Correlation analysis of central venous pressure and intrathoracic pressures in acute respiratory distress syndrome mechanical ventilated patients, a pilot study

Background
Positive end-expiratory pressure (PEEP) can affect the measurement of central venous pressure (CVP) through increased intrathoracic pressure. However, when PEEP is applied, CVP and pleural pressure often increase more than right atrial pressure, so transmural right atrial pressure (true filling pressure) decreases.


Aim

Primary end-point was to recognize the correlation between mean CVP and thoracic pressures on controlled mode and spontaneous modes in the same population of mechanically ventilated acute respiratory distress syndrome (ARDS) patients. The secondary end-point is to compare the correlation calculated
R
during both modes with parameters of ventilatory settings.



Patients and methods

A cohort observational prospective study were done enrolling twenty single groups of patients with ARDS caused by different etiologies, who necessitate mechanical ventilation more than 2 days after connection to ventilators. The patient population was seven (35%) females patients and 13 (65%) males with mean age of 57.20 ± 11.92 years. Insertion of central venous catheter, in accordance with standard guidelines, for measuring CVP and the data collected included mean CVP, applied PEEP according to patient’s needs, plateau pressure, PEEP intrinsic, mean airway pressure, PO
2
/FiO
2
, rapid shallow breathing index, and
R
correlation
. Measurements were divided into
R
measured
and
R
calculated
according to noncalculated CVP and calculated CVP, which releases the influence of PEEP intrinsic.



Results

Twenty patients with a mean age of 57.20 ± 11.92 years (40–80) were evaluated (65% male). There were statistically significant differences between the control and support groups regarding applied PEEP, plateau pressure, mean CVP, and mean airway pressure. The data were significantly higher in the control than the support group with
P
value less than 0.001, 0.002, and 0.004, respectively but no significant difference between
R
calculated
in both groups. A significant positive correlation between
R
calculated
and CVP in the control group with
P
value less than 0.001 and
r
0.918; and significant positive correlation between
R
calculated
and ∆PiT in the pressure support group with
P
value of 0.001 and
r
=0.926. A regression equation for CVP and
R
calculated
among the control group was:
R
=0.028 + 0.032 × CVP (with
P
value <0.001), whereas a regression equation for ∆PiT and
R
calculated
among the support group was
R
=0.465 + 0.020×∆PIT (with
P
=0.022). There was a significant increase in
R
measured
than
R
calculated
in pressure control and pressure support with
P
value of 0.015 and 0.001, respectively.



Conclusion

The relation between hemodynamics change of CVPs and other thoracic pressures is a new independent marker for evaluating ARDS mechanically ventilated patients. Values of
R
correlation were not statistically different in controlled mode relative to spontaneous mode during ARDS ventilated patients.
R
correlation was related to mean CVP in controlled mode but positively correlated with intrapleural pressure (∆PiT) in spontaneous mode.