A prediction-correction scheme for forcing alveolar gases along certain time courses

Robbins, Peter A.; Swanson, George D.; Howson, M. G.

doi:10.1152/jappl.1982.52.5.1353

Cited by 147 publications

(96 citation statements)

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“…For the measurements at 0, 4 and 8 h that required the rapid variation in PET,Oµ of Fig. 1, a dynamic end-tidal forcing system (Robbins et al 1982;Howson et al 1987) was used that required the subjects to breathe through a mouthpiece while wearing a noseclip. Further details of the gas regulation techniques for the present study are given in Clar et al (1999).…”

Section: Gas Controlmentioning

confidence: 99%

Cardiovascular effects of 8 h of isocapnic hypoxia with and without beta-blockade in humans

Clar¹,

Dorrington²,

Fatemian³

et al. 2000

Exp. Physiol.

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Section: Gas Controlmentioning

confidence: 99%

Cardiovascular effects of 8 h of isocapnic hypoxia with and without beta-blockade in humans

Clar¹,

Dorrington²,

Fatemian³

et al. 2000

Exp. Physiol.

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“…During measurements of VIWM and HR, end-tidal gas was regulated using a computer-controlled fast gas-mixing system which has been described in detail elsewhere (Robbins, Swanson & Howson, 1982; Howson, Khamnei, McIntyre, O'Connor & Robbins, 1987). This system required the subject to wear a nose-clip and breathe through a mouthpiece arrangement, which consisted of a turbine volume transducer (SensorMedics VMM Series, CardioKinetics Ltd, Salford, UK) to measure respiratory volumes and a pneumotachograph (Fleisch, Switzerland) to record respiratory flows and timing information.…”

Section: Subjectsmentioning

confidence: 99%

Effects of 8h of eucapnic and poikilocapnic hypoxia on middle cerebral artery velocity and heart rate in humans

Clar

Pedersen²,

Poulin³

et al. 1997

Experimental Physiology

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SUMMARYThis study examines the effects of prolonged hypoxia, with and without control of end-tidal CO2 partial pressure (PET,CO2), on the intensity-weighted mean velocity of blood flow in the middle cerebral artery (VIwM) and on heart rate (HR). Specifically, the time course of the responses, their reversibility with brief periods of hyperoxia and the recovery phase following prolonged hypoxia were all investigated. Twelve subjects were studied, of whom nine provided satisfactory data. A purpose-built chamber was used for the prolonged control of the end-tidal gases, and an end-tidal forcing system was used for generating the brief variations in end-tidal gases. Three 16 h protocols were employed: (1) 8 h eucapnic (average PET,CO, 39 mmHg) hypoxia (end-tidal 02 partial pressure, PETO, = 55 mmHg) followed by 8 h eucapnic euoxia (PETO2 = 100 mmHg); (2) 8 h poikilocapnic (average PET,Co2 4 mmHg below eucapnia) hypoxia (PET,02 = 55 mmHg) followed by 8 h poikilocapnic euoxia (PET,O0 = 100 mmHg); and (3) control (air inspired throughout). VIwM (using Doppler ultrasound) and HR were measured during brief exposures to hypoxic/euoxic and hyperoxic conditions with PET,CO, held 1-2 mmHg above eucapnia, at 0, 20, 240 and 480 min in the first 8 h, and at the same times in the second 8 h. There were no significant trends in VIWM under hypoxic conditions for either hypoxic protocol (ANOVA) and no significant differences between the three protocols for VIwM in hyperoxia (ANOVA). In contrast to VIWM, there was a significant increase in HR over time during both hypoxic exposures (P < 0.01, ANOVA). HR increased to a similar extent for the two types of hypoxia, and there was some suggestion that HR remained elevated after the relief of hypoxia. The results suggest that, with the level of hypoxia employed, progressive changes in HR occur, but that this level and duration of hypoxia has little sustained effect on VIWM.

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“…An even higher success rate would probably be achieved with the computer-controlled method of Robbins, Swanson & Howson (1982) which is capable of inducing many special patterns of changes in alveolar gas.…”

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

The Journal of Physiology

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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.

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A prediction-correction scheme for forcing alveolar gases along certain time courses

Cited by 147 publications

References 0 publications

Cardiovascular effects of 8 h of isocapnic hypoxia with and without beta-blockade in humans

Cardiovascular effects of 8 h of isocapnic hypoxia with and without beta-blockade in humans

Effects of 8h of eucapnic and poikilocapnic hypoxia on middle cerebral artery velocity and heart rate in humans

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

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