NICaS Dyspnea Event Monitoring, UK
Physiology of Dyspnea (difficulty breathing):
Dyspnea is a stronger predictor of death than chest pain.1 As shown in Figure 1 below, it may be caused by cardiac and/or noncardiac conditions, which presents challenges to physicians to accurately determine its cause.
Figure 1. Potential causes of Dyspnea.2
Objective data can lead to better outcomes and decreased cost of care.
NICaSTM provides data that directly or indirectly relate to cardiac and noncardiac causes of dyspnea. When physicians have access to these objective data, they can make more accurate diagnoses,3 utilize these data to guide therapy,4 achieve better outcomes,4 decrease cost of care,5 and identify heart failure patients at high risk of hospital readmission6,7.
NICaSTM Status Report:
An example of a NICaSTM Status report from a patient complaining of dyspnea is shown in Figure 2. The NICaSTM data reveal that this patient has poor cardiac performance: low stroke volume, stroke index, cardiac output, cardiac index, Granov-Goor index, and cardiac power index. These objective data certainly have diagnostic implications.
Figure 2. NICaSTM Status report of a patient complaining of dyspnea.
Studies by Springfield, et al.3, and Lo, et al.8, clearly demonstrated that for patients complaining of dyspnea, diagnoses based upon data from a bioimpedance device similar to NICaSTM (BioZ by CardioDynamics), were more accurate than diagnoses based upon traditional history, physical, and lab results by the attending physicians in an Emergency Department. More specifically, when the following bioimpedance criteria were utilized to make a diagnosis,
- Cardiac: CI < 2.4 or CI < 3.0 and STR > 0.55
- Noncardiac: > 3.0 or CI 2.4 - 2.9 and STR < 0.55 [STR is Systolic Time Ratio and is the ratio of PreEjection Period / Left Ventricular Ejection Time]
The diagnoses based upon the bioimpedance data were more accurate than the attending physicians' diagnoses, when compared to the final diagnoses by a board certified emergency physician, who was blinded to the bioimpedance data. The results of this study are summarized below in Figure 3.
Figure 3. Comparison of accuracy of diagnoses based upon ICG (bioimpedance)and Emergency Department Physicians to the final diagnosis by a board certified Emergency Room Physician.
- Sensitivity = probability that a person with a true cardiac cause will test cardiac by the method.
- Specificity = probability that a person with a true noncardiac cause will test noncardiac by the method.
- PPV = Positive Predictive Value, the probability that a person who tests cardiac is truly a cardiac cause.
- NPV = Negative Predictive Value, the probability that a person who tests noncardiac is truly a noncardiac cause.
Related Clinical Studies:
Academic Emerg Med 06 Impact Of Impedance Cardiography On Diagnosis Andtherapy Of Emergent Dyspnea
- Abidov A, et al. N Engl J Med 2005;353:1889-98.
- Adapted from Braunwald, E. Heart Disease: A Textbook of Cardiovascular Medicine. Philadelphia, Saunders (6th ed). 2001, 28-31.
- Springfield, CL, et al. CHF; 10(2 suppl2):14-16.
- Smith, RD, et al. Hypertension. 2006; 47:769-775.
- Ferrario, CM, et al. Am Heart Hosp J. 2006; 4:279-289.
- Packer, M, et al. J Am Coll Cardiol 2006; 47:2245-52.
- Tanino, Y, et al. Circulation Journal2009; 73: 1074 - 1079
- Lo, HY, et al. Am. J. Emergency Medicine (2007) 25, 437-441