Mechanical ventilation for children with status asthmaticus.

Status asthmaticus is the most common diagnosis leading to hospital admission in childhood. Most of these patients respond well to oxygen, steroids, beta-agonists, anticholinergics, and other medications. The few patients who develop respiratory failure from severe status asthmaticus pose many challenges to those supporting them in the intensive care unit. This Article discusses the pathophysiology of asthma and how that relates to appropriate ventilator management. Alternative therapies are briefly discussed.

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).

Prospective, randomized comparison of high-frequency oscillatory ventilation and conventional mechanical ventilation in pediatric respiratory failure.

OBJECTIVE: To compare the effectiveness of high-frequency oscillatory ventilation with conventional mechanical ventilation in pediatric patients with respiratory failure. SETTING: Five tertiary care pediatric intensive care units. DESIGN: A prospective, randomized, clinical study with crossover. PATIENTS: Seventy patients with either diffuse alveolar disease and/or airleak syndrome were randomized to receive high-frequency oscillatory ventilation or conventional mechanical ventilation. INTERVENTIONS: Patients randomized to receive high-frequency oscillatory ventilation were managed, using a strategy that consisted of aggressive increases in mean airway pressure to attain the "ideal" lung volume and to achieve an arterial oxygen saturation of > or = 90%, with an FIO2 of < or = 0.6. Patients who were randomized to receive conventional mechanical ventilation were treated with a strategy that utilized increases in end-expiratory pressure and inspiratory time to increase mean airway pressure and to limit increases in peak inspiratory pressure. Target blood gas values were the same for both groups. Crossover to the alternate ventilator was required if the patient met defined criteria for treatment failure. MEASUREMENTS AND MAIN RESULTS: Physiologic data and ventilatory parameters were collected prospectively at predetermined intervals after randomization. Airleak Scores were derived daily, based on the chest radiograph and the patient's clinical condition. In the high-frequency oscillatory ventilation group, the PaO2/PAO2 ratio increased significantly and the oxygenation index (mean airway pressure x FIO2 x 100/PaO2) decreased significantly over time. There were no differences between the groups in duration of mechanical ventilation, frequency of airleak, Airleak Scores, or 30-day survival rates. Significantly fewer patients treated with high-frequency oscillatory ventilation required supplemental oxygenation at 30 days compared with patients managed with conventional ventilation. When ventilatory subgroups were compared, the patients managed with high-frequency oscillation only had significantly better ranked outcomes than patients managed with conventional ventilation only. CONCLUSIONS: Our results indicate that high-frequency oscillatory ventilation, utilizing an aggressive volume recruitment strategy, results in significant improvement in oxygenation compared with a conventional ventilatory strategy designed to limit increases in peak airway pressures. Furthermore, despite the use of higher mean airway pressures, the optimal lung volume strategy used in this study was associated with a lower frequency of barotrauma, as indicated by requirement for supplemental oxygen at 30 days, and improved outcome compared with conventional mechanical ventilation.

Analysis of the chromosomal location of two copies of a Bordetella pertussis insertion sequence.

IS481v1 and IS481v2 are two copies of a Bordetella pertussis insertion sequence element. We have shown that IS481v1 is located within 3 kbp of the start of the adenylate cyclase gene whilst IS481v2 is immediately adjacent to the end of the agglutinogen 2 gene and provides the stop codon for that gene. In addition, IS481v1 and IS481v2 were present at these two specific sites in nine strains of B. pertussis, including two Phase IV strains which expressed neither adenylate cyclase nor agglutinogen 2 and three Phase I strains which did not express agglutinogen 2. The loss of expression in these strains is not the result of DNA rearrangements at the sites of IS481v1 or IS481v2.

Analysis of separate isolates of Bordetella pertussis repeated DNA sequences.

Two independent isolates of a Bordetella pertussis repeated DNA unit were sequenced and shown to be an insertion sequence element with five nucleotide differences between the two copies. The sequences were 1053 bp in length with near-perfect terminal inverted repeats of 28 bp, had three open reading frames, and were each flanked by short direct repeats. The two insertion sequences showed considerable homology to two other B. pertussis repeated DNA sequences reported recently: IS481 and a 530 bp repeated DNA unit. The B. pertussis insertion sequence would appear to comprise a group of closely related sequences differing mainly in flanking direct repeats and the terminal inverted repeats. The two isolates reported here, which were from the adenylate cyclase and agglutinogen 2 regions of the genome, were numbered IS48lvl and IS48lv2 respectively.

Malignant mesothelioma of tunica vaginalis testis.

A case of biphasic malignant mesothelioma of the tunica vaginalis occurring in a sixty-four-year-old man is described. The tumor metastasized widely and led to the patient's death two and one-half years after diagnosis. Review of the literature revealed 7 cases of malignant mesothelioma of tunica vaginalis. These tumors appeared highly aggressive with early onset of metastasis. Histologically, the tumors may be epithelial, fibrous, or biphasic. In contrast to the benign variants of mesotheliomas, these tumors often show significant nuclear atypia, mitotic activity, and invasion of the epididymis, spermatic cord, lymphatic spaces, or the fibrous tissue of the tunica.