Hartford C G, Rogers G G, Turner M J
Department of Physiology, University of Witwatersrand, Johannesburg, South Africa.
Pediatr Pulmonol. 1997 May;23(5):362-9. doi: 10.1002/(sici)1099-0496(199705)23:5<362::aid-ppul8>3.0.co;2-m.
Polyvinyl chloride (PVC) nasogastric feeding catheters are used clinically to measure intraesophageal pressure as an estimate of pleural pressure for calculating lung compliance in infants. The accuracy of pressure measurement of 4 French gauge (FG) catheter sizes and three brands of liquid-filled catheter manometer systems (CMS) was evaluated by determining their resonance-frequency amplitude and phase properties. All CMS were underdamped and resonated. No CMS exhibited a uniform mean frequency response above 11 Hz. The maximum respiratory rate (Frr) within which CMS could potentially measure dynamic intraesophageal pressure within a 5% error limit was determined (Frr): the highest mean Frr recorded reliably in large-diameter catheters was 82 breaths/min. Significant CMS differences in accuracy existed between catheter FG sizes and between catheters of similar diameters but differing brands. Correlation (r2) between catheter inner diameter and CMS Frr was 0.66 across brands. In conclusion, intraesophageal PVC liquid-filled feeding catheters are suitable for estimating pleural pressures in subjects mechanically ventilated without sharp inspiratory waveforms or high respiratory rates. Quantitative frequency response characterization of different nasogastric catheter brands and different diameters is mandatory prior to their utilization.
聚氯乙烯（PVC）鼻胃饲管在临床上用于测量食管内压力，以估计胸膜压力，从而计算婴儿的肺顺应性。通过测定4法式规格（FG）导管尺寸和三个品牌的充液导管压力计系统（CMS）的共振频率幅度和相位特性，评估了它们压力测量的准确性。所有CMS均为欠阻尼且发生共振。没有CMS在11 Hz以上表现出均匀的平均频率响应。确定了CMS能够在5%误差限度内潜在测量动态食管内压力的最大呼吸频率（Frr）：大直径导管中可靠记录的最高平均Frr为82次/分钟。导管FG尺寸之间以及直径相似但品牌不同的导管之间，CMS在准确性方面存在显著差异。不同品牌导管内径与CMS Frr之间的相关性（r2）为0.66。总之，食管内PVC充液饲管适用于估计机械通气且无尖锐吸气波形或高呼吸频率患者的胸膜压力。在使用不同鼻胃管品牌和不同直径的导管之前，必须对其进行定量频率响应特征分析。
