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Download EVALUATION OF THE PATIENT WITH PULMONARY DISEASE
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EVALUATION OF THE PATIENT WITH PULMONARY DISEASE By NUSRUM IQBAL, MD Diplomate American Board of Internal Medicine RESPIRATORY SYSTEM SOME FACTS •Most common reason for the patient coming to the doctor •Lungs have a surface area of 500m •Daily air exchange is 7000L ANATOMY •Nose & Sinuses •Throat •Middle ear & Eustachian tube •Larynx •Trachea •Bronchi & Bronchioles •Alveoli •Vasculature PHYSIOLOGY •Type I & Type II Alveoli •Pulmonary Circulation & Vascular Resistance •Ventilation & gas Exchange Evaluation on a Macroscopic level •Physical Examination •Chest radiography •Computed tomography •Magnetic Resonance Imaging MRI •Lung Scanning •Pulmonary angiography •Ultrasonography •Bronchoscopy Evaluation on a Microscopic level •Obtaining specimens •Processing specimens Assessment on a functional level •Pulmonary Function Tests •Arterial Blood Gases •Exercise Testing Physical Examination Inspection Palpation •check the expansion •vocal or tactile fremitus Percussion •resonant •dull /stony dull Auscultation •vesicular breathing •bronchial breathing •advetitious breath sounds CHEST X-RAY •Usually taken in two standard view •PA view/ lateral view •Knowledge of radiographic anatomy is fundamental for the interpretation of consolidation or collapse and for location of the abnormalities •A careful examiner uses the systematic approach in analysing the films •One can detect changes in bones, soft tissues, the heart, other mediastinal structures and pleural space Computed Tomography •CT scan has revolutionized the field of diagnostic radiology •Allows a series of cross-sectional images to be constructed •useful in evaluating pulmonary nodules and the mediastinum and pleural and chest wall diseases •detect subtle differences in tissue density that cannot be detected by conventional radiography Magnetic Resonance Imaging •Newest of the radiologic technique avilable •Very expansive •Evaluating intravascular structure and can differentiate the vascular from the nonvascular structure LUNG SCANNING •Injected or inhaled radioisotopes readily provide information about pulmonary blood flow and ventilation •Imaging of gamma radiation from these isotopes produces a picture showing the distribution of blood flow and ventilation throughout the lungs •Commonest tecnique requires tc99 •useful in the detection of the pulmonary embolism Bronchoscopy •Direct visualization of the airways •brochoalveolar lavage •Transbronchial needle aspiration/biopsy •evaluation of the endobrochial malignancy •sampling of an area of parenchymal disease by bronchoalveolar lavage •evaluation of hemoptysis •removal of foreign body Evaluation on a microscopic level •Microscopy often provides the definite diagnosis of pulmonary diseases •examples are lung tumors, pulmonary infection and miscellaneous pulmonary diseases Assessment on a functional level Pulmonary evaluation on a macroscopic or microscopic level aims at a diagnosis of the lung disease, but neither can determine the extent to which normal functions of the lungs are impaired •Pulmonary function tests •Arterial Blood gases •Exercise testing Pulmonary Function Tests Provides an objective method for assessing functional changes in a patient with known or suspected lung disease Physicians are able to answer the following questions •Does the patient have significant lung disease sufficient to cause respiratory impairment and to account for his or her symptoms? •What functional pattern of lung disease does the patient have-- restrictive or obstructive disease? Serial evaluation of the PFTs will guide the physicians about the detoriation or improvement in the functional capacity OBJECTIVE Three main categories of information can be obtained with routine pulmonary function testing •Lung volumes, which provide a measurement of the size of the various compartments with in the lungs •Flow rates, which measures maximal flow within the airways •Diffusion capacity, which indicates how readily the gas occurs from the alveolus to the pulmonary vasculature LUNG VOLUMES determine by spirometry and either gas dilution or body plethysmography Four volumes are particularly important Total lung capacity TLC •the total volume of gas with in the lungs after maximal inspiration Residual volume RV •the volume of gas remaining in the lungs after maximal expiration Vital capacity VC •the volume of gas expired when going from TLC to RV Functional residual capacity •the volume of gas within the lungs at the resting state, that is, at the end of expiration during the normal tidal breathing pattern FLOW RATES Assessing airflow during maximal forced expiration, that is, with the patient breathing as hard as possible from TLC down to RV •Volume expired during this maneuver is the forced vital capacity •Volume expired during the first second is the forced expiratory volume in 1 second (FEV1) •It is common to use the ratio between these two measurements (FEV1/FVC) as an index of obstruction to airflow •MMFR (maximum midexpiratory flow rate) is the forced expiratory flow between 25 and 75 percent of the vital capacity DIFFUSING CAPACITY •It is the measurement of the rate of transfer of gas from the alveolus to the capillary measured in relation to the driving of the gas across the alveolar-capillary membrane •Small concentrations of carbon monooxide are generally used for this purpose •It is most dependent on the the number of functioning alveolar-capillary units It is decreased in 3 categories of disease •Emphysema •Interstitial lung disease •Pulmonary vascular disease Pattern of Pulmonary function Impairment Obstructive pattern •obstruction to the airflow •diminished rates of expiratory airflow (FEV1/FVC, MMFR) Restrictive pattern •evidence of decreased lung volumes especially TLC but no airflow obstruction
