Usefulness of P_0.1 in the Follow-Up of Individuals With Air Trapping and Home Noninvasive Ventilation and CPAP

The ventilatory mechanics of patients with COPD and obesity-hypoventilation syndrome (OHS) are changed when there is air trapping and auto-PEEP, which increase respiratory effort. P_0.1 measures the ventilatory drive and, indirectly, respiratory effort. The aim of the study was to measure P_0.1 in subjects with COPD or OHS on treatment with positive pressure and to analyze their changes in P_0.1 after treatment.

With a prospective design, subjects with COPD and OHS were studied in whom positive airway pressure was applied in their treatment. P_0.1 was determined at study inclusion and after 6 months of treatment.

A total of 88 subjects were analyzed: 56% were males, and the mean age of 65 ± 9 y old. Fifty-four (61%) had OHS, and 34 (39%) had COPD. Fifty (56%) had air trapping, with an initial P_0.1 value of 3.0 ± 1.3 cm H₂O compared with 2.1 ± 0.7 cm H₂O for subjects who did not have air trapping (P = .001). After 6 months of treatment, subjects who had air trapping had similar P_0.1 as those who did not: 2.3 ± 1.1 and 2.1 ± 1 cm H₂O, respectively (P = .53). In subjects with COPD, initial P_0.1 was 2.9 ± 1.4 cm H₂O and at 6 months 2.2 ± 1.1 cm H₂O (P = .02). In subjects with OHS, initial P_0.1 was 2.4 ± 1.1 cm H₂O and at 6 months 2.2 ± 1.0 cm H₂O (P = .28).

COPD and air trapping were associated with greater P_0.1 as a marker of respiratory effort. A decrease in P_0.1 indicates lower respiratory effort after treatment.