in excess blood flow Physiological dead space (VD) 1. Physiological VD=anatomic VD (conducting airways) + alveolar VD 2. Each type of VD is the volume of inspired air that does not participate in gas exchange Alveolar Ventilation (VA) Amount of fresh air reaching the alveoli/min; VA=(VT-VD) x f What is the most effective way to increase VA? Increasing the depth of breathing is the most effective way of increasing VA What is VA inversely related to? VA is inversely related to PaCO2 (if VA is halved, PACO2 will double What is an appropriate alveolar ventilation? Appropriate alveolar ventilation must accomplish two things: maintain partial pressure of oxygen so arterial oxygen (~100 mm Hg) and maintain partial pressure of CO2 (~40 mm Hg)—this is what we are trying to do with eucapnic (normal breathing). Hypoventilation decrease in alveolar ventilation Hyperventilation increased alveolar ventilation, leads to a fall in PACO2 An increase in PaCO2 results in? hypoventilation A decrease in PaCO2 results in? hyperventilation Compliance of lungs: 1. How much effort is required to stretch the lungs and chest wall 2. Delta V/Delta P High compliance of lungs easy expansion (takes little pressure) Low Compliance Expansion is resisted (takes a lot of pressure) What are the 2 factors which impact compliance? Elasticity and Surface Tension Elasticity Normal lungs are highly compliant and expand easily b/c the elastic fibers in lung tissue are easily stretched. Surface Tension 1. A contractile force acting parallel to the surface 2. Force between molecules in a liquid pull the surface molecules toward the interior What decreases surface tension? surfactant in alveolar fluid decreases surface tension Name 4 pulmonary conditions in which causes decreased compliance of the lungs. 1. Scar tissue (e.g., TB)--more difficult to get air in 2. Cause lung tissue to fill with fluid (pulmonary edema)--more difficult to get air in and diffusion problem with O2 3. Produce a deficiency in surfactant 4. Impede lung expansion in any way (e.g.,paralysis of intercostal muscles) When does increased lung compliance occur? Increased lung compliance occurs in emphysema due to destruction of elastic fibers in alveolar walls. What is the significance of low compliance in the lungs. It requires more work to inflate lungs. (takes more work to bring the air in) What is the significance of high compliance in the lungs? What happens to RV? More effort to force air out. RV increases over time, they can't get air out no matter how hard they try, which results in increased poressure of air to try and get in. What 2 things contribute to airway resistance? Turbulent flow and laminar flow contribute to airway resistance What ratio describes airway resistance? Ratio of driving pressure (DP) to airflow (V) What is the equation for total airway resistance (RAW)? For total airway resistance (RAW), the driving pressure is the pressure difference between atomosphere (pressure at mouth) and PA; RAW(Pmouth-PA)/V Where is the major site of airway resistance? Large and medium airways down to ~7th generation of airway branches (very little resistance in the small airways) What increases resistance? Any condition that narrows or obstructs the airways increases resistance. Therefore more pressure is required to maintain the same airflow What 2 conditions increase airway resistance? COPD (emphysema and chronic bronchitis) and asthma (airways are obstructed or collapsed and RAW increases) What decreases airway resistance? During inspiration bronchi and small airways enlarge as their walls are pulled outward in all directions, thus decreasing RAW. What does bronchial smooth muscle tone affect? Bronchial smooth muscle tone affects airway caliber (gets smaller), and thus RAW What controls smmooth muscle from trachea to terminal bronchioles (conducting zone)? Smooth muscle from trachea to terminal bronchioles (conducting zone) are under autonomic control. What occurs during the parasympathetic stimulation of smooth muscle tone? Bronchial constriction and increased mucus secretion What occurs during the sympathetic stimulation of smooth muscle tone? Dilation and inhibition of secretion TRUE/FALSE. No energy is expended furing inspiration? FALSE. Energy is expended during inspiration. What is the percentage of energy that is expended during inspiration? 1-5% of basal metabolism Name the 3 things that requires work during breathing? 1. Expand thoracic cavity 2. Inflate the lungs 3. Overcome RAW What is the equation of work? Work= f x d f= change in transpulmonary pressure d=change in lung volume W= P x delta(V) What happens to energy when a greater transpulmonary pressure is required to inflate the lungs? More energy is expended.