Abstract 30

Background: In animal experiments has been shown that HFO leads to less damage of the pulmonary epithelium of the small airways compared to IPPV. To investigate if this difference in tissue damage might be reflected also in static compliance and in the compliance of the inspiratory or expiratory limb of the pressure-volume loop we investigated premature lambs after 8 hours ventilatory support with IPPV or HFO. The Stability Index according to Greenwald (SI) and the Expansion Index according to Clements (EI) were calculated also.

Subjects and measurements: Lambs were delivered by cesarean section at 132 days gestational age (term 145 days), were ventilated with HFO (n=10) or IPPV (n=8). After 8 hours the lungs were carefully excised and static compliance Cstat(δV/δP × body weight) measured. δV from 10 to 20 cm H2O/10 × body weight was defined as Inspiratory Compliance (Ci) while δV from 20 to 10 cm H20/10 × body weight was defined as Expiratory Compliance (Ce). The SI was defined as 2 × V at 5 cmH20 + V at 10 cm H20/ V at 30 cm H20. The EI was defined as (V at 5 cmH2O / V at 30 cm H2O) × 100%.

Results: Table 1: Pulmonary mechanical differences between HFO and IPPV ventilated lambs.

Table 1 No caption available.
Full size table

Conclusion: Although not significant, HFO ventilated lungs show higher inspiratory compliance (p=0.08), probably due to less atelectasis as a reflection of better surfactant function, preventing pulmonary collaps during deflation.