Elsevier Pulmonary Questions with correct answers

A patient is placed on a 100% nonrebreathing mask. The SpO2 is 98%. Which statement best describes why oxygen saturation is not a 100%? a). Infiltrates from pneumonia are causing a ventilation-perfusion mismatch. b). The patient is experiencing a small pneumothorax, resulting in pulmonary shunting. c). This finding is attributable to normal physiologic shunting. d). The patient also has pulmonary hypertension and is therefore unable to use exogenous oxygen delivered by the mask. - correct answer c). This finding is attributable to normal physiologic shunting. The left atrium normally contains pure oxygenated blood, with a hemoglobin saturation level of 100%. The mixing of venous blood from the bronchial circulation with the oxygenated blood in the left atrium decreases the saturation of left atrial blood to a range between 96% and 99%. The dumping of venous blood into the left atrium is known as an anatomic shunt. The thebesian veins, which drain the right coronary circulation, are also responsible for the addition of venous blood to the left atrium. These two systems constitute the normal anatomic shunt, which comprises approximately 3% to 5% of the total cardiac output. What does the term anatomic dead space mean? a). The conducting airways of the pulmonary system b). The portion of ventilation that goes to unventilated alveoli c). The portion of total ventilation that participates in gas exchange d). The sum of wasted ventilation and physiologic dead space - correct answer a). The conducting airways of the pulmonary system Areas in the lungs that are ventilated but in which no gas exchange occur are referred to as dead space regions. The conducting airways are such a region and are referred to specifically as anatomic dead space.