Effect of Different Levels of Pressure Support and Proportional Assist Ventilation on Breathing Pattern, Work of Breathing and Gas Exchange in Mechanically Ventilated Hypercapnic COPD Patients with Acute Respiratory Failure

• Published in: Respiration Vol. 70; no. 4; pp. 355 - 361
• Main Authors: Passam, F., Hoing, S., Prinianakis, G., Siafakas, N., Milic-Emili, J., Georgopoulos, D.
• Format: Journal Article
• Language: English
• Published: Basel, Switzerland Karger 01.07.2003; S. Karger AG
• Subjects: Acute Disease; Aged; Airway Resistance; Anesthesia. Intensive care medicine. Transfusions. Cell therapy and gene therapy; Biological and medical sciences; Clinical Investigations; Emergency and intensive respiratory care; Female; Hemodynamics; Humans; Hypercapnia - etiology; Intensive care medicine; Male; Medical sciences; Middle Aged; Positive-Pressure Respiration - methods; Pulmonary Disease, Chronic Obstructive - complications; Pulmonary Disease, Chronic Obstructive - physiopathology; Pulmonary Disease, Chronic Obstructive - therapy; Pulmonary Gas Exchange; Respiration, Artificial - methods; Respiratory Insufficiency - etiology; Respiratory Mechanics; Work of Breathing; Pressure support ventilation; Hypercapnia; Acute respiratory failure; Proportional assist ventilation; COPD; Intensive care; Artificial ventilation; Respiratory failure; Mechanic of breathing; Bronchus disease; Complication; Obstructive pulmonary disease; Human; Lung disease; Assisted ventilation; Respiratory disease; Acute; Method; Metabolism; Chronic; Treatment; Gas exchange; Respiration; Mechanical ventilation; Comparative study
• ISSN: 0025-7931; 1423-0356
• DOI: 10.1159/000072897

Background: Proportional assist ventilation (PAV) has been shown to maintain better patient-ventilator synchrony than pressure support ventilation (PSV); however, its clinical advantage regarding invasive ventilation of COPD patients has not been clarified. Objectives: To compare the effect of PAV and PSV on respiratory parameters of hypercapnic COPD patients with acute respiratory failure (ARF). Methods: Nine intubated hypercapnic COPD patients were placed on the PAV or PSV mode in random sequence. For each mode, four levels (L 1 –L 4 ) of support were applied. At each level, blood gases, flow, tidal volume (V T ), airway pressure (Paw), esophageal pressure (Pes) (n = 7), patient respiratory rate (fp), ventilator rate (fv), missing efforts (ME = fp – fv) were measured. Results: We found increases in ME with increasing levels of PSV but not with PAV. PO 2 and V T increased whereas PCO 2 decreased significantly with increasing levels of PSV (p < 0.05). With PAV, PCO 2 decreased and V T increased significantly only at L 4 whereas PO 2 increased from L 1 to L 4 . Runaways were observed at L 3 and L 4 of PAV. The pressure-time product (PTP) was determined for effective and missing breaths. The mean total PTP per minute (of effective plus missing breaths) was 160 ± 57 cm H 2 O/s·min in PSV and 194 ± 60 cm H 2 O/s·min in PAV. Conclusion: We conclude that in COPD patients with hypercapnic ARF, with increasing support, PSV causes the appearance of ME whereas PAV develops runaway phenomena, due to the different patient-ventilator interaction; however, these do not limit the improvement of blood gases with the application of both methods.