High-frequency Percussive Ventilation Improves Oxygenation in Patients With ARDS: ResultsThe second way of analyzing the data was to examine the rates of change per hour of each parameter during the 48 h before and the 48 h after starting HFPV for each patient, and compare these values using the paired Student’s t test and a significance level of p < 0.05. The third way was to examine the difference of each parameter among three time points: (1) the last value immediately before institution of HFPV; (2) the first value after 2 h of HFPV; and (3) the last value during the 48-h period of HFPV. Comparisons were made between each pair of two time points using the paired Student’s t test. To accommodate multiple comparisons, the significance level was adjusted to p < 0.005. The general linear-model procedure was similarly performed to evaluate the differences over time, between patient types, between CV types, and their interactions.
Results
Comparison of mean values recorded over the 48 h of CV with mean values taken over the 48 h of HFPV (Table 1) revealed the following four differences: (1) Pa02/Fl02 was increased; (2) PIP was decreased; (3) MAP was increased; and (4) Sa02 was increased. Of these four statistically significant differences, the first three were also deemed to be clinically significant; the elevation in Sa02 was of questionable clinical significance. None of the hemodynamic parameters changed when the mode of ventilation was switched from CV to HFPV.
The rate of change per hour of each parameter is shown in Table 2. It is obvious that Pa02/Fl02 was deteriorating during CV and remained unchanged during HFPV. However, there was significant improvement between the values recorded on CV and those recorded after placement on HFPV. No other values achieved statistical significance. generic doxycycline

When the patients were divided according to the type of CV received before HFPV in two groups (patients who received volume-control ventilation and patients who received pressure-control ventilation), the following two observations were made (Table 3): (1) there was significant improvement in PaC02, Sa02, pH, PIP, and MAP among patients who were placed on HFPV after a period of volume-control ventilation; and (2) there was significant improvement in Pa02/Fl02, Sa02, and MAP among patients who were placed on HFPV after pressure-control ventilation.
Table 1—Respiratory and Hemodynamic Parameters During 48 h of CV and 48 h After Institution of HFPV in 32 Critically Ill Patients With ARDS

Parameters CV HFPV CV – HFPV p Value
Pa02/Fi02 130 ± 8 172 ± 17 + 42 ± 18 0.027
PaC02, mm Hg 42.5 ± 1.7 39.4 ± 1.5 – 3.0 ± 1.5 0.056
Sa0£, % 95.1 ± 0.4 96.5 ± 0.5 + 1.3 ± 0.4 0.002
ph 7.33 ± 0.02 7.37 ± 0.01 + 0.04 ± 0.02 0.058
PIP, cm H2O 39.5 ± 1.7 32.5 ± 1.9 – 7.0 ± 2.0 0.002
MAP, cm H2O 19.2 ± 1.2 27.5 ± 1.4 + 8.4 ± 1.5 < 0.001
Qs/Qt, % 37.7 ± 1.9 34.7 ± 2.4 – 3.0 ± 1.9 0.134
Do2I, mL/min/m2 619 ± 44 639 ± 50 + 20 ± 45 0.668
Vo2I, mL/min/m2 164 ± 9 155 ± 7 – 9 ± 5 0.113
O2ER, % 28.7 ± 1.9 26.2 ± 1.3 – 2.6 ± 1.9 0.206
MBP, mm Hg 82.4 ± 2.6 81.6 ± 2.5 – 0.8 ± 2.3 0.738

Table 2—Rates of Change Per Hour of Ventilatory and Hemodynamic Parameters During 48 h of CV and 48 h of HFPV in 32 Critically Ill Patients With ARDS

Parameters Rate of Change per Hour CV Rate of Change per Hour HFPV Difference Between Rates
Mean ± SE p Value Mean ± SE p Value Mean ± SE p Value
Pa0£/Fi02 -1.63 ± 0.57 0.008 +0.28 ± 0.57 0.623 + 1.91 ± 0.82 0.028
PaC02, mm Hg -0.06 ± 0.10 0.569 +0.09 ± 0.20 0.644 +0.03 ± 0.24 0.889
Sa0£, % -0.06 ± 0.04 0.150 +0.01 ± 0.02 0.606 +0.07 ± 0.05 0.134
ph -0.011 ± 0.13 0.935 -0.14 ± 0.22 0.543 -0.13 ± 0.27 0.644
PIP, cm H2O +0.14 ± 0.09 0.140 -0.16 ± 0.14 0.241 -0.31 ± 0.16 0.070
MAP, cm H2O +0.11 ± 0.06 0.062 -0.03 ± 0.03 0.372 -0.14 ± 0.07 0.045
Qs/Qt, % +0.03 ± 0.22 0.906 -0.15 ± 0.08 0.074 -0.18 ± 0.25 0.479
Do2I, mL/min/m2 + 1.28 ± 1.45 0.391 -2.18 ± 2.36 0.367 -3.46 ± 2.59 0.199
Vo2I, mL/min/m2 -0.01 ± 0.35 0.988 -0.29 ± 0.37 0.447 -0.28 ± 0.56 0.622
O2ER, % 0.20 ± 0.21 0.355 +0.04 ± 0.08 0.634 +0.23 ± 0.21 0.286
MBP, mm Hg -0.53 ± 0.26 0.051 +0.02 ± 0.07 0.786 +0.55 ± 0.27 0.053

Table 3—Respiratory and Hemodynamic Parameters During 48 h of CV and 48 h of HFPV in 32 Patients With ARDS, Stratified by Type of CV

Parameters Volume Control (n = 12) Pressure Control (n = 20)
CV HFPV p Value CV HFPV p Value
Pa02/Fi02 146 ± 16 42±67 0.352 123 ± 9 170 ± 22 0.051
PaC02, mm Hg 42.5 ± 2.7 37.6 ± 2.6 0.037 42.4 ± 2.2 40.5 ± 1.9 0.367
Sa0£, % 95.8 ± 0.5 97.3 ± 0.4 0.004 94.7 ± 0.5 95.9 ± 0.7 0.050
ph 7.31 ± 0.04 7.40 ± 0.02 0.014 7.34 ± 0.02 7.34 ± 0.01 0.836
PIP, cm H2O 38.3 ± 3.2 27.1 ± 2.4 0.004 40.2 ± 2.0 35.7 ± 2.6 0.098
MAP, cm H2O 15.0 ± 1.7 24.5 ± 2.0 0.001 21.7 ± 1.4 29.3 ± 1.9 0.001
Qs/Qt, % 36.1 ± 4.3 34.7 ± 4.6 0.587 38.6 ± 2.0 34.6 ± 2.9 0.175
Do2I, mL/min/m2 609 ± 82 666 ± 67 0.368 625 ± 53 623 ± 71 0.971
Vo2I, mL/min/m2 159 ± 11 157 ± 10 0.811 166 ± 12 154 ± 9 0.112
O2ER, % 30.3 ± 4.6 24.7 ± 1.9 0.272 27.8 ± 1.5 27.0 ± 1.8 0.610
MBP, mm Hg 87.2 ± 5.6 81.6 ± 4.1 0.117 79.5 ± 2.5 81.6 ± 3.3 0.491