Usefulness of P0.1 in the Follow-Up of Individuals With Air Trapping and Home Noninvasive Ventilation and CPAP.

BACKGROUND: 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. P0.1 measures the ventilatory drive and, indirectly, respiratory effort. The aim of the study was to measure P0.1 in subjects with COPD or OHS on treatment with positive pressure and to analyze their changes in P0.1 after treatment. METHODS: With a prospective design, subjects with COPD and OHS were studied in whom positive airway pressure was applied in their treatment. P0.1 was determined at study inclusion and after 6 months of treatment. RESULTS: 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 P0.1 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 P0.1 as those who did not: 2.3 ± 1.1 and 2.1 ± 1 cm H2O, respectively (P = .53). In subjects with COPD, initial P0.1 was 2.9 ± 1.4 cm H2O and at 6 months 2.2 ± 1.1 cm H2O (P = .02). In subjects with OHS, initial P0.1 was 2.4 ± 1.1 cm H2O and at 6 months 2.2 ± 1.0 cm H2O (P = .28). CONCLUSIONS: COPD and air trapping were associated with greater P0.1 as a marker of respiratory effort. A decrease in P0.1 indicates less respiratory effort after treatment.

Measurement of upper airway resistances: A simple way to assess its collapsibility?

PURPOSE: The collapsibility of the upper airway is a key factor in the pathogenesis of obstructive sleep apnea (OSA). The exact measurement of this parameter, typically performed by obtaining the critical pressure (Pcrit), has not been introduced into clinical practice. The techniques that are used to measure the upper airway resistance could provide information on its the collapsibility of the airway. The aim of this study was to associate resistance in the upper airway with the presence of OSA. METHODS: Using a cross-sectional design with a control group, consecutive cases that were seen in the Chest Diseases Sleep Unit were recruited after undergoing nocturnal polysomnography. The upper airway collapsibility was determined based on the change in its resistance from the standing position to the supine position with a flow interruption (Rint) device by measuring the angle formed between the pressure/flow lines (PF angle) between the two positions. RESULTS: The PF angle was greater in the OSA group than in the controls: 7.5° (4) vs. 4° (2) (P < .001), with a positive correlation between the width of the angle and the apnea-hypopnea index (AHI) (r: 0.28, P = .03). Placing the threshold level at 10°, a sensitivity of 25% was obtained, along with a specificity of 96%, for the diagnosis of OSA. CONCLUSION: The measurement of resistance in the upper airway using flow interruption (Rint) can predict the presence of moderate and severe OSA with high specificity but low sensitivity.