Capnography for the nonintubated patient in the emergency setting

Can end-tidal CO2 measurement replace arterial partial CO2 in emergency department respiratory distress management?

OBJECTIVE

To assess the feasibility of using end-tidal carbon dioxide (EtCO2) as a non-invasive substitute for partial pressure of arterial carbon dioxide (PaCO2) in emergency department (ED) triage and follow-up, and to explore the potential of partial pressure of venous carbon dioxide (PvCO2) as an alternative to PaCO2.

DESIGN

Prospective cross-sectional study.

SETTING

Tertiary university hospital.

PATIENTS OR PARTICIPANTS

97 patients presenting with acute respiratory distress to the ED.

INTERVENTIONS

EtCO2, arterial blood gases, and venous blood gases measured at admission (0 min), 60 min, and 120 min.

MAIN VARIABLES OF INTEREST

CO2 levels.

RESULTS

Among 97 patients (mean age: 70.93 ± 9.6 years; 60.8% male), EtCO2 > 45 mmHg at admission showed strong positive correlations with PaCO2 and PvCO2 (r = 0.844, r = 0.803; p < 0.001, respectively). Significant positive correlation was observed between 60-min EtCO2 and PaCO2 (r = 0.729; p < 0.001). Strong correlation between PaCO2 and PvCO2 at 120 min when EtCO2 > 45 mmHg (r = 0.870; p < 0.001). EtCO2 was higher in hospitalized patients compared to discharged ones.

CONCLUSIONS

EtCO2 appears promising as a substitute for PaCO2 in ED patients with acute respiratory distress within the initial two hours of treatment. Venous blood gas sampling offers a less invasive alternative to arterial sampling, facilitating simultaneous blood tests.

Diagnostic utility of capnography in emergency department triage for screening acidemia: a pilot study

BACKGROUND

Capnography is a quantitative and reliable method of determining the ventilatory status of patients. We describe the test characteristics of capnography obtained during Emergency Department triage for screening acidemia.

RESULTS

We performed an observational, pilot study of adult patients presenting to Emergency Department (ED) triage. The primary outcome was acidemia, as determined by the basic metabolic panel and/or blood gas during the ED visit. Secondary outcomes include comparison of estimated and measured respiratory rates (RR), relationships between end-tidal CO2 (EtCO2) and venous partial pressure of CO2, admission disposition, in-hospital mortality during admission, and capnogram waveform analysis. A total of 100 adult ED encounters were included in the study and acidemia ([Formula: see text] or [Formula: see text]) was identified in 28 patients. The measured respiratory rate (20.3 ± 6.4 breaths/min) was significantly different from the estimated rate (18.4 ± 1.6 breaths/min), and its area under the receiver operating curve (c-statistic) to predict acidemia was only 0.60 (95% CI 0.51-0.75, p = 0.03). A low end-tidal CO2 (EtCO2 < 32 mmHg) had positive (LR+) and negative (LR-) likelihood ratios of 4.68 (95% CI 2.59-8.45) and 0.34 (95% CI 0.19-0.61) for acidemia, respectively-corresponding to sensitivity 71.4% (95% CI 51.3-86.8) and specificity 84.7% (95% CI 74.3-92.1). The c-statistic for EtCO2 was 0.849 (95% CI 0.76-0.94, p = 0.00). Waveform analysis further revealed characteristically abnormal capnograms that were associated with underlying pathophysiology.

CONCLUSIONS

Capnography is a quantitative method of screening acidemia in patients and can be implemented feasibly in Emergency Department triage as an adjunct to vital signs. While it was shown to have only modest ability to predict acidemia, triage capnography has wide generalizability to screen other life-threatening disease processes such as sepsis or can serve as an early indicator of clinical deterioration.

On Analyzing Capnogram as a Novel Method for Screening COVID-19: A Review on Assessment Methods for COVID-19

In November 2019, the novel coronavirus disease COVID-19 was reported in Wuhan city, China, and was reported in other countries around the globe. COVID-19 is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Strategies such as contact tracing and a vaccination program have been imposed to keep COVID-19 under control. Furthermore, a fast, noninvasive and reliable testing device is needed urgently to detect COVID-19, so that contact can be isolated and ringfenced before the virus spreads. Although the reverse transcription polymerase chain reaction (RT-PCR) test is considered the gold standard method for the diagnosis of SARS-CoV-2 infection, this test presents some limitations which cause delays in detecting the disease. The antigen rapid test (ART) test, on the other hand, is faster and cheaper than PCR, but is less sensitive, and may limit SARS-CoV-2 detection. While other tests are being developed, accurate, noninvasive and easy-to-use testing tools are in high demand for the rapid and extensive diagnosis of the disease. Therefore, this paper reviews current diagnostic methods for COVID-19. Following this, we propose the use of expired carbon dioxide (CO2) as an early screening tool for SARS-CoV-2 infection. This system has already been developed and has been tested on asthmatic patients. It has been proven that expired CO2, also known as capnogram, can help differentiate between respiratory conditions and, therefore, could be used to detect SARS-CoV-2 infection, as it causes respiratory tract-related diseases.

Can Non-Invasive Capnography and Integrated Pulmonary Index Contribute to Patient Monitoring in the Pediatric Emergency Department?

OBJECTIVES

Noninvasive capnography (NICG) devices can measure oxygen saturation, end-tidal carbon dioxide (EtCO2), respiratory rate, heart rate values and integrated pulmonary index (IPI). This study aimed to evaluate patients who were monitored using NICG for various indications in a pediatric emergency department and to determine its contribution to patient management in the pediatric emergency department (PED).

METHODS

In this study, children aged <18 years who had been monitored with a NICG at the PED in our university between August 2018-May 2019 were evaluated. Of them 48 patients' file records and monitored capnography parameters such as heart rate, respiratory rate, blood pressure, capillary refill time, Glasgow Coma Score, SpO2, EtCO2, IPI recorded in the forms were reviewed.

RESULTS

Patients most often presented to the emergency room due to seizures (35.4%), change in consciousness (22.9%), other neurological reasons (18.8%) with %50 were female. Seizure treatment(16.7%), circulatory-respiratory support(16.7%), and antiedema treatments(6.3%) were required for 39.5% patients as life-saving interventions, and 72.9% patients were hospitalized. Patients with low IPI(<8) values at the beginning and decreasing IPI (<8) measurements within monitoring period needed more life-saving treatments(p=0.005 and p=0.001, respectively). Low IPI values of the patients during monitoring showed a significant difference in the decision to be hospitalized(p=0.048).

CONCLUSIONS

The results of the present study indicate that monitoring with NICG in the pediatric emergency room can be an important early indicator in establishing clinical prediction. The study particularly points out that the IPI value can be a guide in decisions regarding life-saving treatment and hospitalization. Among the capnographic data of these patients who had a change in consciousness IPI values those measured at the beginning and within the monitorizarion period showed a significant correlation with low GCS (<8) (r=0.478, p=0.001 and r=0.456, p=0.02, respectively). Prospective comprehensive large scale studies are needed to examine the use of NICG and IPI in routine PED practice for various indications.

Can Providers Use Clinical Skills to Assess the Adequacy of Ventilation in Children During Bag-Valve Mask Ventilation?

OBJECTIVE

Bag-valve mask (BVM) ventilation requires both manual skill and clinical assessment of minute ventilation. Subjective factors can make supplying appropriate ventilation difficult. Capnography is not routinely used when ventilating nonintubated patients. Our objective was to determine if providers were able to maintain normal capnography values with BVM ventilation in pediatric patients based on clinical skills alone.

METHODS

Providers (nurses, residents, and fellows) delivered 2 minutes of BVM respiratory support to healthy children during induction of anesthesia for elective surgery. All patients had standard monitoring including capnography, but providers were blinded to capnography data. Capnography data were video recorded; values between 30 and 50 mmHg were considered indicative of normal ventilation. Any deviation from this range for greater than 10 consecutive seconds was considered an episode of inappropriate ventilation.

MAIN RESULTS

Twenty-five providers-patient pairs were enrolled. Nineteen providers were anesthesia residents. The median age of patients was 5.3 years (interquartile range, 3.3-8.5 years). Nineteen providers (76%) had at least 1 episode of abnormal ventilation with a median of 2 episodes per provider (interquartile range, 0.5-2.5). Among these providers, total mean duration of abnormal ventilation was 57 seconds (95% confidence interval, 41-72) or 47% (95% confidence interval, 34%-60%) of the 2-minute period.

CONCLUSIONS

Normal ventilation is difficult to maintain among providers delivering BVM ventilation to pediatric patients without objective feedback. Incorporation of capnography monitoring may improve BVM ventilation in children.

Tracking tidal volume noninvasively in volunteers using a tightly controlled temperature-based device: A proof of concept paper

INTRODUCTION

There is a paucity of noninvasive respiratory monitors for patients outside of critical care settings. The Linshom respiratory monitoring device is a novel temperature-based respiratory monitor that measures the respiratory rate as accurately as capnography.

OBJECTIVES

Determine whether the amplitude of the Linshom temperature profile was an accurate, surrogate and qualitative metric of the tidal volume (V_T ) that tracks V_T in healthy volunteers.

METHODS

Forty volunteers breathed room air spontaneously through a tight-fitting continuous positive airway pressure mask with a Linshom device mounted in the mask. V_T was measured contemporaneously using a standalone Maquet Servo-i ICU ventilator. The amplitudes of the Linshom temperature profiles were paired with the contemporaneous V_T measurements using least squares linear regression analysis and the coefficient of variation (R² ) was determined.

RESULTS

Forty volunteers completed the study. The data from 30 of the volunteers were analysed and are presented; data from 10 volunteers were not included due to protocol violations and/or technical issues unrelated to Linshom. The fluctuations in the amplitude of the Linshom temperature profiles mapped closely with the measured V_T using least squares linear regression analyses yielding a mean R² (95% CI) value of 0.87 (0.84-0.90).

CONCLUSION

These results support the notion that the Linshom temperature profile is an accurate and reliable surrogate that tracks changes in V_T in healthy volunteers. Further studies are warranted in patients in clinical settings to establish the effectiveness of this monitor.

Effects of diabetic ketoacidosis in the respiratory system

Diabetes affects approximately 30 million persons in the United States. Diabetes ketoacidosis is one of the most serious and acute complications of diabetes. At the time of presentation and during treatment of diabetic ketoacidosis (DKA), several metabolic and electrolyte derangements can ultimately result in respiratory compromise. Most commonly, hypokalemia, hypomagnesemia and hypophosphatemia can eventually lead to respiratory muscles failure. Furthermore, tachypnea, hyperpnea and more severely, Kussmaul breathing pattern can develop. Also, hydrostatic and non-hydrostatic pulmonary edema can occur secondary to volume shifts into the extracellular space and secondary to increased permeability of the pulmonary capillaries. The presence of respiratory failure in patients with DKA is associated with higher morbidity and mortality. Being familiar with the causes of respiratory compromise in DKA, and how to treat them, may represent better outcomes for patients with DKA.

Capnography in the Emergency Department: A Review of Uses, Waveforms, and Limitations

BACKGROUND

Capnography has many uses in the emergency department (ED) and critical care setting, most commonly cardiac arrest and procedural sedation.

OBJECTIVE OF THE REVIEW

This review evaluates several indications concerning capnography beyond cardiac arrest and procedural sedation in the ED, as well as limitations and specific waveforms.

DISCUSSION

Capnography includes the noninvasive measurement of CO₂, providing information on ventilation, perfusion, and metabolism in intubated and spontaneously breathing patients. Since the 1990s, capnography has been utilized extensively for cardiac arrest and procedural sedation. Qualitative capnography includes a colorimetric device, changing color on the amount of CO₂ present. Quantitative capnography provides a numeric value (end-tidal CO₂), and capnography most commonly includes a waveform as a function of time. Conditions in which capnography is informative include cardiac arrest, procedural sedation, mechanically ventilated patients, and patients with metabolic acidemia. Patients with seizure, trauma, and respiratory conditions, such as pulmonary embolism and obstructive airway disease, can benefit from capnography, but further study is needed. Limitations include use of capnography in conditions with mixed pathophysiology, patients with low tidal volumes, and equipment malfunction. Capnography should be used in conjunction with clinical assessment.

CONCLUSIONS

Capnography demonstrates benefit in cardiac arrest, procedural sedation, mechanically ventilated patients, and patients with metabolic acidemia. Further study is required in patients with seizure, trauma, and respiratory conditions. It should only be used in conjunction with other patient factors and clinical assessment.

Capnography as a tool to detect metabolic changes in patients cared for in the emergency setting

OBJECTIVE:

to evaluate the usefulness of capnography for the detection of metabolic changes in spontaneous breathing patients, in the emergency and intensive care settings.

METHODS:

in-depth and structured bibliographical search in the databases EBSCOhost, Virtual Health Library, PubMed, Cochrane Library, among others, identifying studies that assessed the relationship between capnography values and the variables involved in blood acid-base balance.

RESULTS:

19 studies were found, two were reviews and 17 were observational studies. In nine studies, capnography values were correlated with carbon dioxide (CO2), eight with bicarbonate (HCO3), three with lactate, and four with blood pH.

CONCLUSIONS:

most studies have found a good correlation between capnography values and blood biomarkers, suggesting the usefulness of this parameter to detect patients at risk of severe metabolic change, in a fast, economical and accurate way.

OBJETIVO:

avaliar a utilidade da capnografia para a detecção de alterações metabólicas em pacientes com respiração espontânea, no contexto das emergências e dos cuidados intensivos.

MÉTODO:

pesquisa bibliográfica estruturada aprofundada, nas bases de dados EBSCOhost, Biblioteca Virtual em Saúde, PubMed, Cochrane Library, entre outras, identificando estudos que avaliavam a relação entre os valores da capnografia e as variáveis envolvidas no equilíbrio ácido-base sanguíneo.

RESULTADOS:

foram levantados 19 estudos, dois eram revisões e 17 eram estudos observacionais. Em nove estudos, os valores capnográficos foram correlacionados com o dióxido de carbono (CO2), em oito com o bicarbonato (HCO3), em três com o lactato, e em quatro com o pH sanguíneo.

CONCLUSÕES:

na maioria dos estudos foi observada uma correlação adequada entre os valores capnográficos e os biomarcadores sanguíneos, sugerindo a utilidade deste parâmetro para a identificação de pacientes com risco de sofrer uma alteração metabólica grave, de uma forma rápida, econômica e precisa.

OBJETIVO:

explorar la utilidad de la capnografía para la detección de alteraciones metabólicas ante pacientes en respiración espontánea, en el ámbito de las emergencias y los cuidados críticos.

MÉTODO:

búsqueda bibliográfica estructurada en profundidad, en bases de datos EBSCOhost, Biblioteca Virtual de la Salud, PubMed, Cochrane Library, entre otras, identificando estudios que evaluaban la relación entre valores de la capnografía y variables implicadas en el equilibrio ácido-base sanguíneo.

RESULTADOS:

se recopilaron 19 estudios, dos eran revisiones y 17 observacionales. En nueve estudios, se correlacionaron los valores capnográficos junto al dióxido de carbono (CO2), en ocho con el bicarbonato (HCO3), tres con el lactato, y cuatro con el pH sanguíneo.

CONCLUSIONES:

la mayoría de estudios han obtenido una correlación adecuada entre los valores capnográficos y biomarcadores sanguíneos, sugiriendo la utilidad de este parámetro para la detección de pacientes en riesgo de padecer una alteración metabólica grave, de forma rápida, económica y precisa.

Capnography Prevents Hypoxia during Sedation for Dental Treatment: A Randomized Controlled Trial

Intravenous sedation is useful for dental treatment in patients with intellectual disabilities. However, it is often necessary to manage such patients with deep sedation because their cooperation cannot be obtained. During deep sedation, undetected hypoventilation can lead to severe complications, such as hypoxia. Recently, capnographic monitoring has been advocated as a useful technique for preventing hypoxia during sedation. This randomized control trial evaluated whether the use of capnography reduces the incidence of hypoxia during the deep sedation of patients for dental treatment. This study involved patients with intellectual disabilities who underwent dental treatment under sedation. The subjects were randomized to the intervention group (I-group) or control group (C-group). All of the patients underwent routine monitoring, as well as bispectral index (BIS) and capnographic monitoring; however, only an independent observer had access to the patients’ capnographic data during the dental procedures. Sedation was maintained at a BIS of 50 to 70 by administration of propofol. In the I-group, the independent observer signaled to the dental anesthesiologist if the capnogram indicated that the patient had been suffering from alveolar hypoventilation or apnea for >15 s. In the C-group, the observer signaled to the dental anesthesiologist if the capnogram indicated that the patient had been suffering from alveolar hypoventilation or apnea for >60 s. In both groups, the dental anesthesiologists responded to the signals using appropriate airway management strategies. The primary endpoint of this study was the incidence of hypoxia during dental treatment, which was defined as oxygen saturation of <95%. Hypoxemic episodes occurred in 13.4% and 34.8% of cases in the I-group and C-group, respectively. The incidence of hypoxia was significantly lower in the I-group. These results suggest that capnographic monitoring during deep sedation for dental treatment prevents hypoxemic episodes by allowing the early detection of hypoventilation.

Knowledge Transfer Statement: This is the first randomized controlled trial to examine whether the use of capnography reduces the incidence of hypoxia during deep sedation for dental treatment. The findings of this study can be used by clinicians to aid decision-making regarding dental sedation standards at individual clinics. Moreover, they can be used as high-level evidence during the production or updating of clinical guidelines for dental sedation by leading associations.

Linshom respiratory monitoring device: a novel temperature-based respiratory monitor

PURPOSE

We sought to develop a temperature-based respiratory instrument to measure respiration noninvasively outside critical care settings.

METHOD

Respiratory temperature profiles were recorded using a temperature-based noninvasive instrument comprised of three rapid responding medical-grade thermistors-two in close proximity to the mouth/nose (sensors) and one remote to the airway (reference). The effect of the gas flow rate on the amplitude of the tracings was determined. The temperature-based instrument, the Linshom Respiratory Monitoring Device (LRMD) was mounted to a face mask and positioned on a mannequin face. Respiratory rates of 5-40 breaths·min(-1) were then delivered to the mannequin face in random order using artificial bellows (IngMar Lung Model). Data from the sensors were collected and compared with the bellows rates using least squares linear regression and coefficient of determination. The investigators breathed at fixed rates of 0-60 breaths·min(-1) in synchrony with a metronome as their respiratory temperature profiles were recorded from sensors mounted to either a face mask or nasal prongs. The recordings were compared with a contemporaneously recorded sidestream capnogram from a CARESCAPE GEB450 Monitor. The extracted respiratory rates from the LRMD tracings and capnograms were compared using linear regression with a coefficient of determination and a Bland-Altman plot.

RESULTS

The amplitude of the sensor tracings was independent of the oxygen flow rate. Respiratory rates from the new temperature-based sensor were synchronous and correlated identically with both the artificial bellows (r(2) = 0.9997) and the capnometer mounted to both the face mask and nasal prongs (r(2) = 0.99; bias = -0.17; 95% confidence interval, -2.15 to 1.8).

CONCLUSIONS

Respiratory rates using the LRMD, a novel temperature-based respiratory instrument, were consistent with those using capnometry.

Comparison of the effects of ketamine and fentanyl-midazolam-medetomidine for sedation of rhesus macaques (Macaca mulatta)

Background

This study assessed the effects of sedation using a combination of fentanyl, midazolam and medetomidine in comparison to ketamine. Rhesus Macaques (Macaca mulatta), (n = 16, 5 males and 3 females randomly allocated to each treatment group) received either ketamine (KET) (10 mg.kg⁻¹) or fentanyl-midazolam-medetomidine (FMM) (10 μg/kg⁻¹; 0.5 mg.kg⁻¹; 20 μg.kg⁻¹) both IM. Oxygen (100 %) was provided by mask and heart rate, blood pressure, respiratory rate, EtCO₂ and depth of sedation were assessed every 5 min for 20 min. After the last time point, FMM monkeys were reversed with atipamezole-naloxone (0.2 mg.kg⁻¹; 10 μg.kg⁻¹). Recovery was scored using clinical scoring scheme. Differences in physiological parameters and quality of sedation were compared using Area Under the Curve (AUC) method and either Mann-Witney or t-student tests.

Results

Heart rate (beats/min) (Ket = 119 ± 18; FMM = 89 ± 17; p = 0.0066), systolic blood pressure (mmHg) (Ket = 109 ± 10; FMM = 97 ± 10; p = 0.0313), and respiratory rate (breaths/min) (Ket = 39 ± 9; FMM = 29 ± 10; p = 0.0416) were significantly lower in the FMM group. End-tidal CO₂ (mmHg) did not differ between the groups (KET = 33 ± 8; FMM = 42 ± 11; p = 0.0462)_. Although some depression of physiological parameters was seen with FMM, the variables all remained within the normal ranges in both groups. Onset of a sufficient degree of sedation for safe handling was more rapid with ketamine (KET = 2.9 ± 1.4 min; FMM = 7.9 ± 1.2 min; p = 0.0009), but FMM recovery was faster (KET = 21.4 ± 13.4 min; FMM = 9.1 ± 3.6 min; p = 0.0379) and of better quality (KET = 1.3 ± 0.9; FMM = 7.4 ± 1.9; p = 0.0009) most probably because of the effectiveness of the reversal agents used.

Conclusion

FMM provides an easily reversible immobilization with a rapid and good recovery quality and may prove a useful alternative to ketamine.