Development of clinical tools to estimate the breathing effort during high-flow oxygen therapy: A multicenter cohort study.

INTRODUCTION AND OBJECTIVES: Quantifying breathing effort in non-intubated patients is important but difficult. We aimed to develop two models to estimate it in patients treated with high-flow oxygen therapy. PATIENTS AND METHODS: We analyzed the data of 260 patients from previous studies who received high-flow oxygen therapy. Their breathing effort was measured as the maximal deflection of esophageal pressure (ΔPes). We developed a multivariable linear regression model to estimate ΔPes (in cmH2O) and a multivariable logistic regression model to predict the risk of ΔPes being >10 cmH2O. Candidate predictors included age, sex, diagnosis of the coronavirus disease 2019 (COVID-19), respiratory rate, heart rate, mean arterial pressure, the results of arterial blood gas analysis, including base excess concentration (BEa) and the ratio of arterial tension to the inspiratory fraction of oxygen (PaO2:FiO2), and the product term between COVID-19 and PaO2:FiO2. RESULTS: We found that ΔPes can be estimated from the presence or absence of COVID-19, BEa, respiratory rate, PaO2:FiO2, and the product term between COVID-19 and PaO2:FiO2. The adjusted R2 was 0.39. The risk of ΔPes being >10 cmH2O can be predicted from BEa, respiratory rate, and PaO2:FiO2. The area under the receiver operating characteristic curve was 0.79 (0.73-0.85). We called these two models BREF, where BREF stands for BReathing EFfort and the three common predictors: BEa (B), respiratory rate (RE), and PaO2:FiO2 (F). CONCLUSIONS: We developed two models to estimate the breathing effort of patients on high-flow oxygen therapy. Our initial findings are promising and suggest that these models merit further evaluation.

High flow nasal cannula compared with conventional oxygen therapy for acute hypoxemic respiratory failure: a systematic review and meta-analysis.

BACKGROUND: This systematic review and meta-analysis summarizes the safety and efficacy of high flow nasal cannula (HFNC) in patients with acute hypoxemic respiratory failure. METHODS: We performed a comprehensive search of MEDLINE, EMBASE, and Web of Science. We identified randomized controlled trials that compared HFNC to conventional oxygen therapy. We pooled data and report summary estimates of effect using relative risk for dichotomous outcomes and mean difference or standardized mean difference for continuous outcomes, with 95% confidence intervals. We assessed risk of bias of included studies using the Cochrane tool and certainty in pooled effect estimates using GRADE methods. RESULTS: We included 9 RCTs (n = 2093 patients). We found no difference in mortality in patients treated with HFNC (relative risk [RR] 0.94, 95% confidence interval [CI] 0.67-1.31, moderate certainty) compared to conventional oxygen therapy. We found a decreased risk of requiring intubation (RR 0.85, 95% CI 0.74-0.99) or escalation of oxygen therapy (defined as crossover to HFNC in the control group, or initiation of non-invasive ventilation or invasive mechanical ventilation in either group) favouring HFNC-treated patients (RR 0.71, 95% CI 0.51-0.98), although certainty in both outcomes was low due to imprecision and issues related to risk of bias. HFNC had no effect on intensive care unit length of stay (mean difference [MD] 1.38 days more, 95% CI 0.90 days fewer to 3.66 days more, low certainty), hospital length of stay (MD 0.85 days fewer, 95% CI 2.07 days fewer to 0.37 days more, moderate certainty), patient reported comfort (SMD 0.12 lower, 95% CI 0.61 lower to 0.37 higher, very low certainty) or patient reported dyspnea (standardized mean difference [SMD] 0.16 lower, 95% CI 1.10 lower to 1.42 higher, low certainty). Complications of treatment were variably reported amongst included studies, but little harm was associated with HFNC use. CONCLUSION: In patients with acute hypoxemic respiratory failure, HFNC may decrease the need for tracheal intubation without impacting mortality.

A novel risk score for severe ARDS patients undergoing ECMO after retrieval from peripheral hospitals.

BACKGROUND: Extracorporeal Membrane Oxygenation in severe ARDS unresponsive to conventional protective ventilation is associated with elevated costs, resource and complications, and appropriate risk stratification of candidate patients could be useful to recognize those more likely to benefit from ECMO. We aimed to derive a new outcome prediction score for patients retrieved by our ECMO team from peripheral centers, including systematic echocardiographic evaluation before ECMO start. METHODS: Sixty-nine consecutive patients with refractory ARDS requiring ECMO transferred from peripheral centers to our ICU (a tertiary ECMO referral center), from 1 October 2009 to 31 December 2015, were assessed. RESULTS: All patients were transported on ECMO (distance, median 77, range 4-456 km) The mortality rate was 41% (28/69). Our new risk score included age ≥ 42 years, BMI < 31 kg/m2 , RV dilatation, and pH < 7.35. The proposed cut off (Youden's index method) of nine had a sensitivity of 96% and a specificity of 30% (AUC-ROC: 0.85, 95% CI: 0.76-0.94, P < 0.001). When assessing the discriminatory ability of our risk score in the population of local patients, survivors had a mean value of 15.4 ± 8.6, whereas non-survivors showed a mean value of 20.1 ± 7.4 (P < 0.001). CONCLUSIONS: Our new risk score shows good discriminatory ability both in patients retrieved from peripheral centers and in those implanted at our center. This score includes variables easily available at bedside, and, for the first time, a pathophysiologic element, RV dilatation.

Ventilation during extracorporeal support : Why and how.

The main target of extracorporeal support is to achieve viable gas exchange, while minimizing the risk of ventilator-induced lung injury, achieved through a decreased mechanical ventilation load on the natural lung. However, during veno-venous extracorporeal membrane oxygenation (ECMO), mechanical ventilation is still necessary in order to prevent lung collapse and/or if extracorporeal blood flow is not sufficient to guarantee adequate gas exchange. In this review, we will summarize the physiology of extracorporeal support and the rationale for continuing mechanical ventilation in this context. Furthermore, we will review the current clinical practice among ECMO centers and their suggestions regarding mechanical ventilator settings. While optimal ventilatory settings are still a matter of debate, the use of a strategy combining low tidal volume and limited inspiratory pressures is accepted worldwide. On the contrary, the choice of applied positive end-expiratory pressure (PEEP) varies between the total rest strategy and open lung strategy. Finally, the use of assisted or spontaneous ventilation will be discussed.

A spiky pattern in the course of electrical thoracic impedance as a very early sign of a developing pneumothorax.

A pneumothorax (PTX) is a potentially lethal condition in high-risk intensive care patients. Electrical impedance tomography (EIT) has been proven to detect PTX at the bedside. A so far not described pattern in the course of thoracic impedance at an early state of PTX was observed in a pig model of ventilator-induced lung injury (VILI) used for a more extensive study. EIT was performed at a framerate of 50 Hz. Beginning of PTX at normal ventilation, manifestation of PTX at VILI ventilation (plateau pressure 42 cm H2 O) and final pleural drainage were documented. At ventilation with 8·6 ml kg-1 , early PTX findings prior to any clinical deterioration consisted in a spike-like pattern in the time course of impedance (relative impedance change referred to initial end-expiratory level). Spike amplitudes (mean ± SD) were the following: 0·154 ± 0·059 (right lung) and 0·048 ± 0·050 (left lung). At this state, end-expiratory levels (mean ± SD) were still similar, -0·035 ± 0·010 (right) and -0·058 ± 0·022 (left). After application of VILI ventilation (38 ml kg-1 ), a PTX developed slowly, being confirmed by a continuous increase in the end-expiratory level on the right side and diverging levels of +0·320 ± 0·057 (right) and -0·193 ± 0·147 (left) at full manifestation. We assume that spikes reflect a temporary change in the electrical pathway caused by leakage into the pleural cavity. This newly described phenomenon of spikes is considered to be a potentially useful indicator for a very early detection of an evolving PTX in high-risk ICU patients.

Effect of positive end-expiratory pressure on pulmonary shunt and dynamic compliance during abdominal surgery.

BACKGROUND: General anaesthesia decreases pulmonary compliance and increases pulmonary shunt due to the development of atelectasis. The presence of capnoperitoneum during laparoscopic surgery may further decrease functional residual capacity, promoting an increased amount of atelectasis compared with laparotomy. The aim of this study was to evaluate the effects of different levels of positive end-expiratory pressure (PEEP) in both types of surgery and to investigate whether higher levels of PEEP should be used during laparoscopic surgery. METHODS: This prospective observational study included 52 patients undergoing either laparotomy or laparoscopic surgery. Three levels of PEEP were applied in random order: (1) zero (ZEEP), (2) 5 cmH2O and (3) 10 cmH2O. Pulmonary shunt and ventilation/perfusion mismatch were assessed by the automatic lung parameter estimator system. RESULTS: Pulmonary shunt was similar in both groups. However, in laparotomy, a PEEP of 5 cmH2O significantly decreased shunt when compared with ZEEP (12 vs 6%; P=0.001), with additional PEEP having no further effect. In laparoscopic surgery, a significant reduction in shunt (13 vs 6%; P=0.001) was obtained only at a PEEP of 10 cmH2O. Although laparoscopic surgery was associated with a lower pulmonary compliance, increasing levels of PEEP were able to ameliorate it in both groups. CONCLUSION: Both surgeries have similar negative effects on pulmonary shunt, while the presence of capnoperitoneum reduced only the pulmonary compliance. It appears that a more aggressive PEEP level is required to reduce shunt and to maximize compliance in case of laparoscopic surgery.

Long-term extracorporeal membrane oxygenation with minimal ventilatory support: a new paradigm for severe ARDS?

Pulmonary tuberculosis can lead to acute respiratory distress syndrome (ARDS) which is associated with high mortality. We report the case of a patient with pulmonary tuberculosis and severe ARDS (PaO2/FiO2<100 mmHg) who was initially managed with advanced up-to-date treatments (protective ventilation and extracorporeal membrane oxygenation, ECMO) but failed to improve. After a month of failure and the development of bilateral pneumothoraces, we drastically changed our therapeutic strategy: we maximized ECMO support to maintain oxygenation, we greatly reduced ventilation pressures and we left the pneumothoraces undrained. From then on, the patient improved and he eventually survived. This case suggests that ECMO permits large reductions in lung inflation and ventilation to rest the lungs, while maintaining acceptable oxygenation. The combination of ECMO and markedly attenuated ventilation strategy may be effective in cases of severe ARDS.

Prolonged mechanical ventilation after critical illness.

A significant number of patients that have been critically ill require mechanical ventilation for extended periods of time as they progress towards recovery. Many of these patients can be cared for outside of the Intensive Care Unit in facilities focused on stabilizing the underlying medical problems, managing ventilatory support, and planning for rehabilitation and home care. Although these units have varied administrative structures, they have reported similar encouraging rates of weaning and survival. In a recent study about such a ward at a large academic hospital, it was observed that, although the majority of patients were liberated from the ventilator and returned home with a satisfactory activity level, a significant number of patients did not; these patients eventually died after a protracted hospital stay, mostly after a consensual withdrawal of life support. In the present article, a relevant literature review is presented concerning the outcome of patients undergoing prolonged mechanical ventilation. The main focus of the research was to address how to alleviate the burden of prolonged critical illness on mechanically ventilated patients who may eventually die after a great deal of suffering, and to identify the tangible emotional and financial costs to these patients, their families, and society.

The lumbar lordosis below Harrington instrumentation for scoliosis.

This retrospective study evaluates lumbar lordosis in 43 patients before and after Harrington instrumentation into the lumbar spine. The authors measured overall lumbar lordosis, lordosis of unfused lumbar levels, and sagittal vertical axis. Lordosis decreased progressively in lower levels of fusion. The increase in lordosis below the fusion did not compensate for the overall loss of lordosis. The sagittal vertical axis moved forward, producing a subtle, asymptomatic form of flat back syndrome.

Treatment of fractures of the vertebral limbus and spinal stenosis in five adolescents and five adults.

Fractures of the vertebral limbus occur between the vertebral ring apophyses and the cartilaginous rim of the superior or inferior margins of the vertebral end plates. These fractures are typically seen in adolescents or young adults, since fusion in this area is not complete until the ages of 18 to 25. Of 85 cases reported, 24 occurred in adolescents. The authors present the clinical, neurodiagnostic, and surgical management of fractures of the vertebral limbus and coincident segmental spinal stenosis in a group of 5 adolescents and 5 adults. An additional category for fractures of the vertebral limbus is proposed, namely, a lesion that is not confined to the superior or inferior margins of the vertebral end plates, but that spans the full length of the vertebral body.