Which of the following measures atmospheric pressure in pounds per square inch (psi)?

The measure of atmospheric pressure in pounds per square inch (psi) is specifically identified as 14.7 lb/in². This value represents the standard atmospheric pressure at sea level in the imperial system, where one atmosphere is equivalent to 14.7 psi. This is an important concept in respiratory care as understanding atmospheric pressure is crucial for accurately interpreting pressures related to gas laws, ventilators, and other respiratory devices.

The other choices represent atmospheric pressure in different units. For instance, 760 mm Hg corresponds to the barometric pressure typically used in the metric system, while 101 kPa is another metric representation. The value of 33.9 ft H2O indicates pressure in terms of the height of a column of water, which is yet another different measurement system. Each of these units is important in their respective contexts, but when specifically referring to pressure in psi, 14.7 lb/in² is unequivocally correct.