Respiratory care clinics of North America
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During conventional mechanical ventilation, fixed set pressure, flow, and tidal volume result in a mismatch between patient and ventilator inspiratory time and in a patient's inability to adapt to changing ventilatory demand. Synchrony between the patient and ventilator improves neuromuscular coupling and the ability to adapt to increased ventilatory demand or loading. The sensation of dyspnea prevents ineffective inspiratory efforts and attenuates periodic breathing during sleep.
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Partial patient-controlled mechanical support mode ventilators provide positive pressure assistance whenever a patient's inspiratory effort decreases pressure or flow in the ventilator circuit below the sensitivity set by clinicians; these modes minimize disuse atrophy of the respiratory muscles, can facilitate the weaning process, and usually require lower ventilator pressures. The capability of restoring gas exchange, unloading respiratory muscles, and relieving the patient's dyspnea with partial patient-controlled mechanical support modes depends on matching between the ventilator setting and the patient's ventilatory demand (ie, patient-ventilator interactions).
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Expiratory asynchrony is a universal phenomenon, and expiratory synchrony occurs only by chance. Expiratory asynchrony exists in all breath modes and has a significant impact on the patient's work of breathing and the weaning process. Advancements in ventilator designs and basic physiologic science could lead to the improvement of the expiratory asynchrony.
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Respir Care Clin N Am · Jun 2005
ReviewNew and future developments to improve patient-ventilator interaction.
The new and future developments to improve the patient-ventilator interaction are mainly based on the concept of the tight coupling between neural output and ventilator function. This tight coupling should be present throughout a patient's respiratory cycle, a task that is demanding from a technical point of view. ⋯ Although currently sophisticated computer algorithms have been developed, the caregiver is the one who controls the patient-ventilator system. Without indepth knowledge of this system, the algorithms may induce harm rather than benefit.
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Respir Care Clin N Am · Jun 2005
ReviewPatient-ventilator interaction during noninvasive positive pressure ventilation.
The interaction between the patient and the ventilator is complex,especially in a "semi-open" system as for noninvasive ventilation(NIV). Air leaks around the mask are likely to occur, and they affect patient-ventilator synchrony. Several variables may be responsible for the mismatch between the start of the neural output and that of ventilatory aid during NIV. ⋯ Last, NIV should be delivered with turbine- or piston-based ventilators that are able to compensate for air leaks. With respect to the problem of sedation, we point out the importance of optimizing the environmental conditions, avoiding excessive light and noise, assuring patient comfort, and providing reassurance. When sedation is needed, we suggest the use of low doses of analgesics and neuroleptic agents in selected cases.