Short-Term Effect of Controlled Instead of Assisted Noninvasive Ventilation in Chronic Respiratory Failure Due to Chronic Obstructive Pulmonary Disease

BACKGROUND: Noninvasive positive-pressure ventilation (NPPV) unloads respiratory muscles. Spontaneous-breathing ventilation modes require patient effort to trigger the ventilator, whereas controlled modes potentially economize on patient triggering effort and thus achieve more complete respiratory muscle rest. Data on controlled NPPV have not been published to date. We hypothesize that controlled ventilation is feasible in patients with hypercapnic chronic obstructive pulmonary disease.

METHODS: We measured blood gas values, respiratory muscle strength, spontaneous breathing pattern, and lung function before and after a 3-month period of NPPV in 305 patients (213 male, mean ± SD age 61.3 ± 8.6 y). The subjects used a controlled NPPV mode when they could tolerate it.

RESULTS: Ninety-one percent of the patients were able to adapt to a controlled NPPV mode. In those patients, daytime P_CO2 decreased from 56.7 ± 7.5 mm Hg to 47.5 ± 6.6 mm Hg (p < 0.001) and P_O2 increased from 49.2 ± 8.8 mm Hg to 56.2 ± 8.5 mm Hg (p < 0.001). Their mean maximum inspiratory pressure increased from 42.3 ± 16.9 cm H₂O to 48.4 ± 18.0 cm H₂O (p < 0.001). Their mean vital capacity increased from 1.89 ± 0.62 L to 1.99 ± 0.67 L (p = 0.004). And their spontaneous breathing pattern became less rapid and shallow.

CONCLUSIONS: Controlled NPPV is feasible in patients with hypercapnic chronic obstructive pulmonary disease. We observed improved blood gas values, lung function, and inspiratory muscle strength.