Continuous Respiratory Monitoring Research Articles

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.

A non-contact vision-based system for respiratory rate estimation.

A non-contact vision-based system is presented for continuous respiratory rate monitoring. The system identifies feature points in a video feed and tracks them over time. Two methods are presented for comparison - a method which uses principal component analysis (PCA) and a simple averaging approach. These methods condense the feature point trajectories into a compact set of representative signals. The signal which most closely resembles an expected respiratory trace is selected based on spectral analysis. System performance is assessed by comparing the estimated respiratory rate to the rate determined via inductance plethysmogram. The system was evaluated on 5 participants in 4 simulated sleep scenarios. Accuracies of within 1 breath/minute were achieved for more than 97% of the recorded time in all scenarios. The proposed system is accurate, cost-effective, and simple, making it a suitable candidate for at-home installation.

Electromagnetic respiratory effort harvester: human testing and metabolic cost analysis.

Remote health monitoring is increasingly recognized as a valuable tool in chronic disease management. Continuous respiratory monitoring could be a powerful tool in managing chronic diseases, however it is infrequently performed because of obtrusiveness and inconvenience of the existing methods. The movements of the chest wall and abdominal area during normal breathing can be monitored and harvested to enable self-powered wearable biosensors for continuous remote monitoring. This paper presents human testing results of a light-weight (30 g), wearable respiratory effort energy harvesting sensor. The harvester output voltage, power, and its metabolic burden, are measured on twenty subjects in two resting and exercise conditions each lasting 5 min. The system includes two off-the-shelf miniature electromagnetic generators harvesting and sensing thoracic and abdominal movements. Modules can be placed in series to increase the output voltage for rectification purposes. Electromagnetic respiratory effort harvester/sensor system can produce up to 1.4 V, 6.44 mW, and harvests 30.4 mJ during a 5-min exercise stage. A statistical paired t-test analysis of the calculated EE confirmed there is no significant change ( P > 0.05 ) in the metabolic rate of subjects wearing the electromagnetic harvester and biosensor.

Continuous respiratory monitoring for sleep apnea screening by ambulatory hemodynamic monitor

To validate the sleep-disordered breathing components of a portable electrocardiography and hemodynamic monitor to be used for sleep apnea screening. Sleep-disordered breathing (SDB) is associated with cardiovascular disease. Patients with existing cardiovascular disease may have unrecognized SDB or may develop SDB while under the care of a cardiologist. A screening device for SDB, easy to use and appealing to cardiologists, would assist in referral of appropriate patients for full polysomnography (PSG). A cardiac and respiratory monitor (CPAM) was attached to patients undergoing PSG and an apnea/hypopnea index (AHI) generated. The CPAM device produced respiration rate, snoring rate, individual apnea/hypopnea events and an SDB severity score (SDBSS). In addition to AHI, an expert over-reader annotated individual breaths, snores and SDB breathing events to which the automated algorithms were compared. The test set consisted of data from 85 patients (age: 50.5 ± 12.4 years). Of these, 57 had a positive PSG defined as AHI ≥ 5.0 (mean: 30.0 ± 29.8, negative group mean: 1.5 ± 1.2). The sensitivity and specificity of the SDBSS compared to AHI was 57.9% and 89.3%, respectively. The correlation of snoring rate by CPAM compared to the expert over-reader was r = 0.58 (mean error: 1.52 snores/min), while the automated respiration rate had a correlation of r = 0.90 (mean error: 0.70 breaths/min). This performance assessment shows that CPAM can be a useful portable monitor for screening and follow-up of subjects for SDB.

Postoperative Analgesia and Respiratory Events in Patients with Symptoms of Obstructive Sleep Apnoea

Symptoms of obstructive sleep apnoea are common in patients presenting for surgery and are associated with increased morbidity. Analgesia contributes significantly to postoperative respiratory depression and obstruction, so we compared standard morphine patient-controlled analgesia with an opioid-sparing protocol (tramadol patient-controlled analgesia, parecoxib and rescue-only morphine) in these patients. Sixty-two patients presenting for elective surgery with body mass index > or = 28 and signs or symptoms suggesting obstructive sleep apnoea were randomised to receive either the opioid or opioid-sparing postoperative analgesia protocol, with continuous respiratory monitoring for 12 hours on the first postoperative night. The number of respiratory events (apnoeas and hypopnoeas) and oxygen desaturations were compared. There was no difference between treatment groups in the number of obstructive apnoeas, hypopnoeas or central apnoeas. However, central apnoeas and a rate of respiratory events > 15 per hour were related to postoperative morphine dose (P = 0.005 and P = 0.002). In patients at risk of obstructed breathing, intention to treat with an opioid-sparing analgesia protocol did not decrease the rate of respiratory events, although the rate was still related to the total morphine dose.

A monoscopic method for real-time tumour tracking using combined occasional x-ray imaging and continuous respiratory monitoring

Three major linear accelerator vendors offer gantry-mounted single (monoscopic) x-ray imagers. The use of monoscopic imaging to estimate three-dimensional (3D) target positions has not been fully explored. The purpose of this work is to develop and investigate a robust monoscopic method for real-time tumour tracking, combining occasional x-ray imaging and continuous external respiratory monitoring, and compare this with an established stereoscopic method. Monoscopic estimation of 3D target positions is a two-step procedure. Step (1) is similar to the stereoscopic approach using combined occasional x-ray imaging and real-time external respiratory monitoring, i.e. to establish the correlation between the target coordinates T(x, y, z) and the external respiratory signal (R) (sECM: stereoscopic external correlation model). However, in monoscopic estimation, the correlation between the two coordinates (xp, yp) projected on the imager plane and the external respiratory signal (mECM: monoscopic external correlation model) is established. With only a single projection, the component of the 3D target position, which is along the x-ray imaging direction, is unresolved. Therefore, step (2) is used to estimate the unresolved component (z∥) by building a correlation model between the unresolved component and the two other components projected on the imager (ICM: internal correlation model) with a prior 3D target trajectory that may be obtained by 4DCT, MV/kV imaging or 4DCBCT. At the time of prediction, (xp, yp) are estimated from (R) using the correlation model in step (1), and then z∥ is estimated from the estimated (xp, yp) using the correlation model in step (2). The performance of the proposed method was evaluated under various model update intervals and compared with the stereoscopic estimation method using 160 tumour trajectory and external respiratory motion data recorded at 25 Hz from 46 thoracic and abdominal cancer patients who underwent hypofractionated stereotactic radiotherapy by a CyberKnife system. The precision of the input data used in this study to represent tumour motion was assessed using x-ray imaging to be 1.5 ± 0.8 mm. Monoscopic imaging every 30/60 s with updating ICM every 120/180 s can estimate target positions with a 1 mm root-mean-square error (RMSE) for 63/53% or a 2 mm RMSE for 93/91%, respectively. In contrast, stereoscopic x-ray imaging every 30/60 s can estimate target motion within a 1 mm RMSE for 72/58% or a 2 mm RMSE for 95/92%, respectively. The overall 3D error of the monoscopic estimation is approximately 10% higher than comparable stereoscopic imaging methods when the period between imaging is 1 s or more, and 40% higher for continuous imaging. The promising result may be explained by the fact that superior/inferior motion–the major axis of tumour motion–is fully resolved even in the monoscopic view for coplanar treatments, and tumour motion in each dimension is relatively well correlated.

Continuous Oximetry/Capnometry Monitoring Reveals Frequent Desaturation and Bradypnea During Patient-Controlled Analgesia

The most serious complication of patient-controlled analgesia (PCA) is respiratory depression (RD). The incidence of RD in the literature is derived from intermittent sampling of pulse oximetry (Spo(2)) and respiratory rate and defined as a deviation below an arbitrary threshold. We monitored postsurgical patients in a hospital ward receiving morphine or meperidine PCA with continuous oximetry and capnography. Nurses responding to audible monitor bedside alarms documented respiratory status and interventions. A total of 178 patients were included in the analysis, 12% and 41% of whom had episodes of desaturation (Spo(2) <90%) and bradypnea (respiratory rate <10) lasting 3 min or more. One patient required "rescue" with positive pressure ventilation, and none required naloxone. Patients over 65 years of age and the morbidly obese were at greater risk for desaturation. Patients over 65 years of age were also more likely to have bradypnea, whereas the morbidly obese and patients receiving continuous infusions were less likely to have bradypnea. Our incidence of RD by bradypnea is significantly higher than the 1%-2% incidence in the literature, using the same threshold criteria but more stringent duration criteria, while our incidence of RD based on desaturation is consistent with previous estimates. We conclude that continuous respiratory monitoring is optimal for the safe administration of PCA, because any RD event can progress to respiratory arrest if undetected. Better alarm algorithms must be implemented to reduce the frequent alarms triggered by threshold criteria for RD.

Design and Optimization of an Ultra-Sensitive Piezoresistive Accelerometer for Continuous Respiratory Sound Monitoring

Design and Optimization of an Ultra-Sensitive Piezoresistive Accelerometer for Continuous Respiratory Sound Monitoring

Transdermal patient-controlled analgesia

Viscusi and Schechter1 provide a useful summary of various techniques of pain management using patient-controlled analgesia (PCA) delivered by different routes including epidural, i.v., and transdermal. Their analysis of the potential benefits of patient-activated transdermal analgesia system (PATS) delivery of fentanyl for PCA over other routes of administration suggests that this method may enhance effectiveness and minimize adverse respiratory events, particularly those associated with PCA pump-programming errors. We provide additional insight into these issues on the basis of our use of new technology that assesses continuous respiratory monitoring for patients receiving i.v. PCA with multiple opioid drugs. Since June 2004, we have used two respiratory monitoring devices to continuously measure arterial oxygen saturation and exhaled end-tidal carbon dioxide as part of an integrated, modular system of i.v. PCA delivery.a These devices have identified multiple patients who have experienced respiratory depression that might not have otherwise been detected before serious negative outcomes occurred.2,3 In addition, our analysis of continuous quality improvement (CQI) data from these devices indicates that respiratory depression in patients using PCA may be more common than is currently believed.4,–6

Clinical experience with patient-controlled analgesia using continuous respiratory monitoring and a smart infusion system

Ensuring safe and effective opioid use—a critical therapy that combines high-risk drugs with highly variable patient response—is one of the biggest challenges in medicine. The use of patient-controlled analgesia (PCA) for opioid administration has the potential to greatly improve the use of

Capnography for monitoring non-intubated spontaneously breathing patients in an emergency room setting.

OBJECTIVE: To examine the feasibility of using expiratory capnography as an indicator of airway obstruction in non-intubated resuscitation room patients. METHODS: Patients with potential respiratory compromise admitted to the resuscitation...

Postoperative pulse oximetry of patients in maxillomandibular fixation

Following oral and maxillofacial surgery requiring maxillomandibular fixation (MMF), patients are at risk for respiratory problems that may result in decreased arterial oxygen saturation. As a pilot study, oxygen saturation was continuously monitored for 36 hours in 34 patients having 37 procedures requiring MMF. There were 28 hypoxic episodes in 12 patients. These observations emphasize the need for continuous respiratory monitoring during the postoperative period for patients in MMF, even when supplemental oxygen is used.

1473 ABNORMAL CARDIORESPIROGRAPHIC (CRG) TRACINGS AND ELEVATED SERUM CREATINE PHOSPHOKINASE (CPK) IN INFANTS OF DRDG DEPENDENT MOTHERS. (IDDM)

Continuous respiratory & heart rate monitoring were done during the first 5 postnatal days in 12 IDDM & 19 normal infants (control). The results showed abnormal CRG patterns in the IDDM such as: (1) significantly (p<0.01) higher baseline heart rate. (BHR), beat to beat (BBV) & long term (LTV) variability, and resp. rate (RR) - See Table, (2) exaggerated response of HR to stimuli such as light, noise or pain, and (3) frequent & spontaneous occurences of large (Δ40 bpm), brief, rise and fall in HR giving a characteristic “wave-like” appearance to the tracings. The BBV & LTV changes were also more intense (p<0.02) in the IDDM with moderate to severe, as compared to mild withdrawal. Treatment of the withdrawal with drugs, did not abolish the CRG abnormalities despite distinct clinical improvement. Serum CPK (normal = 80 - 450 IU/L) was also analyzed in 16 IDDM during the first 2-7 days of life. Eleven infants (69%) had markedly elevated CPK levels (Mean = 1313 ± 401 IU/L; range = 459 - 5123), & predominantly of the MM fraction (89%). The elevated CPK did not correlate with the infant's birth weight, GA or Apgar score, but was usually found in the infants with significant tremors & hypertonicity. Conclusion: The chronic exposure of infants to drugs of abuse, in utero, induces striking changes in their CRG patterns postnatally & elevation of their serum CPK isoenzymes. These new findings may provide a probe which can be used to study this group of infants, ante-natally & postnatally.