Measurement of tidal volume using respiratory ultrasonic plethysmography in anaesthetized, mechanically ventilated horses.

The study investigates the use of Respiratory Ultrasonic Plethysmography (RUP) for measuring tidal volume in anaesthetized, mechanically ventilated horses, comparing its estimations with data from simultaneous spirometry.

Objective of the Study

• The study aimed to assess the effectiveness of Respiratory Ultrasonic Plethysmography (RUP) in estimating tidal volume in anesthetized, mechanically ventilated horses. The estimations were compared with spirometric measurements to determine the accuracy of RUP.

Methods and Approach

• The research was carried out as a prospective randomized experimental study on five horses that were anaesthetized twice (with one week interval) in different positions: lateral and dorsal recumbency.
• Nine ventilation modes were scheduled in a randomized order, with each lasting for 4 minutes. These modes involved different combinations of tidal volumes (8, 10, 12 mL kg(-1)) and positive end-expiratory pressures (PEEP) (0, 10, 20 cm H(2)O).
• Data from both spirometry and RUP were downloaded to personal computers for comparison. Linear regression analyses were performed using different subsets of data.
• RUP was calibrated against spirometry using a regression equation for all RUP signal values collectively as well as an individually determined best regression equation for each experiment separately.
• Bland-Altman analyses were carried out to assess the agreement between the two methods.

Results

• The findings indicated a robust correlation (R(2) = 0.81) between RUP and spirometric tidal volume when the combined RUP signal was used in lateral recumbency horses that were ventilated without PEEP.
• The bias (±2 standard deviation) dropped from 0 ±2.66 L to 0 ±0.87 L when RUP was collectively calibrated to individual data.

Conclusions

• The study concluded that Respiratory Ultrasonic Plethysmography (RUP) can be potentially used for measuring tidal volume during Intermittent Positive Pressure Ventilation (IPPV). However, for accurate results, individual calibration is required to maintain limits of agreement within ±20%.