The goal of this paper is to review the use of CT scan in acute respiratory failure (ARF), acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). The most important papers studying CT in ARF, published in English language literature, were found in Medline. The use of CT in patients with ARF let allowed the authors to proceed to a qualitative evaluation of lung morphology looking for diffuse an/or localized hyperdensities, and for other concomitant abnormalities (pleural effusion, pneumothorax). It is also possible to evaluate lung density histograms and calculate the gas-tissue ratio within the lungs. Likewise, one can also calculate total and regional lung volumes (aerated, poorly-aerated, non-aerated, and overdistension volumes). Knowing those volumes it is possible to quantify alveolar recruitment and overdistension due to ventilatory strategies as the use of different positive end expiratory pressure (PEEP) levels.

Keywords: Acute lung injury. Acute respiratory distress syndrome.

Recent studies suggest that non-invasive positive pressure ventilation (NPPV) improves clinical signs and gas exchange, apart from avoiding the need for endotracheal intubation in selected patients with acute respiratory failure. In this prospective, open trial in the Intensive Care Unit (Hospital Universitário da Universidade Federal de Juiz de Fora), the authors evaluated the efficacy and security of using NPPV in patients with acute respiratory failure. Twenty-five patients with clinical or gasometric diagnosis of acute respiratory failure (respiratory rate > 25 breaths/min, accessory muscle use, PaO2 < 60 mmHg, PaCO2 > 50 mmHg after supplemental oxygen) received NPPV. Fifteen patients (60%) were successfully ventilated with NPPV, avoiding the tracheal intubation. After two hours with NPPV, the respiratory rate was reduced (from 36 ± 2 breaths/min to 26 ± 1 breaths/min, p < 0.01) and the PaO2 increased (from 76 ± 6 mmHg to 100 ± 12 mmHg, p < 0.05). Among the patients with hypercapnia, after two hours, the PaCO2 decreased (from 60 ± 2 mmHg to 49 ± 3 mmHg, p < 0.05). Four patients (16%) presented complications with facial skin necrosis, but only one had the NPPV stopped. Among the patients who did not respond to the method, three did not adapt to the NPPV and seven had it interrupted because of clinical deterioration. The authors conclude that NPPV is a safe option that can be used to treat selected patients with acute respiratory failure.

The goal of this paper is to review the use of pressure-volume (P-V) curves or compliance curves in patients with acute respiratory failure (ARF) - acute lung injury (ALI), and acute respiratory distress syndrome (ARDS). The most important papers published in English language literature concerning P-V curves in ARF were found in Medline and reviewed. Ideally, recommendation is made to calculate P-V curves in all patients with ARF in order to achieve adequate monitoring and management considering data obtained from the curves, such as lower inflexion point, upper inflexion point, and static compliance. The methods used to obtain P-V curves are supersyringe, multiple inspiratory occlusions and continuous flow. All of them are similar if low continuous flow is used and if care is taken to allow lung emptying and to avoid intrinsic PEEP (positive end expiratory pressure) before accomplishing the curves. In this way continuous flow can be a simple, inexpensive, secure and reliable method to be carried out at bedside in order to obtain P-V curves that allow for a better monitoring and management of patients with ARF.

Keywords: Acute lung injury. Acute respiratory distress syndrome. Pressure-volume curves.

Objective: To evaluate the effects of non-invasive positive pressure ventilation (NIPPV) on acute respiratory failure and to identify the factors associated with its failure or success. Patients and methods: This open and prospective study analyzed 60 episodes of NIPPV use in 53 patients with respiratory failure. Results: In 37 occasions (62%), the patients were successfully ventilated with NIPPV (Success Group, SG) whereas in 23 episodes (38%) intubation was necessary (Failure Group, FG). FG patients showed a higher Apache II score (30.4 ± 9 versus 22.2 ± 8, p = 0.001). The use of NIPPV reduced respiratory rate after 2 hs. This reduction was less evident in FG (from 33 ± 9 to 30 ± 8 bpm, p = 0.094) than in SG (from 39 ± 11 to 28 ± 9 bpm, p < 0.001). PaO2 increased from 62 ± 22 to 101 ± 65 mmHg, (p < 0.001) with no differences between groups. Among patients with hypercapnia, PaCO2 level decreased in SG (from 76 ± 20 to 68 ± 21mmHg, p = 0.032) but not in FG (from 89 ± 23 to 93 ± 40mmHg, p = 0.54). Arterial pH increased in SG (from 7.25 ± 0.10 to 7.34 ± 0.11, p = 0.007) and not in FG (from 7.24 ± 0.07 to 7.21 ± 0.12, p = 0.48). NIPPV was used for longer in SG (3.4 ± 2.5 versus 2.3 ± 2 days, p = 0.003). Higher IPAP levels were used in SG (13.2 ± 3 versus 11 ± 4cmH2O, p = 0.02). The 10 patients (17%) who died, all belonged to FG. Skin lesions at the site of mask contact was the most common complication of NIPPV (5, 8%). NIPPV was efficient in treating acute respiratory failure in 2/3 of patients. The factors associated with failure were: greater severity of the illness, smaller reduction in the respiratory rate, no improvement of respiratory acidosis in 2 h and use of lower IPAP levels. The high mortality rate observed in FG (10, 43%) justifies efforts to optimize NIPPV implementation and to recognize its failure, as early as possible, in order to avoid delays in endotracheal intubation.

Keywords: Non-invasive positive pressure ventilation. Respiratory failure. Apache II. Hypercapnia.

Objective: To present the pulmonary histopathological alterations found in the autopsies of patients with acute respiratory failure (ARF) and determine whether underlying diseases and certain associated risk factors increase the incidence of these histopathological patterns. Methods: Final autopsy reports were reviewed, and 3030 autopsies of patients > 1 year of age with an underlying disease and associated risk factors were selected. All had developed diffuse infiltrates and died of ARF-related pulmonary alterations. Results: The principal pulmonary histopathological alterations resulting in immediate death were diffuse alveolar damage (DAD), pulmonary edema, lymphocytic interstitial pneumonia (LIP) and alveolar hemorrhage. The principal underlying diseases were AIDS, bronchopneumonia, sepsis, liver cirrhosis, pulmonary thromboembolism, acute myocardial infarction (AMI), cerebrovascular accident, tuberculosis, cancer, chronic kidney failure and leukemia. The principal associated risk factors were as follows: age ≥ 50 years; arterial hypertension; congestive heart failure; chronic obstructive pulmonary disease; and diabetes mellitus. These risk factors and AIDS correlated with a high risk of developing LIP; these same risk factors, if concomitant with sepsis or liver cirrhosis, correlated with a risk of developing DAD; thromboembolism and these risk factors correlated with a risk of developing alveolar hemorrhage; these risk factors and AMI correlated with a risk of developing pulmonary edema. Conclusion: Pulmonary findings in patients who died of ARF presented four histopathological patterns: DAD, pulmonary edema, LIP and alveolar hemorrhage. Underlying diseases and certain associated risk factors correlated positively with specific histopathological findings on autopsy.

Keywords: Respiratory insufficiency; Autopsy; Lung diseases, interstitial; Pulmonary edema; Hemorrhage.

Herein, we report an instance of occupational exposure to food preservatives and resultant acute respiratory failure in three workers. The toxicological analysis revealed that mixing the particular food preservatives involved, a procedure that was performed by the three workers involved, produced NO2, the inhalation of which caused the pulmonary edema and respiratory failure. With time, the pulmonary damage was completely reversed in all three individuals. Accompanying this case report is a brief review of the literature regarding acute pulmonary injury resulting from occupational exposure to chemicals. We emphasize the importance of training, as well as of the use of protective gear, for workers who handle chemical substances.

Keywords: Respiratory insufficiency; Occupational exposure; Occupational diseases; Case report

Objective: To determine the impact that open lung biopsy findings have on decisions regarding changes in the treatment strategies employed for critically ill patients presenting diffuse pulmonary infiltrates and suffering from refractory acute respiratory failure, as well as on their clinical improvement. Methods: This study involved 12 mechanically ventilated patients with acute respiratory failure who were subjected to open lung biopsy (by thoracotomy) after not presenting a clinical response to standard treatment. Results: The single most common cause of the acute respiratory failure was viral infection, which was identified in 5 patients (40%). The pre-operative evaluation of the cause of respiratory failure was modified in 11 patients (91.6%), and a specific diagnosis was made in 100% of the cases. Regardless of changes in treatment regimen, the mortality rate was 50%. Six patients (50%) survived to be discharged from the hospital. All of the discharged patients survived for at least one year after the open lung biopsy, for an overall one-year survival rate of 50% among the 12 patients studied. For the patients who died in the hospital, the time of survival after open lung biopsy was 14 + 10.8 days. Conclusion: We conclude that open lung biopsy is a useful tool in the management of acute respiratory failure when there is no clinical improvement after standard treatment, since it can lead to a specific diagnosis that requires distinct treatment, which probably lowers the mortality rate among such patients.

Keywords: Respiratory distress syndrome, adult; Lung/pathology; Biposy; Acute respiratory syndrome

Objective: Bedside lung ultrasound (LUS) is a noninvasive, readily available imaging modality that can complement clinical evaluation. The Bedside Lung Ultrasound in Emergency (BLUE) protocol has demonstrated a high diagnostic accuracy in patients with acute respiratory failure (ARF). Recently, bedside LUS has been added to the medical training program of our ICU. The aim of this study was to investigate the accuracy of LUS based on the BLUE protocol, when performed by physicians who are not ultrasound experts, to guide the diagnosis of ARF. Methods: Over a one-year period, all spontaneously breathing adult patients consecutively admitted to the ICU for ARF were prospectively included. After training, 4 non-ultrasound experts performed LUS within 20 minutes of patient admission. They were blinded to patient medical history. LUS diagnosis was compared with the final clinical diagnosis made by the ICU team before patients were discharged from the ICU (gold standard). Results: Thirty-seven patients were included in the analysis (mean age, 73.2  14.7 years; APACHE II, 19.2  7.3). LUS diagnosis had a good agreement with the final diagnosis in 84% of patients (overall kappa, 0.81). The most common etiologies for ARF were pneumonia (n = 17) and hemodynamic lung edema (n = 15). The sensitivity and specificity of LUS as measured against the final diagnosis were, respectively, 88% and 90% for pneumonia and 86% and 87% for hemodynamic lung edema. Conclusions: LUS based on the BLUE protocol was reproducible by physicians who are not ultrasound experts and accurate for the diagnosis of pneumonia and hemodynamic lung edema.

Keywords: Ultrasonography, interventional; Respiratory insufficiency; Intensive care units.

Eosinophilia-myalgia syndrome was described in 1989 in patients who presented progressive and incapacitating myalgia and eosinophilia in blood, fluids and secretions. Most patients report previous L-tryptophan intake. Respiratory manifestations are found in up to 80% of the cases, occasionally as the only manifestation. Treatment includes drug discontinuation and administration of corticosteroids. Here, we describe the case of a 61-year-old female admitted with acute respiratory failure after using L-tryptophan, hydroxytryptophan and other drugs. The patient presented eosinophilia, together with elevated eosinophil counts in the bronchoalveolar lavage and pleural effusion. After discontinuation of the drugs previously used, corticosteroids were administered, resulting in clinical and radiological improvement within just a few days.

Keywords: Respiratory insufficiency; Tryptophan; Eosinophilia-myalgia syndrome.

Objective: To assess the feasibility of using a new helmet interface for CPAP, designated ELMO, to treat COVID-19-related acute hypoxemic respiratory failure (AHRF) outside the ICU. Methods: This was a proof-of-concept study involving patients with moderate to severe AHRF secondary to COVID-19 admitted to the general ward of a public hospital. The intervention consisted of applying CPAP via the ELMO interface integrated with oxygen and compressed air flow meters (30 L/min each) and a PEEP valve (CPAP levels = 8-10 cmH2O), forming the ELMOcpap system. The patients were monitored for cardiorespiratory parameters, adverse events, and comfort. Results: Ten patients completed the study protocol. The ELMOcpap system was well tolerated, with no relevant adverse effects. Its use was feasible outside the ICU for a prolonged amount of time and was shown to be successful in 60% of the patients. A CPAP of 10 cmH2O with a total gas flow of 56-60 L/min improved oxygenation after 30-to 60-min ELMOcpap sessions, allowing a significant decrease in estimated FIO2 (p = 0.014) and an increase in estimated PaO2/FIO2 ratio (p = 0.008) within the first hour without CO2 rebreathing. Conclusions: The use of ELMOcpap has proven to be feasible and effective in delivering high-flow CPAP to patients with COVID-19-related AHRF outside the ICU. There were no major adverse effects, and ELMO was considered comfortable. ELMOcpap sessions significantly improved oxygenation, reducing FIO2 without CO2 rebreathing. The overall success rate was 60% in this pilot study, and further clinical trials should be carried out in the future. (ClinicalTrials.gov identifier: NCT04470258 [http://www.clinicaltrials.gov/])

Keywords: Pneumonia; SARS-CoV-2; COVID-19; Respiratory protective devices; Continuous positive airway pressure; Noninvasive ventilation.

Background: The aim of this study was to describe the signs of active tuberculosis in patients submitted to high resolution computerized tomography and the distribution of lesions along the pulmonary parenchyma. Material and methods: The high resolution CTs performed on 42 patients with tuberculosis either bacteriologically diagnosed or clinical suspected and later confirmed by bacteriological tests were studied. Results: The signs of disease activity observed were airspace nodule (83%), centrilobular nodule (74%), tree-in-bud pattern (67%), cavitations (67%), bronchial thickening (55%), parenchymal consolidations (48%), ground glass opacity (21%) and thickening of the inter and intralobular septa (9%). Conclusion: High resolution computed tomography can be strongly suggestive of disease activity, is particularly helpful in patients with negative smear and/or undetermined radiographs, and allows the establishment of proper treatment, even before mycobacteria are identified in means of culture.

Keywords: Pulmonary tuberculosis. X-ray computed tomography.

Neuromuscular diseases affect alveolar air exchange and therefore cause chronic respiratory failure. The onset of respiratory failure can be acute, as in traumas, or progressive (slow or rapid), as in amyotrophic lateral sclerosis, muscular dystrophies, diseases of the myoneural junction, etc. Respiratory muscle impairment also affects cough efficiency and, according to the current knowledge regarding the type of treatment available in Brazil to these patients, it can be said that the high rates of morbidity and mortality in these individuals are more often related to the fact that they cough inefficiently rather than to the fact that they ventilate poorly. In this review, with the objective of presenting the options of devices available to support and substitute for natural ventilation in patients with neuromuscular diseases, we have compiled a brief history of the evolution of orthopedic braces and prostheses used to aid respiration since the end of the 19th century. In addition, we highlight the elements that are fundamental to the diagnosis of alveolar hypoventilation and of failure of the protective cough mechanism: taking of a clinical history; determination of peak cough flow; measurement of maximal inspiratory and expiratory pressures; spirometry in two positions (sitting and supine); pulse oximetry; capnography; and polysomnography. Furthermore, the threshold values available in the literature for the use of nocturnal ventilatory support and for the extension of this support through the daytime period are presented. Moreover, the maneuvers used to increase cough efficiency, as well as the proper timing of their introduction, are discussed.

Keywords: Respiratory insufficiency/diagnosis; Chronic disease; Respiratory insufficiency/therapy;

Objective: To evaluate pulmonary function and respiratory muscle strength in chronic renal failure patients, correlating these variables with hemodialysis-related weight fluctuation; to study the correlation between the duration of hemodialysis and potential respiratory alterations. Methods: Seventeen patients (median age, 47 years; interquartile range, 41-52 years), submitted to three weekly hemodialysis sessions for a median of 27 months (interquartile range, 14-55) were evaluated. Twelve of the patients were male. The patients underwent spirometry. Maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) were measured prior to and after the first hemodialysis session of the week. Body weight was quantified prior to and after each of the three weekly sessions. Results: Before the first hemodialysis session of the week, 8 patients presented mild restrictive defect, which normalized after the session in 2 of those patients. After dialysis, there was a significant increase in forced vital capacity (p = 0.02) and a significant decrease in body weight (p = 0.0001). Weight fluctuation over 3 days without hemodialysis tended to correlate with the variation in forced vital capacity in the first weekly session (r = 0.47; p = 0.055). Duration of hemodialysis correlated with predialysis MIP (r = −0.3; p = 0.03) and MEP (r = −0.63; p = 0.006). Conclusions: More pronounced weight gain in the interdialytic period is associated with worsening of lung function, which is almost fully reversible by hemodialysis. In addition, longer duration of hemodialysis is associated with decreased respiratory muscle strength.

Keywords: Spirometry; Respiratory muscles/physiopathology; Kidney failure, chronic; Renal dialysis.

Acute respiratory distress syndrome (ARDS) is characterized by diffuse alveolar damage, and evolves progressively with three phases: exsudative, fibroproliferative, and fibrotic. In the exudative phase, there are interstitial and alveolar edemas with hyaline membrane. The fibroproliferative phase is characterized by exudate organization and fibroelastogenesis. There is proliferation of type II pneumocytes to cover the damaged epithelial surface, followed by differentiation into type I pneumocytes. The fibroproliferative phase starts early, and its severity is related to the patient's prognosis. The alterations observed in the phenotype of the pulmonary parenchyma cells steer the tissue remodeling towards either progressive fibrosis or the restoration of normal alveolar architecture. The fibrotic phase is characterized by abnormal and excessive deposition of extracellular matrix proteins, mainly collagen. The dynamic control of collagen deposition and degradation is regulated by metalloproteinases and their tissular regulators. The deposition of proteoglycans in the extracellular matrix of ARDS patients needs better study. The regulation of extracellular matrix remodeling, in normal conditions or in several pulmonary diseases, such as ARDS, results from a complex mechanism that integrate the transcription of elements that destroy the matrix protein and produce activation/inhibition of several cellular types of lung tissue. This review article will analyze the ECM organization in ARDS, the different pulmonary parenchyma remodeling mechanisms, and the role of cytokines in the regulation of the different matrix components during the remodeling process.

Keywords: Respiratory distress syndrome. Pulmonary alveoli/lesions. Extracellular matrix. Cytokines/ultrastructure.

Objective: To determine the incidence of the reversed halo sign (RHS) in patients with pulmonary infarction (PI) due to acute pulmonary embolism (PE), detected by computed tomography angiography (CTA) of the pulmonary arteries, and to describe the main morphological features of the RHS. Methods: We evaluated 993 CTA scans, stratified by the risk of PE, performed between January of 2010 and December of 2014. Although PE was detected in 164 scans (16.5%), three of those scans were excluded because of respiratory motion artifacts. Of the remaining 161 scans, 75 (46.6%) showed lesions consistent with PI, totaling 86 lesions. Among those lesions, the RHS was seen in 33 (38.4%, in 29 patients). Results: Among the 29 patients with scans showing lesions characteristic of PI with the RHS, 25 (86.2%) had a single lesion and 4 (13.8%) had two, totaling 33 lesions. In all cases, the RHS was in a subpleural location. To standardize the analysis, all images were interpreted in the axial plane. Among those 33 lesions, the RHS was in the right lower lobe in 17 (51.5%), in the left lower lobe in 10 (30.3%), in the lingula in 5 (15.2%), and in the right upper lobe in 1 (3.0%). Among those same 33 lesions, areas of low attenuation were seen in 29 (87.9%). The RHS was oval in 24 (72.7%) of the cases and round in 9 (27.3%). Pleural effusion was seen in 21 (72.4%) of the 29 patients with PI and the RHS. Conclusions: A diagnosis of PE should be considered when there are findings such as those described here, even in patients with nonspecific clinical symptoms.

Keywords: Pulmonary embolism; Pulmonary infarction; Computed tomography angiography.