Patient-ventilator asynchrony during noninvasive ventilation: the role of expiratory trigger

• Published in: Intensive care medicine Vol. 25; no. 7; pp. 662 - 667
• Main Authors: Calderini, E., Confalonieri, M., Puccio, P. G., Francavilla, N., Stella, L., Gregoretti, C.
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer 01.07.1999; Berlin Springer Nature B.V
• Subjects: Acquired immune deficiency syndrome; Adult; AIDS; AIDS-Related Opportunistic Infections - complications; AIDS-Related Opportunistic Infections - physiopathology; Anesthesia. Intensive care medicine. Transfusions. Cell therapy and gene therapy; Biological and medical sciences; Catheters; Critical Care - methods; Cycles; Emergency and intensive respiratory care; Equipment Failure; Esophagus; Failure; Humans; Immune system; Immunodeficiency; Intensive care medicine; Male; Masks; Mechanical ventilation; Medical sciences; Middle Aged; Oxygen; Patients; Pneumonia, Pneumocystis - complications; Pneumonia, Pneumocystis - physiopathology; Population studies; Positive-Pressure Respiration - instrumentation; Pressure; Pressure transducers; Respiration; Respiratory Distress Syndrome, Adult - etiology; Respiratory Distress Syndrome, Adult - physiopathology; Respiratory Distress Syndrome, Adult - therapy; Respiratory failure; Respiratory rate; Synchronism; Time Factors; Ventilation; Ventilators; Ventilators, Mechanical - standards; United States > US; Italy; Sweden; Human; Air leak; Intensive care; Assisted ventilation; Respiratory disease; Acute; Mask; Patient; Artificial ventilation; Fan; Treatment; Asynchronism; Respiratory failure; Non invasive method; Complication
• ISSN: 0342-4642; 1432-1238; 1432-1238
• DOI: 10.1007/s001340050927

Air leaks around the mask are very likely to occur during noninvasive ventilation, in particular when prolonged ventilatory treatment is required. It has been suggested that leaks from the mask may impair the expiratory trigger cycling mechanism when inspiratory pressure support ventilation (PSV) is used. The aim of this study was to compare the short-term effect of two different expiratory cycling mechanisms (time-cycled vs flow-cycled) during noninvasive inspiratory pressure support ventilation (NIPSV) on patient-ventilator synchronisation in severe hypoxemic respiratory failure. Six patients with acute lung injury (ALI) due to acquired immunodeficiency syndrome (AIDS)-related opportunistic pneumonia were enrolled in the protocol. Each subject was first studied during spontaneous breathing with a Venturi oxygen mask (SB) and successively submitted to a randomly assigned 20' conventional flow-cycling (NIPSVfc) or time-cycling inspiratory pressure support ventilation (NIPSVtc). The pre-set parameters were: inspiratory pressure of 10 cm H2O, PEEP of 5 cm H2O for the same inspired oxygen fraction as during SB. A tight fit of the mask was avoided in order to facilitate air leaks around the mask. The esophageal pressure time product (PTPes) and tidal swings (delta Pes) were measured to evaluate the patient's respiratory effort. A subjective "comfort score" and the difference between patient and machine respiratory rate [delta RR(p-v)], calculated on esophageal and airway pressure curves, were used as indices of patient-machine interaction. Air leaks through the mask occurred in five out of six patients. The values of PEEPi (< 1.9 cm H2O) excluded significant expiratory muscle activity. NIPSVtc significantly reduced PTPes, delta Pes, and delta RR(p-v) when compared to NIPS-Vfc [230 +/- 41 (SE) vs 376 +/- 72 cm H2O.s.min-1; 8 +/- 2 vs 13 +/- 2 cm H2O; 1 +/- 1 vs 9 +/- 2 br.min-1; respectively] with a concomitant significant improvement of the "comfort score". In the presence of air leaks a time-cycled expiratory trigger provides a better patient-machine interaction than a flow-cycled expiratory trigger during NIPSV.