ABSTRACT
JUSTIFICATIVA E OBJETIVOS: Em ventilação mecânica invasiva e não-invasiva, o conhecimento da fisiologia da mecânica respiratória, é imprescindível para tomada de decisões e no manuseio eficiente dos ventiladores modernos. A monitorização dos parâmetros da mecânica pulmonar é recomendada nos trabalhos de revisão e de pesquisas clínicas. O objetivo deste estudo foi rever os conceitos de mecânica pulmonar e os métodos utilizados para obtenção de medidas à beira do leito, enfatizando três parâmetros: resistência, complacência e PEEP intrínseca. MÉTODO: Foi realizada revisão bibliográfica através dos bancos de dados LILACS, MedLine e PubMed, no período de 1996 a 2006. RESULTADOS: Esta revisão abordou os parâmetros de resistência, complacência pulmonar e PEEP intrínseca como fundamentais na compreensão da insuficiência respiratória aguda e suporte ventilatório mecânico, principalmente na doença pulmonar obstrutiva crônica (DPOC) e na síndrome da angústia respiratória aguda (SARA). CONCLUSÕES: A monitorização da mecânica pulmonar em pacientes sob ventilação mecânica em unidade de terapia intensiva (UTI) pode fornecer dados relevantes e deve ser implementada de forma sistemática e racional.
BACKGROUND AND OBJECTIVES: In mechanical ventilation, invasive and noninvasive, the knowledge of respiratory mechanic physiology is indispensable to take decisions and into the efficient management of modern ventilators. Monitoring of pulmonary mechanic parameters is been recommended from all the review works and clinical research. The objective of this study was review concepts of pulmonary mechanic and the methods used to obtain measures in the bed side, preparing a rational sequence to obtain this data. METHODS: It was obtained bibliographic review through data bank LILACS, MedLine and PubMed, from the last ten years. RESULTS: This review approaches parameters of resistance, pulmonary compliance and intrinsic PEEP as primordial into comprehension of acute respiratory failure and mechanic ventilatory support, mainly in acute respiratory distress syndrome (ARDS) and in chronic obstructive pulmonary disease (COPD). CONCLUSIONS: Monitoring pulmonary mechanics in patients under mechanical ventilation in intensive care units gives relevant informations and should be implemented in a rational and systematic way.
Subject(s)
Lung Compliance , Monitoring, Physiologic , Positive-Pressure Respiration , Lung/physiology , Respiration, ArtificialABSTRACT
Objective To evaluate the effects of inhaled bronchodilators on dynamic PEEPi in COPD patients.Methods Twenty moderate to severe COPD subjects were divided into three groups.Lung functions,PEEPi,dyn and Borg score were measured at baseline and 30 min after inhaled placebo,and after inhalation of salbutamol 400 ?g(or ipratropium 80 ?g),ipratropium 80 ?g(or salbutamol 400 ?g)in sequence at interval as specified in different groups.Results In comparison with placebo,PEEPi,dyn decreased after inhalied bronchodilators(P
ABSTRACT
BACKGROUND: Auto-PEEP which develops when expiratory lung emptying is not finished until the beginning of next inspiration is frequently found in patients on mechanical ventilation. Its presence imposes increased risk of barotrauma and hypotension, as well as increased work of breathing (WOB) by adding inspiratory threshold load and/or adversely affecting to inspiratory trigger sensitivity. The aim of this study is to evaluate the relationship of auto-PEEP with WOB and to evaluate the effect of PEEP applied by ventilator (external PEEP) on WOB in patients with auto-PEEP. METHOD: 15 patients, who required mechanical ventilation for management of acute respiratory failure, were studied. First, the differences in WOB and other indices of respiratory mechanics were examined between 7 patients with auto-PEEP and 8 patients without auto-PEEP. Then, we applied the 3 cm H2O of external PEEP to patients with auto-PEEP and evaluated its effects on lung mechanics as well as WOB. Indices of respiratory mechanics including tidal volume (V(T)), repiratory rate, minute ventilation (V(E)), peak inspiratory flow rate (PIFR), peak expiratory flow rate (PEFR), peak inspiratory pressure (PIP), T(I)/T(TOT), auto-PEEP, dynamic compliance of lung (Cdyn), expiratory airway resistance (RAWe), mean airway resistance (RAWm), P(0.1), work of breathing performed by patient (WOB), and pressure-time product (PTP) were obtained by CP-100 Pulmonary Monitor (Bicore,USA). The values were expressed as meanSEM (standard error of mean). RESULTS: 1) Comparison of WOB and other indices of respiratory mechanics in patients with and without auto-PEEP: There was significant increase in WOB (1.71 +/-0.24 vs 0.500.19 J/L, p=0.007), PTP (317+/-70 vs 98+/-36 cm H2O * sec/min, p=0.023), RAWe (35.6+/-5.7 vs 18.2+/-2.3 cm H20/L/sec, p=0.023), RAWm (28.8+/-2.5 vs 11.9+/-2.0 cm H2O/L/sec, p=0.001) and P0.1 (6.21.0 vs 2.9+0.6 cm H2O, p=0.021) in patients with auto-PEEP compared to patients without auto-PEEP. The differences of other indices including V(T), PEFR, V(E) and T(I)/T(TOT) showed no significance. 2) Effect of 3 cm H2O external PEEP on respiratory mechanics in patients with auto-PEEP: When 3 cm H2O of external PEEP was applied, there were significant decrease in WOB (1.71+/-0.24 vs 1.20+/-0.21 J/L, p=0.021) and PTP (317+/-70 vs 231+/-55 cm H2O * sec/min, p=0.038). RAWm showed a tendency to decrease (28.8+/-2.5 vs 23.9+/-2.1 cm H2O, p=0.051). But PIP was increased with application of 3 cm H2O of external PEEP (16+/-2 vs 22+/-3 cm H2O, p=0.008). V(T), V(E), PEFR, T(I)/T(TOT) and Cdyn did not change significantly. CONCLUSION: The presence of auto-PEEP in mechanically ventilated patients was accompanied with increased WOB performed by patient, and this WOB was decreased by 3 cm H2O of externally applied PEEP. But, with 3 cm H2O of external PEEP, increased PIP was noted, implying the importance of close monitoring of the airway pressure during application of external PEEP.