Inspiratory Maneuvers Research Articles

Poor correlation between diaphragm ultrasound and invasive gold standard technique derived respiratory muscle strength assessment in patients after hospitalization for COVID-19.

Individuals who survive acute coronavirus disease 2019 (COVID-19) might experience diaphragm muscle weakness. Diaphragm ultrasound may be an easy-to-obtain bedside tool for determining diaphragm function. However, twitch transdiaphragmatic pressure (twPdi) following magnetic stimulation (MS) of the phrenic nerves is the gold standard for non-volitional assessment of diaphragm strength. This study investigated whether diaphragm thickening ratio (DTR) measured on diaphragm ultrasound reflects diaphragm strength as measured by twPdi following MS of the phrenic nerves or other (volitional) invasively obtained pressure values and could therefore be used to accurately diagnose diaphragm weakness. One year after discharge, 50 individuals (14 female, age 58±12 years) who had been hospitalised and treated for moderate-severe COVID-19 underwent standard spirometry and diaphragm ultrasound. TwPdi following cervical MS of the phrenic nerve and volitional inspiratory manoeuvres (Sniff and Mueller manoeuvre) were measured using oesophageal and gastric balloon catheters after transnasal placement. At follow-up, no clinically meaningful restrictive lung function impairment was evident on spirometry. On diaphragm ultrasound, diaphragm dysfunction, i. e. an impaired diaphragm thickening ratio was detected in 24% (12/50) of participants. An objective diagnosis of diaphragm dysfunction, defined as twPdi <16 cmH2O, was made in 60% (30/50) of participants. The measurement results of the two methods did not agree, given that there were many false negative, but also false positive results, so diaphragm ultrasound diagnosed in parts other patients with diaphragm dysfunction than TwPdi. Diaphragm ultrasound had a sensitivity of 26.67% and a specificity of 80.0% in the detection of diaphragm dysfunction (Positive predictive value 66.67%, negative predictive value 42.10%). Diagnosis of diaphragm weakness in individuals who have recovered from COVID-19 cannot be made accurately on diaphragm ultrasound (via DTR), but requires twPdi as the gold standard for assessment of diaphragm strength.

Age-related features of the choice of inhalers in chilren and adolescents with bronchial asthma and other respiratory diseases

The inhalation way of drug delivery seems to be the most logical for respiratory diseases. However, the most important condition for the effectiveness of inhalation therapy in children and adolescents along with the correct choice of the active substance is the selection of the optimal device and adequate execution of the inspiratory maneuver. When prescribing therapy attention should be paid to the inhalation technique of a particular patient and also take into account the likelihood of side effects when using certain devices. The article provides data on factors affecting the pulmonary deposit of the drug, the internal resistance of various inhalers which have the greatest informativeness for choosing a device along with the assessment of the inspiratory flow rate developed by the patient. The most problematic aspects of drug delivery to the respiratory tract in children under 5 years of age and in patients with inadequate inhalation rate are analyzed. The principles of correct inhalation are discussed which are necessary to obtain an optimal respiratory fraction. It is known that the problem of synchronizing inhalation with the moment of receipt of the drug is the most important when using metered – dose aerosol inhalers. In children this problem can be solved by using a spacer or using nebulizers that convert the liquid form of the drug into an aerosol using compressor air. Individual selection of an inhaler depending on the abilities and preferences of the patient in some groups of patients can significantly increase the effectiveness of therapy without increasing the dose of medications. The article presents up-to-date data on digital inhaler systems and the possibilities of using electronic devices for monitoring and using the inhaler.

Effect of inspiratory muscle training on pulmonary function, respiratory muscle strength, aerobic performance, sports skills, and quality of life in wheelchair rugby athletes

IntroductionInspiratory muscle training (IMT) has been used in sports to improve factors that can positively influence sports performance. However, the effects of IMT on athletes with disabilities are less well explored. This study aimed to investigate the effects of IMT on the pulmonary function, respiratory muscle strength, aerobic performance, sports skills, and quality of life (QoL) of wheelchair rugby (WCR) athletes. MethodsA pre–post-intervention case series study of IMT was carried out with six WCR athletes. Pulmonary function (spirometry), respiratory muscle strength (manovacuometry), aerobic (cardiopulmonary exercise test) and WCR skills (Beck Battery) performance and QoL (WHOQOL-DIS) were investigated. Participants were submitted to a six-week IMT with a linear load resistor involving 30 dynamic inspiratory maneuvers twice daily for five days/week. ResultsIncreases in maximum load (+14.6%; p = 0.03), maximum effort time (+19.4%; p = 0.03), absolute and percent of predicted maximal expiratory muscle pressure (both +13.2%; p = 0.04) and absolute and percent of predicted maximal inspiratory muscle pressure (both +28.6%; p = 0.04) were observed. No significant differences were observed for pulmonary function variables, WCR skills performance or QoL. ConclusionIMT seemed to be effective at improving the respiratory muscle strength and aerobic performance of WCR players but there was no impact on pulmonary function, sports skills or QoL.

Tidal expiratory flow limitation during exercise is unrelated to peripheral hypercapnic chemosensitivity

We sought to determine if peripheral hypercapnic chemosensitivity is related to expiratory flow limitation (EFL) during exercise. Twenty participants completed one testing day which consisted of peripheral hypercapnic chemosensitivity testing and a maximal exercise test to exhaustion. The chemosensitivity testing consisting of two breaths of 10% CO2 (O2∼21%) repeated 5 times during seated rest and the first 2 exercise intensities during the maximal exercise test. Following chemosensitivity testing, participants continued cycling with the intensity increasing 20 W every 1.5 minutes till exhaustion. Maximal expiratory flow-volume curves were derived from forced expiratory capacity maneuvers performed before and after exercise at varying efforts. Inspiratory capacity maneuvers were performed during each exercise stage to determine EFL. There was no difference between the EFL and non-EFL hypercapnic chemoresponse (mean response during exercise 0.96 ± 0.46 and 0.91 ± 0.33 l min−1 mmHg−1, p=0.783). Peripheral hypercapnic chemosensitivity during mild exercise does not appear to be related to the development of EFL during exercise.

Reduced tidal volume-inflection point and elevated operating lung volumes during exercise in females with well-controlled asthma

IntroductionIndividuals with asthma breathe at higher operating lung volumes during exercise compared with healthy individuals, which contributes to increased exertional dyspnoea. In health, females are more likely to develop exertional...

Breathing a low-density gas reduces respiratory muscle force development and marginally improves exercise performance in master athletes.

We tested the hypothesis that breathing heliox, to attenuate the mechanical constraints accompanying the decline in pulmonary function with aging, improves exercise performance. Fourteen endurance-trained older men (67.9 ± 5.9 year, [Formula: see text]O2max: 50.8 ± 5.8ml/kg/min; 151% predicted) completed two cycling 5-km time trials while breathing room air (i.e., 21% O2-79% N2) or heliox (i.e., 21% O2-79% He). Maximal flow-volume curves (MFVC) were determined pre-exercise to characterize expiratory flow limitation (EFL, % tidal volume intersecting the MFVC). Respiratory muscle force development was indirectly determined as the product of the time integral of inspiratory and expiratory mouth pressure (∫Pmouth) and breathing frequency. Maximal inspiratory and expiratory pressure maneuvers were performed pre-exercise and post-exercise to estimate respiratory muscle fatigue. Exercise performance time improved (527.6 ± 38 vs. 531.3 ± 36.9s; P = 0.017), and respiratory muscle force development decreased during inspiration (-22.8 ± 11.6%, P < 0.001) and expiration (-10.8 ± 11.4%, P = 0.003) with heliox compared with room air. EFL tended to be lower with heliox (22 ± 23 vs. 30 ± 23% tidal volume; P = 0.054). Minute ventilation normalized to CO2 production ([Formula: see text]E/[Formula: see text]CO2) increased with heliox (28.6 ± 2.7 vs. 25.1 ± 1.8; P < 0.001). A reduction in MIP and MEP was observed post-exercise vs. pre-exercise but was not different between conditions. Breathing heliox has a limited effect on performance during a 5-km time trial in master athletes despite a reduction in respiratory muscle force development.

The Pharmacokinetics of Inhaled Drugs.

The pharmacokinetic (PK) profile of a drug after inhalation may differ quite markedly from that seen after dosing by other routes of administration. Drugs may be administered to the lung to elicit a local action or as a portal for systemic delivery of the drug to its site of action elsewhere in the body. Some knowledge of PK is important for both locally- and systemically-acting drugs. For a systemically-acting drug, the plasma concentration-time profile shares some similarities with drug given by the oral or intravenous routes, since the plasma concentrations (after the distribution phase) will be in equilibrium with concentrations at the site of action. For a locally-acting drug, however, the plasma concentrations reflect its fate after it has been absorbed and removed from the airways, and not what is available to its site of action in the lung. Consequently, those typical PK parameters which are determined from plasma concentration measurements, e.g., area under the curve (AUC), Cmax, tmax and post-peak t1/2 may provide information on the deposition and absorption of drugs from the lung; however, the information from these parameters becomes more complicated to decipher for those drugs which are locally-acting in the lung. Additionally, the plasma concentration profile for both locally- and systemically-acting drugs will not only reflect drug absorbed from the lung but also that absorbed from the gastrointestinal (GI) tract from the portion of the dose which is swallowed. This absorption from the GI tract adds a further complication to the interpretation of plasma concentrations, particularly for locally-acting drugs. The influence of physiological and pathological factors needs to be considered in the absorption of some inhaled drugs. The absorption of some hydrophilic drugs is influenced by the inspiratory maneuver used during initial inhalation of the drug, and at later times after deposition. Similarly, the effects of smoking have been shown to increase lung permeability and increase the absorption of certain hydrophilic drugs. The effects of different disease states of the lung have less defined influences on absorption into the systemic circulation.

Pressure dynamics of the esophagogastric junction at rest and during inspiratory maneuvers after Nissen fundoplication.

Low sphincter pressure and inability of the crural diaphragm to elevate it at the esophagogastric junction are important pathophysiological mechanisms of gastroesophageal reflux disease (GERD). The object of this study was to depict how Nissen fundoplication changed the resting and inspiratory pressures of the anti-reflux barrier. We selected 14 patients (eight males; mean age 42.7years; mean body mass index 27.8) for surgery. They answered symptoms questionnaires and underwent high-resolution manometry (HRM) before and 6months after Nissen fundoplication. We used a standard manometric protocol (resting and liquid swallows) and assessment of esophagogastric junction (EGJ) pressure metrics during standardized forced inspiratory maneuvers against increasing loads (Threshold Maneuvers). We used the Wilcoxon test for comparison of pre and postoperative data. After fundoplication, heartburn and regurgitation scores diminished remarkably (from 4.5 and 2, respectively, to zero; P = 0.002 and P = 0.0005, respective medians). Also, the median expiratory EGJ pressure had a significant increase from 8.1 to 18.1mmHg (P = 0.002), while mean respiratory pressure and EGJ contractility integral (EGJ-CI) increased without statistical significance (P = 0.064 and P = 0.06, respectively). Axial EGJ displacement was lower after fundoplication. The EGJ relaxation pressure (P = 0.001), the mean distal esophageal intrabolus pressure (P = 0.01) and the distal latency (P = 0.017) increased after fundoplication. There was a reduction in the contraction front velocity (P = 0.043). During evaluation with standardized inspiratory maneuvers, the inspiratory EGJ pressures (under loads of 12, 24, 36 and 48 cmH2O) were lower after surgery for all loads (median for load 12 cmH2O: 145.6 vs. 102.7mmHg; P = 0.004). Fundoplication and hiatal closure increased the expiratory EGJ pressure and promoted a great GERD symptom relief. The surgery seemed to overcompensate a reduced EGJ mobility and inspiratory pressure.

Respiration-related variations in central venous pressure as predictors of fluid responsiveness in spontaneously breathing patients.

The hemodynamic parameters used to accurately predict fluid responsiveness (FR) in spontaneously breathing patients (SB) require specific material and expertise. Measurements of the central venous pressure (CVP) are relatively simple and, importantly, are feasible in many critically ill patients. We analyzed the accuracy of respiration-related variations in CVP (vCVP) to predict FR in SB patients, and examined the optimization of its measurement using a standardized, deep inspiratory maneuver. We performed a monocentric, prospective, diagnostic evaluation. Spontaneously breathing patients in intensive care units with a central venous catheter were prospectively included. vCVP was measured while the patient was spontaneously breathing, both with (vCVP-st) and without (vCVP-ns) a standardized inspiratory maneuver, and calculated as: Minimum inspiratory v-wave peak pressure - Maximum expiratory v-wave peak pressure. A passive leg raising-induced increase in the left ventricular outflow tract velocity-time integral ≥10% defined FR. Among 63 patients, 38 (60.3%) presented FR. vCVP-ns was not significantly different between responders and non-responders (-4.9 mmHg [-7.5; -3.1] vs. -4.1 mmHg [-5.4; -2.8], respectively; p = 0.15). vCVP-st was lower in responders than non-responders (-9.7 mmHg [-13.9; -6.2] vs. -3.6 mmHg [-10.6; -1.6], respectively; p = 0.004). A vCVP-st < -4.7 mmHg predicted FR with 89.5% sensitivity, a specificity of 56.0%, and an area under the ROC curve of 0.72 [95% CI: 0.58; 0.86] (p = 0.004). When a central venous catheter is present, elevated values for vCVP-st may be useful to identify spontaneously breathing patients unresponsive to volume expansion. Nevertheless, the necessity of performing a standardized, deep-inspiration maneuver may limit its clinical application.

Lower-limb resistance training reduces exertional dyspnea and intrinsic neuromuscular fatigability in individuals with chronic obstructive pulmonary disease.

Skeletal muscle atrophy, dysfunction, and fatigue are important complications of chronic obstructive pulmonary disease (COPD). Greater reliance on glycolytic metabolism and increased type III/IV muscle afferent activity increase ventilatory drive, promote ventilatory constraint, amplify exertional dyspnea, and limit exercise tolerance. To investigate whether muscular adaptation with resistance training (RT) could improve exertional dyspnea, exercise tolerance, and intrinsic neuromuscular fatigability in individuals with COPD (n = 14, FEV1 = 62 ± 21% predicted), we performed a proof-of-concept single-arm efficacy study utilizing 4 wk of individualized lower-limb RT (3 times/wk). At baseline, dyspnea (Borg scale), ventilatory parameters, lung volumes (inspiratory capacity maneuvers), and exercise time were measured during a constant-load test (CLT) at 75% maximal workload to symptom limitation. On a separate day, fatigability was assessed using 3 min of intermittent stimulation of the quadriceps (initial output of ∼25% maximal voluntary force). Following RT, the CLT and fatigue protocols were repeated. Compared with baseline, isotime dyspnea was reduced (5.9 ± 2.4 vs. 4.5 ± 2.4 Borg units, P = 0.02) and exercise time increased (437 ± 405 s vs. 606 ± 447 s, P < 0.01) following RT. Isotime tidal volume increased (P = 0.01), whereas end-expiratory lung volumes (P = 0.02) and heart rate (P = 0.03) decreased. Quadriceps force, relative to initial force, was higher at the end of the stimulation protocol posttraining (53.2 ± 9.1 vs. 46.8 ± 11.9%, P = 0.04). This study provides evidence that 4 wk of RT attenuates exertional dyspnea and improves exercise tolerance in individuals with COPD, which in part, is likely due to delayed ventilatory constraint and reduced intrinsic fatigability. A pulmonary rehabilitation program beginning with individualized lower-limb RT may help mitigate dyspnea before performing aerobic training in individuals with COPD.NEW & NOTEWORTHY This study presents the novel finding that 4-wk resistance training (RT) focused specifically on the lower limbs can reduce exertional dyspnea during constant-load cycling, improve exercise tolerance, and reduce intrinsic fatigability of the quadriceps in individuals with COPD.

Voluntary activation of the diaphragm after inspiratory pressure threshold loading.

After a bout of isolated inspiratory work, such as inspiratory pressure threshold loading (IPTL), the human diaphragm can exhibit a reversible loss in contractile function, as evidenced by a decrease in transdiaphragmatic twitch pressure (PDI,TW ). Whether or not diaphragm fatigability after IPTL is affected by neural mechanisms, measured through voluntary activation of the diaphragm (D-VA) in addition to contractile mechanisms, is unknown. It is also unknown if changes in D-VA are similar between sexes given observed differences in diaphragm fatigability between males and females. We sought to determine whether D-VA decreases after IPTL and whether this was different between sexes. Healthy females (n=11) and males (n=10) completed an IPTL task with an inspired duty cycle of 0.7 and targeting an intensity of 60% maximal transdiaphragmatic pressure until task failure. PDI,TW and D-VA were measured using cervical magnetic stimulation of the phrenic nerves in combination with maximal inspiratory pressure maneuvers. At task failure, PDI,TW decreased to a lesser degree in females vs. males (87 ± 15 vs. 73 ± 12% baseline, respectively, p=0.016). D-VA decreased after IPTL but was not different between females and males (91 ± 8 vs. 88 ± 10% baseline, respectively, p=0.432). When all participants were pooled together, the decrease in PDI,TW correlated with both the total cumulative diaphragm pressure generation (R2 =0.43; p=0.021) and the time to task failure (TTF, R2 = 0.40; p = 0.30) whereas the decrease in D-VA correlated only with TTF (R2 =0.24; p=0.041). Our results suggest that neural mechanisms can contribute to diaphragm fatigability, and this contribution is similar between females and males following IPTL.

POWERbreathe® S-Index Test – guidelines and recommendations for practitioners

Abstract Study aim: POWERbreathe® S-Index Test is an accessible and functional evaluation of inspiratory muscle strength. The main purpose of this study is to present guidelines that allow to successfully apply the test in sports settings with high accuracy, robustness, and repeatability. Material and methods: Review of available literature and professional guidelines regarding traditional spirometry testing and POWERbreathe® trainers’ application was performed. The obtained information was summarized, analyzed, and interpreted to create POWERbreathe® S-Index Test guidelines and recommendations for practitioners. POWERbreathe® K4 and K5 (POWERbreathe International Ltd., Southam, UK) devices paired with Breathe-Link Live Feedback Software (POWERbreathe International Ltd., Southam, UK) were considered during the analysis and guidelines creation. Results: We recommend performing POWERbreathe® S-Index Test with 8 forceful and dynamic inspiratory maneuvers from residual volume to full inspiratory capacity, divided into 2–3 series of 2–3 maneuvers, in a standing position, after respiratory warm-up. Conclusion: POWERbreathe® S-Index Test may be a useful tool to measure functional inspiratory muscle strength in athletes. When performed with the presented guidelines, it can be successfully applied in sports settings with high accuracy, robustness, and repeatability.

Feasibility to estimate mean systemic filling pressure with inspiratory holds at the bedside.

Background: A decade ago, it became possible to derive mean systemic filling pressure (MSFP) at the bedside using the inspiratory hold maneuver. MSFP has the potential to help guide hemodynamic care, but the estimation is not yet implemented in common clinical practice. In this study, we assessed the ability of MSFP, vascular compliance (Csys), and stressed volume (Vs) to track fluid boluses. Second, we assessed the feasibility of implementation of MSFP in the intensive care unit (ICU). Exploratory, a potential difference in MSFP response between colloids and crystalloids was assessed. Methods: This was a prospective cohort study in adult patients admitted to the ICU after cardiac surgery. The MSFP was determined using 3-4 inspiratory holds with incremental pressures (maximum 35cm H2O) to construct a venous return curve. Two fluid boluses were administered: 100 and 500ml, enabling to calculate Vs and Csys. Patients were randomized to crystalloid or colloid fluid administration. Trained ICU consultants acted as study supervisors, and protocol deviations were recorded. Results: A total of 20 patients completed the trial. MSFP was able to track the 500ml bolus (p < 0.001). In 16 patients (80%), Vs and Csys could be determined. Vs had a median of 2029ml (IQR 1605-3164), and Csys had a median of 73mlmmHg-1 (IQR 56-133). A difference in response between crystalloids and colloids was present for the 100ml fluid bolus (p = 0.019) and in a post hoc analysis, also for the 500ml bolus (p = 0.010). Conclusion: MSFP can be measured at the bedside and provides insights into the hemodynamic status of a patient that are currently missing. The clinical feasibility of Vs and Csys was judged ambiguously based on the lack of required hemodynamic stability. Future studies should address the clinical obstacles found in this study, and less-invasive alternatives to determine MSFP should be further explored. Clinical Trial Registration: ClinicalTrials.gov Identifier NCT03139929.

After-effects of thixotropic conditionings on operational chest wall and compartmental volumes of patients with Parkinson's disease.

Individuals with Parkinson’s disease (PD) present respiratory dysfunctions, mainly due to decreased chest wall expansion, which worsens with the course of the disease. These findings contribute to the restrictive respiratory pattern and the reduction in chest wall volume. According to literature, inspiratory muscle thixotropic conditioning maneuvers may improve lung volumes in these patients. The study aimed to determine the after-effects of respiratory muscle thixotropic maneuvers on breathing patterns and chest wall volumes of PD. A crossover study was performed with twelve patients with PD (8 males; mean age 63.9±8.8 years, FVC%pred 89.7±13.9, FEV1%pred 91.2±15, FEV1/FVC%pred 83.7±5.7). Chest wall volumes were assessed using OEP during thixotropic maneuvers. Increases in EIVCW (mean of 126mL, p = 0.01) and EEVCW (mean of 150mL, p = 0.005) were observed after DITLC (deep inspiration from total lung capacity) due to increases in pulmonary (RCp) and abdominal (RCa) ribcage compartments. Changes in ICoTLC (inspiratory contraction from TLC) led to significant EIVCW (mean of 224mL, p = 0.001) and EEVCW (mean of 229mL, p = 0.02) increases that were mainly observed in the RCp. No significant changes were found when performing DERV (deep expiration from residual volume) and ICoRV (Inspiratory contraction from RV). Positive correlations were also observed between the degree of inspiratory contraction during ICoTLC and EEVRCp (rho = 0.613, p = 0.03) and EIVRCp (rho = 0.697, p = 0.01) changes. Thixotropy conditioning of inspiratory muscles at an inflated chest wall volume increases EIVCW and EEVCW in the ten subsequent breaths in PD patients. These maneuvers are easy to perform, free of equipment, low-cost, and may help patients improve chest wall volumes during rehabilitation.

Effect of norepinephrine on blood volume, cardiac output, and systemic filling pressure in patients undergoing liver transplantation

Patients with liver cirrhosis develop symptoms comparable to those of patients with sepsis, who have increased total vascular compliance, which may cause blood pooling in the venous pool. No previous studies have evaluated the effect of using norepinephrine on the intravascular blood volume. We investigated the norepinephrine infusion's effect on the mean systemic filling pressure, venous return, and cardiac preload in patients undergoing liver transplantation. Overall, 33 patients who underwent living donor liver transplantation were included in this study. Cardiac output (CO) was measured using a PiCCO device (Pulsion Medical Systems, Munich, Germany). The mean systemic filling pressure was calculated using the inspiratory hold maneuver at four time intervals - at baseline, 10 min after the norepinephrine infusion, 5 min after norepinephrine discontinuation, and after infusion of 500 cc of 5% albumin. Other hemodynamic parameters, including the mean arterial pressure (MAP), pulse pressure variation, stroke volume variation, global end-diastolic volume, and mitral inflow velocity (E wave), were also evaluated. The norepinephrine infusion increased MAP and systemic vascular resistance in all patients. Moreover, it increased CO, mean systemic filling pressure, and global end-diastolic volume in 20 patients (60%), whereas there were no changes in these variables in 13 patients (40%). In all patients, norepinephrine infusion discontinuation caused a significant decrease in MAP, CO, resistance to venous return, and mean systemic filling pressure. Infusion of 500 cc colloid increased CO; however, interestingly, it was associated with a significant decrease in systemic vascular resistance; hence, MAP and mean systemic filling pressure showed no changes. The norepinephrine infusion at 0.1 µg-1 kg-1 min-1 was associated with an increase in CO in patients with liver cirrhosis undergoing liver transplantation. Norepinephrine's effect on CO was primarily attributable to an increase in venous return due to an increase in mean systemic filling pressure.

Convolutional Neural Network Analysis to Predict Expiratory Flow Limitation During Exercise in Adults with Asthma

OBJECTIVE and HYPOTHESISThe objective of this study was to assess the potential for using well‐known convolutional neural network (CNN) designs to accurately identify the presence of expiratory flow‐limitation (EFL) during exercise in adult asthmatics. We hypothesized that a CNN model would accurately identify spontaneous exercise tidal flow‐volume loops (eFVL) that exceed maximal airflow from the maximal forced expiration (i.e., EFL).METHODS and RESULTSThe expiratory portion of spontaneous eFVLs were placed within the pre‐exercise maximal volitional flow‐volume envelope. Inspiratory capacity maneuvers were performed to determine the correct lung volume for placement of the eFVLs. We assembled a collection of spontaneous eFVLs from one asthmatic subject consisting of an equal number of eFVLs that were flow‐limited and non‐flow‐limited. Subsequently, our overall approach followed standard deep learning practices. The eFVLs were manually labelled as EFL and non‐EFL. The sci‐kit learn train_test_split() method was used to split the eFVLs randomly into training and testing sets using a 67%/33% split. We trained both a one‐ (expired airflow only) and a two‐channel (expired volume and airflow) CNN model to predict the presence or absence of EFL as a response to an eFVL. The models were instantiated as sequential models using the TensorFlow 2.6.0 python API. After 100 training epochs on the training cases, the 1‐channel model was challenged to predict the labels of the previously unseen testing cases. The 1‐channel model achieved 93.3% accuracy at predicting the EFL/non‐EFL labels as a response to the eFVLs despite having not been trained on these data. Additionally, the 2‐channel model was 100% accurate on the unseen test cases. We then challenged the 2‐channel model on 45 unseen eFVLs from a different asthmatic subject; the eFVLs consisted of a balance of EFL and non‐EFL. The model performed poorly, accurately identifying only 57% of the eFVLs as EFL or non‐EFL. We then trained an additional 2‐channel model on a random sample of the combined data from the two subjects and challenged the model on the unseen eFVLs from the same two subjects. At 25 epochs and 100 epochs, the CNN was challenged with unseen testing subjects and achieved 88 and 92% accuracy, respectively, at distinguishing between EFL and non‐EFL.CONCLUSIONSThese proof‐of‐concept findings provide strong evidence that neural network analyses hold promise as a novel method for identifying either the presence or absence of EFL. Given the current, tedious and nuanced methods for determining EFL, such artificial intelligence analyses hold promise for automating the analysis and identification of exercise ventilatory constraints.

The Effect of a Higher Bias Gas Flow on Imposed T-Piece Resistance and Breathing in Preterm Infants at Birth.

ObjectiveThe resistance created by the PEEP-valve of a T-piece resuscitator is bias gas flow dependent and might affect breathing in preterm infants. In this study we investigated the effect of a higher bias gas flow on the imposed inspiratory and expiratory T-piece resistance and expiratory breaking manoeuvres (EBM) in preterm infants during spontaneous breathing on CPAP at birth.MethodsIn a retrospective pre-post implementation study of preterm infants <32 weeks gestation, who were stabilised with a T-piece resuscitator, a bias gas flow of 12 L/min was compared to 8 L/min. All spontaneous breaths on CPAP within the first 10 min of starting respiratory support were analysed on a breath-by-breath basis to determine the breathing pattern of each breath and to calculate the imposed inspiratory and expiratory T-piece resistance (Ri, Re), flow rates and tidal volume.ResultsIn total, 54 infants were included (bias gas flow 12 L/min: n = 27, 8 L/min: n = 27) with a median GA of 29+6 (28+4–30+3) and 28+5 (25+6–30+3), respectively (p = 0.182). Ri and Re were significantly lower in the 12 L/min compared to 8 L/min bias flow group [Ri: 29.6 (26.1–33.6) vs. 46.4 (43.0–54.1) cm H2O/L/s, p < 0.001; Re: 32.0 (30.0–35.1) vs. 48.0 (46.3–53.9) cm H2O/L/s, p < 0.001], while the incidence of EBM [77% (53–88) vs. 77% (58–90), p = 0.586] was similar.ConclusionDuring stabilisation of preterm infants at birth with a T-piece resuscitator, the use of a higher bias gas flow reduced both the imposed inspiratory and expiratory T-piece resistance for the infant, but this did not influence the incidence of EBMs.

Use of flow volume curve to evaluate large airway obstruction.

The flow volume loop (FVL) is a graphic display of airflow against lung volumes at different levels obtained during the maximum inspiratory and expiratory maneuver. It is a simple and reproducible method of lung function assessment. A narrative review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. PubMed, EMBASE, Ovid MEDLINE and CINAHL databases were queried and reviewed for studies pertinent to the various FVLs abnormalities and their mechanisms from January 2020 to December 2020. We used the following search terms; flow-volume loop, upper airway obstruction, Obstructive airway disease, and spirometry. Assessing the shape of the flow-volume loop is particularly helpful in diagnosing and localizing upper airway obstruction. They are also helpful in identifying bronchodilator response to treatment. Characteristic FVLs is also seen in patients with obstructive or restrictive lung disorders. Spirometry should be interpreted using the absolute values for flows and volumes as well as the flow volume and volume time curves.

Effects of respiratory rate on the fluid mechanics of a reconstructed upper airway

This study aims to utilise particle image velocimetry (PIV) techniques to investigate the time-dependant effects of respiratory rate in the extrathoracic airway, to show how they affect the flow field developed. There has been limited validation of computational fluid dynamics (CFD) models using experimental setups. Furthermore, the large majority of existing CFD models focus on rigid airways, not accounting for active deformation through the breathing cycle. Experiments were carried out to expand upon Zhao et al.’s previous study, in which a single respiratory rate was investigated. This studied utilised a transient, sinusoidal flow profile with two respiratory rates of 10 breaths per minute (BPM) and 25 BPM, both achieving a maximum flow rate correlating to 5 L/min in air to simulate tidal breathing. Results from this study showed that respiratory rate had the greatest influence near the onset of the inspiratory and expiratory manoeuvres, with the higher respiratory rate homogenising later in the cycle. It was shown that airway deformation at the level of the soft palate homogenised flow downstream of the deformation which resulted in a lower peak magnitude velocity for approximately 40% of the cycle at the level of the epiglottis, when compared to the rigid airway model.

Spatial Ventilation Inhomogeneity Determined by Electrical Impedance Tomography in Patients With Chronic Obstructive Lung Disease.

The aim of this study was to examine whether electrical impedance tomography (EIT) could determine the presence of ventilation inhomogeneity in patients with chronic obstructive lung disease (COPD) from measurements carried out not only during conventional forced full expiration maneuvers but also from forced inspiration maneuvers and quiet tidal breathing and whether the inhomogeneity levels were comparable among the phases and higher than in healthy subjects. EIT data were acquired in 52 patients with exacerbated COPD (11 women, 41 men, 68 ± 11 years) and 14 healthy subjects (6 women, 8 men, 38 ± 8 years). Regional lung function parameters of forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), forced inspiratory vital capacity (FIVC), forced inspiratory volume in 1 s (FIV1), and tidal volume (VT) were determined in 912 image pixels. The spatial inhomogeneity of the pixel parameters was characterized by the coefficients of variation (CV) and the global inhomogeneity (GI) index. CV and GI values of pixel FVC, FEV1, FIVC, FIV1, and VT were significantly higher in patients than in healthy subjects (p ≤ 0.0001). The ventilation distribution was affected by the analyzed lung function parameter in patients (CV: p = 0.0024, GI: p = 0.006) but not in healthy subjects. Receiver operating characteristic curves showed that CV and GI discriminated patients from healthy subjects with an area under the curve (AUC) of 0.835 and 0.852 (FVC), 0.845 and 0.867 (FEV1), 0.903 and 0.903 (FIVC), 0.891 and 0.882 (FIV1), and 0.821 and 0.843 (VT), respectively. These findings confirm the ability of EIT to identify increased ventilation inhomogeneity in patients with COPD.