Flow-Through Versus Sidestream Capnometry for Detection of End Tidal Carbon Dioxide in the Sedated Patient

Coronavirus disease 2019 in the pediatric emergency department: unique considerations in preparation and response

PURPOSE OF REVIEW

Pediatric Emergency Departments (PEDs) have experienced unique considerations throughout the coronavirus disease 2019 (COVID-19) pandemic. We review the adaptations and challenges surrounding the preparation and response for pediatric emergency patients, with a specific focus on operational modifications, evolving personal protected equipment (PPE) needs, protected resuscitation responses, clinical characteristics in children, and the unintended effects on children and youth.

RECENT FINDINGS

COVID-19 has thus far proven to have a milder course in children, with manifestations ranging from asymptomatic carriage or typical viral symptoms, to novel clinical entities such as 'COVID toes' and multisystem inflammatory syndrome in children (MIS-C), the latter associated with potentially significant morbidity. It has had an important effect on primary prevention, injury rates, reduced presentations for emergency care, and increased mental health, abuse and neglect rates in children and youth. PEDs have prepared successfully. The most significant adjustments have occurred with screening, testing, and consistent and effective use of PPE, along with protected responses to resuscitation, adaptations to maintain family-centered care, and technological advances in communication and virtual care. Simulation has been key to the successful implementation of many of these strategies.

SUMMARY

COVID-19 has pushed PEDs to rapidly adapt to evolving clinical and societal needs, with both resultant challenges and positive advances. Further experience and research will guide how in the face of a global pandemic we can further optimize the clinical and operational care of children and youth, ensure robust educational training programs, and maintain provider safety and wellness.

A Novel Nasal Cannula Type Mainstream Capnometer System Capable of Oxygen Administration

Capnometry is a method to measure carbon dioxide (CO₂) in exhaled gas and has been used to monitor patient's respiratory status. During moderate or deep sedation, monitoring for the presence of exhaled CO₂ is recommended for evaluating the adequacy of ventilation. Oxygen administration is usually given to patients with a nasal cannula to avoid hypoxia during sedation. However, the flow of oxygen administration can interfere with CO₂ measurement. We developed a nasal cannula type adapter called cap-ONE nasal adapter system based on the mainstream capnography which is designed to monitor CO₂ while supplying oxygen. In this study, we evaluated the basic performance of the system as compared with a conventional device using a spontaneous breathing model. The cap-ONE nasal adapter system could accurately measure PetCO₂ without being disturbed by oxygen flow and efficiently supply oxygen.

A Novel Mainstream Capnometer System for Non-invasive Positive Pressure Ventilation

Capnometry is a method to measure carbon dioxide (CO₂) in exhaled gas and it has been used to monitor patient respiratory status. CO₂ monitoring is also used for patients receiving non-invasive positive pressure ventilation (NPPV) therapy during mechanical ventilation. Ventilators actively dilute exhaled gas during non-invasive ventilation. In order to accurately measure end-tidal CO₂, an adequate amount of expired gas needs to be filled in a CO₂ measurement cell before expiratory positive airway pressure (EPAP) gas from the ventilator arrives to the cell. This is the reason why it is difficult to measure CO₂ stably during non-invasive ventilation using the conventional CO₂ measurement method. Therefore, we developed NPPV cap-ONE mask, which accurately measures CO₂ in exhaled gas during non-invasive ventilation. In this study, we evaluated the basic performance of the NPPV cap-ONE mask system. The NPPV cap-ONE mask system could accurately measure CO₂ in exhaled gas comparing to the conventional device in this study.

Novel mainstream capnometer system is safe and feasible even under CO2 insufflation during ERCP-related procedure: a pilot study

Background and aims

There is a need to safely achieve conscious sedation during endoscopic retrograde cholangiopancreatography (ERCP). We evaluated the safety and feasibility of a mainstream capnometer system to monitor apnoea during ERCP under CO₂ insufflation.

Methods

Non-intubated adult patients undergoing ERCP-related procedures with intravenous sedation were enrolled. End-tidal CO₂ (EtCO₂) was continuously monitored during the procedure under CO₂ insufflation using a mainstream capnometer system, comprising a capnometer and a specially designed bite block for upper gastrointestinal endoscopy and ERCP. Oxygen saturation (SpO₂) was also monitored continuously during the procedure. In this study, we evaluated the safety and feasibility of the capnometer system.

Results

Eleven patients were enrolled. Measurement of EtCO₂ concentration was possible from the beginning to the end of the procedure in all 11 cases. There was no measurement failure, dislocation of the bite block, or adverse event related to the bite block. Apnoea linked to hypoxaemia occurred five times (mean duration, 174.4 s).

Conclusion

This study confirmed that apnoea was detected earlier than when using a percutaneous oxygen monitor. Measurement of EtCO₂ concentration using the newly developed mainstream capnometer system was feasible and safe even under CO₂ insufflation.

Capnography Detection Using Nasal Cannula Is Superior to Modified Nasal Hood in an Open Airway System: A Randomized Controlled Trial

PURPOSE

The nasal cannula and modified nasal hood are methods used by oral and maxillofacial surgeons to detect expired carbon dioxide during procedural sedation in an open airway system. The purpose of this study was to compare the accuracy of the detection of expired carbon dioxide between the nasal cannula and modified nasal hood.

MATERIALS AND METHODS

The authors designed a parallel-group randomized controlled trial to compare the nasal cannula and modified nasal hood. Patients presenting to the authors' institution for outpatient oral and maxillofacial surgery (OMS) using intravenous deep sedation or general anesthesia were randomized to have capnography detection by the modified nasal hood or the nasal cannula. The primary outcome variable was the percentage of accurately captured breaths, as determined by the average number of capnography waveforms per auscultated breath using a precordial stethoscope. The 2 groups were compared using t test.

RESULTS

Fifty patients were screened for enrollment in the study. Twenty-five patients were randomized to the nasal cannula group and 25 patients were randomized to the modified nasal hood group. The proportion of accurate waveforms, recorded as a percentage of total breaths, was 95.7 ± 4.7% for the nasal cannula and 75.8 ± 14.1% for the modified nasal hood (P < .0001).

CONCLUSIONS

When used for capnography for procedural sedation in an open airway system for routine OMS, the nasal cannula accurately recorded more breaths than the modified nasal hood.

Evaluation of end-tidal carbon dioxide gradient as a predictor of volume responsiveness in spontaneously breathing healthy adults

Background

Methods to guide fluid therapy in spontaneously breathing patients are scarce. No studies have reported the accuracy of end-tidal CO₂ (ET-CO₂) to predict volume responsiveness in these patients. We sought to evaluate the ET-CO₂ gradient (ΔET-CO₂) after a passive leg rise (PLR) maneuver to predict volume responsiveness in spontaneously breathing healthy adults.

Methods

We conducted a prospective study in healthy adult human volunteers. A PLR maneuver was performed and cardiac output (CO) was measured by transthoracic echocardiography. ET-CO2 was measured with non-invasive capnographs. Volume responsiveness was defined as an increase in cardiac output (CO) > 12% at 90 s after PLR.

Results

Of the 50 volunteers, 32% were classified as volume responders. In this group, the left ventricle outflow tract velocity time integral (VTI_LVOT) increased from 17.9 ± 3.0 to 20.4 ± 3.4 (p = 0.0004), CO increased from 4.4 ± 1.5 to 5.5 ± 1.6 (p = 0.0), and ET-CO₂ rose from 32 ± 4.84 to 33 ± 5.07 (p = 0.135). Within the entire population, PLR-induced percentage ∆CO was not correlated with percentage ∆ET-CO₂ (R² = 0.13; p = 0.36). The area under the receiver operating curve for the ability of ET-CO₂ to discriminate responders from non-responders was of 0.67 ± 0.09 (95% CI 0.498–0.853). A ΔET-CO₂ ≥ 2 mmHg had a sensitivity of 50%, specificity of 97.06%, positive likelihood ratio of 17.00, negative likelihood ratio of 0.51, positive predictive value of 88.9%, and negative predictive value of 80.5% for the prediction of fluid responsiveness.

Conclusions

ΔET-CO₂ after a PLR has limited utility to discriminate responders from non-responders among healthy spontaneously breathing adults.

Electronic supplementary material

The online version of this article (10.1186/s40635-018-0187-0) contains supplementary material, which is available to authorized users.

Capnogram slope and ventilation dead space parameters: comparison of mainstream and sidestream techniques

BACKGROUND

Capnography may provide useful non-invasive bedside information concerning heterogeneity in lung ventilation, ventilation-perfusion mismatching and metabolic status. Although the capnogram may be recorded by mainstream and sidestream techniques, the capnogram indices furnished by these approaches have not previously been compared systematically.

METHODS

Simultaneous mainstream and sidestream time and volumetric capnography was performed in anaesthetized, mechanically ventilated patients undergoing elective heart surgery. Time capnography was used to assess the phase II (SII,T) and III slopes (SIII,T). The volumetric method was applied to estimate phase II (SII,V) and III slopes (SIII,V), together with the dead space values according to the Fowler (VDF), Bohr (VDB), and Enghoff (VDE) methods and the volume of CO2 eliminated per breath ([Formula: see text]). The partial pressure of end-tidal CO2 ([Formula: see text]) was registered.

RESULTS

Excellent correlation and good agreement were observed in SIII,T measured by the mainstream and sidestream techniques [ratio=1.05 (sem 0.16), R(2)=0.92, P<0.0001]. Although the sidestream technique significantly underestimated [Formula: see text] and overestimated SIII,V [1.32 (0.28), R(2)=0.93, P<0.0001], VDF, VDB, and VDE, the agreement between the mainstream and sidestream techniques in the difference between VDE and VDB, reflecting the intrapulmonary shunt, was excellent [0.97 (0.004), R(2)=0.92, P<0.0001]. The [Formula: see text] exhibited good correlation and mild differences between the mainstream and sidestream approaches [0.025 (0.005) kPa].

CONCLUSIONS

Sidestream capnography provides adequate quantitative bedside information about uneven alveolar emptying and ventilation-perfusion mismatching, because it allows reliable assessments of the phase III slope, [Formula: see text] and intrapulmonary shunt. Reliable measurement of volumetric parameters (phase II slope, dead spaces, and eliminated CO2 volumes) requires the application of a mainstream device.

A novel mainstream capnometer system for endoscopy delivering oxygen

Capnometry is a method to measure carbon dioxide (CO₂) in exhaled gas and it has been used in patients to monitor their respiratory status. Monitoring of exhaled CO₂ during endoscopic procedures has been shown to be effective in detecting drug-induced respiratory depression. Oxygen (O₂) supplementation is given to patients to abolish hypoxia during endoscopy. However, oxygen administration can interfere with CO2 measurement owing to oxygen flow. Therefore, we developed cap-ONE Biteblock for patients undergoing endoscopy with oxygen supply to measure CO₂ accurately. In this study we evaluated the basic performance of cap-ONE Biteblock. The cap-ONE Biteblock system could accurately measure CO₂ and efficiently supply O₂ comparing to conventional devices via a bench study.

Low partial pressure of end-tidal carbon dioxide predicts left ventricular assist device implantation in patients with advanced chronic heart failure

BACKGROUND

This study aimed to clarify the prognostic impact of partial pressure of end-tidal carbon dioxide (PETCO₂) in patients with advanced chronic heart failure (HF).

METHODS

Forty-eight patients (mean age 43.1±11.9years, 32 males) with chronic HF (44 with non-ischemic and 4 with ischemic cardiomyopathy) were prospectively enrolled. Echocardiography, blood tests, pulmonary function testing, and PETCO₂ measurements were performed as noninvasive tests, whereas right heart catheterization and arterial blood gas analysis were conducted as invasive tests. The primary end point of this study was left ventricular assist device (LVAD) implantation or cardiac death.

RESULTS

Eighteen patients underwent LVAD implantation at the Interagency Registry for Mechanically Circulatory Support (INTERMACS) profile 3 during the follow-up period, and no patient died. PETCO₂ was significantly lower in a stepwise manner with New York Heart Association functional class (class I or II, 34.2±9.3mmHg vs. class III or IV, 27.7±2.5mmHg; p<0.001). Univariate and multivariate Cox proportional hazard models and time-dependent receiver operating characteristic curve analysis revealed that PETCO₂≤31mmHg is an independent noninvasive predictor of LVAD implantation. Univariable and multivariable linear regression analyses showed that pulmonary arterial pressure was independently and highly correlated with PETCO₂ (r²=-0.512, p<0.001).

CONCLUSIONS

Among various noninvasive clinical parameters investigated, PETCO₂ was the independent predictor of LVAD implantation at the INTERMACS profile 3 in patients with chronic HF. Pulmonary congestion may significantly contribute to decreases in PETCO₂ in patients with HF.

Mainstream capnography system for nonintubated children in the postanesthesia care unit: Performance with changing flow rates, and a comparison to side stream capnography

INTRODUCTION

Monitoring of exhaled carbon dioxide (CO₂ ) in nonintubated patients is challenging. We compared the precision of a mainstream mask capnography to side stream sampling nasal cannula capnography. In addition, we compared the effect of gas flow rates on the measured exhaled CO₂ between mainstream mask and side stream nasal cannula capnography.

METHODS

A mainstream mask capnography system (cap-ONE) was tested. Children (weight of 7-40 kg, ASA 1-2) following anesthesia for minor procedures were assigned randomly to side stream or mainstream sampling groups. The side stream group wore a nasal cannula with CO₂ side port (NC). In the postanesthesia care unit, O₂ flow was started at 5 l·min^-1 , reduced to 2 and then 0.25 l·min^-1 every 3 min. Capnogram analysis measuring heights of all the waveforms was performed for continuous 120 s from the end of recording at each O₂ flow rate for each group.

RESULTS

Fifty-eight children were enrolled and 39 were analyzed (18 side stream NC and 21 mainstream mask). There were two mouth breathing children excluded from study in side stream NC group due to failure to capture measurable CO₂ waveforms. Peak CO₂ values measured by mainstream mask system were normally (Gaussian) distributed with smaller standard deviation (sd) at each O₂ flow than were those measured by side stream NC system which demonstrated irregular distributions with larger sd. Peak CO₂ values measurement was less affected by a change in flow rate in mainstream mask group than in side stream NC group (P = 0.04 in 5-0.25 l·min^-1 O₂ flow change).

CONCLUSION

A new mainstream mask system (cap-ONE) performed with greater precision than side stream NC monitoring regardless of mouth breathing. Measurement of peak CO₂ values by mainstream mask system showed normal distribution with smaller standard deviation (sd) and was less affected by O₂ flow change in predictable fashion.

A simple method for isocapnic hyperventilation evaluated in a lung model

BACKGROUND

Isocapnic hyperventilation (IHV) has the potential to increase the elimination rate of anaesthetic gases and has been shown to shorten time to wake-up and post-operative recovery time after inhalation anaesthesia. In this bench test, we describe a technique to achieve isocapnia during hyperventilation (HV) by adding carbon dioxide (CO2) directly to the breathing circuit of a standard anaesthesia apparatus with standard monitoring equipment.

METHODS

Into a mechanical lung model, carbon dioxide was added to simulate a CO2 production (V(CO2)) of 175, 200 and 225 ml/min. Dead space (V(D)) volume could be set at 44, 92 and 134 ml. From baseline ventilation (BLV), HV was achieved by doubling the minute ventilation and fresh gas flow for each level of V(CO2), and dead space. During HV, CO2 was delivered (D(CO2)) by a precision flow meter via a mixing box to the inspiratory limb of the anaesthesia circuit to achieve isocapnia.

RESULTS

During HV, the alveolar ventilation increased by 113 ± 6%. Tidal volume increased by 20 ± 0.1% during IHV irrespective of V(D) and V(CO2) level. D(CO2) varied between 147 ± 8 and 325 ± 13 ml/min. Low V(CO2) and large V(D) demanded a greater D(CO2) administration to achieve isocapnia. The FICO2 level during IHV varied between 2.3% and 3.3%.

CONCLUSION

It is possible to maintain isocapnia during HV by delivering carbon dioxide through a standard anaesthesia circuit equipped with modern monitoring capacities. From alveolar ventilation, CO2 production and dead space, the amount of carbon dioxide that is needed to achieve IHV can be estimated.

Evaluation of transcutaneous and end-tidal carbon dioxide levels during inhalation sedation in volunteers

Measurement of end-tidal carbon dioxide (PETCO2) is useful because of its noninvasiveness, continuity, and response time when sudden changes in ventilation occur during inhalation sedation. We compared the accuracy of PETCO2 using a nasal mask and nasal cannula with the accuracy of transcutaneous carbon dioxide (TC-CO2) and determined which method is more useful during inhalation sedation in volunteers. We used a modified nasal mask (MNM) and modified nasal cannula (MNC) for measurement of PETCO2. The capnometer measured PETCO2 in the gas expired from the nasal cavity by means of two devices. The volunteers received supplemental O2 by means of each device at a flow rate of 6 L/min. After the volunteers lay quietly for 5 min with a supply of 100 % O2, they received supplemental N2O by means of each device at concentrations of 10, 20, and 25 % for 5 min and 30 % for 25 min. The correlation coefficient was poorer in the MNM than in the MNC, and the mean difference between TC-CO2 and PETCO2 in the MNM was greater than that in the MNC. The difference between the TC-CO2 and PETCO2 ranged from 3 to 6 mmHg in the MNM and from 2 to 5 mmHg in the MNC. The difference between two variables against the TC-CO2 and the CO2 waveforms obtained by means of the two devices were within the clinically acceptable range. Our two devices can provide continuous monitoring of PETCO2 with a supply of N2O/O2 in patients undergoing inhalation sedation.

Use of signal decomposition to compensate for respiratory disturbance in mainstream capnometer

End-tidal carbon dioxide (P(ET)CO₂) monitoring has become an important tool in clinical monitoring, but there are still limitations in practice. Low-frequency modulation was used to reliably acquire respiratory information. Then the disturbances of humidity and flow rate were removed by signal decomposition. Finally, the real-time concentration of CO₂ was calculated and displayed by an adjusted calibration function. Targeted experiments confirm that a period of 180 ms and a depth of 50% was the optimal choice. In this case, the effects of humidity and flow rate reflected by different components were removed effectively from the capnography. This capnometer obtains capnography with excellent accuracy and stability in long-term continuous monitoring.

Accurate and stable continuous monitoring module by mainstream capnography

End-tidal partial pressure of [Formula: see text] is an important index in clinical monitoring. Medical mainstream capnography has become widely used, but there are still limitations in accuracy and stability. A type of mainstream capnometer based on the principle of non-dispersive infrared was designed. This capnometer inhibits signal drift by using electric modulation and thus ensures the accuracy of long-term CO2 monitoring. Statistical methods are used to find the best setting for sampling respiratory signals and improving precision. Several digital filtering techniques are used to process various interferences and improve capnogram quality. Clinical tests and targeted experiments show this mainstream capnometer can accurately monitor respiratory CO2 concentrations, especially at the end-tidal peak point. This capnometer also shows high accuracy and stability in long-term continuous monitoring.

A novel mainstream capnometer system for non-intubated pediatric patients requiring oxygen administration

Capnometer has been widely used as a respiratory monitor. Stable carbon dioxide (CO(2)) monitoring of non-intubated patient is especially problematic due to the frequent occurrence of tube obstruction and it could be even more difficult when oxygen is being administered. Oxygen is often administered by an oxygen mask or oxygen nasal cannula; however there are some problems with these methods. For oxygen masks, it is necessary to provide high-flow oxygen to prevent rebreathing of exhaled CO(2), and as for oxygen nasal cannula, it is incapable of increasing the oxygen concentration and patient may feel uncomfortable during oxygen administration because it could dry nasal mucous. To solve these problems, we developed a novel mainstream capnometer system, which provides stable monitoring of exhaled CO(2) while administering oxygen. This capnometer system has a mask with an opening large enough to facilitate the observation of patient's nose and mouth and the procedures such as daily oral care. Furthermore, the outer rim of the mask is designed to effectively retain oxygen flow without causing rebreathing.