The European respiratory journal : official journal of the European Society for Clinical Respiratory Physiology
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Randomized Controlled Trial Clinical Trial
Influence of moderate alcohol consumption on obstructive sleep apnoea with and without AutoSet nasal CPAP therapy.
Snoring worsens with high alcohol consumption. It is unclear whether moderate alcohol intake worsens sleep and breathing in subjects with obstructive sleep apnoea syndrome (OSAS), and whether alcohol increases the pressure requirement for nasal continuous positive airway pressure (CPAP). Fourteen adult males with untreated OSAS but without heart or lung disease were studied (age 53+/-9 yrs, body mass index (BMI) 33+/-5 kg x m(-2) (mean+/-SD). ⋯ There was no change in the pressure requirement for CPAP (full night: control 11.9+/-0.9 vs alcohol 12.5+/-0.9 cm H2O; first 2 h: 10.9+/-0.6 vs 11.1+/-0.8 cm H2O). Moderate alcohol intake (in the form of vodka) has little effect on breathing or saturation during sleep in subjects with mild-to-severe obstructive sleep apnoea, and no effect on the pressure required for continuous positive airway pressure in order to prevent apnoea, snoring, and flow limitation. These results cannot be extrapolated to other doses or forms of alcohol, or to subjects with concurrent heart or lung disease.
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Four brands of ventilator used for noninvasive positive pressure ventilation in the home were assessed to determine their performance on a patient simulator. We tested the tidal volume (VT) preset Companion 2801 (Puritan Bennett), minute volume preset Monnal D (Taema), and two pressure preset ventilators, the Nippy (Friday Medical) and the Bilevel Positive Airway Pressure (BiPAP) (Respironics). A patient simulator was employed to investigate the relationships between VT, peak airway pressure (PAP) and mean airway pressure (MAP), the responses to an additional leak in the circuit and patient effort of a variable duration, which was modelled using a negative pressure pump. ⋯ When patient effort was prolonged to 1.5 s, a similar length to the inspiratory time of the ventilators, there was no further change in the minute volume of the Companion 2801 and Monnal D, while that of the Nippy and of the BiPAP increased by 38 and 71%, respectively, compared to baseline. These results show that distinct brands of ventilator respond to changes in the patient and patient circuit in different ways, which are not always predictable from a simple description of their operating principles. This should be borne in mind when choosing a positive pressure ventilator for noninvasive ventilation.
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Case Reports
Fatal ball-valve airway obstruction by an extensive blood clot during mechanical ventilation.
A ball-valve airway obstruction by a blood clot cast of almost the whole bronchial tree occurred in a small-cell lung cancer patient, who had been on mechanical ventilation for 9 days. Chest radiographs revealed overinflated lungs. ⋯ A postmortem extraction of the clot was performed with a rigid tube. This case is rare because of absence of severe haemoptysis and lung volume reduction.
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Review Comparative Study
Control of breathing in mechanically ventilated patients.
During mechanical ventilation, the respiratory system is under the influence of two pumps, the ventilator pump and the patient's own respiratory muscles. Depending on the mode of mechanical ventilatory support, ventilation may be totally controlled by the ventilator or may be determined by the interaction between patient respiratory effort and ventilator function. In either case, compared to spontaneous breathing, the breathing pattern is altered and this may influence: 1) force-length and force-velocity relationships of respiratory muscles (mechanical feedback); 2) chemical stimuli (chemical feedback); 3) the activity of various receptors located in the respiratory tract, lung and chest wall (reflex feedback); and 4) behavioural response (behavioural feedback). ⋯ Thus, the response of ventilator to patient effort, and that of patient effort to ventilator-delivered breath are inevitably the two components of control of breathing during mechanical ventilation; the ventilatory output is the final expression of the interaction between these two components. As a result of this interaction, the various aspects of control of breathing of the respiratory system may be masked or modulated by mechanical ventilation, depending on several factors related both to patient and ventilator. This should be taken into consideration in the management of mechanically ventilated patients.
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Comparative Study
A five year follow-up of lung function among chemical workers using flow-volume and impedance measurements.
Impedance of the respiratory system, measured using the forced oscillation technique (FOT), has repeatedly been proposed as a tool for occupational health screening. The aim of this study was to compare the outcome of impedance measurements and flow-volume curves, and to study relationships between lung function decline and specific exposures and smoking. Both measurements were applied in 136 chemical workers from seven main production/personnel groups during a 5 year follow-up (1990-1995). ⋯ Smoking had a significant effect on most flow-volume parameters but only for frequency dependence among the impedance outcomes. It is concluded that alterations in impedance parameters do reflect changes in flow-volume curves induced by age. smoking and occupational exposure. Therefore, these data are a valuable extension to current cross-sectional data.