Determination of physiological dead space in anaesthetized horses: a method-comparison study

Area of Science:

• Veterinary Anesthesia
• Respiratory Physiology
• Medical Device Evaluation

Background:

• Accurate determination of physiological dead space to tidal volume ratio (Vd/Vt_Bohr-Enghoff) is crucial for managing respiratory function in anesthetized animals.
• Traditional methods for Vd/Vt_Bohr-Enghoff determination can be complex or require specialized equipment.

Purpose of the Study:

• To compare the accuracy of the E-CAiOVX metabolic monitor with a custom-made mixing chamber for determining Vd/Vt_Bohr-Enghoff in horses.
• To assess the clinical applicability of the E-CAiOVX monitor in equine anesthesia.

Main Methods:

• A prospective clinical method-comparison study was conducted on 20 horses undergoing elective orthopedic procedures.
• Horses were anesthetized with isoflurane and mechanically ventilated. Arterial blood gases and mixed expired gas were analyzed.
• Vd/Vt_Bohr-Enghoff was calculated using the Enghoff modification of the Bohr equation for both methods.

Main Results:

• Forty-nine simultaneous measurements of Vd/Vt_Bohr-Enghoff were obtained.
• No clinically significant bias was observed between the E-CAiOVX metabolic monitor and the mixing chamber method.
• The limits of agreement (-0.022 ± 0.078) were within the predefined acceptable error of ≤ 10%.

Conclusions:

• The E-CAiOVX metabolic monitor demonstrated acceptable agreement with the mixing chamber method for Vd/Vt_Bohr-Enghoff determination.
• The E-CAiOVX metabolic monitor is a potentially suitable device for measuring Vd/Vt_Bohr-Enghoff in anesthetized horses.
• This finding supports the use of the E-CAiOVX monitor for real-time respiratory monitoring in equine anesthesia.