Intra-pleural pressure is clinically estimated by measuring intra-esophageal pressure. The potential for three brands of four French Gauge (FG) size Polyvinyl chloride (PVC) fluid-filled catheter manometer systems (CMS) to measure intra-esophageal pressure accurately was quantified by determining their in vitro resonance frequency properties. All CMS were underdamped and resonated. No CMS exhibited a uniform mean frequency response above 11 Hz. Large FG catheters exhibited the potential to measure dynamic intra-esophageal pressure up to 82 breaths/min maximally within a 5% error limit. Significant differences in measurement accuracy existed between catheter FG sizes and between catheters of similar diameters but differing brands. In conclusion, in the absence of sharp inspiratory waveforms or high respiratory rates, intra-esophageal PVC catheters should accurately measure transmitted pleural pressures. Quantitative frequency response characterisation of various nasogastric catheter brands and sizes is desirable.
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