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PubMed2005

Inspiratory muscle training may increase peak inspiratory flow in chronic obstructive pulmonary disease.

BACKGROUND: When choosing a specific inhalation device for a chronic obstructive pulmonary disease (COPD) patient, the internal airflow resistance and the ability of the patient to overcome it and to create an optimal inspiratory flow are essential. OBJECTIVES: The purpose of the present study was to investigate: (1) the peak inspiratory flow (PIF) that a patient with COPD can generate while breathing through two dry powder inhalers and (2) whether in patients with low PIF specific inspiratory muscle training (SIMT) will increase the PIF and exceed the minimal PIF that is considered necessary to guarantee optimal lung deposition of the drug. METHODS: Inspiratory muscle strength and PIFs were measured in 60 patients with COPD. Then 28 patients with severe COPD and low PIF were randomized to receive SIMT or to a control group. RESULTS: With the Turbuhaler, 12 patients (20%) could not generate the optimal flow of 60 l/min. PIF correlated very well with maximal inspiratory mouth pressure (PI(max)) for the Diskus and the Turbuhaler, as well as for both males and females (p < 0.001). Following the training period, there was a statistically significant increase in the PI(max) in the training group. This increase was associated with a significant increase in the PIF. All patients overcame the minimal threshold PIF following the training. CONCLUSIONS: Some patients with severe COPD are not able to generate adequate flow to secure optimal lung deposition of the inhalation with the Turbuhaler. SIMT improves inspiratory muscle strength as well as PIF. Following 8 weeks of training, the optimal PIF enabling adequate lung deposition of the drug was attained in all the trained patients.

Aged↗
PubMed2006

Evaluation of inspiratory muscle function in a healthy austrian population--practical aspects.

BACKGROUND: There is no clear evidence whether inspiratory muscle strength (Pi(max)) is closely linked to inspiratory muscle endurance (T(lim)). Moreover, normal values of T(lim), measured by flow-resistive loads, have not been established. OBJECTIVES: We tried to find answers to the following questions: Is it possible to establish normative values of T(lim) when using flow-dependent, resistive loads? Are Pi(max) and Borg scale values predictors of T(lim)? Are anthropometric and spirometric data closely related to T(lim)? Is it really necessary to measure T(lim) in addition to Pi(max) when evaluating inspiratory muscle function? METHODS: Sixty-eight healthy Austrian volunteers between 17 and 75 years of age and with a sedentary lifestyle participated in our study. Pi(max) was defined as the maximal inspiratory mouth pressure, measured with a differential pressure transducer. T(lim) was determined as the time span until exhaustion, while breathing against a resistive loading device. RESULTS: Pi(max) values showed a low intra- and high interindividual variability for both sexes and were significantly age, weight and height dependent. For male subjects, Pi(max) was also significantly related to spirometric parameters. T(lim) values showed a very high interindividual variability, but a low intraindividual variability. Interestingly, no correlation was found between T(lim) and Pi(max), nor lung function parameters and age. CONCLUSIONS: The results indicate that both Pi(max) and T(lim) have to be determined when inspiratory muscle function is measured. Normal values for T(lim), evaluated by flow-resistive loads, cannot be satisfactorily established due to the high interindividual variability.

Adolescent↗
PubMedDate not supplied

Skin vasomotor reflexes during inspiratory gasp: standardization by spirometric control does not improve reproducibility.

Arteriovenous anastomoses (AVA) in skin microcirculation are mediated by the sympathetic stimuli. The inspiratory gasp test (IG test) triggers the sympathetic nervous system, resulting in a decrease in AVA skin blood flow, as measured by laser Doppler fluxmetry (LDF). We studied the reproducibility of the IG test under carefully standardized respiratory conditions. In each of 19 healthy (young) volunteers with a mean skin temperature during the experiment above 28 degrees C 13 IG tests were performed, either under spirometric control or uncontrolled and by using a negative pressure transducer. Starting the IG test end-inspiratory results in the most pronounced absolute LDF decrease [140 PU (70-490)], median (minimum-maximum) as compared to starting end-expiratory [100 PU (40-260)] and during inspiration [110 PU (50-350)], respectively, p < 0.001 and p < 0.001. Inspiration as fast as possible results in a larger absolute LDF decrease [150 PU (40-450)], compared to inspiration in 5 s [120 PU (60-340); p < 0.02] and in 10 s [130 PU (40-350); p < 0.05]. Continuously sucking negative mouth pressure results in a larger LDF decrease [140 PU (30-420)] in comparison with taking one deep breath and holding it for 10 s [110 PU (30-270); p < 0.01]. However, standardization of the IG test did not improve its reproducibility.

Adult↗
PubMed1986

Respiratory drive and timing during assisted ventilation in dogs.

In 8 anesthetized dogs, during isocapnic hyperoxia we studied the effect of assisted ventilation (AV) on ventilatory drive, inspiratory off-switch volume (Voff) and duration of inspiratory diaphragmatic activity (Tdi). Tidal volumes (Vt) during AV were double spontaneous Vt. Two electrodes were inserted in the diaphragm to obtain the electromyogram (EMG). The index of ventilatory drive was the EMG 0.3--i.e., the amplitude of the moving average EMG 300 ms after the onset of inspiratory activity. AV decreased EMG 0.3 but had no effect on Voff and Tdi. Vagotomy not only abolished the reduction in drive, but may have increased drive during AV.

Animals↗
PubMed1992

Phrenic nerve function in type 1 diabetic patients with diaphragm weakness and peripheral neuropathy.

Phrenic nerve latency was studied in 14 male type 1 diabetic patients with impaired diaphragm function and in 14 healthy control subjects. The diabetics showed significantly decreased values regarding inspiratory vital capacity and forced volume in 1 s compared with the control subjects. All other lung function parameters were similar in both groups. Although motor and sensory nerve conduction studies provided evidence for peripheral neuropathy in all patients, phrenic nerve latencies turned out to be normal. These results rule out a neuropathic disorder of the phrenic nerve. Thus, impaired diaphragm function in type 1 diabetic patients is not caused by phrenic neuropathy.

Adult↗
PubMed1993

Effect of intramuscular administration of thiazinamium and inhaled histamine on forced inspiratory volume in 1 s.

Twenty-one patients with symptoms suggestive of asthma were evaluated clinically by allergy skin tests, pulmonary function, and histamine inhalation challenge. In addition to the forced expiratory manoeuvres (FEV1), forced inspiratory manoeuvres (FIV1), were performed before and after intramuscular administration of thiazinamium (Multergan), a bronchodilator with markedly anticholinergic properties. The same lung function parameters (FEV1 and FIV1) were obtained before and after histamine inhalation challenge. The response after bronchodilatation in litres of FEV1 2.42 +/- 1.12 to 3.27 +/- 0.98 (mean +/- SD) was much larger than in FIV1 3.44 +/- 1.35 to 4.05 +/- 1.14 (p < 0.05). After histamine inhalation the observed decrease in FEV1 (2.65 +/- 0.99 to 2.06 +/- 0.89) was not so great as in FIV1 (3.76 +/- 1.09 to 2.90 +/- 1.15) (p < 0.02). These results suggest that patients often have more difficulty with inspiration rather than expiration.

Adolescent↗
PubMed1993

A new aerosol device for bronchial provocation tests.

A special new device for diagnostic (bronchoprovocation) and therapeutic aerosol application is described. It consists of a high quality nebulizer system combined with a 10-liter storage bag which serves as an aerosol 'conditioner' (saturated ambient temperature and pressure conditions) and as a holding chamber to increase the respirable aerosol fraction and hence pulmonary deposition (Pari Provocation Test I). It allows ten times better standardized pulmonary aerosol deposition compared with the generally used nebulizers for calculation of dose-response curves especially for asthma provocation and dilatation tests. If slow inspiratory vital capacity maneuvers are used, pulmonary deposition of about 100 mg aerosol is achieved in children and adults. This device is especially important when exact dosing (also for therapeutic reasons) is required in the expanding field of topical and systemic aerosol application to or via the lung.

Aerosols↗
PubMed1994

The influence of age, diagnosis, and gender on proper use of metered-dose inhalers.

Metered dose inhalers (MDIs) are widely used in clinical practice for administering pharmaceuticals targeted to the lung. It is well known that the inhalation technique used with MDIs can substantially influence the clinical response to inhaled medications. To determine the acceptability of MDI maneuvers, we studied 59 subjects (26 females and 33 males; age, 20 to 81 yr; mean age, 38 yr) to determine whether the MDI technique used by these individuals complied with published recommendations for acceptable inhalation technique. Measurements were made with an MDI adapter that contained an unobtrusive, lightweight, miniature sensing system. Inspiratory flow at the moment of MDI actuation (Va), the volume (integrated from airflow) at actuation as a fraction of total inspiratory volume (Va/VI), breath-holding time (tBH), and inspiratory volume as a fraction of FVC (VI/FVC) were determined from 59 uncoached inhalations. We defined an acceptable maneuver, based on published data, by four components: (1) inspiratory flow at actuation (Va) between 25 and 90 L/min; (2) actuation during early inspiration (0 < Va/VI < or = 0.20); (3) adequate breath-holding time (tBH > 4 s), and (4) a deep inhalation (VI/FVC > 0.50). For all subjects, only 25% of inhalation maneuvers met all four criteria for acceptability. We found that a significantly higher proportion of male than female subjects performed an acceptable MDI maneuver (43% versus 4%, p < 0.001). There were no significant differences in technique between younger and older subjects or between patients with a diagnosis of asthma or chronic obstructive pulmonary disease (COPD). We conclude that most patients use their MDIs incorrectly; females of all ages are much more likely to have improper MDI technique than are males.

Adult↗
PubMed1995

Rigid external resistances cause effort dependent maximal expiratory and inspiratory flows.

A fixed orifice or a fixed upper airway obstruction (UAO) causes an expiratory and inspiratory plateau-shaped limitation on maximal flow-volume (MEFV, MIFV) curves and, according to the classic concept, a MEF50/MIF50 ratio of 0.9-1.1. However, since maximal expiratory static transrespiratory pressures (PEmax,stat) are clearly greater than the inspiratory ones (PImax,stat), the pressures applied during forced expiration also must be expected to be greater than inspiratory pressures; therefore, the MEF should be larger than the MIF because orifice flow is effort-dependent. We investigated this hypothesis in seven healthy, nonsmoking male volunteers (mean age +/- 1 SD: 34 +/- 10 yr, FVC: 5.9 +/- 1.0 L, PEmax,stat: 168 +/- 16 cm H2O, PImax,stat: 107 +/- 33 cm H2O). They performed MEFV curves and MIFV curves through four different added resistances placed in between the pneumotachograph and the mouth (the orifice diameters ranged between 7.8 mm and 2.8 mm). During these maneuvers dynamic mouth pressures were also measured (PE and PI). We found that the MEF50/MIF50 ratios were significantly increased (p < 0.05) from a control value of 1.1 +/- 0.4 up to 1.5 +/- 0.3 with the resistances. For each added resistance the PE/MEF ratios and (-)PI/MIF ratios were situated on a single line corresponding with the pressure-flow (P/V) characteristics of the resistance. We concluded that external resistances cause a MEF50/MIF50 ratio of clearly more than 1 and that this is determined by the PE/(-)PI ratio, which in healthy subjects is markedly larger than 1.

Adult↗
PubMed1996

Inspiratory muscle strength and endurance in steroid-dependent asthma.

The adverse effect of long-term steroid treatment on respiratory muscle function remains controversial. We evaluated inspiratory muscle strength and endurance in steroid-dependent asthmatics in comparison with other asthmatics or with patients with chronic obstructive pulmonary disease exhibiting a comparable level of lung hyperinflation. Inspiratory muscle function was assessed by maximal inspiratory pressure (Pimax) and by an incremental inspiratory threshold loading test in 19 patients who had had steroid-dependent asthma (SDA) requiring a mean daily dose of 20.7 +/- 0.8 mg prednisone for 5 +/- 1.4 yr. They were compared with 16 healthy control subjects, 30 patients with COPD, and 16 patients with non-steroid-dependent asthma (NSDA). Pimax as percentage of predicted values (%Pimax) was not significantly different in patients with SDA (77 +/- 5%) or NSDA (83 +/- 6%) than in control subjects (93 +/- 4%). In contrast, %Pimax was lower in patients with COPD (59 +/- 4.4%) than in those with SDA or NSDA (p < 0.05) or the control subjects (p < 0.0001). A significant correlation was found between %Pimax and hyperinflation assessed by the FRC/TLC ratio (r = 0.42; p < 0.001). Inspiratory endurance, defined as the ratio of maximal peak inspiratory pressure sustained for 2 min to individual Pimax (Plim2/Pimax), was significantly lower in the SDA (43 +/- 3%; p < 0.0001), NSDA (65 +/- 4%; p = 0.01), and COPD (55 +/- 3%; p < 0.0001) groups than in the control group (76 +/- 2%). Plim2/Pimax was also lower in patients with SDA than in those with COPD (p = 0.0073) or NSDA (p < 0.0001). Hyperinflation plays a major role in inspiratory muscle dysfunction associated with obstructive lung disorders, but the finding of a significantly decreased endurance in patients with SDA when compared with patients with COPD, despite a lower level of hyperinflation in the former group, points to a deleterious effect of long-term corticosteroid treatment on inspiratory muscle function in asthmatics.

Asthma↗
PubMed1996

Effects of non-REM sleep on the response of respiratory output to varying inspiratory flow.

It has been shown in mechanically ventilated awake normal humans that increasing inspiratory flow rate (VI) exerts an excitatory effect on respiratory output. It is not known if this effect persists during sleep. To test this, seven normal adults were studied during wakefulness and non-rapid eye movement (non-REM) sleep. Subjects were connected through a nose mask to a volume-cycled ventilator in the assist/control mode, and VI was increased in steps (3 to 4 breaths each) from 30 to 70 L/min and then back to 30 L/min. VI pattern was square, and all breaths were subject-triggered. Forty-one trials during non-REM sleep and 10 during wakefulness were analyzed. Both during sleep and wakefulness minute ventilation increased and total breath duration (Ttot) decreased significantly in a graded and reversible manner as VI increased. These changes were complete in the first breath after VI transition. The response was significantly less during sleep than during wakefulness (p < 0.050; at 30 L/min Ttot, expressed as percent of that at 70 L/min, was 110.2 +/- 1.3% during sleep and 127.8 +/- 3.9% during wakefulness. During wakefulness, the rate of change in airway pressure before triggering the ventilator (dp/dt), an index of respiratory drive, increased significantly (p < 0.05) with increasing VI. During sleep dp/dt was not affected by VI changes. In four sleeping subjects the increase in VI was sustained for 1.5 to 2 min. There was no evidence for adaptation of the response; Ttot, averaged over the last three breaths, did not differ from that obtained with VI was sustained for only 3 to 4 breaths. We concluded that VI exerts an excitatory effect on respiratory output, mediated by a reflex neural mechanism, and the gain of this reflex is attenuated by sleep.

Adaptation, Physiological↗
PubMed1996

Comparison of cervical magnetic and transcutaneous phrenic nerve stimulation before and after threshold loading.

Brief supramaximal stimulation of the phrenic nerves (twitch) is considered a promising technique to detect diaphragmatic fatigue in humans. However, the most commonly employed methodology (transcutaneous stimulation) is technically difficult. Cervical magnetic stimulation is a recently described technique that is potentially simpler and may obviate some of the problems inherent with transcutaneous stimulation. The purpose of this study was to determine the ability of cervical magnetic stimulation to evaluate diaphragmatic function. Accordingly, we measured transdiaphragmatic pressure (Pdi) during transcutaneous and cervical magnetic stimulation of the phrenic nerves before and after a potentially fatiguing task; inspiratory threshold loading to task failure. During threshold loading, subjects generated approximately 60% of their maximal esophageal pressure with each breath until they could no longer reach the target pressure. At least 10 twitches were obtained during both transcutaneous and magnetic stimulation before and 10, 30, 60, and 120 min after threshold loading. Control twitch Pdi was significantly larger during magnetic stimulation compared with transcutaneous stimulation: 39.3 +/- 3.0 (mean +/- SE) versus 27.4 +/- 2.3 cm H2O, p < 0.0005. This increase in twitch Pdi was solely due to the esophageal component. Following threshold loading, a significant reduction in transcutaneous twitch Pdi was seen in only three of the 10 subjects. Mean transcutaneous twitch Pdi fell only slightly from 27.4 +/- 2.3 during control to 25.1 +/- 2.2 cm H2O at 10 min after loading (p < 0.004). In contrast, magnetic twitch Pdi was significantly reduced in nine of the 10 subjects following threshold loading. Mean magnetic twitch Pdi fell from 39.3 +/- 3.0 during control to 31.1 +/- 3.0 cm H2O at 10 min after loading (p < 0.0001). The average fall in twitch Pdi post-loading (expressed as a percentage of the control value) was significantly greater for magnetic stimulation compared with transcutaneous stimulation: 21.0 +/- 3.1 versus 7.8 +/- 2.9%, p < 0.0001. In summary: (1) in the fresh state, twitch Pdi is larger with magnetic stimulation compared with transcutaneous stimulation, and (2) transcutaneous and cervical magnetic twitch Pdi are affected differently by threshold loading to task failure.

Adult↗
PubMed1997

Maximal inspiratory pressures and dimensions of the diaphragm.

We postulated that the variation of maximal voluntary inspiratory pressures (PI,max and Pdi,max) among individuals largely reflects the variation of the structural attributes of the inspiratory muscles, in particular the muscular cross-sectional area of the diaphragm (CSAdi) and its axially projected area (A(thor)). To test this postulate, we measured PI,max in 36 healthy subjects, including 3 children and 15 weight-lifters, and Pdi,max in 11 subjects. Structural measurements by ultrasonography and anthropometric calipers were available as reported in the companion manuscript. We found a high degree of correlation of Pdi,max with diaphragm thickness (tdi), CSAdi, and CSAdi/A(thor) (r2 = 0.89, 0.89, and 0.77, respectively). PI,max was also correlated with diaphragm structural measurements, although less well. The weight-lifters had greater pressures, thicker diaphragms, and greater diaphragm maximal stress (sigma(max)) than adults of similar stature who had not trained with weights. We conclude (1) that both Pdi,max and PI,max reflect in part structural attributes of the respiratory muscles; (2) that the variation of maximal transdiaphragmatic pressures is largely attributable to the normal variation of diaphragm structure; (3) weight lifting increases diaphragm structure and pressures.

Adult↗
PubMed1997

Effect of elastic loading on variational activity of breathing.

To examine the effect of elastic loading on variational activity of breathing, we studied 11 healthy subjects breathing at rest and with inspiratory elastic loads of 9 and 18 cm H2O/L, applied randomly for 1 h each. Compared with rest, a load of 18 cm H2O/L decreased gross variability, quantitated as standard deviation, of tidal volume (VT) and expiratory time (TE) (p < 0.01 in both instances) but increased that of inspiratory time (TI) (p < 0.03). The autocorrelation coefficients at a lag of 1 breath for each breath component were not altered by elastic loading, although the number of breath lags with significant serial correlations for TE tended to increase with a load of 18 cm H2O/L (p = 0.08). A load of 18 cm H2O/L decreased only the fraction of variational activity of VT and TE due to uncorrelated, random behavior (white noise), while it increased that fraction for TI (p < 0.05 in each instance); the correlated and oscillatory fractions did not change. Uncorrelated random behavior constituted > 87% of the variance of each breath component, correlated behavior represented 3 to 11%, and oscillatory behavior represented < 1.5% during both rest and loaded breathing. Elastic loading changed the gross variability of each primary breath component by altering the random fraction of variational activity; it had no significant effect on the structured, correlated fraction. We speculate that the observed changes in variational activity may reflect an attempt by the controller to compensate for the increased load while simultaneously minimizing load-induced dyspnea.

Adult↗
PubMed1997

Inspiratory muscle mechanics of patients with chronic obstructive pulmonary disease during incremental exercise.

Inspiratory muscles are weak and contribute to exercise limitation in chronic obstructive pulmonary disease (COPD). Differential inspiratory pressure contributions from the diaphragm and inspiratory rib cage muscles (RCMs) during exercise in patients with COPD patients are insufficiently described. We measured, in 16 patients with COPD, the global inspiratory muscle pressure (delta Pmus) and transdiaphragmatic pressure (delta Pdi) during an incremental bicycle exercise to exhaustion. The pressures needed to overcome the elastic load were further partitioned into portions for overcoming the PEEPi-imposed inspiratory threshold load (before the beginning of inspiratory flow) and for inflating the respiratory system (between the beginning and end of inspiratory flow). The delta Pdi/delta Pmus ratio was used to quantify the pressure contribution from RCMs relative to that from the diaphragm for a given inspiratory effort. We observed that in patients with COPD during exercise (1) there is a progressive increase in total inspiratory pressure contribution from RCMs relative to that of the diaphragm, and the magnitude of this increase appears to depend on the RCMs reserves during resting breathing; (2) most of the diaphragmatic pressure contribution occurs before the beginning of inspiratory flow, to overcome the PEEPi-imposed inspiratory threshold load; (3) RCMs pressure contribution predominates during the period of inspiratory flow once PEEPi is neutralized, not only for overcoming the elastic load caused by increased tidal volume, but also for compensating for the diaphragmatic pressure contribution during this interval that was gradually lost with increasing exercise work load.

Exercise Test↗
PubMed1998

Effects of flow triggering on breathing effort during partial ventilatory support.

The effects of flow triggering (FT) as compared with pressure triggering (PT) on breathing effort have been the focus of several studies, and discrepant results have been reported. In the initial part of our study, a lung model was used to quantify triggering effort (airway pressure-time product, PTPaw) for a range of sensitivity settings in nine new-generation ventilators. A ventilator providing both FT and PT was then used to compare these systems during pressure-support (PSV) and volume-targeted assist-control ventilation (ACV) in eight ventilator-dependent patients, using sensitivity settings (2 L/min for FT and -2 cm H2O for PT) that had proven significantly different in the initial bench study. Indexes of effort included the esophageal and transdiaphragmatic pressure-time products and inspiratory work of breathing per minute (PTPes/min, PTPdi/min, and Wi/min, respectively). The experimental study revealed significant differences between ventilators in PTPaw at commonly used settings. In two of three ventilators featuring both systems, PTPaw was significantly lower with FT than PT (p < 0.001). In the clinical study, FT as compared with PT, was associated with reductions in all indexes of breathing effort during PSV: 16 +/- 6% (p < 0.001), 13 +/- 10% (p < 0.01), and 14 +/- 12% (p < 0.05) for PTPdi/min, PTPes/min, and Wi/min, respectively. By contrast, no differences were found when FT was used during ACV. Although FT reduced triggering effort in both modes (p < 0.001), the effects observed during the post-trigger phase differed, and explained the discrepant results between the two modes. We conclude that FT more effectively reduces breathing effort when used in conjunction with a pressure-targeted mode than with a volume-targeted mode, especially when flow delivery is close to or below demand.

Aged↗