Breathing Frequency Changes at the Onset of Stepping in Human Infants

Abstract

Breathing frequency increases at the onset of movement in a wide rage of mammals including adult humans. Moreover, the magnitude of increase in the rate of breathing appears related to the rate of the rhythmic movement. We determined whether human infants show the same type of response when supported to step on a treadmill. Twenty infants (ages 9.7 Ϯ 1.2 mo) participated in trials consisting of sitting, stepping on the treadmill, followed by sitting again. Breathing frequency was recorded with a thermocouple, positioned under one naris and taped to a soother that the infant held in his/her mouth. A video camera, electrogoniometers, and force platforms under the treadmill belts recorded stepping movements. We found that the rate of breathing changed at the beginning of stepping. Most surprisingly, we found that when infants stepped at a frequency slower than their breathing frequency in sitting, the breathing frequency decreased. Average breathing frequency during stepping was positively correlated with stepping frequency. There was no evidence of entrainment between stepping and breathing. In conclusion, the rapid change in breathing frequency at the beginning of movement is functional in infants. The direction and magnitude of change in breathing is associated with the leg movements.

Passive limb movement augments ventilatory response to CO2 via sciatic inputs in anesthetized rats

“…This phase I response was followed by a quick (within 1 min) decline to a relatively constant level (17–30%) above the baseline (phase II). In comparison, although the pattern was similar, the peak response during phase I was higher (∼60%) and decline duration longer (several minutes) in humans (Gozal et al, 1996; Bell and Duffin, 2003; Noah et al, 2008). This quantitative discrepancy may be due to the differences in species, exercise modes (e.g., parallel moving vs. cycling), states (anesthetized vs. awake), and the stimulating frequency of the passive movements.…”

“…With respect to the respiratory pattern, the passive movements increased V̇E by elevating both V t and f r (Gozal et al, 1996). A recent study further pointed out that this hyperpnea primarily resulted from an elevation in f r since the fR but not V t responses were positively correlated with the passive moving frequency (Noah et al, 2008). PLM was first used by Harrison, et al (1932) and subsequently by others (Flandrois et al, 1967) in anesthetized dogs.…”

“…Previous studies in humans have shown that passive movement for 5 – 10 min brings about phasic V̇E responses characterized by an abrupt increase in V̇E followed by a gradual (several min) decline to a relatively constant level above the baseline (Dejours et al, 1959; Gozal et al, 1996; Bell and Duffin, 2003; Noah et al, 2008). With respect to the respiratory pattern, the passive movements increased V̇E by elevating both V t and f r (Gozal et al, 1996).…”

“…Passive limb movement (PLM) for 5–10 min has been applied in humans with a resultant phasic hyperpnea characterized by an abrupt increase in minute ventilation (V̇E) (phase I) at the onset of exercise followed by a decline to a steady level higher (phase II) than that during rest (Dejours et al, 1959; Gozal et al, 1996; Bell and Duffin, 2003; Noah et al, 2008). The hyperpnea was achieved by increasing both tidal volume (V t ) and respiratory frequency (f r ) (Gozal et al, 1996) with the latter reported to be closely correlated to the passive movement frequency (Noah et al, 2008). It is well documented that the hyperpnea by PLM is associated with hypocapnia in both awake humans (Dejours, 1964; Bell and Duffin, 2003) and anesthetized animals (Agostoni and D’Angelo, 1976).…”

Ventilation and Respiratory Mechanics

“…This hypothesis is largely unproven, but recent work in human infants (9 months) shows that the rhythm generated for stepping and/or its afferent feedback have strong influences on the rhythm generator for breathing (392). Noah et al (392) found that young infants change their rate of breathing within the first three breaths taken during stepping, indicating that the mechanisms underlying the rapid change in breathing at the beginning of rhythmic movement are functional at this age. Thus, the mechanisms responsible for the rapid adjustment of breathing frequency at the beginning of movement are functional early in life and may not necessarily be related to "learning."…”