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Background & Aims: Pre-emptive transjugular intrahepatic portosystemic shunt (TIPS) is the treatment of choice for high-risk acute variceal bleeding (AVB; i.e., Child-Turcotte-Pugh [CTP] B8-9+active bleeding/C10-13). Nevertheless, some 'non-high-risk' patients have poor outcomes despite the combination of non-selective beta-blockers and endoscopic variceal ligation for secondary prophylaxis. We investigated prognostic factors for re-bleeding and mortality in 'non-high-risk' AVB to identify subgroups who may benefit from more potent treatments (i.e., TIPS) to prevent further decompensation and mortality., Methods: A total of 2,225 adults with cirrhosis and variceal bleeding were prospectively recruited at 34 centres between 2011-2015; for the purpose of this study, case definitions and information on prognostic indicators at index AVB and on day 5 were further refined in low-risk patients, of whom 581 (without failure to control bleeding or contraindications to TIPS) who were managed by non-selective beta-blockers/endoscopic variceal ligation, were finally included. Patients were followed for 1 year., Results: Overall, 90 patients (15%) re-bled and 70 (12%) patients died during follow-up. Using clinical routine data, no meaningful predictors of re-bleeding were identified. However, re-bleeding (included as a time-dependent co-variable) increased mortality, even after accounting for differences in patient characteristics (adjusted cause-specific hazard ratio: 2.57; 95% CI 1.43-4.62; p = 0.002). A nomogram including CTP, creatinine, and sodium measured at baseline accurately (concordance: 0.752) stratified the risk of death., Conclusion: The majority of 'non-high-risk' patients with AVB have an excellent prognosis, if treated according to current recommendations. However, about one-fifth of patients, i.e. those with CTP ≥8 and/or high creatinine levels or hyponatremia, have a considerable risk of death within 1 year of the index bleed. Future clinical trials should investigate whether elective TIPS placement reduces mortality in these patients., Impact and Implications: Pre-emptive transjugular intrahepatic portosystemic shunt placement improves outcomes in high-risk acute variceal bleeding; nevertheless, some 'non-high-risk' patients have poor outcomes despite the combination of non-selective beta-blockers and endoscopic variceal ligation. This is the first large-scale study investigating prognostic factors for re-bleeding and mortality in 'non-high-risk' acute variceal bleeding. While no clinically meaningful predictors were identified for re-bleeding, we developed a nomogram integrating baseline Child-Turcotte-Pugh score, creatinine, and sodium to stratify mortality risk. Our study paves the way for future clinical trials evaluating whether elective transjugular intrahepatic portosystemic shunt placement improves outcomes in presumably 'non-high-risk' patients who are identified as being at increased risk of death., (Copyright © 2023 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.)

Microbial eukaryotes (or protists) in marine ecosystems are a link between primary producers and all higher trophic levels, and the rate at which heterotrophic protistan grazers consume microbial prey is a key mechanism for carbon transport and recycling in microbial food webs. At deep-sea hydrothermal vents, chemosynthetic bacteria and archaea form the base of a food web that functions in the absence of sunlight, but the role of protistan grazers in these highly productive ecosystems is largely unexplored. Here, we pair grazing experiments with a molecular survey to quantify protistan grazing and to characterize the composition of vent-associated protists in low-temperature diffuse venting fluids from Gorda Ridge in the northeast Pacific Ocean. Results reveal protists exert higher predation pressure at vents compared to the surrounding deep seawater environment and may account for consuming 28 to 62% of the daily stock of prokaryotic biomass within discharging hydrothermal vent fluids. The vent-associated protistan community was more species rich relative to the background deep sea, and patterns in the distribution and co-occurrence of vent microbes provide additional insights into potential predator-prey interactions. Ciliates, followed by dinoflagellates, Syndiniales, rhizaria, and stramenopiles, dominated the vent protistan community and included bacterivorous species, species known to host symbionts, and parasites. Our findings provide an estimate of protistan grazing pressure within hydrothermal vent food webs, highlighting the important role that diverse protistan communities play in deep-sea carbon cycling., Competing Interests: The authors declare no competing interest.

Objectives: The aim of this study was to quantitate patient-specific mitral valve (MV) strain in normal valves and in patients with mitral valve prolapse with and without significant mitral regurgitation (MR) and assess the determinants of MV strain., Background: Few data exist on MV deformation during systole in humans. Three-dimensional echocardiography allows for dynamic MV imaging, enabling digital modeling of MV function in health and disease., Methods: Three-dimensional transesophageal echocardiography was performed in 82 patients, 32 with normal MV and 50 with mitral valve prolapse (MVP): 12 with mild mitral regurgitation or less (MVP - MR) and 38 with moderate MR or greater (MVP + MR). Three-dimensional MV models were generated, and the peak systolic strain of MV leaflets was computed on proprietary software., Results: Left ventricular ejection fraction was normal in all groups. MV annular dimensions were largest in MVP + MR (annular area: 13.8 ± 0.7 cm 2 ) and comparable in MVP - MR (10.6 ± 1 cm 2 ) and normal valves (10.5 ± 0.3 cm 2 ; analysis of variance: p < 0.001). Similarly, MV leaflet areas were largest in MVP + MR, particularly the posterior leaflet (8.7 ± 0.5 cm 2 ); intermediate in MVP - MR (6.5 ± 0.7 cm 2 ); and smallest in normal valves (5.5 ± 0.2 cm 2 ; p < 0.0001). Strain was overall highest in MVP + MR and lowest in normal valves. Patients with MVP - MR had intermediate strain values that were higher than normal valves in the posterior leaflet (p = 0.001). On multivariable analysis, after adjustment for clinical and MV geometric parameters, leaflet thickness was the only parameter that was retained as being significantly correlated with mean MV strain (r = 0.34; p = 0.008)., Conclusions: MVs that exhibit prolapse have higher strain compared to normal valves, particularly in the posterior leaflet. Although higher strain is observed with worsening MR and larger valves and annuli, mitral valve leaflet thickness-and, thus, underlying MV pathology-is the most significant independent determinant of valve deformation. Future studies are needed to assess the impact of MV strain determination on clinical outcome., Competing Interests: Funding Support and Author Disclosures Supported by the Elkins Family Distinguished Chair in cardiac health and the John and Maryanne McCormack Cardiology Fund. The authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2021 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: The aim of this study was to assess mitral valve (MV) remodeling and strain in patients with secondary mitral regurgitation (SMR) compared with primary MR (PMR) and normal valves., Background: A paucity of data exists on MV strain during the cardiac cycle in humans. Real-time 3-dimensional (3D) echocardiography allows for dynamic MV imaging, enabling computerized modeling of MV function in normal and disease states., Methods: Three-dimensional transesophageal echocardiography (TEE) was performed in a total of 106 subjects: 36 with SMR, 38 with PMR, and 32 with normal valves; MR severity was at least moderate in both MR groups. Valve geometric parameters were quantitated and patient-specific 3D MV models generated in systole using a dedicated software. Global and regional peak systolic MV strain was computed using a proprietary software., Results: MV annular area was larger in both the SMR and PMR groups (12.7 ± 0.7 and 13.3 ± 0.7 cm 2 , respectively) compared with normal subjects (9.9 ± 0.3 cm 2 ; p < 0.05). The leaflets also had significant remodeling, with total MV leaflet area larger in both SMR (16.2 ± 0.9 cm 2 ) and PMR (15.6 ± 0.8 cm 2 ) versus normal subjects (11.6 ± 0.4 cm 2 ). Leaflets in SMR were thicker than those in normal subjects but slightly less than those with PMR posteriorly. Posterior leaflet strain was significantly higher than anterior leaflet strain in all 3 groups. Despite MV remodeling, strain in SMR (8.8 ± 0.3%) was overall similar to normal subjects (8.5 ± 0.2%), and both were lower than in PMR (12 ± 0.4%; p < 0.0001). Valve thickness, severity of MR, and primary etiology of MR were correlates of strain, with leaflet thickness being the multivariable parameter significantly associated with MV strain. In patients with less severe MR, anterior leaflet strain in SMR was lower than normal, whereas strain in PMR remained higher than normal., Conclusions: The MV in secondary MR remodels significantly and similarly to PMR with a resultant larger annular area, leaflet surface area, and leaflet thickness compared with that of normal subjects. Despite these changes, MV strain remains close to or in some instances lower than normal and is significantly lower than that of PMR. Strain determination has the potential to improve characterization of MV mechano-biologic properties in humans and to evaluate its prognostic impact in patients with MR, with or without valve interventions., Competing Interests: Funding Support and Author Disclosures This study was supported by the Elkins Family distinguished Chair in cardiac health, and the John and Maryanne McCormack Cardiology Fund. The authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2021 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Background: Low-income parents often seek help from pediatricians for early childhood social-emotional problems but seldom follow through with referrals to behavioral health services., Objective: We sought to understand low-income parents' experiences seeking help from pediatricians for social-emotional problems and how those experiences influenced decisions about accessing behavioral health services., Methods: We conducted 20 semi-structured interviews with low-income parents with concerns about their children's behavior or emotions. Participants were asked about experiences seeking help from pediatricians and decision-making about accessing behavioral health services., Results: Three themes emerged: (1) Participants described reluctance to recognize social-emotional problems, which was often reinforced by doctors' reassurance. (2) Participants reported pediatricians did not meet their expectations about testing, providing explanations/advice, or addressing behavior on-site. (3) Participants had unclear expectations of behavioral health services., Conclusions: Primary care mechanisms that reliably educate parents about behavioral trajectories and the role of behavioral health providers may improve follow-up rates.

The American Academy of Pediatrics recommends that pediatricians promote early childhood education (ECE). However, pediatricians have met resistance from low-income parents when providing anticipatory guidance on some topics outside the realm of physical health. Parents' views on discussing ECE with the pediatrician have not been studied. We sought to understand low-income parents' experiences and attitudes with regard to discussing ECE with the pediatrician and to identify opportunities for pediatrician input. We conducted 27 in-depth, semi-structured, qualitative interviews with parents of 3- and 4-year-old patients (100% Medicaid, 78% African American) at an urban primary care center. Interviews were audio-recorded, transcribed verbatim, and reviewed for themes by a multidisciplinary team. Most low-income parents in our study reported they primarily sought ECE advice from family and friends but were open to talking about ECE with the pediatrician. They considered their children's individual behavior and development to be important factors in ECE decisions and appreciated pediatricians' advice about developmental readiness for ECE. Participants' decisions about ECE were often driven by fears that their children would be abused or neglected. Many viewed 3 years as the age at which children had sufficient language skills to report mistreatment and could be safely enrolled in ECE. Participants were generally accepting of discussions about ECE during well child visits. There may be opportunity for the pediatrician to frame ECE discussions in the context of development, behavior, and safety and to promote high-quality ECE at an earlier age.

Background: Identification of mitral regurgitation (MR) mechanism and pathology are crucial for surgical repair. The aim of the present investigation was to evaluate the comparative accuracy of real-time three-dimensional (3D) transesophageal echocardiography (TEE) and transthoracic echocardiography (TTE) with two-dimensional (2D) TEE and TTE in diagnosing the mechanism of MR compared with the surgical standard., Methods: Forty patients referred for surgical mitral valve repair were studied; 2D and 3D echocardiography with both TTE and TEE were performed preoperatively. Two independent observers reviewed the studies for MR pathology, functional or organic. In organic disease, the presence and localization of leaflet prolapse and/or flail were noted. Surgical findings served as the gold standard., Results: There was 100% agreement in identifying functional versus organic MR among all four modalities. Overall, 2D TTE, 2D TEE, and 3D TEE performed similarly in identifying a prolapse or a flail leaflet; 3D TEE had the best agreement in identifying anterior leaflet prolapse, and it also showed an advantage for segmental analysis. Three-dimensional TTE was less sensitive and less accurate in identifying flail segments., Conclusion: All modalities were equally reliable in identifying functional MR. Both 2D TEE and 3D TEE were comparable in diagnosing MR mechanism, while 3D TEE had the advantage of better localizing the disease. With current technology, 3D TTE was the least reliable in identifying valve pathology.

Background: The most often used functional classification for categorizing the degree of cardiac disability in patients with chronic left ventricular failure is the NYHAN/WHO system. In Idiopathic Pulmonary Arterial Hypertension [I-PAH], this system although used, has not been studied in detail regarding pulmonary hemodynamic parameters association and for long-term prognosis in each of the NYHA/WHO classes., Methods: We retrospectively, studied the NYHA/ WHO system in 83 I-PAH patients. Patients were separated according to the response in the acute vasodilator trial in responders [n = 30] and nonresponders [n = 53]., Results: Classes I - II did not represent the minority population for I-PAH patients [58/83 = 60%]. Only mean right atrial pressure [mRAP] and mean pulmonary artery pressure [mPAP] were different among the NYHA/WHO functional classes [p < 0.000 and p <0.012; respectively]. I-PAH patients class I have the probability to be a responder 12.6 times more [CI 95.%: 4.59-40.62; p < 0.000]. The long-term mortality for class I patients was 0.%, for class II: 2.%, for class III: 28.% and for class IV: 63.% [p < 0.0001]. The follow-up change for one grade class of the NYHA/WHO classes at four years was noticed only in 20.% of the I-PAH patients., Conclusions: NYHA/WHO classes I-II did not represent the minority of I-PAH patients population as has been previously considered. Only mRAP and mPAP were different among the NYHA/WHO classes. The NYHA/ WHO system on the basis of mRAP and mPAP allows to separate classes I-II from III-IV. I-PAH patients class I have 12.6 times more the probability to be a responder and better long-term survival; irrespective of the treatment the prognosis seems to be excellent for this functional class group patients.

The term pulmonary vascular resistance [PVR] describes, in part, the forces opposing the flow across the pulmonary vascular bed. The equation traditionally used is based on the assumption that the pulmonary capillaries, as well as some others vessels in series behave like a Poiseuille resistance. This assumption implies a laminar type of flow of a homogeneous Newtonian fluid, however blood is not a Newtonian fluid and flow is pulsatile in the pulmonary circulation. Neglecting these factors [which only slightly undermines the application of the equation] and others as well [like distension and recruitment of the vessels], will, however, not give us a true clinically practical solution for the calculation of PVR, because the concept of the equation is only true or partially true for part of the pulmonary circulation. In other parts of the lung, flow depends mainly on the behaviour of capillaries as a Starling resistor. If we considered always pulmonary venous pressure [measured clinically as left atrial pressure or pulmonary wedge pressure] as the effective downstream pressure for the calculation of PVR and we ignore or disregard the existence of a significant "critical closing pressure" [whatever the cause] in the lung it will lead to additional erroneous concept regarding PVR calculations and, in addition for the real hemodynamic conditions of the pulmonary vascular bed. Because, at least two different models of perfusion exist in the lung it is inadmissible from a theoretical point of view to calculate PVR, based on only in one of these models. According to the present knowledge of the pulmonary circulation hemodynamics, an improved definition for the PVR could be obtained: 1. by a multipoint pulmonary vascular pressure/flow plot at high flows and 2. with the use of the pulmonary artery occlusion pressure [PAOP] in addition to the determination of the pulmonary wedge pressure technique [PWP], in order to establish the estimated downstream pressure of the pulmonary circulation at zero flow. Therefore, pulmonary hemodynamic determinations of the PVR are better defined with the analysis of the pressure-flow relationships in addition to the information derived from the PAOP/PWP measurements. However, if none of the previous pressure-flow relationships [in order to obtain the slope = PVR at high flows] or the effective downstream pressure measurements [in order to estimate the critical closing pressure at zero flow] are applied for the analysis of the pulmonary circulation, a cautious interpretation of the measured variables [mean pulmonary artery pressure and cardiac output] is preferable to wrong conclusions made from a meaningless variable, the "calculated PVR".

The heart is a muscular mechanical pump with an ability to generate both flow [cardiac output] and pressure in the systemic circulation as well in the pulmonary vascular bed. The product of flow output and systemic arterial pressure is the rate of useful work done, or cardiac power output [CP], therefore for the right ventricle and the pulmonary arterial vascular bed it will be: the product of flow output and mean pulmonary arterial pressure will be the rate of useful work done, or cardiac pulmonary power output [CPP]. Cardiac pulmonary pumping reserve capability can be defined as the maximal cardiac pulmonary power output [CPP] achieved by the right heart during maximal stimulation. Therefore, CPP reserve is the increase in power output as the cardiac performance is increased from the resting to the maximally stimulated state. Recently, several studies have shown that CP is a direct indicator of overall cardiac function, as well is an indicator of exercise capacity and a powerful predictor of prognosis for patients with severe heart failure and ischemic cardiogenic shock. On this basis: 1. we decided to investigate the possible previously mentioned roles of the CP and CPP in patients with different degrees of pulmonary arterial hypertension [n = 137], but mainly in those with primary pulmonary arterial hypertension [PPH]. PPH patients [n = 50], as well as those with Eisenmenger's syndrome [n = 10] were found to have most abnormal resting CPP Indexes [I], [0.431 +/- 0.171, 0.607 +/- 0.124 watts/m2, respectively]. During exercise in PPH patients [n = 14], both CPI and CPPI reserves although they increase, were also found to be significantly diminished [CPI: from 0.546 +/- 170 to 1,116 +/- 0.275 watts/m2, p < 0.05], [CPPI: from 0.373 +/- 0.156 to 0.837 +/- 0.226 watts/m2, p < 0.05]. 2. We also found, significant differences in resting CPPI between PPH responders and no responders patients to hydralazine [0.273 +/- 0.04, 0.507 +/- 0.142 watts/m2, respectively, p < 0.01]. During exercise and under the influence of hydralazine, CPPI "reserve" was significantly diminished in those patients considered as not responders [0.507 +/- 0.142 to 0.723 +/- 0.232 watts/m2, p = ns] when compared with responders to the vasodilator therapy [0.273 +/- 0.04 to 0.903 +/- 0.057 watts/m2, p < 0.01]. On the basis of these initial findings on CPPI in PPH patients, we think that the values of this parameter should be investigated as an index for classifying the severity of this arterial vascular disease, for selecting patients as responders or not to vasodilator therapy, and in the future, to explore the possibility of is usefulness as a prognostic predictor index of mortality in a large population of patients with PPH.

A revision of the pathophysiology clinical classification and treatment of the right ventricular infarction (RVI) is presented. For many years it was believed that right ventricular (RV) contraction was neither important nor crucial to the maintenance of systemic circulation. Although non-invasive studies have reported RV dilation and RV wall motion abnormalities in 50% of patients with inferior--posterior--left ventricular myocardial infarction, RV involvement leads to significant hemodynamic compromise in less than half of such cases. When RVI patients are identified, they should be classified in those without RV failure (Class A), those with RV failure (Class B) and those with shock (Class C). Concerning the role of reperfusion therapies, both therapies (TT or PCI) seem beneficial, because a trend in the reduction of mortality has been observed. A decrease in RV failure was noted in class B patients, and PCI appears to be the procedure of choice in class C patients, since it significantly reduced mortality.

Objective: The purpose of this study was to determine the prevalence of nosocomial infections, associated risk factors, microbiology, use of antibiotics, and associated mortality among hospitalized children., Material and Methods: A 1-day prevalence survey was conducted among 1,183 children hospitalized in a nationwide network of 21 public hospitals caring for children. To attain consistency between hospitals, CDC nosocomial infection definitions were used. Adjusted relative odds of bacteremia were estimated using logistic regression analysis., Results: The prevalence of nosocomial acquired infection was 9.8% (CI 95%, 8.1-11.6). The more prevalent infections were pneumonia (25%), sepsis/bacteremia (19%), and urinary tract infection (5%). The main microorganism isolated in blood cultures drown from patients with nosocomial infection was K. pneumoniae (31%). The prevalence of antibiotics use was 49% with substantial variation between hospitals (range 3-83%). Using logistic regression analysis, four factors were independently associated with the risk of nosocomial infection: central venous catheters (OR 3.3; CI 95% 1.0-5.9), total parenteral nutrition (OR 2.1; CI 95% 1.0-4.5) mechanical ventilation (OR 2.3; CI 95% 1.2-4.1), and low birth weight (OR 2.6; CI 95% 1.0-6.8). The overall mortality was 4.8%; however, patients with nosocomial infection had two times greater risk to die as compared to non-infected children (OR 2.6; CI 95% 1.3-5.1)., Conclusions: This rapid assessment survey using a standard methodology allows to document the prevalence of nosocomial infections in children. The results were used to develop targeted programs on central catheters and mechanical ventilation aimed to reduce bacteremia/sepsis and pneumonia, two nosocomial infections characterized by high prevalence and mortality.

The objective of our study was to validate the diagnostic utility of cardiac troponine T in acute ischemic syndromes, and also in cases of difficult diagnosis. We analyzed its concordance and compare them with conventional enzymatic quantitative methods. We determined sensitivity, specificity, positive and negative predictive values and likelihood ratio. Kappa index was used to know the concordance grade between T troponin and the positive or negative results of the quantitative enzymatic curve. Stochastic significance was valued by Chi square of Mcnemar test. In seventy patients who arrived to the hospital with chest pain who were assigned to five different groups. The sensitivity in quantitative markers was higher than qualitative methods, however the specificity, likelihood ratio was lower. In the total group the concordance analysis between qualitative and quantitative markers was adequate, (kappa index 0.65 p < 0.05). This study suggest that the rapid bedside qualitative test by cardiac Troponin T is a good diagnostic marker compared with conventional quantitative markers to evaluate chest pain in acute ischemic syndromes.

We studied ten patients with unilateral absence of main branch of pulmonary artery (UAMBPA). Six patients with absent right pulmonary artery (ARPA) and four with the left pulmonary artery (ALPA). The presence of either atrial septal defect, ventricular septal defect and patent ductus arteriosus alone or combinated were associated with pulmonary hypertension (mean pressure of the pulmonary artery greater than 48 mm Hg). The patients without associated cardiac defects were asymptomatic and with little elevation of the pulmonary arterial pressure (mean pressure of the pulmonary artery less than 26 mmHg).

The importance of finding in chest roentgenograms the coexistence of aortic and pulmonary artery calcification in emphasized. This radiologic feature is useful in patients which offered difficulty in the clinical diagnosis, it should suggest as a first possibility in the diagnosis patent ductus arteriosus.

The case of a female patient with Rendu-Osler-Weber disease associated with pulmonary arterio-venous fistula localized at the apical segment of the left inferior pulmonary lobe is described. A decrease in the oxygen arterial saturation (SaO2) at adopting the left lateral decubitus position (left-lateral-decubitodeoxia) was found, as well as an increase in the anatomical venoarterial short-circuit (Qs/Qt) in the same position. The resonsible factors of such changes in SaO2 and Qs/Qt related with the body position are analyzed, and the, exceptional in these patients, finding of alteration of pulmonary mechanics is commented.

Thirty two cases of pulmonary arterial hypertension of unknown etiology (PAH-UE) were studied. The diagnosis was established by exclusion after the results of hemodinamics studies. Ninety percent of cases had severe PAH (100 mmHg). The end diastolic right ventricular pressure was elevated in 46% of cases. The total pulmonary vascular resistance was increased in the order of the 1700 dinas. seg. cm-5. The cardiac index was 3.3 1/m2 with a right ventricular work index of 3.96 K gm min. The total lung capacity (TLC) was normal, with a vital capacity (VC) of 78% of the predicted value. The residual volume was increased. The mean value of the maximal midexpiratory flow rate (MMFR) was 78%. The A-a gradient of O2 was 30 mmHg, with a venous mixture expressed as a percentage ratio of the cardiac output (Qva/Qt) of 26%. The mean paO2 mmHg and the anatomical pulmonary artery to vein shunt (Qs/Qt) was 9%, with a DLco normal. The clinical hemodinamic correlation was in good agreement. Our results suggested that PAH-UE "per se" has effect in pulmonary function changing slight lung mechanics, and in a moderate degree lung gas exchange. The hipoxemia results meanly from V/Q imbalance.

We report a male patient, chromosomal complement 44 XY with Turner's phenotype, who has multiple skeletal, genitourinary and mild cardiac abnormalities, without hypogonadism. This patient developed a diffuse infiltrative pulmonary disease which result in pulmonary fibrosis, respiratory insufficiency and cardiac failure. He has also mixed cryoglobulinemia (Type III) with antigammaglobulin antibodies. The relationship among these problems and his phenotype is discussed. Apparently there is only a coincidental association.

A rare case of an oat cell carcinoma is presented. The clinical picture were those of pulmonary thromboembolism and other extrapulmonary symptoms. There were not respiratory symptoms directly related to the lung carcinoma and the chest film remain normal.

Respiratory center (RC) output has been shown to be increased in hypoxemic Chronic Obstructive patients at sea level. In order to asses the separate role of chronic hypoxia on the RC output we studied 30 normal subjects all of them native and residents of Mexico City (altitude: 2,240 m, PaO2: 65-70 torr.). The parameters studied were: occlussion pressure (P0.1), mean inspiratory flow (Vi), and the ratio inspiratory time to total duration of the respiratory cycle (Ti/Ttot). The inspiratory impedance of the respiratory system as well as the minute ventilation (VE) and lastly to ensure isocapnic conditions, the end-tidal CO2 (PECO2), were also measured. These parameters were determined: 1) While breathing room air (RA), 2) after 30 min of breathing an inspired oxygen fraction (FiO2) of 30% and again 3) after 30 min of breathing and FiO2 of 100%. Fifteen of the subjects were studied on supine and the other 15 in the seated position. In most of the subjects the baseline (RA) values of P0.1 were found to be higher than those reported for normals at sea level. In every case, independent of body position, the P0.1 decreased (less than 0.01) to normal sea level values after 30 min of breathing O2 30%. Likewise, Vi and mechanical impedance also decreased (p less than 0.01) and no changes in Ti/Ttot were noted at this FiO2. No further changes occurred after breathing 100%. The above results show that: 1) The RC output in normal people at altitude (i.e. without mechanical abnormalities but with chronic hypoxia) is increased as compared to sea level.(ABSTRACT TRUNCATED AT 250 WORDS)

With a method by which no recirculation was possible the area of a dilution curve was obtained. On this basis it was searched what percentage represents the forward triangle of the total surface of the curve. The rôle of the V/F of the sampling system on this portion of the curve was studied, surface from which the empirical constants for the estimation of the cardiac output derivates. The data obtained suggest that the forward surface triangle was V/F dependent V/F less than 1 gave smaller forward triangles, the opposite was true with V/F greater than 1. It was also found that V/F greater than 1 subestimate the total surface of the dye curve, which means cardiac outputs higher than the real. The forward surface of the curve was reduced to a minimal percentage of the total curve when a V/F less than 1 was used. Situation that makes this area non useful to obtain from them empirical factors. If an empirical factor is use in order to measure cardiac output it had to be accepted that an important grade of error is introduced.