Airway occlusion pressure to titrate positive end-expiratory pressure in patients with dynamic hyperinflation

Background: Although the use of external positive end-expiratory pressure ( PEEP) is recommended for patients with intrinsic PEEP, no simple method exi sts for bedside titration. We hypothesized that the occlusion pressure, mea sured from airway pressure during the phase of ventilator triggering (P-0.1 t), could help to indicate the effects of PEEP on the work of breathing (WO B), Methods: Twenty patients under assisted ventilation with chronic obstructiv e pulmonary disease mere studied with 0, 5, and 10 cm H2O of PEEP while ven tilated with a fixed level of pressure support. Results: PEEP 5 significantly reduced intrinsic PEEP (mean +/- SD, 5.2 +/- 2.4 cm H2O at PEEP 0 to 3.6 +/- 1.9 at PEEP 5; P < 0.001), WOB per min (12. 6 +/- 6.7 J/min to 9.1 +/- 5.9 J/min; P = 0.003), WOB per liter (1.2 +/- 0. 4 J/1 to 0.8 +/- 0.4 J/1; P < 0.001), pressure time product of the diaphrag m (216 +/- 86 cm H2O . s(-1) min(-1) to 155 +/- 179 cm H2O . s(-1) min(-1); P = 0.001) and P-o.1t (3.3 +/- 1.5 cm H2O to 2.3 +/- 1.4 cm H2O; P = 0.002 ), At PEEP 10, no further significant reduction in muscle effort nor in P-0 .1t (2.5 +/- 2.1 cm H2O) occurred, and transpulmonary pressure indicated an increase in end-expiratory lung volume. Significant correlations were foun d between WOB per min and P-0.1t at the three levels of PEEP (P < 0.001), a nd between the changes in P-0.1t versus the changes in WOB per min (P < 0.0 05), indicating that P-0.1t and WOB changed in the same direction. A decrea se in P0.1 with PEEP indicated a decrease in intrinsic PEEP with a specific ity of 71% and a sensitivity of 88% and a decrease in WOB with a specificit y of 86% and a sensitivity of 91%. Conclusion: These results show that P-0.1t may help to assess the effects o f PEEP in patients with intrinsic PEEP.