Monitoring Gas Exchange

Critical illness can threaten the adequacy of O₂ delivery or CO₂ excretion. Monitoring seeks to identify the adequacy of oxygenation and ventilation and to detect deterioration early. Advances in oximetry, capnography, and transcutaneous CO₂ monitoring offer new opportunities for more accurate estimation of gas exchange, noninvasive monitoring of parameters previously not amenable (eg, total hemoglobin measurement), detection of disease, and prediction of fluid responsiveness.

Obesity and diabetes: similar respiratory mechanical but different gas exchange defects

Diabetes mellitus increases smooth muscle tone and causes tissue remodeling, affecting elastin and collagen. Although the lung is dominated by these elements, diabetes is expected to modify the airway function and respiratory tissue mechanics. Therefore, we characterized the respiratory function in patients with diabetes with and without associated obesity. Mechanically ventilated patients with normal body shapes were divided into the control nondiabetic (n = 73) and diabetic (n = 31) groups. The other two groups included obese patients without diabetes (n = 43) or with diabetes (n = 30). The mechanical properties of the respiratory system were determined by forced oscillation technique. Airway resistance (Raw), tissue damping (G), and tissue elastance (H) were assessed by forced oscillation. Capnography was applied to determine phase 3 slopes and dead space indices. The intrapulmonary shunt fraction (Qs/Qt) and the lung oxygenation index (Pa_O2/FI_O2) were estimated from arterial and central venous blood samples. Compared with the corresponding control groups, diabetes alone increased the Raw (7.6 ± 6 cmH₂O.s/l vs. 3.1 ± 1.9 cmH₂O.s/l), G (11.7 ± 5.5 cmH₂O/l vs. 6.5 ± 2.8 cmH₂O/l), and H (31.5 ± 11.8 cmH₂O/l vs. 24.2 ± 7.2 cmH₂O/l (P < 0.001 for all). Diabetes increased the capnographic phase 3 slope, whereas Pa_O2/FI_O2 or Qs/Qt was not affected. Obesity alone caused similar detrimental changes in respiratory mechanics and alveolar heterogeneity, but these alterations also compromised gas exchange. We conclude that diabetes-induced intrinsic mechanical abnormalities are counterbalanced by hypoxic pulmonary vasoconstriction, which maintained intrapulmonary shunt fraction and oxygenation ability of the lungs.

A retrospective analysis of CO2 derived goal-directed perfusion variables under normothermic conditions: do we need to re-evaluate threshold values?

This study investigated if current predictive values for increased lactate formation: VCO₂i > 60 ml min^-1 m^-2, respiratory quotient (RQ) > 0.90, and DO₂/VCO₂ < 5.0, are valid under normothermic conditions. CO₂ derived parameters were analyzed in 91 patients undergoing normothermic CABG and related to increase of blood lactate concentrations during bypass. In this study population, 85 patients (93%) had a median VCO₂i above 60 ml min^-1 m^-2 and 53 patients (58%) had a DO₂/VCO₂ ⩽ 5.0. Eighteen patients (20%) had a median RQ ⩾ 0.90, but RQ remained with a maximum value of 0.94 below the biological threshold of 1.0. Increase of lactate concentrations remained without clinical significance and showed weak correlations with VCO₂i (rs = 0.277, p = 0.008) and RQ (rs = 0.346, p = 0.001).The cohort was separated for the different CO₂ variables by their median value to compare increase in lactate concentration. Patients with a high VCO₂i (⩾70 ml min^-1 m^-2) and a high RQ (⩾0.82) showed significant higher increase in lactate concentration compared to patients with VCO₂i < 70 ml min^-1 m^-2 (p = 0.004), and a RQ < 0.82 (p = 0.012). Groups separated by a median DO₂/VCO₂ of 4.8 did not show a difference in increase of lactate concentration in blood. In summary, specific CO₂ derived threshold values for the prediction of lactate formation, which have been reported in other studies, cannot be confirmed with our findings. However, a CO₂ production ⩾70 ml min^-1 m^-2 and a RQ ⩾ 0.82 in this study population were correlated with increased lactate formation. Because CO₂ production during bypass depends on patient temperature, a different cutoff value, that may take into account the influence of demographic variables, should be determined during normothermic CPB.

Optimizing airway management and ventilation during prehospital advanced life support in out-of-hospital cardiac arrest: A narrative review

Airway management and ventilation are essential components of cardiopulmonary resuscitation to achieve oxygen delivery in order to prevent hypoxic injury and increase the chance of survival. Weighing the relative benefits and downsides, the best approach is a staged strategy; start with a focus on high-quality chest compressions and defibrillation, then optimize mask ventilation while preparing for advanced airway management with a supraglottic airway device. Endotracheal intubation can still be indicated, but has the largest downsides of all advanced airway techniques. Whichever stage of airway management, ventilation and chest compression quality should be closely monitored. Capnography has many advantages and should be used routinely. Optimizing ventilation strategies, harmonizing ventilation with mechanical chest compression devices, and implementation in complex and stressful environments are challenges we need to face through collaborative innovation, research, and implementation.

Predictive Utility of End-Tidal Carbon Dioxide on Defibrillation Success in Out-of-Hospital Cardiac Arrest

INTRODUCTION

The likelihood of survival from ventricular fibrillation (VF) declines 7%-10% per minute until successful defibrillation. When VF duration is prolonged, immediate defibrillation of the ischemic myocardium is less likely to result in ROSC, and repeated unsuccessful defibrillations are associated with post-resuscitation myocardial dysfunction. Thus, the timing of defibrillation should be based upon the probability of shock success-a function of VF duration. Unfortunately, VF duration is often unknown in out-of-hospital cardiac arrest (OHCA) and a better predictor of shock success is needed.

OBJECTIVE

To assess the ability of end-tidal carbon dioxide (EtCO₂) to predict successful defibrillation in OHCA.

METHODS

This retrospective study included adult patients among four EMS systems who experienced non-traumatic OHCA from August, 2015-July, 2017 and received one or more defibrillations. First and succedent shocks were analyzed separately. First shocks represented EMS-attempted defibrillation of patients who had not received a prior AED shock, whereas succedent shocks included all shocks subsequent to the first. Logistic regression provided odds ratios (OR) for first shocks resulting in ROSC, while a generalized estimating equation was used to analyze succedent shocks.

RESULTS

Among 324 patients, 869 shocks were delivered by EMS (153 first and 716 succedent shocks). Layperson CPR was performed in 48.1% of cases and 21.6% received an AED shock before EMS arrival. First defibrillation ROSC was more likely with layperson CPR (OR = 4.41;p = 0.01) and increasing EtCO₂ (OR = 1.03/mmHg;p = 0.01). No other variables were statistically significant. Notably, only one patient with EtCO₂ < 20 mmHg was successfully defibrillated on the first shock. The probability of ROSC was higher with increasing values of EtCO₂ when layperson CPR was provided, yet remained relatively unchanged across all values of EtCO₂ ≥ 20 mmHg without layperson CPR. The optimal threshold first shock EtCO₂ was 27 and 32 mmHg for those with/without layperson CPR, respectively. EtCO₂ was not a predictor of ROSC for succedent shocks.

CONCLUSIONS

An optimal defibrillation threshold EtCO2 of 27 and 32 mmHg was observed for patients with and without layperson CPR, respectively. Further studies are warranted to verify these results and to evaluate the clinical effect of delaying defibrillation in favor of chest compressions until these values are attained.

Effects of Zero PEEP and < 1.0 FIO2 on SpO2 and PETCO2 During Open Endotracheal Suctioning

BACKGROUND

Hyperoxygenation and hyperinflation, preferably with a mechanical ventilator, is the most commonly used technique to prevent the adverse effects of open endotracheal suctioning on arterial oxygenation and pulmonary volume. However, limited data are available on the effects of oxygen concentrations < 100% and PEEP with zero end-expiratory pressure (0 PEEP) to improve oxygenation and to maintain adequate ventilation during open endotracheal suctioning. The aim of this study was to analyze the behavior of [Formula: see text] and end-tidal CO₂ pressure ([Formula: see text]) in open endotracheal suctioning using the 0 PEEP technique with baseline [Formula: see text] (0 PEEP baseline [Formula: see text]) and 0 PEEP + hyperoxygenation of 20% above the baseline value (0 PEEP [Formula: see text] + 0.20) in critically ill subjects receiving mechanical ventilation.

METHODS

This was a prospective, randomized, single-blind crossover study, for which 48 subjects with various clinical and surgical conditions were selected; of these, 38 subjects completed the study. The subjects were randomized for 2 interventions: 0 PEEP baseline [Formula: see text] and 0 PEEP [Formula: see text] + 0.20 during the open endotracheal suctioning procedure. Oxygenation was assessed via oxygen saturation as measured with pulse oximetry ([Formula: see text]), and changes in lung were monitored via [Formula: see text] using volumetric capnography.

RESULTS

In the intragroup analysis with 0 PEEP baseline [Formula: see text], there was no significant increase after open endotracheal suctioning in either [Formula: see text] (P = .63) or [Formula: see text] (P = .11). With 0 PEEP [Formula: see text] + 0.20, there was a significant increase in [Formula: see text] (P < .001), with no significant changes in [Formula: see text] (P = .55). In the intergroup comparisons, there was a significant increase compared to the basal values only with the 0 PEEP + 0.20 method at 1 min after hyperoxygenation (P < .001), post-immediately (P < .001), at 1 min after (P < .001), and at 2 min after open endotracheal suctioning (P < .001).

CONCLUSIONS

The appropriate indication of the hyperinflation strategy via mechanical ventilation using 0 PEEP with or without hyperoxygenation proved to be efficient to maintain [Formula: see text] and [Formula: see text] levels. These results suggest that the technique can minimize the loss of lung volume due to open endotracheal suctioning. (ClinicalTrials.gov registration NCT02440919).

Monitoring Breathing Frequency, Pattern, and Effort

Monitoring respiratory values such as breathing frequency, minute ventilation, breathing effort, and dyspnea are common in acute care. There is evidence that accurate monitoring and interpretation of these values leads to early identification and treatment of impending respiratory failure. Despite this evidence, some values, such as breathing frequency, are largely undervalued in the clinical setting. The undervaluation of breathing frequency is complex and will require a multifaceted approach, including education and improved technology, to reestablish its clinical potential. Many questions remain regarding how to most efficiently and effectively monitor other respiratory values, like noninvasive minute volume and breathing effort, as well. As technology continues to improve alongside the understanding of respiratory physiology, clinicians are able to apply basic clinical assessment skills and technology together to improve patient safety and outcomes.

Excluding Pulmonary Embolism with End-tidal Carbon Dioxide: Accuracy, Cost, and Harm Avoidance

A non-randomized single center prospective, descriptive, correlational design was used to determine what end-tidal carbon dioxide (EtCO₂) level provided the best sensitivity, specificity, and negative predictive value to exclude pulmonary embolism (PE) diagnosis in hemodynamically stable hospitalized adults (n = 111). The financial impact and harm avoidance of adding EtCO₂ to the PE diagnostic process also were examined. PE diagnosis was determined by computed tomography pulmonary angiography (CTPA). PE prevalence was 18.9%. Mean±SD EtCO₂ was lower for PE positive than negative participants (28 ± 7.8 to 33 ± 8.1 mmHg respectively 95% CI: 1.22-8.96; P = .01). For PE exclusion, an EtCO₂ cutoff ≥42 mmHg yielded 100% sensitivity, 12.2% specificity, and 100% negative predictive value. For every six inpatients assessed with EtCO₂, one could be saved from unnecessary CTPA. Eliminating unnecessary CTPA removes the potential harm associated with radiation and intravenous contrast exposure. Additionally, an EtCO₂ cutoff ≥42 mmHg could eliminate ~$88,000/year in healthcare waste at this institution.

Impact of capnography on patient safety in high- and low-income settings: a scoping review

BACKGROUND

Capnography is universally accepted as an essential patient safety monitor in high-income countries (HICs) yet is often unavailable in low and middle-income countries (LMICs). Increasing capnography availability has been proposed as one of many potential approaches to improving perioperative outcomes in LMICs. This scoping review summarises the existing literature on the effect of capnography on patient outcomes to help prioritise interventions and guide expansion of capnography in LMICs.

METHODS

We searched MEDLINE and EMBASE databases for articles published between 1980 and March 2019. Studies that assessed the impact of capnography on morbidity, mortality, or the use of airway interventions both inside and outside the operating room were included.

RESULTS

The search resulted in 7445 unique papers, and 31 were included for analysis. Retrospective and non-randomised data suggest capnography use may improve outcomes in the operating room, ICU, and emergency department, and during resuscitation. Prospective data on capnography use for procedural sedation suggest earlier detection of hypoventilation and a reduction in haemoglobin desaturation events. No randomised studies exist that assess the impact of capnography on patient outcomes.

CONCLUSION

Despite widespread endorsement of capnography as a mandatory perioperative monitor, rigorous data demonstrating its impact on patient outcomes are limited, especially in LMICs. The association between capnography use and a reduction in serious airway complications suggests that closing the capnography gap in LMICs may represent a significant opportunity to improve patient safety. Additional data are needed to quantify the global capnography gap and better understand the barriers to capnography scale-up in LMICs.

Comparison of mainstream (Capnostat 5) and two low-flow sidestream capnometers (VM-2500-S and Capnostream) in spontaneously breathing rabbits anesthetized with a Bain coaxial breathing system

OBJECTIVE

To evaluate agreement with PaCO₂ of two low sampling rate sidestream capnometers and a mainstream capnometer in rabbits and the effect of using high fresh gas flow from a Bain coaxial breathing system.

STUDY DESIGN

Prospective, crossover study.

ANIMALS

A total of 10 New Zealand White rabbits weighing 3.4 ± 0.3 kg [mean ± standard deviation (SD)].

METHODS

Two sidestream analyzers (Viamed VM-2500-S and Capnostream 35) with a sampling rate of 50 mL minute^-1 and a mainstream capnometer (Capnostat 5) were tested. All capnometers used infrared spectroscopy and advanced microprocessor technology. Rabbits were anesthetized and intubated with noncuffed endotracheal tubes of 3 mm internal diameter and adequate seal. A sidestream sampling adapter or the mainstream capnometer was attached to the endotracheal tube and connected to a Bain coaxial breathing system. Oxygen (1.5 L minute^-1) delivered sevoflurane to maintain anesthesia. An auricular artery catheter allowed blood sampling for PaCO₂ analysis corrected to rectal temperature. Inspired and end-tidal carbon dioxide (Pe'CO₂) measurements were recorded during blood sample withdrawal. From each rabbit, 10 paired PaCO₂/Pe'CO₂ measurements were obtained. Each rabbit was recovered from anesthesia and was anesthetized again with an alternate capnometer after 1 week. Data were analyzed using Bland-Altman and two-way anova for repeated measures.

RESULTS

Analysis included 100 paired samples. Negative bias reflects underestimation of PaCO₂. Bland-Altman mean (±1.95 SD) was -16.7 (-35.2 to 1.8) mmHg for Capnostat 5, -27.9 (-48.6 to -7.2) mmHg for Viamed, and -18.1 (-34.3 to -1.9) mmHg for Capnostream. Viamed PaCO₂-Pe'CO₂ gradient was greater than other two capnometers.

CONCLUSIONS

All three capnometers underestimated PaCO₂. Capnostat 5 and Capnostream performed similarly.

CLINICAL RELEVANCE

These capnometers underestimated PaCO₂ in spontaneously breathing rabbits anesthetized using a Bain coaxial breathing system with high fresh gas flows.

Capnography monitoring of non-anesthesiologist provided sedation during percutaneous endoscopic gastrostomy placement: A prospective, controlled, randomized trial

BACKGROUND AND AIM

A number of studies were able to show a reduction of hypoxemia episodes during procedural sedation through the use of capnography (CA). The present study investigates the number of episodes of hypoxemia during percutaneous endoscopic gastrostomy (PEG) placement with propofol sedation comparing standard monitoring (SM) versus SM with additional CA surveillance.

METHODS

In this single center randomized controlled trial, 150 patients were prospectively randomized 1:1 in either the SM group or the CA group after stratification for ASA class, PEG method (push or pull method), presence of head and neck tumor, and tracheostomy. CA analysis was performed for all patients but was blinded for the endoscopic team in the SM group.

RESULTS

In the SM group, 57% episodes of hypoxemia (SpO₂  < 90% for > 15 s) and 41% episodes of severe hypoxemia (SpO₂  < 85% for > 15 s) were observed in comparison with 28% and 20% in the CA group, respectively. Odds ratios for hypoxemia and severe hypoxemia were 0.29 (confidence interval 0.15-0.57; P = 0.0005) and 0.35 (confidence interval 0.17-0.73; P = 0.008) in favor of the CA group. On average, CA was able to detect imminent mild and severe hypoxemia 83 and 99 s before standard monitoring. Standard monitoring represented an independent risk factor for hypoxemia and severe hypoxemia.

CONCLUSIONS

Respiratory complications of sedation during PEG placement are frequent events. CA is able to detect imminent hypoxemia at an early time point. This allows an early intervention and consecutively the avoidance of mild and severe hypoxemia. Therefore, CA monitoring can be recommended particularly during PEG insertion procedures.

Pilot Study to Compare the Use of End-Tidal Carbon Dioxide-Guided and Diastolic Blood Pressure-Guided Chest Compression Delivery in a Swine Model of Neonatal Asphyxial Cardiac Arrest

Background

The American Heart Association recommends use of physiologic feedback when available to optimize chest compression delivery. We compared hemodynamic parameters during cardiopulmonary resuscitation in which either end‐tidal carbon dioxide (ETCO₂) or diastolic blood pressure (DBP) levels were used to guide chest compression delivery after asphyxial cardiac arrest.

Methods and Results

One‐ to 2‐week‐old swine underwent a 17‐minute asphyxial‐fibrillatory cardiac arrest followed by alternating 2‐minute periods of ETCO₂‐guided and DBP‐guided chest compressions during 10 minutes of basic life support and 10 minutes of advanced life support. Ten animals underwent resuscitation. We found significant changes to ETCO₂ and DBP levels within 30 s of switching chest compression delivery methods. The overall mean ETCO₂ level was greater during ETCO₂‐guided cardiopulmonary resuscitation (26.4±5.6 versus 22.5±5.2 mm Hg; P=0.003), whereas the overall mean DBP was greater during DBP‐guided cardiopulmonary resuscitation (13.9±2.3 versus 9.4±2.6 mm Hg; P=0.003). ETCO₂‐guided chest compressions resulted in a faster compression rate (149±3 versus 120±5 compressions/min; P=0.0001) and a higher intracranial pressure (21.7±2.3 versus 16.0±1.1 mm Hg; P=0.002). DBP‐guided chest compressions were associated with a higher myocardial perfusion pressure (6.0±2.8 versus 2.4±3.2; P=0.02) and cerebral perfusion pressure (9.0±3.0 versus 5.5±4.3; P=0.047).

Conclusions

Using the ETCO₂ or DBP level to optimize chest compression delivery results in physiologic changes that are method‐specific and occur within 30 s. Additional studies are needed to develop protocols for the use of these potentially conflicting physiologic targets to improve outcomes of prolonged cardiopulmonary resuscitation.

Maximum Value of End-Tidal Carbon Dioxide Concentrations during Resuscitation as an Indicator of Return of Spontaneous Circulation in out-of-Hospital Cardiac Arrest

Background: The end-tidal carbon dioxide (ETCO₂) concentration during resuscitation (CPR) of an out-of-hospital cardiac arrest (OHCA) has an increasingly well-known prognostic value. Nevertheless, few studies have investigated its maximum value in different etiologies. Methods: It was a retrospective, observational, multicentre study from the French OHCA Registry. All adult OHCA with a known maximum value of ETCO₂ during CPR were included. The primary end-point was to determine the area under the receiver operating characteristic curve (AUROC) of the maximum value of ETCO₂ during resuscitation for the return of spontaneous circulation (ROSC). Results: Of the 53,048 eligible subjects from 2011 to 2018, ETCO₂ was known in 32,249 subjects (61%). Among them, there were 9.2% of traumatic OHCA, 37.7% of suspected cardiac etiology and 16.4% of suspected respiratory etiology. The AUROC of maximum value of ETCO₂ during CPR to achieve ROSC was 0.887 95CI [0.875-0.898] in traumatic OHCA, 0.772 95CI [0.765-0.780] in suspected cardiac etiology and 0.802 95CI [0.791-0.812] in suspected respiratory etiology. The threshold with no survivors at d-30 was <10 mmHg for traumatic etiologies and <6 mmHg for suspected cardiac and respiratory causes. The probability of ROSC increased with the value of ETCO₂ in the 3 etiologies studied. Conclusions: The maximum value of ETCO₂ during OHCA resuscitation was strongly associated with ROSC, especially in the case of a traumatic cause. This suggests that a single elevated ETCO₂ value, regardless of time, could help to predict the outcome.

Implementation Science: Incorporating Obstructive Sleep Apnea Screening and Capnography Into Everyday Practice

PURPOSE

This article describes the implementation and maintenance of obstructive sleep apnea (OSA) screening and capnography monitoring.

DESIGN

A quality improvement project.

METHODS

A multidisciplinary team provided staff education to three perianesthesia care units. Using the STOP-Bang screening tool, five or more positive responses indicated high risk for OSA. A postanesthesia care unit audit tool tracked STOP-Bang scores, capnography use, hypoventilation events, nursing interventions, and respiratory complications.

FINDINGS

Among 314 patients with OSA, 36% were identified as high risk. Nurses used capnography on 76% of OSA patients and were able to readily identify hypoventilation and intervene. Respiratory complications occurred in 10.8% (n = 34) requiring a higher level of care. Postimplementation, all six postanesthesia care units employ this best practice.

CONCLUSIONS

Perianesthesia nurses found OSA screening and capnography easy to incorporate into nursing practice. This process can reduce respiratory complications in the surgical patient with OSA. An Evidence-Based Practice Fellowship Program facilitated this practice change.

Comparison of End-Tidal, Arterial, Venous, and Transcutaneous PCO2

BACKGROUND

We investigated the measurement of end-tidal partial pressure of carbon dioxide (P_ETCO2 ) with a capnometer in patients with respiratory failure, and we determined whether this technique could provide an alternative to measurement of P_aCO2 using arterial blood gas analysis in the clinical setting.

METHODS

We measured P_ETCO2 in subjects with hypoxemic and hypercarbic respiratory failure using a capnometer. We simultaneously measured P_aCO2 , venous partial pressure of carbon dioxide (P_v̄CO2 ), and transcutaneously measured partial pressure P_CO2 (P_tcCO2 ). We analyzed agreements among these parameters with Bland-Altman analysis. We obtained 30 samples from subjects with hypoxemic respiratory failure and 30 samples from subjects with hypercarbic respiratory failure.

RESULTS

Thirty subjects with hypoxemic respiratory failure and 18 subjects with hypercarbic respiratory failure participated in this study. Significant relationships were found between P_ETCO2 and P_aCO2 , between P_tcCO2 and P_aCO2 , and between P_v̄CO2 and P_aCO2 . Bland-Altman analysis of P_ETCO2 and P_aCO2 in all subjects revealed a bias of 6.48 mm Hg (95% CI 4.93-8.03, P < .001) with a precision of 6.01 mm Hg. Bland-Altman analysis of P_ETCO2 and P_aCO2 with hypoxemic respiratory failure revealed a bias of 5.14 mm Hg (95% CI 3.35-6.93, P < .001) with a precision of 4.80 mm Hg. Bland-Altman analysis of P_ETCO2 and P_aCO2 in subjects with hypercarbic respiratory failure revealed a bias of 7.83 mm Hg (95% CI 5.27-10.38, P < .001) with a precision of 6.83 mm Hg.

CONCLUSIONS

P_ETCO2 can be measured simply using a capnometer, and P_ETCO2 measurements can estimate P_aCO2 . However, the limits of agreement were wide. Therefore, care providers must pay attention to the characteristics and errors of these devices. These results suggest that measurement of P_ETCO2 might be useful for screening for hypercarbic respiratory failure in the clinical setting.

The Effect of Asphyxia Arrest Duration on a Pediatric End-Tidal CO2-Guided Chest Compression Delivery Model

OBJECTIVES

To determine the effect of the duration of asphyxial arrest on the survival benefit previously seen with end-tidal CO2-guided chest compression delivery.

DESIGN

Preclinical randomized controlled study.

SETTING

University animal research laboratory.

SUBJECTS

Two-week-old swine.

INTERVENTIONS

After either 17 or 23 minutes of asphyxial arrest, animals were randomized to standard cardiopulmonary resuscitation or end-tidal CO2-guided chest compression delivery. Standard cardiopulmonary resuscitation was optimized by marker, monitor, and verbal feedback about compression rate, depth, and release. End-tidal CO2-guided delivery used adjustments to chest compression rate and depth to maximize end-tidal CO2 level without other feedback. Cardiopulmonary resuscitation for both groups proceeded from 10 minutes of basic life support to 10 minutes of advanced life support or return of spontaneous circulation.

MEASUREMENTS AND MAIN RESULTS

After 17 minutes of asphyxial arrest, mean end-tidal CO2 during 10 minutes of cardiopulmonary resuscitation was 18 ± 9 torr in the standard group and 33 ± 15 torr in the end-tidal CO2 group (p = 0.004). The rate of return of spontaneous circulation was three of 14 (21%) in the standard group rate and nine of 14 (64%) in the end-tidal CO2 group (p = 0.05). After a 23-minute asphyxial arrest, neither end-tidal CO2 values (20 vs 26) nor return of spontaneous circulation rate (3/14 vs 1/14) differed between the standard and end-tidal CO2-guided groups.

CONCLUSIONS

Our previously observed survival benefit of end-tidal CO2-guided chest compression delivery after 20 minutes of asphyxial arrest was confirmed after 17 minutes of asphyxial arrest. The poor survival after 23 minutes of asphyxia shows that the benefit of end-tidal CO2-guided chest compression delivery is limited by severe asphyxia duration.

Association of End-Tidal Carbon Dioxide Monitoring With Nurses' Confidence in Patient Readiness for Postanesthesia Discharge

PURPOSE

To determine if end-tidal carbon dioxide (etCO₂) value increased nurses' perceptions of confidence in patients' readiness for postanesthesia care unit (PACU) discharge.

DESIGN

Prospective, cross-sectional, comparative, one-group (pre-post) design.

METHODS

Nurses completed 2 assessments of confidence in readiness for discharge, before and after etCO₂ monitoring. Patient (discharge pain level, body mass index, sleep apnea history, and opioid use) and nurse factors were assessed. Analyses included descriptive and comparative statistics.

FINDINGS

Of 133 patients, mean (standard deviation) etCO₂ was 36.1 (5.7) mm Hg. Nurses' confidence in readiness for discharge differed before and after etCO₂ assessment. Confidence score decreased when etCO₂ was low (P = .003) or high (P = .005), compared with normal values. In linear regression, etCO₂ remained a factor in nurses' confidence in readiness for discharge (P < .001).

CONCLUSIONS

In a PACU, etCO₂ monitoring changed nurses' perceptions of confidence in patients' readiness for discharge.

Change in capnogram waveform is associated with bronchodilator response and asthma control in children

BACKGROUND

Airway hyper-reactivity, inflammation and remodeling contribute to inhomogeneity of ventilation-perfusion ratio VA·/Q· in asthma. Short-term variations in V.A/Q· can cause changes in expired capnographic indices.

OBJECTIVES

To measure acute changes in the phase 3 slope of the volumetric capnogram after β2-agonist inhalation (ΔSIII), for comparison with airway response based on FEV1 (ΔFEV1), and asthma control.

SUBJECTS AND METHODS

After ethical approval and informed consent, 72 children aged 6-18 y, followed up for asthma underwent spirometry and capnography before and after β-agonist inhalation through a spacer, using a side-stream rapid infrared analyzer. Asthma control was assessed using the GINA questionnaire.

RESULTS

Children with positive reversibility tests (defined as ΔFEV1>12%) had a significantly higher ΔSIII (m ± SE: 87.4 ± 41.4) versus those with negative tests (31.3 ± 14.0%, P = 0.001). Uncontrolled asthma was associated with a significantly larger ΔSIII (103.4 ± 64.0%, n = 7) compared to partly controlled (52.0 ± 26.1, n = 24; P = 0.009) and controlled asthma (30.8 ± 16.3, n = 41; P = 0.003). Neither Bohr dead space nor ΔFEV1 were different between asthma control groups.

CONCLUSIONS

ΔSIII was significantly larger in children with positive response to β2-agonist, and in uncontrolled asthmatics. To our knowledge these are the first data on exhaled CO₂ phase III volumetric slope change and asthma control. The observed ΔSIII could be due to an increased ventilation of inhomogeneous peripheral lung units, and merits further evaluation as a potential phenotypic biomarker in asthma.

The utility of the pretracheal stethoscope in detecting ventilatory abnormalities during propofol sedation in children

BACKGROUND

Monitoring of ventilation with capnography or a stethoscope is recommended because the detection of ventilatory abnormalities can be significantly delayed by the use of pulse oximetry alone in patients receiving supplemental oxygen. The aim of this study was to evaluate the diagnostic performance of the pretracheal stethoscope with pulse oximetry and capnography in detecting adverse respiratory events during propofol sedation in nonintubated children. We hypothesized that use of the pretracheal stethoscope would facilitate earlier detection of adverse respiratory events.

METHODS

This was a prospective observational study of children undergoing procedural sedation at a pediatric sedation program. A pretracheal stethoscope, pulse oximetry, and nasal capnography were attached at the discretion of the sedation nurse and provider to monitor ventilation.

RESULTS

We enrolled 104 patient encounters (mean recorded time, SD 8.3 ± 5.3 minutes) from February, 2015 to March, 2017. The pretracheal stethoscope was the first monitor to detect adverse events in 64% (25/39) of patients compared to 18% (7/39) for capnography and 15% (6/39) for pulse oximetry. Auscultation performed best at detecting upper airway obstruction but capnography and pulse oximetry performed best at detecting hypoventilation. The positive predictive value for detecting a true ventilation abnormality and 95% CI of the pretracheal stethoscope, pulse oximetry, and capnography was 100% (90%-100%), 18% (10%-31%), and 27% (18%-38%), respectively. The negative predictive value and 95% CI of the pretracheal stethoscope, pulse oximetry, and capnography was 88% (82%-92%), 68% (59%-75%), and 70% (61%-78%), respectively. Limitations are short observation time, nonstandardized application of respiratory monitors, and too much focus on auscultation.

CONCLUSION

A pretracheal stethoscope in conjunction with capnography and pulse oximetry detects most sedation-related adverse events first. Auscultation performed best at detecting upper airway obstruction but capnography and pulse oximetry performed best at detecting hypoventilation.

Sedation Strategies for Procedures Outside the Operating Room

With the rapid development of diagnostic and therapeutic procedures performed outside the operating room (OR), the need for appropriate sedation care has emerged in importance to ensure the safety and comfort of patients and clinicians. The preparation and administration of sedatives and sedation care outside the OR require careful attention, proper monitoring systems, and clinically useful sedation guidelines. This literature review addresses proper monitoring and selection of sedatives for diagnostic and interventional procedures outside the OR. As the depth of sedation increases, respiratory depression and cardiovascular suppression become serious, necessitating careful surveillance using appropriate monitoring equipment.

Capnography Monitoring During Procedural Sedation and Analgesia

Procedural sedation is used to alleviate pain and anxiety associated with diagnostic procedures in the acute care setting. Although commonly used, procedural sedation is not without risk. Key to reducing this risk is early identification of risk factors through presedation screening and monitoring during the procedure. Electrocardiogram, respiratory rate, blood pressure, and pulse oximetry commonly are monitored. These parameters do not reliably identify airway and ventilation compromise. Capnography measures exhaled carbon dioxide and provides early identification of airway obstruction and hypoventilation. Capnography is useful in patients receiving supplemental oxygen. In these patients, oxygen desaturation reported by pulse oximetry may lag during episodes of respiratory depression and apnea. Capnography indicates partial pressure of end-tidal carbon dioxide and provides information regarding airway integrity and patterns of ventilation compromise. Implementation of this technology may provide an additional layer of safety, reducing risk of respiratory compromise in patients receiving procedural sedation.

Identifying Patients Experiencing Opioid-Induced Respiratory Depression During Recovery From Anesthesia: The Application of Electronic Monitoring Devices

BACKGROUND

Postsurgical patients experiencing opioid-related adverse drug events have 55% longer hospital stays, 47% higher costs associated with their care, 36% increased risk of 30-day readmission, and 3.4 times higher risk of inpatient mortality compared to those with no opioid-related adverse drug events. Most of the adverse events are preventable.

GENERAL AIM

This study explored three types of electronic monitoring devices (pulse oximetry, capnography, and minute ventilation [MV]) to determine which were more effective at identifying the patient experiencing respiratory compromise and, further, to determine whether algorithms could be developed from the electronic monitoring data to aid in earlier detection of respiratory depression.

MATERIALS AND METHODS

A study was performed in the postanesthesia care unit (PACU) in an inner city. Sixty patients were recruited in the preoperative admissions department on the day of their surgery. Forty-eight of the 60 patients wore three types of electronic monitoring devices while they were recovering from back, neck, hip, or knee surgery. Machine learning models were used for the analysis.

RESULTS

Twenty-four of the 48 patients exhibited sustained signs of opioid-induced respiratory depression (OIRD). Although the SpO₂ values did not change, end-tidal CO₂ levels increased, and MV decreased, representing hypoventilation. A machine learning model was able to predict an OIRD event 10 min before the actual event occurred with 80% accuracy.

LINKING EVIDENCE TO ACTION

Electronic monitoring devices are currently used as a tool to assess respiratory status using thresholds to distinguish when respiratory depression has occurred. This study introduces a potential paradigm shift from a reactive approach to a proactive approach that would identify a patient at high risk for OIRD. Capnography and MV were found to be effective tools in detecting respiratory compromise in the PACU.

Systematic Review of Capnography with Mask Ventilation during Cardiopulmonary Resuscitation Maneuvers

The latest guidelines identify capnography as an instrument used to assess bag-valve-mask ventilation during cardiopulmonary resuscitation (CPR). In this review, we analyzed the feasibility and reliability of capnography use with face mask ventilation during CPR maneuvers in adults and children. This systematic review was completed in December 2018; data for the study were obtained from the following databases: EBSCOhost, SCOPUS, PubMed, Índice Bibliográfico Español en Ciencias de la Salud (IBECS), TESEO, and Cochrane Library Plus. Two reviewers independently assessed the eligibility of the articles; we analyzed publications from different sources and identified studies that focused on the use of capnography with a face mask during CPR maneuvers in order to describe the capnometry value and its correlation with resuscitation outcomes and the assistance of professionals. A total of 888 papers were collected, and 17 papers were included that provided objective values for the use of capnography with a mask for ventilation. Four were randomized clinical trials (RCT) and the rest were observational studies. Four studies were completed in adults and 13 were completed in newborns. After the analysis of the papers, we recommended a capnographic level of C in adults and B in newborns. Despite the little evidence obtained, capnography has been demonstrated to facilitate the advanced clinical practice of mask ventilation in cardiopulmonary resuscitation, to be reliable in the early detection of heart rate increase in newborns, and to asses in-airway patency and lung aeration during newborn resuscitation.