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PubMed2003

Comparison of effectiveness of pressure threshold and targeted resistance devices for inspiratory muscle training in patients with chronic obstructive pulmonary disease.

BACKGROUND AND PURPOSE: Previous studies have provided little information about the comparative efficacy of treatment with pressure threshold and targeted resistive inspiratory muscle training devices. This study compared the efficacy of these two types of inspiratory muscle training (IMT) devices on inspiratory muscle function, exercise capacity, and quality of life in patients with chronic obstructive pulmonary disease (COPD). METHODS: Forty two patients with moderate to severe COPD were randomly assigned to either a control group, a group receiving pressure threshold inspiratory muscle training, or a group receiving targeted resistive inspiratory muscle training. The training intensity was 50% of patients' maximal inspiratory pressure (MIP). Home-based training comprised two 15-minute sessions a day, 5 days a week for 8 weeks. Inspiratory muscle function measurement included MIP and inspiratory muscle endurance. RESULTS: Thirty patients completed the program, 10 from each group. Twelve patients were excluded because of changes in pharmacological regimen or admission to the hospital (n = 5), study withdrawal (n = 4), or poor compliance with the training program (n = 3). After training, a significant increase in endurance time was found for the threshold group and targeted resistive group (4.4 +/- 3.2 min and 3.0 +/- 2.9 min, respectively, both p < 0.05 vs control), with no significant difference between the 2 training groups. The 6-minute walking distance also increased significantly in both training groups (p < 0.05). CONCLUSIONS: Targeted resistive IMT with a controlled training load has a similar efficacy to the more popularly used pressure threshold IMT and can be incorporated in the treatment of COPD patients. The targeted resistance device offers a less expensive and easily used treatment choice.

Aged↗
PubMed2001

Anticipating mechanical ventilation in Guillain-Barré syndrome.

CONTEXT: The combination of multiple clinical factors culminates in neuromuscular respiratory failure in up to 30% of the patients with Guillain-Barré syndrome (GBS). Although guidelines exist as to when to proceed with intubation, early indicators of subsequent progression to respiratory failure have not been established. OBJECTIVES: To identify clinical and respiratory features associated with progression to respiratory failure and to examine patterns of respiratory decline in patients with severe GBS. DESIGN: Retrospective survey. SETTING: Tertiary care hospital. PATIENTS: One hundred fourteen consecutive patients with severe GBS admitted to the intensive care unit between January 1, 1976, and December 31, 1996. MAIN OUTCOME MEASURES: Early markers of impending respiratory failure, requirement for mechanical ventilation, and patterns of respiratory decline. METHODS: The clinical and electrophysiologic features of 60 patients receiving mechanical ventilation were compared with 54 patients with severe GBS who did not receive mechanical ventilation. Daily preventilation maximal inspiratory and maximal expiratory respiratory pressures and vital capacity were analyzed. Multivariate predictors of the necessity for mechanical ventilation were assessed using logistic regression analysis. RESULTS: Progression to mechanical ventilation was highly likely to occur in those patients with rapid disease progression, bulbar dysfunction, bilateral facial weakness, or dysautonomia. Factors associated with progression to respiratory failure included vital capacity of less than 20 mL/kg, maximal inspiratory pressure less than 30 cm H(2)O, maximal expiratory pressure less than 40 cm H(2)O or a reduction of more than 30% in vital capacity, maximal inspiratory pressure, or maximal expiratory pressure. No clinical features predicted the pattern of respiratory decline; however, serial measurements of pulmonary function tests allowed detection of those at risk for respiratory failure. CONCLUSIONS: While inherently unpredictable, the course of patients with severe GBS can, to some extent, be predicted on the basis of clinical information and simple bedside tests of respiratory function. These data may be used in the decisions regarding admission to the intensive care unit and preparation for elective intubation.

Adolescent↗
PubMed1980

Inspiratory muscle activity during induced hyperinflation.

We studied the relationship between inspiratory muscle activity and lung volume in 5 normal subjects in whom hyperinflation to 78-83% VC was induced with exgernal expiratory resistances. While breathing at this high lung volume the most negative pleural pressure (Ppl) during inspiration was -23.4 +/- 2.3 cm H2O (mean +/- 1 SE), whereas the maximum expiratory Ppl was -4.2 +/- 1.6 in four and +31 cm H2O in one subject. Using relaxation pressure-volume curves of the chest wall, we reasoned that in the 4 subjects inspiratory muscles showed a substantial persistence of activity throughout expiration. The minimum inspiratory muscle force (Pmus) during expiration was 35.9 +/- 8.4% of the peak inspiratory Pmus. Similarly, the work of the inspiratory muscles in expiration was 57.8 +/- 9.5% of the work during inspiration. In all 5 subjects the diaphragm relaxed almost completely in expiration, as evidenced by the transdiaphragmatic pressure (Pdi), which fell during expiration to 10.0 +/- 4.1% of the peak inspiratory Pdi. Inspiratory intercostal and scalene electromyographic recordings, obtained in 3 subjects, demonstrated substantial activity in expiration. We conclude that during external, resistive, expiratory loading the volume of hyperinflation is influenced by persistent activity of inspiratory muscles in expiration, and that this is due largely to the inspiratory intercostal and accessory muscles rather than the diaphragm.

Diaphragm↗
PubMed2006

Respiratory muscle strength and cough capacity in patients with Duchenne muscular dystrophy.

The function of inspiratory muscles is crucial for effective cough as well as expiratory muscles in patients with Duchenne muscular dystrophy (DMD). However, there is no report on the correlation between cough and inspiratory muscle strength. To investigate the relationships of voluntary cough capacity, assisted cough techniques, and inspiratory muscle strength as well as expiratory muscle strength in patients with DMD (n= 32). The vital capacity (VC), maximum insufflation capacity (MIC), maximal inspiratory pressure (MIP), and maximal expiratory pressure (MEP) were measured. Unassisted peak cough flow (UPCF) and three different techniques of assisted PCF were evaluated. The mean value of MICs (1918 +/- 586 mL) was higher than that of VCs (1474 +/- 632 mL) (p < 0.001). All three assisted cough methods showed significantly higher value than unassisted method (212 +/- 52 L/min) (F = 66.13, p < 0.001). Combined assisted cough technique (both manual and volume assisted PCF; 286 +/- 41 L/min) significantly exceeded manual assisted PCF (MPCF; 246 +/- 49 L/ min) and volume assisted PCF (VPCF; 252 +/- 45 L/min) (F = 66.13, p < 0.001). MIP (34 +/- 13 cmH2O) correlated significantly with both UPCF and all three assisted PCFs as well as MEP (27 +/- 10 cmH2O) (p < 0.001). Both MEP and MIP, which are the markers of respiratory muscle weakness, should be taken into account in the study of cough effectiveness.

Adolescent↗
PubMed2006

Vocal cord dysfunction concurrent with a nutcracker esophagus and the role of gastroesophageal reflux disease.

BACKGROUND: Psychological disorders were originally thought to be the sole cause of vocal cord dysfunction (VCD). Subsequently, other organic diseases, including structural laryngeal abnormalities, have also been reported to be associated with VCD. OBJECTIVES: To describe the first patient with VCD concurrent with a nutcracker esophagus and to establish the association between VCD and gastroesophageal reflux disease (GERD) by using the Bernstein test. METHODS: Symptom assessments, neuropsychiatric evaluations, fiberoptic laryngoscopy, pulmonary function tests, allergic skin prick tests, radiographs of the chest and sinuses, esophageal manometry (including 24-hour ambulatory esophageal pH monitoring), and the Bernstein test were performed. RESULTS: A 36-year-old woman had dyspnea, hoarseness, chest pain, and wheezes without relief for a decade. Neuropsychiatric evaluations disclosed mild depression. Fiberoptic laryngoscopy showed posterior laryngitis and paradoxical vocal cord adduction with audible inspiratory stridor. Pulmonary function tests showed attenuation of the inspiratory limb with notching in both flow-volume loops and a mid-vital capacity expiratory to inspiratory flow ratio of 4. All the symptoms except chest pain were improved dramatically by speech therapy and empirical treatment for GERD. Esophageal manometry revealed a nutcracker esophagus; 24-hour ambulatory esophageal pH monitoring demonstrated multiple short reflux episodes. The Bernstein test was conducted, and all the manifestations were reproduced with 0.1 N hydrochloric acid but not with isotonic sodium chloride infusion. CONCLUSIONS: This is the first human case report confirming that GERD can trigger an acute attack of VCD and may induce chest pain as a nutcracker esophagus in patients with VCD. It strengthens this association and expands our knowledge of diverse manifestations of this clinical entity.

Adult↗
PubMed2001

[Measurement of central respiratory drive and inspiratory muscles strength in patients with uremia].

OBJECTIVE: To investigate the changes of central respiratory drive and inspiratory muscles function in patients with uremia. METHODS: We performed the measurement of forced vital capacity (FVC), maximal voluntary ventilation (MBC), forced expiratory volume in one second (FEV1), peak expiratory flow (PEF), maximal midexpiratory flow (MMEF), expiratory flow of 25 per cent of FVC (V25), lung carbon monoxide diffusing capacity (DLco), maximal inspiratory mouth pressure (MIP) and airway occlusion pressure (P0.1) in 25 patients with uremia and 20 normal subjects. RESULTS: In patients with uremia, the FVC, MBC, FEV1, PEF, MMEF and V25 which reflect the lung ventilatory function and the DLco which reflects the lung diffusing function were significantly lower than those in normal subjects. The patients' MIP which reflects inspiratory muscles strength was significantly lower and their P0.1 which reflects the central respiratory drive was significantly higher, compared with the normal subjects'. CONCLUSION: Our findings suggest that on the basis of the disorder of ventilation and diffusing function of the lungs, the inspiratory muscles function of the patients with uremia is significantly decreased and the central respiratory drive of the patients is increased.

Aged↗
PubMed2006

C-reactive protein levels and clinically important predictive outcomes in stable COPD patients.

The aim of this study was to determine the relationship between C-reactive protein (CRP) levels and factors known to predict outcome in stable chronic obstructive pulmonary disease (COPD) patients. The following were studied in 130 stable COPD patients: spirometry, lung volume, arterial oxygen tension (P(a,O2)), dyspnoea, 6-min walk distance (6MWD), body mass index, fat-free mass index, BODE (body mass index, obstruction, dyspnoea and exercise capacity), health-related quality of life, smoking status, the presence of cardiovascular risk factors or disease, corticosteroid use and number of exacerbations in the previous year. CRP levels were measured in these patients and in 65 controls. Using univariate and multivariate analyses, any possible association with the predictors of outcomes was evaluated. CRP levels were higher in COPD patients than in controls (4.1 versus 1.8 mg.L(-1), respectively). Correlation was found with the following variables: forced expiratory volume in one second (FEV1; -0.23), FEV1 % (-0.20), forced vital capacity (FVC; -0.24), FVC % (-0.24), Global Initiative for Chronic Obstructive Lung Disease stage (0.17), BODE (0.17), inspiratory capacity/total lung capacity (-0.20), P(a,O2) (-0.40) and 6MWD (-0.30). Using multivariate analysis, P(a,O2) and 6MWD manifested the strongest negative association with CRP levels. C-reactive protein levels in stable chronic obstructive pulmonary disease patients are best correlated with arterial oxygen tension and 6-min walk distance. This should be considered when C-reactive protein levels are measured in stable chronic obstructive pulmonary disease patients.

Aged↗
PubMed1989

Flow-volume curves in snoring patients with and without obstructive sleep apnea.

To examine the usefulness of flow-volume curves as a screening test for the diagnosis of obstructive sleep apnea (OSA), we studied 405 consecutive patients referred for evaluation of possible OSA. All patients had full pulmonary function studies, which included measurements of maximal inspiratory and expiratory flow-volume curves, and nocturnal polysomnography, including continuous monitoring of snoring sounds. When the results were analyzed, of the 405 patients studied, 207 had OSA (apnea/hypopnea index [AHI] greater than 10) and 198 did not. Flow-volume curves were examined for the presence of upper airway obstruction defined as midvital capacity flow ratio (MVCFR = ratio of the maximal expiratory flow at 50% of vital capacity to maximal inspiratory flow at 50% of vital capacity) greater than 1.0. We found no significant difference in the values of MVCFR between the two groups: MVCFR was equal to 0.69 +/- 0.31 for nonapneic snorers, and 0.68 +/- 0.29 for the apneic snorers. Furthermore, we redefined the apneic and nonapneic groups using different cutoff values of AHI: 20, 30, 40, and 50. Independently of the AHI cutoff used, we found no significant difference in the MVCFR between the two groups. Linear regression analysis for the entire group of 405 patients revealed no significant correlation between MVCFR and the AHI or the snoring indices. We calculated the sensitivity, specificity, and predictive values of MVCFR for the diagnosis of OSA. We found that this test had 12% sensitivity, 86% specificity, 47% positive predictive value, and 46% negative predictive value.(ABSTRACT TRUNCATED AT 250 WORDS)

Female↗
PubMed2005

Respiratory muscle performance with stretch-shortening cycle manoeuvres: maximal inspiratory pressure-flow curves.

AIM: To test the hypothesis that the maximal inspiratory muscle (IM) performance, as assessed by the maximal IM pressure-flow relationship, is enhanced with the stretch-shortening cycle (SSC). METHODS: Maximal inspiratory flow-pressure curves were measured in 12 healthy volunteers (35 +/- 6 years) during maximal single efforts through a range of graded resistors (4-, 6-, and 8-mm diameter orifices), against an occluded airway, and with a minimal load (wide-open resistor). Maximal inspiratory efforts were initiated at a volume near residual lung volume (RV). The subjects exhaled to RV using slow (S) or fast (F) manoeuvres. With the S manoeuvre, they exhaled slowly to RV and held the breath at RV for about 4 s prior to maximal inspiration. With the F manoeuvre, they exhaled rapidly to RV and immediately inhaled maximally without a post-expiratory hold; a strategy designed to enhance inspiratory pressure via the SSC. RESULTS: The maximal inspiratory pressure-flow relationship was linear with the S and F manoeuvres (r2 = 0.88 for S and r2 = 0.88 for F manoeuvre, P < 0.0005 in all subjects). With the F manoeuvre, the pressure-flow relationship shifted to the right in a parallel fashion and the calculated maximal power increased by approximately 10% (P < 0.05) over that calculated with the S manoeuvre. CONCLUSION: The maximal inspiratory pressure-flow capacity can be enhanced with SSC manoeuvres in a manner analogous to increases in the force-velocity relationship with SSC reported for skeletal muscles.

Adult↗
PubMed1992

Mechanical constraints on exercise hyperpnea in endurance athletes.

We determined how close highly trained athletes [n = 8; maximal oxygen consumption (VO2max) = 73 +/- 1 ml.kg-1.min-1] came to their mechanical limits for generating expiratory airflow and inspiratory pleural pressure during maximal short-term exercise. Mechanical limits to expiratory flow were assessed at rest by measuring, over a range of lung volumes, the pleural pressures beyond which no further increases in flow rate are observed (Pmaxe). The capacity to generate inspiratory pressure (Pcapi) was also measured at rest over a range of lung volumes and flow rates. During progressive exercise, tidal pleural pressure-volume loops were measured and plotted relative to Pmaxe and Pcapi at the measured end-expiratory lung volume. During maximal exercise, expiratory flow limitation was reached over 27-76% of tidal volume, peak tidal inspiratory pressure reached an average of 89% of Pcapi, and end-inspiratory lung volume averaged 86% of total lung capacity. Mechanical limits to ventilation (VE) were generally reached coincident with the achievement of VO2max; the greater the ventilatory response, the greater was the degree of mechanical limitation. Mean arterial blood gases measured during maximal exercise showed a moderate hyperventilation (arterial PCO2 = 35.8 Torr, alveolar PO2 = 110 Torr), a widened alveolar-to-arterial gas pressure difference (32 Torr), and variable degrees of hypoxemia (arterial PO2 = 78 Torr, range 65-83 Torr). Increasing the stimulus to breathe during maximal exercise by inducing either hypercapnia (end-tidal PCO2 = 65 Torr) or hypoxemia (saturation = 75%) failed to increase VE, inspiratory pressure, or expiratory pressure. We conclude that during maximal exercise, highly trained individuals often reach the mechanical limits of the lung and respiratory muscle for producing alveolar ventilation. This level of ventilation is achieved at a considerable metabolic cost but with a mechanically optimal pattern of breathing and respiratory muscle recruitment and without sacrifice of a significant alveolar hyperventilation.

Adult↗
PubMed2006

High-intensity inspiratory muscle training in COPD.

The aim of the present study was to investigate the effects of an interval-based high-intensity inspiratory muscle training (H-IMT) programme on inspiratory muscle function, exercise capacity, dyspnoea and health-related quality of life (QoL) in subjects with chronic obstructive pulmonary disease. A double-blind randomised controlled trial was performed. Sixteen subjects (11 males, mean forced expiratory volume in one second (FEV(1)) 37.4+/-12.5%) underwent H-IMT performed at the highest tolerable inspiratory threshold load (increasing to 101% of baseline maximum inspiratory pressure). Seventeen subjects (11 males, mean FEV(1 )36.5+/-11.5%) underwent sham inspiratory muscle training (S-IMT) at 10% of maximum inspiratory pressure. Training took place three times a week for 8 weeks and was fully supervised. Pre- and post-training measurements of lung function, maximum inspiratory pressure, maximum threshold pressure, exercise capacity, dyspnoea and QoL (Chronic Respiratory Disease Questionnaire; CRDQ) were obtained. H-IMT increased maximum inspiratory pressure by 29%, maximum threshold pressure by 56%, 6-min walk distance by 27 m, and improved dyspnoea and fatigue (CRDQ) by 1.4 and 0.9 points per item, respectively. These changes were significantly greater than any seen following S-IMT. In conclusion, high-intensity inspiratory muscle training improves inspiratory muscle function in subjects with moderate-to-severe chronic obstructive pulmonary disease, yielding meaningful reductions in dyspnoea and fatigue.

Aged↗
PubMed1975

Regional distribution of a 133Xe labelled gas volume inspired at constant flow rates.

We measured the regional distribution of 480 ml of 133Xe labelled gases inspired from FRC at constant inspiratory flow rates ranging from 0.1 to 6 litres/s. The gases used were air and 20% O2 in helium. At low inspiratory flow rates the gas was preferentially delivered to the dependent region of the lung. At maximal inspiratory flows, all regions of the lung were more evenly ventilated. The rate of redistribution was found to be slower and more even than in previous studies using smaller volumes of inspired gas. Assuming equal and synchronous changes of pleural surface pressure, these results can be reasonably predicted by the mechanical time constant theory applied to a simple two-compartment lung model based on equal regional resistances. Breathing the HeO2 mixture did not significantly change ventilation distribution at any flow rate.

Functional Residual Capacity↗
PubMed1996

Effects of aging and obesity on respiratory muscle phenotype in Zucker rats.

Because obesity results in an increased work of breathing, we tested the hypothesis that the oxidative properties and myosin heavy chain (MHC) isoform profiles in respiratory muscles would differ between lean and obese animals. Furthermore, we postulated that obesity-related changes in respiratory muscles would be independent of age. To test these hypothesis, samples of the costal diaphragm, crural diaphragm, and parasternal intercostal muscles were removed from three age groups (young, adult, and old) of obese and lean Zucker rats. Citrate synthase (CS) activity was measured as a marker of oxidative capacity, and MHC isoforms were identified with gel electrophoresis. Analysis revealed that CS activity was significantly higher in the crural and costal diaphragms and parasternal intercostal of obese animals compared with lean animals (P < 0.05); this obesity-related increased in CS activity was related independent of age. Furthermore, respiratory muscle percent type IIb MHC was lower and percent type I MHC isoforms were higher in obese animals compared with lean animals. These data support the notion that obesity results in a fast-to-slow shift in MHC phenotype and an increase in oxidative capacity in major inspiratory muscles. The shift in MHC isoforms in obese animals is also age related, whereas the obesity-mediated increase in oxidative capacity is relatively independent of age.

Aging↗
PubMed1985

Proximal airway function 8 to 16 years after laryngomalacia: follow-up using flow-volume loop studies.

Twenty children who had endoscopically confirmed laryngomalacia were reviewed at 8 to 16 years of age. All had developed stridor in the first 6 weeks of life; stridor had stopped or largely resolved by age 4 years. Proximal airway function was assessed by expiratory and inspiratory flow volume loops and compared with control values. These children as a group had variable extrathoracic obstruction to inspiratory airflow, as indicated by a significantly low maximal inspiratory flow at 50% of vital capacity and a high mean ratio of maximal expiratory to maximal inspiratory flow at 50% vital capacity. Although limitation to inspiratory airflow was detectable in later childhood, it was not associated with troublesome symptoms. Significant stridor always resolved by 4 years of age, but some children experienced minor stridor under stress in later childhood.

Adolescent↗
PubMed2001

Inspiratory muscle training in patients with cystic fibrosis.

Little information is available about the effects of inspiratory muscle training in patients with cystic fibrosis (CF). In this study the effects of inspiratory-threshold loading in patients with CF on strength and endurance of the inspiratory muscles, pulmonary function, exercise capacity, dyspnoea and fatigue were evaluated. Sixteen patients were assigned to one of two groups using the minimization method: eight patients in the training group and eight patients in the control group. The training was performed using an inspiratory-threshold loading device. Patients were instructed to use the threshold trainer 20 min a day, 5 days a week for 6 weeks. Patients in the training group trained at inspiratory threshold loads up to 40% of maximal static inspiratory pressure (Pimax) and patients in the control group got 'sham' training at a load of 10% of Pimax. No significant differences were found among the two groups in gender, age, weight, height, pulmonary function, exercise capacity, inspiratory-muscle strength and inspiratory-muscle endurance before starting the training programme. Mean (SD) age in the control group was 19 (5.5) years, mean (SD) age in the training group was 17 (5.2) years. Mean FEV1 in both groups was 70% predicted, mean inspiratory-muscle strength in both groups was above 100% predicted. All patients except one, assigned to the training group, completed the programme. After 6 weeks of training, mean inspiratory-muscle endurance (% Pimax) in the control group increased from 50% to 54% (P = 0.197); in the training group mean inspiratory muscle endurance (% Pimax) increased from 49% to 66% (P = 0.003). Statistical analysis showed that the change in inspiratory-muscle endurance (% Pimax) in the training group was significantly higher than in the control group (P = 0.012). After training, in the training group there was a tendency of improvement in Pimax with an increase from 105 to 123% predicted, which just fell short of statistical significance (P = 0.064). After training no significant differences were found in changes from baseline in pulmonary function, exercise capacity, dyspnoea and fatigue. It is concluded that low-intensity inspiratory-threshold loading at 40% of Pimax was sufficient to elicit an increased inspiratory-muscle endurance in patients with CF.

Adolescent↗
PubMed1992

Effect of theophylline in chronic obstructive lung disease.

The bronchodilator, respiratory center and respiratory muscle effects of oral sustained release theophylline are investigated with a placebo controlled double-blind study in 34 patients with chronic obstructive lung disease (COLD). The first 3 days were a theophylline washout period and the patients did not receive theophylline and on the 4th day, serum theophylline concentration was negligible. Initial pulmonary function tests were performed. Twenty-four of the patients took 350 mg oral sustained release theophylline twice a day. Ten of the patients were given placebo. On day 7, serum theophylline concentrations of the study group were in therapeutic doses and the tests were repeated. Bronchodilator effect was assessed by spirometry, flow-volume loops and measuring airway resistance (Raw). Respiratory muscle function was assessed by measuring maximal inspiratory (PImax) and expiratory pressures (PEmax) and the effect on respiratory center was evaluated by minute ventilation, mouth occlusion pressure index and inspiratory duty ratio. Forced vital capacity in one second (p less than 0.001), maximal mid expiratory flow rate (p less than 0.05), maximal expiratory flow at 50 percent of vital capacity (p less than 0.001), maximal inspiratory pressure (p less than 0.01) increased, while airway resistance (p less than 0.05) decreased significantly. Mouth occlusion pressure and minute ventilation mouth occlusion pressure index did not change after theophylline therapy. In placebo group, there was no significant change in airway obstruction assessed by spirometry and flow volume loops or in respiratory muscle function assessed by maximal respiratory pressures. It is therefore, concluded that oral sustained release theophylline has a bronchodilator effect in irreversible chronic obstructive lung disease, increases respiratory muscle function, but in therapeutic doses has no effect on respiratory center.

Administration, Oral↗
PubMed1984

Documentation of upper airway obstruction in unilateral vocal cord paralysis: flow-volume loop studies in 43 subjects.

Upper airway impairment of variable severity occurs in unilateral vocal cord paralysis (UVCP). Among 43 subjects with UVCP all had voice disturbance, 22 had symptoms of airway impairment, and 27 had some disturbance of swallowing. The severity of the airway impairment was evaluated by flow-volume loop spirogram which demonstrated reduced inspiratory flow rates (maximal and midvital capacity). Clinical recovery from paralysis or intracordal Teflon injection was accompanied by improvement in inspiratory flow rates. Airway impairment is most severe in subjects having UVCP due to intrathoracic disorder or intraoperative nerve interruption. Vocal cord position did not correlate with the severity of airway disturbance. The FVC and FEV1 determinations were normal in 33 and 29 cases, respectively, whereas the VI-50 and VE-50/VI-50 were normal in only 11 and 7 instances. This selective restriction of inspiratory flow rates and the abnormally low VE-50/VI-50 ratio was observed regularly. The sensitivity and reproducibility of the flow-volume loop examination support the utilization of this test to evaluate the nature and severity of upper airway impairment; consecutive examinations can be utilized to monitor the clinical course or outcome from treatment.

Adult↗
PubMed1994

Lung volumes during sustained microgravity on Spacelab SLS-1.

Gravity is known to influence the mechanical behavior of the lung and chest wall. However, the effect of sustained microgravity (mu G) on lung volumes has not been reported. Pulmonary function tests were performed by four subjects before, during, and after 9 days of mu G exposure. Ground measurements were made in standing and supine postures. Tests were performed using a bag-in-box-and-flowmeter system and a respiratory mass spectrometer. Measurements included functional residual capacity (FRC), expiratory reserve volume (ERV), residual volume (RV), inspiratory and expiratory vital capacities (IVC and EVC), and tidal volume (VT). Total lung capacity (TLC) was derived from the measured EVC and RV values. With preflight standing values as a comparison, FRC was significantly reduced by 15% (approximately 500 ml) in mu G and 32% in the supine posture. ERV was reduced by 10-20% in mu G and decreased by 64% in the supine posture. RV was significantly reduced by 18% (310 ml) in mu G but did not significantly change in the supine posture compared with standing. IVC and EVC were slightly reduced during the first 24 h of mu G but returned to 1-G standing values within 72 h of mu G exposure. IVC and EVC in the supine posture were significantly reduced by 12% compared with standing. During mu G, VT decreased by 15% (approximately 90 ml), but supine VT was unchanged compared with preflight standing values. TLC decreased by approximately 8% during mu G and in the supine posture compared with preflight standing. The reductions in FRC, ERV, and RV during mu G are probably due to the cranial shift of the diaphragm, an increase in intrathoracic blood volume, and more uniform alveolar expansion.

Adult↗