Performance characteristics of high-frequency percussive ventilation under hyperbaric conditions.

Introduction: Safe administration of critical care hyperbaric medicine requires specialized equipment and advanced training. Equipment must be tested in order to evaluate function in the hyperbaric environment. High-frequency percussive ventilation (HFPV) has been used in intensive care settings effectively, but it has never been tested in a hyperbaric chamber. Methods: Following a modified U.S. Navy testing protocol used to evaluate hyperbaric ventilators, we evaluated an HFPV transport ventilator in a multiplace hyperbaric chamber at 1.0, 1.9, and 2.8 atmospheres absolute (ATA). We used a test lung with analytical software for data collection. The ventilator uses simultaneous cyclic pressure-controlled ventilation at a pulsatile flow rate (PFR)/oscillatory continuous positive airway pressure (oCPAP) ratio of 30/10 with a high-frequency oscillation percussive rate of 500 beats per minute. Inspiratory and expiratory times were maintained at two seconds throughout each breathing cycle. Results: During manned studies, the PFR/oCPAP ratios were 26/6, 22/7, and 22.5/8 at an airway resistance of 20cm H2O/L/second and 18/9, 15.2/8.5, and 13.6/7 at an airway resistance of 50 cm/H2O/L/second at 1, 1.9, and 2.8 ATA. The resulting release volumes were 800, 547, and 513 mL at airway resistance of 20 cm H2O/L/sec and 400, 253, and 180 mL at airway resistance of 50 cm/H2O/L/sec at 1, 1.9, and 2.8 ATA. Unmanned testing showed similar changes. The mean airway pressure (MAP) remained stable throughout all test conditions; theoretically, supporting adequate lung recruitment and gas exchange. A case where HFPV was used to treat a patient for CO poisoning was presented to illustrate that HFPV worked well under HBO2 conditions and no complications occurred during HBO2 treatment. Conclusion: The HFPV transport ventilator performed adequately under hyperbaric conditions and should be considered a viable option for hyperbaric critical care. This ventilator has atypical terminology and produces unique pulmonary physiology, thus requiring specialized training prior to use.

Effectiveness of high-frequency oscillatory ventilation for the treatment of neonatal meconium aspiration syndrome.

BACKGROUND: The purpose of this study is to raise nonjudgmental awareness and attention to current experience of high-frequency oscillatory ventilation (HFOV) for the treatment of neonatal meconium aspiration syndrome (NMAS). METHODS: We will comprehensively search literature from the databases of Cochrane Library, PubMed, Embase, Web of Science, WorldSciNet, PsycINFO, Allied and Complementary Medicine Database, Chinese Biomedical Literature Database, and China National Knowledge Infrastructure from inception until July 1, 2019 without language limitation. We will also handle searching the bibliographies of all relevant studies found for unpublished literatures. Statistical analysis will be conducted using RevMan 5.3 software. RESULTS: The outcomes include function inhaled oxygen concentration, oxygenation index, arterial oxygen tension/alveolar arterial oxygen tension, partial pressure of oxygen, partial pressure of carbon dioxide, transcutaneous arterial oxygen saturation, duration of hospitalization, and adverse events. CONCLUSION: This study will provide an exhaustive view of HFOV for treating infants with NMAS. PROSPERO REGISTRATION NUMBER: PROSPERO CRD42019140520.

High-Frequency Airway Oscillating Device for Respiratory Muscle Training in Subjects With COPD.

BACKGROUND: COPD is characterized by expiratory flow limitation, which results in symptomatic dyspnea and reduced exercise capacity. Changes in breathing mechanics mean the respiratory muscles are unable to respond to the ventilatory demands, increasing the sensation of dyspnea. A high-frequency oscillating device has been developed to improve dyspnea in patients with COPD. We conducted a feasibility trial to gain insight into the potential for recruitment, retention, and study design for a future randomized controlled trial. METHODS: Symptomatic subjects with COPD were included on the basis of a Medical Research Council (MRC) score ≥ 3 and FEV1/FVC < 0.70). Patients were excluded if they received pulmonary rehabilitation within the last 6 months. The intervention employed the device for 8 weeks, 3 times daily. Clinical outcomes included the MRC score, maximal expiratory and inspiratory pressures (PEmax/PImax), the incremental shuttle walk test (ISWT), and the endurance shuttle walk test (ESWT). RESULTS: We successfully recruited 23 subjects with established COPD (65.2% male, mean age 65 ± 5.03 y, mean % predicted FEV1 43.9 ± 16, mean FEV1/FVC ratio 0.46 ± 0.13, and median [interquartile range] MRC 4 [3-5]). There was a significant change in MRC from 4 to 3 pre to post intervention (P = .003). There was a statistically significant difference in PEmaxP < .008 and PImaxP = .044. There were no significant differences observed in the ISWT or ESWT. CONCLUSIONS: This study design appeared feasible to proceed to a clinical effectiveness trial. The use of the device for 8 weeks showed a significant improvement in PEmax, PImax, and reduced symptomatic dyspnea on the MRC dyspnea score. The results of this study should encourage a randomized controlled trial.

Inspiratory high frequency airway oscillation attenuates resistive loaded dyspnea and modulates respiratory function in young healthy individuals.

Direct chest-wall percussion can reduce breathlessness in Chronic Obstructive Pulmonary Disease and respiratory function may be improved, in health and disease, by respiratory muscle training (RMT). We tested whether high-frequency airway oscillation (HFAO), a novel form of airflow oscillation generation can modulate induced dyspnoea and respiratory strength and/or patterns following 5 weeks of HFAO training (n = 20) compared to a SHAM-RMT (conventional flow-resistive RMT) device (n = 15) in healthy volunteers (13 males; aged 20-36 yrs). HFAO causes oscillations with peak-to-peak amplitude of 1 cm H2O, whereas the SHAM-RMT device was identical but created no pressure oscillation. Respiratory function, dyspnoea and ventilation during 3 minutes of spontaneous resting ventilation, 1 minute of maximal voluntary hyperventilation and 1 minute breathing against a moderate inspiratory resistance, were compared PRE and POST 5-weeks of training (2 × 30 breaths at 70% peak flow, 5 days a week). Training significantly reduced NRS dyspnoea scores during resistive loaded ventilation, both in the HFAO (p = 0.003) and SHAM-RMT (p = 0.005) groups. Maximum inspiratory static pressure (cm H2O) was significantly increased by HFAO training (vs. PRE; p<0.001). Maximum inspiratory dynamic pressure was increased by training in both the HFAO (vs. PRE; p<0.001) and SHAM-RMT (vs. PRE; p = 0.021) groups. Peak inspiratory flow rate (L.s(-1)) achieved during the maximum inspiratory dynamic pressure manoeuvre increased significantly POST (vs. PRE; p = 0.001) in the HFAO group only. HFAO reduced inspiratory resistive loading-induced dyspnoea and augments static and dynamic maximal respiratory manoeuvre performance in excess of flow-resistive IMT (SHAM-RMT) in healthy individuals without the respiratory discomfort associated with RMT.

Pulmonary sequelae of severe H1N1 infection treated with high frequency oscillatory ventilation.

During the recent influenza A (H1N1) pandemic, due to severe respiratory failure many patients required treatment with alternative ventilator modalities including High Frequency Oscillatory Ventilation (HFOV). We present four such patients treated with HFOV at an academic, tertiary referral hospital in Ireland. We detail outcomes of clinical examination, pulmonary function testing, quality of life assessment and radiographic appearance on CT Thorax at follow-up at 6 months. Further clinical assessment and pulmonary function testing were performed at median 19 months (range 18-21 months) post-discharge. At initial review all patients were found to have reduced gas transfer (median predicted DLCO 74%) with preservation of lung volumes and normal spirometrical values at 6 months (median FVC 5.42L [101% predicted] and FEV14.5L [101.2% predicted] respectively), with improvements in gas transfer (median predicted DLCO 83%)at subsequent testing. Post-inflammatory changes on CT thorax at 6 months were seen in all 4 cases. To our knowledge this is the first report to document the long-term effects of severe H1N1 infection requiring high frequency oscillation on respiratory function. We conclude that the effects on respiratory function and pulmonary radiological appearance are similar to those observed following conventional treatment of Acute Respiratory Distress Syndrome [ARDS].

A comparison of the Acapella and a threshold inspiratory muscle trainer for sputum clearance in bronchiectasis-A pilot study.

BACKGROUND: Inspiratory muscle training is used to specifically strengthen the respiratory muscles. Controversy exists regarding the use of inspiratory muscle training as a method of facilitating airways clearance. Acapella is already known to be effective in airway clearance. OBJECTIVE: The objective of the study was to compare the effects of the Acapella and a threshold inspiratory muscle trainer as a method of airway clearance in subjects with bronchiectasis and to determine patient preference between the two techniques. METHODS: Thirty patients (10 males, 20 females) mean age of 50.67+/-6.37 (mean+/-SD) with a history of expectoration of more than 30 ml sputum per day were recruited. The sequence of therapy was allocated by block randomization. Assessment and familiarization session was performed on day 1. Treatments employing the Acapella and inspiratory muscle trainer were done on days 2 and 3. Treatment order and allocation was determined by block randomization. Sputum volume was measured during and 2 hours after the treatment and patient treatment preference was recorded. RESULTS: A statistically significant difference was found in the sputum volume expectorated after treatment with the Acapella (7.16+/-1.12 ml) compared with the threshold inspiratory muscle trainer (6.46+/-1.08 ml). Patients preferred Acapella in terms of usefulness of clearing secretions. CONCLUSION: The present study demonstrated increased sputum clearance following the use of the Acapella when compared to the threshold inspiratory muscle trainer. In addition, the Acapella was preferred by patients who judged that it was more useful in clearing secretions.

Persistent Pulmonary Hypertension of the Newborn

Persistent pulmonary hypertension of the newborn (PPHN) is defined as a failure of normal pulmonary vascular relaxation at or shortly after birth, resulting in impedance to pulmonary blood flow which exceeds systemic vascular resistance, such that unoxygenated blood is shunted to the systemic circulation. Perinatal stressors including hypoxia, hypoglycemia, cold stress, sepsis, and direct lung injury alter the course of transition. The initial clinical picture of PPHN is one of dynamic pulmonary vasospasm, with labile flow through the pulmonary circuit and right-to-left shunting of blood across the ductus arteriosus and foramen ovale. The normal postnatal decline in pulmonary vascular tone is absent following exposure to chronic hypoxia. The pathophysiology of neonatal pulmonary hypertension can involve multiple pathways of injury, from altered circulating agonist balance, to endothelial dysfunction, to smooth muscle dysfunction and phenotypic change. The treatment for PPHN has evolved over the past 10 to 15 years but reported mortality remains at 10% to 20% in newborns with PPHN. Extracorporeal membrane oxygenation (ECMO) has been proven of value for this condition, and several "alternative" therapies such as high-frequency ventilation (HFV), surfactant, and inhaled NO (iNO) have been used in a rescue mode.

Persistent Pulmonary Hypertension of the Newborn

Persistent pulmonary hypertension of the newborn (PPHN) is defined as a failure of normal pulmonary vascular relaxation at or shortly after birth, resulting in impedance to pulmonary blood flow which exceeds systemic vascular resistance, such that unoxygenated blood is shunted to the systemic circulation. Perinatal stressors including hypoxia, hypoglycemia, cold stress, sepsis, and direct lung injury alter the course of transition. The initial clinical picture of PPHN is one of dynamic pulmonary vasospasm, with labile flow through the pulmonary circuit and right-to-left shunting of blood across the ductus arteriosus and foramen ovale. The normal postnatal decline in pulmonary vascular tone is absent following exposure to chronic hypoxia. The pathophysiology of neonatal pulmonary hypertension can involve multiple pathways of injury, from altered circulating agonist balance, to endothelial dysfunction, to smooth muscle dysfunction and phenotypic change. The treatment for PPHN has evolved over the past 10 to 15 years but reported mortality remains at 10% to 20% in newborns with PPHN. Extracorporeal membrane oxygenation (ECMO) has been proven of value for this condition, and several "alternative" therapies such as high-frequency ventilation (HFV), surfactant, and inhaled NO (iNO) have been used in a rescue mode.

High-frequency gamma-band activity in the basal temporal cortex during picture-naming and lexical-decision tasks.

Gamma-band activity (GBA) in electroencephalograms (EEGs) has been shown to reflect various cognitive processes. GBA has typically been recorded in the 30-60 Hz range in scalp EEGs. Recently, task-related "high GBA" (HGBA) with frequencies up to 100 Hz has been observed in studies with invasive electrocorticograms (ECoGs). In the present study, we recorded ECoGs from the bilateral basal temporal cortices in a patient with epilepsy and evaluated the task-related HGBA (most prominently in the 80-120 Hz range) accompanying picture-naming and lexical-decision tasks. We examined picture naming using two categories (line drawings of animals and tools). The lexical-decision task was performed using words and pseudowords of two distinct Japanese writing forms, kanji (morphograms) and kana (syllabograms). Task-related HGBA was observed bilaterally during the naming task. Recordings from some electrodes revealed significant differences in HGBA between animal and tool pictures. In contrast to the naming task, there was apparent left dominance in the lexical-decision task. Furthermore, significant differences in HGBA were observed between the Japanese kanji and kana words and between the kanji words and kanji pseudowords. A number of differences in the HGBA observed in the recordings from the basal temporal area were consistent with previous findings from neuroimaging and patient studies and suggest that HGBA is a good correlate of visual cognitive functions.

Oscillating field stimulation for complete spinal cord injury in humans: a phase 1 trial.

OBJECT: An electrical field cathode (negative pole) has trophic and tropic effects on injured spinal cord axons in in vitro and in vivo models of sea lamprey, rodent, and canine spinal cord injury (SCI) and it improves functional outcome. A human oscillating field stimulator (OFS) was built, a Food and Drug Administration (FDA) exemption number was obtained, and institutional review board approval was given for a Phase 1 trial to study 10 humans with complete motor and sensory SCI. METHODS: Entry criteria were complete SCI between C-5 and T-10 in patients 18 to 65 years of age and no transection demonstrated on magnetic resonance imaging. All participants received the National Acute Spinal Cord Injury Study (NASCIS) III methylprednisilone protocol. Cord compression and/or vertebral instability was treated before study entry. After treatment complete SCI (according to the American Spinal Injury Association [ASIA] score) remained in all patients with no somatosensory evoked potentials (SSEPs) below the injury level after surgery or for 48 hours. All patients underwent implantation of the OFS within 18 days. Patients underwent evaluation every 2 weeks postimplantation; the OFS was explanted at 15 weeks. Independent neurological status was assessed based on the ASIA score, visual analog scale (VAS) pain score, and SSEPs at 6 weeks, 6 months, and 1 year. Statistical analyses were performed using the two-tailed Wilcoxon test and analysis of variance (ANOVA). There were no complications at insertion of the OFS; there was one case of wound infection after explantation (5% infection rate). One patient was lost to follow up after 6 months. In all 10 patients the mean VAS pain score was 8 at implantation, 2 at 6 months, and in the nine attending follow up for 1 year it remained 2. At 1 year, the mean improvement in light touch was 25.5 points (ANOVA p < 0.001, Wilcoxon test p = 0.02), the mean improvement in pinprick sensation was 20.4 points (ANOVA p < 0.001, Wilcoxon test p = 0.02), and the mean improvement in motor status was 6.3 points (ANOVA p < 0.01, Wilcoxon test p = 0.02). Of five cases involving cervical cord injuries, bilateral upper-extremity SSEPs were normal in one, unilateral upper-extremity SSEPs were recovered in four, bilateral upper-extremity SSEPs were recovered in one, and abnormal lower-extremity SSEPs resolved in one case. In one of the five cases involving thoracic injuries an abnormal lower-extremity SSEP resolved. CONCLUSIONS: The use of OFS treatment in patients with SCI is safe, reliable, and easy. Compared with the outcomes obtained in compliant NASCIS III plegic patients, the results of the present study indicate efficacy, and the FDA has given permission for enrollment of 10 additional patients.

Heart rate dynamics during three forms of meditation.

OBJECTIVE: This study was designed to quantify and compare the instantaneous heart rate dynamics and cardiopulmonary interactions during sequential performance of three meditation protocols with different breathing patterns. BACKGROUND: We analyzed beat-to-beat heart rate and continuous breathing signals from 10 experienced meditators (4 females; 6 males; mean age 42 years; range 29-55 years) during three traditional interventions: relaxation response, breath of fire, and segmented breathing. RESULTS: Heart rate and respiratory dynamics were generally similar during the relaxation response and segmented breathing. We observed high amplitude, low frequency (approximately 0.05-0.1 Hz) oscillations due to respiratory sinus arrhythmia during both the relaxation response and segmented breathing, along with a significantly (p<0.05) increased coherence between heart rate and breathing during these two maneuvers when compared to baseline. The third technique, breath of fire, was associated with a different pattern of response, marked by a significant increase in mean heart rate with respect to baseline (p<0.01), and a significant decrease in coherence between heart rate and breathing (p<0.05). CONCLUSIONS: These findings suggest that different meditative/breathing protocols may evoke common heart rate effects, as well as specific responses. The results support the concept of a "meditation paradox," since a variety of relaxation and meditative techniques may produce active rather than quiescent cardiac dynamics, associated with prominent low frequency heart rate oscillations or increases in mean resting heart rate. These findings also underscore the need to critically assess traditional frequency domain heart rate variability parameters in making inferences about autonomic alterations during meditation with slow breathing.

Learning-induced modulation of oscillatory activities in the mammalian olfactory system: the role of the centrifugal fibres.

In the mammalian olfactory system, oscillations related to odour representation have been described in field potential activities. Previous results showed that in olfactory bulb (OB) of awake rats engaged in an olfactory learning, odour presentation produced a decrease of oscillations in gamma frequency range (60-90 Hz) associated with a power increase in beta frequency range (15-40 Hz). This response pattern was strongly amplified in trained animals. The aim of this work was twofold: whether learning also induces similar changes in OB target structures and whether such OB response depends on its centrifugal inputs. Local field potentials (LFPs) were recorded through chronically implanted electrodes in the OB, piriform and enthorhinal cortices of freely moving rats performing an olfactory discrimination. Oscillatory activities characteristics (amplitude, frequency and time-course) were extracted in beta and gamma range by a wavelet analysis. First, we found that odour induced beta oscillatory activity was present not only in the OB, but also in the other olfactory structures. In each recording site, characteristics of the beta oscillatory responses were dependent of odour, structure and learning level. Unilateral section of the olfactory peduncle was made before training, and LFPs were symmetrically recorded in the two bulbs all along the acquisition of the learning task. Data showed that deprivation of centrifugal feedback led to an increase of spontaneous gamma activity. Moreover, under this condition olfactory learning was no longer associated with the typical large beta band. As a whole, learning modulation of the beta oscillatory response in olfactory structures may reflect activity of a distributed functional network involved in odour representation.

El aporte de la cirugía bariátrica en el tratamiento del síndrome de Pickwick / Contribution of bariatric surgery in the treatment of Pickwick syndrome

El conjunto de alteraciones respiratorias que sufren los obesos mórbidos y que llevan a la hipoxemia e hipercapnia crónica, con poliglobulia compensatoria y falla cardíaca derecha secundaria es conocida desde hace tiempo como Síndrome de Pickwick. Su tratamiento médico es complejo y poco efectivo, siendo en la actualidad la cirugía bariátrica la que mejores resultados obtiene. En una serie de seis pacientes, con este cuadro, operados desde 1980 por el autor principal, sus resultados han sido muy satisfactorios al corregir rápida y efectivamente las graves alteraciones respiratorias presentes, corroborando lo descrito por la literatura mundial

Endogenous pulmonary surfactant metabolism is not affected by mode of ventilation in premature infants with respiratory distress syndrome.

OBJECTIVE: To determine if high frequency oscillatory ventilation (HFOV) decreases surfactant production in premature infants with respiratory distress syndrome (RDS). STUDY DESIGN: We randomized 19 infants <28 weeks of gestation to either HFOV (n = 8) or conventional ventilation (CV, n = 11) at 24 hours of life. After a 24-hour continuous infusion of uniformly labeled carbon 13 glucose (U-(13)C(6)) glucose, we measured (13)C enrichment in surfactant phosphatidylcholine (PC) in tracheal aspirate samples using gas chromatography/mass spectrometry. We calculated the fractional synthetic rate (FSR) of surfactant PC from labeled glucose and its half-life of clearance (T(1/2)). RESULTS: FSR did not differ between groups (4.7% +/- 2.7%/day CV vs 4.2% +/- 3.1%/day HFOV, P =.7). T(1/2) was 79 +/- 18 hours in the CV group and 76 +/- 23 hours in the HFOV group (P =.7). Neither degree of ventilatory support nor supplemental oxygen exposure correlated with surfactant metabolic indices. Three of 4 infants who died from RDS within the first month of life had a shorter T(1/2) than 14 of 15 infants who survived. CONCLUSION: Surfactant metabolism is similar in preterm infants ventilated with HFOV and CV. Shortened surfactant half-life may characterize a subset of preterm infants with lethal RDS.

Airway clearance strategies for the pediatric patient.

Clinicians who care for cystic fibrosis (CF) patients have many techniques to choose from to facilitate mucus clearance. Little has been published about when to introduce the various techniques and in what order to teach them. Debates have occurred over these issues in the CF community, and there is now consensus on some topics. It is very important to teach adherence to therapy at an early age. Adherence to an airway clearing regimen assists in maintaining good pulmonary function in CF patients. Knowing when and how to introduce airway clearance techniques beyond chest physiotherapy (CPT) is clinically relevant and useful. A 5-position modified CPT routine can be used with infants and children, and it takes less time and may improve adherence. Infants and toddlers can be taught breathing games that eventually lead them to perform diaphragmatic breathing and huffing. Once they have mastered diaphragmatic breathing and huffing, children can be taught the active cycle of breathing technique. Modified CPT can be phased out at that point. Positive expiratory pressure therapy can usually be introduced around 6-7 years of age. High-frequency chest wall oscillation, oscillating positive expiratory pressure, and autogenic drainage all follow. CF patients should be given every opportunity to learn and master various techniques to promote mucus clearance.

Optimizing intrapulmonary perfluorocarbon distribution: fluoroscopic comparison of mode of ventilation and body position.

OBJECTIVE: Partial liquid ventilation with the perfluorochemical, perflubron, has been shown to improve lung mechanics and enhance gas exchange in the treatment of severe acute lung injury. However, the most effective strategy to provide optimal intrapulmonary distribution of perflubron has not been fully accessed. The objective of this study was to examine the effect of body position (supine vs. rotational) and mode of ventilation (conventional mechanical ventilation [CMV] vs. high-frequency oscillatory ventilation [HFOV]) on perflubron distribution and oxygenation improvement. DESIGN: Prospective, randomized, animal trial. SETTING: Research laboratory at a university medical center. SUBJECTS: Twenty healthy piglets (4.5-6.6 kg). INTERVENTIONS: Subjects underwent repetitive saline lavage to achieve a uniform degree of lung injury and then were randomized to either CMV or were converted to HFOV. Within each ventilator group, animals were randomized to supine positioning (S) or rotational positioning with alternation between supine and prone position (R) during incremental dosing of three 5-mL/kg doses of perflubron. MEASUREMENTS AND MAIN RESULTS: Arterial blood gas tensions, hemodynamic variables, and the oxygenation index were recorded after each dose of 5 mL/kg. Lateral cinefluoroscopic images after each dose were digitized for computer analysis of density. A density index was calculated for a 2-cm2 window in three dorsal and three ventral lung regions. Uniformity of distribution was calculated by comparing the mean density among the six regions. Oxygenation improvements were compared between groups. There were no significant differences in hemodynamic variables or gas exchange after lung injury in the four groups. Rotational positioning produced significantly more uniform perflubron distribution during both CMV and HFOV. This effect was independent of the mode of ventilation. The mean ventral density index was affected by rotating position and HFOV mode of ventilation after 10 mL/kg of perflubron, and rotating position was affected only after 15 mL/kg of perflubron. There was a significant reduction in the oxygenation index from baseline to end lavage in both CMV groups, as well as all of the animals that were rotated. CONCLUSION: Perflubron is more uniformly dispersed when dosed in a rotational fashion with alternation between supine and prone position during incremental dosing. This effect is independent of mode of ventilation. There was no relationship between oxygenation improvements and nondependent perflubron distribution. CMV and rotating dosing both led to a significant decrease in the oxygenation index after a 15 mL/kg dose of perflubron. This information has important impact on the future development of dosing strategies and clinical trial design.

Cataract surgery performed with continuous positive airway pressure (CPAP) ventilation.

PURPOSE: To report a case in which cataract surgery was performed under local anesthesia, with continuous positive airway pressure-assisted ventilation. METHODS: A 40-year-old woman with myotonic dystrophy and severe orthopnea, who could not lie supine because of severe orthopnea, and who was a high-risk candidate for general anesthesia, underwent cataract surgery with continuous positive airway pressure ventilation by face mask. RESULTS: The patient underwent uneventful phacoemulsification and intraocular lens implantation in her left eye, while under continuous positive airway pressure ventilation. CONCLUSION: Selected patients who are unable to lie supine for ocular surgery because of severe orthopnea, and who are at risk for systemic complications under general anesthesia, may be evaluated for continuous positive airway pressure-assisted surgery.

Advances in ventilatory support of the pediatric surgical patient.

Severe respiratory failure in newborn and pediatric patients is associated with significant morbidity and mortality. Basic science laboratory investigation has led to advances both in our understanding of ventilator-induced lung injury and in optimizing the supportive use of conventional ventilation strategies. Over the past few years, progress has been made in alternative therapies for ventilating both children and adults with severe respiratory failure. This review focuses on recent laboratory and clinical data detailing the techniques of permissive hypercapnia, high frequency oscillatory ventilation, inhaled nitric oxide, intratracheal pulmonary ventilation, and liquid ventilation. Some of these modalities are becoming commonplace, and others may have much to offer the clinician if their benefit is clearly demonstrated in future clinical trials.

Ventilación de alta frecuencia oscilatoria, un avance en terapia intensiva infantil / Oscillatory high frequency ventilation, an advance in pediatric intensive care

Se revisan los mecanismos del daño pulmonar causado por la ventilación mecánica convencional (VMC) y las recomendaciones para evitarlo. Se analizan otras terapias alternativas en el tratamiento de la insuficiencia respiratoria aguda grave del paciente que no responde a VMC. La ventilación mecánica de alta frecuencia oscilatoria (VAFO) se recomienda como un método útil de terapia en pacientes con síndrome de dificultad respiratoria aguda (SDRA) o bronconeumonía (BRN) grave. Se revisan críticamente los conceptos señalados en la literatura para explicar el intercambio gaseoso en la VAFO y se propone una nueva explicación para este, basada en evidencia experimental y observación clínica. Se concluye que esta técnica ha demostrado utilidad en pacientes con SDRA y BRN grave, que no responden al tratamiento con VMC, resaltando que sólo un pequeño número de pacientes será merecedor de ella. Se refuerza el concepto de que la VMC es la primera opción en todo paciente con insuficiencia respiratoria aguda grave

Partial liquid ventilation reduces pulmonary neutrophil accumulation in an experimental model of systemic endotoxemia and acute lung injury.

OBJECTIVE: To determine whether pulmonary neutrophil sequestration and lung injury are affected by partial liquid ventilation with perfluorocarbon in a model of acute lung injury (ALI). DESIGN: A prospective, controlled, in vivo animal laboratory study. SETTING: An animal research facility of a health sciences university. SUBJECTS: Forty-one New Zealand White rabbits. INTERVENTIONS: Mature New Zealand White rabbits were anesthetized and instrumented with a tracheostomy and vascular catheters. Animals were assigned to receive partial liquid ventilation (PLV, n = 15) with perflubron (18 mL/kg via endotracheal tube), conventional mechanical ventilation (CMV, n = 15) or high-frequency oscillatory ventilation (HFOV, n = 5). Animals were ventilated, using an FIO2 of 1.0, and ventilatory settings were required to achieve a normal PaCO2. Animals were then given 0.9 mg/kg of Escherichia coli endotoxin intravenously over 30 mins. Partial liquid ventilation, conventional mechanical ventilation, or high-frequency oscillatory ventilation was continued for an additional 4 hrs before the animals were killed. A group of animals not challenged with endotoxin underwent conventional ventilation for 4.5 hrs, serving as the control group (control, n = 6). Lungs were removed and samples were frozen at -70 degrees C. Representative samples were stained for histology. A visual count of neutrophils per high-power field (hpf) was performed in five randomly selected fields per sample in a blinded fashion by light microscopy. Lung samples were homogenized in triplicate in phosphate buffer, ultrasonified, freeze-thawed, and clarified by centrifugation. Supernatants were analyzed for myeloperoxidase (MPO) activity by spectrophotometry with o-dianisidine dihydrochloride and hydrogen peroxide at 460 nm. MEASUREMENTS AND MAIN RESULTS: Histologic analysis of lung tissue obtained from control animals showed normal lung architecture. Specimens from the PLV and HFOV groups showed a marked decrease in alveolar proteinaceous fluid, pulmonary vascular congestion, edema, necrotic cell debris, and gross inflammatory infiltration when compared with the CMV group. Light microscopy of lung samples of animals supported with PLV and HFOV had significantly lower neutrophil counts when compared with CMV (PLV, 4 +/- 0.3 neutrophils/hpf; HFOV, 4 +/- 0.5 neutrophils/hpf; CMV, 10 +/- 0.9 neutrophils/hpf; p < .01). In addition, MPO activity from lung extracts of PLV and HFOV animals was significantly lower than that of CMV animals (PLV, 61 +/- 13.3 units of MPO activity/lung/kg; HFOV, 43.3 +/- 6.8 units of MPO activity/lung/kg; CMV, 140 +/- 28.5 units of MPO activity/lung/kg; p < .01). MPO activity from lungs of uninjured control animals was significantly lower than that of animals in the PLV, HFOV, and CMV groups (control, 2.2 +/- 2 units of MPO activity/lung/kg; p < .001). CONCLUSIONS: Partial liquid ventilation decreases pulmonary neutrophil accumulation, as shown by decreased neutrophil counts and MPO activity, in an experimental animal model of ALI induced by systemic endotoxemia. The attenuation in pulmonary leukostasis in animals treated with PLV is equivalent to that obtained by a ventilation strategy that targets lung recruitment, such as HFOV.