Accuracy of respiratory rate monitoring by capnometry using the Capnomask(R) in extubated patients receiving supplemental oxygen after surgery

A randomized controlled trial of the intraoperative use of noninvasive ventilation versus supplemental oxygen by face mask for procedural sedation in an electrophysiology laboratory

PURPOSE

The efficacy of noninvasive ventilation (NIV) during procedures that require sedation and analgesia has not been established. We evaluated whether NIV reduces the incidence of respiratory events.

METHODS

In this randomized controlled trial, we included 195 patients with an American Society of Anesthesiologists Physical Status of III or IV during electrophysiology laboratory procedures. We compared NIV with face mask oxygen therapy for patients under sedation. The primary outcome was the incidence of respiratory events determined by a computer-driven blinded analysis and defined by hypoxemia (peripheral oxygen saturation < 90%) or apnea/hypopnea (absence of breathing for 20 sec on capnography). Secondary outcomes included hemodynamic variables, sedation, patient safety (composite scores of major or minor adverse events), and adverse outcomes at day 7.

RESULTS

A respiratory event occurred in 89/98 (95%) patients in the NIV group and in 69/97 (73%) patients with face masks (risk ratio [RR], 1.29; 95% confidence interval [CI], 1.13 to 1.47; P < 0.001). Hypoxemia occurred in 40 (42%) patients in the NIV group and in 33 (34%) patients with face masks (RR, 1.21; 95% CI, 0.84 to 1.74; P = 0.30). Apnea/hypopnea occurred in 83 patients (92%) in the NIV group vs 65 patients (70%) with face masks (RR, 1.32; 95% CI, 1.14 to 1.53; P < 0.001). Hemodynamic variables, sedation, major or minor safety events, and patient outcomes were not different between the groups.

CONCLUSIONS

Respiratory events were more frequent among patients receiving NIV without any safety or outcome impairment. These results do not support the routine use of NIV intraoperatively.

STUDY REGISTRATION

ClinicalTrials.gov (NCT02779998); registered 4 November 2015.

Methods for calculating ventilation rates during resuscitation from out-of-hospital cardiac arrest

OBJECTIVE

Ventilation control is important during resuscitation from out-of-hospital cardiac arrest (OHCA). We compared different methods for calculating ventilation rates (VR) during OHCA.

METHODS

We analyzed data from the Pragmatic Airway Resuscitation Trial, identifying ventilations through capnogram recordings. We determined VR by: 1) counting the number of breaths within a time epoch ("counted" VR), and 2) calculating the mean of the inverse of measured time between breaths within a time epoch ("measured" VR). We repeated the VR estimates using different time epochs (10, 20, 30, 60 sec). We defined hypo- and hyperventilation as VR <6 and >12 breaths/min, respectively. We assessed differences in estimated hypo- and hyperventilation with each VR measurement technique.

RESULTS

Of 3,004 patients, data were available for 1,010. With the counted method, total hypoventilation increased with longer time epochs ([10-s epoch: 75 sec hypoventilation] to [60-s epoch: 97 sec hypoventilation]). However, with the measured method, total hypoventilation decreased with longer time epochs ([10-s epoch: 223 sec hypoventilation] to [60-s epoch: 150 sec hypoventilation]). With the counted method, the total duration of hyperventilation decreased with longer time epochs ([10-s epochs: 35 sec hyperventilation] to [60-s epoch: 0 sec hyperventilation]). With the measured method, total hyperventilation decreased with longer time epochs ([10-s epoch: 78 sec hyperventilation] to [60-s epoch: 0 sec hyperventilation]). Differences between the measured and counted estimates were smallest with a 60-s time epoch.

CONCLUSIONS

Quantifications of hypo- and hyperventilation vary with the applied measurement methods. Measurement methods are important when characterizing ventilation rates in OHCA.

A capaciflector provides continuous and accurate respiratory rate monitoring for patients at rest and during exercise

Respiratory rate (RR) is a marker of critical illness, but during hospital care, RR is often inaccurately measured. The capaciflector is a novel sensor that is small, inexpensive, and flexible, thus it has the potential to provide a single-use, real-time RR monitoring device. We evaluated the accuracy of continuous RR measurements by capaciflector hardware both at rest and during exercise. Continuous RR measurements were made with capaciflectors at four chest locations. In healthy subjects (n = 20), RR was compared with strain gauge chest belt recordings during timed breathing and two different body positions at rest. In patients undertaking routine cardiopulmonary exercise testing (CPET, n = 50), RR was compared with pneumotachometer recordings. Comparative RR measurement bias and limits of agreement were calculated and presented in Bland-Altman plots. The capaciflector was shown to provide continuous RR measurements with a bias less than 1 breath per minute (BPM) across four chest locations. Accuracy and continuity of monitoring were upheld even during vigorous CPET exercise, often with narrower limits of agreement than those reported for comparable technologies. We provide a unique clinical demonstration of the capaciflector as an accurate breathing monitor, which may have the potential to become a simple and affordable medical device.Clinical trial number: NCT03832205 https://clinicaltrials.gov/ct2/show/NCT03832205 registered February 6th, 2019.

Respiration monitoring in PACU using ventilation and gas exchange parameters

The importance of perioperative respiration monitoring is highlighted by high incidences of postoperative respiratory complications unrelated to the original disease. The objectives of this pilot study were to (1) simultaneously acquire respiration rate (RR), tidal volume (TV), minute ventilation (MV), SpO₂ and PetCO₂ from patients in post-anesthesia care unit (PACU) and (2) identify a practical continuous respiration monitoring method by analyzing the acquired data in terms of their ability and reliability in assessing a patient’s respiratory status. Thirteen non-intubated patients completed this observational study. A portable electrical impedance tomography (EIT) device was used to acquire RR_EIT, TV and MV, while PetCO₂, RR_Cap and SpO₂ were measured by a Capnostream35. Hypoventilation and respiratory events, e.g., apnea and hypopnea, could be detected reliably using RR_EIT, TV and MV. PetCO₂ and SpO₂ provided the gas exchange information, but were unable to detect hypoventilation in a timely fashion. Although SpO₂ was stable, the sidestream capnography using the oronasal cannula was often unstable and produced fluctuating PetCO₂ values. The coefficient of determination (R²) value between RR_EIT and RR_Cap was 0.65 with a percentage error of 52.5%. Based on our results, we identified RR, TV, MV and SpO₂ as a set of respiratory parameters for robust continuous respiration monitoring of non-intubated patients. Such a respiration monitor with both ventilation and gas exchange parameters would be reliable and could be useful not only for respiration monitoring, but in making PACU discharge decisions and adjusting opioid dosage on general hospital floor. Future studies are needed to evaluate the potential clinical utility of such an integrated respiration monitor.

Preclinical evaluation of noncontact vital signs monitoring using real-time IR-UWB radar and factors affecting its accuracy

Recently, noncontact vital sign monitors have attracted attention because of issues related to the transmission of contagious diseases. We developed a real-time vital sign monitor using impulse-radio ultrawideband (IR-UWB) radar with embedded processors and software; we then evaluated its accuracy in measuring heart rate (HR) and respiratory rate (RR) and investigated the factors affecting the accuracy of the radar-based measurements. In 50 patients visiting a cardiology clinic, HR and RR were measured using IR-UWB radar simultaneously with electrocardiography and capnometry. All patients underwent HR and RR measurements in 2 postures—supine and sitting—for 2 min each. There was a high agreement between the RR measured using radar and capnometry (concordance correlation coefficient [CCC] 0.925 [0.919–0.926]; upper and lower limits of agreement [LOA], − 2.21 and 3.90 breaths/min). The HR measured using radar was also in close agreement with the value measured using electrocardiography (CCC 0.749 [0.738–0.760]; upper and lower LOA, − 12.78 and 15.04 beats/min). Linear mixed effect models showed that the sitting position and an HR < 70 bpm were associated with an increase in the absolute biases of the HR, whereas the sitting position and an RR < 18 breaths/min were associated with an increase in the absolute biases of the RR. The IR-UWB radar sensor with embedded processors and software can measure the RR and HR in real time with high precision. The sitting position and a low RR or HR were associated with the accuracy of RR and HR measurement, respectively, using IR-UWB radar.

Evaluation of respiratory rate monitoring using a microwave Doppler sensor mounted on the ceiling of an intensive care unit: a prospective observational study

Continuous monitoring of the respiratory rate is crucial in an acute care setting. Contact respiratory monitoring modalities such as capnography and thoracic impedance pneumography are prone to artifacts, causing false alarms. Moreover, their cables can restrict patient behavior or interrupt patient care. A microwave Doppler sensor is a novel non-contact continuous respiratory rate monitor. We compared respiratory rate measurements performed with a microwave Doppler sensor mounted on the ceiling of an intensive care unit with those obtained by conventional methods in conscious and spontaneously breathing patients. Participants' respiratory rate was simultaneously measured by visual counting of chest wall movements for 60 s; a microwave Doppler sensor; capnography, using an oxygen mask; and thoracic impedance pneumography, using electrocardiogram electrodes. Bland-Altman analysis for repeated measures was performed to calculate bias and 95% limits of agreement between the respiratory rate measured by visual counting (reference) and that measured by each of the other methods. Among 52 participants, there were 336 (microwave Doppler sensor), 275 (capnography), and 336 (thoracic impedance pneumography) paired respiratory rate data points. Bias (95% limits of agreement) estimates were as follows: microwave Doppler sensor, 0.3 (- 6.1 to 6.8) breaths per minute (bpm); capnography, - 1.3 (- 8.6 to 6.0) bpm; and thoracic impedance pneumography, 0.1 (- 4.4 to 4.7) bpm. Compared to visual counting, the microwave Doppler sensor showed small bias; however, the limits of agreement were similar to those observed in other conventional methods. Our monitor and the conventional ones are not interchangeable with visual counting.Trial registration number: UMIN000032021, March/30/2018.

An impedance pneumography signal quality index: Design, assessment and application to respiratory rate monitoring

Impedance pneumography (ImP) is widely used for respiratory rate (RR) monitoring. However, ImP-derived RRs can be imprecise. The aim of this study was to develop a signal quality index (SQI) for the ImP signal, and couple it with a RR algorithm, to improve RR monitoring. An SQI was designed which identifies candidate breaths and assesses signal quality using: the variation in detected breath durations, how well peaks and troughs are defined, and the similarity of breath morphologies. The SQI categorises 32 s signal segments as either high or low quality. Its performance was evaluated using two critical care datasets. RRs were estimated from high-quality segments using a RR algorithm, and compared with reference RRs derived from manual annotations. The SQI had a sensitivity of 77.7 %, and specificity of 82.3 %. RRs estimated from segments classified as high quality were accurate and precise, with mean absolute errors of 0.21 and 0.40 breaths per minute (bpm) on the two datasets. Clinical monitor RRs were significantly less precise. The SQI classified 34.9 % of real-world data as high quality. In conclusion, the proposed SQI accurately identifies high-quality segments, and RRs estimated from those segments are precise enough for clinical decision making. This SQI may improve RR monitoring in critical care. Further work should assess it with wearable sensor data.

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.

Opioid overdose detection using smartphones

Early detection and rapid intervention can prevent death from opioid overdose. At high doses, opioids (particularly fentanyl) can cause rapid cessation of breathing (apnea), hypoxemic/hypercarbic respiratory failure, and death, the physiologic sequence by which people commonly succumb from unintentional opioid overdose. We present algorithms that run on smartphones and unobtrusively detect opioid overdose events and their precursors. Our proof-of- concept contactless system converts the phone into a short-range active sonar using frequency shifts to identify respiratory depression, apnea, and gross motor movements associated with acute opioid toxicity. We develop algorithms and perform testing in two environments: (i) an approved supervised injection facility (SIF), where people self-inject illicit opioids, and (ii) the operating room (OR), where we simulate rapid, opioid-induced overdose events using routine induction of general anesthesia. In the SIF (n = 209), our system identified postinjection, opioid-induced central apnea with 96% sensitivity and 98% specificity and identified respiratory depression with 87% sensitivity and 89% specificity. These two key events commonly precede fatal opioid overdose. In the OR, our algorithm identified 19 of 20 simulated overdose events. Given the reliable reversibility of acute opioid toxicity, smartphone-enabled overdose detection coupled with the ability to alert naloxone-equipped friends and family or emergency medical services (EMS) could hold potential as a low-barrier, harm reduction intervention.

Use of the ABCDE approach to assess a patient post-operatively: a case study

This article details a case study of the immediate post-operative care of an elective adult patient who presented in a postanaesthetic care unit. It outlines the systematic ABCDE (airway, breathing, circulation, disability and exposure) approach that was used to assess the patient and describes the actions that were taken to manage an airway obstruction that occurred. It also discusses the monitoring of patients required post-operatively, including capnography, peripheral oxygen saturations, blood pressure, temperature, heart rate and respiratory rate, which can assist in the identification and management of any issues and support optimal patient outcomes.

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.

Obstructive sleep apnoea in adults: peri-operative considerations: A narrative review

: Obstructive sleep apnoea (OSA) is a common breathing disorder of sleep with a prevalence increasing in parallel with the worldwide rise in obesity. Alterations in sleep duration and architecture, hypersomnolence, abnormal gas exchange and also associated comorbidities may all feature in affected patients.The peri-operative period poses a special challenge for surgical patients with OSA who are often undiagnosed, and are at an increased risk for complications including pulmonary and cardiovascular, during that time. In order to ensure the best peri-operative management, anaesthetists caring for these patients should have a thorough understanding of the disorder, and be aware of the individual's peri-operative risk constellation, which depends on the severity and phenotype of OSA, the invasiveness of the surgical procedure, anaesthesia and also the requirement for postoperative opioids.The objective of this review is to educate clinicians in the epidemiology, pathogenesis and diagnosis of OSA in adults and also to highlight specific tasks in the preoperative assessment, namely to select a suitable intra-operative anaesthesia regimen, and manage the extent and duration of postoperative care to facilitate the best peri-operative outcome.

Contact-free unconstraint respiratory measurements with load cells under the bed in awake healthy volunteers: breath-by-breath comparison with pneumotachography

Rate of respiration is a fundamental vital sign. Accuracy and precision of respiratory rate measurements with contact-free load cell sensors under the bed legs were assessed by breath-by-breath comparison with the pneumotachography technique during two different dynamic breathing tasks in 16 awake human adults resting on the bed. The subject voluntarily increased and decreased the respiratory rate between 4 and 16 breaths/min ( n = 8) and 10 and 40 breaths/min ( n = 8) at every 2 breaths in 6 different lying postures such as supine, left lateral, right lateral, and 30, 45, and 60° sitting postures. Reciprocal phase changes of the upper and lower load cell signals accorded with the respiratory phases indicating respiratory-related shifts of the centroid along the long axis of the bed. Bland-Altman analyses revealed 0.66 and 1.59 breaths/min standard deviation differences between the techniques (limits of agreement: −1.22 to 1.36 and −2.96 to 3.30) and 0.07 and 0.17 breaths/min fixed bias differences (accuracy) (confidence interval: 0.04 to 0.10 and 0.12 to 0.22) for the mean respiratory rates of 10.5 ± 3.7 and 24.6 ± 8.9 breaths/min, respectively, regardless of the body postures on the bed. Proportional underestimation by this technique was evident for respiratory rates >40 breaths/min. Sample breath increase up to 10 breaths improved the precision from 1.59 to 0.26 breaths/min. Abnormally faster and slower respirations were accurately detected. We conclude that contact-free unconstraint respiratory rate measurements with load cells under the bed legs are accurate and may serve as a new clinical and investigational tool.

NEW & NOTEWORTHY Four load cells placed under the bed legs successfully captured a centroid shift during respiration in human subjects lying on a bed. Breath-by-breath comparison of the breaths covering a wide respiratory rate range by pneumotachography confirmed reliability of the contact-free unconstraint respiratory rate measurements by small standard deviations and biases regardless of body postures. Abnormally faster and slower respirations were accurately detected. This technique should be an asset as a new clinical and investigational tool.

Tracheal sounds accurately detect apnea in patients recovering from anesthesia

Apnea should be monitored continuously in the post anesthesia care unit (PACU) to avoid serious complications. It has been confirmed that tracheal sounds can be used to detect apnea during sedation in healthy subjects, but the performance of this acoustic method has not been evaluated in patients with frequent apnea events in the PACU. Tracheal sounds were acquired from the patients in the PACU using a microphone encased in a plastic bell. Concurrently, a processed nasal pressure signal was used as a reference standard to identify real respiratory events. The logarithm of the tracheal sound variance (log-var) was used to detect apnea, and the results were compared to the reference method. Sensitivity, specificity, positive likelihood ratios (PLR), and negative likelihood ratios (NLR) were calculated. One hundred and twenty-one patients aged 55.5 ± 13.2 years (mean ± SD) with a body mass index of 24.6 ± 3.7 kg/m² were included in data analysis. The total monitoring time was 52.6 h. Thirty-four patients experienced 236 events of apnea lasting for a total of 122.2 min. The log-var apnea detection algorithm detected apnea with 92% sensitivity, 98% specificity, 46 PLR and 0.08 NLR. The performance of apnea detection in the PACU using the log-var tracheal sounds method proved to be reliable and accurate. Tracheal sounds could be used to minimize the potential risks from apnea in PACU patients.

Estimating Respiratory Rate in Post-Anesthesia Care Unit Patients Using Infrared Thermography: An Observational Study

The post-anesthesia care unit (PACU) is the central hub for recovery after surgery, especially when the surgery is performed under general anesthesia. Aside from clinical aspects, respiratory impairment is one of the major causes of morbidity and affected recovery in the PACU and should therefore be monitored. In previous studies, infrared thermography was applied to assess the breathing rate (BR) of healthy volunteers. Here, the transferability of published methods for postoperative patients in the PACU was examined. Video recordings of 28 patients were acquired using a long-wave infrared camera, and analyzed offline. For validation purposes, BRs derived from body surface electrocardiography were measured simultaneously. In general, a close agreement between the two techniques (r = 0.607, p = 0.002 upon arrival, and r = 0.849, p < 0.001 upon discharge from the PACU) was obtained. In conclusion, the algorithm was demonstrated to be feasible and reliable under these challenging conditions.

Frequent respiratory events in postoperative patients aged 60 years and above

There is limited information on the occurrence of respiratory events in postoperative patients after discharge from the postanesthesia care unit. We studied the respiratory rate (RR) of 68 patients aged 60 years and above during the first 6 hours following elective surgery under general anesthesia to assess the frequency of respiratory events in the care unit and on the ward. RR was derived from the continuous RR counter RespiR8, measuring RR by quantifying the humidity of exhaled air. One-minute-averaged RRs were collected and analyzed to assess the frequency of postoperative bradypnea (RR 1–6 breaths/minute) and apnea (cessation of inspiratory flow ≥60 seconds). Values were median (interquartile range) or mean (SD). The median RR was 13 (10–15) breaths/minute. In the 6-hour postoperative period, 78% and 57% of patients experienced at least one bradypnea or apnea event, respectively. A median of ten (3.5–24) bradypnea and three (1–11) apnea events were detected per patient. The occurrence of respiratory events in the postanesthesia care unit (PACU) was a predictor of events on the ward (bradypnea, r²=0.4, P<0.001; apnea, r²=0.2, P<0.001). Morphine consumption correlated weakly with respiratory events in the PACU, but not on the ward. Patients with apnea had significantly larger neck circumference than patients without (39.6 [0.7] versus 37.4 [0.8] cm, P<0.05). Bradypneic or apneic respiratory events are frequent in postoperative elderly patients and even occur relatively late after surgery. Continuous respiratory monitoring on the ward, especially in patients with risk factors, such as early occurrence of events, opioid use, and larger neck circumference, is likely warranted.

A Brief Review of Non-invasive Monitoring of Respiratory Condition for Extubated Patients with or at Risk for Obstructive Sleep Apnea after Surgery

Obstructive sleep apnea (OSA) is one of the important risk factors contributing to postoperative airway complications. OSA alters the respiratory physiology and increases the sensitivity of muscle tone of the upper airway after surgery to residual anesthetic medication. In addition, the prevalence of OSA was reported to be much higher among surgical patients than the general population. Therefore, appropriate monitoring to detect early respiratory impairment in postoperative extubated patients with possible OSA is challenging. Based on the comprehensive clinical observation, several equipment have been used for monitoring the respiratory conditions of OSA patients after surgery, including the continuous pulse oximetry, capnography, photoplethysmography (PPG), and respiratory volume monitor (RVM). To date, there has been no consensus on the most suitable device as a recommended standard of care. In this review, we describe the advantages and disadvantages of some possible monitoring strategies under certain clinical conditions. According to the literature, the continuous pulse oximetry, with its high sensitivity, is still the most widely used device. It is also cost-effective and convenient to use but has low specificity and does not reflect ventilation. Capnography is the most widely used device for detection of hypoventilation, but it may not provide reliable data for extubated patients. Even normal capnography cannot exclude the existence of hypoxia. PPG shows the state of both ventilation and oxygenation, but its sensitivity needs further improvement. RVM provides real-time detection of hypoventilation, quantitative precise demonstration of respiratory rate, tidal volume, and MV for extubated patients, but no reflection of oxygenation. Altogether, the sole use of any of these devices is not ideal for monitoring of extubated patients with or at risk for OSA after surgery. However, we expect that the combined use of continuous pulse oximetry and RVM may be promising for these patients due to their complementary function, which need further study.

Linshom thermodynamic sensor is a reliable alternative to capnography for monitoring respiratory rate

Monitoring ventilation accurately is a technically challenging, yet indispensable aspect of patient care in the intra- and post-procedural settings. A new prototypical device known as the Linshom Respiratory Monitoring Device (LRMD) has been recently designed to non-invasively, inexpensively, and portably measure respiratory rate. The purpose of this study was to measure the accuracy and variability of LRMD measurements of respiratory rate relative to the measurement of capnography. In this prospective study, participants were enrolled and individually fitted with a face mask monitored by the LRMD and capnography. With a baseline oxygen flow rate and digital metronome to pace their respiratory rate, the participants were instructed to breathe at 10 breaths per minute (bpm) for 3 min, 20 bpm for 3 min, 30 bpm for 3 min, 0 bpm for 30 s, and resume regular breathing for 30 s. Both sensors were connected to a computer for continuous temperature and carbon dioxide waveform recordings. The data were then retrospectively analyzed. Twenty-six healthy volunteers, mean (range) age 27.8 (23-37) and mean (range) BMI 23.1 (18.8-29.2) kg/m² were recruited. There were 15 males (57.7%) and 11 females (42.3%). After excluding 3 subjects for technical reasons, 13,800 s of breathing and 4,140 expiratory breaths were recorded. Throughout the protocol, the average standard deviation (SD) for the LRMD and capnography was 1.11 and 1.81 bpm, respectively. The overall mean bias (±2SD) between LRMD and capnography was -0.33 (±0.1.56) bpm. At the lowest and intermediate breathing rates reflective of hypoventilation and normal ventilation, the LRMD variance was 0.55 and 1.23 respectively, compared to capnography with 5.54 and 7.47, respectively. At higher breathing rates indicative of hyperventilation, the variance of the test device was 4.52, still less than that of capnography at 5.73. This study demonstrated a promising correlation between the LRMD and capnography for use as a respiratory rate monitor. The LRMD technology may be a significant addition to monitoring vital signs because it offers a minimally intrusive opportunity to detect respiratory rate and apnea, without expensive or complex anesthetic equipment, before the need for life-saving resuscitation arises.

End-tidal capnographic monitoring to detect apnea episodes during flexible bronchoscopy under sedation

Background

Apnea developing as a result of oversedation is a potential clinical problem in patients undergoing flexible bronchoscopy (FB) under sedation. However, there are no reports of evaluation using a standardized method of the frequency of occurrence of apnea episodes during FB under sedation. The aim of this study was to investigate the frequency of apnea episodes during FB under sedation in the clinical setting by end-tidal capnography.

Methods

This study was a single-institution retrospective review of a prospectively maintained database and medical records, including capnographic data, from April 2015 to March 2016. We enrolled patients who were sedated with midazolam and underwent diagnostic FB under end-tidal capnographic monitoring. Apnea was defined as cessation of airflow for more than 10 s.

Results

Data from a total of 121 eligible patients were analyzed. A total of 131 apnea episodes (median duration 33 s) were recorded in 59 patients (48.8%). Prolonged apnea episodes lasting for more than 30 s occurred in 24 patients (19.8%). Furthermore, 55 apnea episodes (42.0%) were followed by a decline of the SpO₂ by ≥4% from the baseline.

Conclusions

In this study, end-tidal capnography revealed the occurrence of apnea episodes at a high frequency in patients undergoing FB under sedation in the clinical setting.

A Brief Review of Non-invasive Monitoring of Respiratory Condition for Extubated Patients with or at Risk for Obstructive Sleep Apnea after Surgery

Obstructive sleep apnea (OSA) is one of the important risk factors contributing to postoperative airway complications. OSA alters the respiratory physiology and increases the sensitivity of muscle tone of the upper airway after surgery to residual anesthetic medication. In addition, the prevalence of OSA was reported to be much higher among surgical patients than the general population. Therefore, appropriate monitoring to detect early respiratory impairment in postoperative extubated patients with possible OSA is challenging. Based on the comprehensive clinical observation, several equipment have been used for monitoring the respiratory conditions of OSA patients after surgery, including the continuous pulse oximetry, capnography, photoplethysmography (PPG), and respiratory volume monitor (RVM). To date, there has been no consensus on the most suitable device as a recommended standard of care. In this review, we describe the advantages and disadvantages of some possible monitoring strategies under certain clinical conditions. According to the literature, the continuous pulse oximetry, with its high sensitivity, is still the most widely used device. It is also cost-effective and convenient to use but has low specificity and does not reflect ventilation. Capnography is the most widely used device for detection of hypoventilation, but it may not provide reliable data for extubated patients. Even normal capnography cannot exclude the existence of hypoxia. PPG shows the state of both ventilation and oxygenation, but its sensitivity needs further improvement. RVM provides real-time detection of hypoventilation, quantitative precise demonstration of respiratory rate, tidal volume, and MV for extubated patients, but no reflection of oxygenation. Altogether, the sole use of any of these devices is not ideal for monitoring of extubated patients with or at risk for OSA after surgery. However, we expect that the combined use of continuous pulse oximetry and RVM may be promising for these patients due to their complementary function, which need further study.

Use of a Respiratory Volume Monitor to Assess Respiratory Competence in Cardiac Surgery Patients After Extubation

Background

Patients who have undergone cardiac surgery are generally mechanically ventilated postoperatively. Early postoperative extubation is currently recommended in anesthesia guidelines. No current technology can accurately, non-invasively, measure respiratory competence after extubation. Pulse oximetry has been helpful, but this is a late indicator of respiratory compromise. A novel, non-invasive, respiratory volume monitor (RVM) has been shown to deliver accurate continuous, real-time minute ventilation (MV), tidal volume (TV) and respiratory rate (RR) measurements and provide an objective measure of respiratory competence. The RVM will accurately reflect MV, TV and RR in cardiac surgery patients before and after extubation.

Methods

RVM traces were recorded from patients before and after cardiac surgery. Continuous monitoring began on admission to the unit and was ended at 24 h after extubation. RVM-based MV, TV and RR were calculated from 30-s segments. MV, TV and RR were also continuously recorded from the ventilator prior to extubation. The RVM was calibrated to each patient using the readings from the ventilator.

Results

During mechanical ventilation, the RVM measured TVs strongly correlated with the ventilator TVs (r = 0.97). Following extubation, the patient’s breathing became more erratic and TVs and MVs decreased. Within 1 h, all patients studied showed a marked recovery of MV and TV.

Conclusions

RVM-based MV, TV and RR correlated well with similar data collected from ventilators. After extubation, RVM shows promise as a means to monitor respiratory competence of non-intubated patients, and has implications for use in other settings and improving patient safety.

Respiratory rates measured by a standardised clinical approach, ward staff, and a wireless device

BACKGROUND

Respiratory rate is among the first vital signs to change in deteriorating patients. The aim was to investigate the agreement between respiratory rate measurements by three different methods.

METHODS

This prospective observational study included acutely admitted adult patients in a medical ward. Respiratory rate was measured by three methods: a standardised approach over 60 s while patients lay still and refrained from talking, by ward staff and by a wireless electronic patch (SensiumVitals). The Bland-Altman method was used to compare measurements and three breaths per minute (BPM) was considered a clinically relevant difference.

RESULTS

We included 50 patients. The mean difference between the standardised approach and the electronic measurement was 0.3 (95% CI: -1.4 to 2.0) BPM; 95% limits of agreement were -11.5 (95% CI: -14.5 to -8.6) and 12.1 (95% CI: 9.2 to 15.1) BPM. Removal of three outliers with huge differences lead to a mean difference of -0.1 (95% CI: -0.7 to 0.5) BPM and 95% limits of agreement of -4.2 (95% CI: -5.3 to -3.2) BPM and 4.0 (95% CI: 2.9 to 5.0) BPM. The mean difference between staff and electronic measurements was 1.7 (95% CI: -0.5 to 3.9) BPM; 95% limits of agreement were -13.3 (95% CI: -17.2 to -9.5) BPM and 16.8 (95% CI: 13.0 to 20.6) BPM.

CONCLUSION

A concerning lack of agreement was found between a wireless monitoring system and a standardised clinical approach. Ward staff's measurements also seemed to be inaccurate.

Determination of saturation, heart rate, and respiratory rate at forearm using a Nellcor™ forehead SpO2-saturation sensor

Alterations in arterial blood oxygen saturation, heart rate (HR), and respiratory rate (RR) are strongly associated with intra-hospital cardiac arrests and resuscitations. A wireless, easy-to-use, and comfortable method for monitoring these important clinical signs would be highly useful. We investigated whether the Nellcor™ OxiMask MAX-FAST forehead sensor could provide data for vital sign measurements when located at the distal forearm instead of its intended location at the forehead to provide improved comfortability and easy placement. In a prospective setting, we recruited 30 patients undergoing surgery requiring postoperative care. At the postoperative care unit, patients were monitored for two hours using a standard patient monitor and with a study device equipped with a Nellcor™ Forehead SpO₂ sensor. The readings were electronically recorded and compared in post hoc analysis using Bland-Altman plots, Spearman's correlation, and root-mean-square error (RMSE). Bland-Altman plot showed that saturation (SpO₂) differed by a mean of -0.2 % points (SD, 4.6), with a patient-weighted Spearman's correlation (r) of 0.142, and an RMSE of 4.2 points. For HR measurements, the mean difference was 0.6 bpm (SD, 2.5), r = 0.997, and RMSE = 1.8. For RR, the mean difference was -0.5 1/min (4.1), r = 0.586, and RMSE = 4.0. The SpO₂ readings showed a low mean difference, but also a low correlation and high RMSE, indicating that the Nellcor™ saturation sensor cannot reliably assess oxygen saturation at the forearm when compared to finger PPG measurements.

Long-term tolerability of capnography and respiratory inductance plethysmography for respiratory monitoring in pediatric patients treated with patient-controlled analgesia

BACKGROUND

The Anesthesia Patient Safety Foundation has advocated the use of continuous electronic monitoring of oxygenation and ventilation to preemptively identify opioid-induced respiratory depression. In adults, capnography is the gold standard in respiratory monitoring. An alternative technique used in sleep laboratories is respiratory inductance plethysmography (RIP). However, it is not known if either monitor is well tolerated by pediatric patients for prolonged periods of time.

AIM

The goal of this study was to determine whether capnography or RIP is better tolerated in nonintubated, spontaneously breathing pediatric patients being treated with intravenous patient-controlled analgesia (IVPCA).

METHODS

Nasal cannula capnography with oral sampling and thoracic and abdominal inductance plethysmography bands were placed along with the routine monitors on pediatric patients being treated for acute pain with IVPCA. Study monitors were left in place for as long as they were tolerated by the patient, up to a maximum of 24 consecutive hours. If the patient did not wear a particular study monitor for any reason, but tolerated the remaining monitor, participation in the study continued. If the patient would not wear either monitor, participation was terminated.

RESULTS

Twenty-six patients (18 female, eight male, average age 10.1 ± 5.5 years) consented to participate, but only 14 patients attempted to wear one or both the devices. Among those who wore either device, median time to device removal was 8.33 h (range 0.3-23.6 h) for capnography and 23.5 h (range 0.7-24 h) for RIP bands.

CONCLUSION

Children did not tolerate wearing capnography cannulae for prolonged periods of time, limiting the usefulness of this device as a continuous monitor of ventilation in children. RIP bands were better tolerated; however, they require further assessment of their utility. Until more effective, child-friendly monitors are developed and their utility is validated, guidelines recommended for adult patients cannot be extended to children.

The prognostic significance of respiratory rate in patients with pneumonia: a retrospective analysis of data from 705,928 hospitalized patients in Germany from 2010-2012

BACKGROUND

Measurement of the respiratory rate is an important instrument for assessing the severity of acute disease. The respiratory rate is often not measured in routine practice because its clinical utility is inadequately appreciated. In Germany, documentation of the respiratory rate is obligatory when a patient with pneumonia is hospitalized. This fact has enabled us to study the prognostic significance of the respiratory rate in reference to a large medical database.

METHOD

We retrospectively analyzed data from the external quality-assurance program for community-acquired pneumonia for the years 2010-2012. All patients aged 18 years or older who were not mechanically ventilated on admission were included in the analysis. Logistic regression was used to determine the significance of the respiratory rate as a risk factor for in-hospital mortality.

RESULTS

705,928 patients were admitted to the hospital with community-acquired pneumonia (incidence: 3.5 cases per 1000 adults per year). The in-hospital mortality of these patients was 13.1% (92 227 persons). The plot of mortality as a function of respiratory rate on admission was U-shaped and slanted to the right, with the lowest mortality at a respiratory rate of 20/min on admission. If patients with a respiratory rate of 12-20/min are used as a baseline for comparison, patients with a respiratory rate of 27-33/min had an odds ratio (OR) of 1.72 for in-hospital death, and those with a respiratory rate above 33/min had an OR of 2.55. Further independent risk factors for in-hospital death were age, admission from a nursing home, hospital, or rehabilitation facility, chronic bedridden state, disorientation, systolic blood pressure, and pulse pressure.

CONCLUSION

Respiratory rate is an independent risk marker for in-hospital mortality in community-acquired pneumonia. It should be measured when patients are admitted to the hospital with pneumonia and other acute conditions.

Assessment of noninvasive acoustic respiration rate monitoring in patients admitted to an Emergency Department for drug or alcoholic poisoning

To compare respiration rate measurement by an acoustic method and thoracic impedance to capnometry as the reference method, in patients at the Emergency Department after drug or alcoholic poisoning. In this observational study, 30 patients aged 18 or older, hospitalized at the Emergency Department for drug or alcoholic poisoning, without any contraindication to a face mask and/or a cervical acoustic sensor, were included in the study. They benefited from a simultaneous recording of their respiration rate by the acoustic method (RRa(®), Masimo Corp., Irvine, CA, USA), by thoracic impedance (Philips Intellivue(®) MP2, Suresnes, France) and by capnometry (Capnostream(®) 20, Oridion, Jerusalem, Israël) through a face mask (Capnomask(®), Mediplus Ltd, Raleigh, NC, USA) for 40-60 min. Of the 86,578 triplets collected, 77,155 (89.1%) were exploitable. Median (range) respiration rate measured by capnometry was 18 (7-29) bpm. Compared to capnometry, bias and limits of agreement were 0.1 ± 3.8 bpm for the acoustic method and 0.3 ± 5.5 bpm for thoracic impedance. The proportions of RR values collected by acoustic method or by thoracic impedance which differed over 10 or 20% during more than 15 s, compared to capnometry, were 8.3 versus 14.3, and 1.5 versus 3.8%, respectively (p < 0.0001). The acoustic sensor had to be repositioned on three patients. For 11 patients, the Capnomask(®) was removed several times. In patients with drug or alcoholic poisoning, the acoustic method seems more accurate than thoracic impedance and better tolerated than face mask capnometry.

Comparison of acoustic and impedance methods with mask capnometry to assess respiration rate in obese patients recovering from general anaesthesia

Respiratory depression, a potentially serious complication after general anaesthesia, can be detected promptly by close monitoring of both oxygen saturation and respiratory rate. Obese patients have morphological changes that may impair the reliability of monitoring devices. In this study, respiration rate was simultaneously recorded every second for up to 60 min using a computer in 30 adult obese patients (body mass index ≥ 35 kg.m(-2)), by three methods: acoustic; thoracic impedance; and capnometry via a facemask (Capnomask, reference method). Of the 99,771 data triplets collected, only 85,520 (86%) were included; 12,021 (84%) were not studied due to failure of capnometry and 2240 (16%) due to failure of the acoustic method. Compared with capnometry, bias was similar using both the acoustic method and impedance (-0.3 bpm vs. -0.6 bpm, respectively, p = 0.09), but limits of agreement were narrower for the acoustic method (±3.5 bpm vs. ±5.3 bpm, respectively, p = 0.0008). The proportion of respiration rate values obtained with the acoustic method and impedance that differed by at least 10% or 20% for more than 15 s were 11% vs. 23% and 2% vs. 6%, respectively (p = 0.0009 for both comparisons). The acoustic sensor was well tolerated, while the facemask was pulled off on several occasions by four (13%) agitated patients. In obese patients requiring close monitoring of respiration rate, the acoustic method may be more precise than thoracic impedance and better tolerated than capnometry with a facemask.

Accuracy of acoustic respiration rate monitoring in pediatric patients

BACKGROUND

Rainbow acoustic monitoring (RRa) utilizes acoustic technology to continuously and noninvasively determine respiratory rate from an adhesive sensor located on the neck.

OBJECTIVE

We sought to validate the accuracy of RRa, by comparing it to capnography, impedance pneumography, and to a reference method of counting breaths in postsurgical children.

METHODS

Continuous respiration rate data were recorded from RRa and capnography. In a subset of patients, intermittent respiration rate from thoracic impedance pneumography was also recorded. The reference method, counted respiratory rate by the retrospective analysis of the RRa, and capnographic waveforms while listening to recorded breath sounds were used to compare respiration rate of both capnography and RRa. Bias, precision, and limits of agreement of RRa compared with capnography and RRa and capnography compared with the reference method were calculated. Tolerance and reliability to the acoustic sensor and nasal cannula were also assessed.

RESULTS

Thirty-nine of 40 patients (97.5%) demonstrated good tolerance of the acoustic sensor, whereas 25 of 40 patients (62.5%) demonstrated good tolerance of the nasal cannula. Intermittent thoracic impedance produced erroneous respiratory rates (>50 b·min(-1) from the other methods) on 47% of occasions. The bias ± SD and limits of agreement were -0.30 ± 3.5 b·min(-1) and -7.3 to 6.6 b·min(-1) for RRa compared with capnography; -0.1 ± 2.5 b·min(-1) and -5.0 to 5.0 b·min(-1) for RRa compared with the reference method; and 0.2 ± 3.4 b·min(-1) and -6.8 to 6.7 b·min(-1) for capnography compared with the reference method.

CONCLUSIONS

When compared to nasal capnography, RRa showed good agreement and similar accuracy and precision but was better tolerated in postsurgical pediatric patients.

The accuracy, precision and reliability of measuring ventilatory rate and detecting ventilatory pause by rainbow acoustic monitoring and capnometry

BACKGROUND

Current methods for monitoring ventilatory rate have limitations including poor accuracy and precision and low patient tolerance. In this study, we evaluated a new acoustic ventilatory rate monitoring technology for accuracy, precision, reliability, and the ability to detect pauses in ventilation, relative to capnometry and a reference method in postsurgical patients.

METHODS

Adult patients presenting to the postanesthesia care unit were connected to a Pulse CO-Oximeter with acoustic monitoring technology (Rad-87, version 7804, Masimo, Irvine, CA) through an adhesive bioacoustic sensor (RAS-125, rev C) applied to the neck. Each subject also wore a nasal cannula connected to a bedside capnometer (Capnostream20, version 4.5, Oridion, Needham, MA). The acoustic monitor and capnometer were connected to a computer for continuous acoustic and expiratory carbon dioxide waveform recordings. Recordings were retrospectively analyzed by a trained technician in a setting that allowed for the simultaneous viewing of both waveforms while listening to the breathing sounds from the acoustic signal to determine inspiration and expiration reference markers within the ventilatory cycle without using the acoustic monitor- or capnometer-calculated ventilatory rate. This allowed the automatic calculation of a reference ventilatory rate for each device through a software program (TagEditor, Masimo). Accuracy (relative to the respective reference) and precision of each device were estimated and compared with each other. Sensitivity for detection of pauses in ventilation, defined as no inspiration or expiration activity in the reference ventilatory cycle for ≥30 seconds, was also determined. The devices were also evaluated for their reliability, i.e., the percentage of the time when each displayed a value and did not drop a measurement.

RESULTS

Thirty-three adults (73% female) with age of 45 ± 14 years and weight 117 ± 42 kg were enrolled. A total of 3712 minutes of monitoring time (average 112 minutes per subject) were analyzed across the 2 devices, reference ventilatory rates ranged from 1.9 to 49.1 bpm. Acoustic monitoring showed significantly greater accuracy (P = 0.0056) and precision (P- = 0.0024) for respiratory rate as compared with capnometry. On average, both devices displayed data over 97% of the monitored time. The (0.95, 0.95) lower tolerance limits for the acoustic monitor and capnometer were 94% and 84%, respectively. Acoustic monitoring was marginally more sensitive (P = 0.0461) to pauses in ventilation (81% vs 62%) in 21 apneic events.

CONCLUSIONS

In this study of a population of postsurgical patients, the acoustic monitor and capnometer both reliably monitored ventilatory rate. The acoustic monitor was statistically more accurate and more precise than the capnometer, but differences in performance were modest. It is not known whether the observed differences are clinically significant. The acoustic monitor was more sensitive to detecting pauses in ventilation. Acoustic monitoring may provide an effective and convenient means of monitoring ventilatory rate in postsurgical patients.

Accuracy of respiratory rate monitoring using a non-invasive acoustic method after general anaesthesia

BACKGROUND

Respiratory rate should be monitored continuously in the post-anaesthesia care unit (PACU) to avoid any delay in the detection of respiratory depression. Capnometry is the standard of care but in extubated patients requires a nasal cannula or a face mask that may be poorly tolerated or can be dislodged, leading to errors in data acquisition and false alarms. The value of a new non-invasive acoustic monitor in this setting has not been fully investigated.

METHODS

Adult patients admitted to the PACU after general anaesthesia were included. After tracheal extubation, an adhesive sensor with an integrated acoustic transducer (RRa™) was placed on the patient's throat and connected to its monitor while the patient breathed through a face mask with a carbon dioxide sampling port (Capnomask™) connected to a capnometer. Both the acoustic monitor and the capnometer were connected to a computer to record one pair of data per second for up to 60 min.

RESULTS

Fifty-two patients, mean (range) age 54 (22-84) yr and BMI 26 (19-39) kg m(-2), were studied. Compared with capnometry, the bias and limits of agreement of the acoustic method were 0 (-1.4-1.4) bpm. The acoustic sensor was well tolerated while the face mask was removed by eight patients, leading to study discontinuation in two patients.

CONCLUSIONS

In extubated patients, continuous assessment of respiration rate with an acoustic monitor correlated well with capnometry.