Continuous Pulse Oximetry Research Articles

All parturients receiving neuraxial morphine should be monitored with continuous pulse oximetry

Although no psychic, I can read the writing on the walls. Findings from large databases that focus on complications, initiatives to improve patient safety, and changing patient demographics are aligning to compel regulatory bodies to develop guidelines or mandates that will require continuous monitoring of oxygenation and ventilation in patients given neuraxial or parenteral opioids for postoperative pain. At the same time, technological advances will enable this potential change in practice standards.

An Ounce of Prevention May Equate to a Pound of Cure

An Ounce of Prevention May Equate to a Pound of Cure

Postoperative Hypoxemia: Common, Undetected, and Unsuspected After Bariatric Surgery

Patients undergoing gastric bypass are at greater than ordinary risk for postoperative respiratory insufficiency, presumably related to obstructive sleep apnea (OSA) and patient-controlled analgesia (PCA). This study was proposed to quantify the magnitude of the problem. Fifteen patients undergoing gastric bypass had oxygen saturation (SpO(2)) recorded continuously, but not displayed, for 24h postoperatively; eight also had arterial blood analysis every 4h. All received narcotic PCA. SpO(2)<90% lasting more than 10 s was reviewed. Results are mean+/-SEM. Mean age was 44+/-4 y, and mean BMI was 48+/-2kg/m(2); 77% had OSA. Every patient had more than one episode with SpO(2)<90% for longer than 30s undetected by routine monitoring; most had multiple episodes. Nadir SpO(2) averaged 75% +/- 8%. Mean longest duration of desaturation below 90% averaged 21+/-15min. Mean PaCO(2) was 37+/-3mm Hg; maximum PaCO(2) was 47mm Hg. Severe and prolonged episodes of hypoxemia were a consistent finding, despite aggressive preoperative diagnosis and treatment of OSA, including use of CPAP postoperatively. Although some postoperative hypoventilation was expected, the degree and frequency of desaturation were surprising. No patient exhibited arterial PaCO(2) evidence of hypoventilation. No patient experienced cardiopulmonary arrest/instability, in spite of severe, repeated episodes of hypoxemia. In no instance was a significant hypoxemic episode suspected or detected. Continuous pulse oximetry monitoring, with an audible alarm set for a saturation less than 90% for 10 s, would have alerted providers to 100% of significant hypoxemic episodes. Our recommendation is routinely monitoring (with alarm capability enabled) every bariatric surgical patient, to prevent such occurrence.

Is your patient sleeping?

Is your patient sleeping?

Survey of perioperative care of adults with obstructive sleep apnoea

Survey of perioperative care of adults with obstructive sleep apnoea

Reproducibility of the 6-Minute Walk Test for Ambulatory Oxygen Prescription

Background: Ambulatory oxygen is frequently prescribed for patients with chronic obstructive pulmonary disease (COPD) who have oxygen desaturation ≤88% during exercise. The 6-min walk test (6MWT) with continuous pulse oximetry monitoring is a common method to document this oxygen desaturation, but the reproducibility of this test in determining the need for ambulatory oxygen in patients with COPD is not well documented. Objective:The aim of this study was to establish the reproducibility of the 6MWT in determining the need for ambulatory oxygen prescription in stable COPD patients using the Centers for Medicare and Medicaid (CMS) criteria for ambulatory oxygen prescription. Methods:The study was designed as a prospective observational study in an academic health center and associated pulmonary rehabilitation program. Eighty-eight COPD patients referred to pulmonary rehabilitation underwent continuous pulse oximetry while performing standard 6MWT on 3 separate days. Results: Fifty-one (58%) of these patients desaturated by continuous pulse oximetry to an SpO₂ ≤88% on a least one of the 6MWTs. Only 26 patients (30%) demonstrated consistency in meeting the criteria for ambulatory oxygen set forth by the CMS on all three 6MWT with a κ statistic of 0.62. The percent agreement between 6MWTs for ambulatory oxygen prescription was 72% and the paired observation was 51%. Conclusions: The 6MWT distance is simple and widely used as a consistent measure of functional capacity in patients with COPD; however, the 6MWT oxygen saturation has only modest reproducibility in determining the need for ambulatory oxygen in stable COPD patients undergoing pulmonary rehabilitation.

Association of Gastroesophageal Reflux and O2 Desaturation: A Novel Study of Simultaneous 24-h MII–pH and Continuous Pulse Oximetry

BackgroundProof of the relationship between gastroesophageal reflux disease (GERD) and respiratory symptoms remains a challenge. Our aim was to determine the association between reflux events and O2 desaturation in GERD patients with primary respiratory symptoms (RS) compared to those with primary esophageal symptoms (ES) using ambulatory monitoring systems. MethodsOne thousand eight hundred fifty-one reflux episodes were detected by multichannel intraluminal impedance (MII)–pH testing in 30 patients with symptoms of GERD (20 RS, ten ES.) All patients underwent simultaneous 24-h MII–pH and continuous O2 saturation monitoring via pulse oximetry. Reflux-associated desaturation events were determined by correlating synchronized 24-h esophageal pH and/or impedance and O2 desaturation. ResultsOne thousand one hundred seventeen reflux events occurred in patients with RS and 734 in those with ES. Nearly 60% of these 1,851 reflux events were associated with O2 desaturation. Markedly more events were associated with O2 desaturation in patients with RS (74.5%, 832/1,117) than in patients with ES (30.4%, 223/734, p < 0.0001). The difference in reflux desaturation association was more profound with proximal reflux—80.3% with RS vs. 29.4% with ES (p < 0.0001). ConclusionsA remarkably high prevalence of O2 desaturation associated with gastroesophageal reflux was noted in patients with RS. Given further study, simultaneous combined esophageal reflux and O2 saturation monitoring may prove a useful diagnostic tool in this difficult group of patients.

Perioperatives Management der obstruktiven Schlafapnoe

There is lack of studies investigating procedures aiming at a decrease in perioperative mortality in patients with obstructive sleep apnoea (OSA). During anesthetic evaluation, identification of patients with OSA as well as using a risk score has been recommended by the American Society of Anesthesiology in order to identify the best perioperative strategy. Perioperative attention should be focused on a secure airway and the duration of monitoring that is necessary regarding severity of OSA, surgical stress and respiratory function. Postoperatively, residual neuromuscular blockade and a supine position have to be avoided. Continuous pulse oximetry should be used as long as patients remain at increased risk and should be applied until oxygen saturation remains above 90% with room air during sleep. Opioids should be excluded for pain management whenever possible, and CPAP or NIPPV should be administered as soon as feasible after surgery to patients who have been receiving it preoperatively.

Practice guidelines for the prevention, detection, and management of respiratory depression associated with neuraxial opioid administration.

Practice guidelines for the prevention, detection, and management of respiratory depression associated with neuraxial opioid administration.

Episodic nocturnal hypoxia and nasal packs

Nasal obstruction influences respiration during sleep and nasal packs may cause obstructive sleep apnoea. In order to investigate this, the perioperative oxygen saturation was monitored for 3 nights with continuous pulse oximetry in 12 patients, who had bilateral nasal packs after septoplasty. A significant increase in the number of nocturnal episodes of hypoxia and a significant prolongation of the mean duration of the individual hypoxic periods were demonstrated during the first and the second post-operative nights. The clinical significance of these results is as yet unknown, but the use of partial nasal packing in septoplasty is advocated. Further investigations of nocturnal oxygen desaturation and design of nasal packs, securing the post-operative nasal airway, are needed.

Emergency management of fat embolism syndrome.

Fat emboli occur in all patients with long-bone fractures, but only few patients develop systemic dysfunction, particularly the triad of skin, brain, and lung dysfunction known as the fat embolism syndrome (FES). Here we review the FES literature under different subheadings.The incidence of FES varies from 1–29%. The etiology may be traumatic or, rarely, nontraumatic. Various factors increase the incidence of FES. Mechanical and biochemical theories have been proposed for the pathophysiology of FES. The clinical manifestations include respiratory and cerebral dysfunction and a petechial rash. Diagnosis of FES is difficult. The other causes for the above-mentioned organ dysfunction have to be excluded. The clinical criteria along with imaging studies help in diagnosis. FES can be detected early by continuous pulse oximetry in high-risk patients. Treatment of FES is essentially supportive. Medications, including steroids, heparin, alcohol, and dextran, have been found to be ineffective.

Medical Malpractice and the Chest Physician

The US malpractice system is based on tort law, which holds physicians responsible for not harming patients intentionally or through negligence. Malpractice claims are brought against physicians from most medical disciplines in proportion to their numbers in practice and to the frequency with which they perform procedures. Claims against chest physicians most commonly allege injuries caused by the following: (1) errors in diagnosis, (2) improper performance of procedures, (3) failure to supervise or monitor care, (4) medication errors, and (5) failure to recognize the complications of treatment. Most of these injuries occur in hospitals, and many of the injured patients die. The social goals of the medical malpractice system include the following: (1) compensating patients injured through negligence, (2) exacting corrective justice, and (3) deterring unsafe practices by creating an economic incentive to take greater precautions. Some patients injured through negligence are compensated, but most are not. Claims are brought against some negligent physicians but also some who are not negligent, and being negligent does not guarantee that a claim will be brought. The deterrent effect of medical malpractice is unproven, and the malpractice system may prompt defensive medicine and increase health-care costs. And by stressing individual accountability, it conflicts with a systems-oriented approach to reducing medical errors.

Poor Agreement between Respiratory Variations in Pulse Oximetry Photoplethysmographic Waveform Amplitude and Pulse Pressure in Intensive Care Unit Patients

To identify fluid responsiveness, a correlation between respiratory variations in pulse pressure (DeltaPP) and respiratory variations in pulse oximetry photoplethysmographic waveform amplitude (DeltaPOP) in mechanically ventilated patients has been demonstrated. To evaluate the agreement between the two methods, knowledge about the repeatability of the methods is imperative. However, no such data exist. Based on knowledge of slow oscillation in skin blood flow, the authors hypothesized that the variability of DeltaPOP would be larger than that of DeltaPP when calculations were performed continuously over a long recording period. Respiration, continuous invasive blood pressure, pulse oximetry, and skin microcirculation were recorded in 14 mechanically ventilated intensive care unit patients. No intravenous fluid challenges were given, and no other interventions were performed during the measurements. Seventy consecutive comparisons between DeltaPP and DeltaPOP were calculated for each of the 14 patients. For all patients, DeltaPOP was 13.7 +/- 5.8% and DeltaPP was 5.8 +/- 2.6% (P < 0.001). There was a larger intraindividual (8.94 vs. 1.29; P < 0.001) and interindividual (26.01 vs. 5.57; P < 0.001) variance of DeltaPOP than of DeltaPP. In six patients, there was no significant correlation between DeltaPP and DeltaPOP. A Bland-Altman plot showed poor agreement between the two methods. A large variability of DeltaPOP and a poor agreement between DeltaPP and DeltaPOP limits DeltaPOP as a tool for evaluation of fluid responsiveness in intensive care unit patients. This is in contrast to DeltaPP, which shows a small variability.

Dynamic Changes of Left Ventricular Performance and Left Atrial Volume Induced by the Mueller Maneuver in Healthy Young Adults and Implications for Obstructive Sleep Apnea, Atrial Fibrillation, and Heart Failure

Using the Mueller maneuver (MM) to simulate obstructive sleep apnea (OSA), our aim was to investigate acute changes in left-sided cardiac morphologic characteristics and function which might develop with apneas occurring during sleep. Strong evidence supports a relation between OSA and both atrial fibrillation and heart failure. However, acute effects of airway obstruction on cardiac structure and function have not been well defined. In addition, it is unclear how OSA might contribute to the development of atrial fibrillation and heart failure. Echocardiography was used in healthy young adults to measure various parameters of cardiac structure and function. Subjects were studied at baseline, during, and immediately after performance of the MM and after a 10-minute recovery. Continuous heart rate, blood pressure, and pulse oximetry measurements were made. During the MM, left atrial (LA) volume index markedly decreased. Left ventricular (LV) end-systolic dimension increased in association with a decrease in LV ejection fraction. On release of the maneuver, there was a compensatory increase in blood flow to the left side of the heart, with stroke volume, ejection fraction, and cardiac output exceeding baseline. After 10 minutes of recovery, all parameters returned to baseline. In conclusion, sudden imposition of severe negative intrathoracic pressure led to an abrupt decrease in LA volume and a decrease in LV systolic performance. These changes reflected an increase in LV afterload. Repeated swings in afterload burden and chamber volumes may have implications for the future development of atrial fibrillation and heart failure.

M1524 Association of Gastroesophageal Reflux and O2 Desaturation in Patients with GERD; a Novel Study of Simultaneous 24-Hour Impedance-pH and Continuous Pulse-Oximetry

M1524 Association of Gastroesophageal Reflux and O2 Desaturation in Patients with GERD; a Novel Study of Simultaneous 24-Hour Impedance-pH and Continuous Pulse-Oximetry

INTERNAL JUGULAR VEIN VALVE INSUFFICIENCY IN COUGH SYNCOPE

A 53-year-old man with chronic obstructive pulmonary disease (COPD) and obstructive sleep apnea was admitted to the hospital for the evaluation of recurrent syncopal episodes induced by paroxysmal cough. Loss of consciousness was brief, and preceded by the sensation of “fullness in the head.” Syncope was provoked also by prolonged expiration during spirometry, which revealed severe bronchial obstruction. However, oxygen saturation on room air and blood gases were within normal limits. To reproduce reported symptoms, the Valsalva maneuver (VM) was performed with the patient in the supine position with noninvasive, continuous blood pressure monitoring (Finapres, Ohmeda) and finger pulse oximetry. This resulted in a brief loss of consciousness, although no desaturation, decrease in blood pressure, or bradycardia was noted. Transthoracic echocardiography revealed normal left and right ventricular function, mild tricuspid insufficiency, and no evidence of pulmonary hypertension. There was no right-to-left shunt detected on the bubble-contrast study. Neurologic assessment, MRI of the brain, and EEG were unremarkable. Duplex-Doppler examination of extracranial carotid and vertebral arteries showed no stenosis. However, evaluation of the internal jugular veins (IJVs) with the use of color Doppler revealed right internal jugular valve insufficiency with flow reversal during inspiration (figure …

Round and round we go: sedation – what is it, who does it, and have we made things safer for children?

In this issue of Pediatric Anesthesia several papers and commentaries authored by anesthesiologists and nonanesthesiologists describe different perspectives regarding sedation ⁄ analgesia for children in the UK and the USA. I will provide historical perspectives from the USA and then examine these reports to see how they compare with current USA practice. I had the good fortune of being the co-author of the first Sedation Guideline (pediatric or adult) supported by any organization. This initial attempt at providing guidance for a systematic and safe approach to procedural sedation was a result of a number of sedation accidents in children undergoing dental procedures. We worked closely with our pediatric dental colleagues and developed joint guidelines (1,2). Unfortunately we adopted terminology that had been approved by the National Institutes of Health, i.e., the phrase conscious sedation (3). This resulted in much confusion particularly since the intended appropriate (purposeful) response to physical stimulus or verbal command was often miss-interpreted to mean any movement at all in response to any stimulus including painful stimuli! As time passed the American Academy of Pediatrics (AAP) recognized that sedation was provided by many specialists besides dental practitioners so the original guideline was revised in 1992 (4). A special emphasis was placed on a systems approach modeled after our specialty (anesthesiology). Points of interest included: (i) informed consent (parents needed to know that sedative ⁄ analgesics can cause harm); (ii) a presedation history was required (how would the child s underlying medical conditions affect the safety of sedation?); (iii) a focused airway examination (was there an airway abnormality or large tonsils that might affect airway patency or complicate airway management?); (iv) proper fasting prior to elective procedures and the need to balance the risk of sedation in children who required urgent or emergent procedures was described; (v) appropriate monitoring especially continuous pulse oximetry during the procedure and into the recovery period was required for the first time; (vi) appropriate monitoring by an independent observer whose only responsibility was to watch the patient was required during deep sedation; (vii) appropriate staffing and monitoring were required during recovery; and (viii) the children had to be returned to their presedation level of consciousness prior to discharge. With this 1992 revision, the dental community separated from the AAP and published their own specialty specific guideline which deviated significantly from that of the AAP (5–7). In 2002, the AAP published an addendum so that the AAP, the American Society of Anesthesiologists (ASA) and the Joint Commission of Accreditation of Healthcare Organizations all used the same terminology. The phrase conscious sedation was changed to sedation ⁄ analgesia and then changed again to moderate sedation (8,9). Children sedated in all venues including private offices were considered to fall under these guidelines. In particular, the updated guideline states that children aged <6 years usually require a state of pharmacologic coma, i.e., deep sedation to successfully complete most procedures without major psychologic trauma to both provider or child. A clear emphasis was made that sedative medications were only to be administered under the safety net of medical supervision (no home Pediatric Anesthesia 2008 18: 3–8 doi:10.1111/j.1460-9592.2007.02403.x

Pulse Transit Time as a Screening Test for Pediatric Sleep-Related Breathing Disorders

To evaluate a noninvasive measure of arousal, the pulse transit time (PTT), as a screening tool for obstructive sleep apnea/hypopnea syndrome (OSAHS) in an unselected population of symptomatic children, compared with overnight polysomnography (PSG). A secondary objective included comparing the diagnostic performance of PTT with continuous pulse oximetry recorded during PSG. Prospective, blinded diagnostic comparison study using the gold standard of overnight PSG. Tertiary-care children's hospital sleep laboratory. An unselected, volunteer sample of 59 patients (mean age, 7.8 years) with and without adenotonsillar tissue undergoing PSG and simultaneous PTT, including patients with obesity and craniofacial syndromes. The relationship between the PTT and polysomnographic measures of OSAHS to include pulse oximetry using correlation coefficients and receiver operating characteristic curve analysis. The correlation coefficient between the PTT arousal index and PSG apnea-hypopnea index (AHI) was 0.70 (P<.001). Linear regression resulted in a good fit (R2=0.73) between PTT arousal index and AHI. With the use of an AHI of 1 or greater (35.6% prevalence of OSAHS) as a criteria for OSAHS, the area under the receiver operating characteristic curve was 0.86 (95% confidence interval, 0.76-0.96). The optimal PTT arousal index threshold was 5.4 events per hour, which translated into a sensitivity of 81% and a specificity of 76%. The PTT arousal index is highly correlated with the PSG-derived AHI and demonstrated excellent diagnostic utility for moderate and severe OSAHS. However, for mild OSAHS, PTT was barely adequate and did not significantly outperform pulse oximetry. Pulse transit time may be a useful tool to evaluate moderate to severe sleep-related breathing disorders in children.

MTP8-01: Percutaneous radiofrequency ablation of malignant thoracic tumors

MTP8-01: Percutaneous radiofrequency ablation of malignant thoracic tumors

Is intravenous conscious sedation for surgical orthodontics in children a viable alternative to general anaesthesia? – a case review

The aim of this case review was to describe the use of local anaesthesia (LA) and intravenous conscious sedation (IVCS) as a safe and effective means of managing patients requiring surgical orthodontic procedures as an alternative to general anaesthesia (GA) in children between the age of 11 and 15 years. 1) Whether treatment was completed, partially completed or not completed; 2) assessment of physiological parameters to verify safety profile of the technique. Records were reviewed retrospectively for all patients included in the series undergoing planned surgical orthodontic procedures between January 2001 and January 2004 under IVCS. All patients had been pre-assessed and deemed to be of sufficient mental and physical maturity to be treated with IVCS. Written informed consent was gained from patients and their parents/guardians with full discussion of the alternative pain and anxiety control methods available including GA. All cases were undertaken by experienced SAS grade surgeons assisted by two dental nurses holding the certificate in dental sedation nursing and their recovery was supervised by registered general nurses. Patients were clinically monitored throughout together with continuous pulse oximetry and intermittent recording of non invasive blood pressure and pulse at 10-15 minute intervals. Patients were reviewed post operatively and any complications or comments noted. Over a three year period a total of 107 patients underwent surgical procedures to aid orthodontic treatment, 28 (26%) under IVCS and 79 (74%) under GA. Twenty-five out of 28 patients in the IVCS group successfully completed all of their planned treatment. Based on this case series, IVCS would appear to offer a safe and effective alternative to GA for this group of patients providing they are selected and managed by an appropriately trained team in a suitable setting. Further prospective evidence is needed if IVCS is to be recommended for general dental treatment in patients under the age of 16 years.