Chest
Clinical Investigations in Critical CareBreathing Frequency and Pattern Are Poor Predictors of Work of Breathing in Patients Receiving Pressure Support Ventilation
Section snippets
Materials and Methods
Sixty-seven adults (42 men and 25 women) admitted to the surgical ICU who were diagnosed as having acute respiratory failure from various etiologies were studied after obtaining informed consent from the patient's family. The study was approved by the Institutional Review Boards at Shands Hospital at the University of Florida Medical Center and at the Jackson Memorial Medical Center at the University of Miami. Patients in the study population were diagnosed as having moderate to severe forms of
Results
Measured values for WOB ranged from 0 to 2.2 J/L. The level of PSV applied ranged from 5 to 50 cm H2O. All breathing pattern variables poorly predicted WOB as evidenced by the low values for the coefficients of determination (r2). For each variable, r2 predicts or explains the amount of variance in WOB. A variable with an r2 value between 0.64 and 0.81 is considered high and thus, a fairly good predictor.19 The f correlated positively with WOB and predicted only 22% of the variance in WOB (
Discussion
The main finding of this study is that, for adults with abnormal pulmonary mechanics and loaded respiratory muscles who are in respiratory failure and being treated with PSV, the f and the breathing pattern are poor inferences of the WOB. Our study reveals that WOB should be measured directly because f, for example, appears to be an inaccurate and misleading variable from which to infer the respiratory muscle workload. The clinical implication of these findings brings into question the
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2023, The Lancet Respiratory MedicineOesophageal pressure and respiratory muscle ultrasonographic measurements indicate inspiratory effort during pressure support ventilation
2020, British Journal of AnaesthesiaCitation Excerpt :As a consequence, spontaneous breathing during mechanical ventilation has been considered a ‘double-edged sword’,23 requiring an appropriate bedside monitoring of inspiratory effort. Despite being suggestive of an increased workload, specific breathing patterns, the use of accessory muscles, an increased ventilatory frequency or a reduced tidal volume, and the inspection of ventilator waveforms do not allow any quantitative assessment of breathing effort.6,24 The contraction of inspiratory muscles increases the size of the ribcage, reducing pleural pressure.
Respiratory work and pattern with different proportional assist ventilation levels
2009, Medicina Intensiva
This paper was presented in part at the annual meeting of the American Society of Anesthesiologists, October 12, 1993, Washington, DC.