Reactive oxygen species in acute respiratory distress syndrome.

In the metabolism of almost all human cells, a sequential addition of electrons to oxygen leads to the formation of reactive oxygen species (ROS). ROS have been implicated in more than 100 diseases and may be the common denominator in the pathogenesis of the most important health problems facing the world today. The last decade has been characterized by a progressive increase in the understanding of oxidant chemistry and the role of ROS in pulmonary disease. The majority of deaths among critically ill patients are the result of sepsis and its sequelae, including acute respiratory distress syndrome (ARDS). Nurses must understand the processes involving ROS that are in play when they are caring for patients with ARDS. This article describes what is known about the formation of ROS, the pathophysiology of ARDS, and the role ROS play in the pathogenesis of ARDS.

Effects of hypoxia on diaphragm activity in anesthetized rats.

Hypoxia is one of the most common conditions observed by PACU nurses after surgery. It may be caused by a reduced functional residual capacity, hypoventilation, and/or ventilation-perfusion mismatch. Hypoxia can also affect diaphragm contractility, making it difficult to wean postoperative patients from mechanical ventilation. Clinically, however, there is no method to directly measure diaphragm contractility; therefore, indicators of intrathoracic pressure such as tidal volume are used. The purpose of this study was to directly measure the effects of diaphragm shortening in 12 anesthetized Sprague-Dawley rats before, during, and after induced hypoxia. A miniaturized ultrasonic sensor was used to measure changes in diaphragm thickness as an index of diaphragm shortening. A stainless steel electrode was attached adjacent to the ultrasonic sensor and used to measure the electromyogram (EMG) of the diaphragm. After normoxic measurements were recorded, hypoxia was initiated by connecting the tracheal cannula to a latex balloon containing 7.4% oxygen in nitrogen. During the first 5 minutes of hypoxia, diaphragm shortening, EMG, and intrathoracic pressure increased. Over the next 30 to 100 minutes, EMG and intrathoracic pressure remained elevated, whereas diaphragm shortening decreased to 50% of control, which was defined as diaphragm fatigue. The mean time for hypoxia-induced diaphragm fatigue to occur was 63 minutes. These results indicate that hypoxia-induced decline in diaphragm shortening was not caused by a decrease in muscle excitation as measured by EMG. These data suggest that impairment in mechanical-chemical coupling (diaphragm shortening) could be a result of decreased oxygen availability associated with the lower arterial blood oxygen content. Thus, the increase in intrathoracic pressure throughout hypoxia suggests that intrathoracic pressure is not always a consistent index of the contractile state of the diaphragm.

Efficacy and safety of prone positioning for patients with acute respiratory distress syndrome.

This article presents an overview of a literature review on how prone positioning can alleviate pathophysiological changes in ARDS and improve ventilation and perfusion. Improvement of gas exchange, efficiency of oxygenation and lung function are emphasized. Literature on the pathophysiology of ARDS, and the physiological effects of prone positioning on haemodynamics and lung function is examined. There are both advantages and disadvantages in turning a patient from the supine to the prone position. There are also contraindications in rotating between the supine and prone positions. Nevertheless, by rotating patients with ARDS, it is possible to achieve a significant improvement in A-aDO2, decrease shunting, and therefore improve oxygenation without use of expensive, invasive and experimental procedures. Placing patients with ARDS in the prone position can reduce inspiratory oxygen concentrations and peak inspiratory pressures, which minimizes the chance for barotrauma and the iatrogenic effects of hyperventilation oxygen toxicity.

Impact of implementation of an embryo storage fee on embryo disposal activity.

OBJECTIVE: To examine the impact of implementation of a new fee for continued storage of cryopreserved embryos on the rate of requests for disposal of embryos. DESIGN: Retrospective cohort study. SETTING: A university-based assisted reproduction program. PATIENT(S): All patients with cryopreserved embryos. INTERVENTION(S): Implementation of a semiannual embryo storage fee of $100 to cover administrative and laboratory costs. MAIN OUTCOME MEASURE(S): The number of embryo disposal requests before and after implementation of the embryo storage fee was compared in relation to the activity of the cryopreserved embryo program as measured by number of frozen embryo transfers. RESULT(S): Annual requests for embryo disposal from 1992 through 1997 ranged from zero to three, which represented 0-5% of the annual frozen embryo program activity. In contrast, a significantly higher number of disposal requests (10, representing 18% of program activity) were received in 1998. CONCLUSION(S): Fees for storage of cryopreserved embryos seem to influence patients' decisions about disposal of cryopreserved embryos.

Improving naltrexone response: an intervention for medical practitioners to enhance medication compliance in alcohol dependent patients.

The effectiveness of naltrexone, a FDA-approved medication for alcohol dependence, can be improved if we support and help patients to consistently take their medication. We illustrate how patient noncompliance with treatment negatively affects outcome, and, we describe a new intervention to enhance medication compliance. Outcome was evaluated for 196 alcohol dependent outpatients who were treated with 50 mg/day naltrexone or placebo for 12 weeks. For patients who adhered to the prescribed treatment, relapse rates were lower with naltrexone than placebo (10% vs. 38.6%, p < 0.001). For noncompliant patients, relapse rates were high and comparable between naltrexone- and placebo-treated patients (42.9% vs. 40%). In a second study of 100 alcohol dependent outpatients, we introduced an intervention that resulted in better medication compliance rates compared to a previous naltrexone study of patients who did not receive the intervention (77.0% vs. 60.8%, p < 0.01). This provided some support for the use of an intervention that targets medication compliance when prescribing naltrexone.

Effects of pressure support ventilation and continuous positive airway pressure on diaphragm performance.

Many patients who are on mechanical ventilation are on ventilator modes called pressure support ventilation (PSV) and continuous positive airway pressure (CPAP) particularly when they are being weaned. As the diaphragm is responsible for approximately 75% of breathing, it is important to promote diaphragm shortening to optimize weaning from mechanical ventilation. The purpose of our 1998 quasi-experimental study was to explore the effects of PSV and CPVP on diaphragm shortening. An animal model was utilized using four Sprague-Dawley rats from the same litter purchased from Sasco (Kansas City, USA). Also measured in this study were intrathoracic pressure (DeltaITP), positive inspiratory pressure, respiratory rate, tidal volume, end-tidal carbon dioxide, central venous pressure (CVP) and mean arterial pressure (MAP). Pressure support was increased in increments of 5 cm H2O at CPAP levels of 0, 2 and 4 cm H2O. A direct assessment of diaphragm shortening was achieved through the adherence of a miniaturized ultrasonic sensor to the inferior surface of the middle costal surface of the right hemidiaphragm of four Sprague-Dawley rats. Limitations of this study included a small sample size, anaesthetized rats and abdominal dissection for insertion of the ultrasonic sensor. As PSV was increased, there was a decrease in MAP, CVP, respiratory rate and end-tidal CO2. When increasing levels of CPAP were added to PSV, a decrease in diaphragm shortening was observed. These results support that higher levels CPAP may hinder diaphragmatic function thus prolong mechanical ventilation. The purpose of this pilot study was to explore the effects of PSV and CPAP on diaphragm shortening. Also measured were DeltaITP, positive inspiratory pressure, respiratory rate, tidal volume, end-tidal carbon dioxide, CVP and MAP. Pressure support was increased in increments of 5 cm H2O at CPAP levels of 0, 2 and 4 cm H2O. A direct assessment of diaphragm shortening was achieved through the adherence of a miniaturized ultrasonic sensor to the inferior surface of the middle costal surface of the right hemidiaphragm of four Sprague-Dawley rats. Limitations of this study included a small sample size, anaesthetized rats and abdominal dissection for insertion of the ultrasonic sensor. As PSV was increased, there was a decrease in MAP, CVP, respiratory rate and end-tidal CO2. When increasing levels of CPAP were added to PSV, a decrease in diaphragm shortening was observed.

Effects of positive end-expiratory pressure on diaphragm function.

Patients admitted to the PACU after surgery may require mechanical ventilation. Knowledge about the anatomy and physiology of the diaphragm and its association with ventilator modes may be helpful in the management of this patient. As the acuity of PACU patients increase, more patients may also be on higher levels of positive end-expiratory pressure (PEEP), requiring PACU nurses to understand the relationship between PEEP and diaphragm function to facilitate weaning. This article provides a review of the mechanical ventilation mode of PEEP and its relationship to diaphragmatic performance. The physiological effects associated with the use of PEEP are also reviewed.

The relationship of Axis II personality disorders to other known predictors of addiction treatment outcome.

This study evaluated the prevalence of Axis II disorders in substance abuse patients and the relationship between Axis II psychopathology and two other known predictors of adverse addiction treatment outcomes, i.e., Axis I psychiatric comorbidity and illegal drug use, specifically cocaine. 232 patients with cocaine and/or alcohol dependence were admitted to either inpatient or outpatient addiction recovery programs at Carrier Foundation, a nonprofit, private-pay hospital in New Jersey. Axis II disorders were more prevalent in cocaine than alcohol dependence and in patients with Axis I psychiatric comorbidity. When all three predictors were evaluated in one prediction model, the combination of Axis I and II psychopathology was the best predictor of a return to substance use at one year post-treatment, compared to the three factors alone. These findings highlighted the importance of the interrelationship of the relative prognostic value of three known predictors of addiction treatment.

Effects of volume control, pressure control, and pressure-regulated volume control on cardiopulmonary parameters in a normal rat lung.

The purpose of this study was to investigate the differences in diaphragm shortening and cardiopulmonary parameters at varying tidal volumes during volume control (VC), pressure control (PC), and pressure-regulated volume control (PRVC). A miniaturized ultrasonic sensor attached to the inferior surface of the upper costal surface of the right hemidiaphragm of 16 Sprague-Dawley rats provided a direct assessment of diaphragm shortening. Within each control mode of mechanical ventilation, the tidal volume was increased from 3 to 12 ml in increments of 3 ml. There were no differences in cardiac output, mean arterial pressure, central venous pressure, peak inspiratory pressure, or end-tidal CO2 among the three modes of mechanical ventilation. At equivalent tidal volumes, diaphragm shortening was less during PRVC than during VC or PC. This finding suggests that differences in diaphragm shortening may be caused by shorter resting (end-expiratory) diaphragm muscle length. The cardiopulmonary data obtained in this study provide new information for clinicians to consider when using various modes of ventilation, particularly PRVC.

Gambling and other risk behaviors among 8th- to 12th-grade students.

OBJECTIVE: To examine the associations between a self-reported history of gambling or problems related to gambling and health risk behaviors in adolescence. DESIGN: An anonymous risk behavior survey was administered to 21 297 8th- through 12th-grade students in 79 public and private schools in Vermont. Gambling or problems related to gambling were the outcome variables of interest. Demographic variables and 13 target risk behaviors related to substance use, sexual activity, and violence were tested for association with gambling and problems related to gambling. RESULTS: Of the students, 53% reported gambling in the past 12 months, and 7% reported problems attributable to gambling. Male gender, any use of alcohol, infrequent use of cigarette smoking, any marijuana use, any inhalant use, infrequent steroid use, frequent illegal drug use, seatbelt nonuse, driving after drinking alcohol, being threatened, carrying a weapon, being involved in a fight, and years of sexual activity were all significantly associated with reported gambling in the past 12 months. Among the students who gambled, younger age, male gender, daily marijuana use, frequent use of cocaine, frequent use of inhalants, any steroid use, never wearing seatbelts, carrying a weapon for up to 3 days a month, fighting, and years of sexual activity were all significantly associated with reported problems with family and friends as a consequence of gambling. There was an increase in the absolute number of risk behaviors reported between those who had not gambled, those who had gambled, and those for whom gambling had created problems. CONCLUSIONS: Risk behaviors are associated with gambling in adolescence. The typology of risk behaviors was different for adolescents who reported gambling compared with those for whom gambling had created problems. Both gambling and problems related to gambling were significantly associated with the absolute number of risk behaviors reported by adolescents in a graded manner. Involvement in gambling should be assessed as part of the health encounter. Assessment may provide a nonthreatening entry into the evaluation of other risk behaviors. Furthermore, it may identify youth who are at risk of developing additional risk behaviors or pathological gambling. Interventions then could be targeted toward prevention of these undesirable outcomes.

Diaphragm shortening and intrathoracic pressure during hypercapnia in rats.

The purpose of this study was to determine the relationship between intrathoracic pressure (delta ITP) and diaphragm shortening (DS) during the development of diaphragm fatigue. Fatigue of the diaphragm was produced by having rats breath 15% CO2 in O2. Diaphragm shortening increased significantly to 178% of control during the first 5 min of hypercapnia and then decreased to 86% of control at approximately 80 min. Twenty minutes after terminating hypercapnia, DS increased to 115% of the prehypercapnic value. delta ITP increased to 199% of control following 5 min of hypercapnia and continued to increase, reaching 267% of control at the end of the hypercapnic period. Twenty minutes later, delta ITP was 147% of control. These results illustrate that during increased respiratory work, DS can decrease while intrathoracic pressure remains increased. These findings suggest that intrathoracic pressure may not always reflect the contractile status of the diaphragm. These findings are consistent with other studies indicating that as the diaphragm fatigues, accessory respiratory muscle activity increases to maintain delta ITP.

Gender differences in risk behaviors associated with forced or pressured sex.

OBJECTIVE: To determine whether gender-specific patterns of risk behaviors are associated with a self-reported history of ever having been forced or pressured to have sexual intercourse among sexually active adolescents. SUBJECTS AND METHODS: In 1995, 21,297 eighth- through 12th-grade students in 79 public and private schools in Vermont were anonymously surveyed. Data were analyzed for 7884 sexually active students (3931 girls and 3953 boys). Demographic variables and indicators of violence, suicide, recent substance use, sexual behavior, pregnancy, and weight control behavior were assessed. Data were analyzed with multiple logistic regression. RESULTS: Of the sexually active students, 30.3% of the girls and 9.9% of the boys reported ever being forced or pressured to have sexual intercourse. Among sexually active girls, being in 1 or more physical fights in the past year (odds ratio [OR], 1.65; 95% confidence interval [CI], 1.40-1.94), seriously considering suicide (OR, 1.97; CI, 1.69-2.31), more years of sexual activity (OR, 1.52; CI, 1.43-1.61), not using a condom at last sexual intercourse (OR, 1.28; CI, 1.09-1.49), and having been pregnant more often (OR, 1.40; CI, 1.16-1.69) were associated with having been forced or pressured to have sex. For sexually active boys, seriously considering suicide (OR, 1.64; CI, 1.23-2.20), more years of sexual activity (OR, 1.21; CI, 1.12-1.31), more male partners in the past 3 months (OR, 1.30; CI, 1.14-1.48), more female partners in the past 3 months (OR, 1.09; CI, 1.01-1.18), not using a condom at last sexual intercourse (OR, 1.37; CI, 1.03-1.82), having been involved in more pregnancies (OR, 1.64; CI, 1.29-2.08), and having vomited or used laxatives (OR, 3.44; CI, 2.18-5.43) were associated with having been forced or pressured to have sex. CONCLUSIONS: Patterns of risk behaviors differed among sexually active male and female adolescents reporting being forced or pressured to have sex. Having been forced or pressured to have sex was associated with externalizing behavior, such as fighting, among girls and with internalizing behavior, such as bulimia, among boys. These unexpected associations have notable implications for screening adolescents for a history of having been forced or pressured to have sex.

Gender differences in comorbidly depressed alcohol-dependent outpatients.

UNLABELLED: Clinical profiles of alcohol-dependent male and female outpatients were evaluated at treatment entry to compare the level of clinical severity in alcoholics with a coexistent comorbid depressive disorder to alcoholics who have never been depressed. Due to a higher proportion of females than males in the depressed alcoholic population, selected patient groups were oversampled to create a study group with equivalent number of males and females with and without comorbid depression. Clinical severity was assessed by examining both the extent of alcohol problems, and depressive symptomatology at treatment entry with respect to gender differences (unrelated to depression), effects of comorbid depression (unrelated to gender), and effects from the interaction of gender and depression. There were 93 DSM-III-R alcohol-dependent outpatients (50 males, 43 females), half of whom had a current or lifetime DSM-III-R depressive disorder. The amount of drinking in the 90 days before treatment entry, the degree of alcohol severity, and the number of lifetime drinking-related consequences were collected in the first week after detoxification. Diagnoses of lifetime and current depression were determined via the Structured Clinical Interview for DSM-III-R, and depressive symptoms were evaluated with rating scales 1 week after detoxification. In most cases, a depressive disorder was diagnosed only if sometime in the patient's history depressive symptoms had either predated problem drinking or been present during a 6-month abstinent period. RESULTS: depressed males had a more severe clinical profile with respect to their alcoholism (i.e., more drinking, drinking-related problems, and alcohol severity than depressed females and never-depressed males). Surprisingly, females who had never been depressed (also no family history of depression) reported drinking the same quantities of alcohol in the 90 days before treatment and had comparable alcohol severity and number of consequences as males who had never been depressed. Depressed females, however, were more severely depressed (i.e., reported more intensive depressive symptoms than depressed male alcoholics). Thus, determining the type and extent of clinical severity at treatment entry in comorbidly depressed alcoholics depends on the gender of the patient The significant interaction between gender and the presence of comorbid depression that was found in this study may have important implications for predicting success in treatment.

Analysis of position of trial sequence and type of diluent on the detection threshold for phenyl ethyl alcohol using a single staircase method.

Although detection thresholds for odors are commonly measured in academic and medical settings, the influences of procedural factors on threshold values are poorly understood. The present study evaluated the influences of (i) trial sequence position and (ii) diluent type on the threshold value for the rose-like odorant phenyl ethyl alcohol. In Exp. 1, detection thresholds were measured in 24 subjects on two occasions in which different diluents were used in the concentration series, propylene glycol and light mineral oil. The thresholds were estimated using a 7-reversal initially ascending single-staircase procedure. Threshold values were significantly influenced by the type of diluent (lower for mineral oil) and trial sequence (lower for later threshold reversals). In Exp. 2, 24 subjects were administered a staircase threshold test which continued through 15 staircase reversals. Continued testing resulted in a significant lowering of the threshold measure. These findings demonstrate the importance of both diluent and test length on detection threshold values measured by a single staircase procedure and emphasize the need for standardization of procedures for threshold testing.

The role of perceptual and structural similarity in cross-adaptation.

Cross-adaptation, the decrease in sensitivity to one odorant following exposure to a different odorant, is affected by odorant similarity, both perceptual and structural, but the precise relationship is obscure. The present series of studies was designed to explore various aspects of perceptual and structural similarity as they relate to cross-adaptation. In Experiment 1, cross-adaptation was assessed between androstenone and five odorants that share a common urinous note with androstenone, but retain unique perceptual characteristics; only the compound judged most perceptually similar to androstenone cross-adapted it. In Experiment 2, odorants both perceptually and structurally similar (androstenone and androstanone) displayed significant, mutual cross-adaptation. Furthermore, magnitude estimates for androstanone were significantly reduced following exposure to 3-methylidene-5 alpha-androstane (3M5A), a structurally similar, perceptually odorless compound. This finding appears to be the first demonstration that an odorless compound can affect, via cross-adaptation, the perception of an odorous compound. Finally, in Experiment 3, significant, asymmetric cross-adaptation was observed between compounds that are perceptually and structurally dissimilar (4-cyclohexylcyclohexanone [4-CHCH] and androstenone). These findings indicate that the role of similarity in cross-adaptation is difficult to quantify and emphasize the numerous odorant characteristics that can affect cross-adaptation.

Cross-adaptation of sweaty-smelling 3-methyl-2-hexenoic acid by a structurally-similar, pleasant-smelling odorant.

Cross-adaptation has been interpreted as a measure of the degree to which odors share common sensory channels. How structural similarity, in the absence of perceptual similarity, influences cross-adaptation is unknown. The present study assessed cross-adaptation by structurally similar, but perceptually different, odorants. Magnitude estimates for a 10:1 mixture of (E)- and (Z)-3-methyl-2-hexenoic acid (3M2H), a principal component of human underarm odor, decreased following adaptation to a mixture of (E)- and (Z)-ethyl esters of 3M2H (EE3M2H), which possess a pleasant, fruity odor. Cross-adaptation was asymmetric; adaptation to 3M2H did not significantly affect the perceived intensity of EE3M2H. By contrast, there was no significant cross-adaptation between 3M2H and the fruity-smelling ethyl esters of its homologues, 3-methyl-2-octenoic acid (EE3M20) and 3-methyl-2-pentenoic acid (EE3M2P). Similarity ratings revealed no differences among the three ethyl esters in their perceptual similarity to 3M2H (i.e. all were rated equally dissimilar to 3M2H). Molecular modeling studies revealed no difference in the charge distribution of these molecules. Rather, differences in the shape and size of the hydrophobic part of the molecule may determine the extent of cross-adaptation. These results demonstrate that structurally-similar, yet perceptually-distinct, odorants may cross-adapt and suggest that the extent of cross-adaptation may be affected by the degree of structural, as well as perceptual, similarity.

Evaluating diaphragm activity in trauma patients.

The diaphragm is the major respiratory muscle responsible for most of the inspiratory work of breathing. Bedside clinicians often overlook the need to assess the diaphragm or have never focused their attention on understanding the mechanisms behind this muscle. This article updates the trauma nurse on the anatomy and physiology of the diaphragm, reviews current methods for assessing diaphragm activity, and discusses research and diagnostic methods concerning the diaphragm. With heightened awareness of diaphragmatic function, clinicians may be able to improve the respiratory status of the trauma patient by preventing diaphragm fatigue or exhaustion.

Wound care update for postanesthesia nurses.

New wound care products are increasingly found in many PACUs. Understanding the basic principles of wound healing and being familiar with the different types of dressings is essential for PACU nurses. This article reviews the phases of wound care healing, do's and don'ts of wound management, wound debridement, and the types of dressings available.

Differences in end-tidal carbon dioxide and breathing patterns in ventilator-dependent patients using pressure support ventilation.

BACKGROUND: Although several investigators have assessed the effects of pressure support ventilation on tidal volume and breathing patterns, none have investigated the combination of breathing patterns and end-tidal carbon dioxide in ventilator-dependent patients. OBJECTIVES: To determine the differences in end-tidal carbon dioxide and breathing patterns at varying pressure support ventilation levels in ventilator-dependent patients. METHODS: Breathing patterns were measured with a plethysmograph and a ventilator. End-tidal carbon dioxide was measured by connecting the capnography sampler to the exhalation port of intubated patients. All equipment was connected to a five-channel recorder for data collection. The respiratory rate, tidal volume, minute ventilation, end-tidal carbon dioxide concentration, and chest and abdominal movement were recorded at 10-minute intervals at four pressure support ventilation levels (0, 10, 15, and 20 cm H2O). RESULTS: As pressure support ventilation increased, the respiratory rate, end-tidal carbon dioxide concentration, and asynchronous movement of chest and abdomen decreased. Tidal volume increased with higher pressure support ventilation levels. CONCLUSIONS: Pressure support ventilation prevents asynchronous chest and abdominal movement and lowers the level of end-tidal carbon dioxide. Pressure support ventilation offers clinicians a way to lower the elevated carbon dioxide level that often occurs in critically ill patients. Increasing tidal volume and reducing the work of breathing by using pressure support ventilation may reduce diaphragm fatigue in ventilator-dependent patients.