The European respiratory journal : official journal of the European Society for Clinical Respiratory Physiology
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Historical Article
A thousand years of pulmonary medicine: good news and bad.
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Mechanical ventilation of the lung is an essential but potentially harmful therapeutic intervention for patients with acute respiratory distress syndrome. The objective of the current study was to establish and characterize an isolated mouse lung model to study the harmful effects of mechanical ventilation. Lungs were isolated from BalbC mice and randomized to either a nonventilated group, a conventionally ventilated group (tidal volume 7 mL x kg(-1), 4 cm positive endexpiratory pressure (PEEP)) or an injuriously ventilated group (20 mL x kg(-1), 0 cm PEEP). ⋯ Injurious ventilation also led to a significantly increased concentration of interleukin-6 and tumour necrosis factor-a in the lavage. It was concluded that the injurious effects of mechanical ventilation can effectively be studied in isolated mouse lung, which offers the potential of studying genetically altered animals. It was also concluded that in this model, the lung injury is, in part, mediated by the surfactant system and the release of inflammatory mediators.
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Comparative Study
Functional differences in bi-level pressure preset ventilators.
The performance of four bilevel positive pressure preset ventilators was compared. The ventilators tested were; BiPAP ST30 (Respironics); Nippy2 (B + D Electrical); Quantum PSV (Healthdyne); and Sullivan VPAP H ST (Resmed). A patient simulator was used to determine the sensitivity of the triggering mechanisms and the responses to a leak within the patient circuit, and to changes in patient effort. ⋯ An increase in VT was seen with some ventilators with patient efforts of 1 s but the effect was variable. Trigger failures and subsequent falls in minute volume were seen with the BiPAP and the Nippy2 at the highest respiratory frequency. Differences in the responses of the ventilators are demonstrated that may influence the selection of a ventilator, particularly in the treatment of breathless patients with ventilatory failure.
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Leak compensating abilities of six different positive pressure ventilators commonly used to deliver noninvasive positive pressure ventilation, including the bilevel positive airway pressure (BiPAP) S/T-D and Quantum (Respironics Inc, Murrysville, PA, USA), 335 and O'NYX (Mallinckrodt Inc, St Louis, MO, USA), PLV 102 (Respironics), and Siemens Servo 900C (Siemens Inc, Danvers, MA, USA). Using a test lung model, compensatory capabilities of the ventilators were tested for smaller and larger leaks using the assist/control or timed modes. Back-up rate was 20 min(-1), inspiratory pressure was 18 cmH2O, and expiratory pressure was 5 cmH2O. ⋯ Volume-targeted modes achieved limited compensation for small air leaks, but compensated poorly for large leaks. To conclude, leak-compensating capabilities differ markedly between ventilators but pressure-targeted ventilators are preferred for noninvasive positive pressure ventilation in patients with substantial air leaking. Adequate inspiratory flows and durations should be used, triggering sensitivity should be adjusted to prevent autocycling, and a mechanism should be available to limit inspiratory time and avoid I:E ratio inversion.
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The Paediatric Asthma Caregiver's Quality of Life Questionnaire (PACQLQ), measures the impact of child asthma symptoms on family activity (CGAct) and parental anxiety (CGEmot). It has not been validated for families of children <7 yrs, with wheezing illness. This study assessed the sensitivity of the PACQLQ to symptom change in 62 preschool children with wheezing illness. ⋯ Compared to parents with higher PACQLQ change, parents with PACQLQ scores <0.5, did not differ in frequency of child symptoms or in social-demographic factors, but had better quality of life scores on entry to the study (p<0.01). It is concluded that the Paediatric Asthma Caregiver's Quality of Life Questionnaire is sensitive to group measures of child symptom change over 3 months, among preschool children, and this supports its use as an outcome measure in clinical trials. The absolute impact of child symptoms on parent quality of life varies among parents.