Ebook Wilkins clinical assessment in respiratory care (7/E): Part 2
➤ Gửi thông báo lỗi ⚠️ Báo cáo tài liệu vi phạmNội dung chi tiết: Ebook Wilkins clinical assessment in respiratory care (7/E): Part 2
Ebook Wilkins clinical assessment in respiratory care (7/E): Part 2
186 CHAPTER 9 • Pulmonary Function TestingFIGURE 9-4 Calculation of back extrapolated volume (BEV) Back-extrapolation is used when the spirogram docs Ebook Wilkins clinical assessment in respiratory care (7/E): Part 2 not exhibit a sharp rise in flow at the beginning of the forced vital capacity (FVC). To compute the BEV, a straight line is drawn through the steepest part of the curve and extended to cross the volume baseline. The point of intersection is the back-extrapolated time zero. The distance from the ti Ebook Wilkins clinical assessment in respiratory care (7/E): Part 2me zero point to the FVC curve is the BEV. (Courtesy of Strategic Learning Associates, LLC, Little Silver, NJ)± 2 standard deviations (9S% ot the valuEbook Wilkins clinical assessment in respiratory care (7/E): Part 2
es)FIGURE 9-5 Determination of upper and lower limits of normal. Ninety-five percent of all values in a normal distnbution fall within ±2 standard dev186 CHAPTER 9 • Pulmonary Function TestingFIGURE 9-4 Calculation of back extrapolated volume (BEV) Back-extrapolation is used when the spirogram docs Ebook Wilkins clinical assessment in respiratory care (7/E): Part 2 Learning Associates, LLC, Little Silver, NJ)FIGURE 9-6 Algorithm for interpreting spirometry test results Dico, diffusing capacity; FVC, forced vital capacity; LLN, lower limit of normal. (Courtesy of Strategic Learning Associates. LLC. Little Silver. NJ)Pulmonary Function Testi ware valid (three a Ebook Wilkins clinical assessment in respiratory care (7/E): Part 2cceptable maneuvers, with wo of them being repeatable), one compares the patient's FVC, FEVp and FEV|/FVC to the predicted reference ranges. If all thEbook Wilkins clinical assessment in respiratory care (7/E): Part 2
ree values fall within rhe reference ranges, the results are deemed normal.If, however, the FEV| is reduced and the FEVj/FVC ratio falls below its LLN186 CHAPTER 9 • Pulmonary Function TestingFIGURE 9-4 Calculation of back extrapolated volume (BEV) Back-extrapolation is used when the spirogram docs Ebook Wilkins clinical assessment in respiratory care (7/E): Part 2pairment. Often, the severity of obstruction is quantified according to magnitude of reduction in FEVj/FVC, as outlined in Table 9-4.The other major possibility is a reduced FVC, normal or reduced FEV|, and FEVj/FVC above the LLN (normal or higher than normal). An FEVi/ FVC above the LLN rulei out a Ebook Wilkins clinical assessment in respiratory care (7/E): Part 2n obftructitr impairment. However, the presence of a reduced FVC suggests that the patient may have a reduction in lung volume, which would be classifEbook Wilkins clinical assessment in respiratory care (7/E): Part 2
ied as a restrictive ventilator}' impairment.TABLE 9-4An obstructive ventilatory impairment IS charactenzed byreduced flows, as evident by an FEV,/FVC186 CHAPTER 9 • Pulmonary Function TestingFIGURE 9-4 Calculation of back extrapolated volume (BEV) Back-extrapolation is used when the spirogram docs Ebook Wilkins clinical assessment in respiratory care (7/E): Part 2cation of Airway ObstructionSeverity of ObstructionFEV1 (% Predicted)Mild70-74Moderate60-69Moderately severe50-59Severe3S-49Very severe<35Interpretation is enhanced by review of rhe graphic plots obtained by spirometry. Figure 9-7 portrays typical vokime-versus-time curves for a normal subject, one Ebook Wilkins clinical assessment in respiratory care (7/E): Part 2with an obstructive impairment and one with a restrictive disorder. Note that rhe obstructive partem is characterized by a decrease in the slope of thEbook Wilkins clinical assessment in respiratory care (7/E): Part 2
e curve (indicating reduction in expiratory flow) and a longer time to empty the lungs. On the other hand, in rhe restrictive pattern, the lung emptie186 CHAPTER 9 • Pulmonary Function TestingFIGURE 9-4 Calculation of back extrapolated volume (BEV) Back-extrapolation is used when the spirogram docs Ebook Wilkins clinical assessment in respiratory care (7/E): Part 2ing the presence and location of large airway obstruction. Figure 9-8 provides six examples of flow-volume loops representing distinct patterns of abnormal function. Disorders causing generalized expiratory obstruction-like asthma and emphysema-mainly affect the MEFV curve, with both exhibiting a re Ebook Wilkins clinical assessment in respiratory care (7/E): Part 2duction in peak flow and FEFso*. Note also that the MEFV portion of the loop on the patient with emphysema is markedly concave and positioned left ofEbook Wilkins clinical assessment in respiratory care (7/E): Part 2
rhe normal loop, indicating greater flow obstruction at lower lung volumes as well as air trapping and hyperinflation. On the other hand, a patient wi186 CHAPTER 9 • Pulmonary Function TestingFIGURE 9-4 Calculation of back extrapolated volume (BEV) Back-extrapolation is used when the spirogram docs Ebook Wilkins clinical assessment in respiratory care (7/E): Part 2 volume axis, consistent with the smaller FVC.The bottom three flow-volume loops in Figure 9-8 portray different types of large airway obstruction. The variable intrathoractc obstruction loop reveals a markedly reduced peak flow on expiration despite near-normal inspiratory flows. This typically is Ebook Wilkins clinical assessment in respiratory care (7/E): Part 2rhe result of expiratory flow obstruction in the large airways, as may occur with tracheomalacia or tumors of the trachea or bronchi. The opposite patEbook Wilkins clinical assessment in respiratory care (7/E): Part 2
tern IS seen in variable extrathoracic obstruction, that IS, reduced inspiratory flow and relatively normal expiratory flow. Vocal cord dysfunction an186 CHAPTER 9 • Pulmonary Function TestingFIGURE 9-4 Calculation of back extrapolated volume (BEV) Back-extrapolation is used when the spirogram docs Ebook Wilkins clinical assessment in respiratory care (7/E): Part 2tructive, and restrictive disorders. Curves are as they appear on commonly available spirometers with tracings beginning at the bottom left corner. (From Kacmarek RM, Stoller JK, Heuer AJ- igm's fundamental of respiratory cate, ed 10, St. Louis, 2013, Mosby.)188CHAPTER 9 • Pulmonary Function Testing Ebook Wilkins clinical assessment in respiratory care (7/E): Part 2reduction ill inspiratory and expiratory Hows suggests a fixed large airway obstruction. Causes of fixed large airway obstruction include tracheal steEbook Wilkins clinical assessment in respiratory care (7/E): Part 2
nosis, tracheal rumors, and foreign body aspiration.After the basic pattern is identified, additional testing may be indicated. If rhe spirometry resu186 CHAPTER 9 • Pulmonary Function TestingFIGURE 9-4 Calculation of back extrapolated volume (BEV) Back-extrapolation is used when the spirogram docs Ebook Wilkins clinical assessment in respiratory care (7/E): Part 2ble with treatment, that is, if it responds to bronchodilator therapy (see Fig. 9-6). This is accomplished by measuring spirometry values before and after adminis tralion of the selected bronchodilator. Normally, the baseline spirometry should be conducted al least 4 hours after any prior use of a s Ebook Wilkins clinical assessment in respiratory care (7/E): Part 2hort acting p agonist (e.g., albuterol) and al least 12 hours after any administration of a long-acting bronchodilator (c.g., salmeierol).Box 9 3 outlEbook Wilkins clinical assessment in respiratory care (7/E): Part 2
ines rhe key elements in rhe procedure for assessing reversibility. If after bronchodilator adminisrra tion, the FEVj or FVC increases by more than 12186 CHAPTER 9 • Pulmonary Function TestingFIGURE 9-4 Calculation of back extrapolated volume (BEV) Back-extrapolation is used when the spirogram docs Ebook Wilkins clinical assessment in respiratory care (7/E): Part 2wever, some patients U'ho do nor meet the criteria for reversibility may still experience improvement after bronchodilator therapy, such as a decrease in dyspnea. 'Ulis response likely is due to a decrease in hyperinflation occurring without a significant decrease in airway resistance.■ SIMPLY STATE Ebook Wilkins clinical assessment in respiratory care (7/E): Part 2DI An obstructive ventilatory defect IS considered reversibleI if. after bronchodilator administration, the FEVj or FVCI increases by more than 12% anEbook Wilkins clinical assessment in respiratory care (7/E): Part 2
d 200 mlAs indicated in Figure 9-6. a reduced FVC in the presence of a normal or high FEV|/FVC suggests that theFIGURT 9-8 Patterns of pulmonary dysfu186 CHAPTER 9 • Pulmonary Function TestingFIGURE 9-4 Calculation of back extrapolated volume (BEV) Back-extrapolation is used when the spirogram docs Ebook Wilkins clinical assessment in respiratory care (7/E): Part 2manual of pulmonary function lotting, ed 10, St. Louis,2013, Mosby.)patient may have a reduction in lung volumes. I lowcver, this same pattern can occur among patients who fail to completely inhale or exhale during the maneuver. For this reason, confirmation of a reduction in lung volumes and the pr Ebook Wilkins clinical assessment in respiratory care (7/E): Part 2esence of a restrictive disorder requires measurement of static lung volumes (FRC, RV, I I.C). Moreover, if it is suspected that the restrictive condiEbook Wilkins clinical assessment in respiratory care (7/E): Part 2
tion is due to an interstitial disease processes, most doctors will also request a dilfusing capacity study (D1X-O).186 CHAPTER 9 • Pulmonary Function TestingFIGURE 9-4 Calculation of back extrapolated volume (BEV) Back-extrapolation is used when the spirogram docs 186 CHAPTER 9 • Pulmonary Function TestingFIGURE 9-4 Calculation of back extrapolated volume (BEV) Back-extrapolation is used when the spirogram docsGọi ngay
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