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PubMed1995

Effects of body position on the upper airway of patients with obstructive sleep apnea.

Fast-CT scanning was used to study the effects of changes in body position on upper airway (UA) size and shape in 11 awake subjects with obstructive sleep apnea (OSA). Six patients with position (P)-dependent OSA were compared with five patients with nonposition (NP)-dependent OSA. Scans were repeated in the prone (PRN), right side (RS), and supine (SUP) body positions at both functional residual capacity and end-inspiratory tidal volume. Significant group, group by position, and borderline group by respiration effects were detected for minimum but not mean UA dimension data. Significant differences between groups were noted in minimum cross-sectional area and minimum lateral distance but not in minimum anteroposterior distance in the RS and SUP positions. Turning from the PRN to the RS or SUP position tended to decrease UA size in the NP group by decreasing the lateral distance, while the opposite effect was found in the P group. The results indicate that changes in body position during wakefulness affect the lateral but not the anteroposterior dimensions of the UA, and the UA behaves differently in patients with NP and P OSA in response to changes in body position.

Case-Control Studies↗
PubMed1997

Respiratory-related pharyngeal constrictor muscle activity in normal human adults.

Electromyographic activity of the superior, middle, and inferior pharyngeal constrictor (PC) muscles was examined in 10 normal adult humans during wakefulness and sleep. Wire electrodes were inserted close to the midline of the posterior pharyngeal wall at the level of the soft palate (superior PC), tip of the epiglottis (middle PC), and corniculate tubercle (inferior PC). In general, the three PC muscles exhibited similar patterns of activation. The PCs were activated during swallows, repetitive "pa" sounds, changes in head position, and the last portions of slow inspiratory and expiratory vital capacity maneuvers. Respiratory-related PC activity was infrequent during quiet breathing during wakefulness; variable and inconsistent phasic activation in expiration in one or more of the PCs was present in seven of the 10 subjects, particularly after a swallow. Progressive hyperoxic hypercapnia and progressive isocapnic hypoxia were associated with recruitment of phasic PC activity, which was predominantly expiratory; however, variable discharge patterns were observed within a given muscle and a given subject. When phasic PC activity was present, preactivation during late inspiration was frequently observed. PC activity was absent in NREM sleep and exhibited sporadic, nonrespiratory-related bursts of activity during REM sleep. Passively induced hypocapnic hyperventilation in NREM sleep was not associated with PC activation. The results indicate that the PCs have very similar patterns of activation and exhibit phasic expiratory activity during relatively high ventilatory output states in wakefulness.

Adult↗
PubMed2005

Residual paralysis at the time of tracheal extubation.

Respiratory and pharyngeal muscle function are impaired during minimal neuromuscular blockade. Tracheal extubation in the presence of residual paresis may contribute to adverse respiratory events. In this investigation, we assessed the incidence and severity of residual neuromuscular block at the time of tracheal extubation. One-hundred-twenty patients presenting for gynecologic or general surgical procedures were enrolled. Neuromuscular blockade was maintained with rocuronium (visual train-of-four [TOF] count of 2) and all subjects were reversed with neostigmine at a TOF count of 2-4. TOF ratios were quantified using acceleromyography immediately before tracheal extubation, after clinicians had determined that complete neuromuscular recovery had occurred using standard clinical criteria (5-s head lift or hand grip, eye opening on command, acceptable negative inspiratory force or vital capacity breath values) and peripheral nerve stimulation (no evidence of fade with TOF or tetanic stimulation). TOF ratios were measured again on arrival to the postanesthesia care unit. Immediately before tracheal extubation, the mean TOF ratio was 0.67 +/- 0.2; among the 120 patients, 70 (58%) had a TOF ratio <0.7 and 105 (88%) had a TOF ratio <0.9. Significantly fewer patients had TOF ratios <0.7 (9 subjects, 8%) and <0.9 (38 subjects, 32%) in the postanesthesia care unit compared with the operating room (P < 0.001). Our results suggest that complete recovery from neuromuscular blockade is rarely present at the time of tracheal extubation.

Adolescent↗
PubMed1993

Improved pulmonary function and exercise tolerance with inspiratory muscle conditioning in children with cystic fibrosis.

This study documented the effect of inspiratory muscle conditioning in children with cystic fibrosis. Subjects, ages 7 to 14 years, were divided into two groups. The experimental group (n = 10) trained at a high pressure load (> or = 29 cm H2O) and the control group (n = 10) trained at a minimal pressure load (< or = 15 cm H2O), using a threshold loading device. Subjects trained 30 min a day for 10 weeks. Pulmonary function, inspiratory muscle strength, and exercise tolerance were measured at the beginning and end of the training period. Pulmonary function was measured by body plethysmography. Inspiratory muscle strength was determined by standard measures of maximal inspiratory pressure against an occluded airway. Exercise tolerance was measured by the length of time subjects could walk on a treadmill. Findings indicated that the experimental group showed significant increases in inspiratory muscle strength, vital capacity, total lung capacity, and exercise tolerance in comparison to the control group.

Adolescent↗
PubMed1999

Safety and efficacy of 4-aminopyridine in humans with spinal cord injury: a long-term, controlled trial.

STUDY OBJECTIVE: To determine the effects of the long-term administration of 4-aminopyridine (4-AP) on sensorimotor function in humans with long-standing spinal cord injury (SCI). DESIGN: Randomized, open-label, active-treatment control, dosage-blinded study. SETTING: University-affiliated, tertiary-level care, Department of Veterans Affairs Medical Center. PATIENTS: Twenty-one healthy men and women outpatients suffering from traumatic SCI (14 tetraplegic, 7 paraplegic) for 2 years or more. INTERVENTIONS: Dosages of an immediate-release formulation of 4-AP were titrated. At 3 months, 16 subjects were receiving 4-AP 30 mg/day (high dose); 5 subjects were receiving 4-AP 6 mg/day (low dose) and served as an active-treatment control group. MEASUREMENTS AND MAIN RESULTS: Composite motor and sensory scores had statistically significant increases at 3 months. Maximal expiratory pressure, maximal inspiratory pressure, forced vital capacity, and forced expiratory volume in 1 second showed clinically meaningful and/or statistically significant increases among patients receiving 4-AP 30 mg/day. These subjects also had significant decreases in spasticity (modified Ashworth Scale). Serial biochemical profiles and electroencephalographs were unchanged from baseline, and no clinically significant drug toxicity was encountered. CONCLUSIONS: Long-term oral administration of immediate-release 4-AP was associated with improvement in and recovery of sensory and motor function, enhanced pulmonary function, and diminished spasticity in patients with long-standing SCI. 4-Aminopyridine appears to be safe and relatively free from toxicity when administered orally over 3 months. Each patient who received immediate-release 4-AP 30 mg/day showed a response in one or more of the outcome measures.

4-Aminopyridine↗
PubMed2002

Pulmonary function in infants exposed to pethidine.

OBJECTIVE: To investigate the effects of maternal pethidine administration on pulmonary function tests in newborn infants. PATIENTS AND METHOD: The study was carried out in the Department of Obstetrics and Gynecology, Faculty of Medicine Siriraj Hospital. The study group consisted of 20 infants exposed to pethidine within 4 hours prior to delivery. Twenty infants whose mothers received no analgesic drug or regional anesthesia were randomly selected as the controls. Narcotic related respiratory depression was determined by Apgar scores, the need for ventilatory support in the delivery room and abnormal pulmonary function measurements. RESULTS: There was no difference in birth weight and gestational age between the two groups of infants. Pethidine was given to mothers at a dose of 72.5 +/- 7.6 mg/kg with a mean drug-delivery interval of 152 +/- 61 minutes. One infant in each group had a 1-minute Apgar score less than 7, but there was no statistical difference in the mean Apgar score between the two groups. None of the infants whose mothers received pethidine required ventilatory support, but oxygen was provided to eight infants who were apparently cyanosed at birth. Pulmonary function measurements were performed at the age of 7.4 +/- 2.3 hours in the controls and 6.0 +/- 2.5 hours in the study group. There was no significant difference in respiratory rate, tidal volume, inspiratory time, functional residual capacity, compliance and resistance between the two groups of infants. CONCLUSION: Severe narcotic related respiratory depression was uncommon in this study. In the first 12 hours of life, there was no significant difference in pulmonary function of the infants exposed to pethidine. It is quite safe to allow the baby to room-in with the mother if respiratory depression is not presented at birth.

Analgesics, Opioid↗
PubMed1992

Breathlessness predicts perceived exertion in young women with mild asthma.

We examined ratings of breathlessness (BRE) as a predictor of perceived exertion (RPE) during incremental cycling at power outputs of 50, 75, and 100 W. Young females (21 yr +/- 1.9) diagnosed with mild asthma (N = 25) were compared with females having normal lung function (N = 25) matched for age, VO2peak, trait anxiety, activity history (7-d recall), and BMI (kg.m-2). Relative oxygen consumption (%VO2peak), blood lactate concentration, VE.VO2(-1), and state anxiety were statistically controlled in hierarchical multiple linear regression analyses. For each group, %VO2peak explained 60% of the variance in RPE across power outputs (P less than 0.001); R2 was unchanged (P greater than 0.10) with the addition of blood lactate, VE.VO2(-1), and state anxiety. Absolute RPE and BRE did not differ between groups at any power output, but partial standardized (beta) and unstandardized (b) regression coefficients and increases in R2 showed that BRE had a greater effect (P less than 0.01) on RPE for asthmatics [adjusted R2 increased to 0.89; (beta) = 0.75; (b) = 0.79 +/- 0.06] than for controls [adjusted R2 increased to 0.74; (beta) = 0.52; (b) = 0.51 +/- 0.09]. The standard error of the prediction was 0.79 for asthmatics and 1.16 for controls. The prediction of RPE by BRE was not moderated by variation in forced expiratory volume for 1 s (FEV1), forced vital capacity (FVC) or peak inspiratory flow (VI). Physiological responses were similar for the groups, but blood lactate was higher in asthmatics at rest, at each power output, and at VO2peak.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2006

[Function of the external respiration in teenage and adult women of different age groups].

The purpose of the study was to determine the function of external breath in teenage and adult women ranging from 15 to 79 years old. 492 people from the age groups of 15-19, 20-29, 30-39, 40-49, 50-59 and 60-79 years were examined by the help of a spirograf supplied with a microprocessor of SPM-01 -"R-D". The results were processed statistically by the F- and t-criterion method. The parameters of the function of external breath (V, VC, FVC tests), except inspiratory reserve volume and capacity breath, proved to be changing in age dynamics (p < 0.01).

Adolescent↗
PubMed1991

[Aerosol deposit sample in aspecific bronchial provocation test: a nuclear medicine study for quantification].

A method of standardization of inhalation bronchial provocation tests is induced. The distribution of radioactivity of in- and exhaled 99mTc human albumin (Venticoll) enables an exact calculation of intrabronchial aerosol deposition. The investigations were carried out at twelve normal test persons by using the device of bronchial provocation tests of PARI. Linearity exists between nebulized aerosol quantity in the bag and bronchial aerosol deposition. The intrabronchial aerosol deposition is calculated about 100 mg after emptying the ten liter-bag. Slowly inspiratory maneuvers of vital capacity produce a precision of the inhaled aerosol of about 15 percent.

Aerosols↗
PubMed1996

Maximal inspiratory pressure in elite soccer players.

The respiratory muscle strength of elite athletes has been assessed only for some competitive sports and different conclusions have been reported. The aim of this study was to evaluate the inspiratory muscle strength in a group of professional soccer players in comparison with a group of sedentary subjects. Maximal Inspiratory Pressure (PImax) was measured both at Functional Residual Capacity (FRC) and at Residual Volume (RV) in 130 subjects: 27 of these were elite soccer players (all males, aged 22 +/- 3 years) and 103 were normal sedentary subjects (77 males and 26 females, aged 44 +/- 19 years). Predictive linear models were produced by a stepwise regression analysis in the whole sample of subjects. Both PImaxFRC and PImaxRV models included female gender and ageing as negative predictors, and Body Mass Index (BMI) as positive predictor of the inspiratory pressures. The model predicting PImaxFRC was slightly more accurate than the model predicting PImaxRV (r-squared: 0.38 vs 0.36, respectively). After adjustment for the variables entered in these models, PImaxFRC and PImaxRV were respectively 1.54 KPa and 1.08 KPa higher in soccer players than in sedentary subjects but this result was statistically significant (p < 0.02) only for PImaxFRC. We conclude that the inspiratory muscle strength is increased in soccer players and PImax measured at FRC seems more sensitive in order to discriminate between subjects with different level of physical activity.

Adolescent↗
PubMed1976

[Closing volume and ventilatory distribution disturbances (author's transl)].

Ventilatory disturbances are induced by airway closure associated with an increase of the venous admixture from alveoli with a low ventilation-perfusion-ratio. Closing volume was measured by single breath nitrogen washout curves and correlated with ventilatory disturbances derived from multiple breath nitrogen washout curves and an inspiratory gas distribution index (IDI). There was present a close correlation between the closing volume in relation to the functional residual capacity and the IDI. With rising closing volume in relation to functional residual capacity a deterioration of the inspiratory gas distribution with increasing venous admixture was observed.

Adolescent↗
PubMed1984

Pulmonary function in adolescents with mild idiopathic scoliosis.

Spirometric indices, lung volumes, maximum voluntary ventilation, and maximum inspiratory and expiratory pressures were measured in 44 adolescents with mild idiopathic scoliosis (spinal curvature less than 30 degrees). All were symptom free, but six (13.6%) showed a restrictive defect with forced vital capacity less than 80% of predicted. In 12 subjects (27.3%) maximum voluntary ventilation was reduced to less than 80% of predicted normal. Forced vital capacity was significantly correlated with maximum inspiratory pressure and with maximum expiratory pressure, measures of respiratory muscle strength, but was not related to the degree of thoracic curvature. When maximum inspiratory pressure and forced vital capacity were corrected for differences in body size these variables remained positively correlated, most significantly in the girls. These data indicate that ventilatory function may be impaired in mild, idiopathic scoliosis and that the force developed by the respiratory muscles is a more important determinant of this impairment than the radiologically determined degree of spinal curvature.

Adolescent↗
PubMed2003

Peak inspiratory flows in children with cystic fibrosis.

OBJECTIVE: To show that in children with moderately severe cystic fibrosis lung disease: (i). inspiratory flow may be reduced; and (ii). peak inspiratory flow may be predicted from height, expiratory flow analysis or body mass index. METHODS: All children attending the Royal Children's Hospital, Melbourne, between May and July, 2001 who had cystic fibrosis, were aged > 5 years, were able to perform spirometry reproducibly and who had a forced expiratory volume in 1 s < 60% predicted were prospectively enrolled. Height, weight, peak inspiratory flow, forced expiratory volume in 1 s and forced vital capacity were recorded. Linear regression analysis was performed. RESULTS: The age range was 9.4-19.9 years. Sixteen boys and 11 girls were studied. All children had a peak inspiratory flow > 0.5 L/s. There was a significant relationship between peak inspiratory flow and forced vital capacity (R2 = 0.50) especially in boys (R2 = 0.65). In boys, peak inspiratory flow was significantly related to forced expiratory volume in 1 s (R2 = 0.47). There was no relationship between peak inspiratory flow and predicted values of expiratory flow, age, height, weight or body mass index. Logistic regression was used to predict the probability that peak inspiratory flow was < 2.0 L/s for a given forced vital capacity. If the forced vital capacity is > 2.5 L, peak inspiratory flow is likely to be > 2.0 L/s. CONCLUSIONS: In children with significant cystic fibrosis lung disease, peak inspiratory flow is likely to be > 0.5 L/s, which is required to activate dry powder inhalers. If the forced vital capacity is < 2.5 L, the peak inspiratory flow may be < 2.0 L/s, and a metered dose inhaler and spacer should be considered. Further studies that investigate the relationship between expiratory flow and peak inspiratory flow against an internal resistance are needed.

Child↗
PubMed1996

Adaptive strategies of respiratory muscles in response to endurance exercise.

The purpose of this review is to discuss the adaptive strategies of mammalian respiratory muscles in response to whole-body endurance exercise training. It is now clear that endurance training results in small (i.e., 20-30%) but significant increases in mitochondrial enzyme activity and the activities of key antioxidant enzymes (i.e., superoxide dismutase and glutathione peroxidase) within the rodent diaphragm. Interestingly, the magnitude of this training-induced increase in costal diaphragmatic oxidative and antioxidant enzyme activity is relatively independent of the exercise duration and intensity. Although the crural diaphragm of rodents is also capable of increasing its oxidative and antioxidant capacity in response to endurance training, high-to moderate-intensity exercise of long duration is required to promote these changes. Endurance training also increases the oxidative capacity of other key rodent inspiratory muscles, such as the parasternal intercostals and external intercostals. Furthermore, endurance training results in small (approximately 10%) increased in the oxidative capacity of key abdominal (expiratory) muscles. Whether the improvement in oxidative capacity of respiratory muscles is of significant magnitude to result in improvement in respiratory muscle performance remains an unanswered question.

Adaptation, Physiological↗
PubMed1995

Inspiratory muscle strength is a determinant of maximum oxygen consumption in chronic heart failure.

OBJECTIVE: To investigate the significance of respiratory muscle weakness in chronic heart failure and its relation both to maximum oxygen consumption during cardiopulmonary exercise testing and to skeletal muscle (quadriceps) strength. SUBJECTS: Seven healthy men aged 54.9 (SEM 4.3) years and 20 men with chronic heart failure aged 61.4 (1.6) years (P = 0.20) with radionuclide left ventricular ejection fraction of 25.4 (3.0)%. METHODS: Mouth pressures during maximum static inspiratory effort (PImax) at functional residual capacity (FRC) and residual volume (RV) were measured in all subjects and taken as indices of inspiratory muscle strength. Similarly, mouth pressures during maximum static expiratory effort (PEmax) at FRC and total lung capacity (TLC) were taken as indices of expiratory muscle strength. Cardiopulmonary exercise testing was performed in all subjects. All controls and 15 heart failure patients also had their right quadriceps muscle strength measured. RESULTS: There was respiratory muscle weakness in heart failure patients, with reduction of PImax at FRC (59.7) (6.3) v 85.6 (9.6) cm H2O, P = 0.045), PEmax at FRC (94.8 (6.2) v 134.6 (9.1) cm H2O, P = 0.004), and PEmax at TLC (121.7 (8.5) v 160.7 (13) cm H2O, P = 0.028). PImax at RV was also reduced but this did not reach statistical significance (77.3 (6.6) v 89.3 (13) cm H2O, P = 0.44). There was also significant weakness of the right quadriceps muscle (308.5 (22) v 446.2 (28) N, P = 0.001). PImax at both FRC and RV correlated with maximum oxygen consumption (r = 0.59, P = 0.006, and r = 0.45, P = 0.048 respectively) but not PEmax. There was, however, no significant correlation between PImax and right quadriceps strength. CONCLUSIONS: Respiratory muscle weakness is seen in chronic heart failure. The results suggest that inspiratory muscles are important in determining maximum oxygen consumption and exercise tolerance in these patients. The lack of correlation between respiratory and right quadriceps muscle strength further suggests that the magnitude and time course of respiratory and locomotor muscle weakness may differ in individual patients. Treatment aimed at improving the function of the involved muscle groups may alleviate symptoms.

Adult↗
PubMed1996

Ventilation with constant versus decelerating inspiratory flow in experimentally induced acute respiratory failure.

BACKGROUND: Recognition of the potential for ventilator-associated lung injury has renewed the debate on the importance of the inspiratory flow pattern. The aim of this study was to determine whether a ventilatory pattern with decelerating inspiratory flow, with the major part of the tidal volume delivered early, would increase functional residual capacity at unchanged (or even reduced) inspiratory airway pressures and improve gas exchange at different positive end-expiratory pressure levels. METHODS: Surfactant depletion was induced by repeated bronchoalveolar lavage in 13 anesthetized piglets. Decelerating and constant inspiratory flow ventilation was applied at positive end-expiratory pressure levels of 22, 17, 13, 9, and 4 cm H(2)O. Tidal volume, inspiration-to-expiration ratio, and ventilatory frequency were kept constant. Airway pressures, gas exchange, functional residual capacity (using a wash-in/washout method with sulfurhexafluoride), central hemodynamics, and extravascular lung water (using the thermo-dye-indicator dilution technique) were measured. RESULTS: Decelerating inspiratory flow yielded a lower arterial carbon dioxide tension compared to constant flow, that is, it improved alveolar ventilation. There were no differences between the flow patterns regarding end-inspiratory occlusion airway pressure, end-inspiratory lung volume, static compliance, or arterial oxygen tension. No differences were seen in hemodynamics and oxygen delivery. CONCLUSIONS: The decelerating inspiratory flow pattern increased carbon dioxide elimination, without any reduction of inspiratory airway pressure or apparent improvement in arterial oxygen tension. It remains to be established whether these differences are sufficiently pronounced to justify therapeutic consideration.

Acute Disease↗
PubMed1996

Inspiratory muscle endurance in patients with chronic heart failure.

OBJECTIVE: To assess the significance of changes in respiratory muscle endurance in relation to respiratory and limb muscle strength in patients with mild to moderate chronic heart failure using a threshold loading technique. SUBJECTS: 20 patients with chronic heart failure (17 male) aged 63.8 (SD 7.4) years and 10 healthy men aged 63.1 (5.6) years. Heart failure severity was New York Heart Association (NYHA) grade II (n = 11) and NYHA grade III/IV (n = 9). METHODS: Respiratory muscle strength was measured from mouth pressures during maximum inspiratory effort (MIP) at functional residual capacity (FRC) and limb muscle strength was measured using a hand grip dynamometer. Inspiratory muscle endurance was measured using a threshold loading technique. The total endurance duration, the maximum threshold pressure achieved (P-Max), and the inspiratory load (% ratio of P-Max/MIP) were recorded in all subjects. RESULTS: Inspiratory muscles were weaker in patients with heart failure than in the controls [MIP 53.6 (16.5) v 70.9 (20.2) cm H2O, P < 0.05]. Hand grip strength was similar in both subject groups [31.6 (SD) v 36.1 (15.9) dynes]. Total endurance duration was significantly reduced in the patient group [494 (223) v 996 (267) s, P < 0.01], as was the maximal threshold pressure achieved [P-Max 18.5 (6.4) v 30.7 (6.6) cm H2O, P < 0.01]. When expressed as a percentage of MIP, P-Max was also lower in the patients [35.2 (11.8) v 44.8 (11.4)%, P < 0.05]. There was no significant correlation between any measure of endurance and limb muscle strength. CONCLUSIONS: Respiratory muscle endurance is reduced in patients with chronic heart failure. These changes probably reflect a generalised skeletal myopathy and provide further evidence of respiratory muscle dysfunction in patients with this disease. Respiratory muscle endurance needs now to be related to symptoms and the effects of treatment and respiratory muscle training should also be explored.

Chronic Disease↗
PubMed1993

Effect of positive expiratory pressure on breathing pattern in healthy subjects.

The purpose of this study was to register breathing patterns, in healthy subjects, during breathing with a positive expiratory pressure. Integrated electromyographic (IEMG) activity of the following muscles was assessed: scalene muscle, parasternal muscle and abdominal muscles, using surface electrodes. Inspiration time, expiration time, total breathing cycle time, tidal volume and breathing frequency were measured using a water-sealed spirometer. Functional residual capacity was measured using a body plethysmograph. Oxygen uptake and carbon dioxide output were measured using an automatized ergometry set-up. All measurements were performed during undisturbed breathing and during breathing with positive expiratory pressures of 5 and 15 cmH2O. Phasic activity, but not tonic activity, of the scalene muscles and the abdominal muscles increased significantly during breathing with the expiratory pressures. No significant change was observed in phasic or tonic activity of the parasternal muscle. Mean (SD) tidal volume increased significantly from 0.8(0.2) l during undisturbed breathing to 1.1(0.3) l and 1.5(0.7) l during breathing with the expiratory pressures of 5 cmH2O and of 15 cmH2O, respectively. Respiration times, breathing frequency, oxygen uptake, carbon dioxide output and functional residual capacity remained unchanged. It can be concluded that, in healthy subjects, positive expiratory pressure increases tidal volume by activity of both expiratory and inspiratory muscles, while functional residual capacity remains unchanged. The changes appeared to be pressure dependent.

Adult↗