The design and evaluation of the P₀.₁ method of assessing ventilatory drive
type: CreativeWork
description: Hypercapnia and/or hypoxia normally cause hyperventilation, The sensitivity to hypercapnia and hypoxia and the resultant hyperventilation is reduced in a patient suffering from damped respiratory centre activity. The P 0.1 method is a modification of the rebreathing technique where a patient rebreathes from a bag prefilled with a mixture of gases of known concentrations. This modification is not sensitive to airflow obstruction as is the case with the ventilatory response of the rebreathing technique. The P 0.1 method has been described by several authors during the past 8 years. There is however the need to standardise the technique. This thesis is an attempt to meet this need. The P 0.1 method involves the occlusion of the inspiratory airway for a set time after the onset of inspiration of a particular breathing cycle. The pressure (P 0.1) at this time, generated by the isometric contraction of the respiratory muscles, is recorded together with the end tidal P C02 . The valve is occluded approximately 20 times during a rebreathing trial lasting for 4 minutes. The plot of P 0.1 versus P C02 is linear and its slope gives an indication of respiratory centre activity. A low slope indicates damped respiratory centre activity. The control electronics was designed using digital logic. The occlusion valve is closed passively during the expiratory phase and then actively held for a preselected time, most frequently for 1OOms, after the onset of inspiration, during the next breathing cycle. The active occlusion period is preselectable between 50ms and 300ms. The inspiratory pressure is recorded at this time, or 10 or 20ms prior to the opening of the valve, by a sample and hold circuit. The occlusion valve can be triggered manually via a push button switch on the front panel, or periodically for preselectable periods every 5 to 30 seconds or pseudo-randomly. Ventilatory phase, pressure preset and autotrigger mode indicators are included as operator aids. In a limited number …
abstract: Hypercapnia and/or hypoxia normally cause hyperventilation, The sensitivity to hypercapnia and hypoxia and the resultant hyperventilation is reduced in a patient suffering from damped respiratory centre activity. The P 0.1 method is a modification of the rebreathing technique where a patient rebreathes from a bag prefilled with a mixture of gases of known concentrations. This modification is not sensitive to airflow obstruction as is the case with the ventilatory response of the rebreathing technique. The P 0.1 method has been described by several authors during the past 8 years. There is however the need to standardise the technique. This thesis is an attempt to meet this need. The P 0.1 method involves the occlusion of the inspiratory airway for a set time after the onset of inspiration of a particular breathing cycle. The pressure (P 0.1) at this time, generated by the isometric contraction of the respiratory muscles, is recorded together with the end tidal P C02 . The valve is occluded approximately 20 times during a rebreathing trial lasting for 4 minutes. The plot of P 0.1 versus P C02 is linear and its slope gives an indication of respiratory centre activity. A low slope indicates damped respiratory centre activity. The control electronics was designed using digital logic. The occlusion valve is closed passively during the expiratory phase and then actively held for a preselected time, most frequently for 1OOms, after the onset of inspiration, during the next breathing cycle. The active occlusion period is preselectable between 50ms and 300ms. The inspiratory pressure is recorded at this time, or 10 or 20ms prior to the opening of the valve, by a sample and hold circuit. The occlusion valve can be triggered manually via a push button switch on the front panel, or periodically for preselectable periods every 5 to 30 seconds or pseudo-randomly. Ventilatory phase, pressure preset and autotrigger mode indicators are included as operator aids. In a limited number …
author: Gajjar, Narendrakumar Chhotalal
keywords: Biomedical Engineering, Ventilators, Mechanical
date published: 1983
date modified: 2026-07-22T22:23:06Z
provider: University of Cape Town
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Division of Biomedical Engineering

PropertyValue
property ID: Handle
value: http://hdl.handle.net/11427/30551