Method and apparatus to attain and maintain target arterial blood gas concentrations using ramp sequences

Abstract

An apparatus and method for controlling the end tidal partial pressure of a gas X in a subject's lung, and to the use of such an apparatus and method for research, diagnostic and therapeutic purposes, wherein the method consists of: obtaining input of a series of logistically attainable PetX values for a series of respective breaths: determining an amount of gas X required to be inspired by the subject in an inspired gas to target the PetX for each of said respective breaths: and controlling a gas delivery device to deliver the amount of gas in a volume of gas delivered to the subject in each of said respective breaths to target the respective PetX for that breath.

Description

FIELD OF THE INVENTION[0001]The present invention relates to an apparatus and method for controlling end tidal gas partial pressures in spontaneously breathing or ventilated subjects and to the use of such an apparatus and method for research, diagnostic and therapeutic purposes.BACKGROUND OF THE INVENTION[0002]Techniques for controlling end-tidal partial pressures of carbon dioxide, oxygen and other gases are gaining increasing importance for a variety of research, diagnostic and medicinal purposes. Methods for controlling end tidal pressures of gases have gained particular importance as a means for manipulating arterial levels of carbon dioxide (and also oxygen), for example to provide a controlled vasoactive stimulus to enable the measurement of cerebrovascular reactivity (CVR) e.g. by MRI.[0003]Conventional methods of manipulating arterial carbon dioxide levels such as breath holding, hyperventilation and inhalation of fixed concentration of carbon dioxide balanced with medical ...

AI Technical Summary

Benefits of technology

The patent describes a method for computing the amount of gas X that needs to be breathed in by a person to achieve a target concentration in their breath. This is done by using a device called a sequential gas delivery system, which delivers air in a specific order to the person's breath. By adjusting the estimated or measured values of certain parameters, the method can accurately target the target concentration of gas X in the breath. This allows for a flexible and effective method for adjusting the gas mixture given to a person to achieve specific objectives.

Problems solved by technology

Conventional methods of manipulating arterial carbon dioxide levels such as breath holding, hyperventilation and inhalation of fixed concentration of carbon dioxide balanced with medical air or oxygen are deficient in their ability to rapidly and accurately attain targeted arterial carbon dioxide partial pressures for the purposes of routinely measuring vascular reactivity in a rapid and reliable manner.

Previous attempts at controlling the end-tidal partial pressures of gases have failed to account for these complex dynamics, and have therefore produced mediocre results.

Furthermore, the ventilatory response to perturbations in the end-tidal partial pressures of gases is generally unpredictable and potentially unstable.

Therefore, any changes in the end-tidal partial pressures of gases are immediately challenged by a disruptive response in the alveolar ventilation.

Technically, such a system suffers from the same limitations as all negative feedback control systems an inherent trade-off between response time and stability.

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