Effect of altering breathing frequency on maximum voluntary ventilation in healthy adults

Neural respiratory drive during maximal voluntary ventilation in individuals with hypertension: A case-control study

Neural respiratory drive (NRD) is measured using a non-invasive recording of respiratory electromyographic signal. The parasternal intercostal muscle can assess the imbalance between the load and capacity of respiratory muscles and presents a similar pattern to diaphragmatic activity. We aimed to analyze the neural respiratory drive in seventeen individuals with hypertension during quite breathing and maximal voluntary ventilation (MVV) (103.9 ± 5.89 vs. 122.6 ± 5 l/min) in comparison with seventeen healthy subjects (46.5 ± 2.5 vs. 46.4 ± 2.4 years), respectively. The study protocol was composed of quite breathing during five minutes, maximum inspiratory pressure followed by maximal ventilatory ventilation (MVV) was recorded once for 15 seconds. Anthropometric measurements were collected, weight, height, waist, hip, and calf circumferences, waist-to-hip ratio (WHR), waist-to-height ratio (WHtR), BMI, and conicity index (CI). Differences between groups were analyzed using the unpaired t-test or Mann-Whitney test to determine the difference between groups and moments. A significance level of 5% (p<0,05) was adopted for all statistical analyses. The group of individuals with hypertension presented higher values when compared to the healthy group for neural respiratory drive (EMGpara% 17.9±1.3 vs. 13.1±0.8, p = 0.0006) and neural respiratory drive index (NRDi (AU) 320±25 vs. 205.7±15,p = 0.0004) during quiet breathing and maximal ventilatory ventilation (EMGpara% 29.3±2.7 vs. 18.3±0.8, p = 0.000, NRDi (AU) 3140±259.4 vs. 1886±73.1,p<0.0001), respectively. In conclusion, individuals with hypertension presented higher NRD during quiet breathing and maximal ventilatory ventilation when compared to healthy individuals.

Differential control of respiratory frequency and tidal volume during exercise

The lack of a testable model explaining how ventilation is regulated in different exercise conditions has been repeatedly acknowledged in the field of exercise physiology. Yet, this issue contrasts with the abundance of insightful findings produced over the last century and calls for the adoption of new integrative perspectives. In this review, we provide a methodological approach supporting the importance of producing a set of evidence by evaluating different studies together-especially those conducted in 'real' exercise conditions-instead of single studies separately. We show how the collective assessment of findings from three domains and three levels of observation support the development of a simple model of ventilatory control which proves to be effective in different exercise protocols, populations and experimental interventions. The main feature of the model is the differential control of respiratory frequency (f_R) and tidal volume (V_T); f_R is primarily modulated by central command (especially during high-intensity exercise) and muscle afferent feedback (especially during moderate exercise) whereas V_T by metabolic inputs. Furthermore, V_T appears to be fine-tuned based on f_R levels to match alveolar ventilation with metabolic requirements in different intensity domains, and even at a breath-by-breath level. This model reconciles the classical neuro-humoral theory with apparently contrasting findings by leveraging on the emerging control properties of the behavioural (i.e. f_R) and metabolic (i.e. V_T) components of minute ventilation. The integrative approach presented is expected to help in the design and interpretation of future studies on the control of f_R and V_T during exercise.

Maximal voluntary ventilation and forced vital capacity of pulmonary function are independent prognostic factors in colorectal cancer patients: A retrospective study of 2323 cases in a single-center of China

Preoperative pulmonary function assessment is applied to select surgical candidates and predict the occurrence of postoperative complications. This present study enrolled 2323 colorectal cancer patients. Forced vital capacity (FVC) and maximal voluntary ventilation (MVV) were measured as predicted values. Associations between patient pulmonary function and both prognosis and postoperative complications was analyzed. The value of FVC and MVV optimal cutoff was 98.1 (P < .001) and 92.5 (P < .001), respectively. Low FVC and low MVV were associated with higher rates of postoperative fever (23.8% vs 13.9%, P < .001; 17.8% vs 13.3%, P = .049, respectively) and with higher rates of pneumonia (3.75% vs 1.73%, P = .002; 3.00% vs 1.71%, P = .009, respectively), pleural effusion (3.00% vs 1.57%, P = .033; 3.18% vs 1.42%, P = .006, respectively), and poor patient prognosis (5-year overall survival: 80.0% vs 90.3%, P < .001; 71.7% vs 91.9%, P < .001, respectively). In addition, low FVC was closely related to the higher rate of anastomosis leak (4.31% vs 2.29%, P = .013), low MVV was correlated with the higher rate of uroschesis (2.38% vs 0.65%, P < .001). In subgroup analyses, the predictive value of FVC and MVV in patients with different tumor stage was analyzed. Both low FVC and MVV were independent risk factors for poor prognosis in stage II and III, indicating that low FVC and MVV are predictive of poorer prognosis and higher risk of postoperative complications in colorectal cancer patients.

Lung Function and Respiratory Muscle Adaptations of Endurance- and Strength-Trained Males

Diverse exercise-induced adaptations following aerobic endurance compared to strength-training programs is well documented, however, there is paucity of research specifically focused on adaptations in the respiratory system. The aim of the study was to examine whether differences in lung function and respiratory muscle strength exist between trainers predominately engaged in endurance compared to strength-related exercise. A secondary aim was to investigate if lung function and respiratory muscle strength were associated with one-repetition maximum (1RM) in the strength trainers, and with VO2 max and fat-free mass in each respective group. Forty-six males participated in this study, consisting of 24 strength-trained (26.2 ± 6.4 years) and 22 endurance-trained (29.9 ± 7.6 years) participants. Testing involved measures of lung function, respiratory muscle strength, VO2 max, 1RM, and body composition. The endurance-trained compared to strength-trained participants had greater maximal voluntary ventilation (MVV) (11.3%, p = 0.02). The strength-trained compared to endurance-trained participants generated greater maximal inspiratory pressure (MIP) (14.3%, p = 0.02) and maximal expiratory pressure (MEP) (12.4%, p = 0.02). Moderate-strong relationships were found between strength-trained respiratory muscle strength (MIP and MEP) and squat and deadlift 1RM (r = 0.48-0.55, p ≤ 0.017). For the strength-trained participants, a strong relationship was found between MVV and VO2 max (mL·kg-1·min-1) (r = 0.63, p = 0.003) and a moderate relationship between MIP and fat-free mass (r = 0.42, p = 0.04). It appears that endurance compared to strength trainers have greater muscle endurance, while the latter group exhibits greater respiratory muscle strength. Differences in respiratory muscle strength in resistance trainers may be influenced by lower body strength.

Acute effects of high-volume compared to low-volume resistance exercise on lung function

The aim of this study was to examine whether a high-volume compared to low-volume resistance exercise session acutely impairs lung function. Fourteen males (age 23.8±6.5 years) with resistance training experience participated in this study. Participants completed two resistance training protocols (high- and low-volume) and a control session (no exercise) with the sequence randomised. High- and low-volume sessions involved 5 sets (5-SETS) and 2 sets (2-SETS), respectively of 10 repetitions at 65% one-repetition maximum for each exercise (bench press, squat, seated shoulder press, and deadlift) with 90-sec recovery between sets. Lung function was evaulated pre- and postsession and respiratory gases were measured during the recovery between sets of exercises. An increase in the ratio of forced expiratory volume in 1 sec (FEV1) to forced vital capacity was found following the 5-SETS compared to 2-SETS (P=0.033). There was a significant reduction in inspiratory capacity following 5-SETS compared to control session (P=0.049). No other lung function parameter was affected postsession. During training sessions, the squat and deadlift required greater ventilatory demands compared to the bench press and shoulder press (P<0.001). Across most exercises during 5-SETS compared to 2-SETS, there was a lower end-tidal CO2 partial pressure. Across most exercises during 5-SETS compared to 2-SETS there was a lower end-tidal CO2 partial pressure (PETCO2) (P≤0.013), although there were no other differences in physiological responses between the sessions. The findings tend to suggest that the ventilatory and respiratory muscle demands of a strenuous resistance exercise session are not great enough to acutely impair indices of lung function.

Maximal Voluntary Ventilation Should Not Be Estimated From the Forced Expiratory Volume in the First Second in Healthy People and COPD Patients

PURPOSE

To evaluate the concordance between the value of the actual maximum voluntary ventilation (MVV) and the estimated value by multiplying the forced expiratory volume in the first second (FEV1) and a different value established in the literature.

METHODS

A retrospective study was conducted with healthy subjects and patients with stable chronic obstructive pulmonary disease (COPD). Five prediction formulas MVV were used for the comparison with the MVV values. Agreement between MVV measured and MVV obtained from five prediction equations were studied. FEV1 values were used to estimate MVV. Correlation and agreement analysis of the values was performed in two groups using the Pearson test and the Bland-Altman method; these groups were one group with 207 healthy subjects and the second group with 83 patients diagnosed with COPD, respectively.

RESULTS

We recruited 207 healthy subjects (105 women, age 47 ± 17 years) and 83 COPD patients (age 66 ± 6 years; 29 GOLD II, 30 GOLD III, and 24 GOLD IV) for the study. All prediction equations presented a significant correlation with the MVV value (from 0.38 to 0.86, p < 0.05) except for the GOLD II subgroup, which had a poor agreement with measured MVV. In healthy subjects, the mean difference of the value of bias (and limits of agreement) varied between -3.9% (-32.8 to 24.9%), and 27% (-1.4 to 55.3%). In COPD patients, the mean difference of value of bias (and limits of agreement) varied between -4.4% (-49.4 to 40.6%), and 26.3% (-18.3 to 70.9%). The results were similar in the subgroup analysis.

CONCLUSION

The equations to estimate the value of MVV present a good degree of correlation with the real value of MVV, but they also show a poor concordance. For this reason, we should not use the estimated results as a replacement for the real value of MVV.