End-tidal Carbon Dioxide Measurements Research Articles

Investigation of the Relationship Between the Measured Alpha Angle in Capnography and Readmission Within Thirty Days in Chronic Obstructive Pulmonary Disease Patients Who Presented to the Emergency Department

BackgroundIndividuals with chronic obstructive pulmonary disease (COPD) constitute a significant portion of patients who present to the emergency department with dyspnea. However, there is no ideal method for predicting mortality or making hospitalization decisions in the emergency department (ED). In this regard, objective findings are needed for these patients. Since there are no objective findings regarding the hospitalization decision, there may be an increase in the re-admission rate of patients who needed hospitalization but were decided to be discharged. Side-stream end-tidal carbon dioxide (EtCO2) measurements offer a non-invasive, easy-to-interpret, quickly accessible, and reproducible method that can be applied at the bedside. ObjectivesThe aim of this study was to evaluate the relationship between the alpha angle values obtained by capnography and readmission rates within 30 days for patients experiencing COPD exacerbations who presented to the ED with dyspnea and were discharged after treatment. MethodsIn this study, we studied with 130 participants presented to the emergency department of a tertiary care university hospital with dyspnea, who are >18 y. Forty patients were excluded after evaluation for eligibility for the study. Thus, the data of 90 patients included were analyzed. We obtained alpha angle and EtCO2 values for all patients at the time of admission and also after treatment. The primary outcome measure of the study was the relationship between the patients’ readmission situations within 30 days of the alpha angle measurements. The secondary outcome measure was the association between patients’ EtCO2 values ​​and readmission within 30 days. ResultsIt was observed that both the pretreatment alpha angle values and the posttreatment alpha angle variables were statistically significant in predicting the readmission of the patients within 30 days (p = 0.001, p = 0.003) ConclusionThe results of this study show that alpha angle values measured for patients with COPD who present to the ED with the complaint of dyspnea may be used to predict readmission.

Using modified Fenn diagrams to assess ventilatory acclimatization during ascent to high altitude: Effect of acetazolamide.

High altitude (HA) ascent imposes systemic hypoxia and associated risk of acute mountain sickness. Acute hypoxia elicits a hypoxic ventilatory response (HVR), which is augmented with chronic HA exposure (i.e., ventilatory acclimatization; VA). However, laboratory-based HVR tests lack portability and feasibility in field studies. As an alternative, we aimed to characterize area under the curve (AUC) calculations on Fenn diagrams, modified by plotting portable measurements of end-tidal carbon dioxide ( ) against peripheral oxygen saturation ( ) to characterize and quantify VA during incremental ascent to HA (n=46). Secondarily, these participants were compared with a separate group following the identical ascent profile whilst self-administering a prophylactic oral dose of acetazolamide (Az; 125mg BID; n=20) during ascent. First, morning and measurements were collected on 46 acetazolamide-free (NAz) lowland participants during an incremental ascent over 10days to 5160m in the Nepal Himalaya. AUC was calculated from individually constructed Fenn diagrams, with a trichotomized split on ranked values characterizing the smallest, medium, and largest magnitudes of AUC, representing high (n=15), moderate (n=16), and low (n=15) degrees of acclimatization. After characterizing the range of response magnitudes, we further demonstrated that AUC magnitudes were significantly smaller in the Az group compared to the NAz group (P=0.0021), suggesting improved VA. These results suggest that calculating AUC on modified Fenn diagrams has utility in assessing VA in large groups of trekkers during incremental ascent to HA, due to the associated portability and congruency with known physiology, although this novel analytical method requires further validation in controlled experiments. HIGHLIGHTS: What is the central question of this study? What are the characteristics of a novel methodological approach to assess ventilatory acclimatization (VA) with incremental ascent to high altitude (HA)? What is the main finding and its importance? Area under the curve (AUC) magnitudes calculated from modified Fenn diagrams were significantly smaller in trekkers taking an oral prophylactic dose of acetazolamide compared to an acetazolamide-free group, suggesting improved VA. During incremental HA ascent, quantifying AUC using modified Fenn diagrams is feasible to assess VA in large groups of trekkers with ascent, although this novel analytical method requires further validation in controlled experiments.

Practical method in the diagnosis of diabetic ketoacidosis: end-tidal carbon dioxide

Objectives: Diabetic ketoacidosis (DKA) poses a life-threatening risk in uncontrolled diabetes. Current diagnostic criteria rely on invasive measures, leading to potential delays in treatment initiation. This study aimed to assess the diagnostic utility of noninvasive end-tidal carbon dioxide (EtCO2) measurements in DKA patients. Methods: A prospective, cross-sectional study was conducted in a tertiary-level Emergency Medicine Clinic from January 2021 to January 2023. Participants included adults with DKA symptoms and those with stable vital signs as controls. EtCO2 levels were measured using a capnograph device. Diagnostic criteria for DKA were blood glucose ≥250 mg/dL, ketonuria, ketonemia, and metabolic acidosis (pH<7.3 or bicarbonate <15 mEq/dL). Statistical analysis was performed using SPSS Statistics. Results: Of 730 participants, 120 had DKA, 410 did not, and 200 served as controls. EtCO2 levels significantly differed between DKA, non-DKA, and control groups (P<0.05). EtCO2 correlated with pH, lactate, base deficit, and bicarbonate (P<0.05). ROC analysis showed an AUC of 0.86 for EtCO2 in diagnosing DKA (P<0.01), with 91.67% sensitivity and 74.39% specificity at a cut-off value 23.7. Conclusion: This study suggests that EtCO2 measurement is a valuable noninvasive tool for diagnosing and assessing the severity of DKA in the emergency department. An EtCO2 threshold of <23.7 could prompt consideration of DKA in patients with elevated blood glucose levels. More extensive multicenter studies are warranted to validate these findings further. EtCO2 measurement could facilitate early DKA diagnosis and improve patient outcomes.

End-Tidal Carbon Dioxide Measurement in Out-of-Hospital Cardiac Arrest as a Predictor of Return of Spontaneous Circulation: A Literature Review.

One of the leading causes of morbidity and mortality worldwide is out-of-hospital cardiac arrest. Early defibrillation and high-quality cardiopulmonary resuscitation (CPR) have improved survival. The main goal of CPR is to achieve return of spontaneous circulation (ROSC), which is assessed by looking for a pulse, analyzing the heart rhythm, and assessing carbon dioxide levels. The use of cartography during CPR to confirm the correct position of the endotracheal tube during intubation or to assess the effectiveness of chest compressions has increased significantly in the last years. The aim of this review was to identify correlations between end-tidal carbon dioxide levels and the likelihood of ROSC in patients with out-of-hospital cardiac arrest. A literature search was performed in MEDLINE (via Pubmed), Scopus, Web of Science, and Google Scholar databases from September to November 2022. Keywords combined with the Boolean operators (AND/OR) were used in both free text and Medical Subject Headings. Studies on adult patients published between 01/01/2016 and 28/09/2022 were searched, with no geographical restrictions. At the end of the selection process, 14 studies were included that investigated capnography in out-of-hospital CPR and reported at least 1 outcome between end-tidal carbon dioxide and ROSC or survival. Capnography is an advantageous tool due to its noninvasive characteristics, ease of use, and immediacy of data. In out-of-hospital cardiac arrest, the use of the end-tidal carbon dioxide appears to be an appropriate complementary tool to support clinical decisions, such as correct positioning of the endotracheal tube, optimizing ventilation in CPR, and as a predictor of ROSC.

Acute cardiac tamponade during atrial flutter ablation: improved hemodynamics after positive pressure ventilation: a case report

IntroductionAcute cardiac tamponade is a rare event during any type of interventional or surgical procedure. It can occur during electrophysiology procedures due to radiofrequency ablation, lead or catheter manipulation, transseptal puncture, laser lead extractions, or left atrial appendage occlusion device positioning. Cardiac tamponade is difficult to study in a prospective manner, and case reports and case series are important contributions to understanding the best options for patient care.Case summaryAn 87-year-old Caucasian male patient breathing spontaneously developed acute tamponade during an atrial flutter ablation. Pericardial drain insertion was difficult, and hypotension failed to respond to epinephrine boluses. The patient became hypoxemic and hypercarbic, requiring intubation. Unexpectedly, the blood pressure markedly increased postintubation and remained in a normal range until the pericardium was drained.ConclusionSpontaneous ventilation is considered important to maintain venous return to the right heart during cardiac tamponade. However, spontaneous ventilation reduces venous return to the left heart and worsens the paradoxical pulse in tamponade. Intravenous vasopressors are thought to be ineffective during cardiac tamponade. Our patient maintained pulmonary blood flow as indicated by end-tidal carbon dioxide measurements but had no measurable systemic blood pressure during spontaneous ventilation. Our case demonstrates that tracheal intubation and positive pressure ventilation can transiently improve left heart venous return, systemic perfusion, and drug delivery to the systemic circulation.

Comparing the EMMA capnograph with sidestream capnography and arterial carbon dioxide pressure at 284 kPa.

Capnography aids assessment of the adequacy of mechanical patient ventilation. Physical and physiological changes in hyperbaric environments create ventilation challenges which make end-tidal carbon dioxide (ETCO2) measurement particularly important. However, obtaining accurate capnography in hyperbaric environments is widely considered difficult. This study investigated the EMMA capnograph for hyperbaric use. We compared the EMMA capnograph to sidestream capnography and the gold standard arterial carbon dioxide blood gas analysis in a hyperbaric chamber. In 12 resting subjects breathing air at 284 kPa, we recorded ETCO2 readings simultaneously derived from the EMMA and sidestream capnographs during two series of five breaths (total 24 measurements). An arterial blood gas sample was also taken simultaneously in five participants. Across all measurements there was a difference of about 0.1 kPa between the EMMA and sidestream capnographs indicating a very slight over-estimation of ETCO2 by the EMMA capnograph, but fundamentally good agreement between the two end-tidal measurement methods. Compared to arterial blood gas pressure the non-significant difference was about 0.3 and 0.4 kPa for the EMMA and sidestream capnographs respectively. In this study, the EMMA capnograph performed equally to the sidestream capnograph when compared directly, and both capnography measures gave clinically acceptable estimates of arterial PCO2.

Breath-hold BOLD fMRI without CO2 sampling enables estimation of venous cerebral blood volume: potential use in normalization of stimulus-evoked BOLD fMRI data

BOLD fMRI signal has been used in conjunction with vasodilatory stimulation as a marker of cerebrovascular reactivity (CVR): the relative change in cerebral blood flow (CBF) arising from a unit change in the vasodilatory stimulus. Using numerical simulations, we demonstrate that the variability in the relative BOLD signal change induced by vasodilation is strongly influenced by the variability in deoxyhemoglobin-containing cerebral blood volume (CBV), as this source of variability is likely to be more prominent than that of CVR. It may, therefore, be more appropriate to describe the relative BOLD signal change induced by an isometabolic vasodilation as a proxy of deoxygenated CBV (CBVdHb) rather than CVR. With this in mind, a new method was implemented to map a marker of CBVdHb, termed BOLD-CBV, based on the normalization of voxel-wise BOLD signal variation by an estimate of the intravascular venous BOLD signal from voxels filled with venous blood. The intravascular venous BOLD signal variation, recorded during repeated breath-holding, was extracted from the superior sagittal sinus in a cohort of 27 healthy volunteers and used as a regressor across the whole brain, yielding maps of BOLD-CBV. In the same cohort, we demonstrated the potential use of BOLD-CBV for the normalization of stimulus-evoked BOLD fMRI by comparing group-level BOLD fMRI responses to a visuomotor learning task with and without the inclusion of voxel-wise vascular covariates of BOLD-CBV and the BOLD signal change per mmHg variation in end-tidal carbon dioxide (BOLD-CVR). The empirical measure of BOLD-CBV accounted for more between-subject variability in the motor task-induced BOLD responses than BOLD-CVR estimated from end-tidal carbon dioxide recordings. The new method can potentially increase the power of group fMRI studies by including a measure of vascular characteristics and has the strong practical advantage of not requiring experimental measurement of end-tidal carbon dioxide, unlike traditional methods to estimate BOLD-CVR. It also more closely represents a specific physiological characteristic of brain vasculature than BOLD-CVR, namely blood volume.

Comparison of mainstream (Capnostat 5) and a low-flow sidestream capnometer (Capnostream) in mechanically-ventilated rabbits anesthetized with a Bain coaxial breathing system.

Introduction: Measurement of end-tidal carbon dioxide (PE'CO2) provides continuous non-invasive estimation of arterial carbon dioxide partial pressure (PaCO2). Agreement can be affected by the high respiratory rates and shallow tidal volumes of rabbits, especially when anesthetizing with a non-rebreathing system and high fresh gas flows. Capnometer function may be improved by increasing tidal volume and decreasing respiratory rate with mechanical lung ventilation.

Dead space fraction for treatment guidance and prognosis evaluation of acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a common cause of critical illness and high mortality from respiratory failure. Increased dead space fraction (VD/VT) was independently associated with lung injury and mortality of ARDS. VD/VT is readily obtained by bedside measurements of arterial blood gas and end-tidal carbon dioxide. Early attention and application of VD/VT as an indicator will help to better understand the pathophysiological of ARDS, guide clinical treatment, and better assess the severity and clinical prognosis of the disease.

Capnography in newborns under mechanical ventilation and its relationship with the measurement of CO2 in blood samples

IntroductionMonitoring the partial pressure of CO2 (PCO2) in newborns who require ventilation would allow avoiding hypocapnia and hypercapnia. The measurement of end-tidal carbon dioxide (ETCO2) is an alternative rarely implemented in this population. ObjectiveTo evaluate the relationship between ETCO2 and PCO2 in newborns. MethodsCross-sectional study comparing two PCO2 measurement methods, the conventional one by analysis of blood samples and the one estimated by ETCO2. The study included hospitalized newborns that required conventional mechanical ventilation. The ETCO2 was measured with a Tecme GraphNet® neo, a neonatal ventilator with an integrated capnograph, and we obtained the ETCO2–PCO2 gradient. We conducted correlation and Bland-Altman plot analyses to estimate the agreement. ResultsA total of 277 samples (ETCO2 / PCO2) from 83 newborns were analyzed. The mean values ​​of ETCO2 and PCO2 were 41.36mmHg and 42.04mmHg. There was a positive and significant correlation between ETCO2 and PCO2 in the overall analysis (r=0.5402; P<.001) and in the analysis of each unit (P<.001). The mean difference was 0.68 mmHg (95% CI, –0.68 to 1.95) and was not significant. We observed a positive systematic error (PCO2 > ETCO2) in 2 of the units, and a negative difference in the third (PCO2 < ETCO2). DiscussionThe correlation between ETCO and PCO2 was significant, although the obtained values ​​were not equivalent, with differences ranging from 0.1mmHg and 20mmHg. Likewise, we found systematic errors that differed in sign (positive or negative) between institutions.

Complete tracheal obstruction during anaesthesia for ventral slot decompression surgery in a dog

AbstractAn 8‐year‐old, female Yorkshire terrier presented to the neurology department with a 3‐month history of progressive ambulatory tetraparesis. A diagnosis of intervertebral disc protrusions at the levels of C3–C4 and C6–C7 was made using magnetic resonance imaging. Ventral slot decompressive surgery was carried out at both sites. When accessing the C6–C7 disc space, placement of Gelpi retractors resulted in complete tracheal obstruction, characterised by an absence of end tidal carbon dioxide measurement. This occurred in conjunction with the cessation of abdominal and thoracic respiratory movement despite the use of positive pressure ventilation. Removal of the Gelpi retractors resolved the tracheal occlusion and permitted the resumption of ventilatory support. To facilitate this surgical approach, the trachea was reintubated with a longer endotracheal tube to protect the patency of the airway. To the authors’ knowledge, this is the first report of tracheal obstruction as a complication of a ventral slot procedure.

End-tidal Carbon Dioxide Measurements in Unintentional Non-fire-related Carbon Monoxide Poisoning

Background: Poisoning with carbon monoxide occurs occasionally worldwide, and the gold diagnostic standard is to measure carboxyhemoglobin level in the blood. This study investigated the correlation between carboxyhemoglobin and the end-tidal carbon dioxide levels in 50 patients with carbon monoxide poisoning. Methods: We recruited 50 volunteer patients who had been admitted to the Emergency Services of Istanbul Medipol University Hospital between January 2017 and January 2018. They had been diagnosed with carbon monoxide poisoning unrelated to fire accidents. The arterial and venous blood gases, and other blood and clinical parameters were also measured. The patients’ end-tidal carbon dioxide levels were measured from the nose and mouth air, using a Capnostream 20p bedside monitor. Pearson’s correlation analyses were performed and the results were compared with the end-tidal carbon dioxide, carboxyhemoglobin and oxygen saturation in the arterial and venous blood samples. Results: The Mean±SD age was 33.98±10.89 years. The Mean±SD arterial and venous carboxyhemoglobin values were 18.05±7.10 and 12.11±9.67, respectively. There were no statistically significant differences between the oxygen saturation, and the arterial and venous blood levels of carboxyhemoglobin (P=0.870, P=0.950), respectively. Also, no statistically significant correlations were found between the end-tidal carbon dioxide, and the arterial and venous carboxyhemoglobin levels (P=0.529, P=0.601), respectively. Conclusion: The results from the blood analyses demonstrated that there was no statistically significant difference between the end-tidal carbon dioxide and the carboxyhemoglobin levels in these patients who had been earlier diagnosed with carbon monoxide poisoning, unrelated to fire accidents.

Capnografía en recién nacidos en ventilación mecánica y su relación con la medición de CO2 en muestras sanguíneas

IntroductionMonitoring the partial pressure of CO2 (PCO2) in newborns who require ventilation would allow avoiding hypocapnia and hypercapnia. The measurement of end-tidal carbon dioxide (ETCO2) is an alternative rarely implemented in this population. ObjectiveTo evaluate the relationship between ETCO2 and PCO2 in newborns. MethodsCross-sectional study comparing two PCO2 measurement methods, the conventional one by analysis of blood samples and the one estimated by ETCO2. The study included hospitalized newborns that required conventional mechanical ventilation. The ETCO2 was measured with a Tecme GraphNet® neo, a neonatal ventilator with an integrated capnography, and we obtained the ETCO2-PCO2 gradient. We conducted correlation and Bland-Altman plot analyses to estimate the agreement. ResultsA total of 277 samples (ETCO2/PCO2) from 83 newborns were analyzed. The mean values of ETCO2 and PCO2 were 41.36 mmHg and 42.04 mmHg. There was a positive and significant correlation between ETCO2 and PCO2 in the overall analysis (r = 0.5402; p < .001) and in the analysis of each unit (p < .001). The mean difference was 0.68 mmHg (95% CI, −0.68 to 1.95) and was not significant. We observed a positive systematic error (PCO2 > ETCO2) in 2 of the units, and a negative difference in the third (PCO2 < ETCO2). DiscussionThe correlation between ETCO and PCO2 was significant, although the obtained values were not equivalent, with differences ranging from 0.1 mmHg to 20 mmHg. Likewise, we found systematic errors that differed in sign (positive or negative) between institutions.

Evaluation of the Relationship between Transcutaneous Carbondioxide Monitorization and End-tidal Carbondioxide and Partial Carbondioxide Monitorization

MonitorizationNon-invasive methods have replaced invasive methods in line with developments in pediatric intensive care units. (Especially methods that enable continuous monitoring) Although arterial carbon dioxide measurement is still the gold standard for the evaluation of alveolar ventilation, the need for continuous monitoring of PaCO2 and the invasive nature of this method have led to the investigation of alternative methods. To evaluate the correlation of transcutaneous CO2 (TcCO2) monitoring with PaCO2 and ETCO2 in mechanically ventilated patients in peditaric intensive care units. Single-center, prospective, observational cohort study. We enrolled 60 patients between the age of 1 month-18 years who were mechanically ventilated in pediatric intensive care unit for this single-center, prospective, observational cohort study from February 2019 through March 2019. Correlation analysis was performed for arterial PaCO2, end-tidal CO2, TcCO2 parameters. P&lt;0.05 values were considered significant. The Bland-Altman plot was created for determining the agreement between the methods. The correlation of transcutaneous CO2 and end-tidal CO2 with arterial PaCO2 was evaluated, both parameters were found to be positively and highly correlated (r=0.864, p&lt;0.001, r:0.962, p&lt;0.001, respectively). The mean bias between the arterial carbondioxide mesaurement and transcutaneous measurement was 5.5, and limits of agreement (bias ±1.96 SD) ranged from -13.9 to 2.9. The mean bias between the arterial carbondioxide mesaurement and end-tidal carbondioxide measurement was 2.3, and limits of agreement (bias ±1.96 SD) ranged from -4.1 to 8.6. In 44 measurements (88%), the TcCO2 was ±7.5 mm Hg of the PaCO2. TcCO2 seems to be a good alternative for carbon dioxide measurement, as it is non-invasive and allows continuous monitoring in view of today's intensive care conditions, but arterial PaCO2 measurement is still the gold standard method. Continuous TcCO2 monitoring provides a promising alternative to repeated blood sampling in subjects requiring mechanical ventilation for critically ill children.

End-tidal carbon dioxide measurements as a surrogate to arterial carbon dioxide during pediatric laparoscopic surgeries: a prospective observational cohort study

BackgroundMaintaining normocapnia during mechanical ventilation in anesthetized children during laparoscopic surgeries is highly recommended. There is a debate regarding the use of capnography (ETCO2) as a trend monitor for evaluation of arterial carbon dioxide levels (PaCO2). We analyzed the relationship between ETCO2 and PaCO2 with time in elective pediatric laparoscopic surgeries. MethodsThis study was a prospective observational cohort analysis of 116 paired comparisons between PaCO2 and ETCO2 computed from 29 children (ASA I, 12...72 months). Arterial blood samples were withdrawn before, at 15...minutes and 30...minutes during pneumoperitoneum and 1...minute after deflation. ETCO2 value was recorded simultaneously, while arterial blood was withdrawn. PaCO2...ETCO2 relationship was evaluated by Pearson's correlation coefficients and Bland Altman Method of agreement. ResultsOut of the 116 comparisons analyzed, a PaCO2...ETCO2 difference beyond 0 to ..± 5...mmHg was recorded in 71 comparisons (61.2%) with negative difference in 34 comparisons (29.3%). A positive significant correlation between PaCO2 and ETCO2 was recorded before (r...=...0.617, p...=...0.000) and at 15...minutes (r...=...0.582, p...=...0.001), with no significant correlation at 30 minutes (r...=...0.142, p...=...0.461), either after deflation (r...=...0.108, p...=...0.577). Bland-Altman plots showed agreement between ETCO2 and PaCO2 before inflation with mean PaCO2-ETCO2 difference 0.14........5.6...mmHg (limits of 95% agreement -10.84...11.2, simple linear regression testing p-value 0.971), with no agreement at 15...minutes (0.51........7.15, -13.5...14.5, p...=...0.000), 30...minutes. (2.62........7.83, -12.73...17.97, p...=...0.000), or after deflation (1.81........6.56, -10.93...14.55, p...=...0.015). ConclusionUsage of capnography as a trend monitor in pediatric laparoscopic surgeries may not be a reliable surrogate for PaCO2 levels. Trial registrationClinical Trials. gov (Identifier: NCT03361657)

Prehospital End-Tidal CO2: A Superior Marker for Mortality Risk in the Acutely Injured Patient.

Emergency medical personnel must expeditiously triage acutely injured patients to the appropriate medical facility. Efficient and objective variables to facilitate this process and provide information to the receiving trauma center are needed. Currently, multiple variables are used to prognosticate injury severity and risk of mortality including vital signs, mental status, lactate, and base excess. We investigated the prehospital use of end-tidal carbon dioxide (ETCO2) as a noninvasive physiologic measure that can be obtained in the acutely injured patient. We performed a retrospective analysis of 557 acutely injured patients over 2years at a Level 1 trauma center. All patients arriving as trauma activations with ETCO2 measurements were included in analysis. End-tidal carbon dioxide measurements were categorized as low, normal, and high based on reference levels. Mortality was the primary outcome. Secondary receiver operator curves (ROC) for base excess, venous lactate, blood pressure, and venous pH were compared. We hypothesized ETCO2 levels would be able to predict mortality. End-tidal carbon dioxide levels conferred a mortality rate of 38%, 17.3%, and 2.9% for low, normal, and high, respectively (P < .001). Receiver operator curve analysis produced an area under the curve predictive value for ETCO2 (.748) which was superior to lactate (.660), SBP (.578), pH (.560), and base excess (.497). End-tidal carbon dioxide is a more sensitive and specific predictor of mortality in the acutely injured patient compared to venous lactate, base deficit, blood pressure, or venous pH. Additional studies are needed to determine if ETCO2 can be used as an effective prehospital adjunct to prevent mortality in acutely injured patients.

Development and validation of a novel fibre-optic respiratory rate sensor (FiRRS) integrated in oxygen delivery devices

Respiratory rate (RR) monitoring provides crucial information on the overall health condition of patients and a reliable, low cost RR monitor for normal hospital inpatient or home use would be of significant benefit. The proposed system measures light reflection from a Fibre Bragg Grating (FBG) located near, and the total reflection spectrum from a humidity sensing film deposited at, the tip of an optical fibre. Every breath causes a shift in the wavelength reflected from the FBG and intensity change in the overall reflection spectrum. The accuracy of different techniques is investigated in a two-part study with 15 healthy volunteers. In part 1, the participants’ respiration rate followed a handheld mobile application at 5, 12 and 30 breaths per minute with simultaneous measurement using the optical fibre system, thoracic impedance pneumography (TIP) and capnometry device (where possible). Two types of medical face masks and a nasal cannula with oxygen delivery rates were investigated. In part 2, participants wore an anaesthetic face mask and breathed at normal and low tidal volumes to evaluate whether low tidal volumes could be detected. The most accurate measurement of RR was through monitoring the Bragg wavelength shift (mean accuracy = 88.1%), followed by the intensity change at the Bragg wavelength (mean accuracy = 78.9%), capnometry (mean accuracy = 77.8%), area under the overall spectrum (mean accuracy = 65.4%) and TIP (mean accuracy = 43.1%). The Fibre-optic Respiratory Rate Sensor system (FiRRS) can differentiate between normal and low tidal volumes (p-value < 0.05) and demonstrated higher accuracy than capnometry measurement of end-tidal carbon dioxide in exhaled air. These latter two monitors measured RR more accurately than TIP. A comparable accuracy in the measurement of RR was obtained when the FiRRS was implemented in nasal cannula and face masks.

Role of capnography in detecting hypercapnic events during weaning from mechanical ventilation

Background End-tidal carbon dioxide (ETCO2) measurement is more applied in clinical practice, as it is a noninvasive tool that helps to evaluate the ventilatory status of the patient. The aim of the present study was to investigate the relationship between ETCO2 and arterial partial pressure of CO2 (PaCO2) measurements and to estimate the role of capnography during weaning off mechanical ventilation. Patients and methods A prospective cross-sectional study was conducted on 60 adult critically ill patients with respiratory failure, comprising 47 males and 13 females. They were put on mechanical ventilation, and after fulfilling criteria of weaning, they were kept on continuous positive airway pressure (CPAP) mode for 1 h. ETCO2, PaCO2, and gradient were measured before and after weaning. Results Mean difference between PaCO2 and ETCO2 before weaning was 8.3 and after one hour on CPAP was 5.1. There was a highly statistically significant positive correlation between ETCO2 and PaCO2 before weaning and after 1 h on CPAP. Bland-Altman comparison between ETCO2 and PaCO2 before weaning and after 1 h on CPAP revealed limits of agreement were 1.941 to 14.826 and −4.134 to 14.367, respectively. Conclusion ETCO2 measurement gives a proper estimation of PaCO2 in patients on mechanical ventilation. ETCO2 decreases the need for repeated invasive arterial blood gas samples.

Uses and pitfalls of measurement of end-tidal carbon dioxide during cardiac arrest.

To discuss recent studies relevant to the utility of measuring end-tidal carbon dioxide (ETCO2) during cardiopulmonary resuscitation (CPR) and its correlation with outcome in adults experiencing cardiac arrest. Over the past couple of years, at least five studies have included measurement of ETCO2 in their methods. Two of these studies were prospective and two retrospective. All considered ETCO2 measurements after out-of-hospital cardiac arrest, either in the prehospital setting, or after arrival in the emergency department. All assessed for an association between ETCO2 measurement and return of spontaneous circulation (ROSC). However, the timing of measurement, whether a one-off value or a trend and the cut-off values used to determine whether or not there was an association were different in all cases. Higher values of ETCO2 during resuscitation from cardiac arrest are generally associated with a greater likelihood of ROSC. However, timing of measurements and cut-off values used show significant variability across different studies, making it hard to draw any conclusions about the utility of any particular reading for prognostication. Future studies might aim to develop an accepted standard for the timing and cut-off value of ETCO2 used, to enable comparison of the parameter across different studies.

Prehospital end-tidal CO2 as an early marker for transfusion requirement in trauma patients.

Below normal end-tidal carbon dioxide measurement (ETCO2) is associated with worse outcomes in sepsis and trauma patients as compared to patients with normal ETCO2. We sought to determine if ETCO2 can be used in the prehospital setting to predict transfusion requirement, operative hemorrhage control, or mortality in the first 24h after admission for trauma. This is a retrospective cohort study at a suburban, academic Level 1 Trauma Center. Patients were sequentially identified as prehospital trauma alerts from a single EMS system which requires, per policy, ETCO2 for all traumas. One year of prehospital data was collected and paired with hospital trauma registry data. Comparisons were made between ETCO2 values for patients who required transfusion, operative blood loss control, or who died, and those who did not. Two hundred thirty-five trauma patients were transported via the study EMS system, of which 105 (44.7%) had documented ETCO2 values. Patient mean age was 60 (SD24) years with 59 (56.2%) male. Three patients were intubated prehospital and seven were intubated in the trauma bay. Mean prehospital ETCO2 for those who needed transfusion, surgery, or died (n=11) was 25.7 (9.1) compared to 30.6 (7.8) for those who did not (p=0.049). Optimal cutoff for our population was EtCO2≤27 with a sensitivity of 72.7% (95% CI 32-93) and specificity of 72.2% (62-81). Below normal ETCO2 values were associated with increase need for transfusion, operative intervention, and death. Further study is warranted to determine if ETCO2 outperforms other predictors of severe trauma.