In-vivo study
During the one-year study, 10 patients received both IPPV and HFOV and were recorded in both ventilatory modes. Because six patients were recorded in only one ventilatory mode, they were excluded from the analysis. Patients included had a mean ± SD gestational age at birth of 25.7 ± 0.9 weeks and a mean ± SD birth weight of 624.4 ± 96.1 g. Twenty recordings were made (10 in each ventilatory mode) at a mean ± SD postnatal age of 8.5 ± 7.7 days for HFOV and 10.9 ± 8.7 days for IPPV. Patients’ characteristics and ventilatory parameters at the time of recording are summarized in Table 2.
RH during HFOV was significantly lower than during IPPV (Table 2). Postnatal age, weight at the procedure, and environmental parameters were comparable during HFOV and IPPV, but the heater-humidifier inlet and outlet temperatures, flow rates, tidal volumes, and pressures differed significantly (Table 2).