A little practice will fix the rhythm, so that you will be able to easily reproduce it.

The beginner usually inhales in about six pulse units, but he will be able to greatly increase this by practice.
The Yogi rule for rhythmic breathing is that the units of inhalation and exhalation should be the same, while the units for retention and between breaths should be one-half the number of those of inhalation and exhalation.
The following exercise in Rhythmic Breathing should be thoroughly mastered, as it forms the basis of numerous other exercises, to which reference will be made later.
(1) Sit erect, in an easy posture, being sure to hold the chest, neck and head as nearly in a straight line as possible, with shoulders slightly thrown back and hands resting easily on the lap.

In this position the weight of the body is largely supported by the ribs and the position may be easily maintained.

The Yogi has found that one cannot get the best effect of rhythmic breathing with the chest drawn in and the abdomen protruding.
(2) Inhale slowly a Complete Breath, counting six pulse units.
(3) Retain, counting three pulse units.
(4) Exhale slowly through the nostrils, counting six pulse units.
(5) Count three pulse beats between breaths.
(6) Repeat a number of times, but avoid fatiguing yourself at the start.
(7) When you are ready to close the exercise, practice the cleansing breath, which will rest you and cleanse the lungs.
After a little practice you will be able to increase the duration of the inhalations and exhalations, until about fifteen pulse units are consumed.

In this increase, remember that the units for retention and between breaths is one-half the units for inhalation and exhalation.
Do not overdo yourself in your effort to increase the duration of the breath, but pay as much attention as possible to acquiring the "rhythm," as that is more important than the length of the breath.
Practice and try until you get the measured "swing" of the movement, and until you can almost "feel" the rhythm of the vibratory motion throughout your whole body.