Mainstream vs. sidestream capnometry for prediction of arterial carbon dioxide tension during supine craniotomy

Comparison of tracheal versus esophageal temperatures during laparoscopic surgery

PURPOSE

Recently, endotracheal tubes with an embedded temperature sensor in the inner surface of the tube cuff (temperature tracheal tubes) have been developed. We sought to assess whether temperature tracheal tubes show a good agreement with esophageal temperature probes during surgery.

METHODS

We enrolled 40 patients who underwent laparoscopic surgery in an observational study. The tracheas of all patients were intubated with a temperature tracheal tube, and an esophageal temperature probe was inserted into the esophagus. Tracheal and esophageal temperatures were recorded at 15-min intervals until the end of surgery. Temperatures from both devices were analyzed using Bland-Altman analysis, four-quadrant plots, and polar plots.

RESULTS

We analyzed 261 data points from 36 patients. Temperatures ranges were 34.2 °C to 36.6 °C for the tracheal temperature tube and 34.7 °C to 37.2 °C for the esophageal temperature probe. Bland-Altman analysis showed an acceptable agreement between the two devices, with an overall mean bias (95% limit of agreement) of -0.3 °C (-0.8 °C to 0.1 °C) and a percentage error of 3%; the trending ability (temperature changes over time) between the two devices showed a concordance rate of 94% in four-quadrant plot (cut-off ≥ 92%), but this was higher than the acceptable mean angular bias of 177° (cut-off <  ± 5°) and radial limits of agreement of 52° (cut-off <  ± 30°) in the polar plot. Bronchoscopy during extubation and patient interviews at six hours postoperatively revealed no serious injuries related to the use of the temperature tracheal tube.

CONCLUSION

The temperature tracheal tube showed an acceptable overall mean bias of -0.3 °C and a percentage error of 3%, but incompatible trending ability with the esophageal temperature probe.

STUDY REGISTRATION

cris.nih.go.kr (KCT0007265); 22 April 2022.

Closed-Loop ventilation using sidestream versus mainstream capnography for automated adjustments of minute ventilation-A randomized clinical trial in cardiac surgery patients

BACKGROUND

INTELLiVENT-Adaptive Support Ventilation (ASV) is a closed-loop ventilation mode that uses capnography to adjust tidal volume (VT) and respiratory rate according to a user-set end-tidal CO2 (etCO2) target range. We compared sidestream versus mainstream capnography with this ventilation mode with respect to the quality of breathing in patients after cardiac surgery.

METHODS

Single-center, single-blinded, non-inferiority, randomized clinical trial in adult patients scheduled for elective cardiac surgery that were expected to receive at least two hours of postoperative ventilation in the ICU. Patients were randomized 1:1 to closed-loop ventilation with sidestream or mainstream capnography. Each breath was classified into a zone based on the measured VT, maximum airway pressure, etCO2 and pulse oximetry. The primary outcome was the proportion of breaths spent in a predefined 'optimal' zone of ventilation during the first three hours of postoperative ventilation, with a non-inferiority margin for the difference in the proportions set at -20%. Secondary endpoints included the proportion of breaths in predefined 'acceptable' and 'critical' zones of ventilation, and the proportion of breaths with hypoxemia.

RESULTS

Of 80 randomized subjects, 78 were included in the intention-to-treat analysis. We could not confirm the non-inferiority of closed-loop ventilation using sidestream with respect to the proportion of breaths in the 'optimal' zone (mean ratio 0.87 [0.77 to ∞]; P = 0.116 for non-inferiority). The proportion of breaths with hypoxemia was higher in the sidestream capnography group versus the mainstream capnography group.

CONCLUSIONS

We could not confirm that INTELLiVENT-ASV using sidestream capnography is non-inferior to INTELLiVENT-ASV using mainstream capnography with respect to the quality of breathing in subjects receiving postoperative ventilation after cardiac surgery.

TRIAL REGISTRATION

NCT04599491 (clinicaltrials.gov).

Comparison of mainstream end tidal carbon dioxide on Y-piece side versus patient side of heat and moisture exchanger filters in critically ill adult patients: a prospective observational study

The purpose of the study was to investigate the accuracy of mainstream EtCO2 measurements on the Y-piece (filtered) side of the heat and moisture exchanger filter (HMEF) in adult critically ill patients, compared to that on the patient (unfiltered) side of HMEF. We conducted a prospective observational method comparison study between July 2019 and December 2019. Critically ill adult patients receiving mechanical ventilation with HMEF were included. We performed a noninferiority comparison of the accuracy of EtCO2 measurements on the two sides of HMEF. The accuracy was measured by the absolute difference between PaCO2 and EtCO2. We set the non-inferiority margin at + 1 mmHg in accuracy difference between the two sides of HMEF. We also assessed the agreement between PaCO2 and EtCO2 using Bland-Altman analysis. Among thirty-seven patients, the accuracy difference was - 0.14 mmHg (two-sided 90% CI - 0.58 to 0.29), and the upper limit of the CI did not exceed the predefined margin of + 1 mmHg, establishing non-inferiority of EtCO2 on the Y-piece side of HMEF (P for non-inferiority < 0.001). In the Bland-Altman analyses, 95% limits of agreement between PaCO2 and EtCO2 were similar on both sides of HMEF (Y-piece side, - 8.67 to  + 10.65 mmHg; patient side, - 8.93 to  + 10.67 mmHg). The accuracy of mainstream EtCO2 measurements on the Y-piece side of HMEF was noninferior to that on the patient side in critically ill adults. Mechanically ventilated adult patients could be accurately monitored with mainstream EtCO2 on the Y-piece side of the HMEF unless their tidal volume was extremely low.

Accuracy evaluation of mainstream and sidestream end-tidal carbon dioxide monitoring during noninvasive ventilation: a randomized crossover trial (MASCAT-NIV trial)

Background

The end-tidal partial pressure of carbon dioxide (P_ETCO₂) can be used to estimate the arterial partial pressure of carbon dioxide (PaCO₂) in patients who undergo mechanical ventilation via endotracheal intubation. However, no reliable method for measuring P_ETCO₂ during noninvasive ventilation (NIV) has been established. The purpose of this study was to evaluate the correlation and agreement between PaCO₂ and P_ETCO₂ measured by these two methods and to compare them in patients who underwent NIV after extubation.

Methods

This study was a randomized, open-label, crossover trial in a mixed intensive care unit. We included patients who were planned for NIV after extubation and for whom the difference between P_ETCO₂ and PaCO₂ was ≤ 5 mmHg. We compared mainstream capnography using an inner cup via face mask (the novel method) with sidestream capnography (the previous method) during NIV. The relationships between PaCO₂ and P_ETCO₂ were evaluated by computing the Pearson correlation coefficient, and the agreement between PaCO₂ and P_ETCO₂ was estimated using the Bland–Altman method.

Results

From April 2020 to October 2021, 60 patients were included to the study. PaCO₂ and P_ETCO₂ were well correlated in both methods (the novel methods: r = 0.92, P < 0.001; the previous method: r = 0.79, P < 0.001). Mean bias between PaCO₂ and P_ETCO₂ measured using the novel method was 2.70 (95% confidence interval [CI], 2.15–3.26) mmHg with 95% limits of agreement (LoA) ranging from − 1.61 to 7.02 mmHg, similar to the result of measurement during SBT (mean bias, 2.51; 95% CI, 2.00–3.02; 95% LoA, − 1.45 to 6.47 mmHg). In contrast, measurement using the previous method demonstrated a larger difference (mean bias, 6.22; 95% CI, 5.22–7.23; 95% LoA, − 1.54 to 13.99 mmHg).

Conclusion

The current study demonstrated that the novel P_ETCO₂ measurement was superior to the previous method for PaCO₂ prediction. During NIV, the novel method may collect as sufficient exhalation sample as during intubation. Continuous P_ETCO₂ measurement combined with peripheral oxygen saturation monitoring is expected to be useful for early recognition of respiratory failure among high-risk patients after extubation.

Trial registration UMIN-CTR UMIN000039459. Registered February 11, 2020.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40560-022-00603-w.

End-Tidal Carbon Dioxide Pressure Measurement after Prolonged Inspiratory Time Gives a Good Estimation of the Arterial Carbon Dioxide Pressure in Mechanically Ventilated Patients

Background: End-tidal carbon dioxide pressure (PetCO₂) is unreliable for monitoring PaCO₂ in several conditions because of the unpredictable value of the PaCO₂–PetCO₂ gradient. We hypothesised that increasing both the end-inspiratory pause and the expiratory time would reduce this gradient in patients ventilated for COVID-19 with Acute Respiratory Distress Syndrome and in patients anaesthetised for surgery. Methods: On the occasion of an arterial blood gas sample, an extension in inspiratory pause was carried out either by recruitment manoeuvre or by extending the end-inspiratory pause to 10 s. The end-expired PCO₂ was measured (expiratory time: 4 s) after this manoeuvre (PACO₂) in comparison with the PetCO₂ measured by the monitor. We analysed 67 Δ(a-et)CO₂, Δ(a-A)CO₂ pairs for 7 patients in the COVID group and for 27 patients in the anaesthesia group. Results are expressed as mean ± standard deviation. Results: Prolongation of the inspiratory pause significantly reduced PaCO₂–PetCO₂ gradients from 11 ± 5.7 and 5.7 ± 3.4 mm Hg (p < 0.001) to PaCO₂–PACO₂ gradients of −1.2 ± 3.3 (p = 0.043) and −1.9 ± 3.3 mm Hg (p < 0.003) in the COVID and anaesthesia groups, respectively. In the COVID group, PACO₂ showed the lowest dispersion (−7 to +6 mm Hg) and better correlation with PaCO₂ (R² = 0.92). The PACO₂ had a sensitivity of 0.81 and a specificity of 0.93 for identifying hypercapnic patients (PaCO₂ > 50 mm Hg). Conclusions: Measuring end-tidal PCO₂ after prolonged inspiratory time reduced the PaCO₂–PetCO₂ gradient to the point of obtaining values close to PaCO₂. This measure identified hypercapnic patients in both intensive care and during anaesthesia.

Comparing the novel microstream and the traditional mainstream method of end-tidal CO2 monitoring with respect to PaCO2 as gold standard in intubated critically ill children

The objective of this study was to evaluate a novel microstream method by comparison with PaCO₂ and the more standard mainstream capnometer in intubated pediatric patients. We hypothesized that the novel microstream method would superior compared to the traditional mainstream method in predicting PaCO₂. This was a prospective single-center comparative study. The study was carried out on 174 subjects with a total of 1338 values for each method. Data were collected prospectively from mainstream and microstream capnometer simultaneously and compared with PaCO₂ results. Although both mainstream PetCO₂ (mainPetCO₂) and microstream PetCO₂ (microPetCO₂) were moderately correlated (r = 0.63 and r = 0.68, respectively) with PaCO₂ values, mainPetCO₂ was in better agreement with PaCO₂ in all subjects (bias ± precision values of 3.8 ± 8.9 and 7.3 ± 8.2 mmHg, respectively). In those with severe pulmonary disease, the mainPetCO₂ and microPetCO₂ methods were highly correlated with PaCO₂ (r = 0.80 and r = 0.81, respectively); however, the biases of both methods increased (14.8 ± 9.1 mmHg and 16.2 ± 9.0 mmHg, respectively). In cases with increased physiologic dead space ventilation, the agreement levels of mainPetCO₂ and microPetCO₂ methods became distorted (bias ± precision values of 20.9 ± 11.2 and 25.0 ± 11.8 mm Hg, respectively) even though mainPetCO₂ and microPetCO₂ were highly correlated (r = 0.78 and r = 0.78, respectively). It was found that the novel microstream capnometer method for PetCO₂ measurements provided no superiority to the traditional mainstream method. Both capnometer methods may be useful in predicting the trend of PaCO₂ due to significant correlations with the gold standard measurement in cases with severe pulmonary disease or increased physiological dead space –despite reduced accuracy.

Novel mainstream capnometer system is safe and feasible even under CO2 insufflation during ERCP-related procedure: a pilot study

Background and aims

There is a need to safely achieve conscious sedation during endoscopic retrograde cholangiopancreatography (ERCP). We evaluated the safety and feasibility of a mainstream capnometer system to monitor apnoea during ERCP under CO₂ insufflation.

Methods

Non-intubated adult patients undergoing ERCP-related procedures with intravenous sedation were enrolled. End-tidal CO₂ (EtCO₂) was continuously monitored during the procedure under CO₂ insufflation using a mainstream capnometer system, comprising a capnometer and a specially designed bite block for upper gastrointestinal endoscopy and ERCP. Oxygen saturation (SpO₂) was also monitored continuously during the procedure. In this study, we evaluated the safety and feasibility of the capnometer system.

Results

Eleven patients were enrolled. Measurement of EtCO₂ concentration was possible from the beginning to the end of the procedure in all 11 cases. There was no measurement failure, dislocation of the bite block, or adverse event related to the bite block. Apnoea linked to hypoxaemia occurred five times (mean duration, 174.4 s).

Conclusion

This study confirmed that apnoea was detected earlier than when using a percutaneous oxygen monitor. Measurement of EtCO₂ concentration using the newly developed mainstream capnometer system was feasible and safe even under CO₂ insufflation.

Anaesthesia for laparoscopic nephrectomy: Does end-tidal carbon dioxide measurement correlate with arterial carbon dioxide measurement?

Background and Aims:

Not many studies have explored the correlation between arterial carbon dioxide tension (PaCO₂) and end-tidal carbon dioxide tension (ETCO₂) in surgeries requiring pneumoperitoneum of more than 1 hour duration with the patient in non-supine position. The aim of our study was to evaluate the correlation of ETCO₂ with PaCO₂ in patients undergoing laparoscopic nephrectomy under general anaesthesia.

Methods:

A descriptive study was performed in thirty patients undergoing laparoscopic nephrectomy from September 2014 to August 2015. The haemodynamic parameters, minute ventilation, PaCO₂ and ETCO₂ measured at three predetermined points during the procedure were analysed. Correlation was checked using Pearson's Correlation Coefficient Test. P <0.05 was considered statistically significant.

Results:

Statistical analysis of the values showed a positive correlation between ETCO₂ and PaCO₂ (P < 0.05). Following carbon dioxide insufflation, both ETCO₂ and PaCO₂ increased by 5.4 and 6.63 mmHg, respectively, at the end of the 1^st hour. The PaCO₂-ETCO₂ gradient was found to increase during the 1^st hour following insufflation (4.07 ± 2.05 mmHg); it returned to the pre-insufflation values in another hour (2.93 ± 1.43 mmHg).

Conclusion:

Continuous ETCO₂ monitoring is a reliable indicator of the trend in arterial CO₂ fluctuations in the American Society of Anesthesiologists Grades 1 and 2 patients undergoing laparoscopic nephrectomy under general anaesthesia.

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.

A flow-through capnometer for obstructive sleep apnea

INTRODUCTION

Capnogram is often distorted due to aspiration of expired gas when a sidestream capnometer is used for non-intubated, spontaneously breathing condition. The purpose of this study was to make a flow-through capnometer without aspiration and to check if this capnometer precisely detected apnea during obstructive sleep apnea (OSA).

METHODS

(1) Flow-through capnometer The capnometer consisted of a flow-through etCO(2) sensor, cap-ONE, and an accompanying capnometer. The size of cap-ONE was small enough to be fitted under the nose where gas expired from the nose and the mouth passed through. Thus, the expired gas to be measured is directly blown into the cap-ONE. (2) The cap-ONE using a spontaneously breathing model Capnograms obtained by the cap-ONE and sidestream capnometers during nasal and oral breathing under normal and reduced ventilation were compared with a reference capnogram. (3) Clinical study with OSA patients With nineteen OSA patients capnograms during apnea events diagnosed as OSA by polysomnography were examined using the cap-ONE. (4) Simulation study with an OSA model Apnea in which inspiratory flow was zero and small expiratory flows repeated was produced. Capnograms and apnea detection were compared between the cap-ONE and sidestream capnometers.

RESULTS

In the spontaneouly breathing model capnograms and etCO(2) of the cap-ONE during nasal and oral breathing were almost identical with the reference capnogram but those of sidetream capnometers during oral breathing were significantly reduced. In the clinical study 41% of total OSA events showed capnograms with prolonged and elevated phase with small ripples. In a simulation study reduction of CO(2) tension during no-inspiration was small and apnea was successfully detected with the cap-ONE. However, with sidestream capnometers the reduction of CO(2) tension was large and apnea was not detected.

CONCLUSIONS

We concluded that the cap-ONE can record capnograms with minimum distortion and detect apnea reliably during OSA.

Does hyperventilation improve operating condition during supratentorial craniotomy? A multicenter randomized crossover trial

BACKGROUND

Hyperventilation has been an integral, but poorly validated part of neuroanesthetic practice. We conducted a two-period, crossover, randomized trial to evaluate surgeon-assessed brain bulk and measured intracranial pressure (ICP) in patients undergoing craniotomy for removal of supratentorial brain tumors during moderate hypocapnia or normocapnia.

METHODS

Two-hundred and seventy-five adult patients with supratentorial brain tumors were randomized to one of two treatment sequences: hyperventilation (arterial carbon dioxide tension, PaCO2 = 25 +/- 2 mm Hg) followed by normoventilation (PaCO2 = 37 +/- 2 mm Hg) or normoventilation followed by hyperventilation. Ventilation and end-tidal CO2 tension were kept constant for 20 min. Patients were also randomly assigned to receive a propofol infusion or isoflurane anesthesia. At the end of each study period, subdural ICP was measured and the neurosurgeon, blinded to the treatment group, was asked to rate the brain bulk using a four-point scale.

RESULTS

Using a generalized estimation equation model, we found that hyperventilation decreased the risk of increased brain bulk by 45%, P = 0.004, 95% confidence intervals 22% to 61%, and the number needed to treat was 8. The mean (+/-SD) ICP during hyperventilation, 12.3 +/- 8.1 mm Hg, was lower than that during normoventilation, 16.2 +/- 9.6 mm Hg, P < 0.001. Anesthetic regimen did not affect brain bulk assessment or ICP.

CONCLUSIONS

In patients with supratentorial brain tumors, intraoperative hyperventilation improves surgeon-assessed brain bulk which was associated with a decrease in ICP.