Variation in barometric pressure in Melbourne does not significantly affect the BTPS correction factor

Area of Science:

• Pulmonary Physiology
• Medical Instrumentation

Background:

• The body temperature and pressure, saturated with water vapour (BTPS) correction factor is crucial for accurate lung function testing.
• This factor conventionally varies with ambient barometric pressure (P(B)), necessitating daily P(B) measurements in many laboratories.

Purpose of the Study:

• To evaluate if a fixed barometric pressure (P(B)) value can replace daily measurements for BTPS correction.
• To determine the potential error introduced by using a standard P(B) instead of daily measurements.

Main Methods:

• Daily P(B) was recorded over a 12-month period in Melbourne.
• Historical P(B) extremes from the Bureau of Meteorology were analyzed.
• BTPS factors were calculated using measured P(B) and a fixed P(B) of 101.3 kPa across various spirometer temperatures.

Main Results:

• The mean P(B) over 12 months was 102.2 kPa (SD 0.64), with a range of 99.9-103.6 kPa.
• Disagreement in BTPS factors was slightly greater at lower spirometer temperatures when using a fixed P(B).
• Using a standard P(B) of 101.3 kPa resulted in a maximum error of ≤0.16% even across extreme historical P(B) values (98.0-104.3 kPa).

Conclusions:

• Daily variations in ambient barometric pressure (P(B)) have a negligible impact on the BTPS correction factor.
• A fixed P(B) value, such as 101.3 kPa, is suitable for routine use in lung function laboratories, simplifying procedures and reducing potential errors.