Effect of resistive loading on variational activity of breathing

Am J Respir Crit Care Med. 1998 Jun;157(6 Pt 1):1756-63. doi: 10.1164/ajrccm.157.6.9704114.

Abstract

To examine the effect of resistive loading on variational activity of breathing, we studied 18 healthy subjects breathing at rest and with inspiratory resistive loads of 3 and 6 cm H2O/L/s, applied randomly for 1 h each. Compared with resting breathing, a resistive load of 3 cm H2O/L/s decreased the total variational activity of expiratory time (TE) and minute ventilation (V I), whereas a load of 6 cm H2O/L/s increased the total variational activity of inspiratory time (TI). Compared with the load of 3 cm H2O/L/s, the load of 6 cm H2O/L/s increased total variational activity of tidal volume (VT), TI, TE, and V I. Partitioning of the total variational activity revealed that these alterations were due to changes in the random uncorrelated fraction. Compared with rest, both the resistive loads of 3 and 6 cm H2O/L/s increased the number of breath lags displaying significant serial correlations ("short-term memory") of TI. Compared with rest, the load of 3 cm H2O/L/s increased the autocorrelation coefficient at a lag of one breath for VT and the load of 6 cm H2O/L/s increased the correlated fraction of variational activity of VT. Thus, three measures of correlated behavior-autocorrelation coefficient at a lag of 1 breath, "short-term memory," and the correlated fraction of total variational activity- increased with loading. In conclusion, resistive loading changed total variational activity according to the size of the load: the random fraction decreased with the smaller load but increased with the larger load; in contrast, correlated behavior increased with both loads. The different behaviors of random and correlated variability with loading may reflect different physiologic influences on respiratory control.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adult
  • Airway Resistance*
  • Carbon Dioxide / physiology
  • Female
  • Humans
  • Male
  • Middle Aged
  • Respiration / physiology*
  • Rest
  • Tidal Volume

Substances

  • Carbon Dioxide