Endoscopic intratracheal carbon dioxide measurements during pediatric flexible bronchoscopy

BACKGROUND: CO2 monitoring is recommended for thoracic telescopic procedures and for spontaneous breathing general anesthesia in children. During flexible bronchoscopy (FB) in children, the various currently available methods of CO2 measurements are limited. The CO2 falls and increases have been reported in FB but it is unknown whether airway lesions predispose to CO2 change. The aim of this study was to describe and validate endoscopic intratracheal CO2 measurements in children undergoing FB under spontaneously breathing GA. METHODS: Endtidal CO2 (P(E)CO2) measurements at the start (Start-CO2) and end (End-CO2) of FB on 100 consecutive children were performed using a newly designed endoscopic intratracheal method. To validate the method blood gas sampling was simultaneously performed in 28 children and results analyzed using the Bland and Altman method, intraclass correlation and 95% range for repeatability. RESULTS: End-CO2 and CO2-change (End-CO2 minus Start-CO2) were significantly different in children with airway lesions (CO2 change: no lesion = 3 mmHg, extrathoracic airway lesion = 4.5, intrathoracic airway lesion = 8, P = 0.038). There was no significant difference in Start-CO2 values among the groups. CO2-change in those aged < or =12 months was similar to those >12 months. Intratracheal CO2 measurements were comparable with arterial blood values in the Bland and Altman plots. The intraclass correlation was 0.69 and 95% range for repeatability was 3.7-4.17 mmHg. CONCLUSIONS: Midtracheal P(E)CO2 provides a useful estimate of P(a)CO2 for monitoring the respiratory status of children undergoing FB. The presence of airway lesions rather than age is associated with significant increased PCO2 rise.     

Influence of Pulse Oximetry and Capnography on Time to Diagnosis of Critical Incidents in Anesthesia: A Pilot Study Using a Full-Scale Patient Simulator

Objective. Many studies (outcome, epidemiological) have tested the hypothesis that pulse oximetry and capnography affect the outcome of anesthetic care. Uncontrollable variables in clinical studies make it difficult to generate statistically conclusive data. In the present study, we eliminated the variability among patients and operative procedures by using a full-scale patient simulator. We tested the hypothesis that pulse oximetry and capnography shorten the time to diagnosis of critical incidents. Methods. A simulator was programmed to represent a patient undergoing medullary nailing of a fractured femur under general anesthesia and suffering either malignant hyperthermia, a pneumothorax, a pulmonary embolism or an anoxic oxygen supply. One hundred thirteen anesthesiologists were randomly assigned to one of two groups of equal size, one with access to pulse oximetry and capnography data and the other without. Each anesthesiologist was further randomized to one of the four critical incidents. Each anesthetic procedure was videotaped. The time to correct diagnosis was measured and analyzed. Results. Based on analysis of 91 of the subjects, time to diagnosis was significantly shorter (median of 432 s vs. >480 s) for the anoxic oxygen supply scenario (p = 0.019) with pulse oximetry and capnography than without. No statistical difference in time to diagnosis was obtained between groups for the other three critical incidents. Conclusions. Simulation may offer new approaches to the study of monitoring technology. However, the limitations of current simulators and the resources required to perform simulator-based research are impediments to wide-spread use of this tool.     

Linking mass spectrometers to provide continuing monitoring during system failure

Although multipatient monitoring with a timeshared mass spectrometer provides considerable cost advantages, failure of one component in a shared system can disrupt gas monitoring at all sites. We describe a simple method for linking two central mass spectrometer systems to provide continual monitoring during failure of one unit, without the need for time-consuming reconfiguration of individual patient sample line and display connections.     

Capnography for detection of endobronchial migration of an endotracheal tube

A patient is described in whom migration of an endotracheal tube into the right main bronchus was suspected when end-tidal carbon dioxide suddenly decreased from 28 to 22 mm Hg. Acute changes with migration of the endotracheal tube into the main bronchus were also studied in an animal experimental model. End-tidal carbon dioxide decreased and tracheal (inflation) pressure increased, with no change in tidal volume. Arterial blood gases showed time-dependent decreases in pH and oxygen tension and an increase in carbon dioxide tension.     

Single breath end-tidal CO2 estimates of arterial PCO2 in infants and children

To determine whether single breath end-tidal carbon dioxide (PE'CO2) measurements accurately estimate arterial PCO2 (PaCO2) in infants and children, 68 healthy infants and children, ASA physical status I or II scheduled for peripheral and lower abdominal surgery requiring endotracheal intubation were studied. A 3 ml single breath sample was obtained with a 23-gauge needle which was inserted through the wall of the endotracheal tube below the connector. The mean +/- SD PE'CO2 33.6 +/- 6.9 mmHg did not differ significantly from the corresponding mean +/- SD PaCO2 33.6 +/- 5.6 mmHg. The coefficient of determination, r2, was 0.97. The authors conclude that single breath PE'CO2 measurements from the proximal end of the endotracheal tube accurately estimate the PaCO2 in infants and children.     

Microstream capnograpy technology: a new approach to an old problem

Significant technical limitations inherent in blackbody infrared technology used in conventional sidestream and mainstream capnography have hindered the acceptance and growth of capnography as a monitoring tool outside the operating room environment. We describe a new technology (Microstream) for CO₂ monitoring, based on molecular correlation spectroscopy, which results in a highly efficient and selective emission of a spectrum of discrete wavelengths exactly matching those for CO₂ absorption. The CO₂ specific emissions allow for an extremely small sample cell (15 µl), which in turn, permits the use of a very low sample flow rate (50 ml/min) without compromising waveform integrity or end-tidal CO₂ accuracy. Design and technology features of the CO₂ emission source, sample cell, and breath sampling circuits are described.     

呼出气CO_2容积曲线诊断COPD换气功能障碍的评价

目的评价无创肺换气肺功能诊断技术即呼出气CO2容积曲线诊断慢性阻塞性肺病(COPD)换气功能障碍的准确度及影响因素。方法采用病例对照研究。对照组94人,COPD组201例,主要分析参数:CO2max%、dC/dV3(%)、Vm25-50/VT、Vm50-75/VT。与常规肺功能各参数进行相关分析,比较四项主要诊断指标敏感度、特异度。结果VD-B(ml)、VD-B/VT、Vm25-50/VT、Vm50-75/VT、CO2max(%)、dC/dV2(%)、dC/dV3(%),两组比较差异有显著性意义(P<0.01);Vm25-50/VT、Vm50-75/VT、CO2max、dC/dV3与FVC、FEV1、DLCO、RV/TLC等常规肺功能指标中度相关(r=-0.4￣-0.6,P<0.01);Vm50-75/VT敏感度和特异度高于其它指标。结论(1)COPD患者VCap曲线形态异常,Ⅲ相斜率[dC/dV3(%)]明显增高且与阻塞严重程度相关。(2)变量Vm50-75/VT、Vm25-50/VT受生理因素及通气量的影响少,与常规肺功能指标显著相关,特别是DLCO功能(r=-0.566,-0.511,P<0.01)作为评价中、重度COPD换气功能障碍、通气/血流灌注失调指标,敏感度86%、特异度91%、准确度90%,能很好地区别正常对照组和COPD阻塞严重程度。(3)VCap方法简便快速、安全无创、患者依从性高、重复性好。(4)频数分布曲线与对照组有重叠,建议取最佳临界点为正常参考值。     

支气管哮喘患者容积二氧化碳图改变的研究

目的 探讨容积二氧化碳图参数在支气管哮喘诊疗方面的临床价值.方法 对34例支气管哮喘急性发作期患者在治疗前后及20例健康者进行肺通气功能以及容积二氧化碳图测定.所有受试者首先进行容积二氧化碳图测定,随后完成肺通气功能测定.结果 肺通气功能检测FEV1/pre、FEV1/FVC、PEF/pre、MMEF/pre 支气管哮喘组较对照组明显下降,容积二氧化碳图参数dC2/DV支气管哮喘组较对照组下降,dC3/DV及SR23支气管哮喘组较对照组显著增大,差异有统计学意义(P＜0.05);支气管哮喘组治疗后较治疗前肺通气功能检测FEV1/pre、FEV1/FVC、PEF/pre、MMEF/pre显著升高,容积二氧化碳图检测dC2/DV增大,dC3/DV及SR23明显下降,差异有统计学意义(P＜0.05);治疗前后dC2/DV、dC3/DV及SR23与FEV1/pre、FEV1/FVC、PEF/pre、MMEF/pre有显著的相关性.结论 容积二氧化碳图是一种定量评估支气管阻塞严重性的有效方法,它简便易行且只需潮气呼吸即可测得,可应用于支气管哮喘的临床诊断及疗效观察等.