Hemodynamic and Oxygen Transport Characteristics of Common Ventilatory Modes: Statistical Analysis
Baseline ventilatory, hemodynamic, and oxygen transport data were obtained on ACV mode. Patients were then placed sequentially on SIMV and PSV modes for 30 min each. All measurements were repeated during the last 10 min before patients were switched to the next ventilatory mode. After the study was completed, patients were placed back on the ACV.
During the entire study at least one of the investigators was present at the bedside. In the event that any of the following conditions occurred, patients were immediately placed back on the ACV mode: (1) any evidence of respiratory distress such as air hunger, increased dyspnea, tachypnea (f>50% of baseline), paradoxical breathing, and apnea; (2) an increase in heart rate (>20% of baseline); (3) a decrease in systolic blood pressure (<90 mm Hg) or an increase (>20% of baseline or >160 mm Hg); (4) Sa02<88%; and (5) any significant new arrhythmia requiring therapeutic intervention.
For any parameter measured or calculated, the values for individual patients were averaged by experimental group, and SEM was calculated. Differences among various groups were tested by one-way analysis of variance with repeated measurements. Canadian neighborhood pharmacy comments Comparison among specific groups were done by multiple t test with significance adjusted by the Bonferroni method; p<0.05 was considered significant. Clinical characteristics of the patients, the FI02, and the level of pressure support are shown in Table 1. Four men and eight women with an average age of 64.8 years (range: 43 to 84) were studied. While on the SIMV mode, f increased and Vt decreased significantly compared with other modes, but Ve was similar among the three groups (Table 2). Both PIP and MIP were significantly higher in the ACV compared with other ventilatory modes; no differences between the SIMV and PSV modes were noted (Table 2). Hemodynamic parameters are listed in Table 3. Pulmonary artery systolic pressure was significantly lower in the ACV compared with other ventilatory modes. Cardiac index was also lower in the ACV, but its value reached only borderline statistical significance (p=0.051) when compared with the SIMV mode. Other hemodynamic values were not different among the three groups. Except for a significantly lower РаСОг in the ACV vs PSV mode and a higher pH in the ACV compared with the other two ventilatory modes, no differences in blood gas and oxygen transport parameters among the groups were noted (Table 4).
Table 2—Ventilatory Parameters
ACV | SIMV | PSV | |
f, breaths/min | 12.3 ±0.6 | 20.1 ±2.3 | 13.1 ±1.4 |
Vt, ml | 715 ±32 | 491 ±51 | 726 ±52 |
Ve, L/min | 9.02 ±0.06 | 8.86 ±0.07 | 9.17 ±0.06 |
PIP, cm H20 | 29.8 ±1.4 | 24.5 ±2.5 | 21.0±1.7 |
MIP, cm H20 | 6.4±0.5 | 3.6 ±0.6 | 4.6 ±0.4 |
Table 3—Hemodynamic Parameters
ACV | SIMV | PSV | |
BP„ mm Hg | 142 ±7 | 149 ±5 | 145±6 |
BPd, mm Hg | 70 ±4 | 73 ±3 | 71 ±3 |
HR, beats/min | 93 ±3 | 100±4 | 98±3 |
PAPS, mm Hg | 38.5± 1.9 | 42.6 ±2.3 | 42.8 ±2.7 |
PAPd, mm Hg | 20.5 ±1.8 | 20.5 ±1.9 | 19.3 ±1.6 |
PAPm, mm Hg | 28.1 ±1.7 | 30.2 ±2.2 | 29.6 ±2.1 |
PAOP, mm Hg | 16.8 ±1.5 | 17.0± 1.4 | 14.7 ±1.4 |
Cl, L/min/m2 | 3.3 ± 0.011 | 3.6 ±0.02 | 3.5 ±0.02 |
SVRI, d/s/cm/m2 | 2218 ±280 | 2158 ±278 | 2179 ±249 |
PVRI, d/s/cm/m2 | 288 ±38 | 305 ±27 | 347 ±29 |
SVI, ml/m2 | 35.4 ±1.8 | 36.0 ±2.1 | 36.3 ±2.1 |
Table 4—Blood Gas and Oxygen Transport Parameters
ACV | SIMV | PSV | |
Pa02, mm Hg | 98.0 ±6 | 101.5 ±6 | 109.6 ±9 |
Sa02, % | 97.0 ±0.05 | 97.3 ±0.03 | 97.6 ±0.03 |
PaC02, mm Hg | 35.8 ±2 | 38.2 ±2.5 | 38.4 ±2 |
pH | 7.46 ±0.001 | 7.43 ±0.001 | 7.42 ±0.001 |
Pv02, mm Hg | 34.8 ±1.3 | 37.0 ± 1.3 | 37.0 ±1.5 |
Sv02, % | 68.2 ±2.3 | 69.6 ±2 | 69.7 ±2.3 |
Ca02, vol % | 14.0 ±0.05 | 14.1 ±0.04 | 14.1 ±0.04 |
Cv02, vol % | 9.9 ±0.05 | 10.1 ±0.05 | 10.1 ±0.06 |
D02I, ml/min/m2 | 462 ±26 | 512±41 | 492 ±38 |
Vc^I, ml/min/m2 | 134 ±5 | 138±7 | 140±9 |
o2er, % | 30 ±2 | 28±2 | 29 ±2 |