The European respiratory journal : official journal of the European Society for Clinical Respiratory Physiology
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Expiratory flow limitation (EFL) during tidal breathing is a major determinant of dynamic hyperinflation and exercise limitation in chronic obstructive pulmonary disease (COPD). Current methods of detecting this are either invasive or unsuited to following changes breath-by-breath. It was hypothesised that tidal flow limitation would substantially reduce the total respiratory system reactance (Xrs) during expiration, and that this reduction could be used to reliably detect if EFL was present. ⋯ Among other indices, mean inspiratory minus mean expiratory Xrs (deltaXrs) and minimum expiratory Xrs (Xexp,min) identified flow-limited breaths with 100% specificity and sensitivity using a threshold between 2.53-3.12 cmH2O x s x L(-1) (deltaXrs) and -7.38- -6.76 cmH2O x s x L(-1) (Xexp,min) representing 6.0% and 3.9% of the total range of values respectively. No flow-limited breaths were seen in the normal subjects by either method. Within-breath respiratory system reactance provides an accurate, reliable and noninvasive technique to detect expiratory flow limitation in patients with chronic obstructive pulmonary disease.
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Review Comparative Study
Immunosuppressive therapy after human lung transplantation.
In 2002, equal numbers of lung transplantation (LTx) were performed with or without induction therapy with antilymphocyte antibodies, monoclonal anti-CD3 antibody or anti-interleukin-2-receptor monoclonal antibodies. It remains to be established if induction therapy after LTx is beneficial or deleterious for long-term graft and patient survival. The vast majority of lung transplant recipients receive a triple-drug maintenance regimen including a calcineurin inhibitor, a cell-cycle inhibitor and steroids. ⋯ The superiority of Tac over CsA as a maintenance agent has not been established to date, and the administration of MMF instead of Aza in combination with CsA and steroids did not improve graft or patient survival in a recent international, prospective, randomised, controlled trial. Shift from cyclosporin A to tacrolimus has emerged as the first treatment step of refractory acute rejection followed by high-dose steroids or antilymphocyte agents, total lymphoid irradiation or photopheresis. The treatment of chronic rejection remains deceptive and includes varied strategies such as modification of the maintenance regimen, addition of inhaled immunosuppressants and/or total lymphoid irradiation and photopheresis.
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The aim of this study was to determine what the influence of different designs of face masks and different noninvasive ventilator modes would be upon total dynamic dead space. Using a spontaneous breathing model, total dynamic dead space was measured when using 19 commercially available face masks and a range of ventilators in various ventilation modes. Total dynamic dead space during spontaneous ventilation was increased above physiological dead space from 32% to 42% of tidal volume by using face masks. ⋯ Pressure assist and pressure support ventilation decreased total dynamic dead space to a lesser degree, from 42% to 39% of tidal volume. Face masks with expiratory ports over the nasal bridge resulted in beneficial flow characteristics within the face mask and nasal cavity, so as to decrease total dynamic dead space to less than physiological dead space from 42% to 28.5% of tidal volume. Exhaust ports over the nasal bridge in face masks effect important decreases in dynamic dead space provided positive pressure throughout the expiratory phase is used.
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Editorial Comment
The interface: crucial for successful noninvasive ventilation.
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The forced oscillation technique (FOT) is a noninvasive method with which to measure respiratory mechanics. FOT employs small-amplitude pressure oscillations superimposed on the normal breathing and therefore has the advantage over conventional lung function techniques that it does not require the performance of respiratory manoeuvres. The present European Respiratory Society Task Force Report describes the basic principle of the technique and gives guidelines for the application and interpretation of FOT as a routine lung function test in the clinical setting, for both adult and paediatric populations. ⋯ Forced oscillation technique has been shown to be as sensitive as spirometry in detecting impairments of lung function due to smoking or exposure to occupational hazards. Together with the minimal requirement for the subject's cooperation, this makes forced oscillation technique an ideal lung function test for epidemiological and field studies. Novel applications of forced oscillation technique in the clinical setting include the monitoring of respiratory mechanics during mechanical ventilation and sleep.