Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Inspiratory Capacity”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 937 records · Page 52Linked to original sources
PubMed2006

Gender differences in the fatigability of the inspiratory muscles.

PURPOSE: The purpose of the present study was to determine whether gender differences are present in the fatigability of the inspiratory muscles of humans. Based on evidence for a gender difference in the oxygen cost of breathing, we hypothesized that females would result in a greater magnitude and/or faster rate of inspiratory muscle fatigue than males. METHODS: Eleven females and males (N = 22) performed resistive breathing at a target pressure of 70% of maximal inspiratory pressure (PImax). Rate of inspiratory muscle fatigue was calculated from measures of PImax taken every 2 min during resistive breathing, and recovery of inspiratory muscle strength was assessed up to 45 min following task failure. RESULTS: Resting PImax was found to be lower for females than males (F:137.0 +/- 7.6 cm H2O; M:172.5 +/- 9.8 cm H2O, mean +/- SE, P </= 0.05). During resistive breathing, females exhibited a slower absolute and relative rate of muscle fatigue than males (F: 1.5 +/- 0.4 cm H2O.min(-1); M: -2.9 +/- 0.3 cm H2O.min(-1); P </=0.05). Females and males resulted in a similar decrease in PImax at task failure (15%), and no gender difference was found for recovery of inspiratory muscle strength. Separate analyses were performed in a subgroup of females and males that were matched for resting PImax. Females demonstrated a slower rate of fatigue and less muscle fatigue at task failure than males. No gender difference was found in time to task failure or the recovery of inspiratory muscle strength. CONCLUSION: The results provide some evidence that the fatigability of the inspiratory muscles is different between genders. Females demonstrated a slower rate of fatigue during resistive breathing than males, a finding independent of muscle strength.

Adult↗
PubMed1991

Measurement of maximal static respiratory pressures at the mouth with different air leaks.

The effect of two different circuit leaks on the measurement of maximal static inspiratory and expiratory pressures at the mouth (Pimax, Pemax) was assessed in 70 patients with respiratory disease. Patients were divided into three groups with similar anthropometric and spirometric characteristics. The first group (30 patients) had their Pmax measured with a leak of 2.0 mm internal diameter (ID) and 37 mm length (as proposed by T. Ringqvist) and repeated with a second leak of 1.0 mm ID and 15 mm length (as recommended by J. L. Clausen). The two measurements were done in random order. Measurements for the other two groups (20 patients each) were taken with one or another, the two leaks randomly alternated with no leak. Pimax measurements obtained with Ringqvist's leak were 17 percent (p less than 0.005) lower than those with Clausen's leak and 22 percent (p less than 0.005) lower than those with no leak. Pemax measurements performed with Ringqvist's leak in place were 11 percent (p less than 0.005) lower than those with Clausen's leak and 11 percent (p less than 0.005) lower than those obtained with no leak. The comparison between Clausen's leak and no leak showed no statistically significant difference. We conclude that whenever the effect of pressure generated in the mouth is to be avoided in the measurement of respiratory Pmax, a leak of the size proposed by Ringqvist is to be preferred.

Asthma↗
PubMed1994

High- vs low-intensity inspiratory muscle interval training in patients with COPD.

This study determined the effect of a high vs low resistive inspiratory muscle interval training protocol on inspiratory muscle strength (PImax), incremental inspiratory threshold loading (Pitl), inspiratory muscle endurance (IE), and 12-minute distance test (12 MD) in severely impaired patients with COPD. We used a double-blind, two-group, repeated-measure design. Group 1 (n = 12) received supervised high resistive loading at approximately 52 percent PImax and group 2 (n = 8) received supervised low resistive loading at approximately 22 percent PImax. All subjects trained three times weekly (progressing from 5 min per session in week 1 to 18 min per session in week 12) for 12 weeks. After three practice sessions, measures of PImax, Pitl, IE, and 12 MD were taken at baseline, at 4-week intervals, and within 72 h of completing the protocol. Group 1 showed significant improvement in all four dependent variables while group 2 improved in Pitl, IE, and 12 MD. The results suggest there is no significant difference between high and low resistive interval training in more severely impaired patients with COPD.

Aged↗
PubMed1996

Short-term effects of inhaled beta-adrenergic agonist on breathlessness and central inspiratory drive in patients with nonreversible COPD.

In patients with COPD, a relationship between breathlessness and respiratory effort, assessed in terms of mouth occlusion pressure (P0.1), has been described. To evaluate the short-term effects of inhaled terbutaline on breathlessness, breathing pattern, and P0.1 in patients with nonreversible COPD, we designed a randomized, double-blind, parallel, placebo-controlled study. Twenty-five patients with stable nonreversible COPD, mean age 64 +/- 11 years, were enrolled in the study. Patients received 500 micrograms inhaled terbutaline or placebo. Breathlessness, using the Borg scale, breathing pattern, and P0.1 were measured at baseline and 30 min after inhalation. Terbutaline resulted in a significant decrease in Borg scale, while no differences were observed after placebo. No significant changes in breathing pattern were found. Nevertheless, a decrease in P0.1 (0.31 +/- 0.07 vs 0.21 +/- 0.05 kPa; p < 0.001) after terbutaline inhalation was observed. Borg score was correlated with P0.1 in all patients. Moreover, changes in Borg score after medication were directly proportional to P0.1 changes (r = 0.85; p < 0.01). We conclude that terbutaline decreases central inspiratory drive and improves breathlessness in patients with nonreversible COPD.

Administration, Inhalation↗
PubMed1997

Applied PEEP during pressure support reduces the inspiratory threshold load of intrinsic PEEP.

OBJECTIVES: Mechanical ventilation in patients with obstructive airway disease (OAD) is associated with the development of dynamic hyperinflation and intrinsic positive end-expiratory pressure (PEEPi). One of the effects of this form of PEEPi is to act as an inspiratory threshold load that can produce ineffective breath triggering, dyspnea, and muscle fatigue. Recently it has been shown that applying PEEP in the ventilator circuit can reduce this imposed triggering load. We wished to investigate this further by studying patients with OAD being weaned with pressure support (PS) ventilation. Our first objective was to determine the prevalence and magnitude of this form of PEEPi in OAD patients who were clinically judged to be capable of triggering mechanical ventilatory breaths. Our second objective was to attempt to reduce the triggering load by applying circuit PEEP and then observe the response of patient-ventilator interactions during the patient-triggered, pressure-limited PS breath. DESIGN: Thirteen random patients with OAD who were receiving PS ventilation were studied by measuring airway pressures, airway gas flow, baseline esophageal pressure, esophageal pressure time products (PTP), and esophageal pressure changes before ventilator gas delivery began (delta Pes taken to represent PEEPi). Measurements were made at baseline and after stepwise increases in circuit PEEP up to the PEEPi. RESULTS: We found measurable PEEPi in all patients (average +/- SD of 9.54 +/- 4.3 cm H2O) and it was > 10 cm H2O in seven patients. As would be predicted, we observed progressive reductions in PEEPi as applied PEEP was given. We also observed that the component of patient effort (PTP) related to overcoming PEEPi also decreased, but the PTP related to tidal volume (VT) did not. The VT associated with the set PS thus did not change with application of PEEP, nor did the breathing frequency. CONCLUSION: PEEPi is common in OAD patients receiving mechanical ventilatory support. The imposed triggering load from PEEPi can be offset to large extent by circuit PEEP approaching the baseline PEEPi. Although total patient effort substantially falls with applied PEEP, the patient effort that combine with PS to effect VT does not.

Female↗
PubMed1997

How many maneuvers are required to measure maximal inspiratory pressure accurately.

OBJECTIVE: To determine whether performing more maximal inspiratory pressure (MIP) maneuvers per test provides a more accurate assessment of the true maximal inspiratory strength. DESIGN: Review of MIP data from 367 tests. Each subject was encouraged to perform 20 MIP maneuvers per test, unless the patient reached the highest measurable pressure three times, or because of poor cooperation, fatigue, or respiratory distress. From the same raw data, MIP was calculated in two ways: (1) the "short MIP" was defined as the average of the first three highest values with < or = 5% variability; the results from further maneuvers were ignored; and (2) the "long MIP" is defined as the average of the three highest values with < or = 5% variability from all recorded maneuvers. SETTING: Pulmonary Physiology Laboratory, Childrens Hospital Los Angeles. PARTICIPANTS: One hundred seventy-eight pediatric and adult subjects (age, 14 +/- 3 [SD] years; 53% male) with suspected inspiratory muscle weakness. MEASUREMENTS AND RESULTS: The long MIP (91 +/- 39 cm H2O) was significantly greater than the short MIP (82 +/- 39 cm H2O) (p < 0.000005). In 177 of 367 tests, the short MIP underestimated the peak performance. CONCLUSIONS: From the same raw data, the long MIP was significantly greater than the short MIP. In 48% of the tests, the short MIP method underestimated the peak performance determined by the long MIP method. We speculate that the difference between the long MIP and the short MIP can be attributed to a learning effect.

Adolescent↗
PubMed1997

Implantation of Accuflex and Strecker stents in malignant bronchial stenoses by flexible bronchoscopy.

Silicone and metal stents are available for the treatment of malignant bronchial stenoses. This project sought to compare the self-expanding nitinol Accuflex stent (Boston Scientific Corp; Watertown, Mass) with the passively expandable tantalum Strecker stent (Boston Scientific Corp; Watertown, Mass), both implanted by flexible bronchoscopy under local anesthesia and sedation. In 51 patients with malignant bronchial stenosis, 14 nitinol and 51 tantalum stents were used and stenoses of 75 to 100% were treated. The intervention was successful in all but one patient; a mean patency of 93% was achieved. In the follow-up period, the probability of survival was significantly lower in patients with total bronchus occlusion than in patients with stenotic alterations (44 vs 109 days; p<0.05). In 10 patients, lung function analysis after stent implantation revealed a significant increase in PaO2 (65 vs 71 mm Hg; p<0.01), inspiratory vital capacity (2.5 vs 2.7 L; p<0.05), and FEV1 (1.8 vs 2.0 L; p<0.05). Mucus retention was the main (39%) adverse factor in the early phase after stent implantation, whereas tumor penetration became the most frequent problem (67%) in the later phase. Recanalizing interventions were necessary in 18% of the cases in which tumor penetration occurred. Stent distortion occurred in 12 patients with Strecker and in none with Accuflex stents. In comparison to the Strecker stent, the self-expanding Accuflex stent is preferable owing to its excellent flexibility and faster delivery system. Both types of stents could be sufficiently deployed within the lesion and allowed for highly precise positioning. Furthermore, no general anesthesia was required. The fiberbronchoscopic mode of implantation under sedation is very efficient even for tumor patients with severe impairment of their physical and respiratory condition.

Alloys↗
PubMed1998

Effect of body posture on spirometric values and upper airway obstruction indices derived from the flow-volume loop in young nonobese subjects.

STUDY OBJECTIVE: To define the effect of changes in body posture on flow-volume loops (FVLs) and four commonly used indices of upper airway obstruction (UAO) in young, nonobese normal subjects. DESIGN: Prospective comparative study. SETTING: Pulmonary function laboratory at an academic hospital. PARTICIPANTS: Thirty-one normal volunteers. INTERVENTION: At least three FVLs per posture were obtained in the sitting, supine, and left and right lateral recumbent postures while maintaining a constant position of the head and neck in relation to the trunk. In each body posture, the largest observed flow rates were used to calculate the UAO indices. RESULTS: When subjects changed from the sitting to each of the three recumbent postures, all spirometric values decreased significantly (p<0.0001). However, among the four UAO indices, only the FEV1/peak expiratory flow ratio increased significantly (although only slightly, by 2.9 and 4.4%, respectively) in both the right and left lateral recumbent postures (p<0.0001), but not in the supine posture. None of the subjects developed an inspiratory or expiratory plateau on the FVL in any of the three recumbent postures. CONCLUSIONS: In young, nonobese normal subjects, recumbency does not induce UAO, at least not detectable by changes in the FVL configuration or in UAO indices derived from the FVL. Furthermore, the study provides the upper limits of recumbency-related changes in the various UAO indices for young, nonobese normal subjects.

Adult↗
PubMed1998

Inspiratory flow rate and dynamic lung function in cystic fibrosis and chronic obstructive lung diseases.

STUDY OBJECTIVES: The peak inspiratory flow rates (PIFRs) generated by cystic fibrosis (CF) and COPD patients through a range of clinically relevant resistances have not yet been reported (to our knowledge). The objectives of this study were to (1) explore a relevant range of resistive loads and address whether patients with stable CF and COPD can generate the PIFR sufficient to disperse dry-powder inhalants (DPI) and (2) determine whether the optimal inspiratory flow rate effective for delivery of aerosolized pharmacologic therapeutic agents can be attained with a comfort rating acceptable to subjects. DESIGN: Prospective, controlled, subject-blinded study. SETTING: Pulmonary function laboratory at the VA Palo Alto Health Care System. PATIENTS OR PARTICIPANTS: Thirty-six subjects, including 12 healthy volunteers, 12 subjects with CF, and 12 subjects with COPD were studied. MEASUREMENTS: Studies of dynamic lung function and PIFR without and with varying resistances were obtained at a single laboratory visit. RESULTS: Dynamic lung function and PIFR varied inversely with the resistive load for all patient groups and did not correlate with the disease severity, as indicated by FEV1 of percent predicted. The average subjective comfort rating for any given resistive load was similar for subjects with CF and COPD. CONCLUSIONS: These results support the conclusion that subjects with stable CF and COPD of varying severity can comfortably generate the necessary flow rates to operate new and currently available DPIs over a wide range of inspiratory resistances.

Adolescent↗
PubMed1999

The unidirectional valve is the best method to determine maximal inspiratory pressure during weaning.

OBJECTIVES: Although maximal inspiratory pressure (MIP) is used as an index of inspiratory muscular strength, there is no consensus on how to measure it. We compared, during weaning from mechanical ventilation, two methods of measurement to determine which shows the greater values (MIPbest) and is more reproducible. One method measured MIP when negative pressure was maintained for at least 1 s after a forceful expiration, and the other method measured MIP with a unidirectional expiratory valve (MIPuni). DESIGN: The study had a crossover design, and patients randomly performed three measurements of each method (t1). The procedure was repeated by the same observer after 20 min (t2). The maximal value in each method was considered. SETTING: ICU, Hospital A.C. Camargo, São Paulo, Brazil. PATIENTS: Fifty-four consecutive patients undergoing short-term mechanical ventilation who became eligible for the study when their physicians decided to restore spontaneous breathing. RESULTS: MIPbest values were arrived at using MIPuni 75% of the time either in tl or t2. MIPuni yielded a higher average of MIPbest values in t1 and t2 (p < 0.0001). The effort-to-effort coefficient of variation of one method compared with the other during t1 and t2 was similar (p > 0.2 for t1; p > 0.8 for t2). Also, when comparing tl and t2, the coefficients of variation were similar for each method (p > 0.62). CONCLUSIONS: Because MIPuni displayed the maximal values, it is the best method for estimating MIP in patients undergoing short-term mechanical ventilation. The reproducibility of consecutive measurements was similar between the methods, even after a short period of time.

Adult↗
PubMed1999

The effect of varying inspiratory to expiratory ratio on gas exchange in partial liquid ventilation.

BACKGROUND: In partial liquid ventilation (PLV), the nondependent lung was observed to be inflated first and the dependent lung later. The inflational time difference between the lung regions can lead to maldistribution of tidal gas and inefficient gas bubbling in the slow-inflating region during PLV. In this situation, increasing the inspiratory to expiratory (I:E) ratio of the mechanical ventilator would lessen the heterogeneity of regional ventilation and improve gas exchange possibly to a greater degree than in gas ventilation (GV). DESIGN AND SETTING: Animal study at the Asan Institute for Life Sciences, Seoul, Korea Subjects: Eighteen rabbits (2.6 +/- 0.5 kg) with acute lung injury by saline solution lavage. INTERVENTIONS: Three I:E ratios were tried in GV and then in PLV. I:E ratios were changed by adjusting pause (1:2, 1:1, and 2:1; group 1) or by adjusting inspiratory flow rate (1:3, 1:1, and 2:1; group 2). MEASUREMENTS AND RESULTS: With increasing I:E ratio in all animals, PaO(2)/FIO(2) increased (80 +/- 24, 143 +/- 74, and 147 +/- 88 mm Hg; p = 0.001), and PaCO(2) decreased (74 +/- 15, 66 +/- 16, and 66 +/- 15 mm Hg; p = 0.006). The increases of PaO(2)/FIO(2) from 1:2/1:3 to 1:1 (p = 0.006) and from 1:1 to 2:1 (p = 0.036) were both greater in group 1 than in group 2. PaCO(2) decreased with increasing I:E ratio in group 1, but not in group 2. The change of PaO(2)/FIO(2) by varying the I:E ratio was 49 +/- 65% in PLV and 14 +/- 14% in GV (p = 0.003). CONCLUSIONS: Extending the I:E ratio, especially by adding pause, improved gas exchange in PLV. Oxygenation in PLV was affected by the I:E ratio to a greater degree than in GV.

Animals↗
PubMed2000

Reduction in tracheal lumen due to endotracheal intubation and its calculated clinical significance.

BACKGROUND: The flow in the human trachea is turbulent. Thus, the tracheal resistance (R) and the pressure gradient (DeltaP) required to maintain a given flow across the trachea is inversely related to its radius raised to the fifth power. If the caliber reduction ratio (X) after endotracheal intubation is calculated as X = radius of the endotracheal tube (rETT)/radius of the trachea (rT), then DeltaP and/or R will be increased by (1/X)(5). STUDY OBJECTIVES: To measure the actual ratio between rETT and rT following endotracheal intubation of pediatric patients with respiratory failure and to calculate the resulting increase in the tracheal R and DeltaP for a given inspiratory flow rate. DESIGN: Retrospective chart review. SETTING: Pediatric ICU in a tertiary-care teaching children's medical center. PATIENT ENROLLMENT: Twenty consecutive pediatric patients (mean [+/- SD] age, 6.4 +/- 7.2 years) whose tracheas had been intubated for various causes of respiratory failure, and who had received a CT scan, were included in our study. All patients received an endotracheal tube the size of which was derived from the following formula: (age in years/4) + 4. MEASUREMENTS AND MAIN RESULTS: rT and rETT were measured from CT scan sections at and around the level of the thoracic inlet, and the average values were used to calculate X. These values ranged from 0.33 to 0.65 (mean, 0. 55 +/- 0.8). The factor (1/X)(5) was calculated for each patient and then was multiplied by the known normal value for tracheal R for adolescents and adults (0.07 cm H(2)O/L/s) to obtain the value of R resulting from the artificial airway, (1/X)(5) x 0.07. Our results showed that tracheal R increased due to caliber reduction of the trachea after endotracheal intubation by 33.9 +/- 52.5-fold (range, 8.6- to 255.5-fold). In order to maintain an inspiratory flow of 1 L/s, the value of P for the intubated trachea would increase from 0. 07 cm H(2)O to a mean of 2.4 +/- 3.7 cm H(2)O (range, 0.6 to 18 cm H(2)O). In two of our patients, the rT/rETT ratios were < 0.5 (0.33 and 0.44, respectively); this translated into a more significant increase in the calculated DeltaPs, 18 and 4.2 cm H(2)O, respectively. CONCLUSIONS: : The common value of X due to endotracheal intubation is between 0.5 and 0.6, which in and of itself results in an increase in R across the intubated trachea up to 32-fold. The calculated increase in P as a result of this is between 2 and 3 cm H(2)O for adolescents or young adults. The addition of pressure support of at least 3 cm H(2)O during spontaneous ventilation via an endotracheal tube, which is common practice in pediatric critical care, should alleviate any respiratory distress emanating from the increased R. However, a value for X < 0.5, which was found in 10% of our patients (2 of 20 patients), results in a much higher calculated increase in the pressure gradient and, therefore, a higher level of pressure support is required to overcome this increase.

Adolescent↗
PubMed2000

Effects of fiberoptic bronchoscopy during mechanical ventilation in a lung model.

STUDY OBJECTIVES: To evaluate the effects of fiberoptic bronchoscopy (FOB) on delivered volumes and pressures during mechanical ventilation, utilizing a lung model. DESIGN: Bench study. SETTING: Laboratory. MATERIALS AND METHODS: Using varying-sized endotracheal tubes (ETTs), we ventilated a lung model at two levels of compliance utilizing different modes and parameters of ventilation. After establishing baseline measurements, the bronchoscope was inserted and measurements repeated. MEASUREMENTS AND RESULTS: During controlled mechanical ventilation (CMV) with a preset high-pressure limit (HPL), tidal volumes (VTs) were reduced from 700 mL to 0 to 500 mL following insertion of the bronchoscope. Increasing the HPL to 120 cm H(2)O resulted in a VT of 40 to 680 mL. Changing from square to decelerating flow waveform resulted in no consistent difference in VT. Auto-positive end-expiratory pressure (auto-PEEP) of 0 to 41 cm H(2)O was present under most conditions. Higher rates and lower peak inspiratory flows were associated with higher levels of auto-PEEP. In the pressure-control (PC) mode, using a preset inspiratory pressure level (IP), VT was reduced from 700 mL to 40 to 280 mL following insertion of the bronchoscope. Maximum IP (100 cm H(2)O) increased VT to 260 to 700 mL. Auto-PEEP was less in the PC mode. CONCLUSIONS: Extreme care must be taken when bronchoscopy is performed on a patient receiving mechanical ventilation. Extremely low VT and significant auto-PEEP may develop unless flow, respiratory rate, mode, and ETT size are carefully selected. The PC mode delivered more volume than did the CMV mode. When performing FOB during mechanical ventilation, the inside diameter of the ETT should be > or = 2.0-mm larger than the outside diameter of the bronchoscope to maintain volume delivery and minimize the development of auto-PEEP.

Airway Resistance↗
PubMed2001

Analysis of inspiratory flow shapes in patients with partial upper-airway obstruction during sleep.

STUDY OBJECTIVE: To study the spectrum of inspiratory flow signal shapes in patients with partial upper airway obstruction during sleep. DESIGN: We identified seven different inspiratory flow shapes and determined their frequencies in two groups of patients (10 postmenopausal women and 19 men after surgical treatment for sleep apnea) and in 9 control subjects. SETTING: Sleep research unit, Department of Physiology, University of Turku, Finland. MEASUREMENTS AND RESULTS: Nasal flow was recorded with nasal prongs. The shape analyses were performed with an automated attribute grammar recognizer. The inspiratory flow-shape distributions differed significantly between patients and control subjects. The flow shapes were also different between postmenopausal women and men after uvulopalatopharyngoplasty. CONCLUSIONS: The differences in the inspiratory flow-shape distributions between the control subjects and the two patient groups suggest that the upper airways behave differently in the three study groups. Automated inspiratory flow-shape analysis seems to be a promising tool to distinguish patient groups with different upper airway function to be treated with different treatment alternatives. The physiologic correlates of each flow-shape class remain to be elucidated.

Adult↗
PubMed2001

Assessing inspiratory muscle strength in patients with neurologic and neuromuscular diseases : comparative evaluation of two noninvasive techniques.

STUDY OBJECTIVES: Static mouth pressure during maximal inspiratory efforts is commonly used to evaluate inspiratory muscle strength. However, maximal inspiratory pressure (MIP) presents some potential limitations likely to be overcome by the measure of mouth pressure during a maximal sniff maneuver in patients with respiratory muscle weakness. The aim of the present study was to assess whether mouth pressure during sniff maneuver (Pmosn) is a better index of inspiratory muscle strength than MIP in patients with neurologic and neuromuscular diseases (NNMD) with and without inspiratory muscle weakness. SUBJECTS AND MEASUREMENTS: Both MIP and Pmosn were measured in 30 patients affected by various types of NNMD and in 41 control subjects. Pmosn was measured with a 5-cm latex balloon-catheter system, the balloon being held in the oral cavity with the lips closed. RESULTS: In control subjects, MIP was either similar (in female subjects) or higher (in male subjects) than Pmosn, the variation coefficients for the two tests being similar both in male subjects (19.3% vs 19.1% for MIP and Pmosn, respectively) and in female subjects (27.5% vs 26.2%, respectively). There was no difference in the Pmosn/MIP ratios observed in the different diseases (one-way analysis of variance, F = 0.29, p = 0.91). In control subjects, a significant inverse relationship between Pmosn/MIP ratio and MIP (r = - 0.66, p < 0.00001) was found, ie, the lower the MIP, the higher the Pmosn/MIP ratio, suggesting an increasing difficulty in performing MIP as MIP values decreased. The majority of patients were between the prediction limits of the regression calculated for control subjects. At variance, patients with Duchenne dystrophy and low MIP were under the prediction limits of the regression calculated for control subjects, indicating a lower-than-expected PMOSN. CONCLUSIONS: In patients with NNMD, irrespective of the etiology, we found the following: (1) Pmosn does not overcome the limitations of MIP measurement; (2) the two maneuvers are not interchangeable, but rather complement one another in the assessment of inspiratory muscle strength; (3) Pmosn may underestimate muscle strength as assessed by MIP in patients with NNMD with inspiratory muscle weakness; and (4) in patients with low MIP, the lower-than-expected Pmosn/MIP ratio confirms inspiratory muscle weakness.

Adult↗
PubMed2004

Bronchodilatory effect of deep inspiration is absent in subjects with mild COPD.

STUDY OBJECTIVES: To investigate whether the bronchodilatory effect of deep inspiration is impaired in subjects with COPD. METHODS: We measured deep inspiration-induced bronchodilation in 19 patients with COPD and 17 healthy subjects (mean age, 67.8 +/- 7.1 years vs 62.5 +/- 9.3 years, respectively [+/- SEM]). Each subject underwent a series of single-dose methacholine provocations to induce at least a 15% reduction in inspiratory vital capacity (IVC). When this was achieved, subjects were asked to perform four consecutive deep inspirations, after which the IVC measurement was repeated and the percentage of bronchodilation by deep inspiration was calculated. RESULTS: The percentage of reduction in IVC from baseline prior to the deep inspirations did not differ between the two groups (COPD, 20.1 +/- 1.6%; healthy, 22.7 +/- 2.4%; p = 0.38); median single methacholine doses employed were 20 mg/mL (range, 0.025 to 75 mg/mL) and 25 mg/mL (range, 10 to 75 mg/mL), respectively (p = 0.19). Deep inspirations were not able to reverse bronchoconstriction in patients with COPD (bronchodilation, 3.9 +/- 2.6%; p = 0.15 by one-sample t test). Bronchodilation by deep inspiration was present in healthy subjects (13.7 +/- 3.0%, p = 0.0003), and was significantly higher than that of patient with COPD (p = 0.02). In patients with COPD, deep inspiration-induced bronchodilation correlated with the percentage of predicted transfer factor of the lung for carbon monoxide (r = 0.53, p = 0.05), but not with airway obstruction, as assessed by FEV(1) or FEV(1)/FVC. CONCLUSIONS: The bronchodilatory ability of deep inspiration is lost in mild COPD. We speculate that the absence of deep inspiration-induced bronchodilation contributes to the development and severity of chronic respiratory symptoms in patients with COPD.

Aged↗
PubMed2004

Therapeutic responses in asthma and COPD. Bronchodilators.

The presence of acute reversibility to bronchodilators does not distinguish asthma from COPD. Patients with either condition can benefit from bronchodilators, and should be given a trial to assess their response. Some respond with a change in lung volume with less hyperinflation; others improve their forced inspiratory flow and become much more comfortable. The combination of long-acting beta-agonists (LABAs) and inhaled steroids is useful in both conditions. While anticholinergics seem to yield the best results in COPD, some patients with asthma benefit from their use. Tiotropium may be the most effective agent as monotherapy in COPD, but the combination of an inhaled steroid and a LABA may produce similar results in improving lung function. Long-acting bronchodilators are effective agents as monotherapy in COPD, but in asthma should be combined with a controller medication. Short-acting beta-agonists should be used intermittently in asthma, but may be used regularly or combined with an anticholinergic in COPD. The roles of stereoisomers, leukotriene receptor antagonists, and type 4 phosphodiesterase inhibitors in asthma and COPD remain uncertain at this time.

Adrenergic beta-Agonists↗