Development and Validation of a Portable EIT System for Real-Time Respiratory Monitoring.

This work contributes to the improvement of novel medical technologies for the prevention and treatment of diseases. Electrical impedance tomography (EIT) has gained attention as a valuable tool for non-invasive monitoring providing real-time insights. The purpose of this work is to develop and validate a novel portable EIT system with a small form factor for respiratory monitoring. The device uses a 16-electrode architecture with adjacent stimulation and measurement patterns, an integrated circuit current source and a single high-speed ADC operating with multiplexers to stimulate and measure across all electrodes. Tests were conducted on 25 healthy subjects who performed a pulmonary function test with a flowmeter while using the EIT device. The results showed a good performance of the device, which was able to recognize all respirations correctly, and from the EIT signals and images, correlations of 96.7% were obtained for instantaneous respiratory rate and 96.1% for tidal volume prediction. These results validate the preliminary technical feasibility of the EIT system and demonstrates its potential as a reliable tool for non-invasive respiratory assessment. The significance of this work lies in its potential to democratize advanced respiratory monitoring technologies, making them accessible to a wider population, including those in remote or underserved areas.

Artificial Intelligence-Driven Prognosis of Respiratory Mechanics: Forecasting Tissue Hysteresivity Using Long Short-Term Memory and Continuous Sensor Data.

Tissue hysteresivity is an important marker for determining the onset and progression of respiratory diseases, calculated from forced oscillation lung function test data. This study aims to reduce the number and duration of required measurements by combining multivariate data from various sensing devices. We propose using the Forced Oscillation Technique (FOT) lung function test in both a low-frequency prototype and the commercial RESMON device, combined with continuous monitoring from the Equivital (EQV) LifeMonitor and processed by artificial intelligence (AI) algorithms. While AI and deep learning have been employed in various aspects of respiratory system analysis, such as predicting lung tissue displacement and respiratory failure, the prediction or forecasting of tissue hysteresivity remains largely unexplored in the literature. In this work, the Long Short-Term Memory (LSTM) model is used in two ways: (1) to estimate the hysteresivity coefficient η using heart rate (HR) data collected continuously by the EQV sensor, and (2) to forecast η values by first predicting the heart rate from electrocardiogram (ECG) data. Our methodology involves a rigorous two-hour measurement protocol, with synchronized data collection from the EQV, FOT, and RESMON devices. Our results demonstrate that LSTM networks can accurately estimate the tissue hysteresivity parameter η, achieving an R2 of 0.851 and a mean squared error (MSE) of 0.296 for estimation, and forecast η with an R2 of 0.883 and an MSE of 0.528, while significantly reducing the number of required measurements by a factor of three (i.e., from ten to three) for the patient. We conclude that our novel approach minimizes patient effort by reducing the measurement time and the overall ambulatory time and costs while highlighting the potential of artificial intelligence methods in respiratory monitoring.

Design and Evaluation of a Novel Venturi-Based Spirometer for Home Respiratory Monitoring.

The high cost and limited availability of home spirometers pose a significant barrier to effective respiratory disease management and monitoring. To address this challenge, this paper introduces a novel Venturi-based spirometer designed for home use, leveraging the Bernoulli principle. The device features a 3D-printed Venturi tube that narrows to create a pressure differential, which is measured by a differential pressure sensor and converted into airflow rate. The airflow is then integrated over time to calculate parameters such as the Forced Vital Capacity (FVC) and Forced Expiratory Volume in one second (FEV1). The system also includes a bacterial filter for hygienic use and a circuit board for data acquisition and streaming. Evaluation with eight healthy individuals demonstrated excellent test-retest reliability, with intraclass correlation coefficients (ICCs) of 0.955 for FVC and 0.853 for FEV1. Furthermore, when compared to standard Pulmonary Function Test (PFT) equipment, the spirometer exhibited strong correlation, with Pearson correlation coefficients of 0.992 for FVC and 0.968 for FEV1, and high reliability, with ICCs of 0.987 for FVC and 0.907 for FEV1. These findings suggest that the Venturi-based spirometer could significantly enhance access to spirometry at home. However, further large-scale validation and reliability studies are necessary to confirm its efficacy and reliability for widespread use.

Differences between oscillometry measurements obtained by MostGraph-01 and MasterScreen-IOS in patients with asthma.

BACKGROUND: Oscillometry devices (also termed forced oscillation technique) devices such as MasterScreen-IOS® (Jaeger, Hochberg, Germany) and MostGraph-01® (Chest, Tokyo, Japan) are useful for obtaining physiological assessments in patients with obstructive lung diseases, including asthma. However, as oscillometry measurements have not been fully compared between MasterScreen-IOS® and MostGraph-01® in patients with asthma, it is unknown whether there are differences in the measurements between the devices. This study aimed to determine whether there is any difference in oscillometry measurements obtained using the two devices in patients with asthma. METHODS: Oscillometry measurements obtained using MasterScreen-IOS® and MostGraph-01® were retrospectively evaluated in 95 patients with asthma at Juntendo University Hospital between October 2009 and November 2009. RESULTS: There was a strong positive correlation in the measurements between the two devices. However, the values of R5, R20, ALX and Fres were lower when measured with MostGraph-01® than with MasterScreen-IOS®, and vice versa for the values of X5. The results were used in correction equations to convert oscillometry parameters measured using MasterScreen-IOS® to those measured using MostGraph-01®. CONCLUSIONS: To our knowledge, this is the first report to compare MostGraph-01® and MasterScreen-IOS® devices using practical clinical data obtained in patients with asthma. The values obtained by both devices can be interpreted in a similar way, although there is slight variation. The conversion equations produced in this study may assist to compare the oscillometry measurements obtained by each of the two devices.

[Research on portable airway impedance monitoring device based on expiratory oscillation].

Monitoring airway impedance has significant clinical value in accurately assessing and diagnosing pulmonary function diseases at an early stage. To address the issue of large oscillator size and high power consumption in current pulmonary function devices, this study adopts a new strategy of expiration-driven oscillation. A lightweight and low-power airway impedance monitoring system with integrated sensing, control circuitry, and dynamic feedback system, providing visual feedback on the system's status, was developed. The respiratory impedance measurement experiments and statistical comparisons indicated that the system could achieve stable measurement of airway impedance at 5 Hz. The frequency spectrum curves of respiratory impedance ( R and X) showed consistent trends with those obtained from the clinical pulmonary function instrument, specifically the impulse oscillometry system (IOS). The differences between them were all less than 1.1 cm H 2O·s/L. Additionally, there was a significant statistical difference in the respiratory impedance R5 between the exercise and rest groups, which suggests that the system can measure the variability of airway resistance parameters during exercise. Therefore, the impedance monitoring system developed in this study supports subjects in performing handheld, continuous measurements of dynamic changes in airway impedance over an extended period of time. This research provides a foundation for further developing low-power, portable, and even wearable devices for dynamic monitoring of pulmonary function.

A wearable eddy current based pulmonary function sensor for continuous non-contact point-of-care monitoring during the COVID-19 pandemic.

Pulmonary function testing (PFT) allows for quantitative analysis of lung function. However, as a result of the coronavirus disease 2019 (COVID-19) pandemic, a majority of international medical societies have postponed PFTs in an effort to mitigate disease transmission, complicating the continuity of care in high-risk patients diagnosed with COVID-19 or preexisting lung pathologies. Here, we describe the development of a non-contact wearable pulmonary sensor for pulmonary waveform analysis, pulmonary volume quantification, and crude thoracic imaging using the eddy current (EC) phenomenon. Statistical regression analysis is performed to confirm the predictive validity of the sensor, and all data are continuously and digitally stored with a sampling rate of 6,660 samples/second. Wearable pulmonary function sensors may facilitate rapid point-of-care monitoring for high-risk individuals, especially during the COVID-19 pandemic, and easily interface with patient hospital records or telehealth services.

Pressure measurement characteristics of a micro-transducer and balloon catheters.

Respiratory pressure responses to cervical magnetic stimulation are important measurements in monitoring the mechanical function of the respiratory muscles. Pressures can be measured using balloon catheters or a catheter containing integrated micro-transducers. However, no research has provided a comprehensive analysis of their pressure measurement characteristics. Accordingly, the aim of this study was to provide a comparative analysis of these characteristics in two separate experiments: (1) in vitro with a reference pressure transducer following a controlled pressurization; and (2) in vivo following cervical magnetic stimulations. In vitro the micro-transducer catheter recorded pressure amplitudes and areas which were in closer agreement to the reference pressure transducer than the balloon catheter. In vivo there was a main effect for stimulation power and catheter for esophageal (Pes ), gastric (Pga ), and transdiaphragmatic (Pdi ) pressure amplitudes (p < 0.001) with the micro-transducer catheter recording larger pressure amplitudes. There was a main effect of stimulation power (p < 0.001) and no main effect of catheter for esophageal (p = 0.481), gastric (p = 0.923), and transdiaphragmatic (p = 0.964) pressure areas. At 100% stimulator power agreement between catheters for Pdi amplitude (bias =6.9 cmH2 O and LOA -0.61 to 14.27 cmH2 O) and pressure areas (bias = -0.05 cmH2 O·s and LOA -1.22 to 1.11 cmH2 O·s) were assessed. At 100% stimulator power, and compared to the balloon catheters, the micro-transducer catheter displayed a shorter 10-90% rise time, contraction time, latency, and half-relaxation time, alongside greater maximal rates of change in pressure for esophageal, gastric, and transdiaphragmatic pressure amplitudes (p < 0.05). These results suggest that caution is warranted if comparing pressure amplitude results utilizing different catheter systems, or if micro-transducers are used in clinical settings while applying balloon catheter-derived normative values. However, pressure areas could be used as an alternative point of comparison between catheter systems.

Effects of three pulmonary ventilation regimes in patients undergoing coronary artery bypass graft surgery: a randomized clinical trial.

The aim was to compare the effect of diaphragmatic breathing exercise (DBE), flow- (FIS) and volume-oriented incentive spirometry (VIS) on pulmonary function- (PFT), functional capacity-6-Minute Walk Test (6 MWT) and Functional Difficulties Questionnaire (FDQ) in subjects undergoing Coronary Artery Bypass Graft surgery (CABG). The purpose of incorporating pulmonary ventilator regimes is to improve ventilation and avoid post-operative pulmonary complications. CABG patients (n = 72) were allocated to FIS, VIS and DBE groups (n = 24 each) by block randomization. Preoperative and postoperative values for PFT were taken until day 7 for all three groups. On 7th postoperative day, 6 MWT and FDQ was analyzed using ANOVA and post-hoc analysis. PFT values were found to be decreased on postoperative day 1(Forced Vital Capacity (FVC) = FIS group-65%, VIS group-47%, DBE group-68%) compared to preoperative day (p < 0.001). PFT values for all 3 groups recovered until postoperative day 7 (FVC = FIS group-67%, VIS group-95%, DBE group-59%) but was found to reach the baseline in VIS group (p < 0.001). When compared between 3 groups, statistically significant improvement was observed in VIS group (p < 0.001) in 6 MWT and FDQ assessment. In conclusion, VIS was proven to be more beneficial in improving the pulmonary function (FVC), functional capacity and FDQ when compared to FIS and DBE.

Effectiveness of expiratory flow acceleration in patients with Parkinson's disease and swallowing deficiency: A preliminary study.

OBJECTIVES: Parkinson's disease (PD) causes dysfunction both to swallowing and to the cough mechanism. Oropharyngeal dysphagia is the main cause of pneumonia, due to silent aspiration of food and saliva. Pneumonia is the leading cause of death in PD. Different strategies exist to reduce the risk of inhalation and associated lung infections, but evidence of their efficacy is still unclear. The aim of this preliminary study was to investigate if adding an expiratory flow acceleration (EFA®) technique to standard therapy (ST) for dysphagia can reduce the incidence of bronchopulmonary infections and improve quality of life, respiratory function parameters, cough, and airways encumbrance perception. MATERIALS AND METHODS: Twenty-five patients with PD were randomized to two groups: ST vs. ST + EFA. Patients were re-assessed at 30, 180 and 360 days from start of treatment. The primary outcome was the incidence of respiratory exacerbations together with quality of life score (PDQ-39). Secondary outcomes were changes in respiratory function tests, cough capacity (CPEF), perceived health status (Euro-QOL-VAS), cough, and upper airways encumbrance perception evaluated by visual numeric scale (VNS). RESULTS: Twenty patients concluded the study (10 each group). Albeit the difference was not significant, less respiratory infections, symptoms, hospital admissions and medical visits were found in the study group. Furthermore, there was a significant difference in cough effectiveness measured with the peak cough expiratory flow (PCEF) and other spirometry parameters (FEV1, FVC), and also in specific and generic health-related quality of life measures (PDQ-39, Euro-QoL-VAS). CONCLUSION: The results of this preliminary study support the use of EFA® technology in Parkinson's patients with dysphagia to reduce the risk of respiratory complications. Nevertheless, further studies are needed in a larger, more representative sample to definitively confirm the usefulness of this technique in PD patients.

Point-of-care blood gas analyzers have an impact on the acceptance of donor lungs for transplantation.

An organ donor PaO2 above 40 kPa is generally required for lung transplantation. Point-of-care (POC) blood gas analyzers are commonly used by organ procurement organizations (OPO) but may underestimate the PaO2 at high levels. We hypothesized that changing to a more accurate blood gas analyzer would result in additional lungs transplanted. All PaO2 measurements on organ donors managed at one OPO's recovery center were performed on an i-STAT POC analyzer prior to October 2015, and on a GEM 4000 subsequently. For 24 weeks, all blood gases were tested simultaneously on both analyzers. We compared lung outcomes of 147 donors in the year prior to this change (using the i-STAT) with 56 donors in the 24-week study period (using the GEM 4000 for lung allocation). When the PaO2 was above 40 kPa, the i-STAT PaO2 was 7.2 kPa lower on average than the GEM 4000. When the GEM PaO2 measured between 40 and 50 kPa, the corresponding i-STAT PaO2 value registered less than 40 kPa 25 out of 48 times (52%), with an average difference of 7.3 kPa (SD = 2.9). The rate of lungs transplanted using the GEM 4000 was 48% compared with 35% in the year prior using the i-STAT (p = .11), with equivalent recipient outcomes. The i-STAT analyzer underestimated the PaO2 above 40 kPa and changing to a more accurate PaO2 analyzer may increase lungs transplanted.

Addressing Reduced Laboratory-Based Pulmonary Function Testing During a Pandemic.

To reduce the spread of the severe acute respiratory syndrome coronavirus 2, many pulmonary function testing (PFT) laboratories have been closed or have significantly reduced their testing capacity. Because these mitigation strategies may be necessary for the next 6 to 18 months to prevent recurrent peaks in disease prevalence, fewer objective measurements of lung function will alter the diagnosis and care of patients with chronic respiratory diseases. PFT, which includes spirometry, lung volume, and diffusion capacity measurement, is essential to the diagnosis and management of patients with asthma, COPD, and other chronic lung conditions. Both traditional and innovative alternatives to conventional testing must now be explored. These may include peak expiratory flow devices, electronic portable spirometers, portable exhaled nitric oxide measurement, airwave oscillometry devices, and novel digital health tools such as smartphone microphone spirometers and mobile health technologies along with integration of machine learning approaches. The adoption of some novel approaches may not merely replace but could improve existing management strategies and alter common diagnostic paradigms. With these options comes important technical, privacy, ethical, financial, and medicolegal barriers that must be addressed. However, the coronavirus disease 19 pandemic also presents a unique opportunity to augment conventional testing by including innovative and emerging approaches to measuring lung function remotely in patients with respiratory disease. The benefits of such an approach have the potential to enhance respiratory care and empower patient self-management well beyond the current global pandemic.

Lung clearance index in healthy volunteers, measured using a novel portable system with a closed circuit wash-in.

INTRODUCTION: Lung clearance index (LCI) is a sensitive measure of early lung disease, but adoption into clinical practice has been slow. Challenges include the time taken to perform each test. We recently described a closed-circuit inert gas wash-in method that reduces overall testing time by decreasing the time to equilibration. The aim of this study was to define a normative range of LCI in healthy adults and children derived using this method. We were also interested in the feasibility of using this system to measure LCI in a community setting. METHODS: LCI was assessed in healthy volunteers at three hospital sites and in two local primary schools. Volunteers completed three washout repeats at a single visit using the closed circuit wash-in method (0.2% SF6 wash-in tracer gas to equilibrium, room air washout). RESULTS: 160 adult and paediatric subjects successfully completed LCI assessment (95%) (100 in hospital, 60 in primary schools). Median coefficient of variation was 3.4% for LCI repeats and 4.3% for FRC. Mean (SD) LCI for the analysis cohort (n = 53, age 5-39 years) was 6.10 (0.42), making the upper limit of normal LCI 6.8. There was no relationship between LCI and multiple demographic variables. Median (interquartile range) total test time was 18.7 (16.0-22.5) minutes. CONCLUSION: The closed circuit method of LCI measurement can be successfully and reproducibly measured in healthy volunteers, including in out-of-hospital settings. Normal range appears stable up to 39 years. With few subjects older than 40 years, further work is required to define the normal limits above this age.

Multimodal remote chest monitoring system with wearable sensors: a validation study in healthy subjects.

OBJECTIVE: Development of wearable medical technology for remote monitoring of patients suffering from chronic lung diseases may improve the care, therapy and outcome of these patients. APPROACH: A multimodal system using wearable sensors for the acquisition of multiple biosignals (electrical bioimpedance of the chest for electrical impedance tomography and respiratory rate assessment, peripheral oxygen saturation, chest sounds, electrocardiography for heart rate measurement, body activity, and posture) was developed and validated in a prospective, monocentric study on 50 healthy subjects. The subjects were studied under different types of ventilation (tidal and deep breathing, forced full expiration maneuver) and during increased body activity and posture changes. The major goals were to assess the functionality by determining the presence and plausibility of the signals, comfort of wearing and safety of the vest. MAIN RESULTS: All intended signals were recorded. Streaming of selected signals and wireless download of complete data sets were functional. Electrical impedance tomography recordings revealed good to excellent quality of detection of ventilation-related impedance changes in 34 out of 50 participants. Respiratory and heart rates were reliably detected and generally in physiological ranges. Peripheral oxygen saturation values were unphysiologically low. The chest sound recordings did not show waveforms allowing meaningful analysis of lung sounds. Body activity and posture were correctly identified. The comfort of wearing and the vest properties were positively rated. No adverse events occurred. SIGNIFICANCE: Albeit the full functionality of the current vest design was not established, the study confirmed the feasibility of remote functional chest monitoring with a marked increase in clinically relevant information compared to existing systems.

The COSMED K5 in Breath-by-Breath and Mixing Chamber Mode at Low to High Intensities.

PURPOSE: The portable metabolic analyzer COSMED K5 (Rome, Italy) allows for switching between breath-by-breath (BBB) and dynamic micro-mixing chamber (DMC) modes. This study aimed to evaluate the reliability and validity of the K5 in BBB and DMC at low, moderate, and high metabolic rates. METHODS: Two K5 simultaneously operated in BBB or DMC, whereas (i) a metabolic simulator (MS) produced four different metabolic rates (repeated eight times), and (ii) 12 endurance-trained participants performed bike exercise at 30%, 40%, 50%, and 85% of their individual power output at V˙O2max (repeated three times). K5 data were compared with predicted simulated values and consecutive Douglas bag measurements. RESULTS: Reliability did not differ significantly between BBB and DMC, whereas the typical error and intraclass correlation coefficients for oxygen uptake (V˙O2), carbon dioxide output (V˙CO2), and minute ventilation (V˙E) ranged from 0.27% to 6.18% and from 0.32 to 1.00 within four metabolic rates, respectively. Validity indicated by mean differences ranged between 0.61% and -2.05% for V˙O2, 2.99% to -11.04% for V˙CO2, and 0.93% to -6.76% for V˙E compared with MS and Douglas bag at low to moderate metabolic rates and was generally similar for MS and bike exercise. At high rates, mean differences for V˙O2 amounted to -4.63% to -7.27% in BBB and -0.38% to -3.81% in DMC, indicating a significantly larger difference of BBB at the highest metabolic rate. CONCLUSION: The K5 demonstrated accurate to acceptable reliability in BBB and DMC at all metabolic rates. Validity was accurate at low and moderate metabolic rates. At high metabolic rates, BBB underestimated V˙O2, whereas DMC showed superior validity. To test endurance athletes at high workloads, the DMC mode is recommended.

Concordant Validity of a Digital Peak Cough Flow Meter to Assess Voluntary Cough Strength in Individuals with ALS.

Peak cough flow represents an important metric directly related to the physiologic ability of an individual to defend the airway or expel tracheal aspirate. Given the high prevalence of dysphagia and dystussia in individuals with amyotrophic lateral sclerosis (ALS) and recent findings that the expiratory phase of voluntary cough is significantly impaired in ALS individuals, we aimed to determine the reproducibility of an affordable, portable peak cough flow (PCF) meter for the assessment of cough production in individuals with ALS. 109 individuals with ALS completed voluntary cough testing using both the research cough spirometry equipment and a digital peak cough flow meter. Maximum peak expiratory cough flow rates were obtained from each device. Analyses included paired t test, Pearson's correlation, and Lin's concordance correlation to determine the degree of agreement and reproducibility between cough measurement devices (alpha = 0.05). Mean differences between peak cough flow test values (L/min) across instruments were not statistically significant (mean difference = - 2.93; 95% CI - 18.67, 12.82; p = 0.713). PCF values obtained from the digital peak cough flow meter and the research cough spirometry equipment were strongly associated (r = 0.826, p < 0.000) and demonstrated a high level of agreement and reproducibility (ρc = 0.824, 95% CI 0.754, 0.876). These data validate the use of an inexpensive and portable digital peak cough flow device to index peak cough flow strength in individuals with ALS. This assessment could easily be incorporated into a multidisciplinary ALS clinical setting to index the physiologic ability of an individual to protect the airway.

Using digital technology for home monitoring, adherence and self-management in cystic fibrosis: a state-of-the-art review.

Digital healthcare is a rapidly growing healthcare sector. Its importance has been recognised at both national and international level, with the WHO recently publishing its first global strategy for digital health. The use of digital technology within cystic fibrosis (CF) has also increased. CF is a chronic, life-limiting condition, in which the treatment burden is high and treatment regimens are not static. Digital technologies present an opportunity to support the lives of people with CF. We included 59 articles and protocols in this state-of-the-art review, relating to 48 studies from 1999 until 2019. This provides a comprehensive overview of the expansion and evolution of the use of digital technology. Technology has been used with the aim of increasing accessibility to healthcare, earlier detection of pulmonary exacerbations and objective electronic adherence monitoring. It may also be used to promote adherence and self-management through education, treatment management Apps and social media.

Highly Linear Phase-Canceling Self-Injection-Locked Ultrasonic Radar for Non-Contact Monitoring of Respiration and Heartbeat.

A novel phase-canceling demodulation scheme to improve the linearity of a self-injection-locked (SIL) ultrasonic radar is proposed with the goal of solving the null detection problem and accurately sensing large displacements of a moving target. A proportional-integral (PI) controller regulates the phase of the injection signal and cancels the Doppler phase shift by tuning a delay in the received echo signal, and this tunable delay serves as the radar output, which is linearly proportional to the displacement of the target. Without assuming weak injection, the frequency and phase equations for an SIL oscillator are derived, supporting the construction of a plant model and the design of a PI controller. Also, a new ultrasonic radar equation is presented for estimating the radar detection range. The SIL radar with phase regulation is operated in its anti-phase injection mode for better performance. The proposed design is implemented on an FPGA to make a 40 kHz continuous-wave ultrasonic radar. The maximum detectable peak-to-peak motion is up to 120 mm (approximately 14 wavelengths of displacement), with a total harmonic distortion as low as 2.3% for the detection of 1 Hz harmonic motion. The radar is used to detect the human chest movement for non-contact monitoring of the respiratory rate and heart rate. Due to the high linearity and sensitivity, the radar is capable of faithfully detecting the relatively large involuntary body movements and lung movements while still preserving the weak heartbeat rhythm buried in them, with the average error of measured heart rates less than 1 BPM.

A Comparison of the s/z Ratio to Instrumental Aerodynamic Measures of Phonation.

OBJECTIVE: The purpose of this study was to examine how the s/z ratio and instrumental measures of laryngeal valving and voicing efficiency. STUDY DESIGN: Prospective, cohort design. METHODS: Fifteen adult males (mean age 28.3 years) and 15 adult females (mean age 29.2 years) with normal voice quality were recruited and compared on productions of the s/z ratio and instrumental aerodynamic measures. The aerodynamic measures included vital capacity, maximum phonation time, airflow rate during sustained and sentence production, subglottal pressure, and laryngeal airway resistance. These measures were obtained on the Phonatory Aerodynamic System Model 6600. Statistical analyses included a univariate analysis of variance to examine for differences between sexes for all the variables, and between the s/z ratios for each of the three trials. Pearson's Product Moment Correlations were performed to identify the strength and nature of any significant relationships between the s/z ratio and instrumental aerodynamics. RESULTS: There were significant differences in the mean values between males and females only for the measures of vital capacity and maximum phonation time. There were no significant differences between the three trials for the s/z ratio. There was a significant moderate negative correlation between the s/z ratio and laryngeal airway resistance in females and between the s/z ratio and sentence airflow rate in males. CONCLUSIONS: The s/z ratio demonstrated only a moderate correlation with limited instrumental measures of laryngeal valving. In the absence of clear evidence of its ability to accurately assess laryngeal valving, the s/z ratio should be used in combination with other instrumental measures of laryngeal aerodynamics for a better representation of aerodynamic functioning.