Breathing Frequency and Pattern Are Poor Predictors of Work of Breathing in Patients Receiving Pressure Support Ventilation

Banner, Michael J.; Kirby, Robert R.; Kirton, Orlando C.; DeHaven, C. Bryan; Blanch, Paul B.

doi:10.1378/chest.108.5.1338

Cited by 36 publications

(22 citation statements)

References 21 publications

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“…In some patients respiratory rate is fairly insensitive to level of support. This conclusion is further supported by recent findings that respiratory rate is not a good predictor of work of breathing or pressure-time product during PSV (16,26). 3.…”

Section: Discussionsupporting

confidence: 80%

Response of Ventilator-dependent Patients to Different Levels of Pressure Support and Proportional Assist

Giannouli

Webster

Roberts

et al. 1999

Am J Respir Crit Care Med

156

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The ventilator's response to the patient's effort is quite different in proportional assist ventilation (PAV) and pressure support ventilation (PSV). We wished to determine whether this results in different ventilatory and breathing pattern responses to alterations in level of support and, if so, whether there are any gas exchange consequences. Fourteen patients were studied. Average elastance (E) was 22.8 (range, 14 -36) cm H2O/L and average resistance (R) was 15. 7 (range, 9-21) cm H2O/L/s. The highest PSV support (PSVmax) was that associated with a tidal volume (VT) of 10 ml/kg (20.4 +/- 3.2 cm H2O), and the highest level of PAV assist (PAVmax) was 78 +/- 7% of E and 76 +/- 7% of R. Level of assist was decreased in steps to the lowest tolerable level (PSVmin, PAVmin). Minute ventilation, VT, ventilator rate (RRvent), and arterial gas tensions were measured at each level. We also determined the patient's respiratory rate (RRpat) by adding the number of ineffective efforts (DeltaRR) to RRvent. There was no difference between PSVmin and PAVmin in any of the variables. At PSVmax, VT was significantly higher (0.90 +/- 0.30 versus 0.51 +/- 0.16 L) and RRvent was significantly lower (13.2 +/- 3.9 versus 27.6 +/- 10.5 min-1) than at PAVmax. The difference in RRvent was largely related to a progressive increase in ineffective efforts on PSV as level increased (DeltaRR 12.1 +/- 10.1 vs 1.4 +/- 2.1 with PAVmax); there was no significant difference in RRpat. The differences in breathing pattern had no consequence on arterial blood gas tensions. We conclude that substantial differences in breathing pattern may occur between PSV and PAV and that these are largely artifactual and related to different patient-ventilator interactions.

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Section: Discussionsupporting

confidence: 80%

Response of Ventilator-dependent Patients to Different Levels of Pressure Support and Proportional Assist

Giannouli

Webster

Roberts

et al. 1999

Am J Respir Crit Care Med

156

View full text Add to dashboard Cite

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“…Unfortunately, in an individual sence of definitive evidence demonstrating that a failed weaning trial adversely effects outcome. If patient the PSV level required to offset the imposed load, while simultaneously avoiding either over-or this proves to be the case, then there is little rationale for trying to predict the outcome of a trial of undercompensation, may vary from 3 to 14 cmH 2 O [85,86]. Two studies compared CPAP versus T-piece discontinuation.…”

Section: Although the Predictive Accuracy Of The Nif/mipmentioning

confidence: 99%

Controversies in Weaning from Mechanical Ventilation

Epstein

2001

J Intensive Care Med

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Invasive mechanical ventilation can successfully support the patient with acute respiratory failure, but it is associated with considerable risks. Numerous complications of invasive mechanical ventilation have been identified, and these may contribute to increased mortality. Therefore after clinical improvement has occurred, considerable emphasis is placed on expeditiously freeing the patient from the ventilator. This process of getting a patient off mechanical ventilation has been variably termed weaning, liberation, or discontinuation (terms which may be used interchangeably), and can be further divided into “readiness testing” and “progressive withdrawal.” Over the last decade, new developments in our understanding of the process of weaning have provided investigators with the tools to address a number of key questions: How should readiness for weaning (and trials of spontaneous breathing) be determined? What is the role of weaning parameters in deciding when to initiate the weaning process? What is the best mode for conducting a spontaneous breathing trial and how should the patient be monitored? What are the mechanisms for weaning (and spontaneous breathing trial) failure? What is the best technique to facilitate progressive withdrawal? What other factors can facilitate liberation from mechanical ventilation? What are the risks of extubation failure and how can extubation outcome best be predicted? What is the role for protocols in facilitating weaning from mechanical ventilation?.

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“…However, the variables of the breathing pattern commonly used at the bedside appear to be inaccurate and misleading interferences of the inspiratory work [16]. Using only the breathing pattern as the primary criterion to detect patients with a good evolution could result in an inappropriate overload of respiratory muscles.…”

Section: Discussionmentioning

confidence: 99%

“…Using only the breathing pattern as the primary criterion to detect patients with a good evolution could result in an inappropriate overload of respiratory muscles. The inspiratory work should then be measured simultaneously with the breathing pattern [16], but this is sometimes difficult in the clinical setting.…”

Section: Discussionmentioning

confidence: 99%

Influence of Respiratory Behavior on Ventilation, Respiratory Work and Intrinsic PEEP during Noninvasive Nasal Pressure Support Ventilation in Normal Subjects

Vanpee

el-Khawand²,

Rousseau³

et al. 2002

Respiration

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Background: In clinical practice, patients have different inspiratory behaviors during noninvasive pressure support ventilation (PSV): some breathe quietly, others actively help PSV by an additional effort, and others even resist the inspiratory pressure of PSV. Objective: What is the influence of patient collaboration (inspiratory behavior) on the efficiency of PSV? Methods: We ventilated 10 normal subjects with nasal PSV (inspiratory/expiratory: 10/0 and 15/5 cm H₂O) and measured their flow and volume with a pneumotachograph and their esophageal and gastric pressures during three different respiratory voluntary behaviors: relaxed inspiration, active inspiratory work and resisted inspiration. Results: When compared with relaxed inspiration with 10/0 cm H₂O PSV: (1) an active inspiratory effort increased tidal volume (from 789 ± 356 to 1,046 ± 586 ml; p = 0.006), minute ventilation (from 10.40 ± 4.45 to 15.77 ± 7.69 liters/min; p < 0.001), transdiaphragmatic work per cycle (from 0.55 ± 0.33 to 1.72 ± 1.40 J/cycle; p = 0.002) and inspiratory work per cycle (from 0.14 ± 0.20 to 1.26 ± 1.01 J/cycle; p = 0.003); intrinsic positive end-expiratory pressure (PEEP_i) increased from 1.23 ± 1.02 to 3.17 ± 2.30 cm H₂O; p = 0.002); (2) a resisted inspiration decreased tidal volume (to 457 ± 230 ml; p = 0.007), minute ventilation (to 6.93 ± 3.04 liters/min; p = 0.028) along with a decrease in transdiaphragmatic work but no change in PEEP_i. Data obtained during a bilevel PSV of 15/5 cm H₂O were similar to those obtained with the 10/0 cm H₂O settings. Conclusions: Active inspiratory effort increases ventilation during PSV at the expense of an increased breathing work and PEEP_i. Resisted inspiration inversely decreases inspiratory work and ventilation with no air trapping. These differences between inspiratory behaviors could affect the expected beneficial effects of PSV in acutely ill patients.

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Breathing Frequency and Pattern Are Poor Predictors of Work of Breathing in Patients Receiving Pressure Support Ventilation

Cited by 36 publications

References 21 publications

Response of Ventilator-dependent Patients to Different Levels of Pressure Support and Proportional Assist

Response of Ventilator-dependent Patients to Different Levels of Pressure Support and Proportional Assist

Controversies in Weaning from Mechanical Ventilation

Influence of Respiratory Behavior on Ventilation, Respiratory Work and Intrinsic PEEP during Noninvasive Nasal Pressure Support Ventilation in Normal Subjects

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