Bedside monitoring of lung volume available for gas exchange (original) (raw)
Related papers
European Journal of Anaesthesiology, 2014
Editor's key points † The clinical gold standard technique for cardiac output (CO) monitoring involves thermodilution via a pulmonary artery catheter. † This and other less invasive techniques suffer from several disadvantages. † The authors have developed a capnodynamic method of non-invasive estimation of CO. † They now compare the performance of their technique with that of ultrasonic and thermodilution techniques in 10 pigs.
Intensive Care Medicine, 2009
Objective To compare pressure–volume (P–V) curves obtained with the Galileo ventilator with those obtained with the CPAP method in patients with acute lung injury (ALI) or acute respiratory distress syndrome (ARDS). Design Prospective, observational study. Setting General critical care center. Patients and participants Patients with ALI/ARDS and receiving mechanical ventilation. Interventions Pressure–volume curves were obtained in random order with the CPAP technique and with the software PV Tool-2 (Galileo ventilator). Measurements and results In ten consecutive patients, airway pressure was measured by a pressure transducer and changes in lung volume were measured by respiratory inductive plethysmography. P–V curves were fitted to a sigmoidal equation with a mean R 2 of 0.994 ± 0.003. Intraclass correlation coefficients were all >0.75 (P < 0.001 at all pressure levels). Lower (LIP) and upper inflection (UIP), and deflation maximum curvature (PMC) points calculated from the fitted variables showed a good correlation between methods with intraclass correlation coefficients of 0.98 (0.92, 0.99), 0.92 (0.69, 0.98), and 0.97 (0.86, 0.98), respectively (P < 0.001 in all cases). Bias and limits of agreement for LIP (0.51 ± 0.95 cmH2O; −1.36 to 2.38 cmH2O), UIP (0.53 ± 1.52 cmH2O; −2.44 to 3.50 cmH2O), and PMC (−0.62 ± 0.89 cmH2O; −2.35 to 1.12 cmH2O) obtained with the two methods in the same patient were clinically acceptable. No adverse effects were observed. Conclusion The PV Tool-2 built into the Galileo ventilator is equivalent to the CPAP method for tracing static P–V curves of the respiratory system in critically ill patients receiving mechanical ventilation.
British Journal of Anaesthesia, 2020
Background: Bedside lung volume measurement could personalise ventilation and reduce driving pressure in patients with acute respiratory distress syndrome (ARDS). We investigated a modified gas-dilution method, the inspired sinewave technique (IST), to measure the effective lung volume (ELV) in pigs with uninjured lungs and in an ARDS model. Methods: Anaesthetised mechanically ventilated pigs were studied before and after surfactant depletion by saline lavage. Changes in PEEP were used to change ELV. Paired measurements of absolute ELV were taken with IST (ELV IST) and compared with gold-standard measures (sulphur hexafluoride wash in/washout [ELV SF6 ] and computed tomography (CT) [ELV CT ]). Measured volumes were used to calculate changes in ELV (DELV) between PEEP levels for each method (DELV IST ,
2006
Objective To examine the effects of short-term cyclic stretch on apoptosis in alveolar type II cells (A549). To study in vitro the direct influence of alveolar type II cells on mechanical stretch. Methods A549 were treated with different doses of lipopolysaccharide (LPS), 0 ng/ml, 1 ng/ml, 10 ng/ml, 100 ng/ml, 1000 ng/ml, and then A549 were lengthened 5%, 15%, 30% using a FLEXCELL tension unit 4000, a vacuum-driven device that applies strain to cells, which were cultured in six-well plates coated with collagen-I, and 12 cycles/min for 4 hours. Apoptosis was measured using the flow cytometry method that measures annexin V and propidium iodide (PI) staining. The morphological changes of apoptotic cells were observed by transmission electron microscope. Results Apoptosis could be induced in alveolar type II cells (A549) by mechanical stretch. The percentage of annexin V + PI cells increased after being treated with cyclic stretch for 4 hours by 5%, 15%, 30% in all groups. The morphological features of apoptotic cells demonstrated by transmission electron microscope were as follows: shrinkage of the cell, chromatin condensation and aggregation under the nuclear membrane as a crescent or lump, membrane-encapsulated nuclear fragment or cell organ formed by invagination of the cell membrane, and apoptotic body formation followed by vacuolization. Conclusion Apoptosis induced by mechanical stretch and LPS is dose dependent. Mechanical stretch aggravates apoptosis especially in cells treated with LPS. Annexin V and PI double staining is a specific, sensitive, and quantitative method for analyzing apoptotic cells. It is also helpful to clarify the protective mechanism of low-volume ventilation in ARDS. PaO 2 /FiO 2 430 [421; 440] # 380 [349; 397] 165 [68; 289] # C (ml/cmH 2 O) 28 [24; 32]* 18 [16; 21]* 12 [8; 17]* R i (cmH 2 O/l/s) 4.1 [3.9; 4.5] 4.5 [4.3; 5.1] 5.1 [3.7; 7.9] # P < 0.05 control vs 24-hour peritonitis, *P < 0.05 control vs 12-hour and 24-hour peritonitis.
Critical care (London, England), 2006
It is possible that taking a static pressure-volume (PV) measurement could durably affect oxygenation and thus interfere with early evaluation of a therapeutic intervention delivered just after that measurement. The aim of the present study was to investigate the effects over time of a single static PV measurement on gas exchange and haemodynamics; the PV measurements were taken using a super syringe and by using the constant flow method in patients with acute respiratory distress syndrome. We conducted a prospective, randomized and controlled interventional study in an intensive care unit. The study was conducted in 17 patients with early acute respiratory distress syndrome ventilated with a tidal volume of 6.9 +/- 1.0 ml/kg, a plateau pressure of 27 +/- 7 cmH2O and a positive end-expiratory pressure [PEEP] of 10 cmH2O. They were all evaluated for 1 hour after each of the following two measurements was taken and during a control period (in a randomized order): generation of a PV cu...
A comprehensive equation for the pulmonary pressure-volume curve
Journal of applied physiology (Bethesda, Md. : 1985), 1998
Quantification of pulmonary pressure-volume (P-V) curves is often limited to calculation of specific compliance at a given pressure or the recoil pressure (P) at a given volume (V). These parameters can be substantially different depending on the arbitrary pressure or volume used in the comparison and may lead to erroneous conclusions. We evaluated a sigmoidal equation of the form, V = a + b[1 - e-(P-c)/d]-1, for its ability to characterize lung and respiratory system P-V curves obtained under a variety of conditions including normal and hypocapnic pneumoconstricted dog lungs (n = 9), oleic acid-induced acute respiratory distress syndrome (n = 2), and mechanically ventilated patients with acute respiratory distress syndrome (n = 10). In this equation, a corresponds to the V of a lower asymptote, b to the V difference between upper and lower asymptotes, c to the P at the true inflection point of the curve, and d to a width parameter proportional to the P range within which most of th...
The physiological basis and clinical significance of lung volume measurements
Multidisciplinary Respiratory Medicine, 2017
From a physiological standpoint, the lung volumes are either dynamic or static. Both subclasses are measured at different degrees of inspiration or expiration; however, dynamic lung volumes are characteristically dependent on the rate of air flow. The static lung volumes/capacities are further subdivided into four standard volumes (tidal, inspiratory reserve, expiratory reserve, and residual volumes) and four standard capacities (inspiratory, functional residual, vital and total lung capacities). The dynamic lung volumes are mostly derived from vital capacity. While dynamic lung volumes are essential for diagnosis and follow up of obstructive lung diseases, static lung volumes are equally important for evaluation of obstructive as well as restrictive ventilatory defects. This review intends to update the reader with the physiological basis, clinical significance and interpretative approaches of the standard static lung volumes and capacities.
Intensive Care Medicine Experimental
Background Personalizing mechanical ventilation requires the development of reliable bedside monitoring techniques. The multiple-breaths nitrogen washin–washout (MBNW) technique is currently available to measure end-expiratory lung volume (EELVMBNW), but the precision of the technique may be poor, with percentage errors ranging from 28 to 57%. The primary aim of the study was to evaluate the reliability of a novel MBNW bedside system using fast mainstream sensors to assess EELV in an experimental acute respiratory distress syndrome (ARDS) model, using computed tomography (CT) as the gold standard. The secondary aims of the study were: (1) to evaluate trending ability of the novel system to assess EELV; (2) to evaluate the reliability of estimated alveolar recruitment induced by positive end-expiratory pressure (PEEP) changes computed from EELVMBNW, using CT as the gold standard. Results Seven pigs were studied in 6 experimental conditions: at baseline, after experimental ARDS and du...
Intensive Care Medicine, 2004
Objective: Measurement of functional residual capacity (FRC) during mechanical ventilation is important to standardise respiratory system compliance and adjust the ventilator settings to optimise lung recruitment. In the present study we compared three methods to measure FRC. Design: The bias flow nitrogen washout technique (FRC N2MC), the multiple breath nitrogen washout (FRC MBNW) and the multiple breath sulphur-hexafluoride washout using the molar mass signal of an ultra-sonic flow meter (FRC MBSF6) were compared in six adult monkeys after endotracheal intubation and during spontaneous breathing and mechanical ventilation at three different positive end-expiratory pressure (PEEP) levels of 0, 5 and 10 cmH 2 O. Setting: Animal research laboratory. Results: We found good agreement between all three methods and they all accurately measured changes in FRC when PEEP was increased. The coefficients of variance of the three measurement techniques were in the same range (1.3-9.2%). Conclusion: The measurement of the tracer gas concentration with the molar mass signal of the ultrasonic flow meter provides a good and simple alternative to respiratory mass spectrometer for FRC measurements in ventilated subjects.