Increase In ETCO2 Research Articles

Buteyko Breathing Technique for Exertion-Induced Paradoxical Vocal Fold Motion (EI-PVFM)

The primary purpose of the current study was to determine the usefulness of Buteyko breathing technique (BBT) in reducing dyspnea in patients with one form of Paradoxical Vocal Fold Motion (PVFM), exertion-induced PVFM (EI-PVFM), concomitant with hyperventilation. The secondary purpose was to determine whether BBT had an effect on physiological markers of hyperventilation, as speculated by BBT theory: respiratory tidal minute volume (RTMV), end-tidal carbon dioxide (ETCO2), and resting heart rate (HR). Using a within-subjects, repeated measures group design, 12 participants with EI-PVFM and hyperventilation underwent 12 weeks of BBT, following an initial no-treatment control condition. Outcome measures of PVFM-dyspnea frequency and severity-and of hyperventilation-HR, RTMV, and ETCO2-were acquired pre- and post-treatment. Results showed post-treatment decreases in dyspnea severity, HR, and RTMV, as well as increases in ETCO2. Decreases in dyspnea and RTMV measures remained after correction for alpha inflation. Findings suggest BBT may be useful for some individuals with EI-PVFM and hyperventilation. The high prevalence of hyperventilation in EI-PVFM found in the current study warrants further investigation.

Da li su vrednosti izdahnutog CO2 i saturacije kiseonika tokom resuscitacije u korelaciji?

Aim The Aim of the research is to determine the connection between EtCO2 and pulse-oxymetry and surviving and favourable outcome of OHCA victims,as an upgrade from OHCA International Studies ' EuReCa_ONE ,in Indjija's emergency service. Methodology: The study was conducted as a prospective-observational study out-of-hospital cardiac arrest between 01.10.2015-31.12.2016., according to the methodology EuReCa_ONE study in 2015.,which followed next 15 months. Data on the SCD are administered in a questionnaire Utstein Style. In addition to the questionnaire EtCO2 and SaO2 value were monitored:the initial-EtCO2 and SaO2 , EtCO2 and SaO2 in the second minute, the final EtCO2 and SaO2 and average value of EtCO2 . Results: In the victims who did not achieve ROSC initial EtCO2 was 7.1mmHg, 12,9mmHg the average and final 11,7mmHg. Average EtCO2 after 2-minutes was 11mmHg. When the victims achieved ROSC initial EtCO2 was 14.65mmHg,average 23,1mmHg and 26.71mmHg final. Average EtCO2 after 2 minutes was 25.77mmHg. In the victims who did not achieve ROSC initial SaO2 was 14.1%,78,5% the average and final 45,3%. Average SaO2 after 2 minutes was 69%.When achieved ROSC initial SaO2 was 21,2 %, average 79,4% and 82,1% final.Average SaO2 after 2 minutes was 71,1. Conclusion: The trend of increase in EtCO2 after 2-minutes is the most important predictor of ROSC. The upward trend in EtCO2 after 2 minutes could be a good indicator of the outcome and further research is needed. Values of EtCO2 and SaO2 are not in correlation during resuscitation, also the values of SaO2 does not predict outcome but SaO2 is sign of good resuscitation.

Arterial and end-tidal Carbon Dioxide Tension Changes during Spinal Anaesthesia in Upper Abdominal Laparoscopic Surgeries: A Comparison with General Anaesthesia


 Nowadays, laparoscopic surgeries are being performed under subarachnoid block (SAB) safely.
 Aims: This study was to compare the arterial and end-tidal carbon dioxide (CO2) tension changes during spinal and general anaesthesia (GA) in CO2 pneumoperitoneum for upper abdominal laparoscopic surgeries.
 Settings and Design: This was a prospective randomized comparative clinical study.
 Materials and Methods: Eighty patients posted for upper abdominal laparoscopic surgeries were randomly allocated to two groups either to receive standard GA or lumbar SAB.
 Results: The demographic profiles of both the groups were comparable. The PaCO2 was increased gradually and sustained at its peaks within 20±4.37 minutes in both the groups. The mean±SD revealed to be higher in Group B (41.5500±2.1315) than Group A (40.8460±2.1136), but the difference between the two was not statistically significant (P=0.6142). There was a gradual increase in ETCO2 over the initial 10±2.07 minutes and reached a plateau within 20±5.74 minutes in both the groups and declined faster after deflation of pneumoperitoneum in SAB group. The mean±SD was found to be higher in Group B (33.923±1.642) than Group A (33.408±1.772), but it was also not statistically significant (P=0.4492). The difference of the arterial blood pH between the groups was not statistically significant. Three (7.5%) patients developed transient urinary retention and 2 (5%) patients suffered from post-dural puncture headache in SAB group.
 Conclusions: Arterial and end-tidal CO2 tension changes during upper abdominal laparoscopic surgery under SAB remain within physiological limit and comparable to the CO2 tensions under GA. However, per-operative complications in SAB are greater, while it is lesser in postoperative period in comparison to GA. SAB may be adopted in ASA physical status I patients with proper preoperative counselling.
 J Bangladesh Coll Phys Surg 2019; 37(1): 13-18
 

An observational study of end-tidal carbon dioxide trends in general anesthesia

PurposeDespite growing evidence supporting the potential benefits of higher end-tidal carbon dioxide (ETCO2) levels in surgical patients, there is still insufficient data to formulate guidelines for ideal intraoperative ETCO2 targets. As it is unclear which intraoperative ETCO2 levels are currently used and whether these levels have changed over time, we investigated the practice pattern using the Multicenter Perioperative Outcomes Group database.MethodsThis retrospective, observational, multicentre study included 317,445 adult patients who received general anesthesia for non-cardiothoracic procedures between January 2008 and September 2016. The primary outcome was a time-weighted average area-under-the-curve (TWA-AUC) for four ETCO2 thresholds (< 28, < 35, < 45, and > 45 mmHg). Additionally, a median ETCO2 was studied. A Kruskal-Wallis test was used to analyse differences between years. Random-effect multivariable logistic regression models were constructed to study variability.ResultsBoth TWA-AUC and median ETCO2 showed a minimal increase in ETCO2 over time, with a median [interquartile range] ETCO2 of 33 [31.0–35.0] mmHg in 2008 and 35 [33.0–38.0] mmHg in 2016 (P <0.001). A large inter-hospital and inter-provider variability in ETCO2 were observed after adjustment for patient characteristics, ventilation parameters, and intraoperative blood pressure (intraclass correlation coefficient 0.36; 95% confidence interval, 0.18 to 0.58).ConclusionsBetween 2008 and 2016, intraoperative ETCO2 values did not change in a clinically important manner. Interestingly, we found a large inter-hospital and inter-provider variability in ETCO2 throughout the study period, possibly indicating a broad range of tolerance for ETCO2, or a lack of evidence to support a specific targeted range. Clinical outcomes were not assessed in this study and they should be the focus of future research.

Carbon Dioxide Fluctuations Are Associated with Changes in Cerebral Oxygenation and Electrical Activity in Infants Born Preterm

To evaluate the effects of acute arterial carbon dioxide partial pressure changes on cerebral oxygenation and electrical activity in infants born preterm. This retrospective observational study included ventilated infants born preterm with acute fluctuations of continuous end-tidal CO2 (etCO2) as a surrogate marker for arterial carbon dioxide partial pressure, during the first 72 hours of life. Regional cerebral oxygen saturation and fractional tissue oxygen extraction were monitored with near-infrared spectroscopy. Brain activity was monitored with 2-channel electroencephalography. Spontaneous activity transients (SATs) rate (SATs/minute) and interval between SATs (in seconds) were calculated. Ten-minute periods were selected for analysis: before, during, and after etCO2 fluctuations of ≥5 mm Hg. Thirty-eight patients (mean ± SD gestational age of 29 ± 1.8 weeks) were included, with 60 episodes of etCO2 increase and 70 episodes of etCO2 decrease. During etCO2 increases, brain oxygenation increased (regional cerebral oxygen saturation increased, fractional tissue oxygen extraction decreased; P < .01) and electrical activity decreased (SATs/minute decreased, interval between SATs increased; P < .01). All measures recovered when etCO2 returned to baseline. During etCO2 decreases, brain oxygenation decreased (regional cerebral oxygen saturation decreased, fractional tissue oxygen extraction decreased; P < .01) and brain activity increased (SATs/minute increased, P < .05), also with recovery after return of etCO2 to baseline. An acute increase in etCO2 is associated with increased cerebral oxygenation and decreased brain activity, whereas an acute decrease is associated with decreased cerebral oxygenation and slightly increased brain activity. Combining continuous CO2 monitoring with near-infrared spectroscopy may enable the detection of otherwise undetected fluctuations in arterial carbon dioxide partial pressure that may be harmful to the neonatal brain.

End-Tidal CO2 Predicts Reduction in Mitral Regurgitation in Patients Undergoing Percutaneous Mitral Valve Edge-to-Edge Repair

Objectives: We evaluated end-tidal CO₂ (etCO₂), which has been proposed to assess acute hemodynamic changes, to guide percutaneous edge-to-edge mitral valve repair (PMVR) with the MitraClip system. Methods: Thirty-nine patients (aged 78 ± 14 years) undergoing PMVR for moderate-to-severe mitral regurgitation (MR) of primary and secondary etiology were included. General anesthesia was maintained with sevoflurane and constant ventilation parameters to ensure stable etCO₂ tension. MR grade was determined semiquantitatively by transesophageal echocardiography by 2 experienced operators blinded to etCO₂ measurements. etCO₂ levels were measured 3, 5, 10, and 15 min after final MitraClip placement. Results: Overall, etCO₂ increased from 32.2 ± 1.7 before to 35.4 ± 3.0, 34.6 ± 2.6, and 34.2 ± 2.4 mm Hg 3, 5, and 10 min after implantation. A significant correlation was noted between the echocardiographic reduction in MR grade and the increase in etCO₂. ANOVA for repeated measures confirmed a significant increase in etCO₂ after clip implantation (corrected F = 20.0; p < 0.001) and revealed a significantly greater increase in etCO₂ in patients with MR reduction ≥2 grades as compared to lesser MR reductions (F = 6.47; p = 0.015). Blood pressure changes did not correlate with the degree of MR reduction. Conclusions: We observed a close correlation between the reduction in MR grade during PMVR and etCO₂, which might evolve as a useful parameter to complement treatment guidance during PMVR.

SponTaneous Respiration using IntraVEnous anaesthesia and Hi-flow nasal oxygen (STRIVE Hi) maintains oxygenation and airway patency during management of the obstructed airway: an observational study

BackgroundHigh-flow nasal oxygen (HFNO) has been shown to benefit oxygenation, ventilation and upper airway patency in a range of clinical scenarios, however its use in spontaneously breathing patients during general anaesthesia has not been described. Spontaneous respiration using i.v. anaesthesia is the primary technique used at our institution for tubeless airway surgery. We hypothesized that the addition of HFNO would increase our margin of safety, particularly during management of an obstructed airway. MethodsA retrospective observational study was conducted using a SponTaneous Respiration using IntraVEnous anaesthesia and High-flow nasal oxygen (STRIVE Hi) technique to manage 30 adult patients undergoing elective laryngotracheal surgery. ResultsTwenty-six patients (87%) presented with significant airway and/or respiratory compromise (16 were stridulous, 10 were dyspnoeic). No episodes of apnoea or complete airway obstruction occurred during the induction of anaesthesia using STRIVE Hi. The median [IQR (range)] lowest oxygen saturation during the induction period was 100 [99–100 (97–100)] %. The median [IQR (range)] overall duration of spontaneous ventilation was 44 [40–49.5 (18–100)] min. The median [IQR (range)] end-tidal carbon dioxide (ETCO2) level at the end of the spontaneous ventilation period was 6.8 [6.4–7.1 (4.8–8.9)] kPa. The mean rate of increase in ETCO2 was 0.03 kPa min−1. ConclusionsSTRIVE Hi succeeded in preserving adequate oxygen saturation, end-tidal carbon dioxide and airway patency. We suggest that the upper and lower airway benefits attributed to HFNO, are ideally suited to a spontaneous respiration induction, increasing its margin of safety. STRIVE Hi is a modern alternative to the traditional inhalation induction.

Management of Low Tidal Volume and ETCO2 during Thoracoscopy in the Treatment of Tracheo-Esophageal Fistula: A Case Report

Esophageal atresia with tracheo-oesophageal fistula (TEF) occurs in 1 in 2500-3000 live births. Management of airway and ventilation in TEF repair is challenging. Nowadays, advances in minimally invasive surgical techniques and neonatal intensive care for neonates have allowed endoscopically repair of TEF, which lends another level of complexity to airway management. Usually, a sudden increase in ETCO2 should alert the anesthesiologist to possible surgical trauma and entrainment of thoracoscopic gas. However, low ETCO2 emerging with low tidal volume can also alerts the anesthesiologist to possible surgical trauma. We had an uncommon situation, where a sudden low ETCO2 emerged with low tidal volume when doing the complete anastomosis. After communicating with surgeons, they stopped and tried to find the possible causes. Finally, it appeared to be a surgical injury on the right lung. Continuous communication between the surgeon and the anesthesiologist is imperative when performing these operations.

Does the end-tidal carbon dioxide (etCo2) concentration during the resuscitation have prognostic value on surviving in out-of hospital cardiac arrest

Introduction: Since 2010. capnography is recommended method of monitoring in advanced life support by the European Resuscitation Council and in 2015. The guidelline highlights the importance of capnography in resuscitation. The aim of the research is to determine the connection between EtCO2 and surviving and favourable outcome of OHCA victims, as an upgrade from OHCA International Studies 'Eureca One', which is implemented in Indjija's emergency service. Methodology: The study was conducted as a prospective observational study of data collection out-of-hospital cardiac arrest in the period 01.10.2015 - 31.09.2016. according to the methodology Eureca One study in 2015. which followed the next 11 months. Data on the SCD are administered in a single questionnaire 'Utstein' methodology. In addition to the questionnaire EtCO2 value were monitored. EtCO2 values are recorded with tape record in a special form: the initial EtCO2, EtCO2 in the second minute, the final EtCO2 and average value of EtCO2. Results: In the victims who underwent advance life support measures did not achieve ROSC initial EtCO2 was 7.1 mmHg, 13.2 mmHg the average and final 12.1 mmHg. Average EtCO2 after 2 minutes the implementation of advanced life support was 11.6 mmHg and the average difference was 4.5 mmHg. When the victims who underwent resuscitation and achieved ROSC initial EtCO2 was 14.48 mmHg, average 22.22 mmHg and 26.21 mmHg final. Average EtCO2 after 2 minutes the implementation of advanced life support was 25.27 mmHg and the average difference was 10.79 mmHg Conclusion: The trend of increase in EtCO2 after 2 minutes of resuscitation is the most important predictor of return of spontaneous circulation. The upward trend in EtCO2 after 2 minutes could be a good indicator of the outcome in resuscitation and further research is needed.

Utility of end-tidal carbon dioxide monitoring in intramuscular ketamine sedation in the pediatric emergency department

Purpose Recently, the use of end-tidal carbon dioxide (ETCO2) monitoring has been suggested for early detection of hypoventilation over oxygen saturation (SPO2) monitoring. We aimed to determine the usefulness of capnography in monitoring patients sedated using intramuscular (IM) ketamine in the pediatric emergency department (ED). Methods This study retrospectively reviewed medical records of patients younger than 16 years who were sedated using IM ketamine and whose ETCO2 values were documented in the ED. Age, sex, American Society of Anesthesiologists physical status classification (ASA classification), and purpose of sedation were investigated. Vital signs were recorded at pre-sedation, 5 and 10 minutes after sedation, and after recovery. Hypoventilation was defined as S P O2 < 95%, ETCO2 ≥ 50 mmHg or ≤30 mmHg, or increase in ETCO2 ≥ 10 mmHg from the baseline without tachypnea. Results A total of 49 patients were investigated; 42 of them belonged to ASA classification I, and 7 to II. There was no patient with SPO2 < 95%, or ETCO2 ≥ 50 mmHg, or increase in ETCO2 ≥ 10 mmHg from the pre-sedation value. However, 5 patients had an ETCO2 ≤ 30 mmHg, and 4 of them (8.2%) had normal respiratory rate and were suitable for hypopneic hypoventilation. Ten patients showed abnormal range of ETCO2 (normal range, 35–45 mmHg), but did not meet the definition of hypoventilation. No one had clinically serious respiratory events. Conclusion During sedation using IM ketamine, 8.2% of the patients had hypopneic hypoventilation without hypoxemia, and they were all younger than 36 months. Capnography for patients sedated using IM ketamine in the ED is useful in detecting hypopneic hypoventilation, and has the potential for preventing clinically serious respiratory events in patients, especially toddlers. Key Words: Capnography; Conscious Sedation; Hypoventilation; Ketamine; Pediatrics

A comparison of 3 ventilation strategies in children younger than 1 year using a Proseal laryngeal mask airway: a randomized controlled trial

Study ObjectiveTo determine quantitative differences in several routinely measured ventilation parameters using a standardized anesthetic technique and 3 different ventilation modalities in patients younger than 1 year with a ProSeal laryngeal mask airway (PLMA). DesignRandomized prospective study. SettingTertiary care pediatric hospital. PatientsThirty-nine American Society Anesthesiologists classifications 1 to 2, pediatric patients younger than 1 year. InterventionsThree different ventilation strategies (spontaneous ventilation [SV], pressure support ventilation [PSV], and pressure-controlled ventilation [PCV]) were randomly applied to patients who underwent a standardized mask induction with sevoflurane/oxygen and propofol 2 mg/kg and fentanyl 2 μg/kg administered intravenously followed by PLMA insertion. Patients were maintained on sevoflurane and N2O. MeasurementsWe measured the differences in end-tidal CO2 (etco2), tidal volume (TV), and respiratory rate (RR) over time between SV, PSV, and PCV. These data were recorded at 5-minute intervals. Main Resultsetco2 (mm Hg) was not significantly higher in the SV vs PSV (P=2.11) and SV vs PCV (P=.24). TV (mL/kg) was significantly lower in SV vs PSV (P<.005) and SV vs PCV (P<.005). RR was not significantly higher in SV vs PSV (P=.43), but was significantly higher in SV vs PCV (P<.005). Three patients in the SV group and 1 patient in the PSV group failed to initiate SV and required PCV and were thus excluded from analysis. ConclusionsAll 3 modes of ventilation using a PLMA were safe in children younger than 1 year. Although we did not observe a statistically significant increase in etco2, differences in TV and RR, and the small but significant incidence of apnea may make PSV or PCV more optimal ventilation strategies in children younger than 1 year when using a PLMA.

Association Between End-Tidal Carbon Dioxide Pressure and Cardiac Output During Fluid Expansion in Operative Patients Depend on the Change of Oxygen Extraction.

In a model of hemorrhagic shock, end-tidal carbon dioxide tension (EtCO2) has been shown to reflect the dependence of oxygen delivery (DO2) and oxygen consumption (VO2) at the onset of shock. The objectives of the present study were to determine whether variations in EtCO2 during volume expansion (VE) are correlated with changes in oxygen extraction (O2ER) and whether EtCO2 has predictive value in this respect.All patients undergoing cardiac surgery admitted to intensive care unit in whom the physician decided to perform VE were included. EtCO2, cardiac output (CO), blood gas levels, and mean arterial pressure (MAP) were measured before and after VE with 500 mL of lactated Ringer solution. DO2, VO2, and O2ER were calculated from the central arterial and venous blood gas parameters. EtCO2 responders were defined as patients with more than a 4% increase in EtCO2 after VE. A receiver-operating characteristic curve was established for EtCO2, with a view to predicting a variation of more than 10% in O2ER.Twenty-two (43%) of the 51 included patients were EtCO2 responders. In EtCO2 nonresponders, VE increased MAP and CO. In EtCO2 responders, VE increased MAP, CO, EtCO2, and decreased O2ER. Changes in EtCO2 were correlated with changes in CO and O2ER during VE (P < 0.05). The variation of EtCO2 during VE predicted a decrease of over 10% in O2ER (area under the curve [95% confidence interval]: 0.88 [0.77–0.96]; P < 0.0001).During VE, an increase in EtCO2 did not systematically reflect an increase in CO. Only patients with a high O2ER (i.e., low ScvO2 values) display an increase in EtCO2. EtCO2 changes during fluid challenge predict changes in O2ER.

Association between Prehospital CPR Quality and End-Tidal Carbon Dioxide Levels in Out-of-Hospital Cardiac Arrest

Introduction: International Guidelines recommend measurement of end-tidal carbon dioxide (EtCO2) to enhance cardiopulmonary resuscitation (CPR) quality and optimize blood flow during CPR. Numerous factors impact EtCO2 (e.g., ventilation, metabolism, cardiac output), yet few clinical studies have correlated CPR quality and EtCO2 during actual out-of-hospital cardiac arrest (OHCA) resuscitations. The purpose of this study was to describe the association between EtCO2 and CPR quality variables during OHCA. Methods: This is an observational study of prospectively collected CPR quality and capnography data from two EMS agencies participating in a statewide resuscitation quality improvement program. CPR quality and capnography data from adult (≥18 years) cardiac resuscitation attempts (10/2008–06/2013) were collected and analyzed on a minute-by-minute basis using RescueNet™ Code Review. Linear mixed effect models were used to evaluate the association between (log-transformed) EtCO2 level and CPR variables: chest compression (CC) depth, CC rate, CC release velocity (CCRV), ventilation rate. Results: Among the 1217 adult OHCA cases of presumed cardiac etiology, 925 (76.0%) had a monitor-defibrillator file with CPR quality data, of which 296 (32.0%) cases had >1 minute of capnography data during CPR. After capnography quality review, 66 of these cases (22.3%) were excluded due to uninterpretable capnography, resulting in a final study sample of 230 subjects (mean age 68 years; 69.1% male), with a total of 1581 minutes of data. After adjustment for other CPR variables, a 10 mm increase in CC depth was associated with a 4.0% increase in EtCO2 (p < 0.0001), a 10 compression/minute increase in CC rate with a 1.7% increase in EtCO2 (p = 0.02), a 10 mm/second increase in CCRV with a 2.8% increase in EtCO2 (p = 0.03), and a 10 breath/minute increase in ventilation rate with a 17.4% decrease in EtCO2 (p < 0.0001). Conclusion: When controlling for known CPR quality variables, increases in CC depth, CC rate and CCRV were each associated with a statistically significant but clinically modest increase in EtCO2. Given the small effect sizes, the clinical utility of using EtCO2 to guide CPR performance is unclear. Further research is needed to determine the practicality and impact of using real-time EtCO2 to guide CPR delivery in the prehospital environment.

Using Near Infrared Spectroscopy for Tissue Oxygenation Monitoring During Procedural Sedation: The Occurrence of Peripheral Tissue Oxygenation Changes With Respiratory Depression and Supportive Airway Measures.

The objective was to assess whether respiratory depression and supportive airway measures occurring during procedural sedation are associated with changes in peripheral tissue oxygen saturation (StO2 ). This was a prospective observational study of adult patients undergoing procedural sedation in the emergency department (ED). Patients undergoing sedation with propofol, 1:1 propofol and ketamine, and 4:1 propofol and ketamine were included. Clinical interventions, sedative medication doses, vital signs, end-tidal capnography (ETCO2 ), pulse oximetry (SpO2 ), and peripheral tissue oxygen saturation (StO2 ) were recorded. Respiratory depression was defined as the occurrence of a recorded SpO2 <92%, an increase in ETCO2 >10 mm Hg from baseline, or loss of capnography waveform. Supportive airway measures documented during the procedure included bag-valve mask ventilation, airway repositioning maneuvers, increase in supplemental oxygen, and stimulation to induce respiration. Relative changes in StO2 between baseline and nadir were compared among patients who met respiratory depression criteria or required a supportive airway measure and those who did not. Ninety-three patients were enrolled. Thirty-two patients (34.4%) met criteria for respiratory depression, and 31 (33.3%) required intervention in the form of a supportive airway measure. The median percent change in StO2 from procedure baseline to nadir in patients meeting criteria for respiratory depression was 13.6%, compared to 4.2% in those who did not. The change in StO2 in patients who required a supportive airway measure was 12.5% versus 5.4% in those who did not. Patients with respiratory depression and the use of supportive airway measures had greater changes in StO2 during procedural sedation than in patients who did not. Peripheral tissue oxygen saturation monitoring may be a useful tool for assessing respiratory adverse events in patients undergoing procedural sedation in the ED.

Capnometry monitoring during intravenous sedation with midazolam for oral surgery

AbstractAimsTo investigate changes in end‐tidal carbon dioxide (ETCO2) and the utility of ETCO2 as an additional monitor of ventilation during intravenous sedation with midazolam for oral surgery. There are no data on capnography in dental sedation, nor is the frequency of abnormal ventilatory activity known in this setting.Materials and methodsThis was a prospective observational study of 33 healthy adults (mean age 38 years). Monitoring included pulse oximetry, blood pressure measurement and visual assessment. Patients were also monitored with blinded capnometry.ResultsPost‐hoc analysis revealed 33% of patients had peripheral capillary oxygen saturation (SPO2) &lt; 95% and 30% had ETCO2 changes indicating respiratory depression. Mean increase in ETCO2 was 2.19 mm Hg (95% confidence interval = 0.83–3.55) P = 0.0025 during sedation.ConclusionDuring intravenous sedation for oral surgery in healthy adult's breathing room air, significant changes in ETCO2 values occur. However, desaturation detectable by pulse oximetry usually occurs before clinically significant changes in capnometry are recognisable.

Massive subcutaneous emphysema following laparoscopic nephroureterectomy: An unusual presentation

Sir, Laparoscopic approach to surgery has expanded its horizon tremendously. It is a preferred approach in many general, urological and thoracic procedures. Massive subcutaneous emphysema is a rare complication of laparoscopic surgery. We report here such a complication after laparoscopic nephroureterectomy using carbon dioxide (CO2) as an insufflating gas. A 62 yr old male, weight 65kg, American Society of Anesthesiologists physical status II was scheduled for nephroureterectomy for sarcoma left kidney through transperitoneal approach. The only positive history revealed in preoperative evaluation was hypertension since 2 yrs. In the operating room, intravascular cannulation was established after baseline routine monitoring [electrocardiography, non-invasive blood pressure, pulse oximetric oxygen saturation (SpO2) and end-tidal CO2, (ETCO2)]. Standard general anaesthesia induction and intubation was performed using injection fentanyl, propofol and vecuronium bromide. Patient was maintained on O2:N2O (35:65) and isoflurane. Pneumoperitoneum was created using CO2 insufflation and was maintained for 4 hours. Intraoperatively, cardiovascular parameters, EtCO2 and peak inspiratory pressure remained normal throughout. The intra- abdominal pressure was in the range of 12-13 mm Hg. Maximum EtCO2 noticed during this period was 42mm Hg, which was normalised by increasing minute ventilation. 3 h after creation of pneumo-peritoneum, patient was noted to have developed marked subcutaneous emphysema over face, neck and chest. Skin crepitus was more on lateral aspects of neck bilaterally. It involved both the eyelids. Caudal extent of emphysema could not be demarcated due to patient positioning and surgical drapes. Arterial blood gas analysis (ABG) was obtained and found to be normal. All ventilatory parameters including EtCO2 were within normal limits at this moment. The surgeon was notified about emphysema. Pneumoperitoneum was deflated after nephrectomy. Uretrectomy was done after opening the abdomen. Entire surgery lasted for 6 hrs. Facial swelling and crepitus over neck started resolving gradually after deflation of pneumoperitoneum. At the end of surgery, direct laryngoscopy was done to exclude the presence of pharyngeal emphysema and laryngeal oedema which may accompany subcutaneous emphysema of face and neck and can cause airway obstruction. Arterial blood gas (ABG) values were repeated and found to be normal. The patient was extubated after confirming audible leak on positive pressure ventilation, after deflating the endotracheal tube cuff, ruling out tracheal compression by neck emphysema. Gaseous collection was allowed to be drained by spontaneous absorption and exhalation. Patient was transferred to ICU for further monitoring. Postoperative chest radiograph in intensive care unit (ICU) confirmed the diagnosis of surgical emphysema in the neck and chest and ruled out pneumothorax and pneumomediastinum. Patient remained stable in post operative period and was transferred to ward next day. Massive subcutaneous emphysema is an extremely rare complication.[1,2] On palpation, it produces an unusual crackling sensation as the gas in pushed through the tissues. Severity of emphysema can be compared on a four point scale.[3] (0) No subcutaneous emphysema, (1) Mild emphysema with crepitus at trocar insertion site, (2) Mild emphysema with crepitus extending to the abdomen and thighs. (3) Massive emphysema extending to the chest, neck and face. Prolonged surgery and pneumoperitoneum of >200 minutes, insufflation of CO2 at pressure ≥15 mm Hg, 6 or more ports and old age due to decrease in natural subcutaneous resistance are the factors which predispose to the risk of development of subcutaneous emphysema.[4,5] The patient had massive subcutaneous emphysema probably due to prolonged pneumoperitoneum of 4 hours duration. Age of the patient was another possible factor which may be responsible for such massive emphysema. Absence of rise in EtCO2 was unusual, a finding contrary to most reports where an increase in EtCO2 was found along with massive subcutaneous emphysema. Our findings are consistent with the finding of Giorgakis and Fernandez-Diaz where they found no increase in EtCO2 intraoperatively.[6] In view of the paucity of literature showing massive subcutaneous emphysema in the absence of increased EtCO2, we wished to share our experience. We recommend that the patient should be closely examined under the drapes intraoperatively even if ventilatory parameters are normal on monitor.

Capnodynamic Estimation of Lung Volumes: Teething Issues of a Potential Early Warning System

I would like to commend Albu et al.1 for their well-designed study evaluating the correlation between effective lung volume (ELV) and end-expiratory lung volume (EELV) in healthy and surfactant-depleted rabbit lungs with various levels of positive end-expiratory pressure.The results have indicated that the correlation between ELV and EELV improves with higher positive end-expiratory pressure, and is best in surfactant-depleted lungs, with the ELV being an overestimate of ELV in healthy lungs by as much as 150 ± 13% at 0 cm H2O. The authors have hypothesized that this is due to carbon dioxide being an intrinsic gas and the ELV/EELV difference is affected by changes in pulmonary capillary volume and ventilation–perfusion mismatch. There are other methodological factors that may affect this correlation, but no method is able to satisfactorily correct for those, and any attempt may potentially require a more complicated set-up than the elegant one Albu et al. propose.2However, for neonatal patients (whom a rabbit model is supposed to simulate), lung injury is on a continuum from healthy to surfactant-depleted. Generally a surfactant-depleted state is avoided by the following two interventions—antenatal glucocorticoid therapy and the instillation of exogenous surfactant into the neonatal lung. Therefore, most neonates requiring ventilator support for perioperative or critical care will be somewhere in the middle—having neither healthy nor surfactant-depleted lungs. The lack of demonstrable reliability of ELV in this gray zone undermines the utility of its absolute value as an estimation of the EELV in this setting.The authors imply that trending the change in ELV would be more useful than the absolute value. I would be concerned however that the percentage change in ELV and EELV postlavage differs significantly between different positive end-expiratory pressure values. The difference is greatest at 0 and 9 cm H2O, but this mitigates the issue somewhat because an optimal and protective lung ventilation strategy in neonates is unlikely to be at these extremes. Nevertheless, it may be difficult to estimate the degree of change in actual lung volumes after a decrease in ELV, and may lead a provider to utilize an overly aggressive recruitment strategy that could potentially result in barotrauma.It should be noted that the sensitivity of ELV to changes to effectiveness in ventilation and as a rough measure of physiological dead space could be useful when paired with other indices that together may indicate lung dysfunction.3 For example, a decreasing ELV with increasing airway resistance and pressures can serve as a preliminary warning before an appreciable increase in ETco2 or a suboptimal arterial blood gas result. At present, such dysfunction is only detected after an arterial blood gas result, and there is no simple, continuous and noninvasive method to detect lung atelectasis and institute recruitment measures early.I believe the greatest value of this study is that the method they describe can be easily implemented as part of an early warning protocol for recruitment manoeuvres, and then a gauge of the effectiveness of the intervention.3 Further studies and modification of the algorithm should be done to improve the accuracy of ELV as an estimate of EELV in various lung states and ventilator settings. This may then allow its potential to be realized as a simple yet powerful tool currently absent from the arsenal available to modern anesthesiologists and intensivists.The author declares no competing interests.

Abstract 304: Conversion of Ventricular Fibrillation to an Organized Rhythm Without a Defibrillator

Background: Reports of pulseless ventricular tachycardia (VT) or ventricular fibrillation (VF) converting to an organized rhythm without defibrillator use are rare. We wish to report a series of such cases in the randomized Circulation Improving Resuscitation Care (CIRC) trial comparing outcome between integrated AutoPulse CPR (iA-CPR) and Manual-CPR (M-CPR) in patients with out-of-hospital cardiac arrest (OHCA) of presumed cardiac etiology. Methods: Defibrillator ECGs were studied to determine rhythm one minute after defibrillation attempts and rhythm immediately before the next defibrillation attempt. Rhythms were categorized as VF, pulseless VT, asystole or an organized rhythm. Organized rhythms were classified as either pulseless electrical activity (PEA) or as return of spontaneous circulation (ROSC) if accompanied by a steep increase in EtCO2, trans-thoracic impedance showing typical “dips,” and a detectable pulse. Results: In 1603 patients with analyzable date and a shockable rhythm there were 13 cases of VF/VT (10/3) conversions to PEA or ROSC during periods with external chest compressions without defibrillation attempts. In eight of the 10 VF cases chest compressions converted VF to PEA (5 iA-CPR vs 3 M-CPR) and in two to ROSC (2 iA-CPR vs 0 M-CPR). With VT one case converted to PEA (M-CPR ) and two to ROSC (2 iA-CPR vs 0 M-CPR). Examples will be presented. Conclusion: This study documents that conversion of VF or VT to an organized rhythm during CPR without electrical assistance is possible but rare.

Abstract 189: Characterizing Continuous Capnography at the Onset of Return of Spontaneous Circulation

BACKGROUND: Manual pulse checks are often unreliable and result in prolonged pauses in chest compressions, which may be deleterious to patient outcomes. Capnography has the potential to minimize these pauses, but the threshold for determining a pulse is not known. METHODS: We conducted a prospective study of consecutive, adult, in-hospital cardiac arrests with documented return of spontaneous circulation (ROSC) at a single academic center between April 2006 and March 2012. CPR parameters and capnography were recorded using a CPR-sensing defibrillator equipped with sidestream capnography (HeartStart MRX with QCPR, Philips Healthcare; MicroStream, Oridion). All cases with continuous capnography and compression data for at least 2 minutes preceding ROSC were included in the analysis. End-tidal carbon dioxide (ETCO2) values were extracted electronically using custom software and the nadir and peak surrounding the last chest compression were manually identified. RESULTS: A total of 69 cases met inclusion criteria. The median ETCO2 nadir was 14 mmHg (range 2 - 23), which rose to a median peak of 43 mmHg (range 21 - 98), yielding a median relative rise of 215% (range 44-1944). The figure displays the changes in ETCO2 before and after the peak. The median time from nadir to peak ETCO2 was 108 s (range 24 - 501), and the median rise was 0.25 mmHg/s (range 0.05 - 0.92). The peak occurred a median of -4.4 s relative to the last chest compression. At the end of chest compressions, the median ETCO2 was 29 mmHg (range 13 - 58), without a significant drop-off when compressions were held. At the end of chest compressions, the median ventilation and heart rate were 14/min (range 6 - 34) and 126/min (range 36 - 225), respectively. CONCLUSION: In this sample, we found that ROSC was accompanied by an abrupt increase in ETCO2. This rise has the potential to be used as a pulse detector. Future work should assess whether the failure of this rise obviates the need for a pulse check.

Intravenous Sodium Bicarbonate Verifies Intravenous Position of Catheters in Ventilated Children

Vascular access in children carries a significant risk of accidental extravasation of IV fluids and medications with the potential for tissue injury. In this prospective controlled study we assessed the diagnostic utility of using IV diluted sodium bicarbonate to confirm placement of IV catheters in ventilated children. Diluted sodium bicarbonate was created using undiluted standard 8.4% (1 mEq/mL) sodium bicarbonate mixed in a 1:3 and 1:5 ratio with sterile water to achieve a final diluted concentration of 2.1% (0. 25 mEq/mL) and 1.05% (0.125 mEq/mL) sodium bicarbonate, respectively. In 18 ASA I-II mechanically ventilated children ages 1 to 8 years, the effects of 1 mL/kg of dilute 2.1%, 1.05% sodium bicarbonate, or 0.9% normal saline, injected in a randomized order, were analyzed. All children had oxygen saturation, arterial blood pressure, electrocardiograph, and end-tidal carbon dioxide (ETCO(2)) monitoring. In addition, venous blood samples were taken before injection and 10 minutes after the final injection for analysis of venous blood pH and electrolytes. In children, IV diluted 2.1% sodium bicarbonate resulted in significantly increased etco(2) (mean of 32.8 ± 3.4 mm Hg to 39.0 ± 3.5 mm Hg, P < 0.001), a mean increase of 6.2 mm Hg (95% prediction interval: 4.3 to 8.1 mm Hg) within 3 breaths. Intravenous diluted 1.05% sodium bicarbonate caused a less pronounced but still significant increase in etco(2) (33.4 ± 3.8 mm Hg to 36.3 ± 3.4 mm Hg, P < 0.001), a mean increase of 2.9 mm Hg (95% prediction interval: 1.8 to 4.1 mm Hg) within 3 breaths. Normal saline did not result in any significant changes, with a mean increase of 0.06 mm Hg (95% prediction interval: -1.3 to 1.4 mm Hg). Both concentrations of sodium bicarbonate were easily differentiated from normal saline injection by blinded anesthesiologists observing the change in etco(2) values immediately after injection. Analysis of pre- and postinjection venous pH, bicarbonate, and sodium levels could not detect clinically significant changes. A small but statistically significant increase in venous bicarbonate was noted. The injection of 2.1% sodium bicarbonate in mechanically ventilated ASA I-II children identified intravascular placement and patency of an IV catheter by an increase in the exhaled CO(2) concentration. The injections did not have any clinically significant effects on blood pH, bicarbonate, or sodium concentration.