A new simple method to perform pressure-volume curves obtained under quasi-static conditions during mechanical ventilation

Rodríguez, Laura Rodríguez; Marquer, B.; Mardrus, P.; Molénat, Françoise; Grand, J.L. Le; Reboul, M; Garrigues, B.

doi:10.1007/s001340050812

Cited by 27 publications

(21 citation statements)

References 19 publications

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“…The slopes of P-V curves and the LIP were similar for all methods, indicating that the resistive pressure generated by administering a constant flow equal to or less than 9 l/min is of no clinical significance, at least in patients without obstructive lung disease. Similar results have also been reported by Rodriquez et al [15] who obtained the P-V curve by inflating the lung with a constant flow of 7 l/min.…”

supporting

confidence: 78%

“…Two recent studies have shown, in patients with relatively low airway resistance, that the P-V curve obtained with low flow inflation (< 0.15 l/s) did not differ from that determined by conventional methods [14,15]. Therefore, provided that patients with normal or slightly elevated airway resistance are studied, P-V curves obtained with the low inflation technique are reliable and may be used instead of the time-consuming conventional techniques.…”

Section: Discussionmentioning

confidence: 99%

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Low flow inflation pressure-time curve in patients with acute respiratory distress syndrome

et al. 2000

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supporting

confidence: 78%

Section: Discussionmentioning

confidence: 99%

Low flow inflation pressure-time curve in patients with acute respiratory distress syndrome

et al. 2000

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“…Constant flows v10 L?min -1 allow the obtention of P/V curves quasi-superimposable to those obtained with static methods [15,[18][19][20]. Such low flows can be delivered by most intensive care unit (ICU) ventilators in the absence of any special equipment.…”

Section: Quasistatic Methods Using a Continuous Inflation At Constantmentioning

confidence: 99%

“…The measurement of the chord compliance (the slope of the linear part of the P/V curve) and the determination of the upper and lower inflection points can be carried out using the mobile cursors available on the ventilator display screen. The entire procedure takes 1 min and is performed without disconnecting the paralysed patient from the ventilator [18,19]. Some recent ICU ventilators are equipped with specific flow generators that deliver constant flows between 1-10 L?min -1 allowing the obtention of static or quasi-static P/V curves.…”

Section: Quasistatic Methods Using a Continuous Inflation At Constantmentioning

confidence: 99%

Pressure/volume curves and lung computed tomography in acute respiratory distress syndrome

Rouby¹,

Lü²,

Vieira³

2003

European Respiratory Journal

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Pressure/volume curves and lung computed tomography in acute respiratory distress syndrome. J-J. Rouby, Q. Lu, S. Vieira. #ERS Journals Ltd 2003. ABSTRACT: Pressure/volume (P/V) curves can be measured by static methods, constant or sinusoidal flow methods and the dynostatic method that allows a breath-tobreath determination of P/V curves. Recent ventilators are equipped with specific flow generators and software aimed at obtaining P/V curves without disconnecting the patient from the ventilator.The most recent generation of computed tomography scanners allows the quantitative determination of lung aeration, lung volumes (gas and tissue), alveolar recruitment and lung overinflation of the whole lung. In the supine position, the acute respiratory distress syndrome (ARDS) lung is characterised by an increase in lung tissue that predominates in upper lobes and a massive loss of aeration that predominates in lower lobes.In a minority of ARDS patients, the loss of aeration is homogeneously distributed. The overall lung volume of upper lobes is preserved suggesting an alveolar floodinginduced loss of aeration. In contrast, the overall lung volume of lower lobes is reduced because the heart and the abdomen exert an external compression that contributes to the loss of aeration. The P/V curve is a lung recruitment curve and the chord compliance indicates the potential for recruitment. In such patients, alveolar recruitment resulting from positive end-expiratory pressure is not accompanied by lung overinflation.In a majority of acute respiratory distress syndrome patients, upper lobes remain partially or totally aerated despite a marked regional increase in lung tissue. The upper lobes9 overall lung volume is either normal or increased, suggesting that the lung does not collapse under its own weight as generally believed. In lower lobes, the overall lung volume is reduced because the heart and the abdomen exert an external compression that contributes to the loss of aeration. The pressure/volume curve is influenced by the recruitment of poorly and nonaerated lung regions and by the mechanical properties of the part of the lung remaining aerated. In such patients, alveolar recruitment resulting from positive end-expiratory pressure w10 cmH 2 O is preceded and accompanied by lung overinflation. Eur Respir J 2003; 22: Suppl. 42, 27s- Respiratory pressure/volume (P/V) curves can be easily obtained at the bedside in critically ill patients whose lungs are mechanically ventilated. Many ventilators are now equipped with flow generators and software that allow the obtention and the analysis of the P/V curve without disconnecting the patient from mechanical ventilation. Hypothesis and concepts serving for interpreting the P/V curves of patients with acute respiratory distress syndrome (ARDS) have been deeply modified during the past 15 yrs. Initially believed to reflect the mechanical properties of the "baby" lung [1], the P/V curve is now rather considered as a lung recruitment curve [2] which is markedly influenced by the regiona...

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“…8,9 The remaining doubts are whether the advantageous postoperative effects of TEA begin intraoperatively, and whether these benefi ts outweigh the undesirable intraoperative effects of thoracic sympathetic block.…”

Section: L-3mentioning

confidence: 99%

Thoracic sympathetic block reduces respiratory system compliance

2007

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ORIGINAL ARTICLE INTRODUCTIONAdequate postoperative analgesia is considered to be a major key for reducing pul monary morbidity and improving the outcome. l-3 Thoracic epidural anesthesia (TEA) has been proposed as a reliable analgesic method following thoracic surgery.3 Most of these benefi ts, however, relate to the postoperative or to the so-called perioperative period. Some case reports have suggested that sympathetic block secon dary to thoracic or spinal anesthesia might cause impaired intraoperative ventilation by increasing airway resistance and bronchial reactivity. 4,5 A similar controversy surrounds some aspects of respiratory mechanics in anesthetized humans. Although previous studies have demonstrated that systemic local anesthetic secondary to TEA does not alter airway resistance in humans, and even attenuates bronchial hyperreactivity, 6,7 the effects of thoracic sympathetic block on respiratory mechanics, particularly on its compliance, have been poorly explained.Pressure-volume curves are a feasible method for studying respiratory system mechanics, and the use of a low-fl ow infl ation technique has been established as a reliable and quick method for obtaining these curves. 8,9 The remaining doubts are whether the advantageous postoperative effects of TEA begin intraoperatively, and whether these benefi ts outweigh the undesirable intraoperative effects of thoracic sympathetic block. OBJECTIVETo evaluate the effects of intraoperative thoracic sympathetic block on the elastic, viscoelastic and resistive properties of the respiratory system and its components (chest wall and pulmonary parenchyma), through analysis of pressure-volume curves obtained under quasi-static conditions. METHODS Patient selection Patient selectionPatients requiring pulmonary segmental resection, pulmonary lobectomy, pulmonary biopsy or mediastinal nodular resection were eligible for the study. Those classifi ed on the American Society of Anesthesiologists (ASA) scale as having a physical status score of 3 or higher were excluded, as were those presenting with moderate or severe obstructive respiratory disease, or any degree of restrictive respiratory disease, as diagnosed by spirometry and/or clinical signs. Written informed consent was obtained from each patient, and the study was approved by the hospital's Ethics Committee.Patients were randomly assigned to one of two anesthetic solutions that were injected into the epidural space: 15 ml of 0.5% bupivacaine plus epinephrine 1:200,000 and 2 mg morphine chlorohydrate (bupivacaine group), or 15 ml 0.9% NaCl plus epinephrine 1:200,000 and 2 mg morphine chlorohydrate (placebo group). Randomization and blindness were achieved by having an anesthesiologist who was not involved in the study make the draw for the two solutions by means of a randomization table that identifi ed the patients. Anesthesia AnesthesiaAll patients were administered epidural and general anesthesia. They were premedicated with 10 mg of diazepam orally the night before surgery and 0.1 mg/kg of ...

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A new simple method to perform pressure-volume curves obtained under quasi-static conditions during mechanical ventilation

Abstract: P-Vlf curves are close to P-Vst curves, are much less time-consuming, easy to acquire with Cesar ventilator equipment, and may be used in clinical routine to assess the elastic properties of the respiratory system.

Cited by 27 publications

References 19 publications

Low flow inflation pressure-time curve in patients with acute respiratory distress syndrome

Low flow inflation pressure-time curve in patients with acute respiratory distress syndrome

Pressure/volume curves and lung computed tomography in acute respiratory distress syndrome

Thoracic sympathetic block reduces respiratory system compliance

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