Breathing pattern in humans: diversity and individuality

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Abstract

In adult awake human subjects at rest, there exists a diversity in the breathing pattern not only in terms of tidal volume and inspiratory and expiratory duration and derived variables (Ttot, Vt/Ti and Ti/Ttot) but also in the airflow profile. Besides this diversity, in every recording of ventilation at rest in steady-state condition breath-to-breath fluctuations are observed in ventilatory variables. This variability is non random and may be explained either by a central neural mechanism or by instability in the chemical feedback loops. Beyond this variability, each individual appears to select one particular pattern among the infinite number of possible combination of ventilatory variables and airflow profile. This one particular pattern appears to be a relatively stable characteristic of an adult individual being reproducible in several conditions and above all, after a long period of time. Consequences of this individuality of breathing pattern are discussed with regard to the selection of control subjects for a study and also per se: are there physiological situations where differences may be observed solely because of the differences in the pattern of breathing?

Section snippets

Breathing frequency

The earliest data available on spontaneous breathing frequency values are those of Quetelet (1842) on 300 subjects and of Hutchinson (1850) on 1714 adult subjects. These data appear to be the most extensive so far published and show the very wide frequency range (between 6 and 31 breaths per minute) observed in adults. In addition, they have the merit of being obtained by observation and thus not being altered by the use of any measuring device.

The large range of breathing frequencies observed

Breath-to-breath variations in the pattern of breathing

Priban (1963) was the first to demonstrate that the breath-to-breath fluctuations in respiratory cycle variables were not purely random. He concluded that, “it is not unlikely that some system would be able to compare one breath to its predecessor and adjust it or the following one with respect to frequency and volume and so produce the observed pattern of breathing”.

Using mainly time-series analyses and statistical models, several studies confirmed the non random nature of the fluctuations of

Individuality of breathing pattern

The existence of the individuality of the breathing pattern has been observed by all the investigators who have had to perform several recordings on one subject. Thus, from the observation of pneumotachograms, Proctor and Hardy (1949) reported that “the comparison of consecutive cycles or cycles taken on different days from records on any single subject impresses one with the consistency with which an individual pattern is reproduced”. Morrow and Vosteen (1953) confirmed these observations and

How are control subjects to be chosen?

In most studies on ventilatory changes, control experiments are carried out on subjects matched by age, weight and sex. Given the diversity of the breathing pattern the question arises as to whether this age and morphology matching yields adequate control subjects.

It has not been clearly established whether in adult human subjects, there is a relationship between these characteristics and the components of the breathing pattern. Jammes et al. (1979) reported a study on 235 subjects of both

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