The function of the multispirometer and procedure to measure the ventilatory function by spirometry is to know how a person exhales or expels air with the objective to study and monitor the functioning of his/her lungs and many pathologies. By means of this method, the ventilatory function by spirometry is measured, and is capable of obtaining respiratory restriction and obstruction values of a patient. To perform the above mentioned method, an electronic spirometer provided with flow detector means, microprocessor control means to carry out calculations on the basis of measured data, and means associated to said microprocessor to store the measured results, to visualize the results and to compare the stored results, is used.