Volume/pressure curve of total respiratory system in paralysed patients: artefacts and correction factors

Gattinoni, Luciano; Mascheroni, D.; Basilico, E; Foti, Giuseppe; Pesenti, Antonio; Avalli, Leonello

doi:10.1007/bf00263552

Cited by 104 publications

(43 citation statements)

References 18 publications

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“…These differences would require the application of a correction factor of about 8% (1.091-1.069 for 22-26°C ambient temperature in the NICU) to the inspired volume measured by pneumotachography. Because the expected difference is small (or even smaller as the PNT was heated) and is impossible to estimate the real conditions of the gas passing through the PNT mesh (18), it was decided not to correct the data for this source of discrepancy. Similar considerations can be referred to the different composition of the inhaled and exhaled gas, as the absorption of oxygen and the release of carbon dioxide in the alveolar gas affect the viscosity, leading to possible differences in the pressure drop across the PNT mesh.…”

Section: Discussionmentioning

confidence: 99%

Measurement of Total and Compartmental Lung Volume Changes in Newborns by Optoelectronic Plethysmography

et al. 2010

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ABSTRACT:The study of respiratory mechanics in infants requires a noninvasive accurate measurement of the lung volume changes (⌬V L ). Optoelectronic plethysmography (OEP) allows the assessment of ⌬V L through the measurement of the chest wall surface motion and it has been proved to be accurate in adults. The aim of this study was to apply OEP to newborns and to validate it by comparison to pneumotachography. Twenty term and preterm newborns (GA ϭ 34 Ϯ 5 wk) in stable condition were studied during 1 to 2 min periods of quiet breathing in supine position. Airway opening flow was measured by applying a facemask connected to a pneumotachograph (PNT) and integrated to provide the ⌬V L . Chest wall volume changes were simultaneously measured by OEP. The tidal volume values measured by pneumotachography and by OEP were compared for each breath. A total of 771 breaths from all patients were considered. Bland-Altmann analysis showed a mean difference of Ϫ0.08 mL and a limit of agreement ranging from Ϫ2.98 to 2.83 mL. Linear regression analysis demonstrated good correlation between the two techniques (r 2 ϭ 0.95, q ϭ 1.00 mL, m ϭ 0.96). OEP provides accurate measurements of ⌬V L in newborns and may be useful to study respiratory mechanics and breathing patterns during spontaneous breathing and mechanical ventilation. T he study of respiratory mechanics and control of breathing ideally requires an accurate and noninvasive measurement of lung volume changes (⌬V L ) not interfering with patients' spontaneous activity. Unfortunately, the currently available methods for the measurement of ⌬V L in infants present several intrinsic and unresolved limitations.Most of the techniques require either connections to the airway opening or critical patient-and posture-dependent calibration procedures. Connecting to the airway opening may introduce leaks, annoy the infant, and affect the breathing pattern (1,2), while the use of patient-dependent calibration procedures can lead to inaccurate measurements when a patient's condition or posture changes with respect to the baseline state (3). Moreover, none of the existing techniques have proved to be reliable in tracking long-term changes in endexpiratory lung volume (EELV) due to integration drift or problems in the measurements stability (4,5).Optoelectronic plethysmography (OEP) is a noninvasive technique, which estimates chest wall volume (V CW ) by measuring the three-dimensional position of several reflective markers placed on the patient's thorax (6 -8). This technique has proved to be reliable in adults in different postures and conditions (7,8).OEP does not require a connection to the airway opening or subject-specific calibration procedures. It provides an accurate measurement of the V CW and it allows, through the use of subsets of the markers placed on the thorax, the measurement of separate compartments, such as the rib cage, abdomen, or smaller components (9). Being based on the direct measurement of chest wall volumes, OEP is not affected by integration drift and can be use...

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Section: Discussionmentioning

confidence: 99%

Measurement of Total and Compartmental Lung Volume Changes in Newborns by Optoelectronic Plethysmography

et al. 2010

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“…In addition, discrepancies can be evidenced between gas volume changes in the syringe and the resulting increase in lung volumes measured by indirect spirometry [6,7]. When changes in lung volume are measured, using inductance plethysmography, the P/V curves exhibit a lesser degree of hysteresis (difference between the lung volumes during inflation and deflation at the same level of airway pressure) and the respiratory compliance during deflation is higher.…”

Section: Static Methodsmentioning

confidence: 99%

“…These differences are observed only if the procedure is longer than 45 s and result from the gas exchange occurring in the lung during the manoeuvre: the oxygen uptake is only partially compensated for by the carbon dioxide production and changes in lung volume are slightly smaller than those that should have resulted from the displacement of the piston in the syringe. Administration of unwarmed and unhumidified gas also causes a displacement of the curve to the left [7,8]. Because of these methodological limitations, the super-syringe method is no longer in use at the bedside.…”

Section: Static Methodsmentioning

confidence: 99%

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

Rouby¹,

Lü²,

Vieira³

2003

Eur Respir J

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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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“…Essa técnica foi largamente popularizada pelos trabalhos de Matamis e Lemaire e permitiu descrever o aspecto da curva em diferentes estágios da doença (5) . Numerosas limitações e artefatos são associados a esse método (15) . Um de seus grandes inconvenientes é a desconexão obrigatória do paciente do ventilador.…”

Section: Técnicas De Obtenção Das Curvasunclassified

“…min -1 ) liberados por um ventilador convencional. Neste trabalho (24) foram estudados, prospectivamente, 14 pacientes com diagnóstico de ALI ou SARA, submetidos à realização de curvas pressão-volume toracopulmonares, pulmo-J Pneumol 25(6) -nov-dez de 1999 nares e torácicas, obtidas pelo método da superseringa (2,5,15) , das oclusões inspiratórias múltiplas (18,19) e de dois fluxos contínuos: 3 e 6L.min -1 . Estes fluxos foram liberados pelo ventilador César usando-se os seguintes parâmetros: freqüência respiratória de 5, relação inspiração/expiração (I/E) de 80% (tempo inspiratório de 9,6 segundos) e volumes correntes de 500ml para o fluxo 3L.min -1 e 1.500 para o fluxo 9L.min -1 .…”

Section: Técnicas De Obtenção Das Curvasunclassified

Curvas de complacência ou curvas pressão-volume na insuficiência respiratória aguda

Vieira

1999

J. Pneumologia

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Volume/pressure curve of total respiratory system in paralysed patients: artefacts and correction factors

Cited by 104 publications

References 18 publications

Measurement of Total and Compartmental Lung Volume Changes in Newborns by Optoelectronic Plethysmography

Measurement of Total and Compartmental Lung Volume Changes in Newborns by Optoelectronic Plethysmography

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

Curvas de complacência ou curvas pressão-volume na insuficiência respiratória aguda

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