Positive expiratory pressure breathing

Darbee JC, Kanga JF, Ohtake PJ. Physiologic evidence for high-frequency chest wall oscillation and positive expiratory pressure breathing in hospitalized subjects with cystic fibrosis. Phys Ther 2005 85(12) 1278-1289. 

The animals are intubated via cannulation of the trachea with an 18-gage metal tube and ventilated (Harvard pump ventilator) at a tidal volume of 0.4 mL, frequency 120 breaths/min and positive end-expiratory pressure 2.5-3.0 cm H20. 

Positive Airway Pressure in Spontaneous Mode Pressure Support in Spontaneous Mode Breath Delivery Control Mandatory Volume-Controlled Inspiratory Flow Delivery Pressure-Controlled Inspiratory Flow Delivery Expiratory Pressure Control in Mandatory Mode Spontaneous Breath Delivery Control... 

Positive end expiratory pressure (PEEP) A therapist-selected patient s airway pressure level that the ventilator maintains at the end of expiration in either mandatory or spontaneous breathing. 

Abbreviations VRU, ventilator rehabilitation unit PEEP, positive end-expiratory pressure Sao2, oxygen saturation SBT, spontaneous breathing trial Fio2, fraction of inspired oxygen CHE, congestive heart failure. 

The variable controlled during the expiratory phase is known as the baseline variable, most commonly, pressure, typically expressed as EPAP or PEEP. It is necessary to have a positive baseline pressure in bi-level devices to assure CO2 washout. Bi-level devices have also been shown to be effective in managing upper airway collapse, in patients with obstructive sleep apnea and overlap (14). Einally, a positive baseline pressure has been shown to decrease the work of breathing associated with intrinsic PEEP and improve... 

Improved alveolar ventilation may be partly compromised by an increase in the dynamic dead space (VDdyn), derived from the physiologic dead space (VDphys) plus the dead space of the apparatus (VDap). Whereas the physiologic dead space is influenced by the tidal volume, the dead space of the apparatus is a fixed consequence of the internal volume of the interface. Differences in flow pattern and pressure waveform associated with the machine and mode of ventilation, also affect the dead space of the apparatus. Saatci et al. (36) noted that during spontaneous breathing, a face mask increased VDdyn from 32% to 42% of tidal volume (VT) above VDp ys. Positive pressure during the expiratory phase reduced VDdyn close to VDphys, while inspiratory pressure support without positive end-expiratory pressure decreased VDdyn from 42% to 39% of VT, i.e., VDdyn remained higher than VDphys. When the exhalation port was placed close to the nasal bridge, VDdyn was lower than VDp ys as a consequence of a beneficial flow path that decreased VDdyn (from 42% to 28% of VT), in the presence of an expiratory positive pressure. 

The most common causes of failure to wean include chronic obstructive pulmonary disease (COPD) exacerbations, neuromuscular diseases, h) oxic respiratory failure, post surgical complications (2), and heart failure. Weaning from the tracheostomy must consider the balance of respiratory muscle function and work of breathing. The work of breathing is determined by ventilatory demand, compliance of the lungs and chest wall, airway resistance, and intrinsic positive end-expiratory pressure (PEEPi). Adequacy of ventilatory drive and neuromechanical output can be assessed from the respiratory rate, airway occlusion pressure at 100 milliseconds (Po.i), maximum inspiratory pressure (MIP), and maximum voluntary ventilation (MW). 

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