Sarah is a 69-year old female that presented to the emergency department with shortness of breath. Her past medical history includes heart failure and COPD. Her pulse oximetry on room air is 82%. You notify the provider, and he orders oxygen at 2 L via nasal cannula NC. Sarah’s chest x-ray reveals bilateral pneumonia. Her arterial blood gas result are below: pH: 7.30 PaCO2: 58 mm Hg PaO2: 78 mm Hg HCO3: 26 mEq/L

The case of Sarah, a 69-year old female with a past medical history of heart failure and COPD, brings up several important considerations in the management of a patient with shortness of breath and abnormal arterial blood gas (ABG) results.

Sarah’s presenting complaint of shortness of breath and the finding of a low pulse oximetry reading of 82% on room air suggests that she is experiencing significant hypoxemia. Hypoxemia refers to a low level of oxygen in the blood, and it can be caused by a variety of conditions including respiratory disorders like COPD and pneumonia. In Sarah’s case, her diagnosis of COPD and subsequent finding of bilateral pneumonia on chest x-ray indicate that her hypoxemia is likely multifactorial in nature.

The ABG results provide additional insight into Sarah’s respiratory status. The arterial blood gas test measures several key parameters including pH, partial pressure of carbon dioxide (PaCO2), partial pressure of oxygen (PaO2), and bicarbonate (HCO3). In Sarah’s ABG results, the pH is 7.30, indicating that she is experiencing acidosis. This acidosis may be due to the accumulation of carbon dioxide (as indicated by the elevated PaCO2 level of 58 mm Hg) in her blood.

The low PaO2 level of 78 mm Hg further supports Sarah’s hypoxemia. A normal PaO2 level is generally considered to be between 75-100 mm Hg. However, it is important to interpret the PaO2 level in the context of the patient’s age, baseline respiratory function (such as COPD), and other comorbidities. In Sarah’s case, her baseline respiratory compromise due to COPD may have contributed to her lower PaO2 level.

The HCO3 level of 26 mEq/L falls within the normal range, suggesting that there is no significant metabolic disturbance in Sarah’s blood. This finding is consistent with the primary cause of her abnormal ABG results being respiratory in nature.

Based on these ABG results, Sarah exhibits findings consistent with a respiratory acidosis. Respiratory acidosis is characterized by an elevation in the PaCO2 level, resulting in a decrease in blood pH. The underlying cause of respiratory acidosis in this case is likely due to Sarah’s COPD and pneumonia, which impair her ability to adequately exchange carbon dioxide for oxygen during respiration.

Given Sarah’s presentation and ABG results, the provider orders oxygen at 2 L via nasal cannula (NC). Oxygen therapy is a common intervention for patients with hypoxemia, as it aims to increase the oxygen content in the bloodstream. In Sarah’s case, providing oxygen via nasal cannula at 2 L is an appropriate initial therapy to improve her oxygenation.

It is important to note that oxygen therapy should be implemented cautiously in patients with chronic respiratory conditions like COPD. In these patients, high levels of oxygen can suppress the respiratory drive and potentially worsen their condition. Therefore, the oxygen flow rate should be carefully monitored and adjusted to balance the need to correct hypoxemia while avoiding complications in patients with chronic respiratory conditions.

In summary, the case of Sarah highlights the complexity of managing a patient with shortness of breath and abnormal ABG results. Her clinical presentation and ABG results suggest a respiratory acidosis due to COPD and pneumonia. The provider’s order of oxygen at 2 L via nasal cannula is an appropriate initial intervention to improve Sarah’s oxygenation. However, ongoing monitoring and adjustment of oxygen therapy is necessary to ensure optimal management of her respiratory condition.