A Functional and Morphologic Analysis of Pressure-Controlled Inverse Ratio Ventilation in Oleic Acid-Induced Lung Injury: Results

Lung injury was characterized by a decrease in static compliance by 12 ml/cm H2O (p<0.05) and by an increase in mean pulmonary artery pressure from 13 to 32 mm Hg (p<0.05). Venous admixture increased from 7 to 45 percent (p<0.05) and PaC>2 fell markedly from 38.7 kPa (290 mm Hg) to 9.3 kPa (70 mm Hg) (p<0.01). Physiologic dead-space increased from 19 percent to 27 percent (p<0.05) and FRC fell from 421 to 207 ml (p<0.05). Table 1 gives a summary of the results.
Lung Function and Hemodynamics (Table 1)—Effects of PEEP
Application of PEEP resulted in improved respiratory mechanics with an increase in static compliance from 20 to 27 ml/cm H2O (p<0.01). The FRC was doubled compared with ZEEP ventilation (404 vs 207 ml, p<0.001). Mean and peak airway pressures increased from 10 to 17 (p<0.001) and from 39 to 44 cm H2O (p<0.05) when PEEP ventilation was commenced. No significant hemodynamic changes were observed with the application of PEEP. Venous admixture was reduced from 45 to 24 percent (p<0.001) and PaC>2 increased from 9.3 kPa (70 mm Hg) to 15.4 kPa (116 mm Hg) (p<0.001). allergy relief

Lung Function and Hemodynamics (Table 1)—Effects of PCIRV
Respiratory pressures changed markedly as an effect of PCIRV. Mean airway pressure increased from 17 cm H20 with VCV PEEP to 29 cm H20 with PCIRV (p<0.001) and there was a reduction in peak airway pressure from 44 to 35 cm H2O (p<0.001). Static compliance, FRC, and PaC>2 were not significantly altered. Cardiac output fell from 3.1 to 2.4 L/min (p<0.05) and mean systemic blood pressure fell from 97 to 82 mm Hg (p<0.05). Despite a constant minute ventilation, PaCC>2 was reduced from 5.9 kPa (44 mm Hg) to 4.9 kPa (37 mm Hg) (p<0.05). Physiologic dead-space decreased from 24 percent to 20 percent (p<0.05).

Table 1—Respiratory Mechanics, Hemodynamics, and Gas Exchange

Wilcoxon’s Matched Pairs Test Repeated-Measures ANOVA
VCV ZEEP p Value VCV ZEEP VCV PEEP PCIRV
VE, L/min 7.6 ±0.8 NS 7.1 ±0.8A 7.0±0.7A 7.4± 1.0A
Peak Paw, cm H2O 23 ±4 <0.05 39±7B 44±7C 35 ±6A
Mean paw, cm H2O 5± 1 <0.05 10±3A 17 ±2B 29±5C
Pee, cm H2O 0±0 NS 0±0A 11 ± 1B 10±2B
Cstat, ml/cm H2O 32 ±7 <0.05 20±6a 27±9B 25 ± 10B
FRC, ml 421 ±65 <0.05 207 ± 75a 404± 142B 432 ±170B
HR, beats/min 136 ±25 NS 161 ±51a 156±46A 173 ±54a
SAPM, mm Hg 115 ± 17 NS 99±31a 97 ±31A 82±21a
PAPM, mm Hg 13±3 <0.05 32 ± 12a 33±11A 34 ± 10A
PAWP, mm Hg 4±2 <0.05 7±2A 10±3B 12 ±3C
CO, L/min 4.0±0.9 NS 3.4± 1.6B 3.1 ±0.5A 2.4±0.2a
РаОг, kPa [mm Hg] 38.7 ±3.0 [290 ±23] <0.01 9.3±6.3a [70 ±47] 15.4± 12.2B [116±92] 17.5 ± 12.8B [131 ± 96]
РаСОг, kPa [mm Hg] 4.8 ±0.6 [36 ±25] <0.05 6.6± 1.5B [45± 11] 5.9± 1.3B [44 ±10] 4.9± 1.7a [37±13]
Vd/Vt, % 19 ±2 <0.05 27 ±4C 24±5B 20±7a
Qs/Qt, % 7±3 <0.01 45 ± 23B 24 ± 14a 21 ± 16A
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