Physiological comparison of three spontaneous breathing trials in difficult-to-wean patients

Servei de Medicina Intensiva, Hospital Santa Creu i Sant Pau, C. Sant Quintí 89, 08041, Barcelona, Spain.
Intensive Care Medicine (Impact Factor: 7.21). 03/2010; 36(7):1171-9. DOI: 10.1007/s00134-010-1870-0
Source: PubMed


To compare cardiovascular and respiratory responses to different spontaneous breathing trials (SBT) in difficult-to-wean patients using T-piece and pressure support ventilation (PSV) with or without positive end-expiratory pressure (PEEP).
Prospective physiological study. Fourteen patients who were monitored with a Swan-Ganz catheter and had failed a previous T-piece trial were studied. Three SBTs were performed in random order in all patients: PSV with PEEP (PSV-PEEP), PSV without PEEP (PSV-ZEEP), and T-piece. PSV level was 7 cmH(2)O, and PEEP was 5 cmH(2)O. Inspiratory muscle effort was calculated, and hemodynamic parameters were measured using standard methods. RESULTS [MEDIAN (AND INTERQUARTILE RANGE)]: Most patients succeeded in the PSV-PEEP (11/14) and PSV-ZEEP (8/14) trials, but all failed the T-piece trial. Patient effort was significantly higher during T-piece than during PSV with or without PEEP [esophageal pressure-time product was 292 (238-512), 128 (58-299), and 148 (100-465) cmH(2)O x s/min, respectively, p < 0.05]. Left ventricular heart failure was observed in 11 of the 14 patients during the T-piece trial. Pulmonary artery occlusion pressure and respiratory rate were significantly higher during T-piece than with PSV-PEEP [21 (18-24) mmHg versus 17 (14-22) mmHg, p < 0.05 and 27 (21-35) breaths/min versus 19 (16-29) breaths/min, p < 0.05 respectively]. Tidal volume was significantly lower during the T-piece trial.
In this selected population of difficult-to-wean patients, PSV and PSV plus PEEP markedly modified the breathing pattern, inspiratory muscle effort, and cardiovascular response as compared to the T-piece. Caregivers should be aware of these differences in SBT as they may play an important role in weaning decision-making.

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    • "Several reversible causes such as respiratory and/or cardiac load, neuromuscular, and metabolic and endocrine disorders have been attributed as causes of difficult weaning. Besides cardiovascular-related causes [4], neuromuscular weaknesses is also a common cause of failure to wean from the ventilator; the causes include polyneuropathy and myopathy [5]. Rarely, undiagnosed, advanced cervical spondylotic myelopathy and syringomyelia may cause acute respiratory failure and subsequent failure to extubate [6]. "
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    ABSTRACT: Patient: Female, 57 Final Diagnosis: Syryngomyelia • cervical Symptoms: Acute respiratory insufficiency Medication: - Clinical Procedure: - Specialty: Pulmonology. Rare disease. Failed planned extubation occurs in a minority of patients with acute respiratory failure requiring invasive mechanical ventilation. In patients presenting with acute respiratory failure with no identifiable cardiopulmonary causes, uncommon conditions, such as cervical spondylotic myelopathy, should be considered. In very rare instances, when cervical spondylotic myelopathy and syringomyelia present concomitantly, they can be devastating. A 57-year-old woman visited the emergency room (ER) after feeling unwell for several days. She was brought to the ER with acute respiratory distress and obtunded state with GCS of 6/15. She was hypotensive and agonally breathing. Her initial neurologic evaluation was unrevealing. Based on these findings, she was intubated. Over the next several days, she was difficult to wean from the ventilator and had persistent respiratory acidosis. After a short-lived extubation, the patient was again re-intubated. This time the neurologic evaluation showed decreased movements of all muscle groups against gravity and forces, with generalized weakness. An MRI of the brain and cervical spine demonstrated moderate degenerative disc disease and syringomyelia extending from C2 to C7 level. The patient underwent de-compression laminectomy. After failing several weaning trials, she underwent bronchoscopically-assisted tracheotomy. Acute cardiopulmonary and intensive care unit-acquired neuromuscular conditions have been attributed as a major cause of difficult weaning and extubation. Failure to identify and correct other rare combinations (such as cervical degenerative disc disease and syringomyelia) may cause acute respiratory failure and subsequent failure to wean and extubation, resulting in high rates of mortality and morbidity.
    Full-text · Article · Apr 2014 · American Journal of Case Reports
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    • "During the SBT, we assessed the patients by using a standard protocol [18]. The patient was thereby completely disconnected from the ventilator to see inspiratory muscle activity during the whole inspiratory period and to avoid effects of triggering pressure support by only brief diaphragmatic contractions [24]. Conventional criteria were used to decide when to terminate the SBT. "
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    ABSTRACT: A reliable prediction of successful weaning from respiratory support may be crucial for the overall outcome of the critically ill patient. The electrical activity of the diaphragm (EAdi) allows one to monitor the patients' respiratory drive and their ability to meet the increased respiratory demand. In this pilot study we compared the EAdi to conventional parameters of weaning failure, such as the ratio of respiratory rate to tidal volume. We studied 18 mechanically ventilated patients considered difficult to wean. For a spontaneous breathing trial (SBT) the patients were disconnected from the ventilator and given oxygen through a T-piece. The SBT was evaluated using standard criteria. Twelve patients completed the spontaneous breathing trial successfully and six failed. The EAdi was significantly different in the two groups. We found an early increase in EAdi in the failing patients that was more pronounced than in any of the patients who successfully passed the SBT. Changes in EAdi predicted an SBT failure earlier than conventional parameters. EAdi monitoring adds valuable information during weaning from the ventilator and may help to identify patients, who are not ready for discontinuation of respiratory support.
    Full-text · Article · Aug 2013 · Critical care (London, England)
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    • "Although there was a significant difference in alveolar ventilation among CG and PSVG, both groups were mostly within the normal range of CO 2 (except one time in the CG) and both weaning protocols may be considered. It is likely that the pressure provided by PSV may have produced an appropriate V T , commonly not accomplished by horses at the return of spontaneous ventilation (Brochard et al. 1987; Esteban et al. 1994; Patroniti et al. 2004; Ezingeard et al. 2006; Cabello et al. 2010). This is supported by the low V T observed in horses at the first spontaneous breath (CG 3.15 AE 1.27 L and PSVG 3.02 AE 1.85 L) and by Table 2 Cardiovascular and metabolic parameters of horses from CG and PSVG (mean AE SD) "
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    ABSTRACT: To determine if pressure support ventilation (PSV) weaning from general anesthesia affects ventilation or oxygenation in horses. Prospective randomized clinical study. Twenty client-owned healthy horses aged 5 ± 2 years, weighing 456 ± 90 kg. In the control group (CG; n = 10) weaning was performed by a gradual decrease in respiratory rate (fR) and in the PSV group (PSVG; n = 10) by a gradual decrease in fR with PSV. The effect of weaning was considered suboptimal if PaCO2 > 50 mmHg, arterial pH < 7.35 plus PaCO2 > 50 mmHg or PaO2 < 60 mmHg were observed at any time after disconnection from the ventilator until 30 minutes after the horse stood. Threshold values for each index were established and the predictive power of these values was tested. Pressure support ventilation group (PSVG) had (mean ± SD) pH 7.36 ± 0.02 and PaCO2 41 ± 3 mmHg at weaning and the average lowest PaO2 69 ± 6 mmHg was observed 15 minutes post weaning. The CG had pH 7.32 ± 0.02 and PaCO2 57 ± 6 mmHg at weaning and the average lowest PaO2 48 ± 5 mmHg at 15 minutes post weaning. No accuracy in predicting weaning effect was observed for fR (p = 0.3474), minute volume (p = 0.1153), SaO2 (p = 0.1737) and PaO2/PAO2 (p = 0.1529). A high accuracy in predicting an optimal effect of weaning was observed for VT > 10 L (p = 0.0001), fR/VT ratio ≤ 0.60 breaths minute−1 L−1 (p = 0.0001), VT/bodyweight > 18.5 mL kg−1 (p = 0.0001) and PaO2/FiO2 > 298 (p = 0.0002) at weaning. A high accuracy in predicting a suboptimal effect of weaning was observed for VT < 10 L (p = 0.0001), fR/VT ratio ≥ 0.60 breaths minute−1 L−1 (p = 0.0001) and Pe′CO2 ≥ 38 mmHg (p = 0.0001) at weaning. Pressure support ventilation (PSV) weaning had a better respiratory outcome. A higher VT, VT/body weight, PaO2/FiO2 ratio and a lower fR/VT ratio and Pe′CO2 were accurate in predicting the effect of weaning in healthy horses recovering from general anesthesia.
    Full-text · Article · Apr 2013 · Veterinary Anaesthesia and Analgesia
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