Using the features of the time and volumetric capnogram for classification and prediction

Quantitative features derived from the time-based and volumetric capnogram such as respiratory rate, end-tidal PCO₂, dead space, carbon dioxide production, and qualitative features such as the shape of capnogram are clinical metrics recognized as important for assessing respiratory function. Researchers are increasingly exploring these and other known physiologically relevant quantitative features, as well as new features derived from the time and volumetric capnogram or transformations of these waveforms, for: (a) real-time waveform classification/anomaly detection, (b) classification of a candidate capnogram into one of several disease classes, (c) estimation of the value of an inaccessible or invasively determined physiologic parameter, (d) prediction of the presence or absence of disease condition, (e) guiding the administration of therapy, and (f) prediction of the likely future morbidity or mortality of a patient with a presenting condition. The work to date with respect to these applications will be reviewed, the underlying algorithms and performance highlighted, and opportunities for the future noted.

Journal of Clinical Monitoring and Computing 2015 end of year summary: respiration

This paper reviews 17 papers or commentaries published in Journal of Clinical Monitoring and Computing in 2015, within the field of respiration. Papers were published covering monitoring and training of breathing, monitoring of gas exchange, hypoxemia and acid-base, and CO2 monitoring.

Transcutaneous PTCCO2 measurement in combination with arterial blood gas analysis provides superior accuracy and reliability in ICU patients

Hyper or hypoventilation may have serious clinical consequences in critically ill patients and should be generally avoided, especially in neurosurgical patients. Therefore, monitoring of carbon dioxide partial pressure by intermittent arterial blood gas analysis (PaCO₂) has become standard in intensive care units (ICUs). However, several additional methods are available to determine PCO₂ including end-tidal (PETCO₂) and transcutaneous (PTCCO₂) measurements. The aim of this study was to compare the accuracy and reliability of different methods to determine PCO₂ in mechanically ventilated patients on ICU. After approval of the local ethics committee PCO₂ was determined in n = 32 ICU consecutive patients requiring mechanical ventilation: (1) arterial PaCO₂ blood gas analysis with Radiometer ABL 625 (ABL; gold standard), (2) arterial PaCO₂ analysis with Immediate Response Mobile Analyzer (IRMA), (3) end-tidal PETCO₂ by a Propaq 106 EL monitor and (4) transcutaneous PTCCO₂ determination by a Tina TCM4. Bland-Altman method was used for statistical analysis; p < 0.05 was considered statistically significant. Statistical analysis revealed good correlation between PaCO₂ by IRMA and ABL (R² = 0.766; p < 0.01) as well as between PTCCO₂ and ABL (R² = 0.619; p < 0.01), whereas correlation between PETCO₂ and ABL was weaker (R² = 0.405; p < 0.01). Bland-Altman analysis revealed a bias and precision of 2.0 ± 3.7 mmHg for the IRMA, 2.2 ± 5.7 mmHg for transcutaneous, and -5.5 ± 5.6 mmHg for end-tidal measurement. Arterial CO₂ partial pressure by IRMA (PaCO₂) and PTCCO₂ provided greater accuracy compared to the reference measurement (ABL) than the end-tidal CO₂ measurements in critically ill in mechanically ventilated patients patients.

A mainstream monitoring system for respiratory CO2 concentration and gasflow

Continuous respiratory gas monitoring is an important tool for clinical monitoring. In particular, measurement of respiratory [Formula: see text] concentration and gasflow can reflect the status of a patient by providing parameters such as volume of carbon dioxide, end-tidal [Formula: see text] respiratory rate and alveolar deadspace. However, in the majority of previous work, [Formula: see text] concentration and gasflow have been studied separately. This study focuses on a mainstream system which simultaneously measures respiratory [Formula: see text] concentration and gasflow at the same location, allowing for volumetric capnography to be implemented. A non-dispersive infrared monitor is used to measure [Formula: see text] concentration and a differential pressure sensor is used to measure gasflow. In developing this new device, we designed a custom airway adapter which can be placed in line with the breathing circuit and accurately monitor relevant respiratory parameters. Because the airway adapter is used both for capnography and gasflow, our system reduces mechanical deadspace. The finite element method was used to design the airway adapter which can provide a strong differential pressure while reducing airway resistance. Statistical analysis using the coefficient of variation was performed to find the optimal driving voltage of the pressure transducer. Calibration between variations and flows was used to avoid pressure signal drift. We carried out targeted experiments using the proposed device and confirmed that the device can produce stable signals.

Availability and use of capnography for in-hospital cardiac arrests in the United Kingdom

BACKGROUND

Airway complications occur more frequently outside the operating theatre and in emergency situations. Capnography remains the gold standard for confirming correct endotracheal tube placement, retaining high sensitivity and specificity in cardiac arrest. The 2010 European Resuscitation Council guidelines for adult advanced life support recommended waveform capnography in this setting. We investigated current UK practice relating to the availability and use of this technology during cardiac arrest.

METHODS

Between June and November 2014, a study was conducted of all UK acute hospitals with both a level three adult intensive care unit (ICU) and an emergency department (ED). A telephone questionnaire was administered examining intubation practice and utilisation of capnography within the ED, ICU and general wards.

RESULTS

Two hundred and eleven hospitals met the inclusion criteria. The response rate was 100%. Arrests were mainly attended by anaesthesia (48%) and ICU physicians (38%) of registrar grade (56%). The ability to measure end tidal carbon dioxide (ETCO2) was available in all but 4 EDs; most used in waveform devices. Most ICUs were similar. However, in 67% of hospitals surveyed, it was not possible to measure ETCO2 in general wards. Where available, 87% used capnography to confirm ETT placement with less than 50% using ETCO2 to determine CPR effectiveness and 8% to prognosticate.

CONCLUSIONS

We believe this is the first study of its kind to fully investigate the availability and use of capnography during cardiac arrest throughout the hospital. Whilst equipment provision appears adequate in critical care areas, it is insufficient in general wards.

A Review of Carbon Dioxide Monitoring During Adult Cardiopulmonary Resuscitation

Although high quality cardiopulmonary resuscitation is one of the most significant factors related to favourable outcome, its quality depends on many components, such as airway management, compression depth and chest recoil, hands-off time, and early defibrillation. The most common way of controlling the resuscitation efforts is monitoring of end-tidal carbon dioxide. The International Liaison Committee on Resuscitation suggests this method both for in-hospital and out-of-hospital cardiac arrest. However, despite the abundant human and animal studies supporting the usefulness of end-tidal carbon dioxide, its optimal values during cardiopulmonary resuscitation remain controversial. In this review, the advantages and effectiveness of end-tidal carbon dioxide during cardiopulmonary resuscitation are discussed and specific target values are suggested based on the available literature.

Initial end-tidal carbon dioxide as a prognostic indicator for inpatient PEA arrest

AIM

Investigate the relationship of initial PetCO2 values of patients during inpatient pulseless electrical activity (PEA) cardiopulmonary arrest with return of spontaneous circulation (ROSC) and survival to discharge.

METHODS

This study was performed in two urban, academic inpatient hospitals. Patients were enrolled from July 2009 to July 2013. A comprehensive database of all inpatient resuscitative events is maintained at these institutions, including demographic, clinical, and outcomes data. Arrests are stratified by primary etiology of arrest using a priori criteria. Inpatients with PEA arrest for whom recorded PetCO2 was available were included in the analysis. Capnography data obtained after ROSC and/or more than 10 min after initiation of CPR were excluded. Multivariable logistic regression was used to explore the association between initial PetCO2 >20 mmHg and both ROSC and survival-to-discharge.

RESULTS

A total of 50 patients with PEA arrest and pre-ROSC capnography were analyzed. CPR continued an average of 11.8 min after initial PetCO2 was recorded confirming absence of ROSC at time of measurement. Initial PetCO2 was higher in patients with versus without eventual ROSC (25.3 ± 14.4 mmHg versus 13.4 ± 6.9 mmHg, P = 0.003). After adjusting for age, gender, and arrest location (ICU versus non-ICU), initial PetCO2 >20 mmHg was associated with increased likelihood of ROSC (adjusted OR 4.8, 95% CI 1.2-19.2, P = 0.028). Initial PetCO2 was not significantly associated with survival-to-discharge (P = 0.251).

CONCLUSIONS

Initial PetCO2 >20 mmHg during CPR was associated with ROSC but not survival-to-discharge among inpatient PEA arrest victims. This analysis is limited by relatively small sample size.

Reliability and Validity of the Iranian Version of Nijmegen Questionnaire in Iranians with Asthma

BACKGROUND

The aim of this study was to assess the validity and reliability of Nijmegen questionnaire (NQ) translated to Farsi for diagnosis of the hyperventilation syndrome (HVS) in patients with asthma.

MATERIALS AND METHODS

The original version of NQ was translated to Farsi and then back-translated to English again to assess its agreement with the original version. To determine its cultural adaptation, a pilot study was carried out. The mean score of the questionnaire and the mean pressure of end tidal carbon dioxide (PETCO2) were compared in 100 asthmatic patients to determine the validity of the questionnaire. For reliability, 52 out of 100 patients randomly filled out the questionnaire with an interval of 5 to 10 days. Internal consistency and content validity of the questionnaire were assessed by Cronbach's alpha coefficient and by calculating floor and ceiling effects respectively. The exploratory factor analysis was used to assess the factor structure.

RESULTS

There was a significant inverse correlation between NQ scores and PETCO2 (P=-0.783). Cronbach's alpha coefficient was greater than 0.7, indicating good internal consistency of the questionnaire (P=0.702). The questionnaire had a good stability in an interval of 5 to 10 days (P=0.826). The NQ had no floor and ceiling effect. and also factor analysis of 16 scales showed that this questionnaire has a five-factor structure, which can describe 55% of data variance.

CONCLUSION

The Iranian version of the Nijmegen questionnaire is a valid and reliable tool for detection of patients with HVS. In addition, the questionnaire can be used to evaluate the condition of respiratory function in people with asthma.

Sedation-related complications in gastrointestinal endoscopy

Defining the risk of procedural sedation for gastrointestinal endoscopic procedures remains a vexing challenge. The definitions as to what constitutes a cardiopulmonary unplanned event are beginning to take focus but the existing literature is an amalgam of various definitions and subjective outcomes, providing a challenge to patient, practitioner, and researcher. Gastrointestinal endoscopy when undertaken by trained personnel after the appropriate preprocedural evaluation and in the right setting is a safe experience. However, significant challenges exist in further quantifying the sedation risks to patients, optimizing physiologic monitoring, and sublimating the pharmacoeconomic and regulatory embroglios that limit the scope of practice and the quality of services delivered to patients.

Arterial and end-tidal carbon dioxide difference in pediatric intensive care

Background and Aim:

Arterial carbon dioxide tension (PaCO₂) is considered the gold standard for scrupulous monitoring in pediatric intensive care unit (PICU), but it is invasive, laborious, expensive, and intermittent. The study aims to explore when we can use end-tidal carbon dioxide tension (P_ETCO₂) as a reliable, continuous, and noninvasive monitor of arterial CO₂

Materials and Methods:

Concurrent P_ETCO₂, fraction of inspired oxygen, PaCO₂, and arterial oxygen tension values of clinically stable children on mechanical ventilation were recorded. Children with extra-pulmonary ventriculoatrial shunts were excluded. The P_ETCO₂ and PaCO₂ difference and its variability and reproducibility were studied.

Results:

A total of 624 concurrent readings were obtained from 105 children (mean age [SD] 5.53 [5.43] years) requiring invasive bi-level positive airway pressure ventilation in the PICU. All had continuous P_ETCO₂ monitoring and an arterial line for blood gas measurement. The mean (SD) number of concurrent readings obtained from each child, 4-6 h apart was 6.0 (4.05). The P_ETCO₂ values were higher than PaCO₂ in 142 observations (22.7%). The PaCO₂–P_ETCO₂ difference was individual admission specific (ANOVA, P < 0.001). The PaCO₂–P_ETCO₂ difference correlated positively with the alveolar-arterial oxygen tension [P(A-a)O₂] difference (ρ = 0.381 P < 0.0001). There was a fixed bias between the P_ETCO₂ and PaCO₂ measuring methods, difference +0.66 KPa (95% confidence interval: +0.57 to +0.76).

Conclusions:

The PaCO₂–P_ETCO₂ difference was individual specific. It was not affected by the primary disorder leading to the ventilation.

Capnography during cardiopulmonary resuscitation: Current evidence and future directions

Capnography continues to be an important tool in measuring expired carbon dioxide (CO₂). Most recent Advanced Cardiac Life Support (ACLS) guidelines now recommend using capnography to ascertain the effectiveness of chest compressions and duration of cardiopulmonary resuscitation (CPR). Based on an extensive review of available published literature, we selected all available peer-reviewed research investigations and case reports. Available evidence suggests that there is significant correlation between partial pressure of end-tidal CO₂ (PETCO₂) and cardiac output that can indicate the return of spontaneous circulation (ROSC). Additional evidence favoring the use of capnography during CPR includes definitive proof of correct placement of the endotracheal tube and possible prediction of patient survival following cardiac arrest, although the latter will require further investigations. There is emerging evidence that PETCO₂ values can guide the initiation of extracorporeal life support (ECLS) in refractory cardiac arrest (RCA). There is also increasing recognition of the value of capnography in intensive care settings in intubated patients. Future directions include determining the outcomes based on capnography waveforms PETCO₂ values and determining a reasonable duration of CPR. In the future, given increasing use of capnography during CPR large databases can be analyzed to predict outcomes.

The usefulness of end-tidal carbon dioxide monitoring during apnea test in brain-dead patients

Background

The apnea test (AT) is essential to confirming the diagnosis of brain death, but critical complications can occur if the AT is maintained over a long period. To minimize the AT period, we used end-tidal carbon dioxide (ETCO₂) monitoring because ETCO₂ is closely correlated with partial pressure of arterial carbon dioxide (PaCO₂). The aim of the present study is to evaluate the usefulness of ETCO₂ monitoring during apnea testing.

Methods

We reviewed 61 patients who were pronounced brain dead at our hospital from July 2009 to December 2012. The subjects were divided into two groups: the N-group, in which capnography was not used, and the C-group, in which capnography was used to monitor ETCO₂. In the C-group, whenever arterial blood was sampled, the PaCO₂ - ETCO₂ gradients were calculated and the ventilator setting adjusted to maintain normocapnia prior to apnea testing.

Results

Twenty-eight subjects in the N-group and twenty-nine subjects in the C-group were included. The gender ratio, age, and cause of brain death were not different between the two groups. Prior to the AT, the normocapnia ratio was higher in the C-group than in the N-group. During the AT, the total test period was shorter in the C-group. Moreover, systolic blood pressure increased in the C-group and decreased in the N-group during apnea testing.

Conclusions

ETCO₂ monitoring during AT allows the PaCO₂ level to be predicted, which reduces the duration of the test and stabilizes systolic blood pressure. Thus, with ETCO₂ monitoring, the AT can be fast and safe.

A review of carbon dioxide monitoring in preterm newborns in the delivery room

INTRODUCTION

The physiologic adaptation to extra uterine life during the immediate neonatal period is unique. Many newborns require assistance in this adaptive process. Recent evidence now supports titrating oxygen to guide resuscitation but no guidance is provided on utilizing exhaled CO2 measurements.

AIM

To review the current evidence relating to the use of CO2 monitoring in preterm newborns in the delivery room.

METHODS

Search was performed using the Cochrane Central Register of Controlled Trials, MEDLINE (1966-2014) and PREMEDLINE, EMBASE (1980-2014), CINAHL (1982-2014), Web of Science (1975-2014) and the Oxford Database of Perinatal Trials.

RESULTS

The search revealed 21 articles relating to CO2 detection, either quantitative or qualitative, in the newborn infant. The majority of these were observational studies, eight relating to CO2 detection as a means of confirming correct endotracheal tube placement in the newborn infant. The other indication is for mask ventilation, and there is one randomized control trial and four observational studies of CO2 detection during mask ventilation. The overall recommendation for CO2 detection for both clinical uses in the delivery suite is level B.

DISCUSSION

CO2 detection may be of particular benefit for preterm infants in the delivery suite. However there is a need for further research into CO2 detection, in particular capnography, as a means of confirming effective PPV in neonatal resuscitation.

Correlation of end tidal and arterial carbon dioxide levels in critically Ill neonates and children

AIM OF THE STUDY

End tidal carbon dioxide (EtCO2) monitoring is considered to reflect real-time estimation of partial pressure of carbon dioxide in arterial blood (PaCO2) noninvasively. However, knowledge about its relationship with PaCO2 in critically ill pediatric and neonatal patients is limited. The primary objective was to evaluate predictive capability of end tidal carbon dioxide monitoring and secondary objective was to determine the influence of severity of lung disease on EtCO2 and PaCO2 relationship.

MATERIALS AND METHODS

This was a prospective, nonrandomized, consecutive enrollment study carried out in neonatal and pediatric intensive care units of a tertiary care children hospital. It was conducted in 66 neonates and 35 children receiving mechanical ventilation. Severity of lung disease was estimated by ventilation index and PaO2/FiO2 (P/F) ratio. Simultaneous recording of EtCO2 and PaCO2 levels was done and data were analyzed for correlation and agreement.

RESULTS

In neonates, 150 EtCO2 and PaCO2 pairs were recorded. The mean weight ± SD of patients was 2.1 ± 0.63 kg. PaCO2 had a positive correlation with EtCO2 (r = 0.836, 95% CI = 0.78-0.88). P/F ratio <200 adversely affected relationship. In infants and children, 96 pairs were recorded. Mean age ± SD of patients was 4.20 ± 4.92 years and mean weight ± SD was 13.1 ± 9.49 kg. PaCO2 had an excellent correlation with EtCO2 (r = 0.914, 95% CI = 0.87 and 0.94). P/F ratio <200 adversely affected relationship.

CONCLUSION

EtCO2 monitoring displayed a good validity to predict PaCO2. Correlation was affected by low P/F ratio (<200); hence, it is recommended that blood gases be measured in these patients until such time that a good relation can be established between end tidal and arterial CO2 values.

Experiences with capnography in acute care settings: a mixed-methods analysis of clinical staff

PURPOSE

Although capnography is being incorporated into clinical guidelines, it is not used to its full potential. We investigated reasons for limited implementation of capnography in acute care areas and explored facilitators and barriers to its implementation.

METHODS

A purposeful sample of physicians and nurses in emergency departments and intensive care units participated in semistructured interviews. Grounded theory, iterative data analysis, and the constant comparative method were used to analyze the data to inductively generate ideas and build theories.

RESULTS

Nineteen providers were interviewed from 5 hospitals. Six themes were identified: variability in use of capnography among acute care units, availability and accessibility of capnography equipment, the evidence behind capnography use, the impact of capnography on patient care, personal experiences impacting use of capnography, and variable knowledge about capnography. Barriers and facilitators to use were found within each theme.

CONCLUSIONS

We observed varied responsiveness to capnography and identified factors that work to foster or discourage its use. These data can guide future implementation strategies. A deliberate strategy to foster utilization, mitigate barriers, and broadly accelerate implementation has the potential to profoundly impact use of capnography in acute care areas with the goal of improving patient care.

Capnography in patients with severe neurological impairment

Respiratory disease is a common reason for hospitalization and mortality in persons with severe intellectual and developmental disability. Capnography is the measurement and numerical display of end-tidal carbon dioxide (EtCO2). This was a prospective, case controlled, cross sectional study to assess differences of baseline EtCO2 values between neurologically impaired patients and healthy individuals. 86 neurologically impaired patients were evaluated in the study group. Their mean age ± SD was 25.65 ± 10.48 years with 41% males. 53 healthy children and young adults were evaluated in the control group. Their mean age ± SD was 21.95 ± 10.38 years with 54.7% males. Patients with severe neurological impairment had higher baseline EtCO2 values than healthy individuals. Kyphoscoliosis and the use of antipsychotic drugs were the major factors to increase EtCO2 levels. Knowing the patient's baseline EtCO2 value, as well as baseline oximetry, could guide treatment decisions, when assessing the patient's oxygenation and ventilation during acute respiratory illness, and can potentially prevent unnecessary laboratory and imaging investigations as well as over treatment. Future research can shed light on the utility of capnometry and clinical implications of higher baseline EtCO2 values among neurologically impaired patients.

Lung mechanical changes following bronchoaspiration in a porcine model: differentiation of direct and indirect mechanisms

Bronchoaspiration results in local deterioration of lung function through direct damage and/or indirect systemic effects related to neurohumoral pathways. We distinguished these effects by selectively intubating the two main bronchi in pigs while a PEEP of 4 or 10cm H2O was maintained. Gastric juice was instilled only into the right lung. Lung mechanical and ventilation defects were assessed by measuring unilateral pulmonary input impedance (ZL,s) and the third phase slope of the capnogram (SIII) for each lung side separately before the aspiration and for 120min thereafter. Marked transient elevations in ZL,s parameters and SIII were observed in the affected lung after aspiration. Elevating PEEP did not affect these responses in the ZL,s parameters, whereas it prevented the SIII increases. None of these indices changed in the intact left lung. These findings furnish evidence of the predominance of the local direct damage over the indirect systemic effects in the development of the deterioration of lung function, and demonstrate the benefit of an initially elevated PEEP following aspiration.

[Usefulness of bedside ultrasound compared to capnography and X-ray for tracheal intubation]

OBJECTIVES

The aim of this study was to assess the usefulness of bedside ultrasound compared to capnography and X-ray for endotracheal intubation in children and newborns.

MATERIALS AND METHODS

Hemodynamically stable children intubated in pedriatric and neonatal intensive care unit were included. Endotracheal tube insertion was checked after every intubation attempt by tracheal ultrasound and capnography simultaneously. The endotracheal tube insertion depth was then checked by assesment of lung sliding by thoracic ultrasound. Thereafter, Chest X-ray was performed and interpreted as usual. Time to perform each technique was recorded.

RESULTS

The study included 31 intubations in 26 patients (15 in PICU and 16 in NICU). There were no statistically significant differences between tracheal ultrasound and capnography or between thoracic ultrasound and x-ray in identifying the correct endotracheal intubation and assessment of endotracheal tube insertion depth, respectively. Sensibility and specificity of ultrasound compared to capnography was 92% and 100%, and 100% and 75% compared to X-ray. Ultrasound was significantly slower compared to capnography [12 (4-16) vs 6 (3-12) seconds; P<.001] and significantly quicker compared to X-ray [0.22 (0.17-0.40) vs. 20 (17-25) minutes, P<.001].

CONCLUSIONS

Ultrasound appears to be as effective as capnography, although slower, for identifying endotracheal intubation. Ultrasound may be useful in clinical situations, such as cardiopulmonary resuscitation where capnography is less reliable. Ultrasound is as effective and quicker than X-ray for assessment of endotracheal tube insertion depth, and it may contribute to decrease the routine use of X-ray after tracheal intubation.

Esformes J. Breathing pattern disorders and functional movement

STUDY DESIGN

Experimental design.

BACKGROUND

Normal breathing mechanics play a key role in posture and spinal stabilization. Breathing Pattern Disorders (BPD) have been shown to contribute to pain and motor control deficits, which can result in dysfunctional movement patterns. The Functional Movement Screen™ (FMS™) has been shown to accurately predict injury in individuals who demonstrate poor movement patterns. The role BPD play on functional movement is not well established. Furthermore, there is currently no single test to clinically diagnose BPD. A variety of methods are used, but correlations between them are poor.

PURPOSE

To examine the relationship between BPD and functional movement and identify correlations between different measures of BPD.

METHODS

Breathing was assessed in 34 healthy individuals using a multi-dimensional approach that included biomechanical, biochemical, breathing related symptoms, and breathing functionality measures. Movement was assessed using the FMS™. Analysis, involving independent t-tests and Pearson correlation were performed to identify associations between measures.

RESULTS

Individuals who exhibited biochemical and biomechanical signs of BPD were significantly more likely to score poorly on the FMS™. These studied measures of BPD correlated highly with each other.

CONCLUSION

These results demonstrate the importance of diaphragmatic breathing on functional movement. Inefficient breathing could result in muscular imbalance, motor control alterations, and physiological adaptations that are capable of modifying movement. These findings provide evidence for improved breathing evaluations by clinicians.

LEVEL OF EVIDENCE

2B.

Unidirectional valve malfunction by the breakage or malposition of disc - two cases report -

Malfunction of the unidirectional valve in a breathing circuit system may cause hypercapnia from the rebreathing of expired gas, ventilation failure, and barotrauma. Capnography is a useful method for monitoring the integrity of the unidirectional valve. We experienced two cases of malfunction of a unidirectional valve which caused leakage and reverse flow, diagnosed early as a change of the capnographic waveform. One case was caused by expiratory unidirectional valve breakage. The other was caused by an incorrectly-assembled inspiratory unidirectional valve.

[Nocturnal monitoring of home non-invasive ventilation: Contribution of simple tools such as pulse-oximetry, capnography, built-in ventilator software and autonomic markers of sleep fragmentation]

Complex respiratory events, which may have a detrimental effect on both quality of sleep and control of nocturnal hypoventilation, occur during sleep in patients treated by non-invasive ventilation (NIV). Among these events are patient-ventilator asynchrony, increases in upper airway resistance with or without increased respiratory drive, and leaks. Detection of these events is important in order to select the most appropriate ventilator settings and interface. Simple tools can provide important information when monitoring NIV. Pulse-oximetry is important to ensure that an adequate SpO2 is provided, and to detect either prolonged or short and recurrent desaturations. However, the specificity of pulse-oximetry tracings under NIV is low. Transcutaneous capnography discriminates between hypoxemia related to V/Q mismatch and hypoventilation, documents correction of nocturnal hypoventilation, and may detect ventilator-induced hyperventilation, a possible cause for central apnea/hypopnea and glottic closure. Data provided by ventilator software helps the clinician by estimating ventilation, tidal volume, leaks, rate of inspiratory or expiratory triggering by the patient, although further validation of these signals by independent studies is indicated. Finally, autonomic markers of sympathetic tone using signals such as pulse wave amplitude of the pulse-oximetry signal can provide reliable information of sleep fragmentation.

Capnography guided awake nasal intubation in a 4 month infant with pierre robin syndrome for cleft lip repair-a better technique

SUMMARY

This four-month-old Pierre Robin child was admitted for cleft lip repair with history of two failed attempts at intubation and subsequent cancellation of surgery. The capnography guided awake nasal intubation was considered as the child's parents were desperate to get the surgery done. A modified cuffless endotracheal tube was used with a capnography sampling tube placed within it. With the capnograph guidance the expiratory gas flow was followed to successfully intubate the child.This technique was found to be very convenient and helpful. The use of this technique in an infant has not been reported so far.

Correlations between capnographic waveforms and peak flow meter measurement in emergency department management of asthma

BACKGROUND

The usual method for initial assessment of an acute asthma attack in the emergency room includes the use of peak flow measurement and clinical parameters. Both methods have their own disadvantages such as poor cooperation/effort from patients (peak flow meter) and lack of objective assessment (clinical parameters). We were looking into other methods for the initial asthma assessment, namely the use of capnography. The normal capnogram has an almost square wave pattern comprising phase 1, slope phase 2, plateau phase 3, phase 4 and angle alpha (between slopes 2 and 3). The changes in asthma include decrease in slope of phase 2, increase in slope 3 and opening of angle alpha.

AIMS

Our objective was to compare and assess the correlation between the changes in capnographic indices and peak flow measurement in non-intubated acute asthmatic patients attending the emergency room.

METHODS

We carried out a prospective study in a university hospital emergency department (ED). One hundred and twenty eight patients with acute asthma were monitored with peak flow measurements and then had a nasal cannula attached for microstream sampling of expired carbon dioxide. The capnographic waveform was recorded onto a PC card for indices analysis. The patients were treated according to departmental protocols. After treatment, when they were adjudged well for discharge, a second set of results was obtained for peak flow measurements and capnographic waveform recording. The pre-treatment and post-treatment results were then compared with paired samples t-test analysis. Simple and canonical correlations were performed to determine correlations between the assessment methods. A p value of below 0.05 was taken to be significant.

RESULTS

Peak flow measurements showed significant improvements post-treatment (p < 0.001). On the capnographic waveform, there was a significant difference in the slope of phase 3 (p < 0.001) and alpha angle (p < 0.001), but not in phase 2 slope (p = 0.35). Correlation studies done between the assessment methods and indices readings did not show strong correlations either between the measurements or the magnitude of change pre-treatment and post-treatment.

CONCLUSION

Peak flow measurements and capnographic waveform indices can indicate improvements in airway diameter in acute asthmatics in the ED. Even though the two assessment methods did not correlate statistically, capnographic waveform analysis presents several advantages in that it is effort independent and provides continuous monitoring of normal tidal respiration. They can be proposed for the monitoring of asthmatics in the ED.

Early detection of ruptured bulla by capnography during off pump coronary artery bypass grafting surgery: A case report

Capnography is monitoring of concentration or partial pressure of CO2 in respiratory gases. It provides information about CO2 production, pulmonary perfusion, alveolar ventilation, respiratory patterns and elimination of CO2 from the anesthesia circuit and ventilator. Thus it gives us a rapid and reliable method to detect life threatening conditions such as malposition of tracheal tube, ventilatory failure, circulatory failure and defective breathing circuits. Authors experienced that change of capnogram during off pump coronary artery bypass grafting surgery helped early detecting ruptured bulla and prevented intraopertive or postoperative pneumothorax.