[Post-pneumonectomy edema]. / Edema postneumonectomía.

A 64-year-old man complained of irritable cough of 3 months' duration and 1 episode of hemoptysis and dyspnea related to effort. The radiograph revealed a mass in the upper right lobe. Adenocarcinoma of the lung was diagnosed by mediastinoscopy. After removal of the right lung, the patient was admitted to the recovery unit for 36 hours and transferred out without complications. The clinical course in 48 hours on the ward included increasing dyspnea, tachypnea and greater respiratory effort with hypoxemia in spite of increased FiO2. A radiograph showed pulmonary edema and the patient was readmitted to the recovery unit. We describe this case of postpneumonectomy edema and discuss the possible origins of the clinical picture, differential diagnosis, preventive measures and possible treatments.

[Comparison of patient-ventilator synchronization during pressure support ventilation versus amplified spontaneous pattern in postoperative patients]. / Comparación de la sincronización paciente-ventilador durante la ventilación con presión de soporte y con patrón espontáneo amplificado en pacientes postoperados.

INTRODUCTION: Patient-ventilator desynchronization can develop during weaning from proportional-assist ventilation. Poor adaptation between ventilator assistance and the patient's ventilatory demand is termed asynchrony. OBJECTIVES: Comparative analysis of types and incidence of asynchrony in patients receiving pressure support (PS) ventilation or amplified spontaneous pattern (ASP) ventilation, to determine whether the presence of asynchrony is related to a patient's level of dyspnea or anxiety. PATIENTS AND METHODS: Eighteen patients were studied prospectively after undergoing coronary revascularization. Baseline anxiety was assessed before surgery. A pleural catheter was inserted during surgery. After surgery patients were randomly assigned to ventilation with PS mode or ASP. Flow curves, flow volume, airway pressure and pleural pressure were recorded by a BioCore CP100 monitor once the patient's work of breathing held steady between 0.3 and 0.5 J/l. The curves were recorded for 10 m on a computer for later analysis. After each recording dyspnea and anxiety were assessed. Fifty consecutive cycles per patient were analyzed, signalling in each case the start of inspiration and expiration. RESULTS: Nine hundred ventilatory cycles were analyzed to identify five types of patient-ventilator asynchrony: 1) self-cycled (SC: inspiratory assistance from the ventilator without demand by patient); 2) no effort detected (NED: patient inspiratory effort but no flow response from the ventilator); 3) interrupted support (IS: interruption of ventilatory support during patient inspiration); 4) prolonged mechanical inspiration (PMI: maintenance of ventilatory support during patient expiration), and 5) double-breath, single cycle (DBSC: sequence of inspiration-expiration-inspiration of the patient within a single assisted inspiration). Asynchronic cycles were found in all PS-ventilated patients (84 of 450; 18.7%): 9.1% SC, 4% NED, 2.2% IS, 1.5% PMI and 1.8% DBSC. Asynchronic cycles were seen in only two ASP patients (16 of 450; 3.5%); both cases were NED asynchrony. Levels of anxiety and dyspnea were slightly higher with the PS mode than with ASP but the differences were not significant (p = 0.05). CONCLUSIONS: The incidence of asynchrony during assisted ventilation is very high with the PS mode and is substantially less with ASP. Asynchrony is difficult to detect clinically and is revealed only by advanced cycle-to-cycle monitoring.

[Preoxygenation for anesthesia]. / Preoxigenación en anestesia.

Oxygenation, or rather denitrogenation, prior to apnea during anesthetic induction attempts to replace alveolar nitrogen with oxygen to achieve an intrapulmonary oxygen reserve that will allow apnea to be as prolonged as possible with the least possible desaturation. During apnea, the rate of arterial desaturation depends mainly on the volume of oxygen stored in the lung, on mixed venous oxygen saturation, and on the presence of intrapulmonary shunt. Together, these factors account for the higher rate of desaturation during apnea in children, obese individuals, postoperative patients, and pregnant women. Two approaches to preoxygenation have proven effective to date: ventilation with 100% oxygen at tidal volume for 3 minutes using a well-sealed face mask and the performance of 8 vital capacity maneuvers in 1 minute. The efficacy of preoxygenation can be assessed by expired oxygen fraction or by pulse oximetry. In a healthy adult, both methods described ensure sufficient oxygenation (pulse oximetry 90% to 95%) after a period of apnea lasting between 6 and 10 minutes.

Airway pressure curve: a good tool to measure neural inspiratory time?

BACKGROUND: Considerable asynchrony during pressure-support ventilation has been reported. While the beginning of active inspiration is usually identifiable in the airway pressure (Paw) curve (the inspiratory trigger), there is still a need for accurate, non-invasive methods to identify the end of inspiration. To test the hypothesis that inspiration, particularly the end of inspiration, can be estimated from the Paw curve, we compared indirect measurements based on Paw with simultaneous direct electromyography of the diaphragm (EMGdi). METHODS: We prospectively studied 10 patients during the weaning period after cardiac surgery. Inspiratory pressure support was set at 20, 15, 10, and 5 cm H(2)O; 25 respiratory cycles were analyzed at each pressure level. Recording of the electromyogram was obtained with electrodes inserted into the diaphragm during surgery. RESULTS: The start and end of inspiration were identified in the Paw curve in 99% and 98% of the 1000 cycles analyzed, respectively, and were coincident with the electromyogram in 62% and 53% of the cycles, respectively. The inspiratory time estimated from the Paw curve was well correlated (r=0.94, P<0.0001) with the electromyogram. CONCLUSION: The end of neural inspiration (EMGdi) can be easily and with little error recognized from the Paw curve alone in patients with normal ventilatory mechanics who receive pressure-support ventilation.