introduction of respiratory system copy.pdf

Introduction of respiratory system Prof. Dr.Ahmed Hussein Jasim F.I.B.M.S (resp) F.I.B.M.S ( med)  Investigation of respiratory system 1- Chest X-ray The chest x-ray (CXR), generally including both posteroanterior and lateral views , is often...

Introduction of respiratory system Prof. Dr.Ahmed Hussein Jasim F.I.B.M.S (resp) F.I.B.M.S ( med)  Investigation of respiratory system 1- Chest X-ray The chest x-ray (CXR), generally including both posteroanterior and lateral views , is often the first diagnostic study in pts presenting with respiratory symptoms. With some exceptions (e.g., pneumothorax), the CXR pattern is usually not sufficiently specific to establish a diagnosis; instead, the CXR serves to detect disease, assess magnitude, and guide further diagnostic investigation. With diffuse lung disease, CXR can detect an alveolar, interstitial, or nodular pattern. CXR can also detect pleural effusion and pneumothorax, as well as abnormalities in the hila and mediastinum. Lateral decubitus views can be used to estimate the size of freely flowing pleural effusions. 2- Sputum examination Sputum can be obtained by spontaneous expectoration or induced by inhalation of an irritating aerosol-like hypertonic saline. Sputum is distinguished from saliva by the presence of alveolar macrophages and other inflammatory cells as opposed to squamous epithelial cells. Sputum examination should include gross inspection for blood and color, as well as Gram’s stain and routine bacterial culture. Bacterial culture of expectorated sputum may be misleading due to contamination with oropharyngeal flora. Sputum samples can also be assessed for a variety of other pathogens, including mycobacteria, fungi, and viruses. Sputum samples induced by hypertonic saline can be stained for the presence of Pneumocystis jirovecii. Cytologic examination of sputum samples can be used as an initial screen for malignancy 3- Pulse oximetry An oximeter is a spectrophotometric device that measures arterial oxygen saturation (SpO2) by determining the differential absorption of light by oxyhaemoglobin and deoxyhaemoglobin. Modern oximeters use a probe incorporating a light source and sensor attached to a patient’s ear or finger. Oximeters are easy to use, portable, non-invasive and inexpensive. They are widely used for the continuous measurement of SpO2 and to adjust oxygen therapy. In acutely ill patients with no risk of CO2 retention, SpO2 should be maintained at 94–98%. Movement artifact, poor tissue perfusion, hypothermia and nail varnish can lead to spuriously low SpO2 values. Dark skin pigmentation and raised levels of bilirubin or carboxyhaemoglobin can result in false increases in SpO2. Oximetry is less accurate with saturations 75% 6- The computed tomography scan Chest computed tomography (CT), typically performed with helical scanning and multiple detectors, is widely used to clarify radiographic abnormalities detected by CXR. Advantages of chest CT compared with CXR include (1) ability to distinguish superimposed structures due to cross-sectional imaging; (2) superior assessment of tissue density, permitting accurate assessment of the size and density of pulmonary nodules and improved identification of abnormalities adjacent to the chest wall, such as pleural disease; (3) with the use of IV contrast, ability to distinguish vascular from nonvascular structures, which is especially useful in assessing hilar and mediastinal abnormalities (including staging of lung cancer); (4) with CT angiography, ability to detect pulmonary emboli; and (5) due to superior visible detail, improved recognition of parenchymal and airway diseases, including emphysema, bronchiectasis, lymphangitic carcinoma, and interstitial lung disease. o chest CT scans can provide a three-dimensional reconstruction of the airways down to at least the sixth generation, providing a virtual bronchoscopy. 7- Magnetic resonance imaging Magnetic resonance imaging (MRI) is generally less useful than CT for evaluation of the respiratory system but can be helpful to assist in the evaluation of intrathoracic cardiovascular pathology without radiation exposure and to distinguish vascular and nonvascular structures without IV contrast. MRI can also distinguish tumor from post-stenotic atelectasis and assess tumor infiltration of the chest wall or mediastinum. However, the presence of metallic foreign bodies, pacemakers, and intracranial aneurysm clips preclude the use of MRI. 8-Ultrasound  Diagnostic US is not useful for assessing the pulmonary parenchyma, but it can detect and localize pleural abnormalities and guide thoracentesis of a pleural effusion.  As a nonionizing imaging approach, it is safe to perform on pregnant women and children.  Real-time US imaging can assess diaphragmatic mobility.  Portable US is useful to monitor resolution of pneumothorax and pleural effusion. 9- Positron emission tomography (PET) scanning (PET) scanning assesses the uptake and metabolism of a radiolabeled glucose analogue. Because malignant lesions usually have increased metabolic activity, PET scanning, especially when combined with CT images in PET/CT, is useful to assess pulmonary nodules for potential malignancy and to stage lung cancer. PET studies are limited in assessing lesions