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Estimation of airway obstruction using oximeter plethysmograph waveform data

BACKGROUND: Validated measures to assess the severity of airway obstruction in patients with obstructive airway disease are limited. Changes in the pulse oximeter plethysmograph waveform represent fluctuations in arterial flow. Analysis of these fluctuations might be useful clinically if they represent physiologic perturbations resulting from airway obstruction. We tested the hypothesis that the severity of airway obstruction could be estimated using plethysmograph waveform data. METHODS: Using a closed airway circuit with adjustable inspiratory and expiratory pressure relief valves, airway obstruction was induced in a prospective convenience sample of 31 healthy adult subjects. Maximal change in airway pressure at the mouthpiece was used as a surrogate measure of the degree of obstruction applied. Plethysmograph waveform data and mouthpiece airway pressure were acquired for 60 seconds at increasing levels of inspiratory and expiratory obstruction. At each level of applied obstruction, mean values for maximal change in waveform area under the curve and height as well as maximal change in mouth pressure were calculated for sequential 7.5 second intervals. Correlations of these waveform variables with mouth pressure values were then performed to determine if the magnitude of changes in these variables indicates the severity of airway obstruction. RESULTS: There were significant relationships between maximal change in area under the curve (P < .0001) or height (P < 0.0001) and mouth pressure. CONCLUSION: The findings suggest that mathematic interpretation of plethysmograph waveform data may estimate the severity of airway obstruction and be of clinical utility in objective assessment of patients with obstructive airway diseases

Noninvasive assessment of asthma severity using pulse oximeter plethysmograph estimate of pulsus paradoxus physiology

<p>Abstract</p> <p>Background</p> <p>Pulsus paradoxus estimated by dynamic change in area under the oximeter plethysmograph waveform (PEP) might provide a measure of acute asthma severity. Our primary objective was to determine how well PEP correlates with forced expiratory volume in 1-second (%FEV₁) (criterion validity) and change of %FEV₁(responsiveness) during treatment in pediatric patients with acute asthma exacerbations.</p> <p>Methods</p> <p>We prospectively studied subjects 5 to 17 years of age with asthma exacerbations. PEP, %FEV₁, airway resistance and accessory muscle use were recorded at baseline and at 2 and 4 hours after initiation of corticosteroid and bronchodilator treatments. Statistical associations were tested with Pearson or Spearman rank correlations, logistic regression using generalized estimating equations, or Wilcoxon rank sum tests.</p> <p>Results</p> <p>We studied 219 subjects (median age 9 years; male 62%; African-American 56%). Correlation of PEP with %FEV₁demonstrated criterion validity (r = - 0.44, 95% confidence interval [CI], - 0.56 to - 0.30) and responsiveness at 2 hours (r = - 0.31, 95% CI, - 0.50 to - 0.09) and 4 hours (r = - 0.38, 95% CI, - 0.62 to - 0.07). PEP also correlated with airway resistance at baseline (r = 0.28 for ages 5 to 10; r = 0.45 for ages 10 to 17), but not with change over time. PEP was associated with accessory muscle use (OR 1.16, 95% CI, 1.11 to 1.21, P < 0.0001).</p> <p>Conclusions</p> <p>PEP demonstrates criterion validity and responsiveness in correlations with %FEV₁. PEP correlates with airway resistance at baseline and is associated with accessory muscle use at baseline and at 2 and 4 hours after initiation of treatment. Incorporation of this technology into contemporary pulse oximeters may provide clinicians improved parameters with which to make clinical assessments of asthma severity and response to treatment, particularly in patients who cannot perform spirometry because of young age or severity of illness. It might also allow for earlier recognition and improved management of other disorders leading to elevated pulsus paradoxus.</p

CCC meets ICU: Redefining the role of critical care of cancer patients

<p>Abstract</p> <p>Background</p> <p>Currently the majority of cancer patients are considered ineligible for intensive care treatment and oncologists are struggling to get their patients admitted to intensive care units. Critical care and oncology are frequently two separate worlds that communicate rarely and thus do not share novel developments in their fields. However, cancer medicine is rapidly improving and cancer is eventually becoming a chronic disease. Oncology is therefore characterized by a growing number of older and medically unfit patients that receive numerous novel drug classes with unexpected side effects.</p> <p>Discussion</p> <p>All of these changes will generate more medically challenging patients in acute distress that need to be considered for intensive care. An intense exchange between intensivists, oncologists, psychologists and palliative care specialists is warranted to communicate the developments in each field in order to improve triage and patient treatment. Here, we argue that "critical care of cancer patients" needs to be recognized as a medical subspecialty and that there is an urgent need to develop it systematically.</p> <p>Conclusion</p> <p>As prognosis of cancer improves, novel therapeutic concepts are being introduced and more and more older cancer patients receive full treatment the number of acutely ill patients is growing significantly. This development a major challenge to current concepts of intensive care and it needs to be redefined who of these patients should be treated, for how long and how intensively.</p

Clinical applications of photoplethysmography in paediatric intensive care

Objective: The photoplethysmographic wave is displayed by most pulse oximeters. It may be used as a non-invasive alternative to invasive arterial blood pressure trace analysis for continuous haemodynamic monitoring in selected situations. Patients and setting: Four cardiac patients treated in a tertiary neonatal-paediatric intensive care unit. Measurements: Simultaneous monitoring of the photoplethysmographic wave, ECG, and invasive blood pressure. Results and conclusions: Photoplethysmography allows for monitoring pulse rate in patients with (possible) heart rate/pulse rate dissociation (pacemaker dependency, pulsatile ventricular assist device); monitoring sudden changes in heart beat volume, which are unrelated to respiration (pulseless electrical activity, pulsus alternans); and monitoring respiratory-dependent fluctuations of the plethysmographic wave (heart failure, hypovolaemia, asthma, upper airway obstruction, pericardial effusion). Deterioration, slowly evolving over time, may be detected by this method

Pediatric cancer type predicts infection rate, need for critical care intervention, and mortality in the pediatric intensive care unit

PURPOSE: Up to 38% of children with cancer require PICU admission within three years of diagnosis, with reported PICU mortality of 13–27% far exceeding that of the general PICU population. PICU outcomes data for individual cancer types are lacking and may help identify patients at risk for poor clinical outcomes. METHODS: We performed a retrospective multi-center analysis of 10,365 PICU admissions of cancer patients ≤ 21 years old among 112 PICUs between 1/1/2009 and 6/30/2012. We evaluated the effect of cancer type, age, gender, genetic syndrome, stem cell transplantation, PRISM3 score, infections, and critical care interventions on PICU mortality. RESULTS: After excluding scheduled perioperative admissions, cancer patients represented 4.2% of all PICU admissions (10,365/246,346), had overall mortality of 6.8% (708/10,365) vs. 2.4% (5,485/230,548) in the general PICU population (RR=2.9, 95% CI 2.7–3.1, p<0.001), and accounted for 11.4% of all PICU deaths (708/6,215). Hematologic cancer patients had greater median PRISM3 score (8 vs 2, p<0.001), rates of sepsis (27% vs 9%, RR=2.9, 95% CI 2.6–3.1, p<0.001), and mortality (9.6% vs 4.5%, RR=2.1, 95% CI 1.8–2.5, p<0.001) compared to solid cancer patients. Among hematologic cancer patients, stem cell transplantation, diagnosis of acute myeloid leukemia, PRISM3 score, and infection were all independently associated with PICU mortality. CONCLUSIONS: Children with cancer account for 4.2% of PICU admissions and 11.4% of PICU deaths. Hematologic cancer patients have significantly higher admission illness severity, rates of infections, and PICU mortality than solid cancer patients. These data may be useful in risk-stratification for closer monitoring and patient counseling