Spirometry and volumetric capnography in lung function assessment of obese and normal-weight individuals without asthma

OBJECTIVE

To analyze and compare lung function of obese and healthy, normal-weight children and adolescents, without asthma, through spirometry and volumetric capnography.

METHODS

Cross-sectional study including 77 subjects (38 obese) aged 5-17 years. All subjects underwent spirometry and volumetric capnography. The evaluations were repeated in obese subjects after the use of a bronchodilator.

RESULTS

At the spirometry assessment, obese individuals, when compared with the control group, showed lower values of forced expiratory volume in the first second by forced vital capacity (FEV₁/FVC) and expiratory flows at 75% and between 25 and 75% of the FVC (p<0.05). Volumetric capnography showed that obese individuals had a higher volume of produced carbon dioxide and alveolar tidal volume (p<0.05). Additionally, the associations between dead space volume and tidal volume, as well as phase-3 slope normalized by tidal volume, were lower in healthy subjects (p<0.05). These data suggest that obesity does not alter ventilation homogeneity, but flow homogeneity. After subdividing the groups by age, a greater difference in lung function was observed in obese and healthy individuals aged >11 years (p<0.05).

CONCLUSION

Even without the diagnosis of asthma by clinical criteria and without response to bronchodilator use, obese individuals showed lower FEV₁/FVC values and forced expiratory flow, indicating the presence of an obstructive process. Volumetric capnography showed that obese individuals had higher alveolar tidal volume, with no alterations in ventilation homogeneity, suggesting flow alterations, without affecting lung volumes.

Patient safety during procedural sedation using capnography monitoring: a systematic review and meta-analysis

OBJECTIVE

To evaluate the effect of capnography monitoring on sedation-related adverse events during procedural sedation and analgesia (PSA) administered for ambulatory surgery relative to visual assessment and pulse oximetry alone.

DESIGN AND SETTING

Systematic literature review and random effects meta-analysis of randomised controlled trials (RCTs) reporting sedation-related adverse event incidence when adding capnography to visual assessment and pulse oximetry in patients undergoing PSA during ambulatory surgery in the hospital setting. Searches for eligible studies published between 1 January 1995 and 31 December 2016 (inclusive) were conducted in PubMed, the Cochrane Library and EMBASE without any language constraints. Searches were conducted in January 2017, screening and data extraction were conducted by two independent reviewers, and study quality was assessed using a modified Jadad scale.

INTERVENTIONS

Capnography monitoring relative to visual assessment and pulse oximetry alone.

PRIMARY AND SECONDARY OUTCOME MEASURES

Predefined endpoints of interest were desaturation/hypoxaemia (the primary endpoint), apnoea, aspiration, bradycardia, hypotension, premature procedure termination, respiratory failure, use of assisted/bag-mask ventilation and death during PSA.

RESULTS

The literature search identified 1006 unique articles, of which 13 were ultimately included in the meta-analysis. Addition of capnography to visual assessment and pulse oximetry was associated with a significant reduction in mild (risk ratio (RR) 0.77, 95% CI 0.67 to 0.89) and severe (RR 0.59, 95% CI 0.43 to 0.81) desaturation, as well as in the use of assisted ventilation (OR 0.47, 95% CI 0.23 to 0.95). No significant differences in other endpoints were identified.

CONCLUSIONS

Meta-analysis of 13 RCTs published between 2006 and 2016 showed a reduction in respiratory compromise (from respiratory insufficiency to failure) during PSA with the inclusion of capnography monitoring. In particular, use of capnography was associated with less mild and severe oxygen desaturation, which may have helped to avoid the need for assisted ventilation.

Continuous Capnography in Pediatric Intensive Care

Capnography or end-tidal carbon dioxide (Etco₂) monitoring has a variety of uses in the pediatric intensive care setting. The ability to continuously measure exhaled carbon dioxide can provide vital information about airway, breathing, and circulation in critically ill pediatric patients. Capnography has diagnosis-specific applications for pediatric patients with congenital heart disease, reactive airway disease, neurologic emergencies, and metabolic derangement. This modality allows for noninvasive monitoring and has become the standard of care. This article reviews the basic principles and clinical applications of Etco₂ monitoring in the pediatric intensive care unit.

Journal of Clinical Monitoring and Computing 2016 end of year summary: respiration

This paper reviews 16 papers or commentaries published in Journal of Clinical Monitoring and Computing in 2016, within the field of respiration. Papers were published covering peri- and post-operative monitoring of respiratory rate, perioperative monitoring of CO₂, modeling of oxygen gas exchange, and techniques for respiratory monitoring.

Should capnography be used as a guide for choosing a ventilation strategy in circulatory shock caused by severe hypothermia? Observational case-series study

Background

Severe accidental hypothermia can cause circulatory disturbances ranging from cardiac arrhythmias through circulatory shock to cardiac arrest. Severity of shock, pulmonary hypoperfusion and ventilation-perfusion mismatch are reflected by a discrepancy between measurements of CO₂ levels in end-tidal air (EtCO₂) and partial CO₂ pressure in arterial blood (PaCO₂). This disparity can pose a problem in the choice of an optimal ventilation strategy for accidental hypothermia victims, particularly in the prehospital period. We hypothesized that in severely hypothermic patients capnometry should not be used as a reliable guide to choose optimal ventilatory parameters.

Methods

We undertook a pilot, observational case-series study, in which we included all consecutive patients admitted to the Severe Hypothermia Treatment Centre in Cracow, Poland for VA-ECMO in stage III hypothermia and with signs of circulatory shock. We performed serial measurements of arterial blood gases and EtCO₂, core temperature, and calculated a PaCO₂/EtCO₂ quotient.

Results

The study population consisted of 13 consecutive patients (ten males, three females, median 60 years old). The core temperature measured in esophagus was 20.7–29.0 °C, median 25.7 °C. In extreme cases we have observed a Pa-EtCO₂ gradient of 35–36 mmHg. Median PaCO₂/EtCO₂ quotient was 2.15.

Discussion and Conclusion

Severe hypothermia seems to present an example of extremely large Pa-EtCO₂ gradient. EtCO₂ monitoring does not seem to be a reliable guide to ventilation parameters in severe hypothermia.

[Airway management in intensive care units in Rhineland-Palatinate : Evolution over five years]

BACKGROUND

Securing the airway in severely ill patients is associated with a high rate of complications. So far, no information exists about the equipment readily available for airway management in German intensive care units (ICUs). It is also unknown if the range of material has improved over time.

OBJECTIVES

In the present trial the availability of equipment for airway management in ICUs in Rhineland-Palatinate was evaluated at two different times.

MATERIALS AND METHODS

Using a structured questionnaire, all ICUs in the state were contacted in the years 2010 and 2015. The availability of different types of equipment for airway management, as well as the presence of a training program for airway management, was evaluated.

RESULTS

For 2010 data from 64 ICUs were evaluated and for 2015 data sets from 63 ICUs were collected. In 2010 indirect laryngoscopes were available in eight ICUs; in 2015 these devices were directly accessible in 43 units (p < 0.0001). Extraglottic devices were available in all but one ICU in 2010 and all ICUs in 2015. Equipment for emergency surgical airway procedures was available in nearly every ICU (n = 60). The availability of capnography increased significantly from 2010 (n = 12) to 2015 (n = 56; p < 0.0001). In 2010 and 2015, frequent training with a focus on airway management was performed in 23 and 32 units, respectively (p > 0.05).

CONCLUSION

Most ICUs in Rhineland-Palatinate have a broad range of equipment for airway management available, and the range has significantly improved over the time period evaluated. The availability of indirect laryngoscopes and capnometers improved significantly. However, it is remarkable that in some ICU's there is still a lack of equipment for advanced airway management.

Effect of Neck Collar Fixation on Ventilation in Multiple Trauma Patients

BACKGROUND

According to the guidelines for treatment of multiple trauma patients, immobilization of the neck and neck collar fixation are essential. However, following neck collar fixation patients usually experience dyspnea. Some studies have found that neck collar fixation can lead to decreased pulmonary volumes, yet there have been no studies on the effect of neck collar fixation on patient ventilation.

OBJECTIVES

The purpose of this study was to determine the effect of neck collar fixation on ventilation in multiple trauma patients.

METHODS

This study was a descriptive-analytical study, which was performed in the emergency department of Tabriz University of Medical Sciences on multiple trauma patients with a Glasgow Coma Score (GCS) of 15. The effect of neck collar fixation on ventilation in the study participants was examined with the use of capnography.

RESULTS

This study involved 163 multiple trauma patients. Of these, 65% were male. The mean of end tidal carbon dioxide (ETCO₂) of the patients without neck collars was 34.62 ± 4.46 and the mean ETCO₂ of the patients with neck collars was 34.21 ± 2.31. There was no significant difference between the means of ETCO₂, before and after removing the neck collar, among the studied patients (P = 0.196).

CONCLUSIONS

According to the results of our study, neck collar fixation has no effect on ventilation in multiple trauma patients.

Two case reports of unexpected tracheal agenesis in the neonate: 3 C's beyond algorithms for difficult airway management

Background

Handling neonates with postnatal respiratory failure due to congenital airway malformations implies knowledge about emergency management of unexpected difficult airway. In these stressful situations both technical and communication skills of the caretakers are essential.

Case presentation

Two cases with prenatally unknown tracheal agenesis are reported.

Conclusion

In the presented cases, airway malformation and subsequent difficulties upon endotracheal intubation were not adequately communicated between caretakers. We discuss the aspects of culture, communication, and capnography.

Endotracheal tube placement confirmation: 100% sensitivity and specificity with sustained four-phase capnographic waveforms in a cadaveric experimental model

BACKGROUND

Waveform capnography is considered the gold standard for verification of proper endotracheal tube placement, but current guidelines caution that it is unreliable in low-perfusion states such as cardiac arrest. Recent case reports found that long-deceased cadavers can produce capnographic waveforms. The purpose of this study was to determine the predictive value of waveform capnography for endotracheal tube placement verification and detection of misplacement using a cadaveric experimental model.

METHODS

We conducted a controlled experiment with two intubated cadavers. Tubes were placed within the trachea, esophagus, and hypopharynx utilizing video laryngoscopy. We recorded observations of capnographic waveforms and quantitative end-tidal carbon dioxide (ETCO₂) values during tracheal versus extratracheal (i.e., esophageal and hypopharyngeal) ventilations.

RESULTS

106 and 89 tracheal ventilations delivered to cadavers one and two, respectively (n=195) all produced characteristic alveolar waveforms (positive) with ETCO₂ values ranging 2-113mmHg. 42 esophageal ventilations (36 to cadaver one and 6 to cadaver two), and 6 hypopharyngeal ventilations (4 to cadaver one and 2 to cadaver two) all resulted in non-alveolar waveforms (negative) with ETCO₂ values of 0mmHg. Esophageal and hypopharyngeal measurements were categorized as extratracheal (n=48). A binary classification test showed no false negatives or false positives, indicating 100% sensitivity (NPV 1.0, 95%CI 0.98-1.00) and 100% specificity (PPV 1.0, 95%CI 0.93-1.00).

CONCLUSION

Though current guidelines question the reliability of waveform capnography for verifying endotracheal tube location during low-perfusion states such as cardiac arrest, our findings suggest that it is highly sensitive and specific.

Reliability of Ultrasonography in Confirming Endotracheal Tube Placement in an Emergency Setting

Background and Objectives:

Over the past few years, ultrasonography is increasingly being used to confirm the correct placement of endotracheal tube (ETT). In our study, we aimed to compare it with the traditional clinical methods and the gold standard quantitative waveform capnography. Two primary outcomes were measured in our study. First was the sensitivity and specificity of ultrasonography against the other two methods to confirm endotracheal intubation. The second primary outcome assessed was the time taken for each method to confirm tube placement in an emergency setting.

Methods:

This is a single-centered, prospective cohort study conducted in an emergency department of a tertiary care hospital. We included 100 patients with indication of emergency intubation by convenient sampling. The intubation was performed as per standard hospital protocol. As part of the study protocol, ultrasonography was used to identify ETT placement simultaneously with the intubation procedure along with quantitative waveform capnography (end-tidal carbon dioxide) and clinical methods. Confirmation of tube placement and time taken for the same were noted by three separate health-care staffs.

Results and Discussion:

Out of the 100 intubation attempts, five (5%) had esophageal intubations. The sensitivity and specificity of diagnosis using ultrasonography were 97.89% and 100%, respectively. This was statistically comparable with the other two modalities. The time taken to confirm tube placement with ultrasonography was 8.27 ± 1.54 s compared to waveform capnography and clinical methods which were 18.06 ± 2.58 and 20.72 ± 3.21 s, respectively. The time taken by ultrasonography was significantly less.

Conclusions:

Ultrasonography confirmed tube placement with comparable sensitivity and specificity to quantitative waveform capnography and clinical methods. But then, it yielded results considerably faster than the other two modalities.

End-tidal CO2 on admission is associated with hemorrhagic shock and predicts the need for massive transfusion as defined by the critical administration threshold: A pilot study

BACKGROUND

Critical administration threshold (≥3 units of packed red blood cells/h or CAT+) has been proposed as a new definition for massive transfusion (MT) that includes volume and rate of blood transfusion. CAT+ has been shown to eliminate survivor bias and be a better predictor of mortality than the traditional MT (>10 units/24h). End-tidal CO₂ (ET CO₂) negatively correlates with lactate and is an early predictor of shock in trauma patients. We conducted a pilot study to test the hypothesis that low ET CO₂ on admission predicts CAT+.

METHODS

ET CO₂ via capnography and serum lactate were prospectively collected on admission for 131 patients requiring trauma team activation. Demographic data were obtained from patient charts. Excluded were patients with isolated head injuries, traumatic arrests, or pre-hospital intubations. CAT± status was determined for each hour up to 6h from admission as described; likewise, MT± status was determined up to 24h from admission.

RESULTS

After exclusion criteria, 67 patients were analyzed. Mean age was 41.2 (SD 18.5). Thirty-three patients had a blunt mechanism of injury (49%), median ISS was 9 (interquartile range 4-19), and there were 6 deaths (9%). ET CO₂ and lactate were negatively correlated by Spearman rank-based correlation (rho=-0.41, p=0.0006). Twenty-one (31%) and 8 (12%) patients were CAT+ and traditional MT+, respectively. There were a significantly greater proportion of patients with ISS>15, ET CO₂ <35, or who died found to be CAT+. A binomial logistic regression model adjusting for age, SBP <90, HR, and ISS >15 revealed ET CO₂ < 35 to be independently predictive of CAT+ (OR 9.24, 95% CI 1.51-56.57, p=0.016).

CONCLUSIONS

This pilot study demonstrated that low ET CO₂ had strong association with standard indicators for shock and was predictive of patients meeting CAT+ criteria in the first 6h after admission. Further study to verify these results and to elucidate CAT criteria's association with mortality will require a larger sample size.

End-tidal capnography and upper airway ultrasonography in the rapid confirmation of endotracheal tube placement in patients requiring intubation for general anaesthesia

Background and Aims:

Confirmation of correct endotracheal tube placement is essential immediately after intubation for general anaesthesia. In this study, we have compared upper airway ultrasonography (USG) with reference to capnography for rapid confirmation of endotracheal tube placement after general anaesthesia.

Methods:

A prospective, single centre, observational study was conducted on 100 patients requiring tracheal intubation for general anaesthesia. Both capnography and upper airway USG were performed immediately after intubation to confirm the endotracheal tube (ETT) placement. Sensitivity, specificity, and positive and negative predictive values of upper airway USG were determined against capnography as the reference method. Agreement between the methods and time required to determine ETT placement by the two methods were assessed with kappa statistics and Student's t-test.

Results:

Upper airway USG detected all five cases of oesophageal intubation, but could not detect five patients with correct tracheal intubation. Upper airway USG had a sensitivity of 96.84% (95% confidence interval [CI]: 94.25%–96.84%), specificity of 100% (95% CI: 50.6%–100%), positive predictive value of 100% (95% CI: 97.3%–100%) and negative predictive value of 62.5% (95% CI: 31.6%–62.5%). Kappa value was found to be 0.76, indicating a good agreement between upper airway USG and capnography for confirmation of ETT placement. Time taken for confirmation of ETT by capnography was 8.989 ± 1.043 s vs. 12.0 ± 1.318 s for upper airway USG (P < 0.001).

Conclusion:

Both capnography and upper airway USG may be used as primary procedures for the confirmation of ETT placement.

Investigation of the efficacy of colorimetric capnometry method used to verify the correct placement of the nasogastric tube

OBJECTIVES

This present study was designed to determine the efficacy of the colorimetric capnometry method used to verify the correct placement of the nasogastric tube.

METHODS

The present study comprised forty patients who had a nasogastric tube inserted and were being monitored in the adult intensive care unit. After the insertion of the nasogastric tube, 40 colorimetric capnometry and 40 auscultation measurements were performed. Auscultation and colorimetric capnometry results were compared with tube placement results confirmed radiologically.

RESULTS

In the confirmation of the placement of the nasogastric tube, the consistency was 97.5% (p<0.05) between the colorimetric capnometry method and the radiological method, and 82.5% (p>0.05) between the auscultatory method and the radiological method. The oesophageal placement of the nasogastric tube was detected with the colorimetric capnometry method, but the gastric and duodenal insertions were not determined. While the sensitivity and specificity of the colorimetric capnometry method in determining the correct placement of the nasogastric tube were 1.00 and 0.667 respectively, those of the auscultatory method were 0.89 and 0.0 respectively.

CONCLUSION

As a result, for the confirmation of the NGT placement, the colorimetric capnometry method is considered more reliable than the auscultatory method and is compatible with the radiological method. However, the colorimetric capnometry method is inadequate to distinguish between the gastric or duodenal insertion.

Implementation of a novel postoperative monitoring system using automated Modified Early Warning Scores (MEWS) incorporating end-tidal capnography

Modified Early Warning Scores (MEWS) provide real-time vital sign (VS) trending and reduce ICU admissions in post-operative patients. These early warning calculations classically incorporate oxygen saturation, heart rate, respiratory rate, systolic blood pressure, and temperature but have not previously included end-tidal CO2 (EtCO₂), more recently identified as an independent predictor of critical illness. These systems may be subject to failure when physiologic data is incorrectly measured, leading to false alarms and increased workload. This study investigates whether the implementation of automated devices that utilize ongoing vital signs monitoring and MEWS calculations, inclusive of a score for end-tidal CO₂ (EtCO₂), can be feasibly implemented on the general care hospital floor and effectively identify derangements in a post-operative patient's condition while limiting the amount of false alarms that would serve to increase provider workload. From July to November 2014, post-operative patients meeting the inclusion criteria (BMI > 30 kg/m², history of obstructive sleep apnea, or the use of patient-controlled analgesia (PCA) or epidural narcotics) were monitored using automated devices that record minute-by-minute VS included in classic MEWS calculations as well as EtCO₂. Automated messages via pagers were sent to providers for instances when the device measured elevated MEWS, abnormal EtCO₂, and oxygen desaturations below 85 %. Data, including alarm and message details from the first 133 patients, were recorded and analyzed. Overall, 3.3 alarms and pages sounded per hour of monitoring. Device-only alarms sounded 2.7 times per hour-21 % were technical alarms. The remaining device-only alarms for concerning VS sounded 2.0/h, 70 % for falsely recorded VS. Pages for abnormal EtCO₂ sounded 0.4/h (82 % false recordings) while pages for low blood oxygen saturation sounded 0.1/h (55 % false alarms). 143 times (0.1 pages/h) the devices calculated a MEWS warranting a page (rise in MEWS by 2 or 5 or greater)-62 % were false scores inclusive of falsely recorded VS. An abnormal EtCO₂ value resulted in or added to an elevated MEWS score in 29 % of notifications, but 50 % of these included a falsely abnormal EtCO₂ value. To date, no adverse events have occurred. There were no statistically significant demographic, post-operative condition, or pre-existing comorbidity differences between patients who had a majority of true alarms from those who had mostly false-positive alarms. Although not statistically significant, the group of patients in whom automated MEWS suggested greater utility included those with a history of hypertension (p = 0.072) and renal disease (p = 0.084). EtCO₂ monitoring was more likely to be useful in patients with a history of type 2 diabetes, coronary artery disease, and obstructive sleep apnea (p < 0.05). These patients were also more likely to have been on a PCA post-operatively (p < 0.05). Overall, non-invasive physiologic monitoring incorporating an automated MEWS system, modified to include end-tidal CO2 can be feasibly implemented in a hospital ward. Further study is needed to evaluate its clinical utility, including an end-tidal CO₂ score, is feasibly implemented and can be useful in monitoring select post-operative patients for derangements in physiologic metrics. Like any other monitoring system, false alarms may occur at high rates. While further study is needed to determine the additive utility of EtCO₂ in MEWS calculations, this study suggests utility of EtCO₂ in select post-operative patients.

Comparison of end-tidal carbon dioxide and arterial blood bicarbonate levels in patients with metabolic acidosis referred to emergency medicine

Introduction: The routine and gold standard method to diagnose of acid - base disturbance is arterial blood gas (ABG) sampling. Capnography could be used to measure the end-tidal carbon dioxide (ETCO2) levels and ETco2 has a close correlation with the PaCo2. The aim of this study was comparison the ETco2 and arterial blood bicarbonate levels in patients with metabolic acidosis. Methods: In a descriptive-analytical study that performed in Emergency Department of Emam Reza Medical Research and Training Hospital of Tabriz on patients with metabolic acidosis, ETco2 level and blood bicarbonate levels in 262 patients were evaluated. Results: Mean of ETco2 and Hco3 levels in patients with metabolic acidosis were 22.29 ± 4.15 and 12.78 ± 3.83, respectively. In all patients, the significant direct linear relationship was found between ETco2 with Hco3 (r = 0.553, P < 0.001). We had 4 groups of patients with metabolic acidosis, also there is a significant direct linear relationship between the ETCo2 and the Hco3 level of arterial blood in patients with renal failure (P < 0.001 and r = 0.551), sepsis (P < 0.001 and r = 0.431), drug toxicity (P < 0.001 and r = 0.856), and ketoacidosis (DKA) (P < 0.001 and r = 0.559). Conclusion: According to the results of this study, capnography can be used for primary diagnosis of metabolic acidosis in spontaneously breathing patients who referred to the emergency wards, however, the ABG must be considered as the gold standard tool for diagnosis and guiding the treatment.

Current methodological and technical limitations of time and volumetric capnography in newborns

Although capnography is a standard tool in mechanically ventilated adult and pediatric patients, it has physiological and technical limitations in neonates. Gas exchange differs between small and adult lungs due to the greater impact of small airways on gas exchange, the higher impact of the apparatus dead space on measurements due to lower tidal volume and the occurrence of air leaks in intubated patients. The high respiratory rate and low tidal volume in newborns, especially those with stiff lungs, require main-stream sensors with fast response times and minimal dead-space or low suction flow when using side-stream measurements. If these technical requirements are not fulfilled, the measured end-tidal CO2 (P et CO 2 ), which should reflect the alveolar CO2 and the calculated airway dead spaces, can be misleading. The aim of this survey is to highlight the current limitations of capnography in very young patients to avoid pitfalls associated with the interpretation of capnographic parameters, and to describe further developments.

Extended Monitoring during Endoscopy

Gastrointestinal endoscopic sedation has improved procedural and patient outcomes but is associated with attendant risks of oversedation and hemodynamic compromise. Therefore, close monitoring during endoscopic procedures using sedation is critical. This monitoring begins with appropriate staff trained in visual assessment of patients and analysis of basic physiologic parameters. It also mandates an array of devices widely used in practice to evaluate hemodynamics, oxygenation, ventilation, and depth of sedation. The authors review the evidence behind monitoring practices and current society recommendations and discuss forthcoming technologies and techniques that are poised to improve noninvasive monitoring of patients under endoscopic sedation.

Typical patterns of expiratory flow and carbon dioxide in mechanically ventilated patients with spontaneous breathing

Incomplete expiration of tidal volume can lead to dynamic hyperinflation and auto-PEEP. Methods are available for assessing these, but are not appropriate for patients with respiratory muscle activity, as occurs in pressure support. Information may exist in expiratory flow and carbon dioxide measurements, which, when taken together, may help characterize dynamic hyperinflation. This paper postulates such patterns and investigates whether these can be seen systematically in data. Two variables are proposed summarizing the number of incomplete expirations quantified as a lack of return to zero flow in expiration (IncExp), and the end tidal CO₂ variability (varETCO₂), over 20 breaths. Using these variables, three patterns of ventilation are postulated: (a) few incomplete expirations (IncExp < 2) and small varETCO₂; (b) a variable number of incomplete expirations (2 ≤ IncExp ≤ 18) and large varETCO₂; and (c) a large number of incomplete expirations (IncExp > 18) and small varETCO₂. IncExp and varETCO₂ were calculated from data describing respiratory flow and CO₂ signals in 11 patients mechanically ventilated at 5 levels of pressure support. Data analysis showed that the three patterns presented systematically in the data, with periods of IncExp < 2 or IncExp > 18 having significantly lower variability in end-tidal CO₂ than periods with 2 ≤ IncExp ≤ 18 (p < 0.05). It was also shown that sudden change in IncExp from either IncExp < 2 or IncExp > 18 to 2 ≤ IncExp ≤ 18 results in significant, rapid, change in the variability of end-tidal CO₂ p < 0.05. This study illustrates that systematic patterns of expiratory flow and end-tidal CO₂ are present in patients in supported mechanical ventilation, and that changes between these patterns can be identified. Further studies are required to see if these patterns characterize dynamic hyperinflation. If so, then their combination may provide a useful addition to understanding the patient at the bedside.

Hypocapnia and hyperoxia induction using a hyperventilation protocol in electroconvulsive therapy

INTRODUCTION

Hyperventilation in electroconvulsive therapy sessions has been associated with seizure threshold, seizure characteristics, and cognitive effects. There is no consensus on the optimal procedure of applying hyperventilation manoeuvres during electroconvulsive therapy.

MATERIAL AND METHODS

Prospective evaluation of the effects of systematic use of hyperventilation manoeuvres with facial mask and capnography (protocolized hyperventilation [pHV]), on ventilation parameters and on seizures. The study included a sample of 130 sessions (65 performed according to hyperventilation standard practice and 65 successive sessions, with pHV) of 35 patients over a period of 10 weeks.

RESULTS

The pHV manoeuvres reduced exhaled CO₂ and increased O₂ saturation significantly (P<.001). The average CO₂ reduction achieved was 6.52±4.75mmHg (95% CI -7.7 to -5.3). The CO₂ values after pHV correlated significantly with seizure duration and O₂ values, with other electroencephalographic quality indices. In pHV sessions, compared with sessions performed according to hyperventilation standard practice, the average lengthening of the motor and electroencephalographic seizure was 3.86±14.62 and 4.73±13.95s, respectively. No differences were identified in other ictal quality parameters.

CONCLUSIONS

The proposed pHV manoeuvres significantly modify ventilation parameters. The hypocapnia and hyperoxia obtained by applying these manoeuvres lengthen the duration of seizures without worsening the quality of the electroencephalographic trace. The use of pHV is generalisable and might improve electroconvulsive therapy procedure without adding costs.

Comparison of ventilator-integrated end-tidal CO2 and transcutaneous CO2 monitoring in home-ventilated neuromuscular patients

BACKGROUND

Non-invasive transcutaneous capnometry (TcCO2) is used to assess the home ventilation's efficiency. Recently, end-tidal CO2 (ETCO2) sensors have been integrated in life-support home ventilators. The purpose of this study was to compare the ventilator-integrated ETCO2 with TcCO2, in home-ventilated neuromuscular disease patients.

METHODS

ETCO2 and TcCO2 were simultaneously measured during one night in 28 patients. Daytime blood gases were drawn on the following morning to measure arterial PCO2 (PaCO2).

RESULTS

Compared to PaCO2 values, both ETCO2 and TcCO2 showed a small bias (-0.1 mmHg and 0.6 mmHg, respectively) and a similar critical difference (6.8 mmHg and 7.3 mmHg, respectively). We found a good correlation between ETCO2 and TcCO2, both considering the mean nocturnal PCO2 (r = 0.897, p < 0.001; bias -1.1 [- 9.0; 6.9] mmHg) and the maximal PCO2 value over the night (r = 0.905, p < 0.001; bias 3.1 [-4.5; 10.8] mmHg). The concordance of the two techniques in detecting overnight PCO2 fluctuations was high, with r = 0.919 (p < 0.001) for the time spent with PCO2 >45 mmHg and r = 0.943 (p < 0.001) for the time with PCO2 >50 mmHg.

CONCLUSIONS

The ventilator-integrated end-tidal CO2 monitoring is as reliable as the currently used transcutaneous measurement, resulting to be a valuable proxy of the overnight PCO2 evolution. This result opens the possibility of a simplification in the monitoring of home ventilated patients, since ETCO2 measurement can be performed directly at home, with a low additional cost. However, the accuracy of both these measurement techniques is not sufficient to replace blood gases, which remain the reference examination. ClinicalTrials.gov registration:NCT02068911.

Abrupt rise of end tidal carbon dioxide level was a specific but non-sensitive marker of return of spontaneous circulation in patient with out-of-hospital cardiac arrest

OBJECTIVE

To evaluate the diagnostic accuracy of an abrupt and sustained increase in end-tidal carbon dioxide (ETCO2) to indicate return of spontaneous circulation (ROSC) during resuscitation of patient with out-of-hospital cardiac arrest.

DESIGN

Cross-sectional study.

SETTING

Emergency department of two regional hospitals.

METHODS

Patients with age ≥18 years old, suffered non-traumatic out-of-hospital cardiac arrest with active resuscitation and endotracheal intubation performed in emergency department, were included. ETCO2 value was charted throughout resuscitation. Time of ROSC was remarked. ETCO2 levels before and after ROSC were compared. Diagnostic accuracy of ETCO2 rise ≥10mmHg, ETCO2 rise ≥20mmHg, and ETCO2 rise to the level ≥40mmHg were evaluated for indicating ROSC.

RESULTS

ETCO2 level immediately after ROSC was higher as compared to the value before return of circulation (median ETCO2 was 32mmHg and 41mmHg respectively, p=0.033). With ETCO2 rise ≥10mmHg, the sensitivity was low (33%, 95% CI 22-47%), while specificity was 97% (95% CI 91-99%). Positive and negative predictive values were 83% (95% CI 62-95%) and 74% (95% CI 66-81%) respectively. The diagnostic accuracy was higher in cardiac arrest with presumed non-cardiac etiology (sensitivity 45%, specificity 100%) as compared to those with cardiac etiology (sensitivity 18%, specificity 97%).

CONCLUSIONS

The feature of an abrupt rise of ETCO2 was a specific but non-sensitive marker of ROSC in patient with out-of-hospital cardiac arrest.

Diagnostic accuracy of capnography during high-frequency ventilation in neonatal intensive care units

BACKGROUND AND OBJECTIVE

High-frequency ventilation (HFV) is a powerful tool for CO2 elimination, and thus requires careful monitoring of CO2 . Our aim was to assess the diagnostic accuracy (correlation, agreement, and trending) of continuous distal capnography (dCap) with PaCO2 in infants ventilated with HFV.

DESIGN

This was a prospective, observational, multicenter study. dCap was compared with simultaneous PaCO2 ("gold standard") drawn from indwelling arterial line for patient care in term and preterm infants ventilated with HFV. dCap was obtained via the side-port of a double-lumen endotracheal-tube by a Microstream capnograph with specially designed software for HFV.

RESULTS

Twenty-four infants participated in the study (median [range] gestational age [GA]: 26.8 [23.6-38.6] weeks). Analysis included 332 measurements. dCap was in correlation (r = 0.70, P < 0.001) but with less than adequate agreement (mean difference ± SD of the differences: -11.7 ± 10.3 mmHg) with PaCO2 . Comparable findings were found in the subgroup of infants <1,000 g (n = 240 measurements). Correlations were maintained in severe lung disease. Changes in dCap and in PaCO2 for consecutive measurements within each patient were correlated (r = 0.63, P < 0.001). Area under the receiver operating curves (ROC) for dCap to detect high (>60 mmHg) or low (<30 mmHg) PaCO2 was 0.83 (CI: 0.76-0.90) and 0.88 (CI: 0.79-0.97), respectively; P < 0.001.

CONCLUSIONS

Our prospective study suggests that continuous dCap in infants ventilated with HFV may be helpful for trends and alarm for unsafe levels of PaCO2 . dCap is only a complimentary tool and cannot replace PaCO2 sampling because the agreement between these measurements was less than adequate.

End-tidal capnometry during emergency department procedural sedation and analgesia: a randomized, controlled study

BACKGROUND

This prospective, randomized trial was undertaken to evaluate the utility of adding end-tidal capnometry (ETC) to pulse oximetry (PO) in patients undergoing procedural sedation and analgesia (PSA) in the emergency department (ED).

METHODS

The patients were randomized to monitoring with or without ETC in addition to the current standard of care. Primary endpoints included respiratory adverse events, with secondary endpoints of level of sedation, hypotension, other PSA-related adverse events and patient satisfaction.

RESULTS

Of 986 patients, 501 were randomized to usual care and 485 to additional ETC monitoring. In this series, 48% of the patients were female, with a mean age of 46 years. Orthopedic manipulations (71%), cardioversion (12%) and abscess incision and drainage (12%) were the most common procedures, and propofol and fentanyl were the sedative/analgesic combination used for most patients. There was no difference in patients experiencing de-saturation (SaO2<90%) between the two groups; however, patients in the ETC group were more likely to require airway repositioning (12.9% vs. 9.3%, P=0.003). Hypotension (SBP<100 mmHg or <85 mmHg if baseline <100 mmHg) was observed in 16 (3.3%) patients in the ETC group and 7 (1.4%) in the control group (P=0.048).

CONCLUSIONS

The addition of ETC does not appear to change any clinically significant outcomes. We found an increased incidence of the use of airway repositioning maneuvers and hypotension in cases where ETC was used. We do not believe that ETC should be recommended as a standard of care for the monitoring of patients undergoing PSA.

Smart respiratory monitoring: clinical development and validation of the IPI™ (Integrated Pulmonary Index) algorithm

Continuous electronic monitoring of patient respiratory status frequently includes PetCO₂ (end tidal CO₂), RR (respiration rate), SpO₂ (arterial oxygen saturation), and PR (pulse rate). Interpreting and integrating these vital signs as numbers or waveforms is routinely done by anesthesiologists and intensivists but is challenging for clinicians in low acuity areas such as medical wards, where continuous electronic respiratory monitoring is becoming more common place. We describe a heuristic algorithm that simplifies the interpretation of these four parameters in assessing a patient’s respiratory status, the Integrated Pulmonary Index (IPI). The IPI algorithm is a mathematical model combining SpO₂, RR, PR, and PetCO₂ into a single value between 1 and 10 that summarizes the adequacy of ventilation and oxygenation at that point in time. The algorithm was designed using a fuzzy logic inference model to incorporate expert clinical opinions. The algorithm was verified by comparison to experts’ scoring of clinical scenarios. The validity of the index was tested in a retrospective analysis of continuous SpO₂, RR, PR, and PetCO₂ readings obtained from 523 patients in a variety of clinical settings. IPI correlated well with expert interpretation of the continuous respiratory data (R = 0.83, p <<< 0.001), with agreement of −0.5 ± 1.4. Receiver operating curves analysis resulted in high levels of sensitivity (ranging from 0.83 to 1.00), and corresponding specificity (ranging from 0.96 to 0.74), based on IPI thresholds 3−6. The IPI reliably interpreted the respiratory status of patients in multiple areas of care using off-line continuous respiratory data. Further prospective studies are required to evaluate IPI in real time in clinical settings.

Effect of End-Tidal Carbon Dioxide Measurement on Resuscitation Efficiency and Termination of Resuscitation

Objectives

In this study, the value of end-tidal carbon dioxide (ETCO₂) levels measured by capnometry were evaluated as indicators of resuscitation effectiveness and survival in patients presenting to the emergency department with cardiopulmonary arrest.

Methods

ETCO₂ was measured after 2 minutes of compression or 150 compressions. ETCO₂ values were measured in patients that were intubated and in those who underwent chest compression. The following parameters were recorded for each patient: demographic data, chronic illness, respiration type, pre-hospital CPR, arrest rhythm, arterial blood gas measurements, ETCO₂ values with an interval of 5 minutes between the measurement and the estimated time of arrest, time to return to spontaneous circulation.

Results

Cardiac arrest developed in 97 cases, including 56 who were out of the hospital and 41 who were in the hospital. Fifty of these patients returned to spontaneous circulation, and just one of these had an initial ETCO₂ value below 10 mmHg. The mean of the final ETCO₂ levels was 36.4±4.46 among Patients who Return to Spontaneous Circulation (RSCPs) and 11.74±7.01 among those that died. In all rhythms; Asystole, pulseless electrical activity (PEA) and VF/VT; Overall, RSCPs had higher ETCO₂ levels than the cases who died. Among the PEA patients undergoing in-hospital arrests and those asystolic patients undergoing out of hospital arrest, the ETCO₂ values of the RSCPs were significantly higher than those of the cases who died.

Conclusions

ETCO₂ levels predicted survival as well as the effectiveness of CPR for patients who received CPR and were monitored by capnometry in the emergency department. As a result, we believe that it would be suitable to use capnometry in all units where the CPR is performed.