Dead air is not involved in respiration because

Correct Answer: D

Rationale: The correct answer is D because dead air is the air present in the alveoli that does not participate in gas exchange. It is located deep in the lungs, beyond the respiratory bronchioles where gas exchange occurs. Dead air does not reach the alveoli to participate in respiration. Choices A, B, and C are incorrect because the quantity of dead air or its oxygen content are not the primary reasons why it is not involved in respiration.

Correct Answer: A

Rationale: The correct answer is A: The patient has a narrowed airway. Wheezing throughout the lung fields indicates the presence of narrowed airways, often due to conditions like asthma or chronic obstructive pulmonary disease (COPD). Wheezing is caused by turbulent airflow through narrowed airways, leading to a high-pitched whistling sound during expiration. This is a characteristic finding in patients with obstructive airway diseases. Summary of other choices: B: The patient having pneumonia would typically present with symptoms like fever, cough, and consolidation on auscultation, not wheezing. C: The patient needing physiotherapy may have respiratory muscle weakness or secretion clearance issues but would not typically present with wheezing throughout lung fields. D: The presence of a hemothorax (blood in the pleural space) would manifest as decreased breath sounds and signs of respiratory distress but not wheezing.

Correct Answer: B

Rationale: The correct answer is B: Maintaining the patient's chest tube. After a mediastinotomy, the focus of postprocedure care is to ensure proper drainage and prevent pneumothorax. Chest tube maintenance is crucial for monitoring drainage, preventing complications, and promoting lung expansion. Assisting with PFT (A) is not a priority immediately post mediastinotomy. Administering oral suction (C) can disrupt the chest tube and increase infection risk. Performing chest physiotherapy (D) may be indicated later but is not the immediate priority.

Correct Answer: B

Rationale: The correct answer is B: epiglottis. The epiglottis is a flap of tissue that covers the opening of the trachea during swallowing, preventing food and fluid from entering the lower respiratory system. This mechanism ensures that the airway remains clear and protects the lungs from aspiration. The other choices are incorrect because: A: The larynx is involved in sound production and air passage but does not specifically protect the lower respiratory system during swallowing. C: The vestibule is the space within the nasal cavity but does not play a direct role in protecting the lower respiratory system during swallowing. D: The pharynx is a passageway for both food and air but does not specifically prevent food and fluid bolus from entering the lower respiratory system during swallowing.

Correct Answer: A

Rationale: The correct answer is A because the partial pressure of oxygen decreases with increasing altitude due to the decrease in atmospheric pressure. At sea level, the atmospheric pressure is higher, resulting in a higher partial pressure of oxygen compared to the top of Mt. Everest. Choice B is incorrect because the partial pressure of oxygen is not higher at higher altitudes. Choice C is incorrect because the partial pressure of oxygen is not equal at sea level and Mt. Everest. Choice D is incorrect because the question specifically asks about the partial pressure of oxygen only, not the sum of partial pressures from other gases.