title: Breathing pattern during acute respiratory failure and recovery.
abstract: The objective of this study was to compare the breathing pattern of patients who failed to wean from mechanical ventilation to the pattern during acute respiratory failure. We hypothesized that a similar breathing pattern occurs under both conditions. Breathing pattern, mouth occlusion pressure (P[0.1]) and maximum inspiratory pressure (P[I,max]) were measured in 15 patients during acute respiratory failure, within 24 h of the institution of mechanical ventilation, and in 49 patients during recovery, when they were ready for discontinuation from mechanical ventilation. The following indices were calculated: rapid shallow breathing index (respiratory frequency/tidal volume (fR/VT)); rapid shallow breathing-occlusion pressure index (ROP = P[0.1 x fR/VT]); P(0.1)/P(I,max); and effective inspiratory impedance (P[0.1]/VT/(inspiratory time (tI)). Patients who failed to wean (n=11) had a similar ROP,fR/VT and P(0.1)/P(I,max) to those with acute respiratory failure despite a significantly reduced P(0.1)/VT/tI, the value of which was comparable to that of patients who weaned successfully (n=38). The P(I,max) of patients who failed to wean was similar to that of patients who weaned successfully. We conclude that patients who failed to wean had a breathing pattern similar to that during acute respiratory failure, despite a reduced mechanical load on the respiratory muscles and a relatively adequate inspiratory muscle strength. This suggests that strategies that enhance respiratory muscle endurance may facilitate weaning.
authors.affiliation: Dept of Medicine, Long Beach Veterans Affairs Medical Center, CA 90822, USA.
authors.forename: N
authors.initials: N
authors.lastname: Del Rosario
authors.forename: C S
authors.initials: CS
authors.lastname: Sassoon
authors.forename: K G
authors.initials: KG
authors.lastname: Chetty
authors.forename: S E
authors.initials: SE
authors.lastname: Gruer
authors.forename: C K
authors.initials: CK
authors.lastname: Mahutte
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D006801:Humans; D012119:Respiration / Q000502:physiology*; D012121:Respiration, Artificial; D012131:Respiratory Insufficiency / Q000209:etiology / Q000503:physiopathology* / Q000628:therapy*; D015656:Respiratory Mechanics / Q000502:physiology; D012132:Respiratory Muscles / Q000503:physiopathology; D015300:Ventilator Weaning