Presence Of Supplemental Oxygen Research Articles

Conducted Electrical Weapon Fire Risk in the Presence of Supplemental Oxygen.

Conducted electrical weapons (CEWs) are nonlethal weapons used in tactical environments. Tactical EMS (TEMS) operators provide patient care in environments where CEWs are present. CEWs may produce a spark that can be a source of ignition. When supplemental oxygen is in use by a TEMS operator, the flammability risk from the CEW is unknown. We measured oxygen levels over 20 minutes in an enclosed space with a supplemental oxygen source maximally flowing. Measurements were taken at various distances from the oxygen source to establish baseline concentrations. These concentrations were replicated within a plexiglass box where a CEW was activated to create a sparking arc between probes embedded in a fresh swine shoulder (with skin intact). Various flammable materials, typically found in a patient care setting were used as potential fuel sources. The highest oxygen levels were achieved directly at the source. At 15cm from the source, the maximum oxygen concentration was 31.5%. Within the box, ignition was only achieved at oxygen concentrations greater than 45% and only when human hair was present as fuel. No ignition was achieved at oxygen levels below this regardless of the tested fuel present. Ignition from a CEW is possible at supplemental oxygen levels greater than 45% when human hair is present. In an enclosed space, oxygen concentration levels of 45% are only present within 15cm of a flush rate oxygen source. The likelihood of CEW-caused ignition in such settings with supplemental oxygen in use is extremely low.

The impact of capnography monitoring among children and adolescents in the postanesthesia care unit: a randomized controlled trial.

Pulse oximetry does not reliably recognize respiratory depression, particularly in the presence of supplemental oxygen. Capnography frequently detects hypoventilation and apnea among children recovering from anesthesia. Although children are routinely monitored with capnography during anesthesia, reducing the rate of adverse events, it is not routinely used in the postanesthesia care unit (PACU), where patients remain at risk for respiratory depression. We hypothesized that children monitored with capnography would have more frequent staff interventions and fewer adverse events than children monitored with pulse oximetry alone. Otherwise healthy children of age 1-20 years undergoing general anesthesia for elective surgery were eligible for enrollment upon entering the pediatric PACU. Subjects were randomized as to whether PACU staff could view the capnography monitor (intervention group) or not (control group). All children received standard monitoring with pulse oximetry. Vital signs and patient interventions were recorded every 30 s by a portable monitor or a research associate. Data from 201 children were analyzed. The rates of hypopneic hypoventilation [5% (95% CI: 2-8%) per minute vs 1% (95% CI: -1% to 3%) per minute, difference 4% (95% CI: 0.2-8%) per minute; P = 0.04] and apnea [11% (95% CI: 8-14%) per minute vs 1.5% (95% CI: -2% to 5%) per minute, difference 9% (5-14%) per minute; P < 0.001] decreased significantly faster in our intervention group as compared to the control group. The rates of bradypnea decreased faster in our control group [5% (95% CI: 2-8%) per minute vs 1% (95% CI: 0-4%) per minute, difference 4% per minute, 95% CI: 0-9%; P = 0.05]. Rates of respiratory events over time between groups were affected by the presence or absence of interventions. There were no differences in rates of hypoxemia between groups over time. Children monitored with capnography have different rates of adverse respiratory events over time than children monitored solely with pulse oximetry. The addition of capnography improved the efficacy of staff interventions, however did not impact rates of oxygen desaturation.

Respiratory depression detected by capnography among children in the postanesthesia care unit: a cross-sectional study.

Children are at risk for respiratory depression while recovering from anesthesia. Currently, monitoring children in the postanesthesia care unit (PACU) with pulse oximetry is recommended. However, pulse oximetry does not reliably recognize hypoventilation or apnea, particularly in the presence of supplemental oxygen. Capnography is a sensitive monitor of ventilation that is not often used in the PACU. To determine the frequency of hypoventilation and apnea as detected by capnography among children in the PACU. In a cross-sectional study, capnography monitoring was applied to healthy children of age 1-17 years in the PACU of a tertiary care hospital. Staff was blinded to the capnography monitor; alarms were disabled. Staff provided routine care and monitoring with pulse oximetry to all patients. Vital signs, patient interventions, and medication administration were recorded by a research assistant every 30 s until all monitoring was discontinued by staff. Outcome measures included frequency of hypoventilation and apnea as measured by capnography and oxygen desaturations as measured by pulse oximetry, as well as staff interventions for these events. Data from 194 children were analyzed. Capnography detected hypoventilation or apnea in 45.5% (95% CI 38.5%, 52.5%) of patients. Oxygen desaturations occurred in 19% (95% CI 13%, 24%) of patients. Interventions occurred in 9% (95% CI 5%, 13%) of patients. Patients who received narcotic medications were more likely to experience hypoventilation (OR 2.3, 95% CI 1.02, 5.3) and apnea (OR 2.7, 95% CI 1.1, 7). Hypoventilation was seen more often among children who received supplemental oxygen (OR 3.1, 95% CI 1.1, 12). Hypoventilation and apnea are common among children in the PACU; however, few interventions occur to address these events. Routine monitoring with capnography may improve recognition of respiratory depression and enhance patient safety in the PACU.

Mobile Phone-Triggered Thermal Burns in the Presence of Supplemental Oxygen

In this case report, we present a patient who used a nasal cannula for oxygen supplementation and suffered deep, second-degree burns to his nose and left leg when an electrical spark shot out of the cable's connection socket while the cellular phone was ringing and the cable was, simultaneously, being disconnected from the socket. The cellular phone, a device commonly thought by many people to be both useful and safe, thus has the potential to serve as a heat source that might ignite and cause burns.

End-tidal carbon dioxide monitoring during flexible fiberoptic bronchoscopy

In recent years, flexible fiberoptic bronchoscopy (FFB) has been applied for diagnostic and some therapeutic purposes. During FFB and even in the presence of supplemental oxygen, hypoventilation leading to hypoxia and desaturation may occur; this is aggravated by the use of suction. Arterial oxygen saturation is usually monitored with pulse oximetry Spo2) during FFB; END-TIDAL Pco2) (ET-Pco2) monitoring is not routinely used. Two-hundred patients were studied between May 1998 till April 2003, at the divisions of chest surgery and pulmonolgy at King Hussein Medical Center, (khmc). Their ages were 53±19 years (mean±SD). They underwent FFB and received supplemental oxygen during various stages of FFB: 1-before and during instillation of hdocaine on the vocal cords, 2-during passage of instrument into the trachea, RMB, IMB, 3-during bronchoalveolar lavage, bronchial biopsy, transbronchial biopsy (TBB), and 4-at the final stages of FFB, ET- Pco2 significantly decreased from Spo2 using a pulse oximeter simultaneously and the results were recorded. Mean ET-Pco2 significantly decreased from 28.7±4.5 mmHg before FFB to 28±5.7 mmHg, 27±5.5 mmHg, 27.5±5.6 mmHg, 27.1±4.5 mmHg, 27.9±5.3 mmHg during bronchoscopy of the right main bronchus (RMB), left main bronchus (LMB), bronchial washing, bronchial biopsy and transbronchial biopsy (TBB), and at the termination of FFB, respectively (p

Microstream Capnography Improves Patient Monitoring During Moderate Sedation: A Randomized, Controlled Trial

Investigative efforts to improve monitoring during sedation for patients of all ages are part of a national agenda for patient safety. According to the Institute of Medicine, recent technological advances in patient monitoring have contributed to substantially decreased mortality for people receiving general anesthesia in operating room settings. Patient safety has not been similarly targeted for the several million children annually in the United States who receive moderate sedation without endotracheal intubation. Critical event analyses have documented that hypoxemia secondary to depressed respiratory activity is a principal risk factor for near misses and death in this population. Current guidelines for monitoring patient safety during moderate sedation in children call for continuous pulse oximetry and visual assessment, which may not detect alveolar hypoventilation until arterial oxygen desaturation has occurred. Microstream capnography may provide an "early warning system" by generating real-time waveforms of respiratory activity in nonintubated patients. The aim of this study was to determine whether intervention based on capnography indications of alveolar hypoventilation reduces the incidence of arterial oxygen desaturation in nonintubated children receiving moderate sedation for nonsurgical procedures. We included 163 children undergoing 174 elective gastrointestinal procedures with moderate sedation in a pediatric endoscopy unit in a randomized, controlled trial. All of the patients received routine care, including 2-L supplemental oxygen via nasal cannula. Investigators, patients, and endoscopy staff were blinded to additional capnography monitoring. In the intervention arm, trained independent observers signaled to clinical staff if capnograms indicated alveolar hypoventilation for >15 seconds. In the control arm, observers signaled if capnograms indicated alveolar hypoventilation for >60 seconds. Endoscopy nurses responded to signals in both arms by encouraging patients to breathe deeply, even if routine patient monitoring did not indicate a change in respiratory status. Our primary outcome measure was patient arterial oxygen desaturation defined as a pulse oximetry reading of <95% for >5 seconds. Secondary outcome measures included documented assessments of abnormal ventilation, termination of the procedure secondary to concerns for patient safety, as well as other more rare adverse events including need for bag-mask ventilation, sedation reversal, or seizures. Children randomly assigned to the intervention arm were significantly less likely to experience arterial oxygen desaturation than children in the control arm. Two study patients had documented adverse events, with no procedures terminated for patient safety concerns. Intervention and control patients did not differ in baseline characteristics. Endoscopy staff documented poor ventilation in 3% of all procedures and no apnea. Capnography indicated alveolar hypoventilation during 56% of procedures and apnea during 24%. We found no change in magnitude or statistical significance of the intervention effect when we adjusted the analysis for age, sedative dose, or other covariates. The results of this controlled effectiveness trial support routine use of microstream capnography to detect alveolar hypoventilation and reduce hypoxemia during procedural sedation in children. In addition, capnography allowed early detection of arterial oxygen desaturation because of alveolar hypoventilation in the presence of supplemental oxygen. The current standard of care for monitoring all patients receiving sedation relies overtly on pulse oximetry, which does not measure ventilation. Most medical societies and regulatory organizations consider moderate sedation to be safe but also acknowledge serious associated risks, including suboptimal ventilation, airway obstruction, apnea, hypoxemia, hypoxia, and cardiopulmonary arrest. The results of this controlled trial suggest that microstream capnography improves the current standard of care for monitoring sedated children by allowing early detection of respiratory compromise, prompting intervention to minimize hypoxemia. Integrating capnography into patient monitoring protocols may ultimately improve the safety of nonintubated patients receiving moderate sedation.

Injury and Liability Associated with Monitored Anesthesia Care

To assess the patterns of injury and liability associated with monitored anesthesia care (MAC) compared with general and regional anesthesia, the authors reviewed closed malpractice claims in the American Society of Anesthesiologists Closed Claims Database since 1990. All surgical anesthesia claims associated with MAC (n = 121) were compared with those associated with general (n = 1,519) and regional (n = 312) anesthesia. A detailed analysis of MAC claims was performed to identify causative mechanisms and liability patterns. MAC claims involved older and sicker patients compared with general anesthesia claims (P < 0.025), often undergoing elective eye surgery (21%) or facial plastic surgery (26%). More than 40% of claims associated with MAC involved death or permanent brain damage, similar to general anesthesia claims. In contrast, the proportion of regional anesthesia claims with death or permanent brain damage was less (P < 0.01). Respiratory depression, after absolute or relative overdose of sedative or opioid drugs, was the most common (21%, n = 25) specific damaging mechanism in MAC claims. Nearly half of these claims were judged as preventable by better monitoring, including capnography, improved vigilance, or audible alarms. On-the-patient operating room fires, from the use of electrocautery, in the presence of supplemental oxygen during facial surgery, resulted in burn injuries in 20 MAC claims (17%). Oversedation leading to respiratory depression was an important mechanism of patient injuries during MAC. Appropriate use of monitoring, vigilance, and early resuscitation could have prevented many of these injuries. Awareness and avoidance of the fire triad (oxidizer, fuel, and ignition source) is essential to prevent on-the-patient fires.

13C-Methacetin metabolism in patients with cirrhosis: relation to disease severity, haemoglobin content and oxygen supply.

Hypoxia may contribute to impairment of liver function and thus interfere with results of liver tests. In patients with cirrhosis, cytochrome P-450 mediated metabolism of substrates is facilitated in the presence of supplemental oxygen. It has not been studied how this relates to liver function and haemoglobin content. We questioned how oxygen supplementation would influence the hepatic microsomal function as assessed by the 13C-methacetin breath test in patients with cirrhosis of different severity and different degrees of anaemia. 13C/12C ratios in exhaled breath assessed by non-dispersive infrared spectrometry were studied in 34 patients with cirrhosis (Child A/B/C 9/17/8) after administration of 75 mg 13C-methacetin p.o. with and without oxygen inhalation (4 L/min). In patients breathing room air the total amount of 13C exhaled weakly correlated both with the Child-Pugh score (r = - 0.41, P < 0.02) and haemoglobin concentrations (r = 0.46; p = 0.006). Oxygen supplementation increased the total amount of 13C exhaled by 68 +/- 90% (P < 0.001). This effect was similar in Child-Pugh classes A (43 +/- 55%), B (83 +/- 80%) and C (66 +/- 123%) and not related to the Child-Pugh score. Our results suggest that tests of microsomal liver function are independently influenced both by oxygen delivery and the Child-Pugh score.

Fire hazards and CO2 laser resurfacing.

The purpose of this study was to investigate the fire risk of laser resurfacing in the presence of supplemental oxygen. This study aims at defining safety parameters of variables such as laser energy level, oxygen flow rate, and "oxygen to laser target distance" when oxygen is delivered through a nasal cannula or nasopharyngeal tube. The typical operating room environment was simulated in the laboratory using the Yucatan minipig animal model. The energy source was a Coherent Ultrapulse CO2 laser. It was found that combustion did not occur at laser settings of 500 mJ, 50 W, 100 kHz, and a density of 5, used in conjunction with an oxygen flow rate of 6 liter/minute with the target area as close as 0.5 cm to the oxygen delivery. A total of 400 computer pattern generator treatments were delivered using this energy setting without observation of any combustion (p < 0.001). This provides evidence that while using even somewhat high laser settings and oxygen flow rate, laser induced fires can be avoided. We conclude that use of the laser in the presence of oxygen is safe, provided the target area is free of combustible fuels. Despite this assurance, laser mishaps are serious because they lead to both morbidity and mortality. It is our recommendation that close attention be constantly paid to all details, thus reducing the hazard potential of laser energy on local factors in an oxygen-rich environment.

Oxygen leakage around the laryngeal mask airway during laser treatment of port-wine stains in children.

The flash-lamp pumped pulsed dye laser is the current treatment of choice for cutaneous port-wine stains. In our practice, most children with these lesions are treated under general anesthesia. At energy levels used clinically, it is possible to ignite hair in the presence of supplemental oxygen; we are aware of four cases in which either the eyebrows or eyelashes were ignited during the administration of general anesthesia via a face mask. The laryngeal mask airway (LMA) recently has become widely available and this device might decrease the risk of fire during treatment of these lesions. We therefore designed this study to examine the extent of oxygen leakage under the mask during clinical cases, and to compare this with the leakage present with the LMA. A total of 20 patients aged 4 mo to 16 yr were studied on 26 separate occasions. During spontaneous ventilation, high concentrations of oxygen leaked around the mask in every case (mean 63% +/- 16%), but in only one case was a concentration more than 21% detected around the LMA (P < 0.001). During controlled ventilation with the LMA, oxygen leaked around the mask in 19% of cases. Use of the LMA markedly decreases the incidence of potential oxygen leakage into the laser field, and is recommended for use, with preservation of spontaneous ventilation, during these cases. We suggest measuring oxygen concentrations at the mouth for laser treatment of facial port-wine stains to confirm that the larynx has been isolated.(ABSTRACT TRUNCATED AT 250 WORDS)

Measurement of minute ventilation in ventilator-dependent patients

a) To determine the variation in methods used to measure minute ventilation (VE) in patients who receive mechanical ventilation; b) to determine the effect of supplemental oxygen on VE, respiratory rate (RR), and tidal volume (VT) measurements. Telephone survey of hospitals, and a randomized control trial. Medical and surgical ICUs in a university hospital. Thirty-three patients who had required mechanical ventilation because of the inability to sustain adequate spontaneous ventilation. All patients were considered ready to undergo a weaning trial by their physicians. Spontaneous VE, RR, VT, and SaO2 were measured both in the presence and absence of supplemental oxygen; measurements were obtained in a randomized manner. a) In a telephone survey of hospitals throughout the country, we found that the measurement of VE is variably obtained during room air breathing or in the presence of supplemental oxygen. b) Measurements of VE increased from 11.0 +/- 0.8 L/min while patients received supplemental oxygen to 13.5 +/- 1.1 L/min while patients breathed room air (p less than .001). Of 15 patients who had a VE less than 10 L/min while receiving supplemental oxygen, seven developed a value greater than 10 L/min while breathing room air; thus, a weaning trial might have been inappropriately deferred in these patients. c) Mean SaO2 decreased from 95.0 +/- 0.6% while breathing supplemental oxygen to 90.2 +/- 1.1% while breathing room air (p less than .001). Measurements of VE in patients being considered for a weaning trial can result in significant oxygen desaturation if obtained during room air breathing, and the values obtained can significantly overestimate the patient's true ventilatory requirements, since most patients receive supplemental oxygen during a weaning trial. Standardized methods of measuring VE in critically ill patients need to be developed.