Effect of drainage system on mean values of maximum and minimum intrapleural pressures (IPPmax and IPPmin)
| Underwater seal | Flutter valve | Difference of means | 95% CI | p value (t test) | |
|---|---|---|---|---|---|
| IPPmax (mm Hg) | −0.8 | −1.6 | 0.8 | 0 to 1.6 | 0.046 |
| IPPmin (mm Hg) | −5.6 | −7.4 | 1.8 | 0.3 to 3.3 | 0.023 |