Rapid shallow breathing index

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The rapid shallow breathing index (RSBI) or Yang Tobin index is a tool that is used in the weaning of mechanical ventilation on intensive care units. The RSBI is defined as the ratio of respiratory frequency to tidal volume (f/VT). People on a ventilator who cannot tolerate independent breathing tend to breathe rapidly (high frequency) and shallowly (low tidal volume), and will therefore have a high RSBI. [1] The index was introduced in 1991 by Karl Yang and Martin J. Tobin.

Contents

Equation

where

is the respiratory rate (breaths/minute)

is the tidal volume (liters)

Measurement

In the original study, measurement was done with a handheld spirometer attached to the endotracheal tube while a patient breathes room air for one minute without any ventilator assistance. [2] In contemporary ICUs, RSBI is often assessed while a patient is on Pressure Support Ventilation during a Spontaneous Breathing Trial.

Example

As an example, a patient who has a respiratory rate of 25 breaths/min and an average tidal volume of 250 mL/breath has an RSBI = (25 breaths/min)/(0.25 L) = 100 breaths/min/L.

In contrast, the 'average' patient breathing 12 breaths/min, with a tidal volume of 420 mL/breath (70kg x 6 mL/kg) would have an RSBI = (12 breaths/min)/(.420 L) = 28 breaths/min/L.

The higher the RSBI, the more distressed the patient is generally considered to be.

History

The concept was introduced in a 1991 paper by physicians Karl Yang and Martin J. Tobin from the University of Texas Health Science Center at Houston and Stritch School of Medicine at Loyola University in Chicago. [1] It was a small single center trial that used 100 patients (n=36 derivation cohort, n=64 validation cohort).

Weaning readiness

A RSBI score of less than 65 [3] indicating a relatively low respiratory rate compared to tidal volume is generally considered as an indication of weaning readiness. A patient with a rapid shallow breathing index (RSBI) of less than 105 has an approximately 80% chance of being successfully extubated, whereas an RSBI of greater than 105 virtually guarantees weaning failure. [4] Other criteria that have been suggested for a successful weaning trial include the ability to (1) tolerate a Spontaneous breathing trial for 30 minutes (in most patients, SBT failure will occur within approximately 20 minutes), (2) maintain a respiration rate of less than 35/min, and (3) keep an oxygen saturation of 90% without arrhythmias; sudden increases in heart rate and blood pressure; or development of respiratory distress, diaphoresis, or anxiety. Once the SBT is tolerated, the ability to clear secretions, a decreasing secretion burden, and a patent upper airway are other criteria that should be met to increase extubation success. Patients should be assessed daily for their readiness to be weaned from mechanical ventilation by withdrawing sedation and performing a spontaneous breathing trial.

Limitations of RSBI

Although widely used as a measure of readiness to liberate from mechanical ventilation, RSBI has been criticized due to several limitations. [5] [6]

Lack of Specificity and Sensitivity

In a meta-analysis of 48 studies, RSBI had only moderate sensitivity (83%) and poor specificity (58%), [7] suggesting that patients who are truly ready for extubation might be missed if RSBI alone is used and that a significant number of patients with "acceptable" RSBI values (<105) may still fail extubation.

Single-Point Measurement

RSBI is usually measured at a single time point, often after a short spontaneous breathing trial (SBT). This does not account for fatigue or changes over time, which can be crucial for weaning success.

Does Not Consider Work of Breathing

RSBI only assesses frequency and tidal volume, but ignores inspiratory effort and respiratory muscle workload. A patient with high work of breathing (e.g., using accessory muscles) might still have a normal RSBI.

Influence of Ventilator Settings and Support

Prior ventilator settings can significantly affect the RSBI. Several studies have found marked variations in RSBI when different ventilation strategies (PSV, CPAP, T-piece) were employed. [8] [9] [10]

Poor Performance in Certain Patient Populations

COPD Patients: Chronic airflow limitation can lead to a misleading RSBI. Alternative thresholds (e.g. RSBI < 85) may perform better in people with COPD. [11]

Neuromuscular Disease: These patients may have normal RSBI but still fail extubation due to poor cough or secretion clearance.

Obesity: Altered chest wall mechanics can make RSBI less predictive.

Influence of Anxiety and Psychological Factors

Patients who are anxious or in pain may have a temporarily elevated RSBI due to rapid breathing, even if they are otherwise ready to liberate from mechanical ventilation.

References

  1. 1 2 Yang KL, Tobin MJ (May 1991). "A prospective study of indexes predicting the outcome of trials of weaning from mechanical ventilation". N. Engl. J. Med. 324 (21): 1445–50. doi: 10.1056/NEJM199105233242101 . PMID   2023603.
  2. Yang KL, Tobin MJ (1991). "A prospective study of indexes predicting the outcome of trials of weaning from mechanical ventilation". N Engl J Med. 324 (21): 1445–50. doi: 10.1056/NEJM199105233242101 . PMID   2023603.
  3. Meade M, Guyatt G, Cook D, Griffith L, Sinuff T, Kergl C, et al. (2001). "Predicting success in weaning from mechanical ventilation". Chest. 120 (6 Suppl): 400S –24S. doi:10.1378/chest.120.6_suppl.400s. PMID   11742961.
  4. McConville JF, Kress JP (Dec 2012). "Weaning patients from the ventilator". N Engl J Med. 367 (23): 2233–9. doi:10.1056/NEJMra1203367. PMID   23215559.
  5. Trivedi, Vatsal; Chaudhuri, Dipayan; Jinah, Rehman; Piticaru, Joshua; Agarwal, Arnav; Liu, Kuan; McArthur, Eric; Sklar, Michael C.; Friedrich, Jan O.; Rochwerg, Bram; Burns, Karen E. A. (January 2022). "The Usefulness of the Rapid Shallow Breathing Index in Predicting Successful Extubation: A Systematic Review and Meta-analysis". Chest. 161 (1): 97–111. doi:10.1016/j.chest.2021.06.030. ISSN   1931-3543. PMID   34181953.
  6. Jia, Donghui; Wang, Hengyang; Wang, Qian; Li, Wenrui; Lan, Xuhong; Zhou, Hongfang; Zhang, Zhigang (2024-02-01). "Rapid shallow breathing index predicting extubation outcomes: A systematic review and meta-analysis" . Intensive and Critical Care Nursing. 80 103551. doi:10.1016/j.iccn.2023.103551. ISSN   0964-3397.
  7. Trivedi, Vatsal; Chaudhuri, Dipayan; Jinah, Rehman; Piticaru, Joshua; Agarwal, Arnav; Liu, Kuan; McArthur, Eric; Sklar, Michael C.; Friedrich, Jan O.; Rochwerg, Bram; Burns, Karen E. A. (January 2022). "The Usefulness of the Rapid Shallow Breathing Index in Predicting Successful Extubation: A Systematic Review and Meta-analysis". Chest. 161 (1): 97–111. doi:10.1016/j.chest.2021.06.030. ISSN   1931-3543. PMID   34181953.
  8. El-Khatib, Mohamad F.; Zeineldine, Salah M.; Jamaleddine, Ghassan W. (March 2008). "Effect of pressure support ventilation and positive end expiratory pressure on the rapid shallow breathing index in intensive care unit patients". Intensive Care Medicine. 34 (3): 505–510. doi:10.1007/s00134-007-0939-x. ISSN   0342-4642. PMID   18060662.
  9. Patel, Kapil N.; Ganatra, Kalpesh D.; Bates, Jason H. T.; Young, Michael P. (November 2009). "Variation in the rapid shallow breathing index associated with common measurement techniques and conditions". Respiratory Care. 54 (11): 1462–1466. ISSN   0020-1324. PMID   19863829.
  10. El-Khatib, Mohamad F.; Jamaleddine, Ghassan W.; Khoury, Andre R.; Obeid, Mounir Y. (February 2002). "Effect of continuous positive airway pressure on the rapid shallow breathing index in patients following cardiac surgery". Chest. 121 (2): 475–479. doi:10.1378/chest.121.2.475. ISSN   0012-3692. PMID   11834660.
  11. Goharani, Reza; Vahedian-Azimi, Amir; Galal, Iman H.; Souza, Leonardo Cordeiro de; Farzanegan, Behrooz; Bashar, Farshid R.; Vitacca, Michele; Shojaei, Seyedpouzhia; Mosavinasab, Seyed M. M.; Takaki, Shunsuke; Miller, Andrew C. (April 2019). "A rapid shallow breathing index threshold of 85 best predicts extubation success in chronic obstructive pulmonary disease patients with hypercapnic respiratory failure". Journal of Thoracic Disease. 11 (4): 1223–1232. doi: 10.21037/jtd.2019.03.103 . ISSN   2077-6624. PMC   6531712 . PMID   31179064.