Respiratory handout - Coast

Respiratory handout - Coast - RESPIRATORY OVERVIEW From a...

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RESPIRATORY OVERVIEW From a Handout by J.R. Coast When we examine the respiratory system, what we are looking at is two systems at the same time. One is a circulatory system, nearly as extensive as what we typically think of when we think of the cardiovascular system. The other is a system of airways that is also very extensive. In the clinical situation, a disruption of either part causes a decrease in our ability to oxygenate the blood that passes through the lungs, and thus decreases our ability to perform vigorous exercise. The main purpose of the respiratory system is to exchange gases, but it has other duties as well: 1. Regulates pH in conjunction with gas exchange. Works in conjunction with the bicarbonate buffer system in the cells and the blood. This is an extremely important role for the respiratory system during exercise. 2. Guard against disease - hairs in the nose and cilia in the trachea catch large particles in the inhaled air and move them toward the openings. Any particles (almost) that get to the alveoli are attacked by macrophages and removed by the blood or lymphatics. 3. Reflexly alter other systems - lungs are innervated by afferent nerves. The large ones sense normal stretch (stretch receptors) and tend to raise heart rate and blood pressure. They are involved in the control of breathing (Hering Breuer Reflex) when stretched. The smaller C-type fibers tend to cause a decrease in blood pressure and heart rate when stimulated. There is also some evidence that they can inhibit skeletal muscle. 4. Keep you afloat - swim bladders in some fish are for just that purpose. Some researchers think they evolved into lungs in land animals. Respiratory physiology carries a lot a baggage in terms of wording that has been around for many years. These are standards, and are used in all work involving respiratory physiology. Many abbreviations start out with a primary variable. With only one exception, this will be a capital letter. These are as follows: C concentration of gas in the blood (ml/L or ml/100ml) D diffusing capacity in general (vol/time/unit pressure) F fractional concentration of gas in dry phase (decimal or %) f breathing frequency (br/min) P gas pressure in general (mmHg or cmH 2 O) Q blood volume (ml or L) Q . rate of blood flow (ml/min or L/min) R respiratory exchange ratio (V . CO 2 /V . O 2 ) S saturation of hemoglobin with O 2 or CO 2 (%) V gas volume (ml or L) V . gas volume/time, rate of flow (ml/min, L/min) These primary variables are often followed by secondary variables. If the secondary variables are small capital letters, it refers to the gas phase: A alveolar gas I inspired gas
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B barometric L lung D dead space T tidal gas E expired gas ET end-tidal But if the secondary variables are lower case letters, they refer to the primary variable in the blood phase: a arterial blood (specify where) v venous blood b blood in general v mixed venous blood c capillary blood There are also secondary symbols and abbreviations that refer to a condition of a gas:
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Respiratory handout - Coast - RESPIRATORY OVERVIEW From a...

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