Serene H. Chang

Pain assessment and management in medical wards: an area of unmet need

Background Acute Pain Services (APS) were introduced primarily to improve postoperative pain management. Although pain is similar in prevalence and severity in medical and surgical wards, its assessment and management in non-surgical patients often receives less attention and resources. Objective To investigate the extent of APS involvement on medical wards and obtain perceptions of deficiencies. Method A questionnaire was mailed to APS leads in 287 UK NHS hospitals; 229 questionnaires were returned (79.8% response). Results Only 36 (16%) of the 225 hospitals with medical wards reported routine APS involvement. Pain scores were not recorded in 75 (33%) hospitals, 11 (5%) denied knowledge about assessments being conducted, and 185 (82.2%) respondents felt that pain management on medical wards was inadequate. Conclusions Perceived lack of training and awareness of healthcare staff were highly ranked contributing factors, and this was attributed to inadequate funding. This study highlights the scope for improvement of pain control in medical patients, with benefits from reduced morbidity and faster recovery.

Photoplethysmographic measurements from the esophagus using a new fiber-optic reflectance sensor

A prototype fiber-optic reflectance-mode pulse oximetry sensor and measurement system is developed for the purposes of estimating arterial oxygen saturation in the esophagus. A dedicated probe containing miniature right-angled glass prisms coupled to light sources and a photodetector by means of optical fibers is designed and used to record photoplethysmographic (PPG) signals from the esophageal epithelium in anesthetized patients. The probe is inserted simply by an anesthesiologist in all cases, and signals are recorded successfully in all but one of 20 subjects, demonstrating that esophageal PPG signals can be reliably obtained. The mean value of the oxygen saturation recorded from the esophagus for all subjects is 94.0 ± 4.0%. These results demonstrate that SpO(2) may be estimated in the esophagus using a fiber-optic probe.

Cerebral Arterial Oxygen Saturation Measurements Using a Fiber-Optic Pulse Oximeter

BackgroundA pilot investigation was undertaken to assess the performance of a novel fiber-optic cerebral pulse oximetry system. A fiber-optic probe designed to pass through the lumen of a cranial bolt of the type used to make intracranial pressure measurements was used to obtain optical reflectance signals directly from brain tissue.MethodsShort-duration measurements were made in six patients undergoing neurosurgery. These were followed by a longer duration measurement in a patient recovering from an intracerebral hematoma. Estimations of cerebral arterial oxygen saturation derived from a frequency domain-based algorithm are compared with simultaneous pulse oximetry (SpO2) and hemoximeter (SaO2) blood samples.ResultsThe short-duration measurements showed that reliable photoplethysmographic signals could be obtained from the brain tissue. In the long-duration study, the mean (±SD) difference between cerebral oxygen saturation (ScaO2) and finger SpO2 (in saturation units) was −7.47(±3.4)%. The mean (±SD) difference between ScaO2 and blood SaO2 was −7.37(±2.8)%.ConclusionsThis pilot study demonstrated that arterial oxygen saturation may be estimated from brain tissue via a fiber-optic pulse oximeter used in conjunction with a cranial bolt. Further studies are needed to confirm the clinical utility of the technique.

A comparison of the respiratory effects of oxycodone versus morphine: a randomised, double-blind, placebo-controlled investigation*

Oxycodone’s respiratory profile (particularly the extent of respiratory depression in comparison to morphine) remains to be fully characterised in the peri‐operative period. We randomly assigned ASA 1‐2 adults for elective surgery under general anaesthesia to receive saline, morphine 0.1 mg.kg−1, or oxycodone 0.05 mg.kg−1, 0.1 mg.kg−1, or 0.2 mg.kg−1. Results were obtained from six patients in the saline group, 12 patients in the groups receiving morphine 0.1 mg.kg−1, oxycodone 0.05 mg.kg−1 and 0.1 mg.kg−1, and from 10 patients who received oxycodone 0.2 mg.kg−1. Patients were breathing spontaneously and minute ventilation monitored with a wet wedge spirometer for 30 min. All active groups demonstrated significant respiratory depression compared to saline (p < 0.0001 for all groups). The mean (SD) reduction in minute volume from baseline was 22.6% (10.4%) for the morphine 0.1 group and 53.3% (27.2%), 74.4% (12.9%) and 88.6% (13.5%) for the oxycodone 0.05, 0.1 and 0.2 groups, respectively, with significant dose dependent differences between oxycodone groups (p = 0.0007). The extent and speed of onset of oxycodone induced respiratory depression was dose dependent and greater than an equivalent dose of morphine.

An oesophageal pulse oximetry system utilising a fibre-optic probe

A dual-wavelength fibre-optic pulse oximetry system is described for the purposes of estimating oxygen saturation (SpO2) from the oesophagus. A probe containing miniature right-angled glass prisms was used to record photoplethysmographic (PPG) signals from the oesophageal wall. Signals were recorded successfully in 19 of 20 patients, demonstrating that PPG signals could be reliably obtained from an internal vascularised tissue site such as the oesophageal epithelium. The value of the mean oxygen saturation recorded from the oesophagus was 94.0 ± 4.0%. These results demonstrate that SpO2 may be estimated in the oesophagus using a fibre-optic probe.

Evaluation of a fiber-optic esophageal pulse oximeter

A dual-wavelength fiber-optic pulse oximetry system was developed for the purposes of estimating oxygen saturation from the esophagus. A probe containing miniature right-angled glass prisms was used to record photoplethysmographic (PPG) signals from the esophageal wall. Signals were recorded successfully in 19 of 20 patients, demonstrating that PPG signals could be reliably obtained from an internal vascularized tissue site such as the esophageal epithelium. The value of the mean oxygen saturation recorded from the esophagus was 94.0 ± 4.0%. These results demonstrate that SpO2 may be estimated in the esophagus using a fiber-optic probe and this may be the first report of such measurements.

Measurements of cerebral arterial oxygen saturation using a fiber-optic pulse oximeter

This pilot investigation was undertaken to assess the performance of a novel fiber-optic cerebral pulse oximetry system. A fiber-optic probe designed to pass through the lumen of a cranial bolt of the type used to make intracranial pressure measurements was used to obtain optical reflectance signals directly from the brain tissue. Preliminary results from seven patients measured in the operating theatre and ITU are presented. Estimations of cerebral arterial oxygen saturation derived from a frequency domain-based algorithm are compared with pulse oximetry (SpO<inf>2</inf>) and hemoximeter (SaO<inf>2</inf>) blood samples. The mean (±SD) difference between cerebral oxygen saturation (ScaO<inf>2</inf>) and finger SpO<inf>2</inf> (in saturation units) was -7.47(±3.4)%. The mean (±SD) difference between ScaO<inf>2</inf> and blood SaO<inf>2</inf> was -7.37(±2.8)%.

Preliminary Evaluation of a Fiber Optic Cerebral Oximetry System in Patients Undergoing Neurosurgery

The primary objective of this proof-of-concept pilot study was to investigate the feasibility of detecting photoplethysmographic(PPG) signals and estimating blood oxygen saturation (Spo2) values from the esophagus of children and neonates. This vital measurement can be impossible to obtain at times when it is most needed during septic shock, circulatory collapse, or cardiac arrest.

Photoplethysmographic measurements from central nervous system tissue

A new system for measuring the oxygen saturation of blood within tissue has been developed, for a number of potential patient monitoring applications. This proof of concept project aims to address the unmet need of real-time measurement of oxygen saturation in the central nervous system (CNS) for patients recovering from neurosurgery or trauma, by developing a fibre optic signal acquisition system for internal placement through small apertures. The development and testing of a two-wavelength optical fibre reflectance photoplethysmography (PPG) system is described together with measurements in rats and preliminary results from a clinical trial of the system in patients undergoing neurosurgery. It was found that good quality red and near-infrared PPG signals could be consistently obtained from the rat spinal cord (n=6) and human cerebral cortex (n=4) using the fibre optic probe. These findings justify further development and clinical evaluation of this fibre optic system.