Search PubMed⌕ Search

Biomedical subjects

J H Arnold

Publications and source records attributed to J H Arnold.

At least 19 recordsLinked to original sources
PubMed2001

High-frequency oscillatory ventilation in pediatric patients.

HFOV is a mode of ventilation that can achieve oxygenation and ventilation while maintaining maximal lung recruitment on the deflation limb of its pressure-volume curve. The primary theoretical advantages of HFOV over CMV in the management of acute lung injury are that HFOV allows adequate alveolar ventilation with minimal peak-trough pressure changes, provides lung recruitment, and avoids end-inspiratory overdistension of the relatively compliant nondependent lung. Taken together, the results of studies in animals, preterm and term neonates, and older pediatric patients reveal that an "open-lung" strategy, with the goal of a high end-expiratory lung volume, is safe and superior to CMV in both the short-term (rapidly improved oxygenation and/or ventilation) and longer-term (lower incidence of chronic lung disease). The improved longer-term clinical outcomes on HFOV are presumably because of less ventilator-induced lung injury. As experience with HFOV in older patients grows, ventilator technology matures, and understanding of the pathophysiology of acute respiratory distress syndrome (RDS) deepens, it is likely that HFOV will find widespread use for the management of respiratory failure caused by acute lung injury in patients from preterm neonates to adults.

Animals↗
PubMed2001

Optimizing intrapulmonary perfluorocarbon distribution: fluoroscopic comparison of mode of ventilation and body position.

OBJECTIVE: Partial liquid ventilation with the perfluorochemical, perflubron, has been shown to improve lung mechanics and enhance gas exchange in the treatment of severe acute lung injury. However, the most effective strategy to provide optimal intrapulmonary distribution of perflubron has not been fully accessed. The objective of this study was to examine the effect of body position (supine vs. rotational) and mode of ventilation (conventional mechanical ventilation [CMV] vs. high-frequency oscillatory ventilation [HFOV]) on perflubron distribution and oxygenation improvement. DESIGN: Prospective, randomized, animal trial. SETTING: Research laboratory at a university medical center. SUBJECTS: Twenty healthy piglets (4.5-6.6 kg). INTERVENTIONS: Subjects underwent repetitive saline lavage to achieve a uniform degree of lung injury and then were randomized to either CMV or were converted to HFOV. Within each ventilator group, animals were randomized to supine positioning (S) or rotational positioning with alternation between supine and prone position (R) during incremental dosing of three 5-mL/kg doses of perflubron. MEASUREMENTS AND MAIN RESULTS: Arterial blood gas tensions, hemodynamic variables, and the oxygenation index were recorded after each dose of 5 mL/kg. Lateral cinefluoroscopic images after each dose were digitized for computer analysis of density. A density index was calculated for a 2-cm2 window in three dorsal and three ventral lung regions. Uniformity of distribution was calculated by comparing the mean density among the six regions. Oxygenation improvements were compared between groups. There were no significant differences in hemodynamic variables or gas exchange after lung injury in the four groups. Rotational positioning produced significantly more uniform perflubron distribution during both CMV and HFOV. This effect was independent of the mode of ventilation. The mean ventral density index was affected by rotating position and HFOV mode of ventilation after 10 mL/kg of perflubron, and rotating position was affected only after 15 mL/kg of perflubron. There was a significant reduction in the oxygenation index from baseline to end lavage in both CMV groups, as well as all of the animals that were rotated. CONCLUSION: Perflubron is more uniformly dispersed when dosed in a rotational fashion with alternation between supine and prone position during incremental dosing. This effect is independent of mode of ventilation. There was no relationship between oxygenation improvements and nondependent perflubron distribution. CMV and rotating dosing both led to a significant decrease in the oxygenation index after a 15 mL/kg dose of perflubron. This information has important impact on the future development of dosing strategies and clinical trial design.

Animals↗
PubMed2001

High-frequency oscillatory ventilation of the perfluorocarbon-filled lung: dose-response relationships in an animal model of acute lung injury.

OBJECTIVE: To examine dose-response relationships regarding the efficiency of gas exchange and hemodynamic function during high-frequency oscillation and partial liquid ventilation (HFO-PLV) of the perfluorocarbon (PFC)-treated lung in a model of acute lung injury. SETTING: An animal research laboratory in a university medical center. DESIGN: A prospective, randomized study comparing animals receiving varying doses (0, 5, 15, and 20 mL/kg) of perflubron during high-frequency oscillatory ventilation (HFOV) with mean airway pressure (Paw) optimized to achieve a minimal percutaneous oxygen saturation (Spo2). SUBJECTS: Nineteen healthy swine (mean weight 28.9 kg) with saline lavage-induced acute lung injury. METHODS: Animals were treated with repetitive saline lavage to achieve a uniform degree of acute lung injury (Spo2 < or =90% on an Fio2 of 1.0). After lung injury, subjects were converted to HFOV, and lung volume was optimized. HFO-PLV was initiated by instillation of perflubron at a rate of 0.5 mL.kg-1.min-1 to achieve total doses of 5, 15, and 20 mL/kg. After PFC dosing, the only experimental manipulation consisted of adjustment of Paw to achieve an Spo2 of 90% +/- 2% with Fio2 of 0.6. Gas exchange, hemodynamic variables, and pulmonary mechanics data were collected over a 1-hr period. Five control animals were not dosed with perflubron and remained on HFOV for the 1-hr period of data collection. MEASUREMENTS AND MAIN RESULTS: After lung volume recruitment with HFOV, the initiation of HFO-PLV was best tolerated with the two lower doses in our protocol. There were essentially no changes in Paco2 or pH between groups over the dosing interval. After dosing, analysis of variance demonstrated a PFC dose-dependent effect for oxygenation index (p =.01) only; the lowest oxygenation index was found in the 15 mL/kg group (p =.01). In the 15 mL/kg group, the Paw decreased steadily from 20.6 +/- 3.4 cm H2O at the end of dosing to 18.0 +/- 4.9 cm H2O at 60 mins. The Pao2 increased from 113 +/- 51 torr (15.06 +/- 6.79 kPa) to 134 +/- 49 torr (17.86 +/- 6.53 kPa) during this period and was associated with a decreasing oxygenation index (from 11.4 +/- 2.0 to 9.3 +/- 1.5). The cardiac index and pulmonary vascular resistance did not change significantly during the dosing period and were relatively stable after the completion of dosing. CONCLUSIONS: The combination of HFOV and perflubron administration was well tolerated hemodynamically and was not associated with deterioration of gas exchange during dosing. Our data suggest that the optimal dose of perflubron to achieve the lowest oxygenation index during HFO-PLV is between 5 and 15 mL/kg. The combination of HFOV and perflubron administration is a novel strategy in the treatment of acute lung injury that shows some promise and merits additional investigation. We hope in future studies to address the histopathologic effects of varying perflubron doses during HFOV in a long-term study of the lung-protective effects of HFO-PLV.

Animals↗
PubMed2001

Identification of optimal lung volume during high-frequency oscillatory ventilation using respiratory inductive plethysmography.

OBJECTIVES: First, to define the relationships between critical opening and closing pressures and oxygenating efficiency, and second, to address whether respiratory inductive plethysmography (RIP) could be used to monitor changes in thoracic volume that follow changes in mean airway pressure during high- frequency oscillatory ventilation (HFOV). DESIGN: Prospective, interventional animal study. SETTING: University research laboratory. SUBJECTS: Five anesthetized, paralyzed, and ventilated pigs. INTERVENTIONS: The animals were ventilated by using HFOV after lung injury. Pre- and post-HFOV pressure-volume curves were obtained by supersyringe. A pressure-volume curve was constructed during HFOV as mean airway pressure was increased from 10 to 40 cm H(2)O and then weaned back down to the minimum sustainable. Hemodynamic and oxygenation data were obtained at each data point. MEASUREMENTS AND MAIN RESULTS: RIP-derived thoracic volumes correlated with known lung volumes during supersyringe (r(2) =.78, p <.00001). During HFOV, three of five animals had an identifiable critical opening pressure of the lung, and four of five had an identifiable critical closing pressure. No consistent relationship between critical opening and critical closing pressures was observed. During the weaning phase of HFOV, a relative decrease in RIP-measured volume of >10% predicted the decrease in oxygenation associated with reaching the critical closing pressure. CONCLUSIONS: The ability of RIP to detect optimal lung volume during the weaning of mean airway pressure may allow clinicians to more directly monitor lung volume changes during HFOV and use the lowest possible airway pressures after lung recruitment.

Animals↗
PubMed2000

Aortic valve replacement: is valve size important?

OBJECTIVE: We sought to determine whether aortic prosthesis size adversely influences survival after aortic valve replacement. METHODS: A total of 892 adults receiving a mechanical (n = 346), pericardial (n = 463), or allograft (n = 83) valve for aortic stenosis were observed for up to 20 years (mean, 5.0 +/- 3.9 years) after primary isolated aortic valve replacement. We used multivariable propensity scores to adjust for valve selection factors, multivariable hazard function analyses to identify risk factors for all-cause mortality, and bootstrap resampling to quantify the reliability of the results. RESULTS: Twenty-five percent of patients had indexed internal orifice areas of less than 1.5 cm(2)/m(2) and more than 2 SDs (Z-value) below predicted normal aortic valve size. Mechanical valve orifices were smaller (1.3 +/- 0. 29 cm(2)/m(2), Z = -2.2 +/- 1.16) than pericardial (1.9 +/- 0.36 cm(2)/m(2), Z = -0.40 +/- 1.01) or allograft valves (2.1 +/- 0.50, Z = 0.24 +/- 1.17). The overall survival was 98%, 96%, 86%, 69%, and 49% at 30 days and 1, 5, 10, and 15 years postoperatively. Univariably, survival was weakly and inversely related to manufacturer valve size (P =.16) and internal orifice diameter (P =. 2) but completely unrelated to indexed valve area (P =.6) or Z-value (P =.8). These, and univariable differences among valve types (P =. 004), were accounted for by different prevalences in patient risk factors and not by valve size or type per se. Bootstrap resampling indicated that these findings had a less than 15% chance of being incorrect. CONCLUSIONS: Survival after aortic valve replacement is strongly related to patient risk factors but appears not to be adversely affected by moderate patient-prosthesis mismatch (down to about 4 SDs below normal). Aortic root enlargement to accommodate a large prosthesis may be required in few situations.

Adolescent↗
PubMed2000

Single-breath CO2 analysis as a predictor of lung volume change in a model of acute lung injury.

OBJECTIVE: To examine the utility of single-breath CO2 analysis as a measure of lung volume change in a model of acute lung injury. SETTING: Animal laboratory in a university-affiliated medical center. DESIGN: Prospective, animal cohort study comparing 21 variables derived from single-breath CO2 analysis with lung volume measurements determined by nitrogen washout. SUBJECTS: Seven lambs with saline lavage-induced acute lung injury. METHODS: Animals were treated with repetitive saline lavage to achieve a uniform degree of acute lung injury (PaO2 < 100 torr [13.32 kPa] on FiO2 of 1.0). Twenty-one derived components of the CO2 expirogram were evaluated as predictors of lung volume change. Lung volume was manipulated by 3-cm H2O incremental increases in positive end-expiratory pressure from 0 to 21 cm H2O and ranged between 90 and 765 mL. MEASUREMENTS AND MAIN RESULTS: Fifty-five measurements of lung volume were available for comparison with derived variables from the CO2 expirogram. Stepwise linear regression identified five variables that were most predictive of lung volume change: a) dynamic lung compliance; b) the slope of phase III; c) the slope of phase II divided by the mixed expired CO2 concentration; d) airway deadspace; and e) PaO2/FIO2 ratio. The multivariate equation was highly statistically significant and explained 94% of the variance (adjusted r2 = .94, p < .0001). The bias and precision of the calculated lung volume were 10.9 and 55.9, respectively. The mean percentage difference for the lung volume estimate derived from the single-breath CO2 analysis station was 3.3%. CONCLUSIONS: Our data indicate that analysis of the CO2 expirogram can yield accurate information about lung volume in animals with saline lavage-induced acute lung injury. Specifically, five variables derived from a plot of expired CO2 concentration vs. expired volume predict changes in lung volume in healthy lambs with an adjusted coefficient of determination of 0.94. We hope to further define the utility of this technique by prospective application of this methodology in the clinical setting.

Animals↗
PubMed2000

High-frequency oscillatory ventilation in pediatric respiratory failure: a multicenter experience.

OBJECTIVE: The use of high-frequency oscillatory ventilation (HFOV) has increased dramatically in the management of respiratory failure in pediatric patients. We surveyed ten pediatric centers that frequently use high-frequency oscillation to describe current clinical practice and to examine factors related to improved outcomes. DESIGN: Retrospective, observational questionnaire study. SETTING: Ten tertiary care pediatric intensive care units. PATIENTS: Two hundred ninety patients managed with HFOV between January 1997 and June 1998. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Patients were classified according to presence or absence of preexisting lung disease, symptomatic respiratory syncytial virus infection, or presence of cyanotic heart disease or residual right-to-left intracardiac shunt. In addition, patients for whom HFOV acutely failed were analyzed separately. Those patients with preexisting lung disease were significantly smaller, had a significantly higher incidence of pulmonary infection as the triggering etiology, and had a significantly greater duration of conventional ventilation before institution of HFOV compared with patients without preexisting lung disease. Stepwise logistic regression was used to predict mortality and the occurrence of chronic lung disease in survivors. In patients without preexisting lung disease, the model predicted a 70% probability of death when the oxygenation index (OI) after 24 hrs was 28 in the immunocompromised patients and 64 in the patients without immunocompromise. In the immunocompromised patients, the model predicted a 90% probability of death when the OI after 24 hrs was 58. In survivors without preexisting lung disease, the model predicted a 70% probability of developing chronic lung disease when the OI at 24 hrs was 31 in the patients with sepsis syndrome and 50 in the patients without sepsis syndrome. In the patients with sepsis syndrome, the model predicted a 90% probability of developing chronic lung disease when the OI at 24 hrs was 45. CONCLUSIONS: Given the number of centers involved and the size of the database, we feel that our results broadly reflect current practice in the use of HFOV in pediatric patients. These results may help in deciding which patients are most likely to benefit from aggressive intervention by using extracorporeal techniques and may help identify high-risk populations appropriate for prospective study of innovative modes of supporting gas exchange (e.g., partial liquid breathing or intratracheal pulmonary ventilation).

Blood Gas Analysis↗
PubMed2000

Acute respiratory failure in children.

Recent studies in the treatment of acute respiratory failure in children have been targeted at reducing ventilator-induced lung injury, providing treatment adjuncts to mechanical ventilation, and assessing innovative therapies directed at immunomodulation. Ventilator-associated lung injury has been demonstrated in animal models during the delivery of moderate-to-large tidal volumes and has also been described in adult populations. Subsequently, a significant survival benefit of a low tidal volume, high positive end expiratory pressure strategy on the ventilatory was found in adults. Investigation of the effects of inhaled nitric oxide in acute respiratory failure patients continues to show transient improvements in oxygenation, but no evidence of improved outcomes. The use of intratracheal surfactant within 24 hours of intubation in pediatric respiratory failure may be beneficial in reducing the days of mechanical ventilation. Neutrophil oxidative damage has been demonstrated, but therapies directed at decreasing neutrophil adherence have failed to demonstrate improvements. Enteral anti-inflammatory and antioxidant therapy may be promising, because these modalities have been shown to improve a number of surrogate outcomes in patients with respiratory failure. The use of corticosteroids in the late stages of lung injury has also recently been shown to have promise.

Acute Disease↗
PubMed2000

High-frequency ventilation in the pediatric intensive care unit.

OBJECTIVE: To provide a state-of-the-art review of high-frequency oscillatory ventilation in the management of pediatric patients with respiratory failure. DATA SOURCES: A thorough analysis of the preclinical and clinical literature regarding the pathophysiology of respiratory failure and the efficacy of high-frequency techniques in the neonatal and pediatric populations. DATA SYNTHESIS: After an overview of the introduction of high-frequency techniques, the following topical areas are addressed: device vs. strategy, indications for use, disease-specific strategies, additional practical considerations, and the future of high-frequency techniques. CONCLUSIONS: The ideal ventilatory approach in patients with hypoxemic respiratory failure may be early institution of an "open lung" strategy using high-frequency ventilatory techniques. The mechanisms of gas exchange that are most important during high-frequency ventilation are bulk axial flow, interregional gas mixing, and molecular diffusion. Infants with hyaline membrane disease and congenital diaphragmatic hernia have also responded positively to the implementation of high-frequency techniques. The oxygenation index (mean airway pressure x Fio2 x 100/Pao2) provides useful prognostic information in patients being managed with high-frequency oscillatory ventilation and may help to identify those patients with high predicted mortality to offer additional or experimental therapies. In the future, the combination of high-frequency oscillatory ventilation and partial liquid breathing offers the possibility of partitioning the physiologic changes associated with positive pressure ventilation. This approach may prove to be the ultimate lung-protective ventilatory strategy.

Journal Article↗
PubMed2000

The effects of early and repeated prone positioning in pediatric patients with acute lung injury.

STUDY OBJECTIVE: To describe the physiologic changes and to evaluate the safety of placing pediatric patients with acute lung injury (ALI) prone for 20 h/d during the acute phase of their illness. DESIGN: Single-center prospective case series. SETTING: Tertiary-level pediatric ICU. PATIENTS: Consecutive patients with bilateral pulmonary parenchymal disease requiring intubation and mechanical ventilation with a PaO(2)/fraction of inspired oxygen (FIO(2)) ratio </= 300 mm Hg. INTERVENTIONS: Patients were enrolled as soon as possible after meeting criteria and were placed in a prone position for 20 h/d daily until clinical improvement or death occurred. MEASUREMENTS AND RESULTS: Twenty-five pediatric patients who had ALI/ARDS, ranging in age from 2 months to 17 years, were placed in a prone position within 19 h of meeting the study criteria for a median time of 4 days, which accounted for 47% of their time receiving mechanical ventilation. Eighty-four percent of patients (n = 21) were categorized as overall responders to prone positioning because they experienced more days of increases of >/= 20 mm Hg in PaO(2)/FIO(2) ratio or a decrease of >/= 10% in oxygenation index when shifted from a supine to a prone position during the study period. During the 107 patient-days and 214 positioning cycles, no critical incidents occurred. Furthermore, no patient experienced a persistent decrease in oxygen saturation as measured by pulse oximetry (SpO(2)) of > 10% from values obtained when in the supine position, failed to keep their SpO(2) at > 85%, or experienced an increased respiratory rate of > 40 breaths/min when prone. Using the COMFORT score, patients were objectively rated to be equally comfortable in both the supine and prone positions. Patients also were able to resume spontaneous ventilation and to progress toward endotracheal extubation while in the prone position. Iatrogenic injury associated with prolonged prone positioning included stage II pressure ulcers in six patients (24%). CONCLUSIONS: The pediatric patients in this series demonstrated improvements in oxygenation without serious iatrogenic injury after prone positioning. This study provides a foundation for a prospective randomized study investigating the effect of early and repeated prone positioning on clinical outcomes in pediatric patients with ALI.

Adolescent↗
PubMed1999

Two internal thoracic artery grafts are better than one.

OBJECTIVE: Does the use of bilateral internal thoracic artery (ITA) grafts provide incremental benefit relative to the use of a single ITA graft? METHODS: We conducted a retrospective, nonrandomized, long-term (mean follow-up interval of 10 postoperative years) study of patients undergoing elective primary isolated coronary bypass surgery who received either single (8123 patients) or bilateral ITA grafts (2001 patients), with or without additional vein grafts. Multiple statistical methods including propensity score matching, and multivariable parsimonious and nonparsimonious risk factor analyses were used to address the issues of patient selection and heterogeneity. RESULTS: In-hospital mortality was 0.7% for both the bilateral and single ITA groups. Survival for the bilateral ITA group was 94%, 84%, and 67%, and for the single ITA group 92%, 79%, and 64% at 5, 10, and 15 postoperative years, respectively (P <.001). Death, reoperation, and percutaneous transluminal coronary angioplasty were more frequent for patients undergoing single rather than bilateral ITA grafting, and this observation remained true despite multiple adjustments for patient selection, sampling, and length of follow-up. The differences between the bilateral and single ITA groups were greatest in regard to reoperation. The extent of benefit of bilateral ITA grafting varied according to patient-related variables, but no patient subsets were identified for whom single ITA grafting could be predicted to provide an advantage. CONCLUSIONS: Patients who received 2 ITA grafts had decreased risks of death, reoperation, and angioplasty.

Aged↗
PubMed1999

High-frequency oscillatory ventilation of the perfluorocarbon-filled lung: preliminary results in an animal model of acute lung injury.

OBJECTIVE: To examine the efficiency of gas exchange, hemodynamic function, and histopathologic evidence of lung protection using high-frequency oscillation of the perfluorocarbon-filled lung in a model of acute lung injury. SETTING: An animal research laboratory. DESIGN: A prospective, randomized animal study comparing animals randomized to high-frequency oscillation or high-frequency oscillation and perfluorocarbon administration (perfluoro-octyl bromide, perfubron, or LiquiVent). SUBJECTS: Ten healthy swine (mean weight, 24.6 kg) with saline lavage-induced acute lung injury. INTERVENTIONS: Animals were treated with repetitive saline lavage to achieve a uniform degree of acute lung injury (Pao2 of <90 torr [11.9 kPa] on a Fio2 of 1.0). After lung injury, subjects were changed to high-frequency oscillatory ventilation and stabilized for 1 hr. High-frequency oscillation of the perfiuorocarbon-filled lung was initiated in five animals with the instillation of 30 mUkg perflubron and five animals continued receiving high-frequency oscillation for a total duration of 2 hrs after the dosing period. Histopathologic evidence of lung injury was quantified by a pathologist using an eight-variable lung injury scoring system to generate a lung injury score. MEASUREMENTS AND MAIN RESULTS: Administration of perflubron did not produce acute alterations of gas exchange. After the dosing period, there were no differences in gas exchange, hemodynamic function, or pulmonary vascular resistance between the two groups. The perfluorocarbon-treated animals had a significantly lower histopathologic total lung injury score, primarily manifested by significantly less atelectasis. CONCLUSIONS: The combination of high-frequency oscillatory ventilation and partial liquid ventilation with perfiubron was well tolerated hemodynamically, was not associated with deterioration of gas exchange during dosing, and did not produce significant differences in either gas exchange or hemodynamic variables over a 2-hr period. There was histopathologic evidence that the combination of high-frequency oscillation and perfiubron administration produces improved recruitment in both dependent and nondependent lung regions.

Animals↗
PubMed1998

Aortic valve replacement for octogenarians: are small valves bad?

BACKGROUND: As the population ages, more octogenarians become candidates for aortic valve replacement. Many octogenarians, particularly women, have a small aortic annulus and there is uncertainty as to the optimal management of this situation in that age group. METHOD: To examine this issue, we reviewed 248 octogenarians (mean age, 82.6 +/- 2.3 years; 58% men) who underwent primary isolated aortic valve replacement (n = 99), or aortic valve replacement and coronary revascularization (n = 149), between 1980 and 1995. Nineteen-millimeter valves were used in 26% of the patients. RESULTS: In-hospital mortality was 8.9%, 5% for aortic valve replacement alone and 11.4% for aortic valve replacement and coronary revascularization. It was 12.5% for the 19-mm size valves compared with 7.7% for the bigger size valves (p = 0.24). Follow-up (mean interval, 4.4 years) demonstrated survival for all patients of 85%, 60%, and 30% and survival free from cardiovascular events of 80%, 45%, and 21% at 1, 5, and 10 postoperative years, respectively. Multivariate analysis identified triple-vessel disease and preoperative congestive heart failure as associated with increased risk for both in-hospital and late mortality (p < 0.05). Valve size did not influence late survival or event-free survival regardless of body surface area. CONCLUSIONS: The use of small aortic valve prostheses in octogenarians does not adversely affect the incidence of early or late mortality or cardiac events.

Aged↗