Inspiratory Capacity Measurements Research Articles

Comparing the Inspiratory Capacity Measurements Obtained by Incentive Spirometry and Ultrasonic Spirography in the Early Postoperative Period in Cardiac Surgery Patients

Incentive spirometry is one of the most common methods used for respiratory rehabilitation in the early period after cardiac surgery. Inspiratory capacity values, obtained by a patient using spirometer, are not reliably trusted.Objectives. To compare volumetric parameters measured with incentive spirometer and results obtained with bedside ultrasound-based spirometer to assure the feasibility of the use of incentive spirometry to assess the inspiratory capacity and effectiveness of postoperative respiratory rehabilitation.Materials and methods. The study included 50 patients after elective cardiac surgery. Pulmonary rehabilitation involved the use of various respiratory therapy methods. Spirography was performed before and after each session. Both approaches were used simultaneously to obtain the spirometry maximum inspiratory capacity (SMIC) with a bedside ultrasonic spirography and maximum inspiratory capacity (MIC) index using an incentive spirometer. Patient’s discomfort and adverse events during the procedures were recorded.Results. The absolute values of the MIC measured before and after each session by the two methods were dissimilar, however, the average increment values (6) did not show statistically significant differences. The correlation analysis revealed a strong positive statistically significant relationship between 6 SMIC and 6 MIC (R = 0.74 before the session, R = 0.79 after the session, R = 0.77 across the whole data set, P < 0.01), also consistent with the Bland–Altman analysis, evidencing that more than 95% of all values fell within ± 1.96 SD of the mean difference. The inspiratory spirometry method showed good diagnostic accuracy (sensitivity 87%, specificity 85%, area under the curve (AUC) 0.8 (95% CI: [0.76; 0.83]), P < 0.001). Refusals of procedure were more often documented with ultrasonic spirography.Conclusion. The increment in the inspiratory capacity index measured with incentive spirometer shows good agreement with ultrasonic spirography measurements. Therefore, incentive spirometry can be reliably used to assess the effectiveness of respiratory rehabilitation interventions in cardiac surgery patients during early postoperative period.

The Six-Minute Stepper Test Is Valid to Evaluate Functional Capacity in Hospitalized Patients With Exacerbated COPD.

Background: The six-minute stepper test (6MST) is a self-paced test considered a valid tool to assess functional capacity in stable COPD patients. However, a high floor effect, where a large proportion of participants reach the minimum score when using the measurement instrument, might compromise the test validity in the hospital setting. Therefore, this study aimed at verifying the concurrent validity of 6MST in hospitalized patients with acute exacerbation of COPD (AECOPD). Methods: A cross-sectional study was conducted in a tertiary hospital. Patients who were hospitalized due to AECOPD were considered for inclusion. On the first day, when patients reached minimum clinical criteria considered as the use of non-invasive ventilation less than 2 h for 6 h/period, dyspnea at rest less than 7 (very severe) on the modified Borg scale, a respiratory rate less than 25 breaths per minute, oxygen pulse saturation greater than 88% (considering use of supplemental oxygen) and absence of paradoxical breathing pattern, they underwent a lung function evaluation and answered three questionnaires: Chronic Respiratory Questionnaire (CRQ), Modified Medical Research Council Dyspnea Scale (MMRC), and COPD Assessment Test (CAT). Then, on two consecutive days, patients performed 6MST or six-minute walk test (6MWT), in random order. Each test was performed twice, and the best performance was recorded. Also, the patient’s severity was classified according to the BODE index. Inspiratory capacity measurements were performed before and after each test execution. Results: Sixteen patients (69.4 ± 11.4 years) with a mean FEV₁ of 49.4 ± 9.9% predicted were included (9 females). There was a strong correlation of the performance in 6MST (number of cycles) with 6MWT (distance walked in meters) in absolute values (r = 0.87, p < 0.001) as well as with the percentage of predicted normal 6MWT (r = 0.86, p < 0.001). There was a strong correlation between the performance in 6MST with the dynamic hyperinflation (r = 0.72, p = 0.002) and a moderate correlation between 6MST with the percentage of reduction of inspiratory capacity (r = 0.68, p = 0.004). We also identified that 6MST showed moderate negative correlations with CAT (r = −0.62, p = 0.01) and BODE index (r = −0.59, p = 0.01). Conclusion: It could be concluded that 6MST is valid for evaluating functional capacity in hospitalized patients with exacerbated COPD.

Patients with Chronic Obstructive Pulmonary Disease Can Accurately Perform Home-Based Measurements of Inspiratory Capacity and Dynamic Hyperinflation

Home-based lung function measurements can be used to capture day-to-day variations in symptoms in patients with chronic obstructive pulmonary disease (COPD). Although dynamic hyperinflation (DH) is clinically relevant, existing home-based measurements do not include its assessment. DH can be measured through inspiratory capacity (IC) measurements before and after metronome-paced tachypnea test (MPT). The goal of this study is to determine the accuracy of unsupervised home-based IC and DH measurements in COPD. Sixteen COPD patients performed IC and DH measurements during 4 home visits. Visit 1 was considered a training session. During all visits supervised and unsupervised IC at rest (ICREST) and after MPT (ICMPT) were measured. DH was calculated as the difference between ICREST and ICMPT, and as a percentage of ICREST. Bland-Altman analyses and ANOVA tests were performed to determine the effect of supervision and repeated measures over time. The biases between supervised and unsupervised ICREST, ICMPT, ΔIC and ΔIC% were 0.007 L, 0.007 L, 0 mL and −0.09% in the last visit, respectively. Limits of agreement of ICREST and ΔIC% decreased from ±0.261 mL to ±0.201 mL, and from ±13.84% to ±10.81% between visit 1 and 4, respectively. No significant effect of supervision or over time was found. After a robust training and a learning phase, COPD patients are able to perform IC measurements in an accurate manner in both rest and after MPT. This yield accurate assessment of DH, in an unsupervised home-based setting.

Effect of Six-Minute Walk Test and Incremental Exercise on Inspiratory Capacity, Ventilatory Constraints, Breathlessness and Exercise Performance in Sedentary Male Smokers without Airway Obstruction.

We investigated physiological responses and exercise capacity in sedentary young smokers during sub-maximal and maximal test and its impact on dyspnea and exercise intolerance. Fifty sedentary male smokers and non-smokers (age: 24 ± 1 years., weight: 71 ± 9 kg, height: 177.3 ± 4.8 cm, body mass index: 22.6 ± 2.5 kg/m2) underwent two visits with pulmonary function tests, breathing pattern, and inspiratory capacity measurement at rest and during sub-maximal and maximal exercise. Smokers show reduced exercise capacity during six minutes walk test (6-MWT) with decreased walked distance (p < 0.001) and inspiratory capacity (p < 0.05). During cardiopulmonary exercise test (CPET), smokers had higher minute ventilation VE for a given submaximal intensity (p < 0.05) and lower minute ventilation at maximal exercise (p < 0.001). End expiratory lung volume was significantly lower in sedentary smokers at rest (p < 0.05), at ventilatory threshold during exercise (p < 0.05), but not during peak exercise. End inspiratory lung volume was significantly lower in smokers at rest (p < 0.05) and ventilatory threshold (p < 0.05). Cigarette smoking alters lung function during submaximal and maximal exercise. This alteration is manifested by the development of dynamic hyperinflation contributing to exercise capacity limitation.

Effects of Tiotropium/Olodaterol on Activity-Related Breathlessness, Exercise Endurance and Physical Activity in Patients with COPD: Narrative Review with Meta-/Pooled Analyses.

One of the most debilitating symptoms of chronic obstructive pulmonary disease (COPD) is breathlessness, which leads to avoidance of physical activities in daily living and hastens clinical deterioration. Treatment of patients with COPD with inhaled long-acting muscarinic antagonist (LAMA)/long-acting β2-agonist (LABA) combination therapy improves airflow limitation, reduces breathlessness compared with LAMA or LABA monotherapies, and improves health status and quality of life. A large clinical trial programme focusing on the effects of tiotropium/olodaterol combination therapy demonstrated that this LAMA/LABA combination improves lung function and reduces hyperinflation (assessed by serial inspiratory capacity measurements) compared with either tiotropium alone or placebo in patients with COPD. Tiotropium/olodaterol also increases exercise endurance capacity and improves patient perception of the intensity of breathlessness compared with placebo. In this narrative review, we focus on the relationship between improving symptoms during activity, the ability to remain active in daily life and how this may impact quality of life. We consider the benefits of therapy optimisation by means of dual bronchodilation with tiotropium/olodaterol, and present new data from meta-analyses/pooled analyses showing that tiotropium/olodaterol improves inspiratory capacity compared with placebo and tiotropium and improves exercise endurance time compared with placebo after 6 weeks of treatment. We also discuss the importance of taking a holistic approach to improving physical activity, including pulmonary rehabilitation and exercise programmes in parallel with bronchodilator therapy and psychological programmes to support behaviour change.Graphic

ENSIFENTRINE ADDED ON TO TIOTROPIUM SIGNIFICANTLY IMPROVES INSPIRATORY CAPACITY IN PATIENTS WITH SYMPTOMATIC COPD

SESSION TITLE: Obstructive Lung Disease Posters SESSION TYPE: Original Investigation Posters PRESENTED ON: October 18-21, 2020 PURPOSE: Ensifentrine (RPL554) is an investigational, first-in-class, inhaled dual inhibitor of PDE3 and PDE4 that combines bronchodilator and anti-inflammatory actions in a single compound. In a previously completed dose-ranging study in patients with COPD, nebulized ensifentrine delivered clinically meaningful and significant improvements versus placebo in lung function and symptoms (Singh et al. 2020). In a second dose-ranging study, nebulized ensifentrine (0.375, 0.75, 1.5 or 3 mg) or placebo was given in addition to tiotropium for 4 weeks in symptomatic COPD patients following a 14-day run-in on tiotropium. All ensifentrine doses produced significant bronchodilation on top of tiotropium with a dose-dependent increase from baseline to peak FEV1 (primary endpoint) at week 4 of 78 to 124 mL (placebo-corrected; all p<0.05). This abstract reports on the pre-specified exploratory investigation of the effect of twice-daily nebulized ensifentrine versus placebo on inspiratory capacity (IC) in the same study. METHODS: Analysis was performed on all randomized patients with sufficient data collected after intake of study treatment to compute the pharmacodynamic parameters based on FEV1 on at least one occasion. The analysis comprised 413 patients with 83, 83, 81, 82 in the 0.375, 0.75, 1.5, 3.0 mg ensifentrine + tiotropium groups and 84 in the placebo + tiotropium treatment group. IC maneuvers were conducted according to ATS/ERS guidelines (Miller et al, 2005) prior to the forced maneuvers 30 minutes pre-dose and 2 hours post-dose following randomization (Day 1) and at the last dose at Week 4. The change from baseline was calculated. RESULTS: Mean age was 64.3 years, with 52.2% under 65 years of age. Patients were primarily female (57.5%), caucasian (90.1%) and current smokers (55.3%) with chronic bronchitis (59%). Day 1 baseline IC was similar between treatment groups. Placebo-corrected change from baseline in IC on Day 1 (2h post-dose) was 76, 62, 115 and 108 mL for the 0.375, 0.75, 1.5, 3.0 mg ensifentrine + tiotropium groups, respectively. The 1.5 and 3 mg doses showed statistically significant improvements (p<0.01). After 4 weeks of twice-daily ensifentrine added to once daily tiotropium, there was a statistically significant improvement of 110.2 mL in IC (2 h post-dose) compared with placebo (tiotropium alone, p=0.0290) with the 3 mg ensifentrine dose + tiotropium treatment group. CONCLUSIONS: This study demonstrates a clinically meaningful response in IC after treatment with 4 weeks of ensifentrine in COPD patients who remain symptomatic and with impaired lung function despite the use of tiotropium. CLINICAL IMPLICATIONS: Measurement of IC as a marker of dynamic lung hyperinflation has been shown to correlate with dyspnea and exercise performance in stable COPD. Results suggest a physiological mechanism by which ensifentrine improved symptoms and health-related quality of life. DISCLOSURES: Consultant relationship with Verona Pharma Please note: $5001 - $20000 Added 06/01/2020 by Thomas Bengtsson, source=Web Response, value=Consulting fee Employee relationship with Verona pharma Please note: >$100000 by Tara Rheault, source=Admin input, value=Stock Employee relationship with Verona Pharma Please note: >$100000 Added 05/20/2020 by Kathleen Rickard, source=Web Response, value=Salary

Evaluation of Dynamic Respiratory Mechanical Abnormalities During Conventional CPET.

Assessment of the ventilatory response to exercise is important in evaluating mechanisms of dyspnea and exercise intolerance in chronic cardiopulmonary diseases. The characteristic mechanical derangements that occur during exercise in chronic respiratory conditions have previously been determined in seminal studies using esophageal catheter pressure-derived measurements. In this brief review, we examine the emerging role and clinical utility of conventional assessment of dynamic respiratory mechanics during exercise testing. Thus, we provide a physiologic rationale for measuring operating lung volumes, breathing pattern, and flow–volume loops during exercise. We consider standardization of inspiratory capacity-derived measurements and their practical implementation in clinical laboratories. We examine the evidence that this iterative approach allows greater refinement in evaluation of ventilatory limitation during exercise than traditional assessments of breathing reserve. We appraise the available data on the reproducibility and responsiveness of this methodology. In particular, we review inspiratory capacity measurement and derived operating lung volumes during exercise. We demonstrate, using recent published data, how systematic evaluation of dynamic mechanical constraints, together with breathing pattern analysis, can provide valuable insights into the nature and extent of physiological impairment contributing to exercise intolerance in individuals with common chronic obstructive and restrictive respiratory disorders.

Deterioration of Nighttime Respiratory Mechanics in COPD: Impact of Bronchodilator Therapy

COPD is associated with nighttime respiratory symptoms, poor sleep quality, and increased risk of nocturnal death. Overnight deterioration of inspiratory capacity (IC) and FEV1 have been documented previously. However, the precise nature of this deterioration and mechanisms by which evening bronchodilation may mitigate this occurrence have not been studied. What is the effect of evening dosing of dual, long-acting bronchodilation on detailed nocturnal respiratory mechanics and inspiratory neural drive (IND)? A double-blind, randomized, placebo-controlled crossover study assessed the effects of evening long-acting bronchodilation (aclidinium bromide/formoterol fumarate dihydrate: 400/12 μg) or placebo on morning trough IC (12h after the dose; primary outcome) and serial overnight measurements of spirometry, dynamic respiratory mechanics, and IND (secondary outcomes). Twenty participants with COPD (moderate/severe airway obstruction and lung hyperinflation) underwent serial measurements of IC, spirometry, breathing pattern, esophageal and transdiaphragmatic pressures, and diaphragm electromyography (diaphragmatic electromyography as a percentage of maximum; IND) at 6 time points from 0 to 12h after the dose and compared with sleeping IND. Compared with placebo, evening bronchodilation was not associated with increased morning trough IC 12h after the dose (P= .48); however, nadir IC (lowest IC, independent of time), peak IC, area under the curve for 12h after the dose, and IC for 10h after the dose were improved (P< .05). During placebo, total airways resistance, lung hyperinflation, IND, and tidal esophageal and transdiaphragmatic pressure swings all increased significantly overnight compared with baseline evening values; however, each of these parameters improved with bronchodilator treatment (P< .05) with no change in ventilation or breathing pattern. Respiratory mechanics significantly deteriorated at night during placebo. Although the morning trough IC was unchanged, evening bronchodilator treatment was associated consistently with sustained overnight improvements in dynamic respiratory mechanics and inspiratory neural drive compared with placebo CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov identifier NCT02429765.

How stable is lung function in patients with stable chronic obstructive pulmonary disease when monitored using a telehealth system? A longitudinal and home-based study

BackgroundMany telehealth systems have been designed to identify signs of exacerbations in patients with chronic obstructive pulmonary disease (COPD), but few previous studies have reported the nature of recorded lung function data and what variations to expect in this group of individuals. The aim of the study was to evaluate the nature of individual diurnal, day-to-day and long-term variation in important prognostic markers of COPD exacerbations by employing a telehealth system developed in-house.MethodsEight women and five men with COPD performed measurements (spirometry, pulse oximetry and the COPD assessment test (CAT)) three times per week for 4–6 months using the telehealth system. Short-term and long-term individual variations were assessed using the relative density and weekly means respectively. Quality of the spirometry measurements (forced expiratory volume in one second (FEV1) and inspiratory capacity (IC)) was assessed employing the criteria of American Thoracic Society (ATS)/European Respiratory Society (ERS) guidelines.ResultsClose to 1100 measurements of both FEV1 and IC were performed during a total of 240 patient weeks. The two standard deviation ranges for intra-individual short-term variation were approximately ±210 mL and ± 350 mL for FEV1 and IC respectively. In long-term, spirometry values increased and decreased without notable changes in symptoms as reported by CAT, although it was unusual with a decrease of more than 50 mL per measurement of FEV1 between three consecutive measurement days. No exacerbation occurred. There was a moderate to strong positive correlation between FEV1 and IC, but weak or absent correlation with the other prognostic markers in the majority of the participants.ConclusionsAlthough FEV1 and IC varied within a noticeable range, no corresponding change in symptoms occurred. Therefore, this study reveals important and, to our knowledge, previously not reported information about short and long-term variability in prognostic markers in stable patients with COPD. The present data are of significance when defining criteria for detecting exacerbations using telehealth strategies.

Inspiratory Capacity and NT-pro BNP Predict Key Cardiopulmonary Exercise Results but not Six-Minute Walk Test distance in Older Patients with Heart Failure

Introduction Heart failure (HF) affects more than five million people, half of whom are at least 75 years old. Peak oxygen consumption (VO2peak), Ventilatory efficiency (VE/VCO2 slope) and the Six-Minute Walk test (6MWT) are powerful prognostic indicators and are useful for monitoring the therapeutic efficacy of symptom and disease management. Cardiopulmonary Exercise testing (CPX) and/or the 6MWT are often not performed as a part of symptom assessment and management in older adults with HF, presumably due to cost, comorbidities and/or potential frailty. NT-pro BNP, NYHA classification, and inspiratory capacity are all easily obtainable in an office setting and may correlate with VO2peak, the VE/VCO2 slope, Peak cardiac output (Qpeak) and/or 6MWT. Hypothesis NT-pro BNP, NYHA classification, and/or inspiratory capacity predict VO2peak, the VE/VCO2 slope, Qpeak, and/or 6MWT. Methods Twenty-three patients (73.6 + 4.5 years old) with HF underwent assessment and determination of NYHA classification status, venipuncture, inspiratory capacity measurement, and performed the 6MWT and CPX per standardized protocol, (Qpeak measured via acetylene washin method). VO2peak, VE/VCO2 slope and Qpeak were recorded during the CPX. Results The strongest relationships were between inspiratory capacity and Qpeak, and between NT-pro BNP and the VE/VCO2 slope. There was a moderate relationship between inspiratory capacity and VO2peak and between NT-pro BNP and VO2peak. Inspiratory capacity and NT-pro BNP combined explained 42% of the variance in VO2peak (adjusted R2 = 0.42, F (2, 20) = 8.82, p Conclusion NT-pro BNP and inspiratory capacity can, either alone or combined, explain between 42% and 59% of variance in key exercise measurements. Both measurements are obtainable in the office setting for monitoring the therapeutic efficacy of symptom and disease management. Moreover, inspiratory capacity has the potential to be measured by older adults in their home.

The Effect of Breathing Retraining Using Metronome-Based Acoustic Feedback on Exercise Endurance in COPD: A Randomized Trial.

During exercise-training patients with chronic obstructive pulmonary disease (COPD) can entrain their breathing pattern to visual-feedback cues as to achieve a slower respiratory rate and prolong exhalation. The result is an improvement in exercise tolerance and a reduction in dynamic hyperinflation. Acoustic stimuli, including metronome-generated acoustic stimuli, can entrain human movements. Accordingly, we hypothesized that exercise duration and dynamic hyperinflation would be less after exercise-training plus breathing-retraining using a metronome-based acoustic-feedback system than after exercise-training alone. Of 205 patients with COPD [FEV1 = 44 ± 16% predicted (± SD)] recruited, 119 were randomly assigned to exercise-training plus breathing-retraining using acoustic feedback (n = 58) or exercise-training alone (n = 61). Patients exercised on a treadmill thrice-weekly for 12weeks. Before and at completion of training, patients underwent constant-load treadmill testing with inspiratory capacity measures every 2min. At completion of training, improvements in exercise duration in the breathing-retraining plus exercise-training and exercise-training alone groups were similar (p = 0.35). At isotime, inspiratory capacity increased (less exercise-induced dynamic hyperinflation) by 3% (p = 0.001) in the breathing-retraining plus exercise-training group and remained unchanged in the exercise-alone group. The between-group change in inspiratory capacity, however, was not significant (p = 0.08). In patients with COPD, breathing-retraining using a metronome-based acoustic feedback did not result in improved exercise endurance or decreased dynamic hyperinflation when compared to exercise-training alone. ClinicalTrials.gov; No.: NCT NCT01009099; URL: http://www.clinicaltrials.gov.

Inspiratory Capacity and Vital Capacity of Healthy Subjects 9-81 Years of Age at Moderate-High Altitude.

Measurements of inspiratory capacity (IC) and vital capacity (VC) are used to recognize dynamic hyperinflation, but appropriate reference values are required to achieve accurate clinical interpretations. Altitude above sea level is a potential determining factor for lung volumes, including IC and VC. To describe IC and VC for healthy people who live in Mexico City at an altitude of 2,240 m above sea level. Healthy subjects ages 9-81 y completed slow spirometry by following 2005 American Thoracic Society/European Respiratory Society standards. Once associations were explored, linear regression models were constructed and values were compared with those from previously published equations. A total of 441 healthy subjects (55.1% women) participated. The mean age was 32 y (minimum age, 9 y; maximum age, 81 y). IC and VC measurements were associated with sex, age, height, and weight. An accelerated increase in IC and VC was evident from 9 to 20 y of age, followed by a gradual decrease in both sexes. In general, IC was higher in our population than predicted by previously published reference equations. IC in healthy people at 2,240 m above sea level was higher than that of previous reports about European and Latin-American subjects of the same height, sex, and age who were at sea level. The present study provided robust reference values for persons who lived at a moderate altitude.

Low exertional inspiratory capacity is not related to dynamic inspiratory muscle weakness in heart failure

Reduction in inspiratory capacity (IC) during exercise has been reported in chronic heart failure (CHF). Since inspiratory muscle dysfunction may be present to a variable degree, the assumption that IC reduction during exercise represents an increase in end-expiratory lung volume must be made with caution. This interpretation is flawed if patients develop dynamic inspiratory muscle strength reduction, i.e., progressively lower esophageal (Pes) pressures as the IC maneuvers are repeated. Sixteen CHF patients and 9 age-matched controls performed an incremental exercise test with serial IC and respiratory pressure measurements. Regardless whether IC decreased or not with exercise (N = 4 and N = 12, respectively), Pes,IC remained stable. This was confirmed by similar Pes,sniff immediately upon exercise cessation (p > .05). No association was found between changes in IC and related Pes from rest to peak exercise. Owing to the lack of dynamic inspiratory muscle weakness, non-invasive indexes of lung mechanics can be reliably obtained from exercise IC in CHF.

Static and dynamic hyperinflation during severe acute exacerbations of chronic obstructive pulmonary disease.

BackgroundStatic hyperinflation is known to be increased during moderate acute exacerbations of chronic obstructive pulmonary disease (COPD) (AECOPD), but few data exist in patients with severe exacerbations of COPD. The role of dynamic hyperinflation during exacerbations is unclear.MethodsIn a prospective, observational cohort study, we recruited patients admitted to hospital for AECOPD. The following measurements were performed upon admission and again after resolution (stable state) at least 42 days later: inspiratory capacity (IC), body plethysmography, dynamic hyperinflation by metronome-paced IC measurement, health-related quality of life and dyspnea.ResultsForty COPD patients were included of whom 28 attended follow-up. The IC was low at admission (2.05±0.11 L) and increased again during resolution by 15.6%±23.1% or 0.28±0.08 L (mean ± standard error of the mean, p<0.01). Testing of metronome-paced changes in IC was feasible, and it decreased by 0.74±0.06 L at admission, similarly to at stable state. Clinical COPD Questionnaire score was 3.7±0.2 at admission and improved by 1.7±0.2 points (p<0.01), and the Borg dyspnea score improved by 2.2±0.5 points from 4.4±0.4 at admission (p<0.01).ConclusionStatic hyperinflation is increased during severe AECOPD requiring hospitalization compared with stable state. We could measure metronome-paced dynamic hyperinflation during severe AECOPD but found no increase.

Sizing the lung in dogs: the inspiratory capacity defines the tidal volume.

ObjectiveTo evaluate a novel physiological approach for setting the tidal volume in mechanical ventilation according to inspiratory capacity, and to determine if it results in an appropriate mechanical and gas exchange measurements in healthy and critically ill dogs.MethodsTwenty healthy animals were included in the study to assess the tidal volume expressed as a percentage of inspiratory capacity. For inspiratory capacity measurement, the mechanical ventilator was set as follows: pressure control mode with 35cmH2O of inspired pressure and zero end-expiratory pressure for 5 seconds. Subsequently, the animals were randomized into four groups and ventilated with a tidal volume corresponding to the different percentages of inspiratory capacity. Subsequently, ten critically ill dogs were studied.ResultsHealthy dogs ventilated with a tidal volume of 17% of the inspiratory capacity showed normal respiratory mechanics and presented expected PaCO2 values more frequently than the other groups. The respiratory system and transpulmonary driving pressure were significantly higher among the critically ill dogs but below 15 cmH2O in all cases.ConclusionsThe tidal volume based on the inspiratory capacity of each animal has proven to be a useful and simple tool when setting ventilator parameters. A similar approach should also be evaluated in other species, including human beings, if we consider the potential limitations of tidal volume titration based on the calculated ideal body weight.

Effects of Expiratory Positive Airway Pressure on Exercise Tolerance, Dynamic Hyperinflation, and Dyspnea in COPD.

The application of expiratory positive airway pressure (EPAP) in patients with COPD during exercise may reduce dynamic hyperinflation, while, on the other hand, it can increase the resistive work of breathing. Therefore, we evaluated the effects of 2 intensities of EPAP during exercise on tolerance, dynamic hyperinflation, and dyspnea in subjects with moderate to very severe COPD. We performed a cross-sectional, experimental, 4-visit study. In visit 1, subjects performed symptom-limited cycling incremental cardiopulmonary exercise test (CPET). In visits 2-4, at least 48 h apart, in a randomized order, subjects performed constant CPET without EPAP, EPAP with 5 cm H2O (EPAP5), or EPAP with 10 cm H2O (EPAP10). The study included 15 non-hypoxemic subjects ranging from moderate to very severe COPD (mean FEV1 = 35 ± 11% predicted). Increasing intensities of EPAP during constant CPET tended to cause progressive reduction in exercise tolerance (P = .11). Of note, 10 of 15 subjects demonstrated significantly shorter average exercise duration with EPAP10 compared to the test without EPAP (-151 ± 105 s, P = .03 or -41 ± 26%). Minute ventilation increment was constrained by EPAP, secondary to a limited increase in tidal volume (P = .01). Finally, dyspnea sensation and serial measurements of inspiratory capacity during exercise were similar when comparing the three interventions at isotime and at end-constant CPETs. The application of EPAP5 or EPAP10 during exercise tended to cause a progressive reduction in exercise tolerance in subjects with COPD without improvement in dyspnea or dynamic hyperinflation at equivalent exercise duration.

Effect of β-blockade on lung function, exercise performance and dynamic hyperinflation in people with arterial vascular disease with and without COPD

Introductionβ Blockers are important treatment for ischaemic heart disease and heart failure; however, there has long been concern about their use in people with chronic obstructive pulmonary disease (COPD) due...

Parasternal intercostal muscle activity during methacholine-induced bronchoconstriction.

What is the central question of this study? The parasternal intercostal electromyogram (EMGpara) is known to provide an accurate, non-invasive index of respiratory load-capacity balance. Although relationships between EMGpara and both airflow obstruction and hyperinflation have been shown, the independent contribution of each factor has not been examined. What is the main finding and its importance? Reductions in airway calibre and inspiratory capacity along with increases in EMGpara were induced via methacholine challenge. A strong inverse relationship was observed between EMGpara and airway obstruction, with no influence of inspiratory capacity. These data suggest that EMGpara is more strongly influenced by airway calibre than by changes in end-expiratory lung volume during airway challenge testing. Neural respiratory drive, measured via the parasternal intercostal electromyogram (EMGpara), provides a non-invasive index of the load-capacity balance of the respiratory muscle pump. Previous studies in patients with obstructive lung disease have shown strong relationships between EMGpara and the extent of both airflow obstruction and hyperinflation. The relative influence of the two factors has not, however, been described. Airflow obstruction was induced via methacholine challenge testing in 25 adult humans. Forced expiratory volume in 1 s (FEV1 ) and surface EMGpara during tidal breathing were measured after each dose, with 20 of the participants also undergoing measurements of inspiratory capacity (IC) at each stage. Linear mixed model analysis was used to assess dose-wise changes in FEV1 and EMGpara, and thereafter to determine the influence of changes in FEV1 and IC on change in EMGpara. Median (interquartile range) FEV1 decreased significantly [from 96.00 (80.00-122.30) to 67.80 (37.98-92.27)% predicted, P<0.0001] and EMGpara increased significantly [from 5.37 (2.25-8.92) to 6.27 (3.37-19.60) μV, P<0.0001] from baseline to end of test. Linear mixed model analysis showed a significant interaction between methacholine dose and induced change in EMGpara, with an increase in EMGpara of 0.24 (95% confidence interval 0.11-0.37) μV per methacholine dose2 . Change in FEV1 further influenced this relationship [increase in slope of 0.002 (0.004-0.001) μVdose-2 per % predicted fall in FEV1 , P=0.011], but not with change in IC. These data suggest that bronchoconstriction exerts a more potent influence on levels of EMGpara than changes in end-expiratory lung volume during methacholine challenge.

Dynamic hyperinflation in patients with asthma and exercise-induced bronchoconstriction

BackgroundLittle is known about the behavior of operative lung volumes during exercise in patients with asthma and exercise-induced bronchoconstriction (EIB). ObjectiveTo compare the presence of dynamic hyperinflation (DH) in patients with mild asthma with and without EIB and in healthy individuals and to relate the changes in end-expiratory lung volume (EELV) with postexercise airflow reduction. MethodsA total of 122 consecutive stable patients (>12 years of age) with mild asthma and 38 controls were studied. Baseline lung volumes were measured, and all patients performed an exercise bronchial challenge. At each minute of exercise, EELV and end-inspiratory lung volume (EILV) were estimated from inspiratory capacity measurements to align the tidal breathing flow-volume loops to within the maximal expiratory curve. ResultsDH was more frequent in patients with asthma and EIB (76%) than in patients with asthma but without EIB (11%) or controls (18%). The EELV increased in patients with asthma and EIB and decreased in patients with asthma without EIB and controls during exercise. In the patients with asthma, the decrease in forced expiratory volume in 1 second after the exercise challenge correlated with age (r = −0.179, P = .05), baseline forced vital capacity (r = 0.255, P = .005), EELV increase (r = 0.447, P < .001), and EILV increase (r = 0.246, P = .007). Age, baseline forced vital capacity, and magnitude of DH were retained as independent predictors of EIB intensity. ConclusionIn patients with asthma and EIB, the development of DH is very frequent and related to the intensity of postexercise bronchoconstriction. This finding could implicate DH in the development of EIB.

Inspiratory Capacity as an Indirect Measure of Immediate Effects of Positive Expiratory Pressure and CPAP Breathing on Functional Residual Capacity in Healthy Subjects.

Positive expiratory pressure (PEP) and CPAP are used to enhance breathing parameters such as functional residual capacity (FRC) in patients. Studies comparing effects of PEP and CPAP on FRC are few and variable. One reason for this may be that sophisticated equipment, not suitable in the clinical setting, is required. Because total lung capacity (TLC) consists of inspiratory capacity (IC) and FRC, a change in IC should result in a corresponding change in FRC given constant TLC. We aimed to evaluate the effects of different PEP and CPAP devices on IC as an indirect measure of induced changes in FRC from these devices in healthy subjects. Twenty healthy subjects breathed with 2 PEP devices, a PEP mask (flow resistor) and a PEP bottle (threshold resistor), and 2 CPAP devices, a flow resistor and a threshold resistor, in a randomized order. The measurement sequence consisted of 30 breaths with an IC measurement performed before and immediately after the 30th breath while the subjects were still connected to the breathing device. Perceived exertion of the 30 breaths was measured with the Borg category ratio 10 scale. Three of the 4 breathing devices, the PEP mask and the 2 CPAP devices, significantly decreased IC (P < .001). Median perceived exertion was quite low for all 4 breathing devices, but the difference in perceived exertion among the different breathing devices was large. Provided that TLC is constant, we found that measurements of changes in IC could be used as an indirect measure of changes in FRC in healthy subjects. All investigated breathing devices except the PEP bottle decreased IC, as an indirect measure of increased FRC.