2.3 | Monitoring of physiological parameters
During the experiment, electrocardiography, mean arterial blood
pressure, and the percentage of arterial hemoglobin oxygen saturation
(SpO2) were continuously measured via a monitor (M1205A
Omni-Care 24/24C, Hewlett Packard, Essex, MA, USA). Respiratory flow and
airway pressure were measured with a heated pneumotachograph coupled to
a differential pressure transducer (MP-45-16, Validyne, Kenilworth, NJ,
USA) and a pressure transducer (MP45-28, Validyne), respectively. The
tidal volume was integrated from the flow signal. These signals were
recorded by a recorder (TA11, Gould, Eastlake, OH, USA) and a data
acquisition system (PowerLab 16/30, ADInstruments Pty Ltd, Bella Vista,
NSW, Australia). Arterial blood gas levels were analyzed using an
autoanalyzer (OPTIMedical, Roswell, GA, USA). Alveolar-arterial oxygen
gradient (AaDO2) was calculated.