Fisiología respiratoria: relación ventilación/perfusión / Respiratory fisiology: ventilation/perfusion relationship

Las alteraciones de la relación entre la ventilación y el flujo sanguíneo (V/Q) en diversas regiones del pulmón alteran el aporte de oxígeno (O2) y remoción del dióxido de carbono (CO2) al organismo. Fisiológicamente existen diferencias regionales en la relación V/Q. Determinadas patologías pueden alterar esta relación, produciendo tres escenarios distintos: Cortocircuito (Shunt), Alteración V/Q y aumento del espacio muerto. Para evaluar estos escenarios y realizar una aproximación diagnostica son de utilidad el estudio de los gases arteriales y venosos, la diferencia alveolo arterial y la respuesta al suministrar O2

Alterations in the ventilation perfusion relationship (V/Q) in various lung regions alter the supply of oxygen (O2) and the removal of carbon dioxide (CO2) in the body. Physiologically, there are regional differences in the V/Q ratio. Certain pathologies can alter this relationship, producing three different scenarios: Shunt, V/Q mismach and dead space increased. To evaluate these scenarios and carry out a diagnostic approach, it is useful to study arterial and venous gasometry, the alveolar arterial difference and the response to oxygen supplying.

Lipoabdominoplasty: repercussions for diaphragmatic mobility and lung function in healthy women / Lipoabdominoplastia: repercussão na mobilidade diafragmática e função pulmonar em mulheres saudáveis

ABSTRACT Objective: To evaluate the impact of lipoabdominoplasty on diaphragmatic mobility (DM) and lung function in healthy women. Methods: This was a prospective cohort study using high-resolution ultrasound and forced spirometry to assess DM and lung function, respectively, prior to lipoabdominoplasty, as well as on postoperative day (POD) 10 and POD 30. DM was measured under two conditions: during tidal volume breathing and during a VC maneuver. Results: The sample consisted of 20 women, with a mean age of 39.85 ± 7.52 years and a mean body mass index of 26.21 ± 2.0 kg/m2. Comparing the preoperative and postoperative periods, we found that DM and lung function values were significantly lower after lipoabdominoplasty, the mean DM on POD 10 being 17% and 15% lower during tidal volume breathing and during the VC maneuver, respectively, in comparison with the preoperative mean (p = 0.009 and p < 0.001, respectively). In addition, FEV1, FVC, and PEF were significantly lower on POD 10 than in the preoperative period (p = 0.046, p = 0.002, and p < 0.001, respectively), returning to preoperative values by POD 30. Conclusions: Lipoabdominoplasty appears to have negative short-term repercussions for DM and lung function in healthy women. However, lung function and DM are both apparently restored to preoperative conditions by POD 30. (ClinicalTrials.gov identifier: NCT02762526 [http://www.clinicaltrials.gov/])

RESUMO Objetivo: Avaliar o impacto da lipoabdominoplastia na mobilidade diafragmática (MD) e na função pulmonar de mulheres saudáveis. Métodos: Estudo prospectivo de coorte com ultrassonografia de alta resolução e espirometria forçada para a avaliação da MD e da função pulmonar, respectivamente, antes da lipoabdominoplastia, no 10º dia do pós-operatório e no 30º dia do pós-operatório. A MD foi medida durante a respiração em volume corrente e durante uma manobra de CV. Resultados: A amostra foi composta por 20 mulheres, com média de idade de 39,85 ± 7,52 anos e média de índice de massa corporal de 26,21 ± 2,0 kg/m2. Ao compararmos os períodos pré e pós-operatório, observamos que a MD e a função pulmonar foram significativamente menores após a lipoabdominoplastia; a média de MD no 10º dia do pós-operatório foi 17% menor durante a respiração em volume corrente e 15% menor durante a manobra de CV do que a média pré-operatória (p = 0,009 e p < 0,001, respectivamente). Além disso, o VEF1, a CVF e o PFE foram significativamente menores no 10º dia do pós-operatório que no pré-operatório (p = 0,046, p = 0,002 e p < 0,001, respectivamente), retornando aos valores pré-operatórios até o 30º dia do pós-operatório. Conclusões: A lipoabdominoplastia parece ter repercussões negativas em curto prazo na MD e função pulmonar de mulheres saudáveis. No entanto, tanto a função pulmonar como a MD aparentemente retornam ao estado pré-operatório até o 30º dia do pós-operatório. (ClinicalTrials.gov identifier: NCT02762526 [http://www.clinicaltrials.gov/])

Extended-time of noninvasive positive pressure ventilation improves tissue perfusion after coronary artery bypass surgery: a randomized clinical trial

Abstract Objective: To compare the effects of extended- versus short-time noninvasive positive pressure ventilation on pulmonary function, tissue perfusion, and clinical outcomes in the early postoperative period following coronary artery bypass surgery in patients with preserved left ventricular function. Methods: Patients were randomized into two groups according to noninvasive positive pressure ventilation intensity: short-time noninvasive positive pressure ventilation n=20 (S-NPPV) and extended-time noninvasive positive pressure ventilation n=21 (E-NPPV). S-NPPV was applied for 60 minutes during immediate postoperative period and 10 minutes, twice daily, from postoperative days 1-5. E-NPPV was performed for at least six hours during immediate postoperative period and 60 minutes, twice daily, from postoperative days 1-5. As a primary outcome, tissue perfusion was determined by central venous oxygen saturation and blood lactate level measured after anesthetic induction, immediately after extubation and following noninvasive positive pressure ventilation protocols. As a secondary outcome, pulmonary function tests were performed preoperatively and in the postoperative days 1, 3, and 5; clinical outcomes were recorded. Results: Significant drop in blood lactate levels and an improvement in central venous oxygen saturation values in the E-NPPV group were observed when compared with S-NPPV group after study protocol (P<0.01). The E-NPPV group presented higher preservation of postoperative pulmonary function as well as lower incidence of respiratory events and shorter postoperative hospital stay (P<0.05). Conclusion: Prophylactic E-NPPV administered in the early postoperative period of coronary artery bypass surgery resulted in greater improvements in tissue perfusion, pulmonary function and clinical outcomes than S-NPPV, in patients with preserved left ventricular function. Trial Registration: Brazilian Registry of Clinical trial - RBR7sqj78 - http://www.ensaiosclinicos.gov.br

Monitorización respiratoria del paciente pediátrico en la Unidad de Cuidados Intensivos / Respiratory monitoring of pediatric patients in the Intensive Care Unit

Resumen: La monitorización respiratoria representa un importante rol en el cuidado del niño con falla respiratoria aguda. Por tanto, su apropiado uso y correcta interpretación (reconociendo qué señales y variables deben ser priorizadas) deberían ayudar a un mejor entendimiento de la fisiopatología de la enfermedad y de los efectos de las intervenciones terapéuticas. Asimismo, la monitorización del paciente ventilado permite, entre otras determinaciones, evaluar diversos parámetros de la mecánica respiratoria, conocer el estado de los diferentes componentes del sistema respiratorio y guiar los ajustes de la terapia ventilatoria. En esta actualización se describe la utilidad de diversas técnicas de monitorización respiratoria (incluyendo métodos convencionales y otros más recientes), se definen conceptos básicos de mecánica ventilatoria, su interpretación y cómo el adecuado análisis de la información puede ocasionar un impacto en el manejo clínico del paciente.

Abstract: Respiratory monitoring plays an important role in the care of children with acute respiratory failure. Therefore, its proper use and correct interpretation (recognizing which signals and variables should be prioritized) should help to a better understanding of the pathophysiology of the disease and the effects of therapeutic interventions. In addition, ventilated patient monitoring, among other determinations, allows to evaluate various parameters of respiratory mechanics, know the status of the different components of the respiratory system and guide the adjustments of ventilatory therapy. In this update, the usefulness of several techniques of respiratory monitoring including conventional respiratory monitoring and more recent methods are described. Moreover, basic concepts of mechanical ventilation, their interpretation and how the appropriate analysis of the information obtained can cause an impact on the clinical management of the patient are defined.

Função pulmonar após cirurgia de revascularização do miocárdiocom e sem circulação extracorpórea / Pulmonary function following on and off-pump coronary artery bypass grafting

Objetivos: avaliar e comparar a função pulmonar de pacientes submetidos à cirurgia de revascularização do miocárdio com e sem o uso de circulação extracorpórea. Métodos: a amostra foi composta por 40 pacientes submetidos à cirurgia de revascularização do miocárdio, classificados em dois grupos: com circulação extracorpórea (grupo CCEC ? 20 pacientes) ou sem circulação extracorpórea (grupo SCEC ? 20 pacientes). Registros espirométricos da capacidade vital forçada (CVF) e do volume expiratório forçado no primeiro segundo (VEF1) foram obtidos no período pré-operatório (considerado basal) e no primeiro, terceiro e quinto dias do período pós-operatório. Resultados: obser-vou-se que no geral os valores de CVF e VEF1 diminuíram no primeiro pós-operatório em relação ao basal (diferença média = 1,8±1,0, p<0,001 e 1,3±1,0, p<0,001, respectivamente), tendo recuperação parcial no terceiro e no quinto pós-operatórios, sem retornar aos valores iniciais (diferença média 1,2±1,1, p<0,001 e 0,9±0,9, p<0,001, respectivamente). Após controle para os valores basais, não foram observadas diferenças significativas entre os grupos CCEC e SCEC quanto à CVF e ao VEF1 no quinto dia pós-operatório. Conclusões: a cirurgia de revascularização do miocárdio associou-se a um decréscimo significante na função pulmonar em todos os pacientes, havendo recuperação parcial da CVF e do VEF1 no quinto pós-operatório para os dois grupos, porém sem retorno aos valores basais. Não se observou associação estatisticamente significativa entre realização de circulação extracorpórea e função pulmonar no quinto dia pós-operatório.

Aims: To evaluate and compare the pulmonary function of patients submitted to myocardial revascularization surgery, with and without the use of extracorporeal circulation. Methods: The sample comprised 40 patients submitted to myocardial revascularization surgery, classified into two groups, depending on whether extracorporeal circulation was used (wECC ? 20 patients) or not (nECC ? 20 patients). Spirometric recordings of forced vital capacity (FVC) and forced expiratory volume in the first second (FEV1) were obtained during the preoperative period (considered baseline) and on the first, third and fifth days postoperatively. Results: In general, the values of FVC and FEV1 diminished on the first day postoperatively compared to the baseline (mean difference = 1.8±1.0, p<0.001 and 1.3±1.0, p<0.001, respectively), with partial recovery on the third and fifth day postoperatively, with no return to the initial values (mean difference = 1.2±1.1, p<0.001 and 0.9±0.9, p<0.001, respectively). After controlling for baseline values, no significant differences were observed between the wECC and nECC groups as to FVC and FEV1 on the 5th day postoperatively. Conclusions: Myocardial revascularization surgery was associated to a significant decrease in pulmonary function in all patients, with partial recovery of FVC and FEV1 on the fifth day postoperatively for all groups, with no return to baseline values. No statistically significant association was found between extracorporeal circulation and pulmonary function on the fifth day postoperatively.