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The procedure for coughing up a sputum sample is explained to the patient. The patient should increase fluid intake the evening prior to collection (unless otherwise restricted), brush his or her teeth, remove dentures, and gargle and rinse the mouth with to remove food particles. These directions may decrease the contamination of the specimen by bacteria in the mouth or the throat. Using the sterile collection container provided, the patient is instructed to take three deep breaths, then force a deep cough and expectorate into a sterile screw-top container. The specimen should be collected in the early morning before ingesting food or drink if possible. The nurse or respiratory therapist examines the specimen to differentiate between sputum and saliva, documents its characteristics (color, viscosity, odor) and volume, and records the date and time the specimen went to the laboratory and the reason the specimen was taken. Five to 10 ml of sputum is typically needed for laboratory analysis. A specimen will be rejected by the laboratory if it contains excessive numbers of epithelial cells from the mouth or throat or if it fails to show adequate numbers of neutrophils on gram staining. If the patient cannot cough up a specimen, the respiratory therapist can use sputum induction techniques such as heated aerosol (nebulization), followed in some instances by postural drainage and percussion. More invasive means of obtaining a sputum specimen are with suction or bronchoscopy. These techniques are used in intubated patients, and in those from whom an uncontaminated specimen is required.
The following procedures should be followed to obtain a specimen by suctioning: the operator should put on sterile gloves, and a face shield, mask, and gown to avoid exposure to airborne pathogens during the procedure; suction equipment, specimen containers and oxygenating devices should assembled at the bedside; the patient should be hyperoxygenated to an oxygen saturation of 99% to 100% before suctioning; suction is applied for about 10 to 15 sec, and the patient’s respiratory and cardiac status are closely monitored for evidence of poor tolerance for the procedure. Sputum may also be collected bronchoscopically, through the inner channel of the bronchoscope. Normal saline is used as an irrigating solution if needed, a technique known as bronchoalveolar lavage (BAL). BAL increases the likelihood of obtaining a diagnostic specimen, although on occasion the fluid used to irrigate the airways may contain local anesthetics, which, because they are bacteriostatic, may prevent bacteria from growing in culture. After bronchoscopy, the patient is observed closely for hypoxia and other possible complications, and oral liquids are withheld until the gag reflex has returned and the patient can swallow saliva without difficulty. All sputum specimens should be sent to the laboratory immediately and refrigerated. They should be treated as infective until proven otherwise. Appropriate isolation procedures are used for handling specimens. Common isolates from sputum specimens include Staphylococcus aureus, Haemophilus influenzae, Streptococcous pneumoniae, and Moraxella catarrhalis.