TAILIEUCHUNG - Ebook Interpretation of pulmonary function tests - A practical guide (4/E): Part 2

(BQ) Part 2 book “Interpretation of pulmonary function tests - A practical guide” has contents: Distribution of ventilation, maximal respiratory pressures, preoperative pulmonary function testing, patterns in various diseases, illustrative cases, and other contents. | 8 Distribution of Ventilation Various pathologic processes alter the normal pattern of ventilation distribution (., the uniformity with which an inhaled breath is distributed to all the alveoli). For this reason, tests that detect abnormal patterns of ventilation distribution are fairly nonspecific and rarely of diagnostic importance. Their major contribution is that such abnormal patterns almost always are associated with alterations in ventilation–perfusion relationships (see pages 66 and 55). Abnormal distribution of ventilation also contributes to the frequency dependence of compliance (see page 68). There are several tests of ventilation distribution. Some are complex and require sophisticated equipment and complex analysis. This chapter discusses only the simplest procedure, the single-breath nitrogen (SBN2) test. 8A.  Single-Breath Nitrogen Test Procedure The testing equipment and procedure are illustrated in Figure 8-1. The subject exhales to residual volume (RV) and then inhales a full breath of 100% oxygen from the bag on the left. A slow, complete exhalation is directed by the one-way valve through the orifice past the nitrogen meter into the spirometer. The orifice ensures that expiratory flow will be steady and slow (< L/s), and we recommend its use. The nitrogen meter continuously records the nitrogen concentration of the expired gas as it enters the spirometer. With simultaneous plotting of the expired nitrogen concentration against expired volume, the normal graph shown in Figures 8-1 and 8-2A is obtained. Normal Results The plot in Figure 8-2A is from a seated normal subject. There are four important portions of the normal graph: phases I through IV. To understand this graph, we need to consider how the inhaled oxygen is normally distributed in the lungs of a seated subject. At RV, the alveolar nitrogen concentration can be considered uniform (roughly 80%) throughout the lung and alveolar gas is present in the trachea and upper airway .

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• Interpretation of pulmonary function tests
• Pulmonary function tests
• Distribution of ventilation
• Maximal respiratory pressures
• Preoperative pulmonary function testing
• Patterns in various diseases
• Illustrative cases
• Lung volumes
• Bronchial challenge testing
• Diffusing capacity of the lungs
• Arterial blood gases
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• following guidance
• recommendation
• including existing
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