Use of capnography to verify emergency ventilator sharing in the COVID-19 era

Exacerbation of COVID-19 pandemic may lead to acute shortage of ventilators, which may require shared use of ventilator as a lifesaving concept. Two model lungs were ventilated with one ventilator to i) test the adequacy of individual tidal volumes via capnography, ii) assess cross-breathing between lungs, and iii) offer a simulation-based algorithm for ensuring equal tidal volumes. Ventilation asymmetry was induced by placing rubber band around one model lung, and the uneven distribution of tidal volumes (VT) was counterbalanced by elevating airflow resistance (HR) contralaterally. VT, end-tidal CO2 concentration (ETCO2), and peak inspiratory pressure (Ppi) were measured. Unilateral LC reduced VT and elevated ETCO2 on the affected side. Under HR, VT and ETCO2 were re-equilibrated. In conclusion, capnography serves as simple, bedside method for controlling the adequacy of split ventilation in each patient. No collateral gas flow was observed between the two lungs with different time constants. Ventilator sharing may play a role in emergency situations.

Breath emulator for simulation and modelling of expired tidal breath carbon dioxide characteristics

BACKGROUND

In this work we describe a breath emulator system, used to simulate temporal characteristics of exhaled carbon dioxide (CO₂) concentration waveform versus time simulating how much CO2 is present at each phase of the human lung respiratory process. The system provides a method for testing capnometers incorporating fast response non-dispersive infrared (NDIR) CO₂ gas sensing devices - in a clinical setting, capnography devices assess ventilation which is the CO₂ movement in and out of the lungs. A mathematical model describing the waveform of the expired CO₂ characteristic and influence of CO₂ gas sensor noise factors and speed of response is presented and compared with measured and emulated data.

OBJECTIVE

A range of emulated capnogram temporal waveforms indicative of normal and restricted respiratory function demonstrated. The system can provide controlled introduction of water vapour and/ or other gases, simulating the influence of water vapour in exhaled breath and presence of other gases in a clinical setting such as anaesthetic agents (eg N₂O). This enables influence of water vapour and/ or other gases to be assessed and modelled in the performance of CO₂ gas sensors incorporated into capnography systems. As such the breath emulator provides a means of controlled testing of capnometer CO₂ gas sensors in a non-clinical setting, allowing device optimisation before use in a medical environment.

METHODS

The breath emulator uses a unique combination of mass flow controllers, needle valves and a fast acting switchable pneumatic solenoid valve (FASV), used to controllably emulate exhaled CO₂ temporal waveforms for normal and restricted respiratory function. Output data from the described emulator is compared with a mathematical model using a range of input parameters such as time constants associated with inhalation/ exhalation for different parts of the respiratory cycle and CO₂ concentration levels. Sensor noise performance is modelled, taking into account input parameters such as sampling period, sensor temperature, sensing light throughput and pathlength.

RESULTS

The system described here produces realistic human capnographic waveforms and has the capability to emulate various waveforms associated with chronic respiratory diseases and early stage detection of exacerbations. The system has the capability of diagnosing medical conditions through analysis of CO₂ waveforms. Demonstrated in this work the emulator has been used to test NDIR gas sensor technology deployed in capnometer devices prior to formal clinical trialling.

Effects of capnometry monitoring during recovery in the post-anaesthesia care unit: a randomized controlled trial in adults (CAPNOSSPI)

PURPOSE

Continuous capnography should be used on patients admitted to post-anaesthesia care units (PACUs) with endotracheal tubes, but this monitoring is not always performed. Optimized ventilation in the PACU could be part of the global standards of practice to maintain the benefits of perioperative ventilation. The main objective was to study the rate of patients with alveolar hypoventilation before tracheal extubation or Laryngeal Mask Airway (LMA) removal upon the measurement of continuous capnography.

METHODS

In this prospective, parallel-group, randomized controlled study, we enrolled adult patients admitted to the PACU after general anaesthesia with an endotracheal tube or LMA in place. Patients were randomly assigned to two groups: in the Capno + group, nurses managed the patients with access to the capnometer and end-tidal carbon dioxide pressure (PETCO₂) measurements; in the Capno- group, nurses monitored the patients without seeing PETCO₂ measurements. The primary outcome was the percentage of patients with PETCO₂ measurements above 45 mm Hg during the minute before extubation. Secondary endpoints included the delay in recovering spontaneous breathing, rate of hypoxemia, delay before extubation, and length of stay in the PACU.

RESULTS

Forty-eight patients were randomized into the two groups. The percentage of patients with PETCO₂ > 45 mm Hg the minute before extubation was significantly decreased in the Capno + group (83.3% versus 54,1% in the Capno- and Capno + groups respectively, p = 0.029). There were no significant differences concerning secondary endpoints.

CONCLUSIONS

The use of PETCO₂ monitoring improves patient safety by decreasing the incidence of CO₂ retention during recovery from general anaesthesia. This study suggests that this monitoring should be integrated in the PACU. The risk of hypoxemia can also be prevented through the early recognition of apnoea.Clinical Trial registry: clinicaltrial.gov. identifier: NCT03370081.

A capnography and transcutaneous CO2 profile of bariatric patients during early postoperative period after opioid-sparing anesthesia

BACKGROUND

Noninvasive monitoring of partial pressure of carbon dioxide can be accomplished indirectly with capnography (P_ETCO₂) or with transcutaneous carbon dioxide monitoring (P_TCCO₂). The use of capnography has been shown to offer an advantage over pulse oximetry alone in the early detection of adverse respiratory events when supplemental oxygen is administered. Furthermore, capnography allows for the monitoring of various respiratory measures, including end-tidal carbon dioxide, respiratory rate, tidal volume, and changes in breathing patterns. Transcutaneous CO₂ also closely approximates arterial CO₂ values, but is not as easy to monitor for prolonged periods. The purpose of this study was to examine the usefulness of capnography and of transcutaneous carbon dioxide monitoring in patients recovering from obesity surgery at high risk of developing postoperative obstructive sleep apnea.

METHODS

In a prospective observational study, 64 bariatric surgery patients at risk of developing obstructive sleep apnea were monitored in the postanesthesia care unit (PACU) with either capnography alone (31 patients) or capnography plus transcutaneous carbon dioxide monitoring (33 additional patients) every 3-5 minutes for the duration of their recovery. Primary endpoints included end-tidal and transcutaneous carbon dioxide, peripheral oxygen saturation, respiratory rate, pain scores, and incidence of adverse respiratory events.

RESULTS

Although no adverse pulmonary events were observed, capnography detected several patients who experienced short periods of respiratory apnea while maintaining pulse oximetry readings within normal limits. Transcutaneous values were slow to change and averaged 4.5 ± 5.5 mm Hg (P < .05) higher than corresponding end-tidal measurements.

CONCLUSIONS

These results indicate the capabilities of both these noninvasive techniques for postoperative monitoring. Capnography acutely monitors changes in respiration, whereas transcutaneous monitoring more accurately reflects arterial CO₂ levels.

A comparison of the breathing apparatus deadspace associated with a supraglottic airway and endotracheal tube using volumetric capnography in young children

Background

Supraglottic airway (SGA) devices including the air-Q^® are being used with increasing frequency for anesthesia in infants and younger pediatric patients. To date, there is minimal research documenting the potentially significant airway deadspace these devices may contribute to the ventilation circuit when compared to an endotracheal tube (ETT). The aim of this study was to evaluate the airway apparatus deadspace associated with an air-Q^® versus an ETT in young children.

Methods

In a prospective cohort study, 59 patients between 3 months and 6 years of age, weighing between 5 and 20 kg, scheduled for outpatient urologic or general surgery procedures were recruited. An air-Q^® or ETT was inserted at the discretion of the attending anesthesiologist, and tidal volume, positive end expiratory pressure, respiratory rate, and end-tidal CO₂ were controlled according to protocol. Airway deadspace was recorded using volumetric capnography every 2 min for 10 min.

Results

Groups were similar in demographics. There was a significant difference in weight-adjusted deadspace volume between the air-Q^® and ETT groups, 4.1 ± 0.8 ml/kg versus 3.0 ± 0.7 ml/kg, respectively (P < 0.001). Weight-adjusted deadspace volume (ml/kg) increased significantly with decreasing weight for both the air-Q^® and ETT groups.

Conclusions

In healthy children undergoing positive pressure ventilation for elective surgery, the air-Q^® SGA introduces significantly greater airway deadspace than an ETT. Additionally, airway deadspace, and minute ventilation required to maintain normocarbia, appear to increase with decreasing patient weight irrespective of whether a SGA or ETT is used.

[Non-invasive home ventilation in patients with severe hypercapnic chronic obstructive pulmonary disease: The SOMNOVENT' study]

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a major cause of morbidity and mortality, especially in cases of chronic hypercapnic respiratory failure. Following a prolonged debate, the indication and benefits of noninvasive ventilation (NIV) have been recently established. Although improved ventilation and reduction in hyperinflation appear to underlie the positive effect on NIV in COPD, only a few studies have focused on specific ventilatory algorithms for improving PaCO2.

METHODS

The main objective of this study is to analyze the impact of Löwenstein's ventilatory algorithms, supposed to allow a better management of hyperinflation and its consequences on alveolar ventilation and blood gas parameters. This is an interventional study in routine care, prospective, single blind, randomized with cross over. The primary endpoint will be the transcutaneous partial pressure of nocturnal carbon dioxide. Secondary endpoints will be: abnormal respiratory events occurring during nocturnal NIV; the objective quality of sleep via polysomnography; the tolerance of ventilation and the subjective quality of sleep evaluated by auto questionnaires.

EXPECTED RESULTS

The results of this study will clarify whether is it necessary to explore more the impact of the ventilatory modes developed by Löwenstein, dedicated to hypercapnic COPD patients, requiring a long-term NIV.

Assessment of end-tidal carbon dioxide and vena cava collapsibility in volume responsiveness in spontaneously breathing patients

BACKGROUND

The benefit of end-tidal carbon dioxide (ETCO2) and inferior vena cava collapsibility index (IVCCI) in predicting fluid responsiveness in mechanically ventilated patients has been demonstrated. However, the data on spontaneously breathing patients is controversial. This study aims to investigate the accuracy of variations in the ETCO2 (∆ETCO2) and IVCCI (∆IVCCI) gradient in predicting volume responsiveness in spontaneously breathing patients with hypovolemia.

METHODS

This was a prospective observational study conducted in an academic emergency department (ED). Spontaneously breathing patients who required fluid resuscitation due to hypovolemia were included in the study. Cardiac output (CO), IVCCI and ETCO2 were measured before and after the passive leg raise (PRL). A change in the CO of ≥15% after the PLR were considered volume responsive. The difference in the ∆ETCO2 and ∆IVCCI were compared between the volume responsive and nonresponsive groups.

RESULTS

A total of 31 patients were included in the study, of whom 15 patients were volume responsive. The difference in the ∆ETCO2 was 4 mm Hg in the volume responsive and 2 mm Hg in the nonresponsive group (p = 0.02). There was no significant difference in ∆IVCCI between the groups. A moderate correlation was detected between the difference in ∆ETCO2 and CO (0.585; p = 0.001).

CONCLUSION

∆ETCO2 can be an alternative method in predicting volume responsiveness in spontaneously breathing patients with hypovolemia.

Automatic classification of regular and irregular capnogram segments using time- and frequency-domain features: A machine learning-based approach

BACKGROUND

The quantitative features of a capnogram signal are important clinical metrics in assessing pulmonary function. However, these features should be quantified from the regular (artefact-free) segments of the capnogram waveform.

OBJECTIVE

This paper presents a machine learning-based approach for the automatic classification of regular and irregular capnogram segments.

METHODS

Herein, we proposed four time- and two frequency-domain features experimented with the support vector machine classifier through ten-fold cross-validation. MATLAB simulation was conducted on 100 regular and 100 irregular 15 s capnogram segments. Analysis of variance was performed to investigate the significance of the proposed features. Pearson's correlation was utilized to select the relatively most substantial ones, namely variance and the area under normalized magnitude spectrum. Classification performance, using these features, was evaluated against two feature sets in which either time- or frequency-domain features only were employed.

RESULTS

Results showed a classification accuracy of 86.5%, which outperformed the other cases by an average of 5.5%. The achieved specificity, sensitivity, and precision were 84%, 89% and 86.51%, respectively. The average execution time for feature extraction and classification per segment is only 36 ms.

CONCLUSION

The proposed approach can be integrated with capnography devices for real-time capnogram-based respiratory assessment. However, further research is recommended to enhance the classification performance.

A new reliable acoustic respiratory monitoring technology during upper gastrointestinal tract therapeutic endoscopy with CO2 insufflation

Previous studies documented the effectiveness and benefits of capnography monitoring during propofol-based sedation for colonoscopy to reduce the incidence of hypoxemia. However, the performance of capnography during longer duration endoscopic therapy of upper gastrointestinal tract cancers under CO₂ insufflation it is not well known. In this study, we compare a new device with acoustic monitoring technology to standard capnography monitoring. We retrospectively analyzed 49 patients who underwent endoscopic resection of early upper gastrointestinal tract cancer between December 2013 and October 2014. All 49 patients were monitored using both acoustic monitoring technology and standard capnography. We investigated the duration of the periods with unmeasurable respiratory rate during the overall procedure. When comparing standard capnography monitoring to the new acoustic monitoring technology, the ratio of the unmeasurable time was significantly lower in RRa (36.9% vs. 21.6%, p < 0.01). The ratio of unmeasurable respiratory rate by capnography was strongly correlated to the ratio of unmeasurable PETCO₂ level by capnography (R² = 0.847). There were no severe events or adverse events (grade 2 or more) during all 49 procedures. The acoustic monitoring technology provides a more reliable respiratory monitoring when compared to standard capnography during endoscopic resection of upper gastrointestinal tract cancers under CO₂ insufflation, even if the procedures were prolonged and complex.

Duration of prone position sessions: a prospective cohort study

Background

Prone position (PP) is highly recommended in moderate-to-severe ARDS. However, the optimal duration of PP sessions remains unclear. We searched to evaluate the time required to obtain the maximum physiological effect, and to search for parameters related to patient survival in PP.

Methods and results

It was a prospective, monocentric, physiological study. We included in the study all prone-positioned patients in our ICU between June 2016 and January 2018. Pulmonary mechanics, data from volumetric capnography and arterial blood gas were recorded before prone positioning, 2 h after proning, before return to a supine position (SP) and 2 h after return to SP. Dynamic parameters were recorded before proning and every 30 min during the session until 24 h. 103 patients (ARDS 95%) were included performing 231 PP sessions with a mean length of 21.5 ± 5 h per session. They presented a significant increase in pH, static compliance and P_aO₂/F_iO₂ with a significant decrease in P_aCO₂, P_plat, phase 3 slope of the volumetric capnography, P_etCO₂, V_D/V_T-phy and ΔP. The beneficial physiological effects continued after 16 h of PP and at least up to 24 h in some patients. The evolution of the respiratory parameters during the first session and also during the pooled sessions did not find any predictor of response to PP, whether before, during or 2 h after the return in SP.

Conclusions

PP sessions should be prolonged at least 24 h and be extended in the event that the P_aO₂/F_iO₂ ratio at 24 h remains below 150, especially since no criteria can predict which patient will benefit or not from it.

Trial registration The trial has been registered on 28 June 2016 in ClinicalTrials.gov (NCT 02816190) (https://clinicaltrials.gov/ct2/show/NCT02816190?term=propocap&rank=1).

Relationship between End-Tidal CO2 (ETCO2) and Lactate and their Role in Predicting Hospital Mortality in Critically Ill Trauma Patients; A Cohort Study

OBJECTIVE

To investigate the relationship between end-tidal CO₂ (ETCO₂) and serum lactate and their predictive role in hospital mortality of intubated multiple trauma patients.

METHODS

In a cohort study, intubated multiple trauma patients who referred to the emergency department for two years were enrolled. After orotracheal intubation using Rapid Sequence Intubation (RSI) method, ETCO2 was immediately measured by capnography. Blood samples for serum lactate measurements were sent to the laboratory, immediately after intubation. Data collection was done using the questionnaire, and the patients were followed using their medical records.

RESULTS

Totally, 250 patients were included with hospital mortality of 14.8% (n=37). Using Pearson correlation, an inverse relationship was noticed between serum lactate and ETCO2, immediately (p<0.0001, r=-0.65). In adjusted multivariate analysis, three variables including heart rate (HR), serum lactate and ETCO2 showed a significant relationship with hospital mortality, respectively (p=0.007, p=0.009, p=0.023, respectively). Receiver operating characteristic curve illustrated an area under the curve (AUC) of 0.93, 0.96, and 0.97 for HR, lactate, and ETCO2, respectively.

CONCLUSION

ETCO₂ post-intubation and serum lactate may be considered as prognostic factors for intubated multiple trauma patients referring to the emergency department, which can give the clinician an important clue in early prediction of the hospital mortality.

Clinical deterioration in patients with ST-elevation myocardial infarction during and for 24 h after percutaneous coronary intervention: An observational study

BACKGROUND

In-hospital adverse events such as cardiac arrest are preceded by abnormalities in physiological data and are associated with high mortality. Healthcare institutions have implemented rapid response systems such as the medical emergency team for early recognition and response to clinical deterioration. Yet, most cardiac catheterisation laboratories, have yet to formally implement a rapid response system, so the nature and frequency of clinical deterioration is unclear and no published data exist.

OBJECTIVES

To explore the nature and frequency of clinical deterioration in ST- elevation myocardial infarction patients in a cardiac catheterisation laboratory without a Medical emergency team, and 24 hours after percutaneous coronary intervention and the immediate nursing responses to clinical deterioration.

METHOD

An exploratory descriptive study using retrospective medical audit was conducted in a public tertiary teaching hospital in Melbourne, Australia. In 2014, there were 327 ST- elevation myocardial infarction presentations of which 75 were randomly selected. Descriptive statistics were used to analyse the data.

RESULTS

In the cardiac catheterisation laboratory, 82.6% of patients fulfilled medical emergency team activation criteria and deterioration was predominantly cardiovascular. Respiratory rate was not documented for all patients in cardiac catheterisation laboratory. Post percutaneous coronary intervention, 31% of patients fulfilled medical emergency team activation criteria and this deterioration occurred secondary to hypoxia. There were no documented abnormalities in respiratory rate.

CONCLUSION

The ST- elevation myocardial infarction patients admitted to the cardiac catheterisation laboratory are critically ill patients. Failure to monitor for signs of respiratory dysfunction such as respiratory rate in cardiac catheterisation laboratory may delay recognition of clinical deterioration and timely escalation of care. Further research is required to inform changes in the system to improve patient safety.

[Airway management in preclinical emergency anesthesia with respect to specialty and education]

BACKGROUND AND OBJECTIVE

Difficult airway management is a key skill in preclinical emergency medicine. A lower rate of subjective difficult airways and an increased success rate of endotracheal intubation have been reported for highly trained emergency physicians. The aim of this study was therefore to analyze the effect for different specialists and the individual state of training in the German emergency medical system.

MATERIAL AND METHODS

In a retrospective register analysis of 6024 preclinical anesthesia procedures, the frequencies of airway devices, neuromuscular blocking agents, capnography and difficult airways were analyzed with respect to specialization and status of training. Additionally, low, medium and highly experienced emergency physicians in airway management were summarized by specialization and status of training according to the Dreyfus model of skill acquisition and compared.

RESULTS

The incidence of subjective difficult airway situations was 10% for anesthesiological emergency physicians compared to 15-20% for other disciplines. The latter used supraglottic airway devices more often (7-9% vs. 4%) and video laryngoscopes less often (3% vs. 5%) compared to anesthesiological emergency physicians. The discipline-related state of training was inhomogeneous and revealed a reduced rate of supraglottic airway devices for internal specialists with further training (10% vs. 2%). Anesthetists specialized in intensive care medicine used capnography less frequently compared to other anesthetists (79% vs. 72%). With higher levels of experience in airway management, the frequency of endotracheal intubation (86% vs. 94%), neuromuscular blocking agents (59% vs. 73%) and video laryngoscopy (3% vs. 6%) increased and the incidence of subjective difficult airway situations (16% vs. 10%) decreased.

CONCLUSION

The level of training in airway management especially for non-anesthetists is inhomogeneous. The recently published German S1 guidelines for prehospital airway management recommend education and training as well as the primary use of the video laryngoscope with Macintosh blade. The implementation could lower the incidence of subjective difficult airways.

Laryngeal mask versus facemask in the respiratory management during catheter ablation

BACKGROUND

The purpose of this study is to investigate if a laryngeal mask could improve respiratory condition during radiofrequency catheter ablation (RFCA).

METHODS

Twenty-four consecutive patients who underwent RFCA for atrial fibrillation were divided into two groups (Facemask group; n = 10, Laryngeal mask group; n = 14). All patients were completely sedated under intravenous anesthesia and fitted with artificial respirators during the RFCA. The capnography waveforms and their differential coefficients were analyzed to evaluate the changes of end-tidal CO₂ (ETCO₂) values, respiratory intervals, expiratory durations, and inspiratory durations.

RESULTS

During the RFCA, ETCO₂ values of the laryngeal mask group were higher than those of the facemask group (36.0 vs. 29.2 mmHg, p = 0.005). The respiratory interval was significantly longer in the laryngeal mask group than those in the facemask group (4.28 s vs.5.25 s, p < 0.001). In both expiratory and inspiratory phases, the mean of the maximum and minimum values of CO₂ was significantly higher when using a laryngeal mask than when using a facemask. The inspiratory-expiratory ratio of the laryngeal mask group was significantly larger than that of the facemask group (1.59 vs. 1.27, p < 0.001). The total procedure duration, fluoroscopic duration and the ablation energy were significantly lower in the laryngeal mask group than in the facemask group. The ETCO₂ value is the most influential parameter on the fluoroscopic duration during the RFCA procedure (β = - 0.477, p = 0.029).

CONCLUSIONS

The use of a laryngeal mask could stabilize respiration during intravenous anesthesia, which could improve the efficiency of RFCA.

Effects of Sedation and/or Sedation/Analgesic Drugs Administered during Central Venous Catheterization on the Level of End-tidal Carbon Dioxide Measured by Nasal Cannula in Our PICU

Aims and objectives

Sedatives and analgesics are commonly used in pediatric intensive care units during minor invasive procedures. Here, we aimed to measure the changes in end-tidal carbon dioxide (EtCO₂) levels with different sedation/analgesic drug administrations (midazolam, ketamine, midazolam + ketamine/fentanyl) during central venous catheterization.

Materials and methods

This prospective study included 44 patients who needed sedation/analgesia for central venous catheterization. Patients were sedated with midazolam, ketamine, or midazolam + fentanyl/ketamine. End-tidal carbon dioxide values were measured before and after sedation-analgesia with nasal cannula and recorded from the capnograph. Oxygen saturation (SO₂) was monitored by pulse oximetry. Whether respiratory depression occurred during the process was recorded.

Results

During the procedure, 15 (34%) patients were given 0.1 mg/kg dose of midazolam described as group I, 18 (41%) patients were given 1 mg/kg dose of ketamine only described as group II, and 11 (25%) patients who could not be effective sedated with a single sedative-analgesic agent were given either 1 mg/kg dose of ketamine or 2 μg/kg dose of fentanyl together with 0.1 mg/kg dose of midazolam described as group III. According to our findings, hypoxia (54.5%) and hypercarbia (45.5%) were detected higher in group III but it was not statistically significant (p = 0.255, p = 0.364). Hypercarbia was detected in 29.5% patients, in 62% of these patients hypercarbia was accompanied by hypoxia, and 38% had only hypercarbia. When presedation and postsedation EtCO₂ values were compared, we detected a statistically significant difference in all groups.

Conclusion

We detected hypercarbia unaccompanied by hypoxemia in 38% patients. And we think that we have identified these patients early due to measurement of EtCO₂ by nasal cannula. This study demonstrated that EtCO₂ monitoring via nasal cannula is a feasible and practical way to follow ventilation during sedation/analgesia.

How to cite this article

Aslan N, Yildizdas D, Horoz OO, Arslan D, Coban Y, Sertdemir Y. Effects of Sedation and/or Sedation/Analgesic Drugs Administered during Central Venous Catheterization on the Level of End-tidal Carbon Dioxide Measured by Nasal Cannula in Our PICU. Indian J Crit Care Med 2020;24(8):705-708.

Right-Left Asymmetry of Prefrontal Cerebral Oxygenation: Does it Depend on Systemic Physiological Activity, Absolute Tissue Oxygenation or Hemoglobin Concentration?

BACKGROUND

We have repeatedly observed a right-left asymmetry (RLA) of prefrontal cerebral oxygenation of subjects during the resting state.

AIM

To clarify if the RLA is a reliably observable phenomenon at the group level and whether it is associated with systemic physiology, absolute tissue oxygen saturation (StO₂) or total hemoglobin concentration ([tHb]).

MATERIAL AND METHODS

StO₂ and [tHb] values at the right and left prefrontal cortex (PFC) were calculated for two 5- min resting phases based on data from 76 single measurements (24 healthy adults, aged 22.0 ± 6.4 years). StO₂ and [tHb] were measured with an ISS OxiplexTS frequency domain near-infrared spectroscopy device. In addition, end-tidal CO₂ (P_ETCO₂), heart rate (HR), respiration rate (RR) and the pulse-respiration quotient (PRQ = HR/RR) were measured and analyzed for the two phases.

RESULTS

On the group level it was found that i) StO₂ was higher at the right compared to the left PFC (for both phases), ii) RLA of StO₂ (∆StO₂ = StO₂ (right)-StO₂ (left) was independent of P_ETCO₂, HR and PRQ, and iii) ∆StO₂ was associated with absolute StO₂ and [tHb] values (positively and negatively, respectively).

DISCUSSION AND CONCLUSION

This study shows that i) RLA of StO₂ at the PFC is a real phenomenon, and that ii) ∆StO₂ at the group level does not depend on P_ETCO₂, HR, RR or PRQ, but on absolute StO₂ and [tHb]. We conclude that the RLA is a real effect, independent of systemic physiology, and most likely reflects genuine properties of the brain, i.e. different activity states of the two hemispheres.

Clinical Application of Pulmonary Function Testing in Small Animals

Pulmonary function tests (PFTs) are important diagnostic tools that have wide clinical applications in human and veterinary medicine. Widespread use of PFTs in measuring lung volumes in veterinary medicine was historically limited by the need for specialized equipment to accurately perform and interpret these tests, and by lack of patient cooperation. However, recent advances and modifications have allowed PFTs to be safely performed in conscious veterinary patients with minimal stress. This article focuses on the most commonly used tests of pulmonary function including tests of pulmonary mechanics and of gas exchange in the lungs.

Benefits and harms of capnography during procedures involving moderate sedation: A rapid review and meta-analysis

BACKGROUND

Patient safety is a priority in dentistry. Evaluating the benefits and harms associated with the addition of capnography to standard monitoring during moderate sedation for adult patients in the dental practice setting is needed.

TYPES OF STUDIES REVIEWED

The authors used rapid review methodology to identify relevant systematic reviews, which they updated through a systematic search by using the same search strategy as the identified reviews. The authors searched PubMed and Google Scholar and through the references of the identified systematic reviews, which yielded 2,892 studies. Inclusion criteria were that the article was available in English, was original research in adult humans who had undergone moderate procedural sedation, and involved comparing standard monitoring with the addition of capnography.

RESULTS

Sixteen studies were eligible, involving 3,866 adults undergoing procedural sedation. The authors used the Grading of Recommendations Assessment, Development and Evaluation approach to evaluate the evidence and rate it as being of moderate to low quality because of high risk of bias and heterogeneous effects for the outcomes of hypoxemia and adverse respiratory events. Capnography had higher sensitivity to detect adverse respiratory events than did standard monitoring alone (0.92; 95% confidence interval, 0.65 to 0.99) and may reduce the risk of developing hypoxemia by 31% (risk ratio, 0.69; 95% confidence interval, 0.57 to 0.82). Capnography did not affect the risk of developing serious adverse events, procedure time, sedation quality, or patient satisfaction.

CONCLUSIONS AND PRACTICAL IMPLICATIONS

Adding capnography to standard monitoring of adults during moderate sedation may reduce the risk of developing hypoxemia, increase detection of adverse respiratory events, and is not associated with additional harms. These findings suggest routine use of capnography during moderate sedation has the potential to reduce adverse anesthetic outcomes in dental practice.

Multimodal non-invasive monitoring to apply an open lung approach strategy in morbidly obese patients during bariatric surgery

To evaluate the use of non-invasive variables for monitoring an open-lung approach (OLA) strategy in bariatric surgery. Twelve morbidly obese patients undergoing bariatric surgery received a baseline protective ventilation with 8 cmH₂O of positive-end expiratory pressure (PEEP). Then, the OLA strategy was applied consisting in lung recruitment followed by a decremental PEEP trial, from 20 to 8 cmH₂O, in steps of 2 cmH₂O to find the lung's closing pressure. Baseline ventilation was then resumed setting open lung PEEP (OL-PEEP) at 2 cmH₂O above this pressure. The multimodal non-invasive variables used for monitoring OLA consisted in pulse oximetry (SpO₂), respiratory compliance (Crs), end-expiratory lung volume measured by a capnodynamic method (EELV_CO2), and esophageal manometry. OL-PEEP was detected at 15.9 ± 1.7 cmH₂O corresponding to a positive end-expiratory transpulmonary pressure (P_L,ee) of 0.9 ± 1.1 cmH₂O. ROC analysis showed that SpO₂ was more accurate (AUC 0.92, IC95% 0.87-0.97) than Crs (AUC 0.76, IC95% 0.87-0.97) and EELV_CO2 (AUC 0.73, IC95% 0.64-0.82) to detect the lung's closing pressure according to the change of P_L,ee from positive to negative values. Compared to baseline ventilation with 8 cmH₂O of PEEP, OLA increased EELV_CO2 (1309 ± 517 vs. 2177 ± 679 mL) and decreased driving pressure (18.3 ± 2.2 vs. 10.1 ± 1.7 cmH₂O), estimated shunt (17.7 ± 3.4 vs. 4.2 ± 1.4%), lung strain (0.39 ± 0.07 vs. 0.22 ± 0.06) and lung elastance (28.4 ± 5.8 vs. 15.3 ± 4.3 cmH₂O/L), respectively; all p < 0.0001. The OLA strategy can be monitored using noninvasive variables during bariatric surgery. This strategy decreased lung strain, elastance and driving pressure compared with standard protective ventilatory settings.Clinical trial number NTC03694665.

Current concepts of perioperative monitoring in high-risk surgical patients: a review

A substantial number of patients are at high-risk of intra- or post-operative complications or both. Most perioperative deaths are represented by patients who present insufficient physiological reserve to meet the demands of major surgery. Recognition and management of critical high-risk surgical patients require dedicated and effective teams, capable of preventing, recognize, start treatment with adequate support in time to refer patients to the satisfactory ICU level provision. The main task for health-care planners and managers is to identify and reduce this severe risk and to encourage patient’s safety practices. Inadequate tissue perfusion and decreased cellular oxygenation due to hypovolemia, heart dysfunction, reduced cardiovascular reserve, and concomitant diseases are the most common causes of perioperative complications. Hemodynamic, respiratory and careful sequential monitoring have become essential aspects of the clinical practice both for surgeons and intensivists. New monitoring techniques have changed significantly over the past few years and are now able to rapidly identify shock states earlier, define the etiology, and monitor the response to different therapies. Many of these techniques are now minimally invasive or non-invasive. Advanced hemodynamic and respiratory monitoring combines invasive, non-invasive monitoring skills. Non-invasive ultrasound has emerged during the last years as an essential operative and perioperative evaluation tool, and its use is now rapidly growing. Perioperative management guided by appropriate sequential clinical evaluation combined with respiratory and hemodynamic monitoring is an established tool to help clinicians to identify those patients at higher risk in the attempt to reduce the complications rate and potentially improve patient outcomes. This review aims to provide an update of currently available standard concepts and evolving technologies of the various respiratory and hemodynamic monitoring systems for the high-risk surgical patients, highlighting their potential usefulness when integrated with careful clinical evaluation.

Capnography-sample line leak and incremental positive end expiratory pressure (PEEP); an interesting interplay

The capnography is an important monitor to assess the patient's respiratory status. Importance of education for clinicians in interpretation of alarms and various capnography waveforms in different clinical scenarios and equipment malfunction is an understatement. Capnography waveforms due to sample line tube leak is described well in literature. This report describes an interesting effect of incremental positive end expiratory pressure (PEEP) on capnography waveforms linked to sample line leak.

Predictive value of capnography for severity of acute gastroenteritis in the emergency department

OBJECTIVE

This study first aims to assess the utility of ETCO2 levels in evaluating the severity of dehydration in adult patients that present to the ED with acute gastroenteritis. AGE. Second, it intends to evaluate the correlation between ETCO2 and several metabolic parameters: creatinine, pH, bicarbonate (HCO3), and bases excessive (BE).

METHOD

This prospective study was conducted with AGE patients in the ED of a training and research hospital between June 2018 and April 2019 after approval of the local ethical-committee. The two groups were defined according to the severity of AGE: mild and non-mild groups. For both groups, ETCO2 levels were measured and recorded on admission of the patients.

RESULTS

87 patients were included in the analyses. The median of ETCO2 values was found as lower in non-mild group than mild group; 30 (25-35) & 39 (33-34), respectively (p < 0.001). In ROC analysis for distinguishing between the both groups, the AUC value was found to be 0.988 and the best cut-off level was found as 33.5 with 95% sensitivity and 93% specificity. In addition, strong negative correlation between ETCO2 and creatinine (p < 0.001, r: -0.771) were found.

CONCLUSION

ETCO2 levels decreased in the non-mild group of AGE patients; it could be useful to distinguish the mild group from the non-mild group. ETCO2 could be a reliable marker in predicting AKI in the management of AGE patients.

Novel device for monitoring respiratory rate during endoscopy-A thermodynamic sensor

BACKGROUND

Monitoring ventilation accurately is an indispensable aspect of patient care in procedural settings. The current gold standard method of monitoring ventilation is by measuring exhaled carbon dioxide concentration, known as capnography. A new device utilizing thermodynamic measurement, the Linshom Respiratory Monitoring Device (LRMD), has been designed to measure respiratory rate (RR) by using the temperature of exhaled breath. We hypothesized that the temperature sensor is at least equivalent in accuracy to capnography in monitoring ventilation.

AIM

To determine if the temperature sensor is equivalent to capnography in monitoring procedural ventilation.

METHODS

In this prospective study, participants were individually fitted with a face mask monitored by both LRMD and capnography. The following data were collected: gender, age, body mass index, type of procedure, and doses of medication. For each patient, we report the mean RR for each device as well as the mean difference. All analyses were performed using SAS, and a P < 0.05 was considered statistically significant.

RESULTS

Twelve consecutive patients undergoing endoscopic procedures at our institution were enrolled. Four patients were excluded due to incomplete data, inadequate data, patient cooperation, and capnography failure. Overall, we found that LRMD RR highly correlated to capnography RR (P < 0.001); the average capnography RR increases by 0.66 breaths for every one additional breath measured by the LRMD. In addition, apnea rates were 7.4% for the capnography and 6.4% for the LRMD (95% confidence interval: 0.92-1.10).

CONCLUSION

The LRMD correlated with the gold standard capnography with respect to respiratory rate detection and apnea events. The LRMD could be used as an alternative to capnography for measuring respiration in endoscopy.

Characterization of respiratory compromise and the potential clinical utility of capnography in the post-anesthesia care unit: a blinded observational trial

The utility of capnography to detect early respiratory compromise in surgical patients after anesthesia is unclear due to limited prospective data. The purpose of this trial was to determine the frequency and duration of capnography-detected respiratory adverse events in the post-anesthesia care unit (PACU). In this prospective observational trial, 250 consenting patients undergoing elective surgery with general anesthesia were monitored by standard monitoring together with blinded capnography and pulse oximetry monitoring. The capnography notification settings were adjusted to match nursing (Level II) and physician (Level I) alarm thresholds. 163 (95%) patients had a Level II notification and 135 (78%) had a Level I notification during standard monitoring. The most common events detected by the capnography monitor included hypocapnia, apnea, tachypnea, bradypnea and hypoxemia, with silent notification duration for these events ranging from 17 ± 13 to 189 ± 127 s. During standard monitoring, 15 respiratory adverse events were reported, with 8 events occurring when valid blinded/silenced capnography and pulse oximetry data was collected simultaneously. Capnography and the Integrated Pulmonary Index™ algorithm (IPI) detected respiratory adverse events earlier than standard monitoring in 75% and 88% of cases, respectively, with an average early warning time of 8 ± 11 min. Three patients’ blinded capnography was unblinded to facilitate clinical care. Respiratory adverse events are frequent in the PACU, and the addition of capnography and IPI to current standard monitoring provides potentially clinically relevant information on respiratory status, including early warning of some respiratory adverse events.

Trial registration ClinialTrials.gov Identifier NCT02707003 (https://clinicaltrials.gov/ct2/show/NCT02707003).