NCLEX: Respiratory disorders

Respiratory disorders: Diagnostic tests

Focus topic: Respiratory disorders

If the history and physical examination reveal evidence of respiratory dysfunction, diagnostic tests will help identify and evaluate the dysfunction. These tests include blood and sputum studies and endoscopic and imaging tests as well as other diagnostic tests, such as pulse oximetry, thoracentesis, and pulmonary function tests.

Respiratory disorders: Blood and sputum studies

Focus topic: Respiratory disorders

Blood and sputum studies include ABG analysis and sputum analysis.

ABG analysis
A practitioner will typically order an ABG analysis as one of the first tests to assess respiratory status because it helps evaluate gas exchange in the lungs. ABG analysis includes several measures:
• An indication of hydrogen ion concentration in the blood, pH shows the blood’s acidity or alkalinity.
• Known as the respiratory parameter, partial pressure of arterial carbon dioxide (PaCO2), reflects the adequacy of the lungs’ ventilation and carbon dioxide elimination.
• Partial pressure of arterial oxygen (PaO2) reflects the body’s ability to pick up oxygen from the lungs.
• Known as the metabolic parameter, the bicarbonate (HCO3 –) level reflects the kidneys’ ability to retain and excrete bicarbonate.

Teamwork

Focus topic: Respiratory disorders

The respiratory and metabolic systems work together to keep the body’s acid-base balance within normal limits. If respiratory acidosis develops, for example, the kidneys attempt to compensate by conserving bicarbonate. Therefore, if respiratory acidosis is present, expect to see the bicarbonate value rise above normal. Similarly, if metabolic acidosis develops, the lungs try to compensate by increasing the respiratory rate and depth to eliminate carbon dioxide. Therefore, expect to see the PaCO2 level fall below normal.

Nursing considerations
• Blood for an ABG analysis should be drawn from an arterial line if the patient has one. If a percutaneous puncture is necessary, the site must be chosen carefully. The brachial, radial, or femoral arteries can be used.
• After the sample is obtained, apply pressure to the puncture site for 5 minutes and tape a gauze pad firmly in place. (Don’t apply tape around the arm; it could restrict circulation.) Regularly monitor the site for bleeding, and check the arm for signs of complications, such as swelling, discoloration, pain, numbness, and tingling.
• Make sure you note on the slip whether the patient is breathing room air or oxygen. If oxygen, document the number of liters. If the patient is receiving mechanical ventilation, document the fraction of inspired oxygen. Also include the patient’s temperature on the slip; results may be corrected if the patient has a fever or hypothermia.
• Keep in mind that certain conditions may interfere with test results — for example, failing to properly heparinize the syringe before drawing a blood sample or exposing the sample to air. Venous blood in the sample may lower PaO2 levels and elevate PaCO2 levels.

Sputum analysis
Analysis of a sputum specimen (the material expectorated from a patient’s lungs and bronchi during deep coughing) helps diagnose respiratory disease, determine the cause of respiratory infection (including viral and bacterial causes), identify abnormal lung cells, and manage lung disease.

Respiratory disorders

Under the microscope

Focus topic: Respiratory disorders

A sputum specimen is stained and examined under a microscope and, depending on the patient’s condition, sometimes cultured. Culture and sensitivity testing identifies a specific microorganism and its antibiotic sensitivities. A negative culture may suggest a viral infection.

Nursing considerations
• Encourage the patient to increase his fluid intake the night before sputum collection to aid expectoration.
• To prevent foreign particles from contaminating the specimen, instruct the patient not to eat, brush his teeth, or use a mouthwash before expectorating. He may rinse his mouth with water.
• When the patient is ready to expectorate, instruct him to take three deep breaths and force a deep cough.

• Before sending the specimen to the laboratory, make sure it’s sputum, not saliva. Saliva has a thinner consistency and more bubbles (froth) than sputum.

Respiratory disorders: Endoscopic and imaging tests

Focus topic: Respiratory disorders

Endoscopic and imaging tests include bronchoscopy, chest X-ray, magnetic resonance imaging (MRI), pulmonary angiography, thoracic computed tomography (CT) scan, and ventilation-perfusion (V) scan.

Bronchoscopy
Bronchoscopy is direct inspection of the trachea and bronchi through a flexible fiber-optic or rigid bronchoscope. It allows the doctor to determine the location and extent of pathologic processes, assess resectability of a tumor, diagnose bleeding sites, collect tissue or sputum specimens, and remove foreign bodies, mucus plugs, or excessive secretions.

Nursing considerations
• Tell the patient that he’ll receive a sedative, such as diazepam (Valium), midazolam, or meperidine (Demerol).
• Explain that the doctor will introduce the bronchoscope tube through the patient’s nose or mouth into the airway. Then he’ll flush small amounts of anesthetic through the tube to suppress coughing and gagging.
• Explain to the patient that he’ll be asked to lie on his side or sit with his head elevated at least 30 degrees until his gag reflex returns; food, fluid, and oral drugs will be withheld as well until this time. Explain that hoarseness or a sore throat is temporary, and when his gag reflex returns, he can have throat lozenges or a gargle.
• Report bloody mucus, dyspnea, wheezing, or chest pain to the practitioner immediately. A chest X-ray will be taken after the procedure and the patient may receive an aerosolized bronchodilator treatment.
• Monitor for subcutaneous crepitus around the patient’s face and neck, which may indicate tracheal or bronchial perforation.
• Watch for breathing problems from laryngeal edema or laryngospasm; call the practitioner immediately if you note labored breathing.                                              • Observe the patient for signs of hypoxia, pneumothorax, bronchospasm, or bleeding.
• Keep resuscitative equipment and a tracheostomy tray available during the procedure and for 24 hours afterward.

Chest X-ray
Because normal pulmonary tissue is radiolucent, foreign bodies, infiltrates, fluids, tumors, and other abnormalities appear as densities (white areas) on a chest X-ray. It’s most useful when compared with the patient’s previous films, which allows the radiologist to detect changes.
By itself, a chest X-ray film may not provide information for a definitive diagnosis. For example, it may not reveal mild to moderate obstructive pulmonary disease. Even so, it can show the location and size of lesions and identify structural abnormalities that influence ventilation and diffusion. Examples of abnormalities visible on X-ray include pneumothorax, fibrosis, atelectasis, and infiltrates.

Nursing considerations
• Tell the patient that he must wear a gown without snaps and must remove all jewelry from his neck and chest but need not remove his pants, socks, and shoes.
• If the test is performed in the radiology department, tell the patient that he’ll stand or sit in front of a machine. If it’s performed at the bedside, someone will help him to a sitting position and a cold, hard film plate will be placed behind his back. He’ll be asked to take a deep breath and to hold it for a few seconds while the Xray is taken. He should remain still for those few seconds.
• Reassure the patient that the amount of radiation exposure is minimal. Explain that facility personnel will leave the area when the technician takes the X-ray because they’re potentially exposed to radiation many times each day.

MRI
MRI is a noninvasive test that employs a powerful magnet, radio waves, and a computer to help diagnose respiratory disorders. It provides high-resolution, cross-sectional images of lung structures and traces blood flow. MRI’s greatest advantage is its ability to “see through’’ bone and to delineate fluid-filled soft tissue in great detail, without using ionizing radiation or contrast media.

Nursing considerations
• Tell the patient that he must remove all jewelry and take everything out of his pockets. Explain that no metal can be in the test room; the powerful magnet may demagnetize the magnetic strip on a credit card or stop a watch from ticking. If he has any metal inside his body, such as a pacemaker, orthopedic pins or disks, and bullets or shrapnel fragments, tell him he must notify the practitioner.
• Explain to the patient that he’ll be asked to lie on a table that slides into an 8 (2.4 m) tunnel inside the magnet.
• Tell him to breathe normally but not talk or move during the test to avoid distorting the results; the test usually takes 15 to 30 minutes but may take up to 45 minutes.
• Warn the patient that the machinery will be noisy, with sounds ranging from a constant ping to a loud bang. Tell him ear protection will be provided. He may feel claustrophobic or bored. Suggest that he try to relax and concentrate on breathing or a favorite image.

Pulmonary angiography
Also called pulmonary arteriography, pulmonary angiography allows radiographic examination of the pulmonary circulation.

Dyeing to find out

Focus topic: Respiratory disorders

After injecting a radioactive contrast dye through a catheter inserted into the pulmonary artery or one of its branches, a series of X-rays is taken to detect blood flow abnormalities, possibly caused by emboli or pulmonary infarction. This test provides more reliable results than a V scan but carries higher risks, including cardiac arrhythmias.

Nursing considerations
• Tell the patient who will perform the test and where and when it will take place. Explain that the test takes about 1 hour and allows confirmation of pulmonary emboli.
• Tell the patient he must fast for 6 hours before the test or as ordered. He may continue his prescribed drug regimen unless the practitioner orders otherwise.
• Ask the patient if he has ever had an allergic reaction to contrast media, shellfish, or iodine. If he has, notify the doctor before starting the procedure.
• Explain that he’ll be given a sedative, such as diazepam, as ordered. He may also be given diphenhydramine (Benadryl) to reduce the risk of a reaction to the dye.
• Explain the procedure to the patient. The doctor will make a percutaneous needle puncture in an antecubital, femoral, jugular, or subclavian vein. The patient may feel pressure at the site. The doctor will then insert and advance a catheter.

• After catheter insertion, check the pressure dressing for bleeding and assess for arterial occlusion by checking the patient’s temperature, sensation, color, and peripheral pulse distal to the insertion site.
• After the test, monitor the patient for hypersensitivity to the contrast medium or to the local anesthetic. Keep emergency equipment nearby and watch for dyspnea.

Thoracic CT scan
A thoracic CT scan provides cross-sectional views of the chest by passing an X-ray beam from a computerized scanner through the body at different angles and depths. The CT scan provides a three-dimensional image of the lung, allowing the doctor to assess abnormalities in the configuration of the trachea or major bronchi and evaluate masses or lesions, such as tumors and abscesses, and abnormal lung shadows. A contrast agent is sometimes used to highlight blood vessels and to allow greater visual discrimination.

Nursing considerations
• Ask the patient if he has ever had an allergic reaction to contrast media, shellfish, or iodine. If he has, notify the practitioner before the procedure.
• Tell the patient that, if a contrast dye will be used, he should fast for 4 hours before the test.
• Explain that he’ll lie on a large, noisy, tunnel-shaped machine. If a contrast dye will be used, tell him that he may experience transient nausea, flushing, warmth, and a salty taste when the dye is injected into his arm vein.
• Tell him that the equipment may make him feel claustrophobic. He shouldn’t move during the test but should try to relax and breathe normally. Movement may invalidate the results and require repeat testing.
• Reassure the patient that he’ll receive only minimal radiation exposure during the test.

V scan
Although less reliable than pulmonary angiography, a V scan carries fewer risks. This test indicates lung perfusion and ventilation. It’s used to evaluate V mismatch, to detect pulmonary emboli, and to evaluate pulmonary function, particularly in preoperative patients with marginal lung reserves.

Respiratory disorders

Nursing considerations
• Tell the patient that a V scan requires injection of a radioactive contrast dye. Explain that he’ll lie in a supine position on a table as a radioactive protein substance is injected into an arm vein.
• While he remains in a supine position, a large camera will take pictures, continuing as he lies on his side, lies prone, and sits up. When he’s prone, more dye will be injected.
• Reassure the patient that the amount of radioactivity in the dye is minimal. However, he may experience some discomfort from the venipuncture and from lying on a cold, hard table. He may also feel claustrophobic when surrounded by the camera equipment.

Respiratory disorders: Other diagnostic tests

Focus topic: Respiratory disorders

Other diagnostic tests include pulse oximetry, thoracentesis, and pulmonary function tests (PFTs).

Pulse oximetry
Pulse oximetry is a continuous noninvasive study of arterial blood oxygen saturation using a clip or probe attached to a sensor site (usually an earlobe or a fingertip). The percentage expressed is the ratio of oxygen to Hb.

Nursing considerations
• Place the probe or clip over the finger or other intended sensor site so that the light beams and sensors are opposite each other.
• Protect the transducer from exposure to strong light. Check the transducer site frequently to make sure the device is in place, and examine the skin for abrasion and circulatory impairment.
• Rotate the transducer at least every 4 hours to avoid skin irritation.
• If oximetry has been performed properly, the saturation readings are usually within 2% of ABG values when saturations range between 84% and 98%.

Thoracentesis
Also known as pleural fluid aspiration, thoracentesis is used to obtain a sample of pleural fluid for analysis, relieve lung compression and, occasionally, obtain a lung tissue biopsy specimen.

Nursing considerations
• Tell the patient that his vital signs will be taken and then the area around the needle insertion site will be shaved.
• Explain that the doctor will clean the needle insertion site with a cold antiseptic solution, then inject a local anesthetic. Tell the patient that he may feel a burning sensation as the doctor injects the anesthetic.

Settle into stillness

Focus topic: Respiratory disorders

• Explain to him that after his skin is numb, the doctor will insert the needle. He’ll feel pressure during needle insertion and withdrawal. He’ll need to remain still during the test to avoid the risk of lung injury. He should try to relax and breathe normally during the test and shouldn’t cough, breathe deeply, or move.
• Emphasize that he should tell the doctor if he experiences dyspnea, palpitations, wheezing, dizziness, weakness, or diaphoresis; these symptoms may indicate respiratory distress. After withdrawing the needle, the doctor will apply slight pressure to the site and then an adhesive bandage.
• Tell the patient to report fluid or blood leakage from the needle insertion site as well as signs and symptoms of respiratory distress.

Respiratory disorders

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PFTs
PFTs can measure either volume or capacity. These tests aid diagnosis in patients with suspected respiratory dysfunction. The practitioner orders these tests to:
• evaluate ventilatory function through spirometric measurements
• determine the cause of dyspnea
• assess the effectiveness of medications, such as bronchodilators and steroids
• determine whether a respiratory abnormality stems from an obstructive or restrictive disease process
• evaluate the extent of dysfunction.

Verifying volume

Focus topic: Respiratory disorders

Direct spirography measures tidal volume and expiratory reserve volume, two of the five pulmonary function tests. Minute volume, inspiratory reserve volume, and residual volume are calculated from the results of other PFTs.

Calculating capacity

Focus topic: Respiratory disorders

Of the pulmonary capacity tests, functional residual capacity, total lung capacity, and maximal midexpiratory flow must be calculated. Either direct measurement or calculation provides vital capacity and inspiratory capacity. Direct spirographic measurements include forced vital capacity, forced expiratory volume, and maximal voluntary ventilation. The amount of carbon monoxide exhaled permits calculation of the diffusing capacity for carbon monoxide.

Nursing considerations
• For some tests, the patient will sit upright and wear a noseclip.
• Explain that he may receive an aerosolized bronchod ilator. He may need to receive the bronchodilator more than once to evaluate the drug’s effectiveness.
• Emphasize that the test will proceed quickly if the patient follows directions, tries hard, and keeps a tight seal around the mouthpiece or tube to ensure accurate results.
• Instruct the patient to loosen tight clothing so he can breathe freely. Tell him he must not smoke or eat a large meal for 4 hours before the test.

Respiratory disorders

• Keep in mind that anxiety can affect test accuracy. Also remember that medications, such as analgesics and bronchodilators, may produce misleading results. You may be asked to withhold bronchodilators and other respiratory treatments before the test. If the patient receives a bronchodilator during the test, don’t give another dose for 4 hours.

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