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Determinants of Tracheal Pressure During Flow-Dependent Positive Expiratory Pressure Therapy
Irene Comelli1,2, Lorenzo Ball1,2, Chiara Robba1,2
1Drs. Comelli, Ball, Robba, Patroniti, and Battaglini are affiliated with Department of Surgical Sciences and Integrated Diagnostics (DISC), University of Genoa, Genoa, Italy.
Background:
Positive expiratory pressure (PEP) devices facilitate airway clearance, but the determinants of pressure transmission during therapy are not fully understood.
Methods:
In this bench study, a flow-dependent PEP device was tested using tracheostomy tubes with internal diameters of 7, 8, and 9 mm under different oxygen flows (0-15 L/min), tidal volumes (260-886 mL), and breathing frequencies (10-32 breaths/min). Tracheal and airway pressures were measured.
Results:
A total of 486 observations were analyzed. Mean maximum tracheal pressure was 11 ± 7 cm H2O for 7 mm and 8 mm tubes and 10 ± 6 cm H2O for 9 mm tubes. Oxygen flow was the main determinant of maximum tracheal pressure (β = 3.19, P < .001), while tidal volume (β = 2.75, P < .001) and breathing frequency (β = 4.44, P < .001) were also independently associated with higher pressures. Compared with the 7-mm cannula, maximum tracheal pressure was significantly lower only with the 9-mm cannula. Minimum tracheal pressure was independently associated with oxygen flow (β = 1.28, P < .001), tidal volume (β = -2.56, P < .001), and breathing frequency (β = -3.00, P < .001), with significant interaction effects between ventilatory variables. Maximum airway-opening pressure-maximum tracheal pressure gradient was negative in 354 of 486 observations and became progressively less negative with increasing cannula diameter. Oxygen flow was associated with a higher gradient (β = 0.16, P < .001), whereas tidal volume (β = -0.59, P < .001) and breathing frequency (β = -0.87, P < .001) were associated with a lower gradient.
Conclusions:
Tracheal pressure during a flow-dependent PEP therapy was influenced by oxygen flow, ventilatory pattern, and airway diameter. These findings highlight the dynamic behavior of a flow-dependent PEP device and the importance of patient-specific respiratory mechanics during therapy.
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