The impact of artificial intelligence on retinal disease management: Vision Academy retinal expert consensus

PURPOSE OF REVIEW

The aim of this review is to define the "state-of-the-art" in artificial intelligence (AI)-enabled devices that support the management of retinal conditions and to provide Vision Academy recommendations on the topic.

RECENT FINDINGS

Most of the AI models described in the literature have not been approved for disease management purposes by regulatory authorities. These new technologies are promising as they may be able to provide personalized treatments as well as a personalized risk score for various retinal diseases. However, several issues still need to be addressed, such as the lack of a common regulatory pathway and a lack of clarity regarding the applicability of AI-enabled medical devices in different populations.

SUMMARY

It is likely that current clinical practice will need to change following the application of AI-enabled medical devices. These devices are likely to have an impact on the management of retinal disease. However, a consensus needs to be reached to ensure they are safe and effective for the overall population.

Current status and practical considerations of artificial intelligence use in screening and diagnosing retinal diseases: Vision Academy retinal expert consensus

PURPOSE OF REVIEW

The application of artificial intelligence (AI) technologies in screening and diagnosing retinal diseases may play an important role in telemedicine and has potential to shape modern healthcare ecosystems, including within ophthalmology.

RECENT FINDINGS

In this article, we examine the latest publications relevant to AI in retinal disease and discuss the currently available algorithms. We summarize four key requirements underlining the successful application of AI algorithms in real-world practice: processing massive data; practicability of an AI model in ophthalmology; policy compliance and the regulatory environment; and balancing profit and cost when developing and maintaining AI models.

SUMMARY

The Vision Academy recognizes the advantages and disadvantages of AI-based technologies and gives insightful recommendations for future directions.

Repeated Topical Administration of 3 nm Cerium Oxide Nanoparticles Reverts Disease Atrophic Phenotype and Arrests Neovascular Degeneration in AMD Mouse Models

Increased oxidative stress in the retina and retinal pigment epithelium is implicated in age-related macular degeneration (AMD). Antioxidant cerium oxide nanoparticles (CeO2NPs) have been used to treat degenerative retinal pathologies in animal models, although their delivery route is not ideal for chronic patient treatment. In this work, we prepared a formulation for ocular topical delivery that contains small (3 nm), nonaggregated biocompatible CeO2NPs. In vitro results indicate the biocompatible and protective character of the CeO2NPs, reducing oxidative stress in ARPE19 cells and inhibiting neovascularization related to pathological angiogenesis in both HUVEC and in in vitro models of neovascular growth. In the in vivo experiments, we observed the capacity of CeO2NPs to reach the retina after topical delivery and a subsequent reversion of the altered retinal transcriptome of the retinal degenerative mouse model DKOrd8 toward that of healthy control mice, together with signs of decreased inflammation and arrest of degeneration. Furthermore, CeO2NP eye drops' treatment reduced laser-induced choroidal neovascular lesions in mice by lowering VEGF and increasing PEDF levels. These results indicate that CeO2NP eye drops are a beneficial antioxidant and neuroprotective treatment for both dry and wet forms of AMD disease.

<p>Inter-Ocular Asymmetry in Anterior Corneal Aberrations Using Placido Disk-Based Topography</p>

Objective

Inter-ocular asymmetry in anterior corneal high-order aberrations has previously not been investigated. This study aims to investigate the normal range of inter-ocular asymmetry in corneal high-order aberrations (HOAs) using a Placido disk-based corneal topographer to explore the relationship between the HOA parameters of the anterior corneal for each eye individually and the refractive error.

Patients and Methods

A total of 257 subjects (98 males and 159 females) were participated, with an age range of 6 to 81 years (average of 40.2 ±17.53). Participants were divided into three groups: myopia (spherical equivalent (SEQ) of refraction ≥−0.50 D), hypermetropia (SEQ ≥+0.50 D), and emmetropia. For all patients, high-order aberrations were measured using a corneal topographer (CA.200TM; Topcon). Inter-ocular asymmetry was represented by RMS (root mean square) for three, five, and seven mm as pupil entry; aberrations for five mm pupil (vertical and oblique trefoil, vertical and horizontal comma, and primary spherical aberration) were recorded using the instrument’s built-in software.

Results

Hypermetropes exhibit the highest inter-ocular asymmetry of all RMS values, mostly in spherical aberrations, and higher-order trefoil values. Oblique trefoil aberrations had the highest interocular asymmetry in the myopic groups. The interocular asymmetry in horizontal coma values was the highest in emmetropes and the lowest in hypermetropes.

Conclusion

To our knowledge, this is the first observational study of inter-ocular differences in high-order aberrations of the anterior corneal surface of the human eye. This study’s results could be used to establish normal values of inter-ocular asymmetry of HOAs of the anterior cornea. The use of such normal values should be investigated further to serve as a guideline for clinicians when establishing the best management route for the patient’s refractive error.

Artificial Intelligence for the Detection of Diabetic Retinopathy in Primary Care: Protocol for Algorithm Development

Background

Diabetic retinopathy (DR) is one of the most important causes of blindness worldwide, especially in developed countries. In diabetic patients, periodic examination of the back of the eye using a nonmydriatic camera has been widely demonstrated to be an effective system to control and prevent the onset of DR. Convolutional neural networks have been used to detect DR, achieving very high sensitivities and specificities.

Objective

The objective of this is paper was to develop an artificial intelligence (AI) algorithm for the detection of signs of DR in diabetic patients and to scientifically validate the algorithm to be used as a screening tool in primary care.

Methods

Under this project, 2 studies will be conducted in a concomitant way: (1) Development of an algorithm with AI to detect signs of DR in patients with diabetes and (2) A prospective study comparing the diagnostic capacity of the AI algorithm with respect to the actual system of family physicians evaluating the images. The standard reference to compare with will be a blinded double reading conducted by retina specialists. For the development of the AI algorithm, different iterations and workouts will be performed on the same set of data. Before starting each new workout, the strategy of dividing the set date into 2 groups will be used randomly. A group with 80% of the images will be used during the training (training dataset), and the remaining 20% images will be used to validate the results (validation dataset) of each cycle (epoch). During the prospective study, true-positive, true-negative, false-positive, and false-negative values will be calculated again. From here, we will obtain the resulting confusion matrix and other indicators to measure the performance of the algorithm.

Results

Cession of the images began at the end of 2018. The development of the AI algorithm is calculated to last about 3 to 4 months. Inclusion of patients in the cohort will start in early 2019 and is expected to last 3 to 4 months. Preliminary results are expected to be published by the end of 2019.

Conclusions

The study will allow the development of an algorithm based on AI that can demonstrate an equal or superior performance, and that constitutes a complement or an alternative, to the current screening of DR in diabetic patients.

International Registered Report Identifier (IRRID)

PRR1-10.2196/12539

Prevalence of Vitreoretinal Interface Abnormalities on Spectral-Domain OCT in Healthy Participants over 45 Years of Age

PURPOSE

To assess the prevalence of vitreoretinal interface abnormalities in a general population of healthy adults ≥45 years of age.

DESIGN

Cross-sectional study carried out at 17 ophthalmology services throughout Spain.

PARTICIPANTS

Between September 2015 and March 2016, all consecutive healthy persons aged ≥45 years who were accompanying patients to ophthalmology services were invited to take part in the study. Exclusion criteria were known retinal disease, uveitis, history of ocular trauma or previous intraocular surgery (including cataract surgery and intravitreal injections), severe myopia (>-6 dioptres), and poor ocular media transparency.

METHODS

Spectral-domain OCT or swept-source OCT was performed on all participants. Diseases of the vitreomacular interface were classified according to the OCT-based anatomic classification system of the International Vitreomacular Traction Study Group. All pathologic and borderline images as well as doubtful cases were evaluated blindly in a central reading center.

MAIN OUTCOME MEASURES

Prevalence of vitreomacular interface abnormalities (vitreomacular traction epiretinal membrane, lamellar hole).

RESULTS

The study included 2257 participants with a mean age of 59.5 years (range 45-90), and a total of 4490 eyes (right eyes 2242, left eyes 2248). Vitreoretinal interface abnormalities were detected in 70 eyes, with a prevalence of 1.6%. Vitreomacular adhesion was observed in 1317 eyes (29.3%). Results of spectral-domain OCT or swept-source OCT examination were unrevealing in 3103 eyes. Vitreoretinal interface abnormalities were found in 61 participants, with a prevalence in the study population of 2.7%. Vitreomacular traction was observed in 14 participants (0.6%), epiretinal membrane in 44 (1.9%), and lamellar macular hole in 3 (0.1%). The prevalence of both vitreomacular traction and epiretinal membrane increased significantly with age. The presence of vitreoretinal interface abnormalities was unrelated to concomitant diabetes mellitus or hypertension.

CONCLUSIONS

An important percentage of healthy participants from the general population ≥45 years of age showed vitreoretinal interface abnormalities. Screening with OCT is advisable at any first routine consultation or preoperative assessment, particularly in older participants.

[New perspectives in the approach to age-related macular degeneration]

The approval of aflibercept for the neovascular form of age-related macular degeneration has opened up the possibility of treating patients with fewer injections, since the drug can be administered once every two months. Aflibercept can also be used as rescue therapy in patients with suboptimal response to other antiangiogenic treatments. The present study reviews the scientific evidence on aflibercept, both in treatment-naïve patients and in those with an unsatisfactory response to conventional treatments.

[From scientific evidence to clinical practice: treatment regimens for macular edema secondary to retinal vein occlusion]

Retinal vein occlusion (RVO) is the second most common cause of retinal vascular disease after diabetic retinopathy. Despite the existence of several possible treatment options, none was entirely satisfactory and many patients suffered irreversible visual loss. As a result of the BRAVO, CRUISE and GENEVA trials, ranibizumab and the intravitreal biodegradable implants of dexamethasone has recently been approved by the US Food and Drug Administration and the European Medicines Agency for the treatment of RVO secondary edema. In this paper we begin by describing the current treatment options for RVO associated macular edema and continue with the description of the treatment regimen with ranibizumab.

Vitreous levels of somatostatin in patients with chronic uveitic macular oedema

PURPOSE

Intravitreal somatostatin (SST) levels are decreased in patients with diabetic macular oedema. This deficit may be involved in the pathogenesis of this condition. The aim of the present study was to determine SST concentration in the vitreous fluid of patients with chronic uveitic macular oedema (CUMO) and quiescent intraocular inflammation.

METHODS

Plasma and vitreous fluid samples were obtained during vitrectomy from 11 eyes of patients with CUMO and from 42 eyes of control subjects (idiopathic epiretinal membrane, macular hole). SST concentration was measured by radioimmunoassay.

STATISTICS

χ(2)-square test, Mann-Whitney U-test, Wilcoxon test, Spearman's rank correlation coefficient, and multivariant linear regression models.

RESULTS

Plasma SST concentrations were similar in uveitic patients and controls (28.25 pg/ml (21.3-31) vs 28.7 pg/ml (22-29.5); P=0.869). A higher vitreous concentration of proteins was found in uveitic patients (1.59±0.38 mg/ml vs 0.73±0.32 mg/ml, P<0.0001). Vitreous SST was markedly lower in uveitic patients, both in absolute terms and after adjusting for total intravitreous protein concentration (39.37 pg/ml (6.16-172) vs 486.73 pg/ml (4.7-1833), P<0.0001; 33.1 pg/mg (3.9-215.74) vs 629.75 pg/mg (6.91-2024), P<0.0001). No correlations were found between plasma and vitreous concentration of SST in either group (ρ=0.191, P=0.57 and ρ=0.49, P=0.66). There were no correlations between vitreous SST concentration and visual acuity or macular thickness in uveitic patients (ρ=0.302, P=0.31 and ρ=0.45, P=0.13).

CONCLUSIONS

Intravitreous SST is decreased in patients with CUMO and quiescent intraocular inflammation. The deficit of SST may have a role in the pathogenesis of this condition.

Bilateral anterior ischemic optic neuropathy in patients on dialysis: A report of two cases

Patients under chronic dialysis treatment suffer from atherosclerotic disease and anemia more frequently than the normal population. This, together with the frequent hypotension, put these patients at increased risk for anterior ischemic optic neuropathy (AION), which may be bilateral and blinding. We present two cases of patients under chronic dialysis who developed bilateral AION after hypotensive events. Bilateral involvement is not unusual in renal replacement patients who suffer from AION. Efforts should be focused on prevention of this complication by improving anemia and blood pressure control because once established, treatment will probably be ineffective.

Effect of intensive insulin therapy on macular biometrics, plasma VEGF and its soluble receptor in newly diagnosed diabetic patients

BACKGROUND

To evaluate whether intensive insulin therapy leads to changes in macular biometrics (volume and thickness) in newly diagnosed diabetic patients with acute hyperglycaemia and its relationship with serum levels of vascular endothelial growth factor (VEGF) and its soluble receptor (sFlt-1).

METHODS

Twenty-six newly diagnosed diabetic patients admitted to our hospital to initiate intensive insulin treatment were prospectively recruited. Examinations were performed on admission (day 1) and during follow-up (days 3, 10 and 21) and included a questionnaire regarding the presence of blurred vision, standardized refraction measurements and optical coherence tomography. Plasma VEGF and sFlt-1 were assessed by ELISA at baseline and during follow-up.

RESULTS

At study entry seven patients (26.9%) complained of blurred vision and five (19.2%) developed burred vision during follow-up. Macular volume and thickness increased significantly (p = 0.008 and p = 0.04, respectively) in the group with blurred vision at day 3 and returned to the baseline value at 10 days. This pattern was present in 18 out of the 24 eyes from patients with blurred vision. By contrast, macular biometrics remained unchanged in the group without blurred vision. We did not detect any significant changes in VEGF levels during follow-up. By contrast, a significant reduction of sFlt-1 was observed in those patients with blurred vision at day 3 (p = 0.03) with normalization by day 10.

CONCLUSION

Diabetic patients with blurred vision after starting insulin therapy present a significant transient increase in macular biometrics which is associated with a decrease in circulating sFlt-1.

Vitreous levels of interleukine-8 and monocyte chemoattractant protein-1 in macular oedema with branch retinal vein occlusion

PURPOSE

To investigate whether interleukine-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1) are related with macular oedema in patients with branch retinal vein occlusions (BRVOs).

DESIGN

Retrospective case-control study.

PARTICIPANTS

Nineteen patients who had macular oedema due to BRVO and nine patients with non-ischaemic ocular diseases (control group).

METHODS

Macular oedema was examined by optical coherence tomography. Both venous blood and vitreous samples were obtained at the time of vitreoretinal surgery. IL-8 and MCP-1 levels in vitreous fluid and plasma were determined with enzyme-linked immunosorbent assay kits. Variables were compared with the Mann-Whitney U-test, Wilcoxon's signed-ranked test, and the chi2-test, when appropriate. To examine correlations, Spearman's rank-order correlation coefficients were calculated. Statistical significance was set at P<0.05.

RESULTS

The vitreous fluid levels of IL-8 (median: 63.5 pg/ml) and MCP-1 (median: 1522.4 pg/ml) were significantly higher in the patients with BRVO than in the control group (median: 5.1 and 746.5 pg/ml respectively; P<0.001 and <0.001 respectively). Vitreous IL-8 and MCP-1 were significantly correlated in patients with BRVO (P=0.009).

CONCLUSIONS

Both IL-8 and MCP-1 were elevated in the vitreous fluid of patients with BRVO and macular oedema. Both chemokines may contribute to the pathogenesis of macular oedema in patients with BRVO.

Distinct cholesterol and phospholipid incorporation at the platelet plasma membrane of hyperlipidemic subjects: structural order and function

Plasma lipid composition, platelet aggregation, cholesterol (Ch)/glycoprotein IIb-IIIa (GP) and phospholipid (Ph)/GP molar ratios, fatty acid composition and structural order (1, 6-diphenyl-1, 3, 5-hexatriene (DPH) fluorescence anisotropy at 35 degrees C (r(DPH,35)) of human platelet plasma membranes (HPPM) were measured in four DPH,35 groups of hyperlipidemic patients (II: plasma Ch < 250 mg/dl and TG (triglycerides) <220 mg/dl, n = 21; III: Ch > 250 mg/dl and TG < 220 mg/dl, n = 23; IV: Ch < 250 mg/dl and TG > 220 mg/dl, n = 18; and V: Ch > 250 mg/dl and TG > 220 mg/dl, n = 12) and compared with those of the control group (I). Our results were: (i) in groups III, IV and V the HPPM (Ch + Ph)/GP molar ratio increased 7.0+/-7.7% (mean SD); (ii) the Ph/GP molar ratio increased significantly in groups III, IV and V, but most in IV and V, while the Ch/GP molar ratio increased only in groups III and V; (iii) the mean relative increase of Ch with respect to Ph in the HPPM of groups III, IV and V was 140% 21% and 54%, respectively; (iv) the Ch/GP molar ratio was correlated with LDL-Ch (0.41+/-0.16, P < 0.002, n = 55, for all the subjects and 0.60+/-0.11, P < 2.10(-4), n = 33, for subjects with TG < 220 mg/dl), however, it was totally uncorrelated with HDL-Ch; (v) the HPPM Ch/Ph molar ratio was positively correlated with plasma Ch (r = 0.51+/-0.08, P < 1.10(-6), n = 83) and with (LDL + HDL) Ch (r = 0.64+/-0.07, P < 1.10(-6), n = 73), the former correlation increased significantly ( r = 0.67+/-0.07, P < 1.10(-6), n = 53) when done only for subjects with TG < 220 mg/dl; (vi) the Ch/Ph molar ratio was only increased in group III (0.70+/-0.03, P < 3.10(-5), n = 23) and decreased in group IV (0.62+/-0.02, P < 0.001, n = 18); (vii) the fatty acid/GP molar ratio was significantly increased in groups IV and V, however, a significant absolute and relative increase of C16:0 and C18:1 was observed only in severe hypertriglyceridemia (> 500 mg/dl), together with a relative decrease of C18:0 and C20:4 ( n - 6); (viii) the HPPM structural order, as probed by r(DPH,35), was negatively correlated with DPH,35 plasma TG (r =- 0.61+/-0.10, P < 4.10(-5), n = 39), the Ph/GP molar ratio (r =-0.58+/-0.10, P < 2.10(-4), n = 39) and the the (C18:1 + C18:2))/GP molar ratio (r =- 0.80+/-0.05, P < 1.10(-6), n = 39), however, it was independent of plasma and HPPM Ch; (ix) the higher HPPM Ch/Ph molar ratio in group III was associated (r = 0.58+/-0.12, P < 0.005, n = 22) with a moderately higher platelet reactivity to collagen. We conclude that Ch and Ph were distinctly incorporated to HPPM in the different groups of hyperlipidemia and, therefore, that the absolute increase of Ch and Ph was more informative to understand the structural and functional modifications of the HPPM in hyperlipidemias, than the Ch/Ph molar ratio. On the other hand, the r was sensitive to the DPH,35 increase in the content of HPPM Ph and C18:1 + C18:2 and it was insensitive to the increase in the Ch content.

Topical anesthesia: Possible risk factor for endophthalmitis after cataract extraction

PURPOSE

To assess the relationship between the risk for acute endophthalmitis after cataract extraction and whether certain factors, such as surgeon qualification, numerical order, duration of surgery, operating theater, and type of anesthesia (topical or retrobulbar), could be modified to decrease the risk.

SETTING

Single-center academic practice.

METHODS

Two epidemiological studies were performed: a case-control study and a retrospective cohort study. The surgical records of all patients with clinically diagnosed endophthalmitis within 30 days after cataract surgery performed between February 2002 and September 2003 were reviewed. The endophthalmitis cases were compared with 108 randomly selected controls (4 controls per case). The global incidence of endophthalmitis and the incidence according to type of anesthesia were calculated.

RESULTS

Of 5011 cataract extractions performed, 27 cases of endophthalmitis occurred. The incidence was 5.39 per 1000 procedures. An independent statistically significant relationship was found between endophthalmitis and the use of topical anesthesia (odds ratio [OR], 11.8; 95% confidence interval [CI], 2.4-58.7) and surgery longer than 45 minutes (OR, 7.2; 95% CI, 1.7-29.7) but not between the other variables. The incidence of endophthalmitis was 1.8 per 1000 cataract extractions with retrobulbar anesthesia and 6.76 per 1000 with topical anesthesia (relative risk [RR], 3.76; 95% CI, 0.89-15.85). After the start of the study period was extended to May 2001, the incidence of endophthalmitis was 1.3 per 1000 cataract extractions with retrobulbar anesthesia and 8.7 per 1000 with topical anesthesia (RR, 6.72; 95% CI, 1.63-27.63).

CONCLUSION

Results suggest that there may be an association between topical anesthesia and endophthalmitis after cataract extraction.

Pars plana vitrectomy, laser retinopexy, and aqueous tamponade for pseudophakic rhegmatogenous retinal detachment

OBJECTIVE

To evaluate a novel pars plana vitrectomy (PPV) approach with aqueous tamponade for repair of primary pseudophakic rhegmatogenous retinal detachment (RRD).

DESIGN

Prospective, noncomparative, interventional case series.

PARTICIPANTS

Sixty nonconsecutive patients (60 eyes) with primary pseudophakic RRD.

INTERVENTION

Patients underwent PPV alone with injection of perfluoro-n-octane followed by fluid-air exchange and transscleral diode laser retinopexy and then balanced salt solution (BSS) tamponade. All patients were observed for at least 1 year.

MAIN OUTCOME MEASURES

Anatomic outcome, visual acuity (VA), and complications.

RESULTS

The mean follow-up period was 16.4 months (range, 12.1-21.5). Preoperatively, 32 patients (53.3%) had 1 break and 28 patients (46.7%) had 2 to 4 breaks (mean, 2.7). Intraoperatively, 108 retinal breaks were identified, 82 (75.9%) superior and 26 (24%) inferior. Eight breaks in 8 patients that were not seen preoperatively or intraoperatively were diagnosed after air-BSS exchange. Mean preoperative best-corrected VA (BCVA) was 20/700 (range, hand movements [HM]-20/20). Final BCVA was a mean of 20/59 (range, 20/200-20/20). For the 13 eyes with macula-attached RRD, BCVA was the same preoperatively and postoperatively (mean, 20/27; range, 20/50-20/20). For the 47 eyes with macula-detached RRD, the mean BCVA was 20/888 preoperatively (range, HM-20/50) and 20/68 postoperatively (range, 20/200-20/20). Final VA was > or =20/40 in 34 of 60 eyes (56.6%). Primary retinal reattachment (attachment at 1 month postoperatively) was attained in 59 of the 60 patients (98.3%). The single failure was due to a new break postoperatively; this break was treated by pneumatic retinopexy and photocoagulation of the break. At the 12-month follow-up visit, reattachment had been attained in all 60 eyes (100%). Postoperatively, 1 patient (1.6%) had hypotony at the 1-day postoperative visit, but intraocular pressure was 14 mm at the 4-day visit, and 2 patients (3.3%) had mild vitreous hemorrhage during the first 48 hours that resolved spontaneously during the following 10 days.

CONCLUSION

Pars plana vitrectomy with laser retinopexy followed by BSS tamponade is effective for intraoperative sealing of retinal breaks causing pseudophakic RRD. We did not identify safety concerns in this 60-patient series.

[Endotracheal aspiration: respirator vs. manual resuscitation as method for hyperoxygenation and hyperinflation]

Endotracheal aspiration protocols (EAT) include hyperoxygenation and hyperinflation to minimize the negative effects of the technique. No conclusive studies have determined the most effective hyperoxygenation and hyperinflation method. This study had two aims: to compare the effects on patient oxygenation and hemodynamics during endotracheal aspiration of secretions using, respectively, a respirator or manual resuscitator as the hyperoxygenation and hyperinflation method. Tidal volume (TV) and FIO2 with the manual resuscitator were quantified. The study was based on 172 aspiration sessions carried out under artificial ventilation in the immediate postoperative period of 26 patients who had undergone cardiac surgery without lung damage. Hyperinflation and hyperoxygenation before, during and after aspiration were carried out with and artificial ventilator in group I and with a manual resuscitator in group II. In all aspiration interventions, an analysis was made of hemodynamic parameters (MAP, MPAP, HR, CO and arrhythmias), ventilation and oxygenation parameters (HR, FIO2, SpO2, and SvO2), and the influence of the method on the appearance of atelectasis. Both methods produced small increases in all hemodynamic parameters, and significant differences in HR (p < 0.001) and MPAP (p < 0.002), although no clinical repercussions were observed. No severe arrhythmias were observed. No statistically significant differences between the two methods were found in the evolution of SpO2 and SvO2, which remained above baseline levels throughout both procedures. Analysis of the effectiveness of the manual resuscitator (the second aim) under the conditions established yielded a mean FIO2 of 0.86 and a mean tidal volume of 153% in relation to baseline tidal volume. Both methods of hyperoxygenation and hyperinflation prevent hypoxia and maintain hemodynamic stability in patients without producing lung damage. The effectiveness of the manual resuscitator for administering high oxygen concentration and large volumes was confirmed.

[Endotracheal suctioning of secretions: effects of instillation of normal serum]

Normal saline (NS) instillations in the trachea during the technique of endotracheal suctioning is an habitual practice although there is still some controversy about the benefits and harmful effects caused by this practice. This study was carried out with the objective to compare the effects of instillation or no instillation of NS during the aspiration technique on the oxygenation, amount of secretion obtained, and hemodynamical and ventilatory parameters. We studied 176 en dotracheal aspirations recorded in the post-operatory of 25 patients without previous pulmonary disease who underwent heart surgery. The aspiration was performed every two hours, according to the protocol of the study. Each patient was its own case and control, so the same patient was aspired altern actively; with and without NS instillation alternatively. Hemodynamical parameters (arterial blood pressure, heart rate), ventilatory parameters (fidal volume, peak inspiratory pressure, respiratory rate) and oxygenation parameters (PaO2, SaO2, SpO2) were analysed in all the samples. The amount of secretion obtained with both techniques was evaluated using weight calculus and total proteins. When analysing the results, we observed that the technique of en dotracheal aspiration causes increases of the Average Arterial Pressure; when NS is used in the aspiration there is a statistically significant decrease of PaO2. In the evaluation of the amount of secretions we obtained similar amounts with both techniques. Taking all this into account we recommend the elimination of systematical instillation of physiological serum from the protocols of endotracheal aspiration during this technique.

International study of asthma and allergies in childhood. Results of the first phase of the I.S.A.A.C. project in Pamplona, Spain

The international study of asthma and allergy in childhood was designed for the epidemiological investigation of asthma, by means of a standardized methodology. It was started in 1989, as a consequence of very different results obtained in previous epidemiological studies, of which none could be considered as definitive. First, a standardized survey was performed, in order to determine the prevalence of asthma in the United Kingdom, New Zealand and Australia, and subsequently several countries joined them, Spain being one of them. The first objective was to discover the prevalence and severity of bronchial asthma in children who lived in different countries, and to compare the results. Also, it was intended to obtain baseline measurements, in order to assess future trends in asthma prevalence and severity, and to facilitate a base for a subsequent phase of etiologic investigation. For this study, following a protocol previously established, a written survey and a video-survey were given to children aged 13 and 14, and a written survey to the parents of the children aged 6 and 7. All the surveys were performed during the school year 1993-1994. A total of 8,087 surveys were conducted in 53 schools from Pamplona and neighbouring towns. Among the group of children aged 13 and 14, 5.3% had a crisis in the study period, whereas 4.4% suffered from an acute attack. This prevalence was not as high in children aged 6 and 7, for whom the percentages were 3.3% and 3.2%, respectively. We found lower prevalences in the two groups in relation to other countries, and we attribute this result, on one hand to the accessibility to doctors in our area, and on the other hand, to early diagnosis of the disease by specialists, periodic control and suitable etiologic treatment.