We compared in six healthy subjects non invasive mechanical ventilation delivered by a new 'helmet' (large [L] and small [S] size) and by a standard face mask (FM). We tested three different ventilatory setting: a continuous flow CPAP (CPAPCF), a CPAP delivered by a ventilator (CPAPVent) and a pressure support ventilation (PSV). The level of PEEP and PSV were 5 cmH2O while FIO2 was 21%. Tidal volume VT, respiratory rate (RR), work of breathing (WOB L), pressure time product (PTP) were measured.
Our results suggest that during CPAP the three systems are equals while during PSV the FM is better.
Table.
| VT (l) | RR (bpm) | WOB L (J/l) | PTP (cmH2O*s/m) | |
|---|---|---|---|---|
| CPAPCF | ||||
| Helmet L | 0.42 ± 0.05 | 14.4 ± 4.1 | 0.36 ± 0.06 | 81 ± 16 |
| Helmet S | 0.44 ± 0.14 | 14.8 ± 4.3 | 0.34 ± 0.06 | 71 ± 14 |
| FM | 0.50 ± 0.07 | 14.9 ± 4.1 | 0.39 ± 0.09 | 84 ± 17 |
| CPAPVent | ||||
| Helmet L | 0.56 ± 0.16 | 14.8 ± 3.6 | 0.35 ± 0.12 | 105 ± 52 |
| Helmet S | 0.63 ± 0.12 | 13.5 ± 2.7 | 0.31 ± 0.18 | 85 ± 45 |
| FM | 0.55 ± 0.10 | 14.8 ± 4.3 | 0.26 ± 0.17 | 81 ± 49 |
| PSV | ||||
| Helmet L | 0.68 ± 0.15 | 12.5 ± 3.3 | 0.12 ± 0.1 | 28 ± 24 |
| Helmet S | 0.68 ± 0.18 | 13.1 ± 3.7 | 0.13 ± 0.1 | 30 ± 21 |
| FM | 0.62 ± 0.15 | 15.6 ± 3.6 | 0.01 ± 0.01* | 2 ± 1* |
*P < 0.05 vs helmet L and helmet S.