Estudo comparativo entre as ventilações espontânea, mandatória intermitente sincronizada, pressão de suporte e volume garantido e suporte pressórico, em coelhos anestesiados com propofol e induzidos à hipovolemia aguda

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Comparação entre a ventilação com pressão positiva intermitente ou pressão controlada em equinos anestesiados com isofluorano

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Avaliação de parâmetros cardiovasculares, ventilatórios e hemogasométricos de coelhos anestesiados com isofluorano ou sevofluorano e submetidos à ventilação espontânea ou controlada a volume

The volume-controlled mechanical ventilation and spontaneous ventilation, through haemogasometric, cardiovascular and spirometry variables were evaluated. Twenty-eight rabbits were distributed into two groups: GIVC (isoflurane and volume-controlled ventilation), GIVE (isoflurane and spontaneous ventilation), GSVC (sevoflurane and volume-controlled ventilation) and GSVE (sevoflurane and spontaneous ventilation). Induction was performed by mask with isoflurane (GIVE and GIVC) or sevoflurane (GSVE and GSVC) at 1.5 MAC in 100% oxygen. To maintain anesthesia, MAC was reset to 1. In GIVC and GSVC groups, rocuronium was administered at a dose of 0.6 mg/kg followed by its continuous infusion (0.6 mg/kg/h). In GSVE and GIVE, 0.9% NaCl was administered instead of rocuronium. Controlled ventilation was started by adjusting the capnometry in order to obtain values between 35 and 45 mmHg. Parameters were measured 60 minutes after induction of anesthesia (M0), 15 minutes after the bolus of rocuronium or 0.9% NaCl (M15) and every fifteen minutes (M30, M45 and M60). Hypercapnia and acidosis was evident in GIVC, GSVC and GSVE. We concluded that the volume-controlled mechanical ventilation was not able to maintain normocapnia in rabbits, producing acidosis in them, especially when using sevoflurane. The use of isoflurane showed greater stability than the sevoflurane anesthetic in the species studied.

Efeitos da administração de fentanil na concentração anestésica mínima e nas variáveis cardiorrespiratórias de galinhas (Gallus gallus domesticus) anestesiadas com isofluorano

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Nursing diagnoses in trauma victims with fatal outcomes in the emergency scenario

The objective of this study was to identify and analyze the nursing diagnoses that constitute risk factors for death in trauma victims in the first 6 hours post-event. This is a cross-sectional, descriptive and exploratory study using quantitative analysis. A total of 406 patients were evaluated over six months of data collection in a tertiary hospital in the municipality of Sao Paulo, according to an instrument created for this purpose. Of the total, 44 (10.7%) suffered death. Multivariate analysis indicated the nursing diagnoses ineffective respiratory pattern, impaired spontaneous ventilation, risk of bleeding and risk of ineffective gastrointestinal tissue perfusion as risk factors for death and ineffective airway clearance, impaired comfort, and acute pain as protective factors, data that can direct health teams for different interventionist actions faced with the complexity of the trauma.

Awake tracheal intubation using the Sensascope in 13 patients with an anticipated difficult airway

We present the use of the SensaScope, an S-shaped rigid fibreoptic scope with a flexible distal end, in a series of 13 patients at high risk of, or known to have, a difficult intubation. Patients received conscious sedation with midazolam or fentanyl combined with a remifentanil infusion and topical lidocaine to the oral mucosa and to the trachea via a trans-cricoid injection. Spontaneous ventilation was maintained until confirmation of tracheal intubation. In all cases, tracheal intubation was achieved using the SensaScope. The median (IQR [range]) insertion time (measured from the time the facemask was taken away from the face until an end-expiratory CO(2) reading was visible on the monitor) was 58 s (38-111 [28-300]s). In nine of the 13 cases, advancement of the SensaScope into the trachea was easy. Difficulties included a poor view associated with a bleeding diathesis and saliva, transient loss of spontaneous breathing, and difficulty in advancing the tracheal tube in a patient with unforeseen tracheal narrowing. A poor view in two patients was partially improved by a high continuous flow of oxygen. The SensaScope may be a valuable alternative to other rigid or flexible fibreoptic scopes for awake intubation of spontaneously breathing patients with a predicted difficult airway.

Evaluation of laryngeal mask as an alternative to endotracheal intubation in cats anesthetized under spontaneous or controlled ventilation

Objective To compare the cardiorespiratory effects and incidence of gastroesophageal reflux with the use of a laryngeal mask airway (LMA) or endotracheal tube (ET) in anesthetized cats during spontaneous (SV) or controlled ventilation (CV).Study design Prospective randomized experimental trial.Animals Thirty-two adult crossbred cats, weighing 2.7 +/- 0.4 kg.Methods the cats were sedated with intramuscular (IM) methotrimeprazine (0.5 mg kg(-1)) and buprenorphine (0.005 mg kg(-1)), followed 30 minutes later by induction of anesthesia with intravenous (IV) thiopental (12.5-20 mg kg(-1)). An ET was used in 16 cats and an LMA in the remaining 16 animals. Anesthesia was maintained with 0.5 minimum alveolar concentration (0.6%) of halothane in oxygen using a Mapleson D breathing system. Cats in both groups were further divided into two equal groups (n = 8), undergoing either SV or CV. Neuromuscular blockade with pancuronium (0.06 mg kg(-1)) was used to facilitate CV. Heart and respiratory rates, direct arterial blood pressure, capnometry (PE'CO2) and arterial blood gases were measured. Gastric reflux and possible aspiration was investigated by intragastric administration of 5 mL of radiographic contrast immediately after induction of anesthesia. Cervical and thoracic radiographs were taken at the end of anesthesia. Data were analyzed using ANOVA followed by Student-Newman-Keuls, Kruskal-Wallis or Friedman test where appropriate.Results Values for PaCO2 and PE'CO2 were higher in spontaneously breathing cats with the LMA when compared with other groups. Values of PaO2 and hemoglobin oxygen saturation did not differ between groups. Gastroesophageal reflux occurred in four of eight and two of eight cats undergoing CV with ET or LMA, respectively. There was no tracheal or pulmonary aspiration in any cases.Conclusions and clinical relevance the use of an LMA may be used as an alternative to endotracheal intubation in anesthetized cats. Although aspiration was not observed, gastric reflux may occur in mechanically ventilated animals.

Spontaneous combustion and simulation of mine fires and their effects on mine ventilation systems

The structure of a comprehensive research project into mine fires study applying the Ventgraph mine fire simulation software, preplanning of escape scenarios and general interaction with rescue responses is outlined. The project has Australian Coal Association Research Program (ACARP) funding and also relies on substantial mining company site support. This practical input from mine operators is essential and allows the approach to be introduced in the most creditable way. The effort is built around the introduction of fire simulation computer software to the Australian mining industry and the consequent modelling of fire scenarios in selected different mine layouts. Application of the simulation software package to the changing mine layouts requires experience to achieve realistic outcomes. Most Australian mines of size currently use a ventilation network simulation program. Under the project a small subroutine has been written to transfer the input data from the existing mine ventilation network simulation program to ‘Ventgraph’. This has been tested successfully. To understand fire simulation behaviour on the mine ventilation system, it is necessary to understood the possible effects of mine fires on various mine ventilation systems correctly first. Case studies demonstrating the possible effects of fires on some typical Australian coal mine ventilation circuits have been examined. The situation in which there is some gas make at the face and effects with fire have also been developed to emphasise how unstable and dangerous situations may arise. The primary objective of the part of the study described in this paper is to use mine fire simulation software to gain better understanding of how spontaneous combustion initiated fires can interact with the complex ventilation behaviour underground during a substantial fire. It focuses on the simulation of spontaneous combustion sourced heatings that develop into open fires. Further, it examines ventilation behaviour effects of spontaneous combustion initiated pillar fires and examines the difficulties these can be present if a ventilation reversal occurs. It also briefly examines simulation of use of the inertisation to assist in mine recovery. Mine fires are recognised across the world as a major hazard issue. New approaches allowing improvement in understanding their consequences have been developed as an aid in handling this complex area.

Assisted ventilation modes reduce the expression of lung inflammatory and fibrogenic mediators in a model of mild acute lung injury

The goal of the study was to compare the effects of different assisted ventilation modes with pressure controlled ventilation (PCV) on lung histology, arterial blood gases, inflammatory and fibrogenic mediators in experimental acute lung injury (ALI). Paraquat-induced ALI rats were studied. At 24 h, animals were anaesthetised and further randomized as follows (n = 6/group): (1) pressure controlled ventilation mode (PCV) with tidal volume (V (T)) = 6 ml/kg and inspiratory to expiratory ratio (I:E) = 1:2; (2) three assisted ventilation modes: (a) assist-pressure controlled ventilation (APCV1:2) with I:E = 1:2, (b) APCV1:1 with I:E = 1:1; and (c) biphasic positive airway pressure and pressure support ventilation (BiVent + PSV), and (3) spontaneous breathing without PEEP in air. PCV, APCV1:1, and APCV1:2 were set with P (insp) = 10 cmH(2)O and PEEP = 5 cmH(2)O. BiVent + PSV was set with two levels of CPAP [inspiratory pressure (P (High) = 10 cmH(2)O) and positive end-expiratory pressure (P (Low) = 5 cmH(2)O)] and inspiratory/expiratory times: T (High) = 0.3 s and T (Low) = 0.3 s. PSV was set as follows: 2 cmH(2)O above P (High) and 7 cmH(2)O above P (Low). All rats were mechanically ventilated in air and PEEP = 5 cmH(2)O for 1 h. Assisted ventilation modes led to better functional improvement and less lung injury compared to PCV. APCV1:1 and BiVent + PSV presented similar oxygenation levels, which were higher than in APCV1:2. Bivent + PSV led to less alveolar epithelium injury and lower expression of tumour necrosis factor-alpha, interleukin-6, and type III procollagen. In this experimental ALI model, assisted ventilation modes presented greater beneficial effects on respiratory function and a reduction in lung injury compared to PCV. Among assisted ventilation modes, Bi-Vent + PSV demonstrated better functional results with less lung damage and expression of inflammatory mediators.

Patient-ventilator asynchrony during noninvasive ventilation: a bench and clinical study.

BACKGROUND: Different kinds of ventilators are available to perform noninvasive ventilation (NIV) in ICUs. Which type allows the best patient-ventilator synchrony is unknown. The objective was to compare patient-ventilator synchrony during NIV between ICU, transport-both with and without the NIV algorithm engaged-and dedicated NIV ventilators. METHODS: First, a bench model simulating spontaneous breathing efforts was used to assess the respective impact of inspiratory and expiratory leaks on cycling and triggering functions in 19 ventilators. Second, a clinical study evaluated the incidence of patient-ventilator asynchronies in 15 patients during three randomized, consecutive, 20-min periods of NIV using an ICU ventilator with and without its NIV algorithm engaged and a dedicated NIV ventilator. Patient-ventilator asynchrony was assessed using flow, airway pressure, and respiratory muscles surface electromyogram recordings. RESULTS: On the bench, frequent auto-triggering and delayed cycling occurred in the presence of leaks using ICU and transport ventilators. NIV algorithms unevenly minimized these asynchronies, whereas no asynchrony was observed with the dedicated NIV ventilators in all except one. These results were reproduced during the clinical study: The asynchrony index was significantly lower with a dedicated NIV ventilator than with ICU ventilators without or with their NIV algorithm engaged (0.5% [0.4%-1.2%] vs 3.7% [1.4%-10.3%] and 2.0% [1.5%-6.6%], P < .01), especially because of less auto-triggering. CONCLUSIONS: Dedicated NIV ventilators allow better patient-ventilator synchrony than ICU and transport ventilators, even with their NIV algorithm. However, the NIV algorithm improves, at least slightly and with a wide variation among ventilators, triggering and/or cycling off synchronization.

Sub-cortical and brainstem sites associated with chemo-stimulated increases in ventilation in humans.

We investigated the neural basis for spontaneous chemo-stimulated increases in ventilation in awake, healthy humans. Blood oxygen level dependent (BOLD) functional MRI was performed in nine healthy subjects using T2 weighted echo planar imaging. Brain volumes (52 transverse slices, cortex to high spinal cord) were acquired every 3.9 s. The 30 min paradigm consisted of six, 5-min cycles, each cycle comprising 45 s of hypoxic-isocapnia, 45 s of isooxic-hypercapnia and 45 s of hypoxic-hypercapnia, with 55 s of non-stimulatory hyperoxic-isocapnia (control) separating each stimulus period. Ventilation was significantly (p<0.001) increased during hypoxic-isocapnia, isooxic-hypercapnia and hypoxic-hypercapnia (17.0, 13.8, 24.9 L/min respectively) vs. control (8.4 L/min) and was associated with significant (p<0.05, corrected for multiple comparisons) signal increases within a bilateral network that included the basal ganglia, thalamus, red nucleus, cerebellum, parietal cortex, cingulate and superior mid pons. The neuroanatomical structures identified provide evidence for the spontaneous control of breathing to be mediated by higher brain centres, as well as respiratory nuclei in the brainstem.

Feasibility of non-invasive pressure support ventilation in infants with respiratory failure after extubation: a pilot study.

OBJECTIVE: To evaluate the feasibility and effects of non-invasive pressure support ventilation (NIV) on the breathing pattern in infants developing respiratory failure after extubation. DESIGN: Prospective pilot clinical study; each patient served as their own control. SETTING: A nine-bed paediatric intensive care unit of a tertiary university hospital. PATIENTS: Six patients (median age 5 months, range 0.5-7 months; median weight 4.2 kg, range 3.8-5.1 kg) who developed respiratory failure after extubation. INTERVENTIONS: After a period of spontaneous breathing (SB), children who developed respiratory failure were treated with NIV. MEASUREMENTS AND RESULTS: Measurements included clinical dyspnoea score (DS), blood gases and oesophageal pressure recordings, which were analysed for respiratory rate (RR), oesophageal inspiratory pressure swing (dPes) and oesophageal pressure-time product (PTPes). All data were collected during both periods (SB and NIV). When comparing NIV with SB, DS was reduced by 44% (P < 0.001), RR by 32% (P < 0.001), dPes by 45% (P < 0.01) and PTPes by 57% (P < 0.001). A non-significant trend for decrease in PaCO(2) was observed. CONCLUSION: In these infants, non-invasive pressure support ventilation with turbine flow generator induced a reduction of breathing frequency, dPes and PTPes, indicating reduced load of the inspiratory muscles. NIV can be used with some benefits in infants with respiratory failure after extubation.

Variability of neurally-adjusted ventilatory assist (nava) compared to pressure support ventilation (psv) during the weaning phase of mechanical ventilation.

Rationale: NAVA is an assisted ventilatory mode that uses the electrical activity of the diaphragm (Edi) to trigger and cycle the ventilator, and to offer inspiratory assistance in proportion to patient effort. Since Edi varies from breath to breath, airway pressure and tidal volume also vary according to the patient's breathing pattern. Our objective was to compare the variability of NAVA with PSV in mechanically ventilated patients during the weaning phase. Methods: We analyzed the data collected for a clinical trial that compares PSV and NAVA during spontaneous breathing trials using PSV, with PS of 5 cmH2O, and NAVA, with Nava level titrated to generate a peak airway pressure equivalent to PSV of 5 cmH2O (NCT01137271). We captured flow, airway pressure and Edi at 100Hz from the ventilator using a dedicated software (Servo Tracker v2, Maquet, Sweden), and processed the cycles using a MatLab (Mathworks, USA) code. The code automatically detects the tidal volume (Vt), respiratory rate (RR), Edi and Airway pressure (Paw) on a breath-by-breath basis for each ventilatory mode. We also calculated the coefficient of variation (standard deviation, SD, divided by the mean). Results: We analyzed data from eleven patients. The mean Vt was similar on both modes (370 ±70 for Nava and 347± 77 for PSV), the RR was 26±6 for Nava and 26±7 or PSV. Paw was higher for Nava than for PSV (14±1 vs 11±0.4, p=0.0033), and Edi was similar for both modes (12±8 for Nava and 11±6 for PSV). The variability of the respiratory pattern, assessed with the coefficient of variation, was larger for Nava than for PSV for the Vt ( 23%±1% vs 15%±1%, p=0.03) and Paw (17%±1% vs 1% ±0.1%, p=0.0033), but not for RR (21% ±1% vs 16% ±8%, p=0.050) or Edi (33%±14% vs 39% ±16%,p=0.07). Conclusion: The variability of the breathing pattern is high during spontaneous breathing trials independent of the ventilatory mode. This variability results in variability of airway pressure and tidal volume, which are higher on Nava than on PSV. Our results suggest that Nava better reflects the normal variability of the breathing pattern during assisted mechanical ventilation.

Effectiveness of nitric oxide during spontaneous breathing in experimental lung injury

Inhaled nitric oxide (iNO) improves gas exchange in about 60% of patients with acute respiratory distress syndrome (ARDS). Recruitment of atelectatic lung areas may improve responsiveness and preservation of spontaneous breathing (SB) may cause recruitment. Accordingly, preservation of SB may improve effectiveness of iNO. To test this hypothesis, iNO was evaluated in experimental acute lung injury (ALI) during SB. In 24 pigs with ALI, effects of 10 ppm iNO were evaluated during controlled mechanical ventilation (CMV) and SB in random order. Preservation of SB was provided by 4 different modes: Unassisted SB was enabled by biphasic positive airway pressure (BIPAP), moderate inspiratory assist was provided by pressure support (PS) and volume-assured pressure support (VAPS), maximum assist was ensured by assist control (A/C). Statistical analysis did not reveal gas exchange improvements due to SB alone. Significant gas exchange improvements due to iNO were only achieved during unassisted SB with BIPAP (P <.05) but not during CMV or assisted SB. The authors conclude that effectiveness of iNO may be improved by unassisted SB during BIPAP but not by assisted SB. Thus combined iNO and unassisted SB is possibly most effective to improve gas exchange in severe hypoxemic ARDS.

[Spontaneous dural arterio-venous fistula at the cavernous sinus: detected by decompensation following endoscopic sinus surgery]

Spontaneous dural arterio-venous fistulas can imperceptibly develop over a long time period before they suddenly develop symptoms like bruit, loss of vision, exophthalmos and conjunctival injection. We present the rare case of an occult, para-infectious, dural arterio-venous fistula which became symptomatic after endoscopic sinus surgery. Conjunctival injection and slight exophthalmos developed due to decompensation of venous drainage probably by intraoperative positioning of the patient, positive pressure ventilation and nasal packing.