A nurse is caring for a client who has COPD. The nurse should identify that the client is at risk for which of the following acid-base imbalances?

Choice A reason: Prone is not the best position to allow maximal lung expansion. Prone is a position where the client lies on their stomach, with their head turned to one side. Prone can help to improve oxygenation in some cases of acute respiratory distress syndrome (ARDS), but it can also increase the risk of pressure ulcers, facial edema, and airway obstruction.

Choice B reason: Side-lying is not the best position to allow maximal lung expansion. Side-lying is a position where the client lies on their side, with their head supported by a pillow. Side-lying can help to prevent aspiration and reduce the work of breathing in some clients, but it can also compromise the ventilation of the dependent lung.

Choice C reason: Supine is not the best position to allow maximal lung expansion. Supine is a position where the client lies on their back, with their head and shoulders slightly elevated. Supine can help to maintain a patent airway and facilitate suctioning in some clients, but it can also increase the risk of atelectasis, pneumonia, and hypoxemia.

Choice D reason: Upright is the best position to allow maximal lung expansion. Upright is a position where the client sits or stands with their back straight and their chest expanded. Upright can help to improve lung compliance, reduce airway resistance, and enhance gas exchange in clients with respiratory failure. Upright can also reduce the pressure on the diaphragm and abdominal organs, and promote the drainage of secretions.

Choice A reason: Muscle twitching is a sign of central nervous system oxygen toxicity, which can occur when breathing high concentrations of oxygen under pressure. It can also cause seizures, confusion, and loss of consciousness.

Choice B reason: Facial flushing is not a symptom of oxygen toxicity. It can be caused by other conditions such as fever, allergic reactions, or alcohol consumption.

Choice C reason: Periorbital edema is not a symptom of oxygen toxicity. It can be caused by other conditions such as kidney disease, heart failure, or allergies.

Choice D reason: Metallic taste in mouth is not a symptom of oxygen toxicity. It can be caused by other conditions such as medication side effects, dental problems, or infections.