A patient’s ABGs include PaO2 88 mm Hg and PaCO2 38 mm Hg; mixed venous gases include PvO2 40 mm Hg and PvCO2 46 mm Hg. What do these findings indicate?
Impaired cardiac output
Unstable hemodynamics
Inadequate delivery of oxygen to the tissues
Normal capillary oxygen–carbon dioxide exchange
The Correct Answer is D
The given arterial and mixed venous blood gas values indicate normal capillary oxygen–carbon dioxide exchange. The values show that oxygen is adequately delivered to the tissues and that normal gas exchange is occurring between arterial and venous blood.
Rationale for correct answer:
4. Normal capillary oxygen–carbon dioxide exchange. Normal arterial blood gas (ABG) values include a PaO₂ of 80–100 mm Hg and a PaCO₂ of 35–45 mm Hg. The mixed venous gases (PvO₂ around 40 mm Hg and PvCO₂ around 46 mm Hg) also fall within expected ranges. The difference between arterial and venous oxygen levels (A–V difference) demonstrates that oxygen is being delivered to tissues and carbon dioxide is being effectively removed — a sign of healthy pulmonary and circulatory function.
Rationale for incorrect answers:
1. Impaired cardiac output. Low cardiac output would reduce tissue perfusion, leading to decreased PvO₂ and increased PvCO₂ due to poor oxygen delivery and CO₂ accumulation. However, the normal venous values here indicate that cardiac output is sufficient.
2. Unstable hemodynamics. Unstable hemodynamics, such as hypotension or shock, would alter tissue oxygen extraction and cause abnormal mixed venous gas values. These results show stable gas exchange and therefore do not suggest hemodynamic instability.
3. Inadequate delivery of oxygen to the tissues. Inadequate oxygen delivery would result in low PvO₂ (<30 mm Hg) and high PvCO₂, reflecting tissue hypoxia. The normal values here (PvO₂ 40 mm Hg, PvCO₂ 46 mm Hg) indicate that oxygen delivery is appropriate and tissue oxygenation is adequate.
Take-home points:
- Normal ABG and mixed venous gas values reflect effective oxygen delivery and carbon dioxide removal.
- A PaO₂ of 88 mm Hg and PaCO₂ of 38 mm Hg are within normal arterial limits.
- PvO₂ of 40 mm Hg and PvCO₂ of 46 mm Hg are consistent with normal venous return after tissue gas exchange.
- These findings confirm normal cardiopulmonary function and efficient capillary gas exchange.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
The nurse should interpret bronchial breath sounds in the lower lung fields as an abnormal finding. Normally, bronchial sounds are heard only over the trachea and mainstem bronchi. When these harsh, high-pitched sounds are heard in the peripheral lung areas, it indicates that lung tissue has become consolidated or filled with fluid, as seen in conditions such as pneumonia.
Rationale for correct answer:
4. Bronchial breath sounds in the lower lung fields. These sounds are characterized by a loud, tubular quality with a longer expiratory phase. In healthy lungs, the alveoli dampen bronchial sounds, so they should not be heard in the lower fields. Their presence there suggests abnormal air-to-fluid or air-to-solid ratios, typically caused by lung consolidation, atelectasis, or fibrosis. This finding warrants prompt investigation to identify the underlying pathology.
Rationale for incorrect answers:
1. Inspiratory chest expansion of 1 in. Normal chest expansion during inspiration is about 1 inch (2.5 cm) and should be symmetric. This finding is expected and indicates adequate lung inflation.
2. Percussion resonance over the lung bases. Resonance is the normal percussion tone over healthy lung tissue, reflecting air-filled alveoli. It indicates normal lung aeration and is not abnormal.
3. Symmetric chest expansion and contraction. Equal movement of both sides of the chest during breathing reflects normal respiratory mechanics and adequate bilateral lung expansion.
Take-home points:
- Bronchial breath sounds heard in peripheral or lower lung fields are a key sign of abnormal lung consolidation or fluid accumulation.
- Normal findings include resonant percussion tones and symmetric chest expansion.
- Recognizing changes in breath sound location or quality is essential for early detection of respiratory pathology.
- Document abnormal findings clearly and notify the provider for further evaluation, such as imaging or sputum testing.
Correct Answer is A
Explanation
The nurse would prepare the patient for a thoracentesis, which is the diagnostic procedure used to remove pleural fluid for analysis. This test helps determine the cause of pleural effusion, such as infection, malignancy, or inflammatory conditions, and can also relieve pressure on the lungs caused by excess fluid accumulation.
Rationale for correct answer:
1. Thoracentesis. Thoracentesis involves inserting a needle into the pleural space between the chest wall and the lungs to withdraw pleural fluid for diagnostic or therapeutic purposes. The fluid is analyzed for cell count, protein, glucose, culture, and cytology to identify infection, cancer, or other causes of pleural effusion. The procedure also helps alleviate symptoms such as dyspnea by reducing lung compression.
Rationale for incorrect answers:
2. Bronchoscopy. A bronchoscopy involves inserting a flexible tube through the nose or mouth into the bronchi to directly visualize the airways, obtain tissue biopsies, or remove secretions. It does not involve removal of pleural fluid from the pleural space.
3. Pulmonary angiography. This test involves injecting contrast dye into the pulmonary arteries to evaluate blood flow and detect pulmonary embolism or vascular abnormalities. It is not used for fluid removal or pleural fluid analysis.
4. Sputum culture and sensitivity. A sputum test analyzes mucus expectorated from the lungs to identify microorganisms causing infection, such as pneumonia or tuberculosis. It evaluates airway secretions, not pleural fluid from the pleural cavity.
Take-home points:
- Thoracentesis is the correct procedure for removing and analyzing pleural fluid.
- The test helps diagnose infection, malignancy, or inflammatory causes of pleural effusion.
- The nurse should position the patient upright and leaning forward, monitor for respiratory distress, and obtain a post-procedure chest x-ray to rule out pneumothorax.
- Other respiratory tests like bronchoscopy, angiography, or sputum culture serve different diagnostic purposes and do not access the pleural space.
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