Assessing practical skills in cardiopulmonary resuscitation: Discrepancy between standard visual evaluation and a mechanical feedback device.

This paper aims to analyze agreement in the assessment of external chest compressions (ECC) by 3 human raters and dedicated feedback software.While 54 volunteer health workers (medical transport technicians), trained and experienced in cardiopulmonary resuscitation (CPR), performed a complete sequence of basic CPR maneuvers on a manikin incorporating feedback software (Laerdal PC v 4.2.1 Skill Reporting Software) (L), 3 expert CPR instructors (A, B, and C) visually assessed ECC, evaluating hand placement, compression depth, chest decompression, and rate. We analyzed the concordance among the raters (A, B, and C) and between the raters and L with Cohen's kappa coefficient (K), intraclass correlation coefficients (ICC), Bland-Altman plots, and survival-agreement plots.The agreement (expressed as Cohen's K and ICC) was ≥0.54 in only 3 instances and was ≤0.45 in more than half. Bland-Altman plots showed significant dispersion of the data. The survival-agreement plot showed a high degree of discordance between pairs of raters (A-L, B-L, and C-L) when the level of tolerance was set low.In visual assessment of ECC, there is a significant lack of agreement among accredited raters and significant dispersion and inconsistency in data, bringing into question the reliability and validity of this method of measurement.

Low compliance with the 2 minutes of uninterrupted chest compressions recommended in the 2010 International Resuscitation Guidelines.

BACKGROUND: We aimed to analyze compliance with 2010 European guidelines' quality criteria for external chest compressions (ECC) during 2 minutes of uninterrupted cardiopulmonary resuscitation. METHODS: Seventy-two healthy nurses and physicians trained in advanced cardiopulmonary resuscitation performed 2 uninterrupted minutes of ECC on a training manikin (Resusci Anne Advanced SkillTrainer; Laerdal Medical AS, Stavanger, Norway) that enabled us to measure the depth and rate of ECC. When professionals agreed to participate in the study, we recorded their age, body mass index (BMI), smoking habit, and their own subjective estimation of their physical fitness. To measure fatigue, we analyzed participants' heart rates, percentage of maximum tolerated heart rate (MHR), and subjective perception of their fatigue on a visual analog scale. RESULTS: Nearly half (48.6%) the rescuers failed to achieve a minimum average ECC depth of 50 mm. Only 48.1% of ECCs fulfilled the 2010 guidelines' quality criteria; quality deteriorated mainly after the first minute. Poor ECC quality and deteriorating quality after the first minute were associated with BMI < 23 kg/m(2). Rescuers with BMI ≥ 23 kg/m(2) fulfilled the quality criteria throughout the 2 minutes, whereas those with BMI < 23 kg/m(2) fulfilled them for 80% of ECCs during the first minute, but for only 30% at the end of the 2 minutes. CONCLUSIONS: Compliance with the 2010 guidelines' quality criteria is often poor, mainly due to lack of proper depth. The greater depth recommended in the 2010 guidelines with respect to previous guidelines requires greater force, so BMI < 23 kg/m(2) could hinder compliance. Limiting each rescuer's uninterrupted time doing ECC to 1 minute could help ensure compliance.

Procalcitonin for diagnosis of bacterial pneumonia in critically ill patients during 2009 H1N1 influenza pandemic: a prospective cohort study, systematic review and individual patient data meta-analysis.

INTRODUCTION: Procalcitonin (PCT) is helpful for diagnosing bacterial infections. The diagnostic utility of PCT has not been examined thoroughly in critically ill patients with suspected H1N1 influenza. METHODS: Clinical characteristics and PCT were prospectively assessed in 46 patients with pneumonia admitted to medical ICUs during the 2009 and 2010 influenza seasons. An individual patient data meta-analysis was performed by combining our data with data from five other studies on the diagnostic utility of PCT in ICU patients with suspected 2009 pandemic influenza A(H1N1) virus infection identified by performing a systematic literature search. RESULTS: PCT levels, measured within 24 hours of ICU admission, were significantly elevated in patients with bacterial pneumonia (isolated or coinfection with H1N1; n = 77) (median = 6.2 µg/L, interquartile range (IQR) = 0.9 to 20) than in patients with isolated H1N1 influenza pneumonia (n = 84; median = 0.56 µg/L, IQR = 0.18 to 3.33). The area under the curve of the receiver operating characteristic curve of PCT was 0.72 (95% confidence interval (CI) = 0.64 to 0.80; P < 0.0001) for diagnosis of bacterial pneumonia, but increased to 0.76 (95% CI = 0.68 to 0.85; P < 0.0001) when patients with hospital-acquired pneumonia and immune-compromising disorders were excluded. PCT at a cut-off of 0.5 µg/L had a sensitivity (95% CI) and a negative predictive value of 80.5% (69.9 to 88.7) and 73.2% (59.7 to 84.2) for diagnosis of bacterial pneumonia, respectively, which increased to 85.5% (73.3 to 93.5) and 82.2% (68.0 to 92.0) in patients without hospital acquired pneumonia or immune-compromising disorder. CONCLUSIONS: In critically ill patients with pneumonia during the influenza season, PCT is a reasonably accurate marker for detection of bacterial pneumonia, particularly in patients with community-acquired disease and without immune-compromising disorders, but it might not be sufficient as a stand-alone marker for withholding antibiotic treatment.

Antibiotic prescription patterns in the empiric therapy of severe sepsis: combination of antimicrobials with different mechanisms of action reduces mortality.

INTRODUCTION: Although early institution of adequate antimicrobial therapy is lifesaving in sepsis patients, optimal antimicrobial strategy has not been established. Moreover, the benefit of combination therapy over monotherapy remains to be determined. Our aims are to describe patterns of empiric antimicrobial therapy in severe sepsis, assessing the impact of combination therapy, including antimicrobials with different mechanisms of action, on mortality. METHODS: This is a Spanish national multicenter study, analyzing all patients admitted to ICUs who received antibiotics within the first 6 hours of diagnosis of severe sepsis or septic shock. Antibiotic-prescription patterns in community-acquired infections and nosocomial infections were analyzed separately and compared. We compared the impact on mortality of empiric antibiotic treatment, including antibiotics with different mechanisms of action, termed different-class combination therapy (DCCT), with that of monotherapy and any other combination therapy possibilities (non-DCCT). RESULTS: We included 1,372 patients, 1,022 (74.5%) of whom had community-acquired sepsis and 350 (25.5%) of whom had nosocomial sepsis. The most frequently prescribed antibiotic agents were ß-lactams (902, 65.7%) and carbapenems (345, 25.1%). DCCT was administered to 388 patients (28.3%), whereas non-DCCT was administered to 984 (71.7%). The mortality rate was significantly lower in patients administered DCCTs than in those who were administered non-DCCTs (34% versus 40%; P = 0.042). The variables independently associated with mortality were age, male sex, APACHE II score, and community origin of the infection. DCCT was a protective factor against in-hospital mortality (odds ratio (OR), 0.699; 95% confidence interval (CI), 0.522 to 0.936; P = 0.016), as was urologic focus of infection (OR, 0.241; 95% CI, 0.102 to 0.569; P = 0.001). CONCLUSIONS: ß-Lactams, including carbapenems, are the most frequently prescribed antibiotics in empiric therapy in patients with severe sepsis and septic shock. Administering a combination of antimicrobials with different mechanisms of action is associated with decreased mortality.

Procalcitonin levels are lower in intensive care unit patients with H1N1 influenza A virus pneumonia than in those with community-acquired bacterial pneumonia. A pilot study.

PURPOSE: The purpose of the study was to know the kinetics of procalcitonin (PCT), C-reactive protein (CRP), and white blood cell (WBC) in critically ill patients with H1N1 influenza A virus pneumonia and to compare levels of these inflammatory mediators with patients with acute community-acquired bacterial pneumonia. MATERIALS AND METHODS: An observational study in a mixed intensive care unit (ICU) at a general university hospital was performed. All consecutive patients admitted to the ICU with a diagnosis of severe acute community-acquired pneumonia from September 2009 to December 2009 were included. Viral (H1N1 influenza A) and bacterial microbiological diagnoses were done in every patient. At admission, demographics, comorbidities, Simplified Acute Physiology Score, Sequential Organ Failure Assessment, Lung Injury Score, and Pao(2)/Fio(2) were recorded. At admission and after 24, 48, and 120 hours, WBC, CRP, and PCT levels were obtained. Finally, hospital and ICU length of stay and mortality were recorded. RESULTS: No differences in CRP or WBC were found between H1N1-positive patients and H1N1-negative patients (patients with acute community-acquired bacterial pneumonia). Procalcitonin levels at admission were lower in H1N1-positive patients (PCT = 0.4 [0.1-6.1] ng/mL) than in the H1N1-negative patients (24.8 [13.1-34.5] ng/mL). Procalcitonin significantly decreased with time but remained lower in the H1N1-positive group at all measurements (P < .05 for all comparisons). CONCLUSIONS: Among patients admitted to the ICU with pneumonia, the PCT level could help identify H1N1 influenza A virus pneumonia and thus enable earlier antiviral therapy.

[Intraabdominal hypertension and abdominal compartment syndrome]. / Hipertensión intraabdominal y síndrome compartimental abdominal.

Although intraabdominal pressure (IAP) has been studied for more than 100 years, the concepts of intraabdominal hypertension (IAH) and abdominal compartmental syndrome (ACS) have only been developed as clinical entities of interest in intensive care in the last 5 years. At the first Congress on Abdominal Compartment Syndrome in December 2004, a series of definitions were established, which were published in 2006. IAH is defined as IAP ≥ 12 mmHg and is classified in four severity grades, the maximum grade being ACS, with the development of multiorgan failure. The incidence of IAH in patients in intensive care units is high, around 30% at admission and 64% in those with a length of stay of 7 days. The increase in IAP leads to reduced vascular flow to the splenic organs, increased intrathoracic pressure and decreased venous return, with a substantial reduction in cardiac output. If IAH persists, these physiopathologic episodes are followed by the development of multiorgan failure with renal, cardiocirculatory and respiratory failure and intestinal ischemia. Mortality from untreated ACS is higher than 60%. The only treatment for ACS is surgical decompression. In patients with moderate IAH, medical treatment should be optimized, based on the following measures: a) serial IAP monitoring; b) optimization of systemic perfusion and the function of the distinct systems in patients with high IAP; c) instauration of specific measures to decrease IAP; and d) early surgical decompression for refractory IAH. The application of the medical measures that can reduce IAP and early abdominal decompression in ACS improve survival in critically ill patients with IAH.

Hemodynamic effects of recombinant human activated protein C in patients with septic shock.

PURPOSE: The aim of this study is to examine the effects of recombinant human activated protein C (rhAPC) on hemodynamic parameters in patients with septic shock. METHODS: This is a retrospective study of 2 university-hospital critical care units. Patients with septic shock with pulmonary artery catheterization or transthoracic thermodilution monitoring were studied. We matched patients with septic shock with at least 2 organ failures (18 treated with rhAPC and 18 controls) on sex, age, sequential organ failure assessment (SOFA), Acute Physiology and Chronic Health Evaluation (APACHE) II, and sepsis etiology. We recorded norepinephrine dose and hemodynamic parameters at baseline and 24, 36, and 48 hours after the real or theoretical start of rhAPC treatment. RESULTS: Mean arterial pressure remained stable in both groups. In rhAPC patients, norepinephrine requirements, initially higher than in controls, were significantly lower at 48 hours, and stroke volume at 24 and 48 hours improved (P < .05). CONCLUSION: Recombinant human activated protein C use correlated with improved hemodynamic parameters and decreased norepinephrine requirements. The retrospective nature of the study limits the strength of these findings.

A new automated method versus continuous positive airway pressure method for measuring pressure-volume curves in patients with acute lung injury.

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 cmH(2)O; -1.36 to 2.38 cmH(2)O), UIP (0.53 +/- 1.52 cmH(2)O; -2.44 to 3.50 cmH(2)O), and PMC (-0.62 +/- 0.89 cmH(2)O; -2.35 to 1.12 cmH(2)O) 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.

Effects of vascular flow and PEEP in a multiple hit model of lung injury in isolated perfused rabbit lungs.

BACKGROUND: High vascular flow aggravates lung damage in animal models of ventilator-induced lung injury. Positive end-expiratory pressure (PEEP) can attenuate ventilator-induced lung injury, but its continued effectiveness in the setting of antecedent lung injury is unclear. The objective of the present study was to evaluate whether the application of PEEP diminishes lung injury induced by concurrent high vascular flow and high alveolar pressures in normal lungs and in a preinjury lung model. METHODS: Two series of experiments were performed. Fifteen sets of isolated rabbit lungs were randomized into three groups (n = 5): low vascular flow/low PEEP; high vascular flow/low PEEP, and high vascular flow/high PEEP. Subsequently, the same protocol was applied in an additional 15 sets of isolated rabbit lungs in which oleic acid was added to the vascular perfusate to produce mild to moderate lung injury. All lungs were ventilated with peak airway pressure of 30 cm H2O for 30 minutes. Outcome measures included frequency of gross structural failure, pulmonary hemorrhage, edema formation, changes in static compliance, pulmonary vascular resistance, and pulmonary ultrafiltration coefficient. RESULTS: In the context of high vascular flow, application of a moderate level of PEEP reduced pulmonary rupture, edema formation, and lung hemorrhage. The protective effects of PEEP were not observed in lungs concurrently injured with oleic acid. CONCLUSIONS: Under these experimental conditions, PEEP attenuates lung injury in the setting of high vascular flow. The protective effect of PEEP is lost in a two-hit model of lung injury.

Peripheral arterial blood pressure monitoring adequately tracks central arterial blood pressure in critically ill patients: an observational study.

INTRODUCTION: Invasive arterial blood pressure monitoring is a common practice in intensive care units (ICUs). Accuracy of invasive blood pressure monitoring is crucial in evaluating the cardiocirculatory system and adjusting drug therapy for hemodynamic support. However, the best site for catheter insertion is controversial. Lack of definitive information in critically ill patients makes it difficult to establish guidelines for daily practice in intensive care. We hypothesize that peripheral and central mean arterial blood pressures are interchangeable in critically ill patients. METHODS: This is a prospective, observational study carried out in a surgical-medical ICU in a teaching hospital. Fifty-five critically ill patients with clinical indication of invasive arterial pressure monitoring were included in the study. No interventions were made. Simultaneous measurements were registered in central (femoral) and peripheral (radial) arteries. Bias and precision between both measurements were calculated with Bland-Altman analysis for the whole group. Bias and precision were compared between patients receiving high doses of vasoactive drugs (norepinephrine or epinephrine >0.1 microg/kg/minute or dopamine >10 microg/kg/minute) and those receiving low doses (norepinephrine or epinephrine <0.1 microg/kg/minute or dopamine <10 microg/kg/minute). RESULTS: Central mean arterial pressure was 3 +/- 4 mmHg higher than peripheral mean arterial pressure for the whole population and there were no differences between groups (3 +/- 4 mmHg for both groups). CONCLUSION: Measurement of mean arterial blood pressure in radial or femoral arteries is clinically interchangeable. It is not mandatory to cannulate the femoral artery, even in critically ill patients receiving high doses of vasoactive drugs.

Contributions of vascular flow and pulmonary capillary pressure to ventilator-induced lung injury.

OBJECTIVE: To evaluate the influence of vascular flow on ventilator-induced lung injury independent of vascular pressures. DESIGN: Laboratory study. SETTING: Hospital laboratory. SUBJECTS: Thirty-two New Zealand White rabbits. INTERVENTIONS: Thirty-two isolated perfused rabbit lungs were allocated into four groups: low flow/low pulmonary capillary pressure; high flow/high pulmonary capillary pressure; low flow/high pulmonary capillary pressure, and high flow/low pulmonary capillary pressure. All lungs were ventilated with peak airway pressure 30 cm H2O and positive end-expiratory pressure 5 cm H2O for 30 mins. MEASUREMENTS AND MAIN RESULTS: Outcome measures included frequency of gross structural failure (pulmonary rupture), pulmonary hemorrhage, edema formation, changes in lung compliance, pulmonary vascular resistance, and pulmonary ultrafiltration coefficient. Lungs exposed to high pulmonary vascular flow ruptured more frequently, displayed more hemorrhage, developed more edema, suffered larger decreases in compliance, and had larger increases in vascular resistance than lungs exposed to low vascular flows (p < .05 for each pairwise comparison between groups). CONCLUSIONS: These findings suggest that high pulmonary vascular flows might exacerbate ventilator-induced lung injury independent of their effects on pulmonary vascular pressures.

Massive brain injury enhances lung damage in an isolated lung model of ventilator-induced lung injury.

OBJECTIVE: To assess the influence of massive brain injury on pulmonary susceptibility to injury attending subsequent mechanical or ischemia/reperfusion stress. DESIGN: Prospective experimental study. SETTING: Animal research laboratory. SUBJECTS: Twenty-four anesthetized New Zealand White rabbits randomized to control (n = 12) or induced brain injury (n = 12) group. INTERVENTIONS: After randomization, brain injury was induced by inflation of an intracranial balloon-tipped catheter, and animals were ventilated with a tidal volume of 10 mL/kg and zero end-expiratory pressure for 120 mins. Following heart-lung block extraction, isolated and perfused lungs were subjected to injurious ventilation with peak airway pressure 30 cm H2O and positive end-expiratory pressure 5 cm H2O for 30 mins. MEASUREMENTS AND MAIN RESULTS: No difference was observed between groups in gas exchange, lung mechanics, or hemodynamics during the 2-hr in vivo period following induction of brain injury. However, after 30 mins of ex vivo injurious mechanical ventilation, lungs from the brain injury group showed greater change in ultrafiltration coefficient, weight gain, and alveolar hemorrhage (all p < .05). CONCLUSIONS: Massive brain injury might increase lung vulnerability to subsequent injurious mechanical or ischemia-reperfusion insults, thereby increasing the risk of clinical posttransplant graft failure.

Intramucosal-arterial Pco2 gradient does not reflect intestinal dysoxia in anemic hypoxia.

BACKGROUND: An increase in intramucosal-arterial Pco2 gradient (DeltaPco2) might be caused by tissue hypoxia or by diminished blood flow. Our hypothesis was that DeltaPco2 should not be altered in anemic hypoxia with preserved blood flow. METHODS: In 18 anesthetized, mechanically ventilated sheep, oxygen transport was stepwise reduced by hemorrhage (hypovolemia, n = 9) or by hemorrhage and simultaneous dextran infusion (hemodilution, n = 9). RESULTS: Hypovolemia and hemodilution produced comparable decreases in systemic and intestinal oxygen transport and uptake. However, mixed venoarterial and mesenteric venoarterial Pco2 gradients and DeltaPco2 were significantly higher in hypovolemia than in hemodilution (25 +/- 5 vs. 10 +/- 2 mm Hg; 21 +/- 6 vs. 10 +/- 5 mm Hg; and 41 +/- 18 vs. 14 +/- 9 mm Hg, respectively; p < 0.01). CONCLUSION: DeltaPco2 did not reflect intestinal dysoxia during Vo2/Do2 dependency attributable to hemodilution. Blood flow seems to be the main determinant of DeltaPco2.

Changes in lung volume with three systems of endotracheal suctioning with and without pre-oxygenation in patients with mild-to-moderate lung failure.

OBJECTIVE: To compare changes in lung volume, oxygenation, airway pressure, and hemodynamic effects induced by suctioning with three systems in critically ill patients with mild-to-moderate lung disease, and also to evaluate the effects of hyperoxygenation applied prior to the maneuver as suggested by some guidelines. DESIGN: Prospective crossover study. SETTING: General intensive care department of a university-affiliated hospital. PATIENTS: Ten mechanically ventilated patients with mild-to-moderate acute respiratory failure. INTERVENTIONS: Patients were ventilated in volume control mode with a mean tidal volume of 490+/-88 ml, PEEP 7+/-4 cmH2O and FiO(2) 0.36+/-0.05. Suctioning was performed sequentially with a quasi-closed system, with an open system 10 min later, and finally with a closed system. Thereafter, pure oxygen was applied for 2 min and the whole suctioning sequence was repeated in reverse order. MEASUREMENTS AND MAIN RESULTS: Patients' mean PaO(2)/FiO(2) ratio was 273+/-28 mmHg. The reductions in lung volume during suctioning were similar with the quasi-closed (386+/-124 ml) and closed system (497+/-338 ml), but significantly higher with the open system (1281+/-656 ml, P=0.022). We found no significant hemodynamic adverse effects, and no significant SpO(2) reductions with all the studied suctioning techniques. Pre-oxygenation with pure oxygen did not induce additive effects in lung volume changes. With and without pre-oxygenation, lung volume returned to baseline in every patient within 10 min. CONCLUSIONS: Suctioning with closed and quasi-closed systems reduces the substantial losses in lung volume observed with the open system. Nevertheless, in patients without severe lung disease these changes were transient and rapidly reversible.

Clinical review: the implications of experimental and clinical studies of recruitment maneuvers in acute lung injury.

Mechanical ventilation can cause and perpetuate lung injury if alveolar overdistension, cyclic collapse, and reopening of alveolar units occur. The use of low tidal volume and limited airway pressure has improved survival in patients with acute lung injury or acute respiratory distress syndrome. The use of recruitment maneuvers has been proposed as an adjunct to mechanical ventilation to re-expand collapsed lung tissue. Many investigators have studied the benefits of recruitment maneuvers in healthy anesthetized patients and in patients ventilated with low positive end-expiratory pressure. However, it is unclear whether recruitment maneuvers are useful when patients with acute lung injury or acute respiratory distress syndrome are ventilated with high positive end-expiratory pressure, and in the presence of lung fibrosis or a stiff chest wall. Moreover, it is unclear whether the use of high airway pressures during recruitment maneuvers can cause bacterial translocation. This article reviews the intrinsic mechanisms of mechanical stress, the controversy regarding clinical use of recruitment maneuvers, and the interactions between lung infection and application of high intrathoracic pressures.

Application of continuous positive airway pressure to trace static pressure-volume curves of the respiratory system.

OBJECTIVE: To evaluate a new technique for pressure-volume curve tracing. DESIGN: Prospective experimental study. SETTING: Animal research laboratory. SUBJECTS: Six anesthetized rats. INTERVENTIONS: Two pressure-volume curves were obtained by means of the super-syringe method (gold standard) and the continuous positive airway pressure (CPAP) method. For the CPAP method, the ventilator was switched to CPAP and the pressure level was raised from 0 to 50 cm H2O in 5 cm H2O steps and then decreased, while we measured lung volume using respiratory inductive plethysmography. Thereafter, lung injury was induced using very high-volume ventilation. Following injury, two further pressure-volume curves were traced. Pressure-volume pairs were fitted to a mathematical model. MEASUREMENTS AND MAIN RESULTS: Pressure-volume curves were equivalent for each method, with intraclass correlation coefficients being higher than.75 for each pressure level measured. Bias and precision for volume values were 0.46 +/- 0.875 mL in basal measurements and 0.31 +/- 0.67 mL in postinjury conditions. Lower and upper inflection points on the inspiratory limb and maximum curvature point on the deflation limb obtained using both methods and measured by regression analysis also were correlated, with intraclass correlation coefficients (95% confidence interval) being.97 (.58,.99),.85 (.55,.95), and.94 (.81,.98) (p <.001 for each one). When inflection points were estimated by observers, the correlation coefficient between methods was.90 (.67,.98) for lower inflection points (p <.001). However, estimations for upper inflection points and maximum curvature point were significantly different. CONCLUSIONS: The CPAP method for tracing pressure-volume curves is equivalent to the super-syringe method. It is easily applicable at the bedside, avoids disconnection from the ventilator, and can be used to obtain both the inspiratory and the deflation limbs of the pressure-volume curve. Use of regression techniques improves determination of inflection points.