"Residual volume" is the name given to the volume of air remaining in the lungs once a respiratory cycle is completed, giving way to a new cycle.

The "residual volume" represents the mass of air which fills up the lungs once the new-born adapts himself to the physic-natural world during the transcendental act of birth, after which the cyclic phenomena known as respiration begins. Therefore, the "residual volume" represents the Initial Volume-mass from the ontogenetic point of view; being renewed by successive inspirations of a volume-mass of air known as "tidal volume", while the first named is used and exhausted.

It is deduced from the above, that the "residual volume" or Initial volume is the mechanical factor in Nature (mass of air from the environment) necessary to put into motion the organic mechanism designed to renew the gases in the blood, with the air thus supplying organic needs.

The inspired volume-mass of air (Tidal volume), to be used at the alveoli-capillary level, is pressurised and acclimatised while ít circulates throughout the airways; hence, it is not used during the same cycle in which is inhaled, but rather when the previously-inhaled air is exhausted.



I. "The Primary Inspiratory Reflex" (Vagal reflex) starts the ventilatory cycle by broncho-constriction, which results in the reduction of the diameter and length of the airways, with four main consequences:

1. Diminishing of airway capacity, with a consequent increase in contained air pressure.

2. Displacement of the "residual volume" towards the pulmonary periphery.

3. Traction of the thoracic wall (diaphragm and costal wall), by means of pleural adhesion.

4. Increase in the pleural diameters.

II. Traction of the diaphragm evokes the "Pulmo-diaphragmatic Reflex" (phrenic reflex) for diaphragm contraction, which, when flattening its dome, diminishes the resistance to expansion of the previously pressurised gases in the airways, favouring displacement of the lungs towards the abdomen. At the same time, the "tidal volume-mass" begins to penetrate the lungs.

III. On termination of the vagus action potential evoked by the inspiratory Reflex, the bronchial muscles relax and the pressurised gases expand, aided by diaphragm contraction, which diminishes the resistance. The final portion of the tidal-volume-mass then enters the lungs.

Inspiration is now complete. The diaphragm has achieved maximal contraction, with maximum traction of the costal arch, evoking the "Costo-diaphragmatic Reflex" (Intercostal reflex).

IV. The lungs begin their elastic retraction (reaction) following the route generated by costal expansion. When both the lungs and the costal walls reach the end of their displacement, in opposite senses, the resulting stretching of the airway receptors evokes a new inspiratory reflex to start a new ventilatory cycle.



Simultaneously with the events describes above, the pulmonary respiratory zone (or lobular zone), is the site of a succession of cyclic events, with lobular-cardiac rhythm, for gas interchange with the blood. These events or "Lobular alveoli-capillary cycles" lead to the consumption of a mass of air during each alveoli-capillary cycle, which diminishes the mass of the remaining gas in the lungs in the same measure. The "tone reflex" balances the pressure of the remaining mass of air since the dynamics for gas interchange demands a very well defined gas pressure at the alveoli-capillary level.

When a mass of air similar to the tidal volume-mass is used and exhausted, the dynamic conditions in the respiratory apparatus are similar to those at the beginning of the same cycle, and a new ventilatory cycle will consequently follow.




The Volume-mass of inspired air is an expression, which emphasises the physic-natural factors of the air, required for pulmonary respiration as a dynamic biological function, related to the adaptation of the individual to the surrounding atmosphere.

Atmospheric air has a uniform percentage of the component gases, and a density relative to geographical level, as a consequence of Universal Gravitation.

The adaptation of living organisms to the atmosphere is primarily in relation to the molecular density of the inspired air, which gives its inertial properties to the air; therefore, organic life adapts to levels of altitude within limits of displacement compatible with organic potentialities.

We inspire a volume-mass of air, which is predetermined by the organic capacity of the respiratory tree and by the organic potentialities to determine changes in volume through bronchi-constriction-relaxation. This is related to organic programme and is accomplished by means of reflexes whose results are a mathematical product given by the force potential to determine a degree of contraction. This contraction concerns, in turn, with the reduction of sectorial airways capacity, and hence, with the increase of the "mass" of air per unit-volume which afterwards expands, when bronchi-relaxation is produced, thus accomplishing air circulation throughout the respiratory tree, and finally delivering ít to the alveoli.

The physiological "Reflex-Programme" has as its objective the increase in gas pressure, to first accumulate and then liberate energy for the intra-pulmonary air circulation, lastly, to supply the alveoli with a mass of air relative to their capacity. This happens in such a way that the new pressure acquired by the air in the alveoli can equilibrate capillary blood pressure, allowing the steady selective diffusion of gases, in the required proportions, through the alveoli-capillary membrane.

This organic behaviour defines the functional equilibrium of living beings at birth and at the different levels of adaptation.




1. The rigorously reasoned analysis of the dynamic manifestations attributed here to the lobuli, as specific functional units of the lungs for gas interchange with the blood.

2. The complexity of the dynamic events made evident in the "Lobular Pulse" when compared with the simplicity of the arterial pulse.

3. The fact that the highest pressure-peak shown in the "Lobular Pulse", (attributed here to the expansive force of the air pressurised by bronchi-lobular constriction), coincides with the cardiac diastole, while the second highest pressure-peak (relative to the "Alveoli-capillary Pulse), coincides with the cardiac systole.

4. The fact that the cyclic increase in pressure coincides with active retraction of the pulmonary structure followed by relaxation, and a consequent widening-narrowing of the pleural diameter (as deduced from the analysis of intra-pleural pressure variations). This widening-narrowing of the pleural diameter is concerned with alveoli-capillary retraction-expansion.

Finally, incontrovertible evidence is offered by the following two complementary experimental observations.

5. When cardiac arrest is produced, by electrical stimulation of the vagus nerve or throughout the effect of Curare-injection, the arterial pulse disappears, while the lobular pulse remains present for about three more minutes, after which arterial pulses re-appear, or the dog dies.

6. When respiratory arrest is produced, the arterial pulses remain present and may even be elevated, and there is no manifestation of pulmonary activity in the corresponding Respiratory Pulse graph.


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