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Biomedical subjects

F W Moler

Publications and source records attributed to F W Moler.

At least 37 records · Page 2Linked to original sources
PubMed1994

Extracorporeal life support for severe pediatric respiratory failure: an updated experience 1991-1993.

OBJECTIVE: The purpose of this study was to examine our recent experience with children who had acute respiratory failure managed with extracorporeal life support (ECLS) from 1991 to 1993, to determine whether a change in survival rate had occurred in comparison with our previous experience. DESIGN: Historic and prospective cohort study. SETTING: A tertiary pediatric referral center. PATIENTS: All non-neonatal pediatric patients treated with ECLS for severe, life-threatening respiratory failure were examined. Overall, 25 patients have been managed with this life-support technique in the past 28 months. Eighty-four percent (21/25) were transferred to our medical center because of failure of conventional mechanical ventilation therapy. Descriptive data of the recent cohort were as follows (mean +/- SD): age 60 +/- 75 months, weight 23.6 +/- 24.8 kg, and male gender 44%. Duration of intubation before ECLS was 5.8 +/- 2.7 days. Arterial blood gas values and ventilator settings immediately before ECLS were as follows: fraction of inspired oxygen, 0.98 +/- 0.08; mean airway pressure, 21.6 +/- 6.2 cm H2O; peak inspiratory pressure, 45.5 +/- 9.6 cm H2O; positive end-expiratory pressure, 11.0 +/- 4.3 cm H2O; partial pressure of oxygen (arterial), 56 +/- 20 mm Hg (7.4 +/- 2.7 kilopascals); partial pressure of carbon dioxide (arterial), 46 +/- 17 mm Hg (6.1 +/- 2.3 kPa); and estimated alveolar-arterial oxygen tension difference, 572 +/- 81 mm Hg (76.3 +/- 10.8 kPa). Mean duration of ECLS was 373 +/- 259 hours. Of 25 recently treated patients, 22 (88%) survived their life-threatening respiratory illness to be discharged home; this represented a statistically improved survival rate in comparison with the 58% survival rate previously reported by us for similar patients (p < 0.05). Comparisons of arterial blood gas and mechanical ventilation-related variables measured 24 hours before and again immediately before bypass were similar in the two cohorts with the exception of higher mean partial pressure of carbon dioxide (arterial) 24 hours before bypass in the recent treatment group. For our entire experience, younger age groups had greater survival rates; 100% of infants less than 1 year of age survived. CONCLUSIONS: Treatment with ECLS is an evolving pulmonary rescue therapy with an 88% survival rate in our recent experience. The survival rate has improved to levels that may not greatly improve in the near future, especially for patients less than 1 year of age. Better patient selection or improved management strategies or both may be responsible for the improved patient outcome.

Acute Disease↗
PubMed1994

Alveolar-arterial oxygen gradients before extracorporeal life support for severe pediatric respiratory failure: improved outcome for extracorporeal life support-managed patients?

OBJECTIVE: Recent reports have described the usefulness of the alveolar-arterial oxygen tension difference (P[A-a]O2) in predicting mortality in children with acute respiratory failure managed with mechanical ventilation. We reviewed our experience with extracorporeal life support for acute pediatric respiratory failure and specifically examined P(A-a)O2 measurements during the 24 hrs before extracorporeal life support to determine if defined cutoffs established with conventional mechanical ventilation were applicable to extracorporeal life-support survival. DESIGN: Retrospective, case-series chart review. SETTING: A university tertiary medical center. PATIENTS: Infants and children (n = 36), one month to 18 yrs of age, with severe life-threatening respiratory failure who were believed to have failed conventional mechanical ventilatory support. INTERVENTIONS: Veno-venous or veno-arterial extracorporeal life support. MEASUREMENTS AND MAIN RESULTS: From 1982 to 1992, we managed 36 pediatric patients with severe respiratory failure using extracorporeal life support. We identified 28 patients who had P(A-a)O2 values of > 400 torr (> 53.3 kPa) for the 24-hr time period before placement on bypass. At the time of bypass initiation, all blood gas and mechanical ventilator parameters except PaCO2 showed trends of worsening pulmonary function, compared with measurements done 24 hrs before bypass initiation. Oxygenation-related variables showed statistically significant worsening trends when measured 24 hrs before bypass, compared with the time of bypass: P(A-a)O2 539 vs. 582 torr (71.9 vs. 77.6 kPa), p < .01; PaO2/FIO2 ratio 70 vs. 57 torr (9.3 vs. 7.6 kPa), p < .05; oxygenation index 32 vs. 47 cm H2O/torr, p < .01; and FIO2 0.94 vs. 0.98, p < .05. Sixty-one percent of extracorporeal life support-managed patients (17 of 28) survived their life-threatening respiratory illness to be discharged home. CONCLUSIONS: Based on previous reports of the utility of P(A-a)O2 measurements to predict mortality, our preliminary evidence suggests that extracorporeal life support results in 62% survival for pediatric respiratory failure patients predicted to have no chance of survival using conventional mechanical ventilation. Prospective, randomized trials of children with severe acute respiratory failure managed with mechanical ventilation vs. extracorporeal life support may be indicated.

Adolescent↗
PubMed1994

Simulated pediatric cardiopulmonary resuscitation: initial events and response times of a hospital arrest team.

BACKGROUND: Cardiopulmonary resuscitation (CPR) training programs exist to enhance knowledge and skills retention. However, they do not ensure that effective CPR will be performed by trainees or resuscitation teams. One aspect of CPR effectiveness is the ability of the team to respond to an emergency call in a timely manner. METHODS: We prospectively evaluated the time required for team members to respond to an emergency call and to initiate definitive treatment in our pediatric facility. The medical staff who responded had no prior knowledge of the simulated cardiac arrest (SCA) events. All events were recorded on audio-cassette tape to determine the sequence of events and response time of arrest team members. SCA scenarios represented examples of cardiac, hematologic, renal, respiratory, and pharmacologic pathophysiology. All participants were instructed to respond as though the SCA were an actual emergency. RESULTS: From December 1991 to January 1993, 37 SCAs were evaluated. Documentation began after a concise arrest scenario had been presented to a designated nursing representative who was to be the first rescuer on the scene. The rescuer first assessed the patient's condition, activated the cardiac arrest system (median elapsed time, MET, 0.50 minutes), and then initiated single-person CPR (MET 0.58 minutes). Administration of oxygen occurred at an MET of 2.25 minutes. The first member of the arrest team to respond was the pediatric resident (MET 3.17 minutes) followed by the respiratory therapist (MET 3.20 minutes), an ICU nurse (MET 3.58 minutes), a pharmacist (MET 3.42 minutes), and anesthesiology personnel (MET 4.70 minutes). DISCUSSION: The use of SCAs (termed "Mega Code") serves as an extension of Basic Life Support and Advanced Cardiac Life Support education and provides a valuable learning experience and quality assurance tool. Limitations that might influence patient outcome during an actual in-hospital arrest have led to refinements in our cardiac arrest procedures. Of particular note was the delay in oxygen administration, which may be linked to its omission from the 1986 and 1992 American Heart Association Basic Life Support Guidelines. CONCLUSION: We believe that BLS education for hospital employees should include and emphasize oxygen delivery for resuscitation.

Cardiopulmonary Resuscitation↗
PubMed1993

Predictors of outcome of severe respiratory syncytial virus-associated respiratory failure treated with extracorporeal membrane oxygenation.

OBJECTIVE: To examine the Extracorporeal Life Support Organization registry data base for all infants and children with respiratory syncytial virus-associated respiratory failure managed with extracorporeal life support, to delineate predictors of outcome. DESIGN: Retrospective cohort study. SETTING: Extracorporeal Life Support Organization data registry. PATIENTS: All pediatric patients treated in the United States with extracorporeal life support for severe pediatric respiratory syncytial virus-associated respiratory failure reported to the registry, from 1982 through June 1992. INTERVENTIONS: Venoarterial or venovenous extracorporeal life support. MEASUREMENTS AND MAIN RESULTS: As of June 1992, fifty-three pediatric patients meeting study entry criteria were reported to the Pediatric Respiratory Failure Registry (n = 412) as having received extracorporeal membrane oxygenation (ECMO) for severe respiratory syncytial virus infection with pulmonary failure. Forty-nine percent (26/53) were successfully managed and survived to hospital discharge. The mean patient age was 5.0 +/- 8.6 months. Duration of mechanical ventilation before institution of extracorporeal life support was 8.1 +/- 6.2 days. Multivariate logistic regression analysis found four variables to be associated with patient nonsurvival at the p < 0.05 level: male gender, longer duration of mechanical ventilation before ECMO, higher peak inspiratory pressure, and lower ratio of arterial oxygen tension to fraction of inspired oxygen. Era of treatment was not associated with outcome. Receiver operator characteristic curve analysis of this multivariate model resulted in cutoff points of r = 0.5 and 0.1 that resulted in 92% sensitivity and 81% specificity (false-positive ratio 19%) and 96% sensitivity and 73% specificity (false-positive ratio 27%), respectively. CONCLUSIONS: Predictors of outcome of severe respiratory failure caused by respiratory syncytial virus infection managed with ECMO exist, and multivariate predictive models with high sensitivity and low false-positive risk are possible. Similar mathematical models may be helpful in establishing criteria for future trials of ECMO versus conventional respiratory support.

Acute Disease↗
PubMed1993

Extracorporeal life support for pediatric respiratory failure: predictors of survival from 220 patients.

OBJECTIVE: The purpose of this report was to examine the Extracorporeal Life Support Organization registry database for predictors of outcome for severe pediatric respiratory failure managed with extracorporeal life support. DESIGN: Retrospective cohort study. SETTING: Extracorporeal Life Support Organization data registry. PATIENTS: All nonneonatal pediatric patients who were treated in the United States with extracorporeal life support for severe pediatric respiratory failure reported to the Extracorporeal Life Support Organization registry as of August 1991. Patients with congenital heart disease and congenital gastrointestinal malformations were excluded from study. INTERVENTIONS: Venoarterial or venovenous extracorporeal life support for severe life-threatening pulmonary failures. MEASUREMENTS AND MAIN RESULTS: As of August 1991, 220 pediatric patients meeting study entry criteria were reported to the Registry having received extracorporeal life support for severe pulmonary failure, since 1982. Forty-six percent (102 of 220 patients) were successfully managed with this technology and survived to hospital discharge. The mean patient age was 36.8 +/- 51.6 months. Fifty-one percent of the patients were male. The mean duration of mechanical ventilation before extracorporeal life support was 6.3 +/- 5.9 days. Mean blood gas and ventilatory measurements obtained before extracorporeal life support were as follows: PaCO2 52 +/- 23 torr (6.9 +/- 3.0 kPa); PaO2 59 +/- 32 torr (7.8 +/- 4.3 kPa); estimated alveolar-arterial oxygen gradient 561 +/- 63.4 torr (74.8 +/- 8.5 kPa); peak airway pressure 49.5 +/- 13.1 cm H2O; mean airway pressure 24.3 +/- 8.2 cm H2O; positive end-expiratory pressure 11.8 +/- 6.3 cm H2O; ventilator rate 58 +/- 64.4 breaths/min; and FIO2 0.98 +/- 0.07. The mean duration of extracorporeal life support for all patients was 247 +/- 164 hrs. For the 102 survivors, the mean time for decannulation from extracorporeal life support to extubation from mechanical ventilation was 6.5 +/- 7.6 days. Stepwise multivariate logistic regression modeling found the following variables to be associated with patient survival: a) patient age, b) days of mechanical ventilation before extracorporeal life support, c) peak inspiratory pressure, d) alveolar-arterial oxygen gradient, and e) extracorporeal life support administered since December 31, 1988 (all p < .05). CONCLUSIONS: Extracorporeal life support may represent an effective rescue therapy for some selected pediatric patients with severe respiratory failure for whom conventional mechanical ventilation support has failed to improve. Predictors of survival for this life-support therapy exist that may be helpful for individual patient prognostication and future prospective study.

Adolescent↗
PubMed1992

Unsuspected congenital heart disease in neonates receiving extracorporeal life support: a review of ninety-five cases from the Extracorporeal Life Support Organization Registry.

The purpose of this study was to determine the frequency of patients with congenital heart disease who were given extracorporeal life support (ECLS) for respiratory failure. Underlying congenital heart disease "masked" by respiratory failure occurred in 2%. The most frequent pre-ECLS diagnosis that "masked" congenital heart disease was persistent fetal circulation. Of neonates with a pre-ECLS diagnosis of persistent fetal circulation, congenital heart disease was found in 56 (9%) of 623 patients.

Age Factors↗
PubMed1992

Extracorporeal life support for pediatric respiratory failure.

OBJECTIVES: The purposes of this report are to a) describe the University of Michigan experience with venoarterial or venovenous extracorporeal life support for severe pediatric pulmonary rescue therapy, and b) examine survivors and nonsurvivors for differences that might be useful for examination in future, prospective studies. DESIGN: Case series report. Phase I study of safety and effectiveness of extracorporeal life support for pediatric respiratory failure. SETTING: University of Michigan Medical Center. PATIENTS: Non-neonatal pediatric patients treated with extracorporeal life support for severe respiratory failure at the University of Michigan. INTERVENTIONS: Extracorporeal life support for pulmonary failure. MEASUREMENTS AND MAIN RESULTS: From November 1982 until May 1991, 25 pediatric patients underwent extracorporeal life support for severe pulmonary failure. Twenty patients were treated in the last 36 months. Sixty percent (15/25 patients) survived their life-threatening respiratory illness, were weaned from mechanical ventilation, and were discharged home. The mean patient age was 4.1 yrs, and mechanical ventilation duration before extracorporeal life support was 5.9 days. Mean blood gas data and mechanical ventilation pressures before extracorporeal life support were: peak inspiratory pressure of 48.6 cm H2O, mean airway pressure of 21.9 cm H2O, positive end-expiratory pressure of 9.7 cm H2O, PaCO2 of 43 torr (5.7 kPa), PaO2 of 69 torr (9.1 kPa), estimated alveolar-arterial oxygen gradient of 563 torr (75 kPa), and FIO2 of 0.98. Variables associated with survival included: age of survivors vs. nonsurvivors, 2.1 vs. 7.1 yrs (p less than .02); peak inspiratory pressure of survivors vs. nonsurvivors, 43.1 vs. 57.9 cm H2O (p less than .03); mean airway pressure of survivors vs. nonsurvivors, 18.4 vs. 27.2 cm H2O (p less than .03); and positive end-expiratory pressure of survivors vs. nonsurvivors, 8.1 vs. 12.1 cm H2O (p less than .01). There were no differences detectable in the blood gas values (PaO2, PaCO2, P[A-a]O2) in survivors and nonsurvivors before extracorporeal life support. The number of days mechanical ventilation was used before extracorporeal life support in survivors and in nonsurvivors was similar. CONCLUSION: Extracorporeal life support is an effective rescue therapy for pediatric patients with severe respiratory failure (University of Michigan survival rate of 60%).

Age Factors↗
PubMed1992

Use of extracorporeal life support in patients with congenital heart disease.

OBJECTIVES: To review a large experience with extracorporeal life support in patients with congenital heart disease. To determine the major causes of mortality and morbidity in order to improve the results of using this technology in this patient population. DESIGN: Retrospective chart review. PATIENTS: Twenty-five patients between the ages of 1 day and 8 yrs. These patients had congenital heart disease and were clinically felt to be at high risk for death caused by cardiac failure or by respiratory failure complicated by congenital heart disease. INTERVENTIONS: All patients in this report were placed on extracorporeal life support to allow recovery of myocardial or pulmonary function. MEASUREMENTS AND MAIN RESULTS: Of these 25 patients, 52% were weaned from bypass support and 40% survived to discharge. Patients who were not weaned from extracorporeal life support characteristically suffered from irreversible neurologic injury, multiple organ failure, or bleeding complications. Only one patient died of irreversible cardiac failure. CONCLUSIONS: Extracorporeal life support can be useful in supporting patients with congenital heart disease with life-threatening cardiac or pulmonary failure. Improvements in limiting neurologic and bleeding complications may lead to improvements in the use of extracorporeal life support for this indication. However, prospective, randomized studies are needed to appreciate the role of extracorporeal life support in these patients.

Child↗
PubMed1992

Respiratory syncytial virus morbidity and mortality estimates in congenital heart disease patients: a recent experience.

OBJECTIVE: To determine recent morbidity and mortality rates from respiratory syncytial virus infection in a pediatric congenital heart disease population. DESIGN: Retrospective cohort study design. SETTING: The C. S. Mott Children's Hospital, University of Michigan Medical Center. PATIENTS: A total of 740 pediatric patients hospitalized at the University of Michigan Medical Center for symptomatic respiratory syncytial virus infection, of whom, 79 patients had clinically important congenital heart disease. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: We retrospectively examined the charts of 740 patients hospitalized at our children's hospital from July 1, 1983 to June 30, 1990 with symptomatic respiratory syncytial virus infection to assess morbidity and mortality outcomes. Seventy-nine patients had congenital heart disease and 40 of these patients had pulmonary hypertension. For the entire cohort and a subset of patients with community-acquired infection, those patients with congenital heart disease had longer durations of hospitalization and greater need for, and days of, both intensive care and mechanical ventilation than patients without congenital heart disease. Mortality risk for respiratory syncytial virus community-acquired infection was not different for congenital heart disease vs. noncongenital heart disease patients (0.0% vs. 0.2%; p = 1.00). When examining only patients with congenital heart disease, those patients with pulmonary hypertension had increased hospital days and greater intensive care and mechanical ventilation durations compared with patients without this diagnosis. The overall mortality rate was low and was equally low for congenital heart disease groups with or without pulmonary hypertension (2.5 vs. 2.6). For community-acquired illness, no mortality was found in either congenital heart disease group. When the cohort of congenital heart disease patients was divided into pre- and postribavirin administration eras, no differences in mean hospital duration, ICU days, and mechanical ventilation days were noted. Of the 79 congenital heart disease patients, only two died during their hospitalization in which respiratory syncytial virus infection occurred. Both patients had nosocomial-acquired respiratory syncytial virus and both were from the postribavirin administration cohort. One of these two patients had received antiviral therapy. Neither death was secondary to respiratory syncytial virus respiratory failure (based on pathologic examination). CONCLUSIONS: We conclude that respiratory syncytial virus mortality risk in pediatric patients with congenital heart disease is less than the risk reported a decade ago. Respiratory syncytial virus infection in congenital heart disease patients with pulmonary hypertension is associated with increased morbidity but not increased mortality rates. The markedly decreased respiratory syncytial virus mortality risk in patients with congenital heart disease currently experienced is likely secondary to improvements in intensive care management and advances in the surgical correction in this population rather than antiviral therapy.

Academic Medical Centers↗
PubMed1991

Hemodynamic instability after the initiation of extracorporeal membrane oxygenation: role of ionized calcium.

OBJECTIVES: To prospectively document the occurrence of ionized hypocalcemia in infants and children treated with extracorporeal membrane oxygenation (ECMO), to determine if the type of calcium salt (calcium chloride or gluconate) used in priming the ECMO circuit affected ionized calcium, to determine if ionized calcium concentrations correlate with total calcium, protein, albumin, or total magnesium values, and to determine if the hypotension usually observed after ECMO initiation correlates with low circulating ionized calcium concentrations. DESIGN: Prospective study. SETTING: Pediatric ICU and neonatal ICU. PATIENTS: Sixteen neonatal and three pediatric patients who were started on ECMO for cardiopulmonary support. INTERVENTIONS: The ECMO circuit was primed in a standardized manner, 100 mg of calcium gluconate was added in group 1 patients and 100 mg of calcium chloride was added in group 2 patients. MEASUREMENTS: Ionized calcium was measured from the circuit before initiation of ECMO and from the patient before, and then 5, 10, 15, 30, 60, 120, and 240 mins after initiation of ECMO. Total calcium and ionized calcium concentrations were measured simultaneously every 6 hrs. Serum total protein, albumin, magnesium, and ionized calcium values were measured from blood samples collected simultaneously twice daily. RESULTS: A significant decrease in the mean serum ionized calcium value occurred 5 mins after the initiation of ECMO in both groups, p less than .001. The ionized calcium value remained significantly decreased until 30 mins after the initiation of ECMO. There were no differences between the ionized calcium concentrations obtained during priming with calcium gluconate vs. those concentrations obtained with calcium chloride priming (p = .79). Throughout the course of ECMO, the serum ionized calcium concentrations ranged from 0.60 to 1.86 mmol/L. Poor correlations existed between circulating ionized calcium values and total calcium (r2 = .30), total protein (r2 = .20), albumin (r2 = .20), and magnesium concentrations (r2 = .10). There was a good correlation between the patients' BP and ionized calcium concentrations after bypass was initiated (r2 = .87). CONCLUSION: Our data demonstrate that ionized hypocalcemia is a frequent occurrence after the initiation of ECMO. Since there is a poor correlation between ionized calcium and total calcium, ionized calcium concentrations should be measured directly in these patients.

Blood Pressure↗
PubMed1991

Extracorporeal life support for cardiac assist in pediatric patients. Review of ELSO Registry data.

The collected data on extracorporeal membrane oxygenation (ECMO), now referred to as extracorporeal life support (ECLS), for pediatric cardiac support has not been analyzed. The purpose of this study was to review the Extracorporeal Life Support (ELSO) Registry data to evaluate the results, identify possible predictors of outcome, and attempt to establish criteria. From 1981 to June of 1990, 189 patients were placed on ECLS for cardiac assist. The age range was 0-204 months (median, 7 months). Mean time on ECLS was 115 +/- 75 hours. Fourteen patients were placed on ECLS as a bridge to transplant or for management of transplant rejection. All of the remaining 175 patients were treated in the postoperative period. The causes of mortality included lack of improvement in cardiovascular function in 69 (37%) of the patients, major central nervous system damage in 28 (15%), uncontrollable hemorrhage in three (2%), sepsis in three (2%), and pulmonary interstitial disease in two (1%). The Registry data were examined for predictors of outcome. There was no significant difference between survivors and nonsurvivors when compared for duration of ECLS, mechanical complications, arterial or venous blood gases, ventilation settings, or hemodynamics. Forty-three percent of 189 pediatric patients treated with ECLS for cardiac failure survived. The highest survival, 61%, occurred in right-sided lesions and the lowest, 18%, in post-Fontan. Mediastinal bleeding, cardiac arrest, renal failure, and prolonged intubation were all associated with a poor outcome. Most deaths were attributed to irreversible cardiac or brain injury, suggesting that results could be improved by earlier identification of high-risk patients and earlier institution of ECLS.

Assisted Circulation↗
PubMed1991

High-frequency jet ventilation improves cardiac function after the Fontan procedure.

Pulmonary vascular resistance is an important determinant of cardiac output after the Fontan procedure and is adversely affected by elevated mean airway pressure. High-frequency jet ventilation (HFJV) is an alternate form of mechanical ventilation which supports gas exchange at lower mean airway pressure. This study was performed to determine if HFJV could lower mean airway pressure and pulmonary vascular resistance and result in an increase in cardiac output after the Fontan procedure. We prospectively evaluated 13 patients ranging in age from 0.9 to 8.5 years (mean, 3.9 years) and in weight from 6.2 to 20.1 kg (mean, 13.9 kg). Right atrial, left atrial and pulmonary artery catheters were used to measure hemodynamic parameters. Cardiac index was measured by dye dilution technique, and pulmonary vascular resistance was calculated. The patients were stabilized on mechanical ventilation to achieve a PaCO2 = 30 +/- 5 mm Hg, and baseline hemodynamic and respiratory measurements were made. HFJV was begun at settings adjusted to achieve similar gas exchange. Respiratory and hemodynamic measurements were repeated after 30-60 minutes of HFJV. Mechanical ventilation was then resumed at baseline settings, and measurements were repeated 0.5-1 hour later. There was no significant change in gas exchange. HFJV resulted in a 50% reduction in mean airway pressure (9.2 +/- 0.2 cm H2O to 4.6 +/- 0.1 cm H2O, p less than 0.001), a 59% reduction in pulmonary vascular resistance (3.82 +/- 0.36 to 1.52 +/- 0.16 Woods units, p less than 0.001), and a 25% increase in cardiac index (2.32 +/- 0.12 l/min/m2 to 2.91 +/- 0.12 l/min/m2, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Child, Preschool↗
PubMed1988

Improvement in clinical asthma score and PaCO2 in children with severe asthma treated with continuously nebulized terbutaline.

We analyzed continuous nebulized terbutaline (CNT) therapy in 19 patients with 27 admissions for severe asthma and impending respiratory failure who failed to respond to our standard asthma protocol of methylprednisolone, aminophylline, and intermittently nebulized terbutaline. Terbutaline was administered by continuous face mask nebulization at a dose equaling the most frequent previous intermittent dose per hour (4 mg per hour). No patient with frank respiratory failure (i.e., PaCO2 greater than or equal to 60 torr, exhaustion, or coma) was studied. All patients improved, and therapy was stopped in a mean of 15.4 hours (range 3 to 37 hours). The average heart rate did not increase over baseline measurements through 24 hours of CNT. The mean clinical asthma score improved significantly during 8 hours, falling from 6.9 to 3.2 (p greater than 0.001). In 14 patients whose PaCO2 was greater than or equal to 39 torr (range 39 to 58 torr) and clinical asthma score was 6 or greater, PaCO2 decreased a mean of 11.7 torr during a mean of 8.1 hours. In six patients whose PaCO2 was 45 torr or greater at the start of CNT (mean 49, range 45 to 58 torr) and in whom we would have previously treated with intravenous isoproterenol, PaCO2 decreased a mean of 15 torr in an average of 8.7 hours. This preliminary study suggests that CNT is an effective therapy for severe asthma in children.

Administration, Inhalation↗
PubMedDate not supplied

Influence of tidal volume, respiratory rate, and supplemental oxygen flow on delivered oxygen fraction using a mouth to mask ventilation device.

We examined the influence of the following parameters in determining the FiO2 delivered to a pediatric lung model using the mouth-to-mask method of resuscitation: rate of ventilation, inspiratory tidal volumes, and supplemental oxygen flow. With a ventilator rate of 20/min and tidal volumes (Vt) < or = 100 mL, an FiO2 of approximately .50 was observed with a supplemental oxygen flow of 5 L/min. Increasing the supplemental oxygen flow to 15 L/m did not appreciably increase the FiO2 (FiO2 = .53 versus FiO2 = .60, respectively), but did cause a significant and unintended increase in Vt. Similar results were noted with a ventilator rate of 12/min and Vt < or = 100 mL (FiO2 = .68 versus FiO2 = .73, respectively). We also observed a potentially hazardous situation involving the positioning of the supplemental oxygen port that might result in high inspiratory pressures (stacking of breaths) to the pediatric patient. We believe additional testing is warranted prior to widespread use of this device in children.

Child↗