Mean and breath‐by‐breath pattern of breathing in man during steady‐state exercise.

Section: Expirationmentioning

confidence: 99%

A quantitative description of the pattern of breathing during steady‐state CO₂ inhalation in man, with special emphasis on expiration

Cunningham¹,

Gardner²

1977

“…When VT is high the slopes of the VT, Tj and TE relations are at a maximum (Kay et al 1975) and the breath-by-breath variation gives rise to a lot of scatter that could mask any small trend that might underlie the mean values. However, other factors may be involved in some types of step: thus the gross changes seen at the off-transient in Fig.…”

Section: Patterningmentioning

confidence: 99%

“…For all subjects the data from each transition were plotted on the VT-TE-TI modified von Euler plot' (Kay, Petersen & Vejby-Christensen, 1975). There were no consistent patterns even within subjects; the changes in VE took the form primarily of changes in VT rather than of frequency, with TE varying, if anything, more than T1, and independently of it.…”

Section: Pattern Of Breathingmentioning

confidence: 99%

Dynamics of the ventilatory response in man to step changes of end‐tidal carbon dioxide and of hypoxia during exercise.

Macfarlane¹,

Cunningham²

1992

SUMMARY1. Four human subjects exercised in hypoxia (end-tidal partial pressure Of 02 (PET, 02) ca 55 Torr; heart rate ca 100-130 beats min-), and the contribution to the respiratory drive of the peripheral and central chemoreflex pathways have been separated on the basis of the latencies and the time courses of the responses to sudden changes of stimulus.2. The subjects were exposed to repeated end-tidal step changes in PCO2 of ca 3-3 5 Torr (at nearly constant PET, 02 ) and P02 (between ca 55 and 230 Torr) at three regions along the expiratory ventilation VE-PET°2 response line (hypocapnia, eucapnia, hypercapnia). The dynamics of the ventilatory responses were calculated using a two-compartment non-linear least-squares optimization method.3. The component of the response attributable to the peripheral chemoreflex loop may in some subjects contribute up to 75% of the ventilatory drive during mild hypocapnic hypoxic exercise and ca 72 % of the total gain following steps Of PET, CO, during hypoxic exercise. These data support the notion that the effectiveness of the peripheral chemoreceptor pathway is enhanced in moderate exercise.4. During hypoxic exercise, the time delays and time constants attributed to the peripheral chemoreflex pathways (ca 3-5 and 9 s respectively) and to the central chemoreflex pathways (ca 9-5 and 47 s respectively) are some of the shortest reported.5. The dynamics of the peripheral and central chemoreflex pathways appeared to be largely independent of each other.6. There was a notable absence of systematic change of inspiratory and expiratory durations during the step-induced transients.

“…Although humans show some flexibility in locomotor-respiratory coupling (Bechbache & Duffin, 1977;Bramble & Carrier, 1983;Paterson, Wood, Morton & Henstridge, 1986;Loring, Mead & Waggener, 1990), quadrupeds, notably horses, almost invariably take one breath per stride at canter and gallop over a wide range of speeds (Bramble & Carrier, 1983;Butler et al 1993b). At trot, a definite but rather variable and inconstant entrainment has also been observed in horses (Bramble 1989;Art, Desmecht, Amory & Lekeux, 1990;Lafortuna & Saibene, 1991 (Hey, Lloyd, Cunningham, Jukes & Bolton, 1966;Kay, Strange-Petersen & Vejby-Christensen, 1975b;Cunningham, Robbins and Wolff, 1986). This possibly results from respiratory control mechanisms geared to a principle of energy optimization (Otis, Fenn & Rahn, 1950;Mead, 1960;Priban & Fincham, 1965;Yamashiro, Dubenspeck, Lauritsen & Grodins, 1975 The expansion of this tube ranged from a minimum of 045 m to a maximum of 5.7 m. The minimum volume of the total VD thus obtained was 7-3 1 (fully compressed) and the maximum was 66-7 1 (fully extended).…”

mentioning

confidence: 99%

The effects of locomotor‐respiratory coupling on the pattern of breathing in horses.

Lafortuna

Reinach

Saibene

1996

1. To investigate the effect of locomotor activity on the pattern of breathing in quadrupeds, ventilatory response was studied in four healthy horses during horizontal and inclined (7 %) treadmill exercise at different velocities (1 4-6-9 m s-1) and during chemical stimulation with a rebreathing method. Stride frequency (fe) and locomotor-respiratory coupling (LRC)were also simultaneously determined by means of video recordings synchronized with respiratory events. 2. Tidal volume (VT) was positively correlated with pulmonary ventilation (VE) but significantly different linear regression equations were found between the experimental conditions (P < 0 0001), since the chemical hyperventilation was mainly due to increases in VT, whereas the major contribution to exercise hyperpnoea came from changes in respiratory frequency (fR).3. The average fR at each exercise level was not significantly different from f", although therewas not always a tight 1: 1 LRC. At constant speeds, fs was independent of the treadmill slope and hence the greater VE during inclined exercise was due to increased VT. 4. At any ventilatory level, the differences in breathing patterns between locomotion and rebreathing or locomotion at different slopes derived from different set points of the inspiratory off-switch mechanism. 5. The percentage of single breaths entrained with locomotor rhythm rose progressively and significantly with treadmill speed (P < 0 0001) up to a 1: 1 LRC and was significantly affected by treadmill slope (P < 0 001). 6. A LRC of 1: 1 was systematically observed at canter (10 out of 10 trials) and sometimes at trot (5 out of 14) and it entailed (i) a 4-to 5-fold reduction in both VT and fR variability, and (ii) a gait-specific phase locking of inspiratory onset during the locomotor cycle. 7. It is concluded that different patterns of breathing are employed during locomotion and rebreathing due to the interference between locomotor and respiratory functions, which may play a role in the optimization and control of exercise ventilation in horses.