Switches in non-invasive respiratory support strategies during acute hypoxemic respiratory failure: Need to monitoring from a retrospective observational study

OBJECTIVE

To explore combined non-invasive-respiratory-support (NIRS) patterns, reasons for NIRS switching, and their potential impact on clinical outcomes in acute-hypoxemic-respiratory-failure (AHRF) patients.

DESIGN

Retrospective, single-center observational study.

SETTING

Intensive Care Medicine.

PATIENTS

AHRF patients (cardiac origin and respiratory acidosis excluded) underwent combined NIRS therapies such as non-invasive-ventilation (NIV) and High-Flow-Nasal-Cannula (HFNC).

INTERVENTIONS

Patients were classified based on the first NIRS switch performed (HFNC-to-NIV or NIV-to-HFNC), and further specific NIRS switching strategies (NIV trial-like vs. Non-NIV trial-like and single vs. multiples switches) were independently evaluated.

MAIN VARIABLES OF INTEREST

Reasons for switching, NIRS failure and mortality rates.

RESULTS

A total of 63 patients with AHRF were included, receiving combined NIRS, 58.7% classified in the HFNC-to-NIV group and 41.3% in the NIV-to-HFNC group. Reason for switching from HFNC to NIV was AHRF worsening (100%), while from NIV to HFNC was respiratory improvement (76.9%). NIRS failure rates were higher in the HFNC-to-NIV than in NIV-to-HFNC group (81% vs. 35%, p < 0.001). Among HFNC-to-NIV patients, there was no difference in the failure rate between the NIV trial-like and non-NIV trial-like groups (86% vs. 78%, p = 0.575) but the mortality rate was significantly lower in NIV trial-like group (14% vs. 52%, p = 0.02). Among NIV to HFNC patients, NIV failure was lower in the single switch group compared to the multiple switches group (15% vs. 53%, p = 0.039), with a shorter length of stay (5 [2-8] vs. 12 [8-30] days, p = 0.001).

CONCLUSIONS

NIRS combination is used in real life and both switches' strategies, HFNC to NIV and NIV to HFNC, are common in AHRF management. Transitioning from HFNC to NIV is suggested as a therapeutic escalation and in this context performance of a NIV-trial could be beneficial. Conversely, switching from NIV to HFNC is suggested as a de-escalation strategy that is deemed safe if there is no NIRS failure.

Comparing lung aeration and respiratory effort using two different spontaneous breathing trial: T-piece vs pressure support ventilation

OBJECTIVE

To assess the changes in lung aeration and respiratory effort generated by two different spontaneous breathing trial (SBT): T-piece (T-T) vs pressure support ventilation (PSV).

DESIGN

Prospective, interventionist and randomized study.

SETTING

Intensive Care Unit (ICU) of Hospital del Mar.

PARTICIPANTS

Forty-three ventilated patients for at least 24 h and considered eligible for an SBT were included in the study between October 2017 and March 2020.

INTERVENTIONS

30-min SBT with T-piece (T-T group, 20 patients) or 8-cmH2O PSV and 5-cmH2O positive end expiratory pressure (PSV group, 23 patients).

MAIN VARIABLES OF INTEREST

Demographics, clinical data, physiological variables, lung aeration evaluated with electrical impedance tomography (EIT) and lung ultrasound (LUS), and respiratory effort using diaphragmatic ultrasonography (DU) were collected at different timepoints: basal (BSL), end of SBT (EoSBT) and one hour after extubation (OTE).

RESULTS

There were a loss of aeration measured with EIT and LUS in the different study timepoints, without statistical differences from BSL to OTE, between T-T and PSV [LUS: 3 (1, 5.5) AU vs 2 (1, 3) AU; p = 0.088; EELI: -2516.41 (-5871.88, 1090.46) AU vs -1992.4 (-3458.76, -5.07) AU; p = 0.918]. Percentage of variation between BSL and OTE, was greater when LUS was used compared to EIT (68.1% vs 4.9%, p ≤ 0.001). Diaphragmatic excursion trend to decrease coinciding with a loss of aeration during extubation.

CONCLUSION

T-T and PSV as different SBT strategies in ventilated patients do not show differences in aeration loss, nor estimated respiratory effort or tidal volume measured by EIT, LUS and DU.

Association between histological diaphragm atrophy and ultrasound diaphragm expiratory thickness in ventilated patients

Background

Diaphragm fiber atrophy has been evidenced after short periods of mechanical ventilation (MV) and related to critical illness-associated diaphragm weakness. Atrophy is described as a decrease in diaphragm fiber cross-sectional area (CSA) in human diaphragm biopsy, but human samples are still difficult to obtain in clinics. In recent years, ultrasound has become a useful tool in intensive care to evaluate diaphragm anatomy. The present study aimed to evaluate the ability of diaphragm expiratory thickness (Tdi) measured by ultrasound to predict diaphragm atrophy, defined by a decrease in diaphragm fiber CSA obtained through diaphragm biopsy (the gold standard technique) in ventilated patients.

Methods

Diaphragm biopsies and diaphragm ultrasound were performed in ventilated donors and in control subjects. Demographic variables, comorbidities, severity on admission, treatment, laboratory test results and evolution variables were evaluated. Immunohistochemical analysis to determine CSA and ultrasound measurements of Tdi at end-expiration were performed, and median values of the control group were used as thresholds to determine agreement between them in further analysis. Sensitivity, specificity, and positive and negative predictive values of an ultrasound Tdi cutoff for detecting histologic atrophy were calculated. Agreement between two ultrasound observers was also assessed.

Results

Thirty-five ventilated organ donors and 5 ventilated controls were included, without differences in basic characteristics. CSA and Tdi were lower in donors than in controls. All donors presented lower CSA, but only 74% lower Tdi regarding control group thresholds. The cut-off value for lower diaphragm expiratory thickness (Tdi < 1.7 mm) presented a sensitivity of 73%, a specificity of 67%, a positive predictive value of 96% and a negative predictive value of 17% for determining the presence of diaphragm atrophy (CSA < 2851 μm²).

Conclusions

Diaphragm atrophy and thickness reduction is associated to MV. While a lower Tdi in diaphragm ultrasound is a good tool for diagnosing atrophy, normal or increased Tdi cannot rule atrophy out showing that both parameters should not be considered as synonymous.

Aeration changes induced by high flow nasal cannula are more homogeneous than those generated by non-invasive ventilation in healthy subjects

BACKGROUND

Non-invasive mechanical ventilation (NIV) is a standard respiratory support technique used in intensive care units. High-Flow Nasal Cannula (HFNC) has emerged as an alternative, but further evidence is needed. The lung aeration and diaphragm changes achieved with these two strategies in healthy subjects have not been compared to date.

METHODS

Twenty healthy subjects were recruited. Ten were ventilated with NIV and ten underwent HFNC. Lung impedance and diaphragmatic ultrasound measurements were performed before and after 30 min of respiratory support. The Mar-index was defined as the ratio of the diaphragm excursion-time index to the respiratory rate.

RESULTS

Both groups showed significant decreases in respiratory rate (NIV: 14.4 (4.1) vs 10.4 (1.6), p = 0.009; HFNC: 13.6 (4.3) vs 7.9 (1.5) bpm, p = 0.002) and significant increases in the end-expiratory lung impedance (EELI) (NIV: 66,348(10,761) vs. 73,697 (6858), p = 0.005; HFNC: 66,252 (9793) vs 69,869 (9135), p = 0.012). NIV subjects showed a significant increase in non-dependent silent spaces (4.13 (2.25) vs 5.81 (1.49)%, p = 0.037) while the increase was more homogeneous with HFNC. The variation in EELI tended to be higher in NIV than in HFNC (8137.08 (6152.04) vs 3616.94 (3623.03), p = 0.077). The Mar-index was higher in HFNC group (13.15 vs 5.27 cm-sec²/bpm, p = 0.02).

CONCLUSIONS

NIV and HFNC increased EELI in healthy subjects, suggesting an increase in the functional residual capacity. The EELI increase may be higher in NIV, but HFNC produced a more homogeneous change in lung ventilation. HFNC group has a higher MAR-index that could reflect a different ventilatory system adaptation.

Severe vitamin D deficiency upon admission in critically ill patients is related to acute kidney injury and a poor prognosis

OBJECTIVES

To evaluate the prevalence of vitamin D deficiency in critically ill patients upon admission to an Intensive Care Unit (ICU) and its prognostic implications.

DESIGN

A single-center, prospective observational study was carried out from January to November 2015. Patients were followed-up on until death or hospital discharge.

SETTING

The department of Critical Care Medicine of a university hospital.

PATIENTS

All adults admitted to the ICU during the study period, without known factors capable of altering serum 25(OH)D concentration.

INTERVENTIONS

Determination of serum 25(OH)D levels within the first 24h following admission to the ICU.

MAIN VARIABLES OF INTEREST

Prevalence and mortality at 28 days.

RESULTS

The study included 135 patients, of which 74% presented deficient serum 25(OH)D levels upon admission to the ICU. Non-survivors showed significantly lower levels than survivors (8.14ng/ml [6.17-11.53] vs. 12ng/ml [7.1-20.30]; P=.04], and the serum 25(OH)D levels were independently associated to mortality (OR 2.86; 95% CI 1.05-7.86; P=.04]. The area under the ROC curve was 0.61 (95% CI 0.51-0.75), and the best cut-off point for predicting mortality was 10.9ng/ml. Patients with serum 25(OH)D<10.9ng/ml also showed higher acute kidney injury rates (13 vs. 29%; P=.02).

CONCLUSION

Vitamin D deficiency is highly prevalent upon admission to the ICU. Severe Vitamin D deficiency (25[OH]D<10.9ng/ml) upon admission to the ICU is associated to acute kidney injury and mortality.

Prospective validation of right ventricular role in primary graft dysfunction after lung transplantation

Primary graft dysfunction is a significant cause of lung transplant morbidity and mortality, but its underlying mechanisms are not completely understood. The aims of the present study were: 1) to confirm that right ventricular function is a risk factor for severe primary graft dysfunction; and 2) to propose a clinical model for predicting the development of severe primary graft dysfunction.A prospective cohort study was performed over 14 months. The primary outcome was development of primary graft dysfunction grade 3. An echocardiogram was performed immediately before transplantation, measuring conventional and speckle-tracking parameters. Pulmonary artery catheter data were also measured. A classification and regression tree was made to identify prognostic models for the development of severe graft dysfunction.70 lung transplant recipients were included. Patients who developed severe primary graft dysfunction had better right ventricular function, as estimated by cardiac index (3.5±0.8 versus 2.6±0.7 L·min^-1·m^-2, p<0.01) and basal longitudinal strain (-25.7±7.3% versus -19.5±6.6%, p<0.01). Regression tree analysis provided an algorithm based on the combined use of three variables (basal longitudinal strain, pulmonary fibrosis disease and ischaemia time), allowing accurate preoperative discrimination of three distinct subgroups with low (11-20%), intermediate (54%) and high (75%) risk of severe primary graft dysfunction (area under the receiver operating characteristic curve 0.81).Better right ventricular function is a risk factor for the development of severe primary graft dysfunction. Preoperative estimation of right ventricular function could allow early identification of recipients at increased risk, who would benefit the most from careful perioperative management in order to limit pulmonary overflow.

The role of high flow oxygen therapy in acute respiratory failure

Acute respiratory failure represents one of the most common causes of intensive care unit admission and oxygen therapy remains the first-line therapy in the management of these patients. In recent years, high-flow oxygen via nasal cannula has been described as a useful alternative to conventional oxygen therapy in patients with acute respiratory failure. High-flow oxygen via nasal cannula rapidly alleviates symptoms of acute respiratory failure and improves oxygenation by several mechanisms, including dead space washout, reduction in oxygen dilution and inspiratory nasopharyngeal resistance, a moderate positive airway pressure effect that may generate alveolar recruitment and an overall greater tolerance and comfort with the interface and the heated and humidified inspired gases. However, the experience in adults is still limited and there are no clinical guidelines to establish recommendations for their use. This article aims to review the existing evidence on the use of high-flow oxygen via nasal cannula in adults with acute respiratory failure and its possible applications, advantages and limitations.

Influence of right ventricular function on the development of primary graft dysfunction after lung transplantation

BACKGROUND

Primary graft dysfunction (PGD) remains a significant cause of lung transplant postoperative morbidity and mortality. The underlying mechanisms of PGD development are not completely understood. This study analyzed the effect of right ventricular function (RVF) on PGD development.

METHODS

A retrospective analysis of a prospectively assessed cohort was performed at a single institution between July 2010 and June 2013. The primary outcome was development of PGD grade 3 (PGD3). Conventional echocardiographic parameters and speckle-tracking echocardiography, performed during the pre-transplant evaluation phase up to 1 year before surgery, were used to assess preoperative RVF.

RESULTS

Included were 120 lung transplant recipients (LTr). Systolic pulmonary arterial pressure (48 ± 20 vs 41 ± 18 mm Hg; p = 0.048) and ischemia time (349 ± 73 vs 306 ± 92 minutes; p < 0.01) were higher in LTr who developed PGD3. Patients who developed PGD3 had better RVF estimated by basal free wall longitudinal strain (BLS; -24% ± 9% vs -20% ± 6%; p = 0.039) but had a longer intensive care unit length of stay and mechanical ventilation and higher 6-month mortality. BLS ≥ -21.5% was the cutoff that best identified patients developing PGD3 (area under the receiver operating characteristic curve, 0.70; 95% confidence interval, 0.54-0.85; p = 0.020). In the multivariate analysis, a BLS ≥ -21.5% was an independent risk factor for PGD3 development (odds ratio, 4.56; 95% confidence interval, 1.20-17.38; p = 0.026), even after adjusting for potential confounding.

CONCLUSIONS

A better RVF, as measured by BLS, is a risk factor for severe PGD. Careful preoperative RVF assessment using speckle-tracking echocardiography may identify LTrs with the highest risk of developing PGD.