Analyzing key elements of breathing patterns, deriving remaining variables, and identifying cutoff values in individuals with chronic respiratory disease and healthy subjects

BACKGROUND

Pulmonary physiology encompasses intricate breathing patterns (BPs), characterized by breathing frequency (Bf), volumes, and flows. The complexities intensify in the presence of interstitial lung disease (ILD) and chronic obstructive pulmonary disease (COPD), especially during exercise. This study seeks to identify pivotal factors driving changes among these variables and establish cutoff values, comparing their efficacy in differentiating BPs to traditional methods, specifically a breathing reserve (BR) of 30% and a Bf of 50 bpm.

METHODS

Screening 267 subjects revealed 23 with ILD, 126 with COPD, 33 healthy individuals, and the exclusion of 85 subjects. Lung function tests and ramp-pattern cardiopulmonary exercise testing (CPET) were conducted, identifying crucial BP elements. Changes were compared between groups at peak exercise. The area under the receiver operating characteristic curve (AUC) analysis determined cutoff values.

RESULTS

Inspiratory time (TI) remained constant at peak exercise for all subjects (two-group comparisons, all p=NS). Given known differences in expiratory time (TE) and tidal volume (VT) among ILD, COPD, and healthy states, constant TI could infer patterns for Bf, total breathing cycle time (TTOT=60/Bf), I:E ratio, inspiratory duty cycle (IDC, TI/TTOT), rapid shallow breathing index (Bf/VT), tidal inspiratory and expiratory flows (VT/TI and VT/TE), and minute ventilation (V̇E=Bf×VT) across conditions. These inferences aligned with measurements, with potential type II errors causing inconsistencies. RSBI of 23 bpm/L and VT/TI of 104 L/min may differentiate ILD from control, while V̇E of 54 L/min, BR of 30%, and VT/TE of 108 may differentiate COPD from control. BR of 21%, TE of 0.99 s, and IDC of .45 may differentiate ILD from COPD. The algorithm outperformed traditional methods (AUC 0.84-0.91 versus 0.59-0.90).

CONCLUSION

The quasi-fixed TI, in conjunction with TE and VT, proves effective in inferring time-related variables of BPs. The findings have the potential to significantly enhance medical education in interpreting cardiopulmonary exercise testing. Moreover, the study introduces a novel algorithm for distinguishing BPs among individuals with ILD, COPD, and those who are healthy.

AARC Clinical Practice Guideline: Spontaneous Breathing Trials for Liberation From Adult Mechanical Ventilation

Despite prior publications of clinical practice guidelines related to ventilator liberation, some questions remain unanswered. Many of these questions relate to the details of bedside implementation. We, therefore, formed a guidelines committee of individuals with experience and knowledge of ventilator liberation as well as a medical librarian. Using Grading of Recommendations Assessment, Development, and Evaluation (GRADE) methodology, we make the following recommendations: (1) We suggest that calculation of a rapid shallow breathing index is not needed to determine readiness for a spontaneous breathing trial (SBT) (conditional recommendation; moderate certainty); (2) We suggest that SBTs can be conducted with or without pressure support ventilation (conditional recommendation, moderate certainty); (3) We suggest a standardized approach to assessment and, if appropriate, completion of an SBT before noon each day (conditional recommendation, very low certainty); and (4) We suggest that FIO2 should not be increased during an SBT (conditional recommendation, very low certainty). These recommendations are intended to assist bedside clinicians to liberate adult critically ill patients more rapidly from mechanical ventilation.

2022 Year in Review: Ventilator Liberation

Mechanical ventilation is ubiquitous in critical care, and duration of ventilator liberation is variable and multifactorial. While ICU survival has increased over the last two decades, positive-pressure ventilation can cause harm to patients. Weaning and discontinuation of ventilatory support is the first step in ventilator liberation. Clinicians have a wealth of evidence-based literature at their disposal; however, more high-quality research is needed to describe outcomes. Additionally, this knowledge must be distilled into evidence-based practice and applied at the bedside. A proliferation of research on the subject of ventilator liberation has been published in the last 12 months. Whereas some authors have reconsidered the value of applying the rapid shallow breathing index in weaning protocols, others have begun to investigate new indices to predict liberation outcomes. New tools such as diaphragmatic ultrasonography have begun to appear in the literature as a tool for outcome prediction. A number of systematic reviews with both meta-analysis and network meta-analysis that synthesize the literature on ventilator liberation have also been published in the last year. This review describes changes in performance, monitoring of spontaneous breathing trials, and evaluations of successful ventilator liberation.

Work of Breathing During Proportional Assist Ventilation as a Predictor of Extubation Failure

BACKGROUND

Despite decades of research on predictors of extubation success, use of ventilatory support after extubation is common and 10-20% of patients require re-intubation. Proportional assist ventilation (PAV) mode automatically calculates estimated total work of breathing (total WOB). Here, we assessed the performance of total WOB to predict extubation failure in invasively ventilated subjects.

METHODS

This prospective observational study was conducted in 6 adult ICUs at an academic medical center. We enrolled intubated subjects who successfully completed a spontaneous breathing trial, had a rapid shallow breathing index < 105 breaths/min/L, and were deemed ready for extubation by the primary team. Total WOB values were recorded at the end of a 30-min PAV trial. Extubation failure was defined as any respiratory support and/or re-intubation within 72 h of extubation. We compared total WOB scores between groups and performance of total WOB for predicting extubation failure with receiver operating characteristic curves.

RESULTS

Of 61 subjects enrolled, 9.8% (n = 6) required re-intubation, and 50.8% (n = 31) required any respiratory support within 72 h of extubation. Median total WOB at 30 min on PAV was 0.9 J/L (interquartile range 0.7-1.3 J/L). Total WOB was significantly different between subjects who failed or were successfully extubated (median 1.1 J/L vs 0.7 J/L, P = .004). The area under the curve was 0.71 [95% CI 0.58-0.85] for predicting any requirement of respiratory support and 0.85 [95% CI 0.69-1.00] for predicting re-intubation alone within 72 h of extubation. Total WOB cutoff values maximizing sensitivity and specificity equally were 1.0 J/L for any respiratory support (positive predictive value [PPV] 70.0%, negative predictive value [NPV] 67.7%) and 1.3 J/L for re-intubation (PPV 26.3%, NPV 97.6%).

CONCLUSIONS

The discriminative performance of a PAV-derived total WOB value to predict extubation failure was good, indicating total WOB may represent an adjunctive tool for assessing extubation readiness. However, these results should be interpreted as preliminary, with specific thresholds of PAV-derived total WOB requiring further investigation in a large multi-center study.

The Usefulness of the Rapid Shallow Breathing Index in Predicting Successful Extubation: A Systematic Review and Meta-analysis

BACKGROUND

Clinicians use several measures to ascertain whether individual patients will tolerate liberation from mechanical ventilation, including the rapid shallow breathing index (RSBI).

RESEARCH QUESTION

Given varied use of different thresholds, patient populations, and measurement characteristics, how well does RSBI predict successful extubation?

STUDY DESIGN AND METHODS

We searched six databases from inception through September 2019 and selected studies reporting the accuracy of RSBI in the prediction of successful extubation. We extracted study data and assessed quality independently and in duplicate.

RESULTS

We included 48 studies involving RSBI measurements of 10,946 patients. Pooled sensitivity for RSBI of < 105 in predicting extubation success was moderate (0.83 [95% CI, 0.78-0.87], moderate certainty), whereas specificity was poor (0.58 [95% CI, 0.49-0.66], moderate certainty) with diagnostic ORs (DORs) of 5.91 (95% CI, 4.09-8.52). RSBI thresholds of < 80 or 80 to 105 yielded similar sensitivity, specificity, and DOR. These findings were consistent across multiple subgroup analyses reflecting different patient characteristics and operational differences in RSBI measurement.

INTERPRETATION

As a stand-alone test, the RSBI has moderate sensitivity and poor specificity for predicting extubation success. Future research should evaluate its role as a permissive criterion to undergo a spontaneous breathing trial (SBT) for patients who are at intermediate pretest probability of passing an SBT.

TRIAL REGISTRY

PROSPERO; No.: CRD42020149196; URL: www.crd.york.ac.uk/prospero/.

[Factors Related to Successful Ventilator Weaning in Respiratory Care Center Patients: A Retrospective Chart Review Study]

BACKGROUND

The subacute respiratory care unit is an important relay station where respirator-dependent patients may access subsequent chronic respiratory care. Although there is relatively little information in the literature regarding respirator disconnections in subacute respiratory care units, assisting patients to disconnect successfully from respirators is a primary challenge for care teams.

PURPOSE

The purpose of this study was to understand respirator disconnections and the factors affecting these events in subacute respiratory care units to improve the effectiveness of ventilator weaning and reduce the burden on families and medical care providers.

METHODS

This was a retrospective chart review study. Patients admitted to the subacute respiratory care unit for respiratory training during the study period from January 2016 to December 2019 were recruited as subjects and the data were collected from the Chang Gung Medical Research Database`s health insurance secondary data using a self-made transcription form.

RESULTS

The ventilator weaning success rate of the subjects in this study was 78.5%. A bivariate analysis revealed that consciousness status; disease severity; rapid shallow breathing index; days of hospitalization in a respiratory care center; days of ventilator use; blood urea nitrogen, white blood cell, hemoglobin, and blood albumin levels; and mean caloric intake were each significantly associated with successful ventilator withdrawal. The predictors of ventilator weaning in respiratory care center patients were identified as disease severity, rapid shallow breathing index, days of ventilator use, white blood cell level, and hemoglobin level.

CONCLUSIONS / IMPLICATIONS FOR PRACTICE

Respirator-dependent patients should be evaluated and monitored as early as possible. Moreover, a ventilator weaning plan should be included as a regular testing and monitoring item. Also, a respirator removal program should be provided on a case-by-case basis. Individualized ventilator weaning programs may reduce the burden on families and medical care providers.

Product of driving pressure and respiratory rate for predicting weaning outcomes

Objective

Clinicians cannot precisely determine the time for withdrawal of ventilation. We aimed to evaluate the performance of driving pressure (DP)×respiratory rate (RR) to predict the outcome of weaning.

Methods

Plateau pressure (Pplat) and total positive end-expiratory pressure (PEEPtot) were measured during mechanical ventilation with brief deep sedation and on volume-controlled mechanical ventilation with a tidal volume of 6 mL/kg and a PEEP of 0 cmH₂O. Pplat and PEEPtot were measured by patients holding their breath for 2 s after inhalation and exhalation, respectively. DP was determined as Pplat minus PEEPtot. The rapid shallow breathing index was measured from the ventilator. The highest RR was recorded within 3 minutes during a spontaneous breathing trial. Patients who tolerated a spontaneous breathing trial for 1 hour were extubated.

Results

Among the 105 patients studied, 44 failed weaning. During ventilation withdrawal, DP×RR was 136.7±35.2 cmH₂O breaths/minute in the success group and 230.2±52.2 cmH₂O breaths/minute in the failure group. A DP×RR index >170.8 cmH₂O breaths/minute had a sensitivity of 93.2% and specificity of 88.5% to predict failure of weaning.

Conclusions

Measurement of DP×RR during withdrawal of ventilation may help predict the weaning outcome. A high DP×RR increases the likelihood of weaning failure.

Statement: This manuscript was previously posted as a preprint on Research Square with the following link: https://www.researchsquare.com/article/rs-15065/v3 and DOI: 10.21203/rs.2.24506/v3

Use of the Change in Weaning Parameters as a Predictor of Successful Re-Extubation

OBJECTIVE

Weaning parameters are well studied in patients undergoing first time extubation. Fewer data exists to guide re-extubation of patients who failed their first extubation attempt. It is reasonable to postulate that improved weaning parameters between the first and second extubation attempt would lead to improved rates of re-extubation success. To investigate, we studied a cohort of patients who failed their first extubation attempt and underwent a second attempt at extubation. We hypothesized that improvement in weaning parameters between the first and the second extubation attempt is associated with successful reextubation.

INTERVENTIONS

Rapid shallow breathing index (RSBI), maximum inspiratory pressure (MIP), vital capacity (VC), and the blood partial pressure of CO2 (PaCO2) were measured and recorded in the medical record prior to extubation along with demographic information. We examined the relationship between the change in extubation and re-extubation weaning parameters and re-extubation success.

MEASUREMENTS AND MAIN RESULTS

A total of 1283 adult patients were included. All weaning parameters obtained prior to re-extubation differed between those who were successful and those who required a second reintubation. Those with reextubation success had slightly lower PaCO2 values (39.5 ± 7.4 mmHg vs. 41.6 ± 9.1 mmHg, p = 0.0045) and about 13% higher vital capacity volumes (1021 ± 410 mL vs. 907 ± 396 mL, p = 0.0093). Lower values for RSBI (53 ± 32 breaths/min/L vs. 69 ± 42 breaths/min/L, p < 0.001) and MIP (-41 ± 12 cmH2O vs. -38 ± 13 cm H2O), p = 0.0225) were seen in those with re-extubation success. Multivariable logistical regression demonstrates lack of independent associated between the change in parameters between the 2 attempts and re-extubation success.

CONCLUSIONS

The relationship between the changes in extubation parameters through successive attempts is driven primarily by the value obtained immediately prior to re-extubation. These findings do not support waiting for an improvement in extubation parameters to extubate patients who failed a first attempt at extubation if extubation parameters are compatible with success.

A Reassessment of Weaning Parameters in Patients With Spontaneous Intracerebral Hemorrhage

Background and purpose

Patients with spontaneous intracerebral haemorrhage have significant morbidity and mortality. One aspect of their care is the need for mechanical ventilation. Extubating a patient safely and efficiently is important in advancing their care; however, traditional extubation criteria using the rapid shallow breathing index and negative inspiratory force do not predict success in these patients as well as they do in other intubated patients. This study aimed to evaluate these criteria in patients with spontaneous intracerebral haemorrhage to improve the extubation success rate.

Methods

We conducted a retrospective chart review of patients with spontaneous intracerebral haemorrhage (sICH) who underwent spontaneous breathing trials from 2018 to 2020. Twenty-nine patients met the inclusion criteria, and of these 29, 20 had a trial of extubation. Rapid shallow breathing index (RSBI), negative inspiratory force (NIF), and cuff leak were recorded to analyze breathing parameters at the time of extubation. Patients who required reintubation were noted.

Results

All trials of extubation required a cuff leak. Using RSBI, patients with values <105 or <85, as the only other extubation criteria, were associated with a 70.6% and 71.4% success rate, respectively. With RSBI <105 and NIF <-25 cm water, the success rate was 88.9%. Any patient with a cuff leak that had a NIF <-30 had a success rate of 100%, regardless of RSBI.

Conclusion

The RSBI was not a reliable isolated measure to predict 100% extubation success. Using a NIF <-30 predicts a 100% extubation success rate if a cuff leak is present. This demonstrates that the NIF may be a more useful metric in sICH patients, as it accounts for patient participation and innate ability to draw a breath spontaneously. Future studies are warranted to evaluate further and optimize the extubation criteria in these patients.

Ventilatory equivalent for oxygen as an extubation outcome predictor: A pilot study

Introduction

Weaning predictors can help liberate patients in a timely manner from mechanical ventilation. Ventilatory equivalent for oxygen (VEqO₂), a surrogate for work of breathing and a measure of the efficiency of breathing, may be an important noninvasive alternative to other weaning predictors. Our study’s purpose was to observe any differences in VEqO₂ between extubation outcome groups.

Methods

Employing a metabolic cart, oxygen consumption (V^˙O₂), minute volume (VE), tidal volume (VT), and breathing frequency were recorded during a spontaneous breathing trial (SBT) to calculate VEqO₂ and the rapid shallow breathing index (RSBI) in 34 adult participants in the intensive care unit. Five-breath means of VEqO₂ and the RSBI collected throughout the SBT were examined between SBT pass and fail groups and extubation pass and fail groups using the Mann–Whitney U test with p < 0.05.

Results

Data from 31 participants were analyzed between SBT outcome groups. Data from 20 participants were examined for extubation outcome after a successful SBT. Median (interquartile range) VEqO₂ was not different between extubation groups. Participants who passed the SBT had a higher median VEqO₂ than those who did not at the midpoint (25.3 L/L V^˙O₂ [22–33 L/L V^˙O₂] vs. 23.7 L/L V^˙O₂ [18–24 L/L V^˙O₂], p = 0.035) and at the end (25.5 L/L V^˙O₂ [23–34 L/L V^˙O₂] vs. 21.3 L/L V^˙O₂ [20–24 L/L V^˙O₂], p = 0.017) of the SBT.

Discussion

VEqO₂ may show differences in SBT outcomes, but not differences between extubation outcomes. VEqO₂ may be able to detect differences in work during an SBT, but may not be able to predict change in workload in the respiratory system after extubation. The small sample size may also have prevented any differences in extubation outcomes to be shown.

Conclusion

VEqO₂ was higher in patients that passed their SBT. VEqO₂ was not useful in identifying extubation success or failure in adult mechanically ventilated patients.

The prognostic value of rapid shallow breathing index and physiologic dead space for weaning success in intensive care unit patients under mechanical ventilation

Background

Mechanical ventilation (MV) is a life-saving intervention that should be considered for patients with respiratory failure. This study was conducted to evaluate the predictive value of physiologic dead space for weaning success and compare it with rapid shallow breathing index (RSBI).

Materials and Methods

This cross-sectional study was conducted on 80 intensive care unit (ICU) patients who were under MV and candidate for weaning; among them, 68 patients experienced weaning success. RSBI was measured by dividing the respiratory rate by tidal volume. End-tidal CO₂ (PETCO₂) was obtained using caponometry, then dead-space was calculated as (VD/VT = (PaCO₂ - PETCO₂)/PaCO₂). PaCO₂ was also obtained from arterial blood gas recorded chart.

Results

Age, PaCO₂, PETCO₂, and RSBI were significantly different between those patients with and without weaning success (P < 0.05). RSBI ≤ 98 could predict the success of weaning with sensitivity 91.7%; specificity 76.5% and (AUC) area under the ROC curve (AUC = 0.87; 95% confidence interval [CI]: 0.78-0.94; P < 0.001). Dead space was not statistically significant prognostic index (AUC = 0.50; 95% CI: 0.31-0.69; P = 0.09).

Conclusion

In our study, RSBI was an effective predictive index for weaning success in ICU patients under MV, but dead space did not show significant predictive value. Further studies with larger sample sizes for providing more evidence are recommended.

Chest physiotherapy with early mobilization may improve extubation outcome in critically ill patients in the intensive care units

BACKGROUND

Extubation failure can lead to a longer intensive care unit (ICU) stay, higher mortality rate, and higher risk of requiring tracheostomy. Chest physiotherapy (CPT) can help patients in reducing the accumulation of airway secretion, preventing collapsed lung, improving lung compliance, and reducing comorbidities. Much research has investigated the correlation between CPT and respiratory system clearance. However, few studies have investigated the correlation between CPT and failed ventilator extubation. Therefore, this study aimed to investigate the use of CPT for reducing the rate of failed removal from mechanical ventilators.

METHODS

This study was an intervention study with mechanical control. Subjects were divided into two groups. The control group, which received routine nursing chest care, was selected from a retrospective chart review. The intervention group was prospectively taken into the chest physiotherapy program. The chest physiotherapy treatment protocol consisted of inspiratory muscle training, manual hyperinflation, chest wall mobilization, secretion removal, cough function training, and early mobilization.

RESULTS

A total of 439 subjects were enrolled in the intervention and control groups, with a mean age of 69 years. APACHE II score (P = .09) and GCS scores (P = .54) were similar between the two groups. Compared to the control group, patients in the intervention group had a significantly lower reintubation rate (8% vs 16%; P = .01).

CONCLUSIONS

The results indicate that intensive chest physiotherapy could decrease extubation failure in mechanically ventilated patients in the ICU. In addition, chest physiotherapy could also significantly improve the rapid shallow breathing index score.

Comparison of Lung Ultrasound-based Weaning Indices with Rapid Shallow Breathing Index: Are They Helpful?

Background and Aims:

The diaphragm is considered the main respiratory muscle and difficulty in weaning can occur because of impaired diaphragmatic function. Hence, monitoring diaphragmatic function is important. The aim of this study is to assess the ability of various lung ultrasound (US) indices and the rapid shallow breathing index (RSBI) to predict the outcome of the weaning process and compare them with RSBI.

Materials and Methods:

This was a prospective study conducted on patients admitted to critical care unit at a tertiary care hospital in north India from February 2017 to June 2017. Patients were put to spontaneous breathing trial (SBT) when they met the weaning criteria. Initial US was done immediately after putting the patient on SBT to check anatomy of the diaphragm and rule out patients according to exclusion criteria. This was followed by complete lung US (LUS) after 20 min of SBT.

Results:

The RSBI performed better than all other parameters, with an area under the curve (AUC) of 0.996. The sensitivity and specificity is 100%. Only comparable to RSBI is the speed of diaphragmic contraction (DC) which has AUC of 0.93. All other parameters had an AUC <0.8. Moreover, the DC and LUS score are strongly positively correlated with RSBI, whereas diaphragmic excursion and diaphragmic thickness fraction (DTF %) are weakly correlated.

Conclusion:

In Intensive Care Unit, RSBI is the best clinical tool for weaning, and DC is found to be the best parameter for weaning among the US-based weaning parameters. It can even be a substitute for RSBI, in today's world of real-time monitoring methods.

Rapid shallow breathing index

Predicting successful liberation of patients from mechanical ventilation has been a focus of interest to clinicians practicing in intensive care. Various weaning indices have been investigated to identify an optimal weaning window. Among them, the rapid shallow breathing index (RSBI) has gained wide use due to its simple technique and avoidance of calculation of complex pulmonary mechanics. Since its first description, several modifications have been suggested, such as the serial measurements and the rate of change of RSBI, to further improve its predictive value. The objective of this paper is to review the utility of RSBI in predicting weaning success. In addition, the use of RSBI in specific patient populations and the reported modifications of RSBI technique that attempt to improve the utility of RSBI are also reviewed.

Modified rapid shallow breathing index adjusted with anthropometric parameters increases predictive power for extubation failure compared with the unmodified index in postcardiac surgery patients

OBJECTIVE

The aim of this study was to determine the best predictors of successful extubation after cardiac surgery, by modifying the rapid shallow breathing index (RSBI) based on patients' anthropometric parameters.

DESIGN

Single-center prospective observational study.

SETTING

Two general intensive care units at a single research institute.

PARTICIPANTS

Patients who had undergone uncomplicated cardiac surgery.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The following parameters were investigated in conjunction with modification of the RSBI: Actual body weight (ABW), predicted body weight, ideal body weight, body mass index (BMI), and body surface area. Using the first set of patient data, RSBI threshold and modified RSBI for extubation failure were determined (threshold value; RSBI: 77 breaths/min (bpm)/L, RSBI adjusted with ABW: 5.0 bpm×kg/mL, RSBI adjusted with BMI: 2.0 bpm×BMI/mL). These threshold values for RSBI and RSBI adjusted with ABW or BMI were validated using the second set of patient data. Sensitivity values for RSBI, RSBI modified with ABW, and RSBI modified with BMI were 91%, 100%, and 100%, respectively. The corresponding specificity values were 89%, 92%, and 93%, and the corresponding receiver operator characteristic values were 0.951, 0.977, and 0.980, respectively.

CONCLUSIONS

Modified RSBI adjusted based on ABW or BMI has greater predictive power than conventional RSBI.

The effect of flow trigger on rapid shallow breathing index measured through the ventilator

BACKGROUND

The rapid shallow breathing index (RSBI) has the best predictive value to assess readiness for weaning from mechanical ventilation. At many institutions, this index is conveniently measured without disconnecting the patient from the ventilator, but this method may be inaccurate. Because modern ventilators have a base flow in the flow trigger mode that may provide a substantial help to the patient, we hypothesized that the RSBI is significantly decreased when measured through the ventilator with flow trigger even without continuous positive airway pressure (CPAP) and pressure support (PS).

METHODS

The RSBI was calculated using the values of minute ventilation and respiratory rate obtained either through the digital display of the ventilator or from a digital ventilometer. The RSBI was measured using 3 different methods: method 1, CPAP and PS both 0 cm H2O with flow trigger; method 2, CPAP and PS both 0 cm H2O without flow trigger; and method 3, using digital ventilometer.

RESULTS

A total of 165 measurements per method were obtained in 80 adult patients in the medical intensive care unit (MICU). The RSBI (breaths/min/L) values were 70.2 ± 26.5 with method 1, 85.4 ± 30.3 with method 2, and 80.1 ± 30.3 with method 3. The RSBI was significantly decreased using mechanical ventilation with flow trigger as compared with mechanical ventilation without flow trigger (P < .0001) or digital ventilometer (P < .0001). When method 1 was compared with methods 2 and 3, the RSBI decreased by 17% and 12%, respectively.

CONCLUSIONS

The RSBI measurement is significantly decreased by the base flow delivered through modern ventilators in the flow trigger mode. If RSBI is measured through the ventilator in the flow trigger mode, the difference should be considered when using RSBI to assess readiness for weaning from mechanical ventilation.

The use of extubation readiness parameters: a survey of pediatric critical care physicians

BACKGROUND

The pediatric literature addressing extubation readiness parameters and strategies to wean from mechanical ventilation is limited.

METHODS

We designed a survey to assess the use of extubation readiness parameters among pediatric critical care physicians at academic centers in the United States.

RESULTS

The overall response rate was 44.1% (417/945). The majority of respondents check for air leak and the amount of tracheal secretions. Fewer respondents use sedation score, the rapid shallow breathing index, or the airway-occlusion pressure 0.1 s after the start of inspiratory flow prior to extubation. The majority perform a spontaneous breathing trial with pressure support. The majority consider 30 cm H2O as the upper limit of an air leak test, and the need for endotracheal suctioning once every 2-4 hours as acceptable for extubation. In preparation for termination of mechanical ventilation the majority daily wean the ventilator rate and/or the pressure support instead of conducting a spontaneous breathing trial.

CONCLUSIONS

Most pediatric critical care physicians reported assessing extubation readiness by checking air leak and suctioning need, and less often consider or perform sedation score or the rapid shallow breathing index.

The weaning index as predictor of weaning success

BACKGROUND

The quest to obtain an accurate way to predict success when weaning a patient from mechanical ventilation continues. The established parameters such as tidal volume (Vt), respiratory rate (f), negative inspiratory force (NIF), vital capacity (VC), and minute ventilation (V) have not predicted weaning accurately. The frequency-to-tidal volume ratio (f/Vt), or rapid shallow breathing index (RSBI) is a good predictor of weaning success if the value is low, but not when the value approximates 105. Because of the aforementioned, we decided to add 2 corrective factors to the RSBI. The first one was elastance index (EI = peak pressure/NIF) and the second one, the ventilatory demand index (VDI = minute ventilation/10). The result of the product of the RSBI × EI × VDI was called the weaning index (WI).

METHODS

In order to assess the discriminatory power of WI, we obtained weaning parameters and calculated WI for 59 patients in our intensive care unit and extubated them if RSBI was ≤105. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and receiver-operating characteristics (ROC) curves were obtained. The results were compared with the previous studies involving the RSBI.

RESULTS

The WI sensitivity was 98%, specificity was 89%, PPV was 95%, NPV was 94%, and area under the ROC curve was 95.9.

CONCLUSIONS

The WI is a simple and reproducible parameter that integrates breathing pattern, compliance, inspiratory muscle strength, and ventilatory demand and is the most accurate predictor of weaning success.