Precision and accuracy of Morgan ventilometers at continuous and sinusoidal flows

Area of Science:

• Physiological measurement
• Respiratory diagnostics

Background:

• The P.K. Morgan Mark II Ventilometer is utilized for measuring minute ventilation during oxygen consumption tests.
• This device incorporates a turbine transducer and a control/readout unit with either VENTX5A or VENTX6A programs.

Purpose of the Study:

• To evaluate the precision and accuracy of six P.K. Morgan Mark II Ventilometer devices.
• To assess device performance under both continuous and pulsatile flow conditions.

Main Methods:

• Six P.K. Morgan Mark II Ventilometer devices (one VENTX5A with two turbines, two VENTX6As each with two turbines) were tested.
• Accuracy was assessed against a 350 l Collins chain-compensated gasometer.
• Continuous and sinusoidal (pulsatile) flows were used, with calibration performed using a syringe rate.

Main Results:

• Excellent precision was observed, with coefficients of variation between 0-0.2%.
• Accuracy varied: VENTX5A showed 99.5-100.5% at 60-160 l.min-1 (continuous flow), while VENTX6As showed 99.3-102.1% at 60-200 l.min-1.
• Sinusoidal flow accuracy: VENTX5A ranged from 96.1-101.3% (15-200 l.min-1), improving to 98.1-101.3% above 80 l.min-1. VENTX6As showed 95.9-98.9%, improving to 96.9-98.5% when excluding low tidal volumes.

Conclusions:

• The P.K. Morgan Mark II Ventilometer demonstrates high precision in minute ventilation measurements.
• Device accuracy is significantly affected by the calibration syringe rate, the specific program (VENTX5A vs. VENTX6A), and the level of minute ventilation.