Lung function measured by impulse oscillometry and spirometry following eucapnic voluntary hyperventilation: METHODS (1)
Twenty subjects (five women and 15 men) volunteered to participate in the present study, which was approved by the Marywood University Institutional Review Board (Pennsylvania, USA). Table 1 provides subject demographic data. Ten subjects (four women and six men) were considered AHR+ by a 10% or greater fall in FEVj following EVH, and 10 subjects (one woman and nine men) were considered AHR- by EVH. buy prednisone
The EVH protocol required subjects to breathe a compressed dry gas mixture (21% O2, 5% CO2, balance N2) at a predetermined rate (30 x FEVj) for 6 min. Gas flowed from a cylinder through a calibrated rotameter (1110 Series Flowmeter, Brooks Instruments, USA) to three 300 g reservoir bags via high-pressure tubing. From the reservoir bags, the gas was directed to the subject via a 35 mm breathing tube, two-way breathing valve and mouthpiece (Hans Rudolf, USA). Expired gas passed through a flow sensor and minute ventilation was recorded (Vmax Spectra, SensorMedics, USA). Inhaled gas during EVH was at laboratory temperature but completely dry. Ambient temperature, relative humidity and barometric pressure in the laboratory were 19.4±0.61°C, 16.1±3.22% and 722±7.8 mmHg, respectively.
Table 1 Subject demographics and per cent fall in forced expiratory volume in 1 s after eucapnic voluntary hyperventilation (mean ± SD)
|Fall in FEV1 (%)||7.5±2.59||30.6±14.03|