Integrated Pulmonary Index during nurse-administered procedural sedation: Study protocol for a cluster-randomized trial

AIM

To determine if smart alarm-guided treatment of respiratory depression using the Integrated Pulmonary Index is an effective way to implement capnography during nurse-administered sedation.

DESIGN

Parallel cluster-randomized trial.

METHODS

Nurses will be randomized to use capnography with or without the Integrated Pulmonary Index enabled. Capnography alarm performance will be compared between nurses using capnography alone or with the Integrated Pulmonary Index enabled. The target sample size is 400 adult patients scheduled for elective procedures with nurse-administered sedation. The primary outcome is the number of seconds in an alert condition state without an intervention being applied. Secondary outcomes are alarm burden, number of appropriate alarms, number of inappropriate alarms, total duration of alert conditions, choice of alarm settings and adverse sedation events. This study has been funded since April 2021.

DISCUSSION

Implementing capnography into practice for respiratory monitoring during nurse-administered sedation is considered a high priority. The Integrated Pulmonary Index shows promise as a strategy to optimize the implementation of capnography for respiratory monitoring during nurse-administered sedation. If it is found in this study that using the Integrated Pulmonary Index improves the nursing management of physiologically abnormal states during nurse-administered sedation, it would provide the high-level evidence needed to support broader use of this 'smart alarm' strategy for respiratory monitoring in practice.

IMPACT

With advances in medical technology continuing to expand the indications for minimally invasive surgical techniques, the use of nurse-administered sedation during medical procedures is likely to expand in the future. The findings may be applied to other populations receiving nurse-administered sedation during medical procedures. Results from this study will help translate the usage of smart alarm-guided treatment of respiratory depression during procedural sedation.

TRIAL REGISTRATION

NCT05068700.

Respiratory rate monitoring in healthy volunteers by central photoplethysmography compared to capnography

Monitoring of respiration is a central task in clinical medicine, crucial to patient safety. Despite the uncontroversial role of altered respiratory frequency as an important sign of impending or manifest deterioration, reliable measurement methods are mostly lacking outside of intensive care units and operating theaters. Photoplethysmography targeting the central blood circulation in the sternum could offer accurate and inexpensive monitoring of respiration. Changes in blood flow related to the different parts of the respiratory cycle are used to identify the respiratory pattern. The aim of this observational study was to compare photoplethysmography at the sternum to standard capnography in healthy volunteers. Bland Altman analysis showed good agreement (bias -0.21, SD 1.6, 95% limits of agreement -3.4 to 2.9) in respiratory rate values. Photoplethysmography provided high-quality measurements of respiratory rate comparable to capnographic measurements. This suggests that photoplethysmography may become a precise, cost-effective alternative for respiratory monitoring.

Accuracy of Delta Capnography for the Prediction of Pulmonary Vein Occlusion During Cryoablation for Atrial Fibrillation

The purpose of this study was to quantify the relationship between a drop in end-tidal carbon dioxide (etCO₂) and occlusion of pulmonary veins (PVs) to find a delta etCO₂ (ΔetCO₂) able to predict occlusion during PV isolation (PVI) by cryoballoon. We designed a prospective registry. Paroxysmal atrial fibrillation patients who underwent cryoballoon PVI were included. Capnography was performed. Occlusion was tested by injection. A comparison between ΔetCO₂ and occlusion was performed. Eighteen subjects (138 injections) were included. A drop of >3.5 mmHg predicted occlusion of the PV (sensitivity, 80%; specificity, 86.7%). A ΔetCO₂ of ≥3.5 mmHg during inflation of the cryoballoon in each PV directly correlates with PV balloon occlusion.

Investigating the Effects of Protective Face Masks on the Respiratory Parameters of Children in the Postanesthesia Care Unit During the COVID-19 Pandemic

PURPOSE

The purpose of this study was to investigate the effect of protective face mask usage during the postoperative period on carbon dioxide retention in children during the COVID-19 pandemic.

DESIGN

This study was designed as a prospective, randomized trial including 40 ASA I-II patients aged 3 to 10 years who were scheduled for elective surgery.

METHODS

Patients were randomly allocated to two groups. The first group (group 1) received O₂ treatment over the protective face mask. In the second group (group 2), the protective face mask was worn over the O₂ delivery system. Heart rate, oxygen saturation (SPO₂) level, end-tidal carbon dioxide (EtCO₂) level, and respiratory rate were measured using a patient monitor at 0, 5, 10, 15, 30, and 45 minutes and recorded. The primary outcome of the study was the determination of the EtCO₂ levels, which were used to assess the safety of the mask in terms of potential carbon dioxide retention.

FINDINGS

None of the participants' SPO₂ levels fell below 92% while wearing masks. There was no statistically significant difference between the groups in terms of EtCO₂, heart rate, SPO₂, and respiratory rate (P > .05).

CONCLUSIONS

During the COVID-19 pandemic, protective surgical face masks can be used safely in the postoperative period for pediatric patients aged 3 to 10 years.

Volumetric Capnography at 36 Weeks Postmenstrual Age and Bronchopulmonary Dysplasia in Very Preterm Infants

OBJECTIVES

To assess the feasibility of volumetric capnography in spontaneously breathing very preterm infants at 36 weeks postmenstrual age (PMA) and its association with clinical markers of lung disease including the duration of respiratory support and bronchopulmonary dysplasia (BPD).

STUDY DESIGN

We obtained mainstream volumetric capnography measurements in 143 very preterm infants at 36 weeks PMA. BPD was categorized into no, mild, moderate, and severe according to the 2001 National Heart, Lung and Blood Institute workshop report. Normalized capnographic slopes of phase II (S_nII) and phase III (S_nIII) were calculated. We assessed the effect of BPD, duration of respiratory support, and duration of supplemental oxygen on capnographic slopes.

RESULTS

S_nIII was steeper in infants with moderate to severe BPD (76 ± 25/L) compared with mild (31 ± 20/L) or no BPD (26 ± 18/L) (P < .001). The association of S_nIII with moderate to severe BPD persisted after adjusting for birth weight z-score, respiratory rate, and airway dead space to tidal volume ratio. The diagnostic usefulness of S_nIII to discriminate between infants with and without moderate to severe BPD was high (area under the curve, 0.94; 95% CI, 0.89-0.99).

CONCLUSIONS

Volumetric capnography is feasible in spontaneously breathing preterm infants at 36 weeks PMA and reflects the degree of lung disease. This promising bedside lung function technique may offer an objective, continuous physiological outcome measure for assessment of BPD severity.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT02083562.

The PaCO2-ETCO2 gradient in pre-hospital intubations of all aetiologies from a single UK helicopter emergency medicine service 2015-2018

Background

Control of the arterial partial pressure of carbon dioxide (PaCO2) is important in the ventilated patient. End-tidal carbon dioxide (ETCO2) levels are often used as a proxy, but are clinically limited. The difference between the PaCO2 and ETCO2 has been suggested to be 0.5-1.0 kPa. However, this has not been consistently reflected in the physiologically unstable pre-hospital patient. This study aims to elucidate the PaCO2-ETCO2 gradient for pre-hospital intubated patients.

Methods

This was a retrospective, cohort study using data identified from the HEMSbase 2 database (Feb 2015-Nov 2018). Patients were included if they had documented ETCO2 and arterial PaCO2 measurements. Arterial PaCO2 data that could not be linked to within 5 minutes of ETCO2 were excluded. Bland-Altman plots were calculated to describe agreement.

Results

A total of 73 patients were identified. Aetiology was arranged into three categories: 13 (17.8%) medical, 22 (30.1%) traumatic and 38 (52.1%) out-of-hospital cardiac arrest (OHCA). The median PaCO2-ETCO2 gradient was 2.0 [1.3-3.1] kPa. A PaCO2-ETCO2 gradient of 0-1 kPa was seen for only 11 (15.1%) of total patients. The Bland-Altman agreement for all aetiologies was more than the accepted gradient of 0-1 kPa with the largest bias and widest limits of agreement seen for OHCA (-3.2 [0.3 - -6.8]).

Conclusion

The magnitude of the differences between the ETCO2 and PaCO2, levels of variation and inability to predict this suggest that ETCO2 is not a suitable surrogate upon which to base ventilatory settings in conditions where pH or PaCO2 require precise control.

Quality Management of Prehospital Airway Programs: An NAEMSP Position Statement and Resource Document

Prehospital airway management encompasses a multitude of complex decision-making processes, techniques, and interventions. Quality management (encompassing quality assurance and quality improvement activities) in EMS is dynamic, evidence-based, and most of all, patient-centric. Long a mainstay of the EMS clinician skillset, airway management deserves specific focus and attention and dedicated quality management processes to ensure the delivery of high-quality clinical care.It is the position of NAEMSP that:All EMS agencies should dedicate sufficient resources to patient-centric, comprehensive prehospital airway quality management program. These quality management programs should consist of prospective, concurrent, and retrospective activities. Quality management programs should be developed and operated with the close involvement of the medical director.Quality improvement and quality assurance efforts should operate in an educational, non-disciplinary, non-punitive, evidence-based medicine culture focused on patient safety. The highest quality of care is only achieved when the quality management program rewards those who identify and seek to prevent errors before they occur.Information evaluated in prehospital airway quality management programs should include both subjective and objective data elements with uniform reporting and operational definitions.EMS systems should regularly measure and report process, outcome, and balancing airway management measures.Quality management activities require large-scale bidirectional information sharing between EMS agencies and receiving facilities. Hospital outcome information should be shared with agencies and the involved EMS clinicians.Findings from quality management programs should be used to guide and develop initial education and continued training.Quality improvement programs must continually undergo evaluation and assessment to identify strengths and shortcomings with a focus on continuous improvement.

Prehospital Drug Assisted Airway Management: An NAEMSP Position Statement and Resource Document

Airway management is a critical intervention for patients with airway compromise, respiratory failure, and cardiac arrest. Many EMS agencies use drug-assisted airway management (DAAM) - the administration of sedatives alone or in combination with neuromuscular blockers - to facilitate advanced airway placement in patients with airway compromise or impending respiratory failure who also have altered mental status, agitation, or intact protective airway reflexes. While DAAM provides several benefits including improving laryngoscopy and making insertion of endotracheal tubes and supraglottic airways easier, DAAM also carries important risks. NAEMSP recommends:DAAM is an appropriate tool for EMS clinicians in systems with clear guidelines, sufficient training, and close EMS physician oversight. DAAM should not be used in settings without adequate resources.EMS physicians should develop clinical guidelines informed by evidence and oversee the training and credentialing for safe and effective DAAM.DAAM programs should include best practices of airway management including patient selection, assessmenct and positioning, preoxygenation strategies including apneic oxygenation, monitoring and management of physiologic abnormalities, selection of medications, post-intubation analgesia and sedation, equipment selection, airway confirmation and monitoring, and rescue airway techniques.Post-DAAM airway placement must be confirmed and continually monitored with waveform capnography.EMS clinicians must have the necessary equipment and training to manage patients with failed DAAM, including bag mask ventilation, supraglottic airway devices and surgical airway approaches.Continuous quality improvement for DAAM must include assessment of individual and aggregate performance metrics. Where available for review, continuous physiologic recordings (vital signs, pulse oximetry, and capnography), audio and video recordings, and assessment of patient outcomes should be part of DAAM continuous quality improvement.

Respiratory consequences of obesity and diabetes

Összefoglaló. Bevezetés: A cukorbetegségben nő a simaizmok tónusa, és megváltozik az elasztin és a kollagén szerkezete. Mivel a tüdőszövetben ezek a strukturális elemek meghatározóak, a cukorbetegség várhatóan módosítja a légutak és a tüdőszövet mechanikai és funkcionális viselkedését. Célkitűzés: Vizsgálatunk során diabetesben szenvedő, elhízott és nem elhízott betegeink körében tanulmányoztuk a légzésmechanikai elváltozásokat és a gázcserefunkciót. Módszer: Elektív szívsebészeti beavatkozásra kerülő, normál testalkatú betegeket diabetesben nem szenvedő (n = 80), illetve cukorbeteg (n = 35) csoportokra osztottuk. További két betegcsoportba elhízott és nem cukorbeteg (n = 47), valamint elhízott és diabetesben szenvedő (n = 33) betegek kerültek. A légzőrendszer mechanikai tulajdonságait kényszerített oszcillációs technikával határoztuk meg, mellyel a légúti ellenállás (Raw), valamint a szöveti csillapítás (G) és rugalmasság (H) tényezői jellemezhetők. Volumetriás kapnográfia segítségével a kapnogram 3. fázisának meredekségét és a légzési térfogat különböző ventilációs/perfúziós illeszkedési zavaraiból adódó holttérfrakciókat határoztuk meg. Az intrapulmonalis shuntfrakciót és az oxigenizációs indexet (PaO2/FiO2) artériás és centrális vénás vérgázmintákból határoztuk meg. Eredmények: A megfelelő kontrollcsoportokhoz hasonlítva a cukorbetegség önmagában is növelte az Raw (7,4 ± 5 vs. 3,0 ± 1,7 H2Ocm.s/l), a G (11,3 ± 4,9 vs. 6,2 ± 2,4 H2Ocm/l) és a H (32,3 ± 12,0 vs. 25,1± 6,9 H2Ocm/l) értékét (p<0,001 mindegyik betegcsoportnál), de ez nem járt együtt a gázcserefunckció romlásával. Hasonló patológiás elváltozásokat észleltünk elhízás során a légzésmechanikában és az alveolaris heterogenitásban, amelyek azonban a gázcsere hatékonyságát is rontották. Következtetés: Cukorbetegségben a légzésmechanika romlását a fokozott hypoxiás pulmonalis vasoconstrictio ellensúlyozni képes, ezzel kivédve az intrapulmonalis shunt növekedését és az oxigenizációs képesség romlását. Orv Hetil. 2022; 163(2): 63-73.

SUMMARY

INTRODUCTION

While sustained hyperglicemia affects the smooth muscle tone and the elastin-collagen network, the effect of diabetes mellitus on the function and structure of the airways and the lung parenchyma has not been characterized, and the confounding influence of obesity has not been elucidated.

OBJECTIVE

To reveal the separate and additive roles of diabetes mellitus and obesity on the respiratory function.

METHOD

Non-obese mechanically ventilated patients were categorized as control non-diabetic (n = 80) and diabetic (n = 35) groups. Obese patients with (n = 33) or without (n = 47) associated diabetes were also enrolled. Forced oscillation technique was applied to measure airway resistance (Raw), tissue damping (G), and tissue elastance (H). Capnography was utilized to determine phase 3 slopes and ventilation dead space parameters. Arterial and central venous blood samples were analyzed to assess intrapulmonary shunt fraction (Qs/Qt) and the lung oxygenation index (PaO2/FiO2).

RESULTS

Diabetes without obesity increased the Raw (7.4 ± 5 cmH2O.s/l vs. 3.0 ± 1.7 cmH2O.s/l), G (11.3 ± 4.9 cmH2O/l vs. 6.2 ± 2.4 cmH2O/l), and H (32.3 ± 12.0 cmH2O/l vs. 25.1 ± 6.9 cmH2O/l, (p<0.001 for all), compared with the corresponding control groups. Capnographic phase 3 slope was increased in diabetes without significant changes in PaO2/FiO2 or Qs/Qt. While similar detrimental changes in respiratory mechanics and alveolar heterogeneity were observed in obese patients without diabetes, these alterations also compromised gas exchange.

CONCLUSION

The intrinsic mechanical abnormalities in the airways and lung tissue induced by diabetes are counterbalanced by hypoxic pulmonary vasoconstriction, thereby maintaining intrapulmonary shunt fraction and oxygenation ability of the lungs. Orv Hetil. 2022; 163(2): 63-73.

Inhaled CO2 Concentration While Wearing Face Masks: A Pilot Study Using Capnography

BACKGROUND

Face masks are recommended based on the assumption that they protect against SARS-CoV-2 transmission, however studies on their potential side effects are still lacking. We aimed to evaluate the inhaled air carbon dioxide (CO₂) concentration, when wearing masks.

METHODS

We measured end-tidal CO₂ using professional side-stream capnography, with water-removing tubing, (1) without masks, (2) wearing a surgical mask, and (3) wearing a FFP2 respirator (for 5 minutes each while seated after 10 minutes of rest), in 146 healthy volunteers aged 10 to 90 years, from the general population of Ferrara, Italy. The inhaled air CO₂ concentration was computed as: ([mask volume × end-tidal CO₂] + [tidal volume - mask volume] × ambient air CO₂)/tidal volume.

RESULTS

With surgical masks, the mean CO₂ concentration was 7091 ± 2491 ppm in children, 4835 ± 869 in adults, and 4379 ± 978 in the elderly. With FFP2 respirators, this concentration was 13 665 ± 3655 in children, 8502 ± 1859 in adults, and 9027 ± 1882 in the elderly. The proportion showing a CO₂ concentration higher than the 5000 ppm (8-hour average) acceptable threshold for workers was 41.1% with surgical masks, and 99.3% with FFP2 respirators. Adjusting for age, gender, BMI, and smoking, the inhaled air CO₂ concentration significantly increased with increasing respiratory rate (mean 10 837 ±3712 ppm among participants ⩾18 breaths/minute, with FFP2 respirators), and among the minors.

CONCLUSION

If these results are confirmed, the current guidelines on mask-wearing should be reevaluated.

Improving Capnography Use for Critically Ill Emergency Patients: An Implementation Study

OBJECTIVES

Capnography has established benefit during intubation and cardiopulmonary resuscitation (CPR). Implementation within emergency departments (EDs) has lagged. We sought to address barriers to improve documented capnography use for patients requiring intubation or CPR.

METHODS

A controlled before- and after-implementation study was performed in 2 urban EDs. The control site had an existing policy for capnography use. Interventions for the experimental site included a 5-minute informational video, placement of capnography monitors with a shortened warm-up period in all resuscitation rooms, laminated reminder cards, and feedback during staff meetings. Staff members were surveyed about knowledge before and after the intervention. Records were reviewed for documented capnography use for 3 months before and 6 months after the intervention. Change in documented use at the experimental site was compared with the control site.

RESULTS

At the experimental site, 118 providers participated and 190 records were reviewed; 544 records were reviewed from the control site. There was a significant increase in the proportion of documented capnography use at the experimental site (8% versus 19%, P = 0.04) compared with the control site (64% versus 71%, P = 0.10). However, there was no significant trend over time at the experimental site after the intervention (P = 0.86). Despite high baseline knowledge about capnography, providers had improvements in survey responses regarding indications for intubation and CPR, normal values, and minimum effective values during CPR.

CONCLUSIONS

Documented capnography use increased with simple interventions but with no positive trend. Additional work is needed to improve use, including further evaluation of capnography's implementation in the ED.

The Evaluation of End Tidal Carbon Dioxide Values in Intubated Patients with COVID-19

BACKGROUND

The aim of this study is to establish the value of PETCO2 in COVID-19 patients intubated in emergency department, and its effects on mortality.  Objectives: Between May 15, 2020 and January 15, 2021, The patients aged ≥18 years and diagnosed COVID-19, scheduled for urgent intubation in the emergency department were included.

METHOD

Single-center, prospective and observational study. Age, gender, vital signs, laboratory findings are recorded. Immediately after intubation as measured by the capnography, the initial PETCO2_1 and at post-ventilation 15 min, PETCO2_2 and first, second arterial blood gas analysis are recorded.

RESULTS

The mean age of the 48 patients was 74 years. The PETCO2_1 and PETCO2_2 measurements were statistically significantly different between the patients who survived and those who died (p=0.014, p=0.015). The patients with a high first PETCO2_1 value and a decrease to the normal level survived, but those with a low PETCO2_1 value that could not increase to a normal value died (p=0.038, p=0.031). Increased levels of SpO2, PETCO2_1, PETCO2_2 and PaCO2_2 decreased the risk of mortality, while an increased level of PaO2_2 increased the risk of mortality.

CONCLUSION

Capnography is non-invasive and provides continuous measurement. Assessment of changes in PETCO2 value would contribute to patient survival.

Inhaled CO2 Concentration While Wearing Face Masks: A Pilot Study Using Capnography

BACKGROUND

Face masks are recommended based on the assumption that they protect against SARS-CoV-2 transmission, however studies on their potential side effects are still lacking. We aimed to evaluate the inhaled air carbon dioxide (CO₂) concentration, when wearing masks.

METHODS

We measured end-tidal CO₂ using professional side-stream capnography, with water-removing tubing, (1) without masks, (2) wearing a surgical mask, and (3) wearing a FFP2 respirator (for 5 minutes each while seated after 10 minutes of rest), in 146 healthy volunteers aged 10 to 90 years, from the general population of Ferrara, Italy. The inhaled air CO₂ concentration was computed as: ([mask volume × end-tidal CO₂] + [tidal volume - mask volume] × ambient air CO₂)/tidal volume.

RESULTS

With surgical masks, the mean CO₂ concentration was 7091 ± 2491 ppm in children, 4835 ± 869 in adults, and 4379 ± 978 in the elderly. With FFP2 respirators, this concentration was 13 665 ± 3655 in children, 8502 ± 1859 in adults, and 9027 ± 1882 in the elderly. The proportion showing a CO₂ concentration higher than the 5000 ppm (8-hour average) acceptable threshold for workers was 41.1% with surgical masks, and 99.3% with FFP2 respirators. Adjusting for age, gender, BMI, and smoking, the inhaled air CO₂ concentration significantly increased with increasing respiratory rate (mean 10 837 ±3712 ppm among participants ⩾18 breaths/minute, with FFP2 respirators), and among the minors.

CONCLUSION

If these results are confirmed, the current guidelines on mask-wearing should be reevaluated.

The Effectiveness of Capnography Versus Pulse Oximetry in Detecting Respiratory Adverse Events in the Postanesthesia Care Unit (PACU): A Narrative Review and Synthesis

PURPOSE

The objective of this review was to evaluate the effectiveness of capnography monitoring versus standard monitoring of pulse oximetry in detecting respiratory adverse events in nonintubated pediatric and adult postanesthesia care unit (PACU) patients.

DESIGN

Experimental, quasi-experimental, and observational studies examining pulse oximetry and capnography in adult and pediatric patients in the PACU were included in this systematic review.

METHODS

An initial search of MEDLINE and CINAHL, PubMed, Web of Science, Prospero, Google Scholar, and Cochrane was undertaken to identify articles on the topic. The text words contained in the titles and abstracts of relevant articles, and the index terms used to describe the articles were used to develop a full search strategy in July 2019. Reference lists of studies included at critical appraisal stage were hand-searched. Studies published in English from 1978 onward were included.

FINDINGS

Meta-analysis was not possible due to variation in outcome measurements; therefore, results are presented in narrative form. Four studies were included in the review: 1 randomized controlled trial (RCT) and 3 observational cross-sectional studies. The RCT was considered of moderate to high quality, and the observational cross-sectional studies were of high quality. The main findings of this review suggest that there is limited high-quality evidence that capnography improves detection of respiratory adverse events in the PACU versus pulse oximetry.

CONCLUSIONS

The lack of RCTs and varied outcomes measures in the 4 studies reviewed meant that meta-analysis was not possible. Early detection of respiratory adverse events afforded by the addition of PETCO₂ to SpO₂ in the PACU was seen in these studies. More research is needed to determine if widespread implementation of capnography in addition to pulse oximetry would reduce severity of respiratory related adverse events in the PACU through more timely identification.

Digitization and Analysis of Capnography Using Image Processing Technique

The study of carbon dioxide expiration is called capnometry. The graphical representation of capnometry is called capnography. There is a growing interest in the usage of capnography as the usage has expanded toward the study of metabolism, circulation, lung perfusion and diffusion, quality of spontaneous respiration, and patency of airways outside of its typical usage in the anesthetic and emergency medicine field. The parameters of the capnograph could be classified as carbon dioxide (CO₂) concentration and time points and coordinates, slopes angle, volumetric studies, and functional transformation of wave data. Up to date, there is no gold standard device for the calculation of the capnographic parameters. Capnography digitization using the image processing technique could serve as an option. From the algorithm we developed, eight identical breath waves were tested by four investigators. The values of the parameters chosen showed no significant difference between investigators. Although there were no significant differences between any of the parameters tested, there were a few related parameters that were not calculable. Further testing after refinement of the algorithm could be done. As more capnographic parameters are being derived and rediscovered by clinicians and researchers alike for both lung and non-lung-related diseases, there is a dire need for data analysis and interpretation. Although the proposed algorithm still needs minor refinements and further large-scale testing, we proposed that the digitization of the capnograph via image processing technique could serve as an intellectual option as it is fast, convenient, easy to use, and efficient.

Predicting Prolonged Apnea During Nurse-Administered Procedural Sedation: Machine Learning Study

BACKGROUND

Capnography is commonly used for nurse-administered procedural sedation. Distinguishing between capnography waveform abnormalities that signal the need for clinical intervention for an event and those that do not indicate the need for intervention is essential for the successful implementation of this technology into practice. It is possible that capnography alarm management may be improved by using machine learning to create a "smart alarm" that can alert clinicians to apneic events that are predicted to be prolonged.

OBJECTIVE

To determine the accuracy of machine learning models for predicting at the 15-second time point if apnea will be prolonged (ie, apnea that persists for >30 seconds).

METHODS

A secondary analysis of an observational study was conducted. We selected several candidate models to evaluate, including a random forest model, generalized linear model (logistic regression), least absolute shrinkage and selection operator regression, ridge regression, and the XGBoost model. Out-of-sample accuracy of the models was calculated using 10-fold cross-validation. The net benefit decision analytic measure was used to assist with deciding whether using the models in practice would lead to better outcomes on average than using the current default capnography alarm management strategies. The default strategies are the aggressive approach, in which an alarm is triggered after brief periods of apnea (typically 15 seconds) and the conservative approach, in which an alarm is triggered for only prolonged periods of apnea (typically >30 seconds).

RESULTS

A total of 384 apneic events longer than 15 seconds were observed in 61 of the 102 patients (59.8%) who participated in the observational study. Nearly half of the apneic events (180/384, 46.9%) were prolonged. The random forest model performed the best in terms of discrimination (area under the receiver operating characteristic curve 0.66) and calibration. The net benefit associated with the random forest model exceeded that associated with the aggressive strategy but was lower than that associated with the conservative strategy.

CONCLUSIONS

Decision curve analysis indicated that using a random forest model would lead to a better outcome for capnography alarm management than using an aggressive strategy in which alarms are triggered after 15 seconds of apnea. The model would not be superior to the conservative strategy in which alarms are only triggered after 30 seconds.

Carbon dioxide monitoring in the newborn infant

Carbon dioxide (CO₂ ) monitoring is vital during mechanical ventilation of newborn infants, as morbidity increases when CO₂ levels are inappropriate. Our aim was to review the uses and limitations of such noninvasive monitoring methods. Colorimetry is primarily utilized during resuscitation to determine whether successful intubation has occurred. False negative and positive results can however lead to delays in detecting tracheal versus esophageal intubation. Transcutaneous carbon dioxide sensors have limited use during resuscitation, but can be utilized to provide continuous trend data during on-going ventilation. End-tidal capnography can provide clinicians with quantitative end-tidal CO₂ (EtCO₂ ) values and a continuous real-time capnogram waveform trace. These devices are becoming more widely accepted for use in the neonatal population as the new devices are lightweight with minimal additional dead space. Nevertheless, they have been reported to have variable accuracy when compared to arterial CO₂ measurements, however, divergence of results may be related to disease severity rather than technological limitations. During resuscitation EtCO₂ can be detected by capnography more rapidly than by colorimetry. Furthermore, capnography can be currently utilized in neonatal research settings to determine the physiological dead space and ventilation inhomogeneity, and thus has potential to be beneficial to clinical care. In conclusion, novel modes of noninvasive carbon dioxide monitoring can be safely and reliably utilized in newborn infants during mechanical ventilation. Future randomized trials should aim to address which device provides the most optimal form of monitoring in different clinical contexts.

Rationale for developing tunable laser spectroscopy (TLS) technology for high resolution real-time carbon dioxide monitoring (capnography) in human breath

Real-time monitoring of exhaled carbon dioxide (CO₂), also known as capnography, is a valuable hospital tool for assessing patient health during anesthesia and in both the emergency department and critical care units. The fundamental measurement is referred to as end-tidal carbon dioxide concentration that reflects pulmonary gas exchange of CO₂representing systemic metabolism. The shape of the exhaled CO₂concentration for individual inhalation/exhalation breath cycles can offer additional information regarding lung function, airway obstruction, alveolar ventilation, and worsening disease. The most frequent use is to indicate appropriate placement of an endotracheal tube but and it is also employed in the assessment of disease severity and response to treatment (e.g. asthma). Other applications include outpatient monitoring with oxygen supplementation (nasal cannula) and continuous positive airway pressure control for sleep apnea. As technology has evolved, CO₂measurements have become more mobile; capnography systems are now used by emergency medical services personnel for verifying proper placement of airway devices in 'pre-hospital' environments. The use of CO₂diagnostics has evolved to identify breathing system disruptions in 'on-demand' regulator/masks equipment, both in medical and occupational settings. Most recently, miniaturized tunable laser spectroscopy sensors have been implemented for assessing pilot breathing in high-performance military aircraft. This editorial describes the use of CO₂breath sensors and proposes some new applications based on miniaturized sensors that can be directly inserted into breathing masks.

Capnography use in the critical care setting: why do clinicians fail to implement this safety measure?

Tracheal intubation is among the most frequently performed manoeuvres in the critical care setting, and can be life-saving in critical illness, though also associated with serious adverse events such as oesophageal intubation or tracheal tube obstruction, displacement, or disconnection from the ventilator. A key finding of the 4th National Audit Project (NAP4) was identification of waveform capnography as the single intervention with the highest potential for reducing morbidity and mortality during tracheal intubation and maintenance of an artificial airway. In the INTUBE study, penetration of capnography into ICUs was low, and was not in use in 70% of the episodes of oesophageal intubation. To reduce harm and avoidable death, there is a need for a global initiative to increase access to and use of capnography in ICUs.

Lung function and stress echocardiography in pulmonary arterial hypertension: a cross-sectional study

BACKGROUND

The mechanism of exercise limitation in idiopathic pulmonary arterial hypertension (IPAH) is not fully understood. The role of hemodynamic alterations is well recognized, but mechanical, ventilatory and gasometric factors may also contribute to reduction of exercise capacity in these individuals.

OBJECTIVE

To investigate whether there is an association between ventilatory pattern and stress Doppler echocardiography (SDE) variables in IPAH patients.

DESIGN AND SETTING

Single-center prospective study conducted in a Brazilian university hospital.

METHODS

We included 14 stable IPAH patients and 14 age and sex-matched controls. Volumetric capnography (VCap), spirometry, six-minute walk test and SDE were performed on both the patients and the control subjects. Arterial blood gases were collected only from the patients. The IPAH patients and control subjects were compared with regard to the abovementioned variables.

RESULTS

The mean age of the patients was 38.4 years, and 78.6% were women. The patients showed hypocapnia, and in spirometry 42.9% presented forced vital capacity (FVC) below the lower limit of normality. In VCap, IPAH patients had higher respiratory rates (RR) and lower elimination of CO2 in each breath. There was a significant correlation between reduced FVC and the magnitude of increases in tricuspid regurgitation velocity (TRV). In IPAH patients, VCap showed similar tidal volumes and a higher RR, which at least partially explained the hypocapnia.

CONCLUSIONS

The patients with IPAH showed hypocapnia, probably related to their higher respiratory rate with preserved tidal volumes; FVC was reduced and this reduction was positively correlated with cardiac output.

Dopamine Reverses Lung Function Deterioration After Cardiopulmonary Bypass Without Affecting Gas Exchange

OBJECTIVE

To investigate the effects of dopamine on the adverse pulmonary changes after cardiopulmonary bypass.

DESIGN

A prospective, nonrandomized clinical investigation.

SETTING

A university hospital.

PARTICIPANTS

One hundred fifty-seven patients who underwent elective cardiac surgery that required cardiopulmonary bypass.

INTERVENTIONS

Fifty-two patients were administered intravenous infusion of dopamine (3 µg/kg/min) for five minutes after weaning from cardiopulmonary bypass; no intervention was applied in the other 105 patients.

MEASUREMENTS AND MAIN RESULTS

Measurements were performed under general anesthesia and mechanical ventilation before cardiopulmonary bypass, after cardiopulmonary bypass, and after the intervention. In each protocol stage, forced oscillatory lung impedance was measured to assess airway and tissue mechanical changes. Mainstream capnography was performed to assess ventilation- and/or perfusion-matching by calculating the normalized phase-3 slopes of the time and volumetric capnograms and the physiologic deadspace. Arterial and central venous blood samples were analyzed to characterize lung oxygenation and intrapulmonary shunt. After cardiopulmonary bypass, dopamineinduced marked improvements in airway resistance and tissue damping, with relatively small decreases in lung tissue elastance. These changes were associated with decreases in the normalized phase-3 slopes of the time and volumetric capnograms. The inotrope had no effect on physiologic deadspace, intrapulmonary shunt, or lung oxygenation.

CONCLUSION

Dopamine reversed the complex detrimental lung mechanical changes induced by cardiopulmonary bypass and alleviated ventilation heterogeneities without affecting the physiologic deadspace or intrapulmonary shunt. Therefore, dopamine has a potential benefit on the gas exchange abnormalities after weaning from cardiopulmonary bypass.

Availability of portable capnometers in children with tracheostomy

BACKGROUND

A capnometer is a noninvasive monitor that is used to assess patients' respiratory status. This study was performed to evaluate the availability of a portable capnometer in children with tracheostomy.

METHODS

This retrospective study included children with tracheostomy who were treated at the Osaka Women's and Children's Hospital Osaka, Japan, from 1 September 2018 to 31 October 2019. We assessed the correlation between the partial pressure of venous carbon dioxide (PvCO₂ ) and end-tidal carbon dioxide tension (EtCO₂ ) using a portable capnometer (EMMA; Masimo, Irvine, CA, USA).

RESULTS

Nine infants and 43 simultaneous PvCO₂ -EtCO₂ pairs were analyzed. The correlation coefficient of these pairs was 0.87 (95% confidence interval, 0.77-0.93; P < 0.001). The Bland-Altman plot showed that EtCO₂ was on average 10.0 mmHg lower than its paired PvCO₂ value (95% limits of agreement, 1.0-19.1). The difference between PvCO₂ and EtCO₂ was significantly greater in patients on ventilators.

CONCLUSIONS

The portable capnometer evaluated in this study (EMMA) was readily available and useful for assessment of the respiratory condition in children with tracheostomy.

Correlation of End-Tidal Carbon Dioxide with Arterial Carbon Dioxide in Mechanically Ventilated Neonates: A Scoping Review

Monitoring CO2 levels in intubated neonates is highly relevant in the face of complications associated with altered CO2 levels. Thus, this review aims to present the scientific evidence in the literature regarding the correlation between arterial carbon dioxide measured by non-invasive methods in newborns submitted to invasive mechanical ventilation. The search was carried out from January 2020 to January 2021, in the Scopus, Medline, The Cochrane Library, Web of Science, CINAHL and Embase databases. Also, a manual search of the references of included studies was performed. The main descriptors used were: "capnography," "premature infant," "blood gas analysis," and "mechanical ventilation." As a result, 221 articles were identified, and 18 were included in this review. A total of 789 newborns were evaluated, with gestational age between 22.8 and 42.2 weeks and birth weight between 332 and 4790 g. Capnometry was the most widely used non-invasive method. In general, the correlation and agreement between the methods evaluated in the studies were strong/high. The birth weight did not influence the results. The gestational age of fewer than 37 weeks implied, in its majority, a moderate correlation and agreement. Therefore, we can conclude that there was a predominance of a strong correlation between arterial blood gases and non-invasive methods, although there are variations found in the literature. Even so, the results were promising and may provide valuable data for future studies, which are necessary to consolidate non-invasive methods as a reliable and viable alternative to arterial blood gasometry.