Efficacy of inspiratory muscle training on inspiratory muscle function, functional capacity, and quality of life in patients with asthma: A randomized controlled trial.

OBJECTIVE: To evaluate the efficacy of an inspiratory muscle training protocol on inspiratory muscle function, functional capacity, and quality of life in patients with asthma. DESIGN: A single-blind, randomized controlled clinical trial. SETTING: Community-based. SUBJECTS: Patients with asthma, aged between 20 and 70 years old, non-smokers. INTERVENTIONS: Participants were randomized into two groups: inspiratory muscle training group performed inspiratory muscle training 5 days a week for 8 weeks, consisting of six sets of 30 breaths per day with a training load ⩾50% of maximal inspiratory pressure, plus an educational program; the control group only received the educational program. MAIN MEASUREMENTS: Maximal inspiratory pressure, inspiratory muscle endurance, and the distance performed on the incremental shuttle walking test were assessed pre-intervention, post-intervention and at follow-up (3 months after the end of the intervention). The asthma quality of life questionnaire was applied pre and post-intervention. RESULTS: Data from 39 participants were analyzed. Maximal inspiratory pressure in percentage of predicted and endurance test duration were significantly higher post-intervention in the inspiratory muscle training group (∆ post-pre: 50.8% vs 7.3% of predicted - P < 0.001 and ∆ post-pre: 207.9 seconds vs 2.7 seconds - P < 0.001, respectively). There was no significant difference in the incremental shuttle walking distance between groups (∆ post-pre: 30.9 m vs -8.1 m, P = 0.165). Quality of life was perceived as significantly better, without a difference between groups (P > 0.05). CONCLUSIONS: About 8 weeks of inspiratory muscle training in patients with controlled asthma significantly increased inspiratory muscle strength and endurance.

Use of volume controlled vs. pressure controlled volume guaranteed ventilation in elderly patients undergoing laparoscopic surgery with laryngeal mask airway.

BACKGROUND: The peak inspiratory pressure (PIP) is crucial in mechanical ventilation with supraglottic airway device (SAD). Pressure-controlled ventilation volume-guaranteed (PCV-VG), delivering a preset tidal volume with the lowest required airway pressure, is being increasingly used during general anesthesia. In this study, we compared respiratory mechanics and circulatory parameters between volume-controlled ventilation (VCV) and PCV-VG in elderly patients undergoing laparoscopic surgery using the laryngeal mask airway supreme (LMA). METHODS: Eighty participants scheduled for laparoscopic surgery were enrolled in this prospective, randomized clinical trial. The participants were randomly assigned to receive VCV or PCV-VG. PIP, dynamic compliance (Cdyn) and mean inspiratory pressure (Pmean) were recorded at 5 min after induction of anesthesia (T1), 5 min after pneumoperitoneum(T2), 30 and 60 min after pneumoperitoneum (T3 and T4). Data including other respiratory variables, hemodynamic variables, and arterial blood gases were also collected. The difference in PIP between VCV and PCV-VG was assessed as the primary outcome. RESULTS: PIP was significantly lower at T2, T3, and T4 in both groups compared with T1 (all P <  0.0001), and it was significantly lower in the PCV-VG group than the VCV group at T2, T3, and T4 (all P <  0.001). Cydn was decreased at T2, T3, and T4 in two groups compared with T1 (all P <  0.0001), but it was higher in PCV-VG group than in VCV group at T2, T3, and T4 (all P <  0.0001). There were on statistically significant differences were found between the groups for other respiratory and hemodynamic variables. CONCLUSION: In elderly patients who underwent laparoscopic surgery using an LMA, PCV-VG was superior to VCV in its ability to provide ventilation with lower peak inspiratory pressure and greater dynamic compliance.

Evaluation of Respiratory Muscle Strength and Diaphragm Ultrasound: Normative Values, Theoretical Considerations, and Practical Recommendations.

BACKGROUND: Reference values derived from existing diaphragm ultrasound protocols are inconsistent, and the association between sonographic measures of diaphragm function and volitional tests of respiratory muscle strength is still ambiguous. OBJECTIVE: To propose a standardized and comprehensive protocol for diaphragm ultrasound in order to determine lower limits of normal (LLN) for both diaphragm excursion and thickness in healthy subjects and to explore the association between volitional tests of respiratory muscle strength and diaphragm ultrasound parameters. METHODS: Seventy healthy adult subjects (25 men, 45 women; age 34 ± 13 years) underwent spirometric lung function testing, determination of maximal inspiratory and expiratory pressure along with ultrasound evaluation of diaphragm excursion and thickness during tidal breathing, deep breathing, and maximum voluntary sniff. Excursion data were collected for amplitude and velocity of diaphragm displacement. Diaphragm thickness was measured in the zone of apposition at total lung capacity (TLC) and functional residual capacity (FRC). All participants underwent invasive measurement of transdiaphragmatic pressure (Pdi) during different voluntary breathing maneuvers. RESULTS: Ultrasound data were successfully obtained in all participants (procedure duration 12 ± 3 min). LLNs (defined as the 5th percentile) for diaphragm excursion were as follows: (a) during tidal breathing: 1.2 cm (males; M) and 1.2 cm (females; F) for amplitude, and 0.8 cm/s (M) and 0.8 cm/s (F) for velocity, (b) during maximum voluntary sniff: 2.0 cm (M) and 1.5 cm (F) for amplitude, and 6.7 (M) cm/s and 5.2 cm/s (F) for velocity, and (c) at TLC: 7.9 cm (M) and 6.4 cm (F) for amplitude. LLN for diaphragm thickness was 0.17 cm (M) and 0.15 cm (F) at FRC, and 0.46 cm (M) and 0.35 cm (F) at TLC. Values for males were consistently higher than for females, independent of age. LLN for diaphragmatic thickening ratio was 2.2 with no difference between genders. LLN for invasively measured Pdi during different breathing maneuvers are presented. Voluntary Pdi showed only weak correlation with both diaphragm excursion velocity and amplitude during forced inspiration. CONCLUSIONS: Diaphragm ultrasound is an easy-to-perform and reproducible diagnostic tool for noninvasive assessment of diaphragm excursion and thickness. It supplements but does not replace respiratory muscle strength testing.

Assessing Inspiratory Muscle Strength for Early Detection of Respiratory Failure in Motor Neuron Disease: Should We Use MIP, SNIP, or Both?

BACKGROUND: Motor neuron disease (MND) invariably impacts on inspiratory muscle strength leading to respiratory failure. Regular assessment of sniff nasal inspiratory pressure (SNIP) and/or maximal mouth inspiratory pressure (MIP) contributes to early detection of a requirement for ventilatory support. OBJECTIVES: The aim of this study was to compare the feasibility, agreement, and performance of both tests in MND. METHODS: Patients with MND followed by a multidisciplinary consultation were prospectively included. Pulmonary follow-up included forced expiratory volumes, vital capacity (VC) seated and supine, MIP, SNIP, pulse oximetry, and daytime arterial blood gases. RESULTS: A total of 61 patients were included. SNIP and MIP could not be performed in 14 (21%) subjects; 74% of the subjects showed a decrease in MIP or SNIP at inclusion versus 31% for VC. Correlation between MIP and SNIP (Pearson's rho: 0.68, p < 0.001) was moderate, with a non-significant bias in favor of SNIP (3.6 cm H2O) and wide limits of agreement (-34 to 41 cm H2O). Results were similar in "bulbar" versus "non-bulbar" patients. At different proposed cut-off values for identifying patients at risk of respiratory failure, the agreement between MIP and SNIP (64-79%) and kappa values (0.29-0.53) was moderate. CONCLUSIONS: MIP and SNIP were equally feasible. There was no significant bias in favor of either test, but a considerable disparity in results between tests, suggesting that use of both tests is warranted to screen for early detection of patients at risk of respiratory failure and avoid over diagnoses. SNIP, MIP, and VC all follow a relatively linear downhill course with a steeper slope for "bulbar" versus "non-bulbar" patients.

Impairment of respiratory muscle strength in Berardinelli-Seip congenital lipodystrophy subjects.

BACKGROUND: Berardinelli-Seip Congenital Generalized Lipodystrophy (BSCL) is an ultra-rare metabolic disease characterized by hypertriglyceridemia, hyperinsulinemia, hyperglycemia, hypoleptinemia, and diabetes mellitus. Although cardiovascular disturbances have been observed in BSCL patients, there are no studies regarding the Respiratory Muscle Strength (RMS) in this type of lipodystrophy. This study aimed to evaluate RMS in BSCL subjects compared with healthy subjects. METHODS: Eleven individuals with BSCL and 11 healthy subjects matched for age and gender were included in this study. The Maximum Inspiratory Pressure (MIP), Maximum Expiratory Pressure (MEP), and Peripheral Muscle Strength (PMS) were measured for three consecutive years. BSCL subjects were compared to healthy individuals for MIP, MEP, and PMS. Correlations between PMS and MIP were also analyzed. The genetic diagnosis was performed, and sociodemographic and anthropometric data were also collected. RESULTS: BSCL subjects showed significantly lower values for MIP and MEP (p <  0.0001 and p = 0.0002, respectively) in comparison to healthy subjects, but no changes in handgrip strength (p = 0.15). Additionally, we did not observe changes in MIP, MEP, and PMS two years after the first analysis, showing maintenance of respiratory dysfunction in BSCL subjects (p = 0.05; p = 0.45; p = 0.99). PMS and MIP were not correlated in these subjects (r = 0.56; p = 0.18). CONCLUSION: BSCL subjects showed lower respiratory muscle strength when compared with healthy subjects; however, PMS was not altered. These findings were maintained at similar levels during the two years of evaluation. Our data reveal the first association of BSCL with the development of respiratory muscle weakness.

Effect of Manual Therapy, Motor Control Exercise, and Inspiratory Muscle Training on Maximum Inspiratory Pressure and Postural Measures in Moderate Smokers: A Randomized Controlled Trial.

OBJECTIVE: The aim of this study is to assess whether adding manual therapy to motor control exercises protocol with inspiratory muscle training (IMT) (combined intervention) resulted in a greater effect than IMT alone in enhancing maximum inspiratory pressure (MIP) in the short term. METHODS: This was a single-blind, randomized, controlled trial. Fifty-one healthy moderate smokers were randomized into 2 groups: (1) IMT and (2) combined intervention. All participants received 8 individual sessions, 2 per week during a 4-week period. The primary outcome (MIP) and the secondary outcome (pulmonary function, forward head posture, and thoracic kyphosis) were recorded at baseline and after the treatments. RESULTS: There were differences between groups in change score for MIP (mean, 23.8; 95% confidence interval [CI]: 16.48-31.12), forward head posture (-1.57; 95% CI: -2.79 to -0.35), and thoracic kyphosis (-0.92; 95% CI: -1.74 to -0.1). The combined intervention revealed statistically significant differences for MIP (mean, -34; 95% CI: -39.12 to -28.88) and for postural measures (forward head posture 2.31; 95% CI: 1.45-3.16; thoracic kyphosis, 1.39; 95% CI: 0.8-1.97), whereas the IMT was only observed for MIP (mean, -10.2; 95% CI: -15.42 to -4.98). In addition, the intraclass correlation coefficient and minimal detectable change for MIP were 0.96; 95% CI: 0.93-0.97, and 17.70, respectively. CONCLUSION: Inspiratory muscle training protocol combined with manual therapy and motor control exercise had greater effect in enhancing MIP than did IMT in isolation in moderate smokers in the short term. In addition, both groups experienced changes in MIP but not in lung function.

Role of tube size and intranasal compression of the nasotracheal tube in respiratory pressure loss during nasotracheal intubation: a laboratory study.

BACKGROUND: Small nasotracheal tubes (NTTs) and intranasal compression of the NTT in the nasal cavity may contribute to increasing airway resistance. Since the effects of size, shape, and partial compression of the NTT on airway resistance have not been investigated, values of airway resistance with partial compression of preformed NTTs of various sizes were determined. METHODS: To determine the factors affecting the respiratory pressure loss during the nasotracheal intubation, physical and fluid dynamics simulations were used. The internal minor axes of NTTs in the nasal cavity of intubated patients were measured using dial calipers. In physical and fluid dynamics simulations, pressure losses through the tubular parts, compressed parts, and slip joints of NTTs with internal diameters (IDs) of 6.0, 6.5, 7.0, 7.5, and 8.0 mm were estimated under partial compression. RESULTS: The median internal minor axes of the 7.0- and 7.5-mm ID NTTs in the nasal cavity were 5.2 (4.3-5.6) mm and 6.0 (4.2-7.0) mm, respectively. With a volumetric air flow rate of 30 L/min, pressure losses through uncompressed NTTs with IDs of 6.0-, 6.5-, 7.0-, 7.5- and 8.0-mm were 651.6 ± 5.7 (6.64 ± 0.06), 453.4 ± 3.9 (4.62 ± 0.04), 336.5 ± 2.2 (3.43 ± 0.02), 225.2 ± 0.2 (2.30 ± 0.00), and 179.0 ± 1.1 Pa (1.82 ± 0.01 cmH2O), respectively; the pressure losses through the slip joints were 220.3 (2.25), 131.1 (1.33), 86.8 (0.88), 57.1 (0.58), and 36.1 Pa (0.37 cmH2O), respectively; and the pressure losses through the curvature of the NTT were 71.6 (0.73), 69.0 (0.70), 64.8 (0.66), 32.5 (0.33), and 41.6 Pa (0.42 cmH2O), respectively. A maximum compression force of 34.1 N increased the pressure losses by 82.0 (0.84), 38.0 (0.39), 23.5 (0.24), 16.6 (0.17), and 9.3 Pa (0.09 cmH2O), respectively. CONCLUSION: Pressure losses through NTTs are in inverse proportion to the tubes' IDs; greater pressure losses due to slip joints, acute bending, and partial compression of the NTT were obvious in small NTTs. Pressure losses through NTTs, especially in small NTTs, could increase the work of breathing to a greater extent than that through standard tubes; intranasal compression further increases the pressure loss.

Maximal expiratory pressure and Valsalva manoeuvre do not produce similar cardiovascular responses in healthy men.

NEW FINDINGS: What is the central question of this study? This is the first study to evaluate and describe the cardiovascular responses during maximal expiratory pressure compared with the Valsalva manoeuvre, and whether those responses are similar. What is the main finding and its importance? This study showed that the duration of the manoeuvres appears to be responsible for the different physiological mechanisms involved in the cardiovascular responses to each manoeuvre and that the intensity of expiratory effort was related to the response in maximal expiratory pressure. These results are important to identify the risks to which subjects are exposed when performing these manoeuvres. The main purpose of this study was to compare the cardiovascular responses between the Valsalva manoeuvre (VM) and maximal expiratory pressure (MEP) and to evaluate the effect of age on these responses. Twenty-eight healthy men were evaluated and divided into two groups, younger (n = 15, 25 ± 5 years) and middle aged (n = 13, 50 ± 5 years), and they performed the VM and MEP measurement. The VM consisted of an expiratory effort (40 mmHg) against a manometer for 15 s, and the MEP was performed according to American Thoracic Society guidelines. The cardiovascular responses were analysed at rest, isotime (3 s), peak, nadir and recovery, and the cardiovascular variations (Δ) were calculated as peak or isotime minus resting values. For the statistical analysis, we used two-way ANOVA (P < 0.05). We observed that MEP and the VM generate similar changes in cardiac output (P > 0.05), but MEP presents higher values for mean arterial pressure (MAPPeak , MAPIsotime , ΔMAP and ΔMAPIsotime ) than those observed in the VM (P < 0.05). The execution time of the manoeuvres (VM ∼15 s and MEP ∼5 s) appears to be largely responsible for the activation of different physiological mechanisms involved in the cardiovascular control for each manoeuvre, and the intensity of expiratory effort is related to the higher response of MAP and peripheral vascular resistance (PVRIsotime and ΔPVRIsotime ) during MEP (P < 0.05). Moreover, it appears that age affects only the heart rate and PVR responses (P < 0.05), which were higher in the young and middle-aged group, respectively. Based on these findings, we can conclude that MEP and the VM do not generate similar cardiovascular responses, except for cardiac output.

Relationship between inspiratory muscle strength and balance in women: A cross-sectional study.

BACKGROUND: There is scarce evidence on changes at the functional level associated with the respiratory area in women. This study aims to analyse the relationship between inspiratory muscle strength and balance in women. MATERIAL AND METHODS: In this cross-sectional observational study, the sample consisted of groups according to the results obtained in the balance test. Inspiratory muscle weakness was defined as maximum inspiratory pressure (MIP) ≤ 80% of the predictive value. MIP was carried out using through a mouthpiece, with an electronic manometer. Logistic regression model was used to examine if MIP predicts balance. RESULTS: 159 women participated in the study. Approximately 20% of them achieved balance ≤ 2 seconds and 18% presented MIP≤80%. MIP was associated with the time achieved in the one-leg support test. Subjects with MIP ≤ 80% of the predictive value show 3 times more risk of having a lower performance in the balance test (OR = 3.26). CONCLUSIONS: Inspiratory muscle weakness is associated with deficient balance in this sample. It shows the need for multidimensional assessment and rehabilitation strategies for patients identified as having MIP weakness and/or balance disorders.

Maximal inspiratory pressure is associated with health-related quality of life and is a reliable method for evaluation of patients on hemodialysis.

OBJECTIVE: To evaluate the association between Maximal Inspiratory Pressure (MIP) and health-related quality of life (HRQoL) and to verify the reliability of the MIP in patients on hemodialysis. METHODS: In a repeated-measures design, patients on hemodialysis performed MIP and specific HRQoL questionnaire (trial 1). The MIP was repeated after 6 to 8 weeks (trial 2) and reliability was assessed using Intra-class Correlation Coefficient. Standard Error of Measurement and Minimal Detectable Change scores were calculated. RESULTS: Sixty-one individuals (68.9% men) were evaluated in trial 1. MIP was associated with specific domains "Symptoms" (r = 0.45; R2 adjusted = 0.192) and the kidney disease component summary (r = 0.38; R2 adjusted = 0.138). Regarding generic domains, the MIP was associated with "Physical Functioning" (r = 0.57; R2 adjusted = 0.375) and Physical component summary (r = 0.47; R2 adjusted = 0.258). Thirty-three patients were randomly selected to perform a second MIP test (trial 2). The Intra-class Correlation Coefficient was 0.94 (95%CI 0.88-0.97). By Bland-Altman analysis, the bias was 3.2 cmH2O, which represents a difference of 3.7%. The Standard Error of Measurement and Minimal Detectable Change for MIP were 5.9 cmH2O and 13.8 cmH2O, respectively. CONCLUSION: The MIP is a reliable test, associated with physical domains of HRQoL in patients on hemodialysis. Thus, it is a useful method for respiratory evaluation in this population.

Ultrasonographic modeling of diaphragm function: A novel approach to respiratory assessment.

OBJECTIVES: Bedside ultrasound techniques have the unique ability to produce instantaneous, dynamic images, and have demonstrated widespread utility in both emergency and critical care settings. The aim of this article is to introduce a novel application of this imaging modality by utilizing an ultrasound based mathematical model to assess respiratory function. With validation, the proposed models have the potential to predict pulmonary function in patients who cannot adequately participate in standard spirometric techniques (inability to form tight seal with mouthpiece, etc.). METHODS: Ultrasound was used to measure diaphragm thickness (Tdi) in a small population of healthy, adult males at various points of the respiratory cycle. Each measurement corresponded to a generated negative inspiratory force (NIF), determined by a handheld meter. The data was analyzed using mixed models to produce two representative mathematical models. RESULTS: Two mathematical models represented the relationship between Tdi and NIFmax, or maximum inspiratory pressure (MIP), both of which were statistically significant with p-values <0.005: 1. log(NIF) = -1.32+4.02×log(Tdi); and 2. NIF = -8.19+(2.55 × Tdi)+(1.79×(Tdi2)). CONCLUSIONS: With validation, these models intend to provide a method of estimating MIP, by way of diaphragm ultrasound measurements, thereby allowing evaluation of respiratory function in patients who may be unable to reliably participate in standard spirometric tests.

Comparison of balance changes after inspiratory muscle or Otago exercise training.

The inspiratory muscles contribute to balance via diaphragmatic contraction and by increasing intra-abdominal pressure. We have shown inspiratory muscle training (IMT) improves dynamic balance significantly with healthy community-dwellers. However, it is not known how the magnitude of balance improvements following IMT compares to that of an established balance program. This study compared the effects of 8-week of IMT for community-dwellers, to 8-week of the Otago exercise program (OEP) for care-residents, on balance and physical performance outcomes. Nineteen healthy community-dwellers (74 ± 4 years) were assigned to self-administered IMT. Eighteen, healthy care-residents (82 ± 4 years) were assigned to instructor-led OEP. The IMT involved 30 breaths twice-daily at ~50% of maximal inspiratory pressure (MIP). The OEP group undertook resistance and mobility exercises for ~60 minutes, twice-weekly. Balance and physical performance were assessed using the mini Balance Evaluation System Test (mini-BEST) and time up and go (TUG). After 8-week, both groups improved balance ability significantly (mini-BEST: IMT by 24 ± 34%; OEP by 34 ± 28%), with no between-group difference. Dynamic balance sub-tasks improved significantly more for the IMT group (P < 0.01), than the OEP group and vice versa for static balance sub-tasks (P = 0.01). The IMT group also improved MIP (by 66 ± 97%), peak inspiratory power (by 31 ± 12%) and TUG (by -11 ± 27%); whereas the OEP did not. IMT and OEP improved balance ability similarly, with IMT eliciting greater improvement in dynamic balance, whilst OEP improved static balance more than IMT. Unlike IMT, the OEP did not provide additional benefits in inspiratory muscle function and TUG performance. Our findings suggest that IMT offers a novel method of improving dynamic balance in older adults, which may be more relevant to function than static balance and potentially a useful adjunct to the OEP in frailty prevention.

Maximal Dynamic Inspiratory Pressure Evaluation in Heart Failure: A Comprehensive Reliability and Agreement Study.

OBJECTIVE: The purpose of this study was to analyze the reliability (interrater and intrarater) and agreement (repeatability and reproducibility) properties of tapered flow resistive loading (TFRL) measures in patients with heart failure (HF). METHODS: For this cross-sectional study, participants were recruited from the cardiopulmonary rehabilitation program at the University of Brasilia from July 2015 to July 2016. All patients participated in the study, and 10 were randomly chosen for intrarater and interrater reliability testing. The 124 participants with HF (75% men) were 57.6 (SD = 1.81) years old and had a mean left ventricular ejection fraction of 38.9% (SD = 15%) and a peak oxygen consumption of 13.05 (SD = 5.3) mL·kg·min-1. The main outcome measures were the maximal inspiratory pressure (MIP) measured with a standard manovacuometer (SM) and the MIP and maximal dynamic inspiratory pressure (S-Index) obtained with TFRL. The S-Index reliability (interrater and intrarater) was examined by 2 evaluators, the S-Index repeatability was examined with 10 repetitions, and the reproducibility of the MIP and S-Index was measured with SM and TFRL, respectively. RESULTS: The reliability analysis revealed high S-Index interrater and intrarater reliability values (intraclass correlation coefficients [ICCs] of 0.89 [95% CI = 0.58-0.98] and 0.97 [95% CI = 0.89-0.99], respectively). Repeatability analyses revealed that 8 maneuvers were required to reach the maximum S-Index in 75.81% (95% CI = 68.27-83.34) of the population. The reproducibility of TFRL measures (S-Index = 68.8 [SD = 32.8] cm H2O; MIP = 66 [SD = 32.3] cm H2O) was slightly lower than that of the SM measurement (MIP = 70.1 [SD = 35.9] cm H2O). CONCLUSIONS: The TFRL device provided a reliable intrarater and interrater S-Index measure in patients with HF and had acceptable repeatability, requiring 8 maneuvers to produce a stable S-Index measure. The reproducibilities of the S-Index, MIP obtained with SM, and MIP obtained with TRFL were similar. IMPACT: TRFL is a feasible method to assess both MIP and the S-index as measures of inspiratory muscle strength in patients with HF and can be used for inspiratory muscle training, making the combined testing and training capabilities important in both clinical research and the management of patients with HF.

Driving Pressure: Defining the Range.

BACKGROUND: Recent literature suggests that optimization of tidal driving pressure (ΔP) would be a better variable to target for lung protection at the bedside than tidal volume (VT) or plateau pressure (Pplat), the traditional indicators of ventilator-induced lung injury. However, the usual range or variability of ΔP over time for any subject category have not been defined. This study sought to document the ΔP ranges observed in current practice among mechanically ventilated subjects receiving routine care for diverse acute conditions in a community hospital environment. METHODS: This was a retrospective, observational study in a university-affiliated and house staff-aided institution with respiratory care protocols based on extant lung-protective guidelines for VT. Demographic characteristics and measured parameters related to mechanical ventilation and hemodynamics were extracted from electronic records of intubated subjects for each 8-h period of the first 24 h in the ICU. Pplat values reported by the ventilator were validated by the respiratory therapist before those data were entered into the electronic medical record. RESULTS: The mean ΔP was significantly higher at Time 1 (mean 16.1, range 7.0-31.0 cm H2O) compared to both Time 2 (mean 14.5, range 7.0-35.0 cm H2O) (P < .001) and Time 3 (mean 14.8, range 8.0-32 cm H2O) (P < .001). At all time points, the median ΔP was higher for completely passive breathing compared to triggered breathing. The widest difference between presumed entirely passive and presumed intermittently or consistently triggered breaths occurred at Time 1 (mean ΔP = 17.2 vs 14.9 cm H2O, respectively) (P = .01). CONCLUSIONS: Suggested safety thresholds for ΔP are often violated by a strategy that focuses on only VT and Pplat. Our data suggest that ΔP is lower for passive versus triggered breathing cycles. Vigilance is especially important in the initial stages of mechanical ventilator support, and attention should be paid to triggering efforts when interpreting and comparing machine-determined numerical values for ΔP.

Inspiratory Muscle Training After Heart Valve Replacement Surgery Improves Inspiratory Muscle Strength, Lung Function, and Functional Capacity: A RANDOMIZED CONTROLLED TRIAL.

PURPOSE: The aim of this study was to analyze the effects of inspiratory muscle training (IMT) as a therapeutic strategy after heart valve replacement surgery (HVRS). METHODS: A double-blind, randomized, clinical trial that included patients undergoing elective HVRS, without post-operative complications, were allocated to 2 groups: IMT group (IMT-G) and IMT placebo group (IMT-PG). The IMT started 3 d after surgery and was performed twice daily for 4 wk. Lung function, maximum inspiratory pressure (MIP) as a measure of inspiratory muscle strength, functional capacity, and quality of life were assessed pre-operatively and at the end of training. RESULTS: The IMT-G recovered pre-operative MIP and lung function values after 4 wk of training. This group also increased the distance walked during the 6-min walk test (6MWD). In the IMT-PG, the values of MIP were below those found pre-operatively, with impairment of lung function and lower 6MWD in the final evaluation. At the end of IMT, MIP was correlated with the 6MWD and with the spirometry variables. CONCLUSIONS: IMT performed for 4 wk after HVRS was effective in restoring the values of inspiratory muscle strength and lung function to the pre-operative level and increasing the functional capacity assessed by the 6MWD. Furthermore, an association between lung function and functional capacity was observed, demonstrating the clinical relevance of the use of IMT in the rehabilitation process of these patients.

Effects of inspiratory muscle training on postural stability, pulmonary function and functional capacity in children with cystic fibrosis: A randomised controlled trial.

BACKGROUND: Previous research has found conflictive results regarding the benefits of inspiratory muscle training (IMT) for cystic fibrosis (CF) patients. Also, involvement of postural stability is a rising concern in chronic lung diseases but its role in CF patients is poorly understood. Our aim was to investigate the effects of IMT in CF patients as well as analysing the factors which may be related to postural stability. METHODS: Thirty-six children aged between 8 and 18 years with CF were randomly allocated to either "comprehensive chest PT" group (PT) or "IMT alongside comprehensive chest PT" group (PT+IMT). Both groups trained for 8 weeks. Dynamic and static postural stability tests on Biodex Balance system®, spirometry, respiratory muscle strength and 6-min walk distance (6MWD) was assessed at baseline and after 8 weeks of training. Determinants of postural stability was also analysed on baseline values. RESULTS: Maximum expiratory pressure (MEP) was found to be an independent predictor for overall limits of stability (LOS) score explaining %26 of variance (R = 0.514, p = 0.003). Overall LOS score, FVC, FEV1, peak expiratory flow, MEP and 6MWD significantly improved in both groups, with no significant differences between groups. Maximum inspiratory pressure (MIP) also improved in both groups but the magnitude of improvement in MIP was greater in PT+IMT group (38 cmH2O vs 13 cmH2O; p < 0.001). CONCLUSIONS: Combining IMT with chest PT failed to provide further improvements, except for MIP, suggesting that a comprehensive chest PT program may be individually effective in improving overall LOS score, spirometry, respiratory muscle strength and 6MWD. TRIAL REGISTRATION: www.ClinicalTrials.gov; registration number: NCT03375684.

Clinical implication of maximal voluntary ventilation in myotonic muscular dystrophy.

Patients with myotonic muscular dystrophy type 1 (DM1) tend to exhibit earlier respiratory insufficiency than patients with other neuromuscular diseases at similar or higher forced vital capacity (FVC). This study aimed to analyze several pulmonary function parameters to determine which factor contributes the most to early hypercapnia in patients with DM1.We analyzed ventilation status monitoring, pulmonary function tests (including FVC, maximal voluntary ventilation [MVV], and maximal inspiratory and expiratory pressure), and polysomnography in subjects with DM1 who were admitted to a single university hospital. The correlation of each parameter with hypercapnia was determined. Subgroup analysis was also performed by dividing the subjects into 2 subgroups according to usage of mechanical ventilation.Final analysis included 50 patients with a mean age of 42.9 years (standard deviation = 11.1), 46.0% of whom were male. The hypercapnia was negatively correlated with MVV, FVC, forced expiratory volume in 1 second (FEV1), and their ratios to predicted values in subjects with myotonic muscular dystrophy type 1. At the same partial pressure of carbon dioxide, the ratio to the predicted value was lowest for MVV, then FEV1, followed by FVC. Moreover, the P values for differences in MVV and its ratio to the predicted value between ventilator users and nonusers were the lowest.When screening ventilation failure in patients with DM1, MVV should be considered alongside other routinely measured parameters.

Beyond inspiratory muscle strength: Clinical utility of single-breath work capacity assessment in veterans with COPD.

BACKGROUND: Inspiratory muscle function in COPD has been traditionally described in terms of maximal inspiratory pressure (MIP). Arguably, however, is the day-to-day relevance of MIP, given that individuals rarely need maximal inspiratory forces to perform general tasks, but rather repeated breathing muscle contractions which demand endurance. The sustained maximal inspiratory pressure (SMIP) reflects the ability of the respiratory muscles to maintain force over time (i.e. single-breath work capacity). We investigated the relationships between SMIP and COPD-related clinical outcomes, hypothesizing that SMIP would have superior correlational and discriminatory value when compared to MIP. METHODS: 61 males with mild-to-very severe airflow obstruction underwent measures of spirometry, whole-body plethysmography, symptomatology, comorbidity, quality of life, exacerbations and mental health. MIP and SMIP were obtained via the Test of Incremental Respiratory Endurance. RESULTS: The mean ±â€¯SD MIP and SMIP were 77.2 ±â€¯22.9 cmH2O and 407.9 ±â€¯122.8 PTU. Both MIP and SMIP positively correlated with pulmonary function, with SMIP displaying the highest correlations. We found significant differences in spirometry, hyperinflation, symptomatology, exacerbation frequency, comorbidity, quality of life and anxiety in subjects grouped as having reduced or normal single-breath work capacity. Finally, significantly lower SMIP values were found in individuals with an IC/TLC ratio ≤25%. CONCLUSIONS: The assessment of SMIP appears to have superior clinical value than MIP in COPD. Our analyses revealed that subjects whose SMIP was reduced experienced more severe airflow obstruction, greater hyperinflation, as well as worse health and mental status with increased symptomatology and impaired quality of life.

Assessment of Maximum Dynamic Inspiratory Pressure.

BACKGROUND: Inspiratory muscle strength has been considered an important marker of ventilatory capacity and a predictor of global performance. A new tool has become available for dynamically evaluating the maximum inspiratory pressure (the S-Index). However, the proper assessment of this parameter needs to be determined. Thus, the aim of the present study was to investigate the number of inspiratory maneuvers necessary to reach a maximum and reliable S-Index and the influence of inspiratory muscle warm-up on this assessment. METHOD: We performed a retrospective study from the database of 432 healthy subjects who underwent S-Index tests and inspiratory muscle warm-up or sham. The effect of repeated maneuvers on the S-Index and the impact of inspiratory muscle warm-up were analyzed by using the intraclass correlation coefficient and unpaired t test. RESULTS: We analyzed 81 subjects, (55% men), mean ± SD age 38.1 ± 9.6 y, 43 subjects in the inspiratory muscle warm-up group. Maximum and reliable S-Indexes were reached at the eighth maneuver in both groups preceding inspiratory muscle warm-up or sham, 102 cm H2O (95% CI 95-109 cm H2O); intraclass correlation coefficient 0.96; P < .001. Only the inspiratory muscle warm-up group presented a significant increase in the S-Index after warm-up, 13.5 cm H2O (95% CI 10-17), P < .001. CONCLUSIONS: Eight maneuvers were necessary to reach maximum and reliable values of the S-Index preceding inspiratory muscle warm-up or sham. Moreover, inspiratory muscle warm-up preceding S-Index assessment improved inspiratory muscle performance.

Pulsus paradoxus.

OBJECTIVES: Reviewed the etiologies, pathophysiologic mechanisms, detection and clinical significance of pulsus paradoxus in various conditions. DATA SOURCE: We searched PubMed, EMBASE, and the CINAHL from inception to June 2017. We used the following search terms: Pulsus paradoxus, pericardial effusion, acute asthma, ventricular interdependence and so forth. All types of study were chosen. RESULTS AND CONCLUSION: Legendary physician Sir William Osler truly said that "Medicine is learned by the bedside and not in the classroom." Bedside history taking and physical examination should be an integral component of clinical teaching curriculum imparted to medical students. Pulsus paradoxus is a valuable physical sign seen in many clinical conditions. Pulsus paradoxus is defined by an inspiratory fall in systolic blood pressure of greater than 10 mm Hg. Two prototype examples of pulsus paradoxus are cardiac tamponade and acute asthma. Exaggerated swings of intrapleural pressure, bi-ventricular interactions and increase afterload of the left ventricle are few of the pathophysiological mechanisms involved in the causation of pulsus paradoxus. The sensitivity of pulsus paradoxus in the diagnosis of cardiac tamponade is very high. In acute asthma, it also correlates with the severity of airflow obstruction.