How to breathe? Respiratory mechanics and breathing pattern.

On theoretical grounds any given level of pulmonary or alveolar ventilation can be obtained at various absolute lung volumes and through many combinations of tidal volume, breathing frequency and inspiratory and expiratory timing. However, inspection of specific cases of newborn and adult mammals at rest indicates that the breathing pattern reflects a principle of economy oriented toward minimal respiratory work. The mechanisms that permit optimization of respiratory cost are poorly understood; yet, it is their efficiency and coordination that permits pulmonary ventilation at rest to require only a minimal fraction of resting metabolism. The sensitivity of the breathing pattern to the mechanical properties implies that tidal volume, breathing rate, mean inspiratory flow or other ventilatory parameters cannot be necessarily considered indicators proportional to the central neural respiratory 'drive'. The broad conclusion is that the breathing pattern adopted by newborn and adult mammals is the one that produces the adequate alveolar ventilation with minimal cost, that is, in full recognition of the mechanical characteristics of the system.