Central venous and bladder pressure reflect transdiaphragmatic pressure during pressure support ventilation.
OBJECTIVE
To determine whether the change in bladder pressure (Pblad) and central venous pressure (Pcvp) may reflect the changes in esophageal pressure (Pes) and gastric pressure (Pgas) when inspiratory pressure support (IPS) is altered.


METHODS
Prospective clinical study.


METHODS
The ICUs of a teaching hospital.


METHODS
Ten patients currently receiving IPS ventilation via a tracheostomy or an endotracheal tube who already had bladder and central venous catheters in situ.


RESULTS
Airway pressure, Pes, Pgas, Pcvp, Pblad, and flow were measured at the original IPS setting. IPS then was reduced by 5-cm H(2)O increments until IPS was zero or was at the minimum pressure that could be tolerated by each patient. At each level of IPS, pressures and flow were measured at steady-state breathing. The maximum pressure difference for each pressure during inspiration was calculated. We found that the Delta Pblad correlated closely with the Delta Pgas (r = 0.904) and that the Delta Pes correlated with the Delta Pcvp (r = 0.951). When the Delta Pcvp - Delta Pblad was compared with the transdiaphragmatic pressure for each patient as the IPS was altered, the correlation coefficients varied from 0.952 to 0.999.


CONCLUSIONS
Although absolute values for the Delta Pcvp during mechanical ventilation do not always reflect the Delta Pes, useful information can be obtained from this route. In individual patients, the two sites of measurement followed each other when IPS was changed, enabling a bedside assessment of the response to reducing respiratory support.
Chieveley-Williams
Sarah
S
Department of Anesthesia, University College London Medical School, London, UK.
Dinner
Lila
L
Puddicombe
Anna
A
Field
Debbie
D
Lovell
A T
AT
Goldstone
John C
JC
D000328:Adult; D000368:Aged; D002496:Central Venous Pressure; D003964:Diaphragm / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011312:Pressure; D012121:Respiration, Artificial; D001743:Urinary Bladder / Q000502:physiology*