César Augusto Melo e Silva

Evaluation of peak inspiratory pressure, tidal volume and respiratory rate during ventilation of premature lambs using a self-inflating bag

OBJECTIVE To evaluate the peak inspiratory pressure, tidal volume and respiratory rate achieved during manual ventilation of premature lambs, using a self-inflating bag. METHODS In this descriptive, experimental study, five pairs of physicians, selected at random among 35 neonatologists working at a neonatal intensive care unit and with experience in the resuscitation of newborn infants, ventilated five intubated premature lambs using a self-inflating bag. Pressure and flow monitor signals were passed through a transducer and digitized for recording and analysis. Tidal volume and pressure curves were obtained from the integral of flow rate, at peak, during the last 50 seconds of every fifth minute, and analyzed. RESULTS Median pressure was 39.8 (IQ(25-75%) 30.2-47.2) cmH(2)O; being below 20 in 1.1% of cases and above 40 in 49.1%. Seven out of 10 physicians produced more than six pressure peaks of over 40 cmH(2)O. Median tidal volume/kg was 17.8 (IQ(25-75%) 14.1-22.4) mL, being below 5 mL in 0.1% of cases and greater than or equal to 20 mL in 37.7%. All of the physicians propelled five or more ventilation cycles with tidal volume/kg of 20 mL or more. Respiratory rate was between 30 and 60 cycles/minute in 65.9% of cases, being below 30 in 6.8% of cases and over 60 in 27.3% of cases. CONCLUSIONS There was major variation in peak inspiratory pressure and tidal volume/kg values, which were in many cases elevated, attaining levels that habitually cause biotrauma, while respiratory rates were adequate in the majority of cases.

Effects of Tityus serrulatus scorpion venom on lung mechanics and inflammation in mice

The present study evaluated the effects of an intramuscular injection of Tityus serrulatus venom (TsV) (0.67 miocrog/g) on lung mechanics and lung inflammation at 15, 30, 60 and 180 min after inoculation. TsV inoculation resulted in increased lung elastance when compared with the control group (p < 0.001); these values were significantly higher at 60 min than at 15 and 180 min (p < 0.05). Resistive pressure (DeltaP1) values decreased significantly at 30, 60 and 180 min after TsV injection (p < 0.001). TsV inoculation resulted in increased lung inflammation, characterised by an increased density of mononuclear cells at 15, 30, 60 and 180 min after TsV injection when compared with the control group (p < 0.001). TsV inoculation also resulted in an increased pulmonary density of polymorphonuclear cells at 15, 30 and 60 min following injection when compared to the control group (p < 0.001). In conclusion, T. serrulatus venom leads to acute lung injury, characterised by altered lung mechanics and increased pulmonary inflammation.

Avaliação muscular isocinética do quadríceps em indivíduos com doença pulmonar obstrutiva crónica

Rationale: Muscle debility has a significant impact on health-related quality of life in subjects with chronic obstructive pulmonary disease (COPD), and is correlated to exacerbation and even mortality. Assessing muscle strength is extremely relevant. Lack of standardisation in numbers of sets and rest interval in isokinetic test protocol can lead to distinct results, making comprehension and comparisons among studies difficult. Aim: To analyse the effect of two sets and three different rest intervals on isokinetic strength measurement of quadriceps tests, in order to define the adequate test protocol. Methods: Subjects with severe or very severe COPD underwent three isokinetic tests to evaluate knee extensor muscle strength, at an angular velocity of 60° · s− 1, with rest intervals of 30, 60 and 120 seconds. Each test consisted of two sets of five repetitions, during which peak torque, total work and fatigue index were measured. Results: In 20 studied subjects (66.1 ± 7.4 years, 70 ± 10.8 kg, 167.4 ± 6.2 cm, FEV1 36.5 ± 10.1%), there were no significant differences in peak torque, total work and fatigue index, independent of number of sets or rest interval between sets. Conclusion: In subjects with severe or very severe COPD, quadriceps muscle strength can be evaluated by an isokinetic protocol with one set of five repetitions. If two sets are performed, a rest interval of 30 seconds is enough to ensure muscle recovery between sets. Rev Port Pneumol 2010; XVI (5): 717-736

Avaliação do pico de pressão e da freqüência respiratória durante o uso de balão auto-inflável em um modelo de pulmão neonatal

OBJETIVO: Avaliar o pico de pressao inspiratoria e a frequencia ventilatoria obtidos por medicos quando da utilizacao de balao auto-inflavel neonatal em modelo de pulmao. METODOS: Quinze medicos ventilaram simuladores de pulmao de recem-nascidos a termo e pre-termo, sendo os desfechos captados atraves de um monitor de ventilacao. RESULTADOS: As medianas dos picos de pressao foram 23 (intervalo interquartil, 15-47) e 26 (intervalo interquartil, 14-51) cmH2O, sendo menor que 20 em 41,2 e 35,8% das vezes; maior que 40 em 29,7 e 33,6% das vezes e entre 27 e 33 cmH2O em 8,2 e 6,5% das vezes, para o pulmao de termo e de pre-termo, respectivamente. As medianas das frequencias ventilatorias foram de 45 (intervalo interquartil, 36-57) e 48 (intervalo interquartil, 39-55,5) ciclos por minuto, sendo menor que 30 em 9,3 e 6,7% das vezes e maior que 60 em 12 e 13,3% das vezes, respectivamente, para o pulmao de termo e de pre-termo. As diferencas nas medianas nao foram estatisticamente significantes. CONCLUSAO: A ventilacao utilizando o balao auto-inflavel promoveu adequacao para a frequencia ventilatoria em aproximadamente 80% das vezes, e os medicos nao conseguiram promover ventilacao com minima variabilidade na pressao, alcancando niveis diferentes daqueles definidos no curso de reanimacao neonatal em 70% das vezes. Essa situacao independeu da ventilacao do pulmao-teste analogo ao sistema respiratorio de recem-nascidos a termo ou pre-termo.

Evaluation of peak inspiratory pressure and respiratory rate during ventilation of an infant lung model with a self-inflating bag

OBJECTIVE To evaluate the peak inspiratory pressure and ventilation rate achieved by physicians when using a neonatal self-inflating bag on a lung model. METHODS Fifteen physicians ventilated full term and preterm infant lung simulators while the outcomes were captured by a ventilation monitor. RESULTS Median peak pressures in cmH(2)O for full term and preterm lungs were 23 (interquartile range: 15-47) and 26 (interquartile range: 14-51), being less than 20 in 41.2 and 35.8% of the pressure curves analyzed, more than 40 in 29.7 and 33.6%, and between 27 and 33 cmH(2)O in 8.2 and 6.5% of the curves, respectively. Median ventilation rates were 45 (interquartile range: 36-57) and 48 (interquartile range: 39-55.5) cycles per minute, being more than 30 in 9.3 and 6.7% of pressure curves and more than 60 in 12 and 13.3% of pressure curves, for the full term and preterm lungs, respectively. The differences between these medians were not statistically significant. CONCLUSIONS Ventilation rates achieved with the self-inflating bag were adequate in approximately 80% of pressure curves analyzed, but the physicians were unable to provide ventilation with minimal pressure variation, producing pressures that diverged from those defined by the neonatal resuscitation training course in 70% of the curves. This was irrespective of whether they were ventilating the lung model analogous to preterm or full term infant lungs.

Isokinetic muscle evaluation of quadriceps in patients with chronic obstructive pulmonary disease

RATIONALE Muscle debility has a significant impact on health-related quality of life in subjects with chronic obstructive pulmonary disease (COPD), and is correlated to exacerbation and even mortality. Assessing muscle strength is extremely relevant. Lack of standardisation in numbers of sets and rest interval in isokinetic test protocol can lead to distinct results, making com- prehension and comparisons among studies difficult. AIM To analyse the effect of two sets and three different rest intervals on isokinetic strength measurement of quadriceps tests, in order to define the adequate test protocol. METHODS Subjects with severe or very severe COPD underwent three isokinetic tests to evaluate knee extensor muscle strength, at an angular velocity of 60°⋅s⁻¹, with rest intervals of 30, 60 and 120 seconds. Each test consisted of two sets of five repetitions, during which peak torque, total work and fatigue index were measured. RESULTS In 20 studied subjects (66.1 ± 7.4 years, 70 ± 10.8 kg, 167.4 ± 6.2 cm, FEV₁ 36.5 ± 10.1%), there were no significant differences in peak torque, total work and fatigue index, independent of number of sets or rest interval between sets. CONCLUSION In subjects with severe or very severe COPD, quadriceps muscle strength can be evaluated by an isokinetic protocol with one set of five repetitions. If two sets are performed, a rest interval of 30 seconds is enough to ensure muscle recovery between sets.

Stability of the animal model of oleic acid-induced acute lung injury.

OBJECTIVE To evaluate the stability of hemodynamic, respiratory and gas exchange variables in an animal model of oleic acid-induced acute lung injury. METHODS This was an experimental study involving 10 mongrel dogs. The variables were measured at baseline, as well as at 30, 60, 90 and 120 min after the administration of oleic acid. In order to analyze repeated measurements, linear and quadratic effects were tested. Mixed linear models with diversified variance and covariance structures were used, depending on the variable studied. RESULTS We found that mean arterial blood pressure stabilized at 30 min, as did heart rate, pulmonary arterial pressure and pulmonary capillary pressure at 60 min. Respiratory rate, tidal volume, minute volume and respiratory work stabilized at 30 min. Regarding gas exchange variables, PaO2, PaO2/FiO2 ratio and pulmonary shunt fraction stabilized at 30 min. The remaining variables maintained a continuous rise or fall. CONCLUSIONS This oleic acid-induced acute lung injury model is stable for some of the variables tested, although stabilization occurs at different times. The respiratory and gas exchange variables stabilized at 30 min, whereas the hemodynamic variables stabilized at 60 min.

Pulmonary mechanic and lung histology injury induced by Crotalus durissus terrificus snake venom.

In the present work we investigated the effects of Crotalus durissus terrificus venom (CdtV) on the pulmonary mechanic events [static and dynamic elastance, resistive (DeltaP1) and viscoelastic pressures (DeltaP2)] and histology after intramuscular injection of saline solution (control) or venom (0.6 microg/g). The static and dynamic elastance values were increased significantly after 3 h of venom inoculation, but were reduced at control values in the other periods studied. The DeltaP1 values that correspond to the resistive properties of lung tissue presented a significant increase after 6h of CdtV injection, reducing to basal levels 12h after the venom injection. In DeltaP2 analysis, correspondent to viscoelastic components, an increase occurred 12 h after the venom injection, returning to control values at 24 h. CdtV also caused an increase of leukocytes recruitment (3-24 h) to the airways wall as well as to the lung parenchyma. In conclusion, C. durissus terrificus rattlesnake venom leads to lung injury which is reverted, after 24 h of inoculation.

Using clinical data to predict sleep hypoxemia in patients with acromegaly

Hypoxemia secondary to sleep apnea is commonly seen in patients with acromegaly, and this alteration apparently leads to considerable morbidity and mortality among such patients. With the objective of identifying hypoxemia based on clinical data, we conducted a cross-sectional study of 34 patients with acromegaly, all of whom were submitted to nocturnal oximetry and evaluation of snoring, as well as to the determination of body mass index (BMI) and neck circumference. In addition, daytime sleepiness was evaluated using the Epworth sleepiness scale (ESS). In this study, sleep hypoxemia was defined as five or more episodes of desaturation per hour. The sensitivity and specificity of the various parameters in predicting such hypoxemia were, respectively, as follows: snoring (92.9% and 35%); BMI>28.5 kg/m2 (71.4% and 60%); neck circumference>44 cm (28.6% and 95%); ESS score>10 (42.9% and 70%). For patients with a neck circumference of more than 44 cm, the probability of sleep hypoxemia was found to increase from 41% (pre-test) to 80% (post-test). For patients with a neck circumference of less than 44 cm, positivity for two or three of the other parameters (snoring, ESS score>10 and BMI>28.5 kg/m2) increased the post-test probability to 62%, whereas positivity for only one (or none) reduced post-test probability to 8%. We can conclude that the clinical parameters evaluated allowed us to predict, with considerable accuracy, whether or not sleep hypoxemia would occur in patients with acromegaly.

Análise da mecânica pulmonar em modelo experimental de sepse

OBJECTIVE To determine whether pulmonary mechanics are altered in mice with sepsis. METHODS A total of 40 Balb/c mice were divided into two groups: survival (n = 21) and pulmonary mechanics (n = 19). The survival group was divided into three subgroups: control (n = 7), sublethal (n = 7) and lethal (n = 7). The pulmonary mechanics group was also divided into three subgroups: control (n = 5), sublethal (n = 7) and lethal (n = 7). Sepsis was induced through cecal ligation and puncture, the latter varying in degree (sublethal or lethal). At eight hours after the intervention, pulmonary mechanics were measured through end-inflation occlusion. In the pulmonary mechanics group, the following variables were studied: total pressure, resistance, viscoelasticity, dynamic compliance and static compliance. The data obtained were analyzed using one-way ANOVA. RESULTS The data for the survival group indicate the efficacy of the model employed. There were no statistically significant differences among the pulmonary mechanics subgroups in terms of dynamic compliance, static compliance, total pressure, resistance or viscoelasticity. CONCLUSION At eight hours after cecal ligation and puncture, there were no changes in the lung parenchyma, nor were any alterations observed in the viscous and viscoelastic components of the lung.