Methods and apparatuses are described for direct rapid measurement of pulmonary flow resistance. A measurement of a first pressure in a gas-tight chamber is received from a pressure sensor when a gas output port of the chamber is closed, a patient is blowing into a gas inlet of the chamber at a given pressure, and a gas-flow path between the inlet and output port has a resistance value. A measurement of a second pressure in the chamber is received from the pressure sensor and a measurement of gas flow through the chamber is received from a gas flow sensor when the output port is opened and the patient is blowing into the inlet to maintain the given pressure relatively constant. A pulmonary flow resistance is computed based upon the measurement of the first pressure, the measurement of the second pressure, the resistance value, and the measurement of gas flow.