Haemodynamic effects of pressure-controlled ventilation versus volume-controlled ventilation in patients submitted to cardiac surgery.
OBJECTIVE
To compare the haemodynamic effects of pressure-controlled ventilation (PCV) with volume-controlled ventilation (VCV) in patients after cardiac surgery.


METHODS
Prospective clinical study.


METHODS
Post-operative cardiac surgical ICU.


METHODS
Twenty sequential elective adult patients with no previous chronic lung disease and aged less than 70 years old.


METHODS
One hour after ICU admission and receiving mechanical ventilation utilising sinusoidal flow, patients were divided into two groups according to cardiac index (CI): group I: CI > 2.5 l/min/M2 and group II: CI < 2.5 l/min/M2. They were submitted randomly to 15 minutes' PC or VC mode, a 30-minute wash-out period of mechanical ventilation with a sinusoidal flow pattern, and then alternate PC or VC mode for 15 more minutes. Data were statistically compared using analysis of variance (ANOVA) with a significance level of 5%. Sedatives and muscle relaxants were given as necessary.


METHODS
Data were obtained at the end of 15 minutes under each ventilatory mode, observing a 30-minute interval between each.


METHODS
Standard cardiorespiratory parameters were measured or calculated using conventional monitoring (including cardiac output), Qs/Qt, A-aDO2 alveolar-arterial oxygen difference, peak inspiratory pressure, mean airway pressure and dynamic compliance (C).


RESULTS
No significant differences between PCV and VCV modes, or between groups, were seen in MPAP, MAP, PCWP, RAP, heart rate, O2ER, VO2I, Paw, C, A-aDO2 and Qs/Qt. However, DO2I (p = 0.0063), LVSWI, (p = 0.0001) and RVSWI (p = 0.0053) showed a statistically significant difference between groups I and II. No influence of VCV or PCV on these parameters was seen. There was a slight significant difference between groups for PVR (p = 0.0205). In contrast, CI (p = 0.0001) and SVR (p = 0.0062) showed significant differences among groups, but also a significantly favourable effect of PCV over VCV (p = 0.0239 and p = 0.0318 respectively). Finally, a significant reduction (p = 0.0001) in peak inspiratory pressure with PCV was observed.


CONCLUSIONS
PC and VC ventilatory modes had comparable effects on patients with preserved or depressed cardiac output. Patients ventilated with PCV showed significantly higher values for cardiac index, a decreased SVR, as well as significantly lower values for inspiratory pressure when compared with VCV patients.
Auler Júnior
J O
JO
Anesthesia and Critical Care Department, Instituto do Coração do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, Brazil.
Carmona
M J
MJ
Silva
M H
MH
Silva
A M
AM
do Amaral
R V
RV
D000368:Aged; D000704:Analysis of Variance; D006348:Cardiac Surgical Procedures; D005260:Female; D006439:Hemodynamics; D006801:Humans; D008168:Lung / Q000502:physiology; D008176:Lung Volume Measurements; D008297:Male; D008875:Middle Aged; D011184:Postoperative Period; D011446:Prospective Studies; D012121:Respiration, Artificial / Q000379:methods*