PRESSURE CONSTANT VERSUS VOLUME CONSTANT VENTILATION IN CHRONIC RESPIRATORY-FAILURE

Background: Volume controlled intermittent ventilation (IPPV) via face mask is a treatment of proven efficacy for chronic respiratory failur e (CRF). Pressure support ventilation has recently been introduced in the treatment of CRF. In this study we investigated whether pressure c onstant ventilation (PCV) via face mask could be an adequate long term alternative to IPPV. Patients and Methods: We studied 30 (24 male, ag e: 52.2+/-15.9 years) patients with CRF. We measured the following par ameters at baseline, after 1, 2 and 6 months, respectively: blood gas analysis, oxygen saturation, vital capacity, forced exspiratory volume , breathing frequency, tidal volume, inspiratory mouth occlusion press ure, maximal inspiratory pressure. subjective symptom scores and venti lator acceptance scores. In all patients, we attempted to treat with I PPV over 1 month, followed by 1 month's trial of PCV. If PCV, compared to IPPV, was adequate, PCV was continued for a follow-up period of 4 months' duration. If patients deteriorated after PCV they were treated the following 4 months with IPPV. Results: In 28 out of 30 patients C RF improved concerning subjective and objective parameters. After IPPV 18 our of 28 patients changed to PCV, with an equal quality of treatm ent (PCV-responder). Ten patients were PCV-nonresponders since compare d to IPPV the subjective scores deteriorated and the PaCO2 increased a gain, In all patients of either therapy group, subjective and objectiv e parameters remained constant for another 4 months period. Ar baselin e the PCV-nonresponders had significantly higher degree of hypercapnia and oxygen desaturation; no other parameters were found to be of pred ictive value concerning the efficacy of PCV. Conclusions: PCV proved t o be an alternative to IPPV in the treatment of chronic respiratory in sufficiency in approximately 60% of the patients with CRF. However the re is a subgroup with more severe CRF at baseline in whom PCV is inade quate.