Jafar Vossoughi

Variation of Respiratory Resistance Suggests Optimization of Airway Caliber

Physiologically optimized processes, such as respiration, walking, and cardiac function, usually show a range of variability about the optimized value. Airway resistance has, in the past, been noted as variable, and this variability has been connected to pulmonary disease (e.g., asthma). A hypothesis was presented many years ago that postulated airway resistance as an optimized parameter in healthy individuals, and we have noticed that respiratory measurements made with the airflow perturbation device (APD) tend to be variable in nature. It was posited that this variability indicates that respiratory resistance is optimized similarly to other physiological processes. Fifty subjects with a wide range of demographics volunteered to have 100 measurements made of their respiratory resistances. Resistances were separated into inhalation and exhalation phases. These were plotted and shown to have frequency distributions that were consistent with expectations for an optimized process. The frequency distributions were not quite symmetrical, being skewed slightly toward upper resistances. Comparison between subject data and data from a mechanical respiratory analog showed that subject resistance variation is overwhelmingly from the respiratory system and not from the APD.

Comparison of Respiratory Resistance Measurements Made with an Airflow Perturbation Device with Those from Impulse Oscillometry.

The airflow perturbation device (APD) has been developed as a portable, easy to use, and a rapid response instrument for measuring respiratory resistance in humans. However, the APD has limited data validating it against the established techniques. This study used a mechanical system to simulate the normal range of human breathing to validate the APD with the clinically accepted impulse oscillometry (IOS) technique. The validation system consisted of a sinusoidal flow generator with ten standardized resistance configurations that were shown to represent a total range of resistances from 0.12 to 0.95 kPa·L−1 ·s (1.2–9.7 cm H2O·L−1 ·s). Impulse oscillometry measurements and APD measurements of the mechanical system were recorded and compared at a constant airflow of 0.15 L·s−1. Both the IOS and APD measurments were accurate in assessing nominal resistance. In addition, a strong linear relationship was observed between APD measurements and IOS measurements (R 2 = 0.999). A second series of measurements was made on ten human volunteers with external resistors added in their respiratory flow paths. Once calibrated with the mechanical system, the APD gave respiratory resistance measurements within 5% of IOS measurements. Because of their comparability to IOS measurements, APD measurements are shown to be valid representations of respiratory resistance.

Validity of a new respiratory-resistance measurement device to detect glottal-area change

OBJECTIVE To determine the correlation between respiratory resistance (Rr) values measured with the Airflow Perturbation Device (APD) to laryngoscopic images of glottal area (GA) in feigned paradoxical vocal fold motion (PVFM), also known as vocal cord dysfunction. HYPOTHESIS There is a strong inverse relationship between Rr and GA such that laryngeal constriction can be detected and quantified by APD-measured Rr. STUDY DESIGN Prospective, single subject study. METHODS A healthy adult feigned breathing that was characteristic of PVFM. Rr and GA were simultaneously recorded, synchronized, and analyzed for three complete breathing cycles with significant glottal constriction occurring during inspiration. RESULTS Cross-correlation analysis revealed a strong negative correlation (-0.824) between GA and Rr during feigned PVFM breathing such that Rr increased when GA decreased. CONCLUSION APD-measured Rr appears to be a viable noninvasive method for diagnostic screening and monitoring of treatment outcomes for individuals presenting with dyspnea related to PVFM.

Test–Retest Reliability of Respiratory Resistance Measured With the Airflow Perturbation Device

PURPOSE In this study, the authors aimed to determine reliability of the airflow perturbation device (APD) to measure respiratory resistance within and across sessions during resting tidal (RTB) and postexercise breathing in healthy athletes, and during RTB across trials within a session in athletes with paradoxical vocal fold motion (PVFM) disorder. METHOD Prospective, repeated-measures design. The APD measured respiratory resistance during 3 baseline assessments in 24 teenage female athletes, 12 with and 12 without PVFM. Control athletes provided data at rest and following a customized exercise challenge during each of 3 sessions. Intraclass correlation coefficient (ICC) analysis assessed strength of relationships, and repeated-measures analysis of variance assessed differences across trials and sessions. RESULTS ICC analyses confirmed strong correlations across RTB trials for inspiratory, expiratory, and mean respiratory resistance in both groups. Inspiratory resistance decreased ~5% between sessions for control participants; expiratory and mean respiratory resistances were stable. Data from control athletes across sessions and following rigorous exercise were strongly correlated when taken at comparable intervals. CONCLUSIONS APD-measured respiratory resistance, including separate assessments for the inspiratory and expiratory phases, has strong test-retest reliability during RTB and after exercising. This suggests that the APD is a useful measurement tool for the assessment of airway function in patients suspected of having PVFM.

Inspiratory and expiratory resistances during exercise.

Aims: Paradoxical vocal fold motion, especially during exercise, causes symptoms of dyspnea in patients experiencing this condition. At present, the standard means to diagnose this condition is invasive using a laryngoscope. The Airflow Perturbation Device (APD) could offer a simpler means of diagnosis and monitoring, but the APD must be validated with laryngoscopy. Both devices require access to the mouth, and so cannot be used simultaneously. The aim of this study was to determine if respiratory resistance of exercising subjects changes immediately after exercise begins and ends. Study Design: The study was conducted as a prospective study. Place and Duration of Study: All tests were conducted in the Human Performance Laboratory, Fischell Department of Bioengineering, University of Maryland, College Park, MD between August 2011 and August 2012. Methodology: Fifteen subjects exercised on a bicycle ergometer at 70% of maximum predicted heart rate while breathing through the APD. Results: Results show that APD measurements made just prior and after the cessation of Research Article AArticleArticle... ......... Article British Journal of Medicine & Medical Research, 3(4): 1222-1232, 2013 1223 exercise are comparable. Conclusion: APD measured inspiration and expiration resistances do not change immediately after exercise cessation.

In-Home Hand-Held Device to Measure Respiratory Resistance

A small hand-held Airflow Perturbation Device (APD) has been developed that is capable of noninvasively evaluating respiratory resistance. The APD has several advantages over commercially available spirometers. The APD is small, compact, self-contained, and low cost. It can measure respiratory resistance noninvasively in inhalation and exhalation accurately and reliably. Because of its size, cost, and ease of operation, it can be a suitable diagnostic device for home use

Influence of Nasal Congestion on Respiratory Resistance Values

Nasal congestion is the fourth most common minor ailment presented in primary care and as such, a method to quantify the meaning of nasal congestion in order to enable evaluation of medicines catered to specific congestion levels can prove important. The Airflow Perturbation Device (APD) is a noninvasive respiratory diagnostic device that evaluates the respiratory resistance in humans. It measures the total respiratory resistance under normal breathing in less than one minute. This study involved using the APD to determine the influence of nasal congestion on respiratory resistance in a laboratory setting. A total of 25 volunteers volunteered for this study and it employed a standard subjective categorical scale for nasal congestion (i.e. No Congestion, Mild Congestion, Moderate Congestion, and Severe Congestion). The results show that resistance values increased with increased congestion levels. However, resistance values of the groups of volunteers for the various congestion categories overlapped, and there were no statistically significant values differentiating no congestion and mild congestion or moderate congestion and severe congestion.

A Rapid, Handheld Device to Assess Respiratory Resistance: Clinical and Normative Evidence

Introduction Following reports of respiratory symptoms among service members returning from deployment to South West Asia (SWA), an expert panel recommended pre-deployment spirometry be used to assess disease burden. Unfortunately, testing with spirometry is high cost and time-consuming. The airflow perturbation device (APD) is a handheld monitor that rapidly measures respiratory resistance (APD-Rr) and has promising but limited clinical data. Its speed and portability make it ideally suited for large volume pre-deployment screening. We conducted a pilot study to assess APD performance characteristics and develop normative values. Materials and Methods We prospectively enrolled subjects and derived reference equations for the APD from those without respiratory symptoms, pulmonary disease, or tobacco exposure. APD testing was conducted by medical technicians who received a 10-min in-service on its use. A subset of subjects performed spirometry and impulse oscillometry (iOS), administered by trained respiratory therapists. APD measures were compared with spirometry and iOS. Results The total study population included 199 subjects (55.8% males, body mass index 27.7 ± 6.0 kg/m2, age 49.9 ± 18.7 yr). Across the three APD trials, mean inspiratory (APD-Ri), expiratory (APD-Re), and average (APD-Ravg) resistances were 3.30 ± 1.0, 3.69 ± 1.2, and 3.50 ± 1.1 cm H2O/L/s. Reference equations were derived from 142 clinically normal volunteers. Height, weight, and body mass index were independently associated with APD-Ri, APD-Re, and APD-Ravg and were combined with age and gender in linear regression models. APD-Ri, APD-Re, and APD-Ravg were significantly inversely correlated with FEV1 (r = -0.39 to -0.42), FVC (r = -0.37 to -0.40), and FEF25-75 (r = -0.31 to -0.35) and positively correlated with R5 (r = 0.61-0.62), R20 (r = 0.50-0.52), X5 (r = -0.57 to -0.59), and FRES (r = 0.42-0.43). Bland-Altman plots showed that the APD-Rr closely approximates iOS when resistance is normal. Conclusion Rapid testing was achieved with minimal training required, and reference equations were constructed. APD-Rr correlated moderately with iOS and weakly with spirometry. More testing is required to determine whether the APD has value for pre- and post-deployment respiratory assessment.

An Effortless Noninvasive Respiratory Diagnostic Device

During the past decade the mortality and morbidity due to pulmonary diseases ranked number 2 or 3, the current data projection suggests that COPD (Chronic Obstructive Pulmonary Disease) alone will be the third cause of death worldwide by 2020. Before a respiratory disorder can be treated, it has to be diagnosed. Currently a variety of respiratory diagnostic devices/systems exists. Spirometer is the most common and frequently used respiratory diagnostic device, whereas plethysmograph (Bodybox) and Impulse Oscillometer (IOS) are more sophisticated systems. We have developed a simple, portable, and inexpensive respiratory diagnostic device, Airflow Perturbation Device (APD), that can evaluate the respiratory resistance noninvasively and effortlessly. It is based on normal breathing with no effort from the subject beyond simple breathing into the APD for less than one minute. APD measures the respiratory pressure (in mmHg) and flow (Liter per second), the ratio of the respiratory pressure over respiratory flow is the resistance of the respiratory system (mmHg/L/s). APD has been favorably compared with spirometer, plethysmograph, and IOS. The respiratory resistance value is highly age dependent, it is fairly high for children and infants (60 - 3 mmHg/L/s) and assumes low values in adulthood (2.5-2 mmHg/L/s). We have evaluated the respiratory resistance values for over 3,000 normal subjects and those with a variety of pulmonary disorders such as asthma, COPD, Vocal Fold Dysfunction, etc. Since APD is an effortless and noninvasive pulmonary diagnostic device, it is in particular very attractive for young children and infants unable to do spirometry.

A fiber optic enhanced bone biopsy needle

Bone marrow biopsy is a commonly practiced procedure in hospitals used for a number of purposes, such as diagnosing blood diseases and gauging a patients response to chemotherapy, etc. The procedure is relatively simple, but crude. The physician uses a specially designed needle to penetrate the tissue and the bone. Currently, the method by which a physician determines whether or not the needle is in the marrow is by his or her judgment/feeling from a slight reduction in pressure while the needle advances from bone to the bone marrow region. We present a re-design of a bone marrow biopsy needle that will increase the efficiency and success rate of the procedure. The design incorporates a dual-fiber optic cable system into a needle in order to achieve the purpose. Low power laser light (5 mW) is transmitted down one fiber optic cable through the needle and the reflected light is caught by the second fiber optic cable and is analyzed as the needle tip moves through the tissue. A distinct difference in reflectivity exists between the bone and marrow that can be detected and used to send a signal alerting the user of the exact needle tip location. This in turn will increase the probability of obtaining an adequate marrow sample, as well as simplifying the procedure, reducing patient discomfort, and preventing the need to use more than one needle biopsy due to procedural errors.