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

PURPOSE

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

DESIGN

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

METHODS

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

FINDINGS

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

CONCLUSIONS

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

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

BACKGROUND

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

OBJECTIVES

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

SUBJECTS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Sedation Strategies for Procedures Outside the Operating Room

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

Capnography Monitoring During Procedural Sedation and Analgesia

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

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

BACKGROUND

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

GENERAL AIM

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

MATERIALS AND METHODS

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

RESULTS

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

LINKING EVIDENCE TO ACTION

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

Systematic Review of Capnography with Mask Ventilation during Cardiopulmonary Resuscitation Maneuvers

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

Respiratory evaluation through volumetric capnography among grade III obese and eutrophic individuals: a comparative study

BACKGROUND

Excess trunk body fat in obese individuals influences respiratory physiological function. The aims of this study were to compare volumetric capnography findings (VCap) between severely obese patients and normal-weight subjects and to assess whether there is any association between neck circumference (NC), waist-hip ratio (WHR) and VCap among grade III obese individuals.

DESIGN AND SETTING

Analytical observational case-matched cross-sectional study, University of Campinas.

METHODS

This cross-sectional study compared VCap variables between 60 stage III obese patients and 60 normal-weight individuals.

RESULTS

In comparison with the normal-weight group, obese patients presented higher alveolar minute volume (8.92 ± 4.94 versus 6.09 ± 2.2; P = < 0.0001), CO2 production (278 ± 91.0 versus 209 ± 60.23; P < 0.0001), expiratory tidal volume (807 ± 365 versus 624 ± 202; P = 0.005), CO2 production per breath (21.1 ± 9.7 versus 16.7 ± 6.16; P = 0.010) and peak expiratory flow (30.9 ± 11.9 versus 25.5 ± 9.13; P = 0.004). The end-expiratory CO2 (PetCO2) concentration (33.5 ± 4.88 versus 35.9 ± 3.79; P = 0.013) and the phase 3 slope were normalized according to expired tidal volume (0.02 ± 0.05 versus 0.03 ± 0.01; P = 0.049) were lower in the obese group.

CONCLUSIONS

The greater the NC was, the larger were the alveolar minute volume, anatomical dead space, CO2 production per minute and per breath and expiratory volume; whereas the smaller were the phase 2 slope (P2Slp), phase 3 slope (P3Slp) and pressure drop in the mouth during inspiration.

Chemical capture of wild swamp buffalo (Bubalus bubalis) in tropical northern Australia using thiafentanil, etorphine and azaperone combinations

BACKGROUND

Studying wild animals in situ is fundamental to collecting baseline information, but generally they need to be immobilised for examination, sampling, marking and/or equipping with tracking apparatus. Capturing wild animals is inherently risky and there is a need for immobilisation methods that are safe for both the animals and researchers.

METHODS

A total of 16 free-ranging swamp buffalo (Bubalus bubalis) were chemically captured by dart for the application of satellite tracking collars in tropical northern Australia; 7 animals were anesthetised with a thiafentanil-etorphine-azaperone (TEA) combination and 9 animals with a thiafentanil-azaperone (TA) combination. Anaesthesia was reversed with intravenous naltrexone. Mean dosages of etorphine and thiafentanil for animals in the TEA group were 0.01 mg/kg of each drug and mean dosage of thiafentanil for animals in the TA group was 0.02 mg/kg. Total dose per animal of azaperone and naltrexone was 80 mg and 150 mg, respectively. Anaesthetic monitoring was by physical observation of physiological variables, pulse oximetry and capnography. Blood laboratory parameters including creatine kinase (CK), aspartate transaminase (AST), serum bicarbonate and anion gap were measured.

RESULTS

All subject animals recovered well from anaesthesia despite the occurrence of subclinical acidosis in some patients. There was no significant difference between the treatment groups. Conversely, chase time had an adverse effect on body temperature, irrespective of the anaesthetic combination used.

CONCLUSIONS

Thiafentanil and azaperone, with or without etorphine, delivered rapid safe, effective, reversible field anaesthesia in healthy swamp buffalo.

Assessment of newly developed real-time human respiration carbon dioxide measurement device for management of asthma outside of hospital

BACKGROUND

Assessment of asthma outside of the hospital using a patient independent device is highly in demand due to the limitation of existing devices, which are manual and unreliable if patients are not cooperative.

OBJECTIVE

The study aims to verify the use of newly developed human respiration, carbon dioxide (CO2) measurement device for the management of asthma outside of the hospital.

METHOD

The data were collected from 60 subjects aged between 18-35 years via convenience sampling method reported in UTM Health Center using the device. Furthermore, the data were normalized and analyzed using descriptive statistics, t-test, and area (Az) under receiver operating characteristic curve (ROC).

RESULT

Findings revealed that the normalized mean values of end-tidal carbon dioxide (EtCO2), Hjorth Activity (HA), and respiratory rate (RR) were lower in asthmatic compared with healthy subjects with minimum deviation from the mean. In addition, each parameter was found to significantly differ statistically for asthma and non-asthma with p< 0.05. Furthermore, the Az shows the strong association for the screening of asthma and non-asthma with an average of 0.71 (95% CI: 0.57-0.83), 0.77 (95% CI: 0.64-0.90), and 0.83 (95% CI: 0.73-0.94) for RR, EtCO2, and HA, respectively.

CONCLUSIONS

This study demonstrates that the newly developed handheld human respiration CO2 measurement device may possibly be used as an effort-independent asthma management method outside of the hospital.

Monitoring Gas Exchange During Hypothermia for Hypoxic-Ischemic Encephalopathy

OBJECTIVES

Therapeutic hypothermia is standard of care in management of moderate/severe hypoxic-ischemic encephalopathy. Persistent pulmonary hypertension of the newborn is associated with hypoxic-ischemic encephalopathy and is exacerbated by hypoxemia and hypercarbia. Gas exchange is assessed by arterial blood gas analysis (with/without correction for body temperature), pulse oximetry, and end-tidal CO2.

DESIGN

A retrospective chart review.

SETTINGS

Regional perinatal center in Western New York.

PATIENTS

Fifty-eight ventilated neonates with indwelling arterial catheter on therapeutic hypothermia.

INTERVENTION

None.

MEASUREMENT AND MAIN RESULTS

We compared pulse oximetry, PaO2, end-tidal CO2, and PaCO2 during hypothermia and normothermia in neonates with hypoxic-ischemic encephalopathy using 1,240 arterial blood gases with simultaneously documented pulse oximetry. During hypothermia, pulse oximetry 92-98% was associated with significantly lower temperature-corrected PaO2 (51 mmHg; interquartile range, 43-51) compared with normothermia (71 mmHg; interquartile range, 61-85). Throughout the range of pulse oximetry values, geometric mean PaO2 was about 23% (95% CI, 19-27%) lower during hypothermia compared with normothermia. In contrast, end-tidal CO2 accurately assessed temperature-corrected PaCO2 during normothermia and hypothermia.

CONCLUSIONS

Hypothermia shifts oxygen-hemoglobin dissociation curve to the left resulting in lower PaO2 for pulse oximetry. Monitoring oxygenation with arterial blood gas uncorrected for body temperature and pulse oximetry may underestimate hypoxemia in hypoxic-ischemic encephalopathy infants during whole-body hypothermia, while end-tidal CO2 reliably correlates with temperature-corrected PaCO2.

Confirmation of placement of endotracheal tube - A comparative observational pilot study of three ultrasound methods

Background and Aims

Confirmation of endotracheal tube (ETT) position is necessary to ensure proper ventilation. The present study was conducted with the aim to compare the efficacy of three ultrasonographic (USG) techniques in terms of time taken for confirmation of ETT position. The time taken by each USG technique was also compared with that for auscultation and capnography. The ability of the three USG techniques to identify tracheal placement of ETT was evaluated in all patients.

Material and Methods

Ninety adult American Society of Anesthesiologists (ASA) I/II patients requiring general anaesthesia with tracheal intubation were randomised into three groups (n = 30 each) depending upon the initial USG transducer position used to confirm tracheal placement of ETT: group T (tracheal), group P (pleural) and group D (diaphragm). The time taken for confirmation of tracheal placement of ETT by USG, auscultation and capnography was recorded for each of the groups. Subsequently, USG confirmation of ETT placement was performed with the other two USG techniques in all patients.

Results

The time taken for USG in group T was significantly less (3.8 ± 0.9 s) compared to group P (12.1 ± 1.6 s) and group D (13.8 ± 1.7 s); P < 0.001. USG was significantly faster than both auscultation and capnography in group T (P < 0.001), whereas in group P and group D, USG took longer time compared to auscultation (P = 0.014 and P < 0.001, respectively) but lesser time than capnography (P < 0.001 in both groups).

Conclusion

USG is a rapid technique for identification of ETT placement. All the three USG techniques are reliable in identifying the tracheal placement of ETT.

Volumetric but Not Time Capnography Detects Ventilation/Perfusion Mismatch in Injured Rabbit Lung

Whereas time capnography (Tcap) is routinely displayed during mechanical ventilation, the volumetric representation (Vcap) is seldom used. We compared the diagnostic value of indices derived from Tcap and Vcap following ventilation to perfusion ratio () mismatch subsequent to experimentally induced acute respiratory distress syndrome (ARDS), and alveolar recruitment by elevating the positive end-expiratory pressure (PEEP). Lung injury was induced by iv lipopolysaccharide, whole lung lavage and injurious ventilation in anesthetized, mechanically ventilated rabbits (n = 26). Mainstream Tcap and Vcap were performed to assess normalized phase 2 (Sn2_T, Sn2_V) and phase 3 slopes (Sn3_T, Sn3_V) in the time and volumetric domains. Vcap was also used to estimate Enghoff’s physiological dead space (VD_E). Lung oxygenation index (PaO₂/FiO₂) and intrapulmonary shunt (Qs/Qt) were derived from arterial and central venous blood gas samples. All measurements were made under baseline conditions, and, following lung injury, under moderate (6 cmH₂O) and high PEEP levels (9 cmH₂O). Lung injury deteriorated the PaO₂/FiO₂ (baseline vs. injured 466 ± 10.2 [95% confidence interval] vs. 77.3 ± 17.1 mmHg, p < 0.05) and compromised all mechanical parameters significantly, whereas Tcap parameters exhibited contradictory or inconsistent changes. Conversely, Vcap indices exhibited consistent changes and provided excellent diagnostic value in detecting lung-function deterioration subsequent to lung injury [area under the receiver operating characteristic (ROC) curve of 1.0 ± 0.0, 0.87 ± 0.22 and 0.86 ± 0.22 for VD_E, Sn3_V and Sn3_V/Sn2_V, respectively]. Elevated PEEP increased PaO₂/FiO₂ and decreased Qs/Qt, which was reflected only in the Vcap slope ratio (Sn3_V/Sn2_V, p < 0.05). Our findings demonstrate the limited value of Tcap to detect ventilation to perfusion ratio () mismatch, following severe lung injury. Conversely, indices derived from Vcap proved to be sensitive for detecting lung volume loss and alveolar recruitment. Therefore, promotion of Vcap is of paramount importance as a real-time, non-invasive, bedside monitoring modality to detect the development of and to follow-up the progression of lung injury in a model of ARDS.

Global Capnography Project (GCAP): implementation of capnography in Malawi - an international anaesthesia quality improvement project

The Lancet Commission on Global Surgery emphasised the importance of access to safe anaesthesia care. Capnography is an essential monitor for safe anaesthesia, but is rarely available in low‐income countries. The aim of this study was twofold: to measure the prevalence of capnography in the operating theatres and in intensive care units; and to determine whether its introduction was feasible and could improve the early recognition of critical airway incidents in a low‐income country. This is the first project to do this. Forty capnographs were donated to eight hospitals in Malawi. Thirty‐two anaesthesia providers received a 1‐day capnography training course with pre‐ and post‐course knowledge testing. Providers kept logbooks of capnography use and recorded their responses to abnormal readings. On follow‐up at 6 months, providers completed questionnaires on any significant patient safety incidents identified using capnography. In January 2017, at the commencement of the project, only one operating theatre had a capnograph. Overall, 97% and 100% ‘capnography gaps’ were identified in the theatres and intensive care units, respectively. The mean (SD) scores of our capnography multiple choice questionnaires improved after training from 15.00 (3.16) to 18.70 (0.99), p = < 0.001. The capnography equipment was appropriately robust and performed well. Six months following implementation, 24 (77%) anaesthesia providers reported recognising 44 oesophageal intubations and 28 (90%) believed that capnography had saved lives. This study has shown it is feasible to introduce capnography in a low‐income country, resulting in early recognition of critical airway incidents and ultimately helping to save lives. Building on the experience of the first trial of pulse oximetry implementation in low‐income countries in 2007, we believe this is one of the most important projects in anaesthesia safety in the last decade.

Accuracy of Transcutaneous Carbon Dioxide Levels in Comparison to Arterial Carbon Dioxide Levels in Critically Ill Children

BACKGROUND

Widespread use of transcutaneous P_CO2 (P_tcCO2 ) monitoring is currently limited by concerns many practitioners have regarding accuracy. We compared the accuracy of P_tcCO2 with that of P_aCO2 measurements in critically ill children, and we investigated whether clinical conditions associated with low cardiac output or increased subcutaneous tissue affect this accuracy.

METHODS

We performed a single-center prospective study of critically ill children placed on transcutaneous monitoring.

RESULTS

There were 184 children enrolled with paired P_aCO2 and P_tcCO2 values. Subjects had a median age of 31.8 mo (interquartile range 3.5-123.3 mo). Most children were mechanically ventilated (n = 161, 87.5%), and many had cardiac disease (n = 76, 41.3%). The median P_aCO2 was 44 mm Hg (interquartile range 39-51 mm Hg). The mean bias between P_aCO2 and P_tcCO2 was 0.6 mm Hg with 95% limits of agreement from -13.6 to 14.7 mm Hg. The P_tcCO2 and P_aCO2 were within ±5 mm Hg in 126 (68.5%) measurements. In multivariable modeling, cyanotic heart disease (odds ratio 3.5, 95% CI 1.2-10, P = .02) and monitor number 2 (odds ratio 3.8 95% CI 1.3-10.5, P = .01) remained associated with P_tcCO2 ≥ 5 mm Hg higher than P_aCO2 . Serum lactate, fluid balance, renal failure, obesity, vasoactive-inotrope score, and acyanotic heart disease were not associated with high or low P_tcCO2 values. In 130 children with a second paired P_tcCO2 and P_aCO2 measurement, predicting the second measured P_aCO2 by subtracting the initial observed difference between the P_tcCO2 and P_aCO2 from the subsequent measured P_tcCO2 decreased the mean bias between observed and predicted P_aCO2 to 0.2 mm Hg and the 95% limits of agreement to -9.4 to 9.7 mm Hg.

CONCLUSIONS

P_tcCO2 provides an acceptable estimate of P_aCO2 in many critically ill children, including those with clinical conditions that may be associated with low cardiac output or increased subcutaneous tissue, although it does not perform as well in children with cyanotic heart disease. P_tcCO2 may be a useful adjunct monitoring method, but it cannot reliably replace P_aCO2 measurement.

Paediatric intensive care and neonatal intensive care airway management in the United Kingdom: the PIC-NIC survey

In 2011, the Fourth National Audit Project (NAP4) reported high rates of airway complications in adult intensive care units (ICUs), including death or brain injury, and recommended preparation for airway difficulty, immediately available difficult airway equipment and routine use of waveform capnography monitoring. More than 80% of UK adult intensive care units have subsequently changed practice. Undetected oesophageal intubation has recently been listed as a 'Never Event' in UK practice, with capnography mandated. We investigated whether the NAP4 recommendations have been embedded into paediatric and neonatal intensive care practice by conducting a telephone survey of senior medical or nursing staff in UK paediatric intensive care units (PICUs) and neonatal intensive care units (NICUs). Response rates were 100% for paediatric intensive care units and 90% for neonatal intensive care units. A difficult airway policy existed in 67% of paediatric intensive care units and in 40% of neonatal intensive care units; a pre-intubation checklist was used in 70% of paediatric intensive care units and in 42% of neonatal intensive care units; a difficult intubation trolley was present in 96% of paediatric intensive care units and in 50% of neonatal intensive care units; a videolaryngoscope was available in 55% of paediatric intensive care units and in 29% of neonatal intensive care units; capnography was 'available' in 100% of paediatric intensive care units and in 46% of neonatal intensive care units, and 'always available' in 100% of paediatric intensive care units and in 18% of neonatal intensive care units. Death or serious harm occurring secondary to complications of airway management in the last 5 years was reported in 19% of paediatric intensive care units and in 26% of neonatal intensive care units. We conclude that major gaps in optimal airway management provision exist in UK paediatric intensive care units and especially in UK neonatal intensive care units. Wider implementation of waveform capnography is necessary to ensure compliance with the new 'Never Event' and has the potential to improve airway management.

An appropriate inspiratory flow pattern can enhance CO2 exchange, facilitating protective ventilation of healthy lungs

BACKGROUND

In acute lung injury, CO2 exchange is enhanced by prolonging the volume-weighted mean time for fresh gas to mix with resident alveolar gas, denoted mean distribution time (MDT), and by increasing the flow rate immediately before inspiratory flow interruption, end-inspiratory flow (EIF). The objective was to study these effects in human subjects without lung disease and to analyse the results with respect to lung-protective ventilation of healthy lungs.

METHODS

During preparation for intracranial surgery, the lungs of eight subjects were ventilated with a computer-controlled ventilator, allowing breath-by-breath modification of the inspiratory flow pattern. The durations of inspiration (TI) and postinspiratory pause (TP) were modified, as was the profile of the inspiratory flow wave (i.e. constant, increasing, or decreasing). The single-breath test for CO2 was used to quantify airway dead space (VDaw) and CO2 exchange.

RESULTS

A long MDT and a high EIF augment CO2 elimination by reducing VDaw and promoting mixing of tidal gas with resident alveolar gas. A heat and moisture exchanger had no other effect than enlarging VDaw. A change of TI from 33 to 15% and of TP from 10 to 28%, leaving the time for expiration unchanged, would augment tidal elimination of CO2 by 14%, allowing a 10% lower tidal volume.

CONCLUSIONS

In anaesthetized human subjects without lung disease, CO2 exchange is enhanced by a long MDT and a high EIF. A short TI and a long TP allow significant reduction of tidal volume when lung-protective ventilation is required.

CLINICAL TRIAL REGISTRATION

NCT01686984.

Detection of optimal PEEP for equal distribution of tidal volume by volumetric capnography and electrical impedance tomography during decreasing levels of PEEP in post cardiac-surgery patients

Background

Homogeneous ventilation is important for prevention of ventilator-induced lung injury. Electrical impedance tomography (EIT) has been used to identify optimal PEEP by detection of homogenous ventilation in non-dependent and dependent lung regions. We aimed to compare the ability of volumetric capnography and EIT in detecting homogenous ventilation between these lung regions.

Methods

Fifteen mechanically-ventilated patients after cardiac surgery were studied. Ventilator settings were adjusted to volume-controlled mode with a fixed tidal volume (Vt) of 6–8 ml kg⁻¹ predicted body weight. Different PEEP levels were applied (14 to 0 cm H₂O, in steps of 2 cm H₂O) and blood gases, Vcap and EIT were measured.

Results

Tidal impedance variation of the non-dependent region was highest at 6 cm H₂O PEEP, and decreased significantly at 14 cm H₂O PEEP indicating decrease in the fraction of Vt in this region. At 12 cm H₂O PEEP, homogenous ventilation was seen between both lung regions. Bohr and Enghoff dead space calculations decreased from a PEEP of 10 cm H₂O. Alveolar dead space divided by alveolar Vt decreased at PEEP levels ≤6 cm H₂O. The normalized slope of phase III significantly changed at PEEP levels ≤4 cm H₂O. Airway dead space was higher at higher PEEP levels and decreased at the lower PEEP levels.

Conclusions

In postoperative cardiac patients, calculated dead space agreed well with EIT to detect the optimal PEEP for an equal distribution of inspired volume, amongst non-dependent and dependent lung regions. Airway dead space reduces at decreasing PEEP levels.

Capnogram slope and ventilation dead space parameters: comparison of mainstream and sidestream techniques

BACKGROUND

Capnography may provide useful non-invasive bedside information concerning heterogeneity in lung ventilation, ventilation-perfusion mismatching and metabolic status. Although the capnogram may be recorded by mainstream and sidestream techniques, the capnogram indices furnished by these approaches have not previously been compared systematically.

METHODS

Simultaneous mainstream and sidestream time and volumetric capnography was performed in anaesthetized, mechanically ventilated patients undergoing elective heart surgery. Time capnography was used to assess the phase II (SII,T) and III slopes (SIII,T). The volumetric method was applied to estimate phase II (SII,V) and III slopes (SIII,V), together with the dead space values according to the Fowler (VDF), Bohr (VDB), and Enghoff (VDE) methods and the volume of CO2 eliminated per breath ([Formula: see text]). The partial pressure of end-tidal CO2 ([Formula: see text]) was registered.

RESULTS

Excellent correlation and good agreement were observed in SIII,T measured by the mainstream and sidestream techniques [ratio=1.05 (sem 0.16), R(2)=0.92, P<0.0001]. Although the sidestream technique significantly underestimated [Formula: see text] and overestimated SIII,V [1.32 (0.28), R(2)=0.93, P<0.0001], VDF, VDB, and VDE, the agreement between the mainstream and sidestream techniques in the difference between VDE and VDB, reflecting the intrapulmonary shunt, was excellent [0.97 (0.004), R(2)=0.92, P<0.0001]. The [Formula: see text] exhibited good correlation and mild differences between the mainstream and sidestream approaches [0.025 (0.005) kPa].

CONCLUSIONS

Sidestream capnography provides adequate quantitative bedside information about uneven alveolar emptying and ventilation-perfusion mismatching, because it allows reliable assessments of the phase III slope, [Formula: see text] and intrapulmonary shunt. Reliable measurement of volumetric parameters (phase II slope, dead spaces, and eliminated CO2 volumes) requires the application of a mainstream device.

Correlation between minute carbon dioxide elimination and pulmonary blood flow in single-ventricle patients after stage 1 palliation and 2-ventricle patients with intracardiac shunts: A pilot study

BACKGROUND

Assessment of pulmonary blood flow and cardiac output is critical in the postoperative management of patients with single-ventricle physiology or 2-ventricle physiology with intracardiac shunting. Currently, such hemodynamic data are only obtainable by invasive procedures, such as cardiac catheterization or the use of a pulmonary artery catheter. Ready availability of such information, especially if attainable noninvasively, could be a valuable addition to postoperative management.

AIMS

The aim of this study was to assess the correlation between volume of CO₂ elimination obtained by volumetric capnography and pulmonary blood flow in pediatric patients with single-ventricle physiology after stage 1 palliation as well as in patients with other cardiac lesions associated with intracardiac shunting.

METHODS

This prospective cohort study included children with congenital or acquired heart disease who underwent cardiac catheterization as part of clinical care. Cardiac output, pulmonary blood flow, and volume of CO₂ elimination were simultaneously collected. Spearman's rank correlation coefficients were used to assess correlation between measurements after controlling for minute ventilation.

RESULTS

Thirty-five patients were enrolled and divided into 3 groups. Group 1 (n = 8) included single-ventricle patients after stage 1 palliation. Group 2 (n = 10) patients had structural heart disease with 2 ventricles and intracardiac shunting. Group 3 (n = 17) had structurally normal hearts. Among Group 1 patients, the correlation coefficients (R² ) between volume of CO₂ elimination and pulmonary blood flow and volume of CO₂ elimination and cardiac output were 0.60 (P = .02) 95% CI [0.01-0.79] and 0.29 (P = .74) 95% CI [-0.91 - 0.86], respectively. In patients with 2 ventricles associated with intracardiac shunts (Group 2), the correlation coefficients between volume of CO₂ elimination and pulmonary blood flow and volume of CO₂ elimination and cardiac output were 0.86 (P = .001) 95% CI [0.53 - 0.97] and 0.73 (P = .001) 95% CI [0.29 - 0.95], respectively. Among Group 3 patients, the correlation coefficient between volume of CO₂ elimination and pulmonary blood flow was 0.66 (P = .038) 95% CI [0.29 - 0.87].

CONCLUSION

Volume of CO₂ elimination may be a surrogate marker of pulmonary blood flow in single-ventricle patients and patients with biventricular physiology with intracardiac shunting. Also, among patients with normal cardiac anatomy, volume of CO₂ elimination may be a marker of cardiac output.

Accuracy of Real-time Intratracheal Bedside Ultrasonography and Waveform Capnography for Confirmation of Intubation in Multiple Trauma Patients

Background:

A secure airway and effective ventilation are key components of advanced life support, and misplacement of endotracheal tube (ETT) can lead to morbidity in multiple trauma patients. The purpose of this study was to investigate the accuracy of ultrasound in diagnosis of direction for tracheal intubation.

Materials and Methods:

This descriptive-analytical study was conducted on 100 traumatic patients requiring intubation in 2016 in the Emergency Department of Al-Zahra and Kashani Medical Education Centers in Isfahan. Surface probe was placed transversally in the front of the neck at the top of the suprasternal notch, and the position of trachea was specified by front of comet-tail artifact which is the contour between hyperechoic air–mucosa (A–M) and a posterior reverberation artifact. Intubation accuracy by capnography was investigated, and the results were recorded in each patient's profile. Tracheal sonography was done during placement, or as soon as, the ETT has been embedded. The scanning time was minimized and it was carried out in total time of 10 s.

Results:

The diagnosis of intubation accuracy indicated that it was successful in 94 individuals (94%) and unsuccessful in 6 ones (6%). Intubation accuracy in 93 people (93%) was confirmed, and inaccuracy of intubation in 7 people (7%) was diagnosed. Ultrasound sensitivity in diagnosis of intubation accuracy was 97.9% (92.94) with 83.3% (5.6%) specificity. The positive and negative predictive values were 98.9% (92.93) and 71.4% (5.7%) respectively.

Conclusion:

Ultrasound method has high sensitivity and specificity to determine the correct placement of the tracheal tube, and it can be implemented as a reliable method given the acceptable positive and negative predictive values.

Respiratory Diagnostic Tools in Neuromuscular Disease

Children with neuromuscular disease (NMD) are at risk of acquiring respiratory complications. Both clinical assessments and respiratory diagnostic tests are important to optimize the respiratory health and care of such children. The following respiratory diagnostic tools and their utility for evaluating children with NMD are discussed in this article: lung function testing (spirometry and lung volumes), peak cough flow (PCF), respiratory muscle strength testing, oximetry, capnography, and polysomnography.

Exploring the Waveform Characteristics of Tidal Breathing Carbon Dioxide, Measured Using the N-Tidal C Device in Different Breathing Conditions (The General Breathing Record Study): Protocol for an Observational, Longitudinal Study

BACKGROUND

In an increasingly comorbid population, there are significant challenges to diagnosing the cause of breathlessness, and once diagnosed, considerable difficulty in detecting deterioration early enough to provide effective intervention. The burden of the breathless patient on the health care economy is substantial, with asthma, chronic heart failure, and pneumonia affecting over 6 million people in the United Kingdom alone. Furthermore, these patients often have more than one contributory factor to their breathlessness symptoms, with conditions such as dysfunctional breathing pattern disorders-an under-recognized component. Current methods of diagnosing and monitoring breathless conditions can be extensive and difficult to perform. As a consequence, home monitoring is poorly complied with. In contrast, capnography (the measurement of tidal breath carbon dioxide) is performed during normal breathing. There is a need for a simple, easy-to-use, personal device that can aid in the diagnosis and monitoring of respiratory and cardiac causes of breathlessness.

OBJECTIVE

The aim of this study was to explore the use of a new, handheld capnometer (called the N-Tidal C) in different conditions that cause breathlessness. We will study whether the tidal breath carbon dioxide (TBCO₂) waveform, as measured by the N-Tidal C, has different characteristics in a range of respiratory and cardiac conditions.

METHODS

We will perform a longitudinal, observational study of the TBCO₂ waveform (capnogram) as measured by the N-Tidal C capnometer. Participants with a confirmed diagnosis of asthma, breathing pattern disorders, chronic heart failure, motor neurone disease, pneumonia, as well as volunteers with no history of lung disease will be asked to provide twice daily, 75-second TBCO₂ collection via the N-Tidal C device for 6 months duration. The collated capnograms will be correlated with the underlying diagnosis and disease state (stable or exacerbation) to determine if there are different TBCO₂ characteristics that can distinguish different respiratory and cardiac causes of breathlessness.

RESULTS

This study's recruitment is ongoing. It is anticipated that the results will be available in late 2018.

CONCLUSIONS

The General Breathing Record Study will provide an evaluation of the use of capnography as a diagnostic and home-monitoring tool for various diseases.

REGISTERED REPORT IDENTIFIER

RR1-10.2196/9767.

Estimating Arterial Partial Pressure of Carbon Dioxide in Ventilated Patients: How Valid Are Surrogate Measures?

The arterial partial pressure of carbon dioxide (Pa_CO2) is an important parameter in critically ill, mechanically ventilated patients. To limit invasive procedures or for more continuous monitoring of Pa_CO2, clinicians often rely on venous blood gases, capnography, or transcutaneous monitoring. Each of these has advantages and limitations. Central venous Pco₂ allows accurate estimation of Pa_CO2, differing from it by an amount described by the Fick principle. As long as cardiac output is relatively normal, central venous Pco₂ exceeds the arterial value by approximately 4 mm Hg. In contrast, peripheral venous Pco₂ is a poor predictor of Pa_CO2, and we do not recommend using peripheral venous Pco₂ in this manner. Capnography offers measurement of the end-tidal Pco₂ (Pet_CO2), a value that is close to Pa_CO2 when the lung is healthy. It has the advantage of being noninvasive and continuously available. In mechanically ventilated patients with lung disease, however, Pet_CO2 often differs from Pa_CO2, sometimes by a large degree, often seriously underestimating the arterial value. Dependence of Pet_CO2 on alveolar dead space and ventilator expiratory time limits its value to predict Pa_CO2. When lung function or ventilator settings change, Pet_CO2 and Pa_CO2 can vary in different directions, producing further uncertainty. Transcutaneous Pco₂ measurement has become practical and reliable. It is promising for judging steady state values for Pa_CO2 unless there is overt vasoconstriction of the skin. Moreover, it can be useful in conditions where capnography fails (high-frequency ventilation) or where arterial blood gas analysis is burdensome (clinic or home management of mechanical ventilation).