Maximal static respiratory pressures in the normal elderly

To determine if a relationship exists between maximal static respiratory pressures measured at the mouth and age greater than 55 yr, and if so, whether regression equations can be derived that accurately reflect this, we measured maximal inspiratory (Plmax) and expiratory (PEmax) pressures in 64 normal women and 40 normal men older than 55 yr of age. We found no relationship between PImax and PEmax and age greater than 55 yr (all r squared values less than 0.14). We tested the reproducibility of our measurements of PImax and PEmax in 13 and 12 subjects, respectively, on three separate occasions. Repeated measures analysis showed no significant differences in these measurements. Using the measurements obtained in this large study, we calculated 95% confidence limits for PImax and PEmax values in men and women older than 55 yr of age. The 95% confidence limits for PImax in men were 55 to 161 cm H2O, and 26 to 124 cm H2O in women. The 95% confidence limits for PEmax in men were 90 to 256 cm H2O, and 46 to 184 cm H2O in women. We conclude that given the large interindividual variation, a cross-sectional study such as this or other previous studies may not be able to reveal age-dependent changes unless very large numbers are used, and even then potential for bias exists. However, with the small intraindividual coefficients of variation in repeated measurements of PImax and PEmax, a longitudinal study may provide more pertinent information.     

Maximal static respiratory pressures in children and adolescents

This study was designed to establish reference values of maximal static respiratory pressures in children and adolescents in our community, and compare them with previous studies.Participants were recruited from three schools (randomly chosen from those located in the metropolitan area of the city of Valencia) after appropriate consent. None of the participants had a previous history of pulmonary, cardiac, and/or skeletal abnormalities, and all of them had normal spirometry.Forced spirometry (Spirotrac III, Vitalograph) and maximal inspiratory (P(ImaxRV)) and expiratory (P(EmaxTLC)) pressure values (Sibelmed 163) were obtained by the same investigator, following national guidelines (SEPAR 1990).We studied 392 subjects (185 males, 207 females) whose ages ranged from 8-17 years. The reproducibility of measurements was investigated in a subgroup of 88 participants (randomly selected from the total sample, and stratified for age and gender) by means of the intraclass correlation coefficient (P(EmaxTLC), 0.98; P(ImaxRV), 0.95). P(EmaxTLC) and P(ImaxRV) values were significantly different between males and females (P < 0.0001) and were normally distributed. A stepwise, linear multiple regression model was built in each gender group (male/female) for the prediction of P(ImaxRV) and P(EmaxTLC) values. Independent variables (weight, height, and age) and their potential interactions were forced to enter the model in order to maximize the square of the multiple correlation coefficient of the resultant equation. This model turned out to be applicable (homoscedasticity, independence, and normality requirements) for P(ImaxRV) (in males and females) and for P(EmaxTLC) (in males but not in females). Variables included in the model were age and the product of weight and height. Their predictive power ranged between 0.21-0.51.In conclusion, P(ImaxRV) and P(EmaxTLC) values increase with age from 8 until 17 years. In all age groups, values were higher in males than in females. Weight, height, and age are included in the predictive equations for P(ImaxRV) (in males and females) and P(EmaxTLC) (in males). Their predictive value is similar to that reported by other authors and ranges between 0.21-0.51. This model is not suitable for the prediction of P(EmaxTLC) in females; the observed mean and range should be used instead.     

Laryngeal cancer: long-term follow-up of respiratory functions after laryngectomy

Pulmonary function of 31 heavy smokers with laryngeal cancer was evaluated before and during the 1st year after total (n = 21) and conservative (n = 10) laryngectomy. 2 of them died because of recurrences, 1 for bronchopulmonary complications. Long-lasting hoarseness was the only presenting symptom in all patients. Preoperative lung function data and mucociliary clearance were consistent with a coexisting chronic obstructive lung disease in most subjects and was probably due to smoking. No differences were observed comparing pre- and postoperative data in the 10 conservative laryngectomy patients. On the contrary, the total-laryngectomy patients showed a progressive impairment of bronchial obstruction and bacteriological infection of the trachea during the 1st year after the operation. An impressive increase in mucociliary clearance rates has been observed 2 months after total laryngectomy during the postoperative hypersecretory phase. the obtained data allow us to hypothesize that when clinical conditions of laryngectomized patients in whom local or distant recurrences have been excluded deteriorate, this is related to a progressive bronchial obstruction at any level of the bronchial tree due to descending bacterial infection of the airways. To our knowledge this is the only work demonstrating that total laryngectomized patients need a complete pre- and postoperative evaluation of lung function, airway dynamics, mucociliary function and tracheal bacteriology for long-term prognosis and treatment.     

Measurements of maximum respiratory pressures in polymyositis and dermatomyositis

Measurements of maximum respiratory pressures and routine pulmonary function tests were performed in 8 patients with polymyositis (PM) and 2 patients with dermatomyositis (DM). Serial measurements of routine pulmonary function tests in 8 patients remained unchanged. Maximum respiratory pressures were decreased initially in 7 patients with proximal muscle weakness and clinically active muscle disease and improved with corticosteroid therapy in the 5 patients who were followed serially. In 3 patients with clinically stable disease the maximum respiratory muscle power was normal. Serial measurements of maximum respiratory pressures have been of value in monitoring patients with PM and DM.     

The effect of posture and abdominal binding on respiratory pressures

We examined the effect of posture on the generation of respiratory pressures in 6 highly trained subjects. Transdiaphragmatic pressure was measured at FRC during bilateral percutaneous phrenic nerve stimulation (twitch Pdi) and maximal sniffs (sniff Pdi), with the abdomen bound and unbound. Maximum static inspiratory (PImax) and expiratory (PEmax) mouth pressures were measured with the abdomen unbound. Three postures were examined: seated (Se), semi-supine (30s), and supine (Su). Changes of posture did not significantly alter twitch Pdi. By contrast, sniff Pdi and static mouth pressures were significantly reduced in the Su posture. Abdominal binding significantly increased twitch Pdi only. We conclude that voluntary respiratory manoeuvres requiring activation, recruitment and coordination of different muscle groups are performed better in the Se position. We suggest that posture be standardised for serial comparative measurements of voluntary respiratory pressures in a given subject.     

Effect of intermittent mandatory ventilation on respiratory drive and timing

Seven patients receiving chronic ventilatory support were studied to better define the effects of intermittent mandatory ventilation (IMV) on the control and timing of spontaneous breathing between mandatory breaths. Each of these patients could sustain adequate spontaneous ventilation, as reflected by stable end-tidal carbon dioxide concentration (FETCO2), and arterial oxygen saturation (SO2) during periods of unassisted ventilation of sufficient duration to allow study. Inspiratory time (TI), respiratory cycle duration (Ttot), tidal volume (VT), and tracheal occlusion pressure (P0.1) were measured as IMV rate was progressively reduced. Respiratory timing was unaltered by decreasing IMV frequency; however, VT increased progressively. The P0.1 and mean inspiratory flow rate (VT/TI) also increased with each decrease in IMV rate, whereas FETCO2 and arterial SO2 remained constant. Thus, in these stable but ventilator-dependent patients, IMV did not alter respiratory timing or chemical stimuli, but it did alter respiratory drive as measured by VT/TI and P0.1.     

Effect of respiratory apparatus on timing and depth of breathing in man

The effects on breathing of (1) nose-clips, with and without mouthpieces, (2) tube breathing with incremental dead spaces up to 600 ml, and (3) a Venturi mask with a high air inflow reducing the effective dead space to zero were measured with respiratory inductance plethysmography. The effective dead spaces of the lengths of tubing were 25% smaller than their water-displacement volumes. The principal response to the increase in dead space was an increase in VT without any change in frequency or timing. The increase in VE was 16% greater than the ventilation of the effective dead space. The facemask with a high flow of air did not affect the pattern of breathing. External devices alone (nose-clips, mouthpieces) by themselves brought about a significant increase in VT (+10%, P less than 0.05) and a small drop in frequency, which in the case of a nose-clip alone was large enough to be significant (-15%, P less than 0.05). The increase in DS with the change from nasal to oral breathing may have contributed to the accompanying increase in VT; the fall in frequency with the nose-clip alone might have been caused by stimulation of receptors in the trigeminal area.     

Vagal influences on respiratory mechanics, pressures, and control in rats

In eight spontaneously breathing anesthetized rats airflow, volume, and tracheal pressure were measured. The passive and active mechanical properties of the respiratory system, the shape of the tracheal occlusion pressure wave (Potr), the decay of inspiratory muscle pressure during expiration, and parameters related to the control of breathing were computed both before and after bilateral cervical vagotomy. Pre- and post-vagotomy values of passive elastance, resistance, and time constant were similar. Active mechanics disclosed an increase of elastance and a decrease in resistance and in the time constant after vagotomy. The time course of Potr showed a downward concavity and was not modified by vagotomy in the range of control inspiratory times, whereas the shape of inspiratory muscle pressure decay during expiration was changed. The present data help to explain why after vagotomy the load-compensatory mechanisms are less effective.     

Effect of upper airway negative pressure on respiratory timing

The effects of upper airway negative pressure on respiratory timing and respiratory muscle activity were investigated in 13 urethane-pentobarbital anesthetized adult rabbits. Diaphragm and upper airway muscle EMGs were recorded with fine wire electrodes. The upper airway was converted into a closed system and negative pressure changes were made at will with a syringe attached to a laryngeal cannula. Both inspiratory and expiratory durations (Ti and Te) were prolonged during the negative pressure trials. Maximal prolongation occurred on the first experimental breath for Te and on second breath for Ti. Decreased effects were seen during maintained negative pressures. Peak diaphragm EMG and average slope of diaphragm EMG decreased during these trials. Diaphragmatic apnea (Te greater than or equal to 5 sec) occurred in 15% of trials. In some of these trials apnea lasted as long as the negative pressure stimulus whereas in others spontaneous breathing resumed after a period of apnea. Phasic upper airway muscle activity occurred during diaphragmatic apnea in most of these trials. The superior laryngeal nerve section markedly reduced the effects of negative pressure, indicating that its afferents primarily mediate this response. Our results suggest that upper airway negative pressure acts centrally on both inspiratory and expiratory timing as well as on the motor output of thoracic and upper airway respiratory muscles.     

Laryngeal and respiratory patterns in patients with paradoxical vocal fold motion

The purposes of this study were to determine the differences in spirometric measures obtained from patients with endoscopically-documented paradoxical vocal fold motion (PVFM) and to compare them to a group of normal subjects without endoscopically-documented paradoxical vocal fold motion during non-provocative breathing and following speech. Thirty eight subjects with documented paradoxical vocal fold motion using transnasal flexible laryngoscopy (TFL) and no history of asthma and 21 normal subjects with documented normal breathing patterns and normal findings on endoscopy underwent flow-volume loop studies. Endoscopic judgments of vocal fold motion from three breathing conditions were made by two observers. The results of the endoscopic judgments indicate that paradoxical motion occurs whether breathing through the nose or mouth in the PVFM subjects, mainly after speaking and inhalation. In addition, the spirometry results indicated that the inspiratory measure of FIVC%, FVC% and FIV(0.5)/FIVC were significantly lower in the PVFM group compared to the normal subjects. The data supports the hypothesis that in patients with PVFM, inspiratory spirometric values play a role in identifying patients with PVFM. The finding of vocal fold closure following a speech utterance in the majority of the PVFM subjects but not in the normal control group warrants further investigation.     

Effect of ventilator flow rate on respiratory timing in normal humans

Respiratory rate (RR) increases as a function of ventilator flow rate (V). We wished to determine whether this is due to a decrease in neural inspiratory time (T In), neural expiratory time (TEn), or both. To accomplish this, we ventilated 15 normal subjects in the assist, volume cycled mode. Ventilator flow rate was varied at random, at four breaths with each step, over the flow range from 0.8 (Vmin) to 2.5 (Vmax) L/s. V T was kept constant. The pressure developed by respiratory muscles (Pmus) was calculated with the equation of motion (Pmus = V. R + V. E - Paw, where R = resistance, V = volume, E = elastance, and Paw = airway pressure). Electromyography of the diaphragm (Edi) was also done in five subjects. TIn and TEn were determined from the Pmus or Edi waveform. TIn decreased progressively as a function of V, from 1.44 +/- 0.34 s at Vmin to 0.62 +/- 0.26 s at Vmax (p < 0.00001). Changes in TEn were inconsistent and not significant. TIn/Ttot decreased significantly (0.30 +/- 0.06 at Vmin to 0.18 +/- 0.09 at Vmax; p < 0. 00001). We conclude that TI is highly sensitive to ventilator flow, and that the RR response to V is primarily related to this T In response. Because an increase in V progressively reduces T In/Ttot, and this variable is an important determinant of inspiratory muscle energetics, we further conclude that inspiratory muscle energy expenditure is quite sensitive to V over the range from 0.8 to 2.5 L/s.     

Face mask spirometry and respiratory pressures in normal subjects.

Spirometry and maximal respiratory pressures are pulmonary function parameters commonly used to evaluate respiratory function. Prediction values are available for conventional lung function devices using a standard tube or flanged type of mouthpiece connection. This equipment is not suitable for patients with facial or buccal muscle weakness, because of air leakage around the mouthpiece. A face mask was used for the portable lung function devices used in the neuromuscular department. The aim of this study was to compare the face mask and the conventional mouthpiece for the measurement of spirometry and of respiratory pressures in 22 healthy subjects. Values obtained with the conventional mouthpiece differed significantly from values obtained with the face mask. With the mask, forced vital capacity and forced expiratory volume in one second were 200 mL lower, and maximal expiratory pressure was 3.2 kPa lower than with the mouthpiece. Subsequently, new prediction values for face mask spirometry and maximal respiratory pressures were obtained from 252 other healthy subjects, from which new prediction equations were derived. It was concluded that the face mask connection to the lung function device is a valid alternative, is easy to use and is most useful to monitor changes in patients. This study confirms the importance of appropriate prediction equations, depending on subject-instrument interfaces.     

Effect of posture on arterial pressures, timing of the arterial sounds and pulse wave velocities in the extremities.

We have recorded systolic and diastolic blood pressure, and the intervals between the QRS complex of the electrocardiogram and the Korotkoff arterial sound at systolic and diastolic pressure (QKs and QKd, respectively), at the brachial and posterior malleolar arteries, for normal subjects in the supine, standing, or head-down positions on a tilt table. These data make it possible to calculate an apparent mean pulse wave velocity. Results indicate: (1) when the subject is supine (0 degrees), brachial and posterior malleolar artery blood pressures are virtually identical; (2) upon standing (+90 degrees), both systolic and diastolic pressures in the foot are elevated by a mean of approximately 70 mm Hg, whereas brachial artery systolic pressure is unaffected and brachial diastolic pressure is raised 7 mm of mercury; (3) conversely, in the head-down (feet-up) position (-30 degrees) the blood pressure in the foot was decreased approximately 20 mm of mercury, whereas the brachial arterial pressure is again unaffected; (4) as one changes from the head-down to the supine to the standing positions, the mean QKs interval at the brachial artery was increased by 5 and 15 msec, respectively; (5) conversely, the arrival of the pulse wave in the leg was hastened, with QKd decreasing by 7 and then 18 msec. The effects of QKs were slightly smaller in the brachial artery but considerably larger in the malleolar artery, with a decrease of 16 msec and then 48 msec; (6) mean apparent pulse wave velocity increases from 9.1 to 10.9 to 17.6 m/sec, as one changes from -30 degrees to 0 degrees to +90 degrees.     

Influence of abdomen on respiratory mechanics in supine rabbits.

Previous studies showed that abdominal evisceration has no effect on respiratory system compliance. We hypothesized that this could be related to lung distortion in eviscerated animals. Methods were developed for continuous recording of pleural pressure (Ppl) at various sites over the costal (co) and diaphragmatic lung surface (di) in acutely and chronically instrumented rabbits. We compared deltaPpl,co and deltaPpl,di recorded at mid-lung height during inflations in anesthetized, paralyzed supine rabbits before and after evisceration. Cranial and caudal deltaPpl.co were the same under all conditions. In intact animals, deltaPpl.co and deltaPpl,di were equal at all inflation volumes, whilst in eviscerated animals, deltaPpl,di were smaller than deltaPpl,co, the difference increasing with lung inflation. At any given volume, rib cage circumference (Crc) was smaller after evisceration, but the Crc deltaPpl,co relationship remained unchanged. These results are indicative of non-uniform lung expansion after evisceration and are consistent with model predictions based on cylindrical deformation and lung stress-strain relationship. This deformation should mimic the effect of a reduced lung compliance, keeping respiratory system compliance of eviscerated animals nearly normal. Similar deformation should have occurred also in intact rabbits during strong inspiratory efforts and in the erect posture, because lower Ppl,di than Ppl,co values were observed at the same lung height under these conditions.     

Effects of exercise modality on patterns of ventilation and respiratory timing.

Ventilatory patterns and respiratory timing were measured in 14 subjects during cycling (CYC) and treadmill exercise (TM) at similar leg frequencies (fLEG) to determine if mode of exercise affects patterns of ventilation and respiratory timing. Measurements of breathing frequency (fR), tidal volume (VT), expired ventilation (VE), and inspiratory (TI) and expiratory (TE) time were obtained at fLEG of 50, 70, and 90 rev.min-1 (rpm) for CYC and at similar incremental fLEG (strides.min-1; spm) during TM achieved by increasing belt speed at 0% grade. CYC exercise intensity was approximately 50% VO2,max at all fLEG, whereas VO2 increased progressively with TM. fR increased significantly (P < 0.001) with increasing fLEG of TM (20.5 +/- 4.6, 25.4 +/- 5.8, and 36.3 +/- 7.6 breaths.min-1; mean +/- SD), but during CYC fR changed significantly (P < 0.05) only between fLEG of 70 and 90 rpm (25.0 +/- 5.9 vs 28.5 +/- 6.9 breaths.min-1). Both average breath TI and TE obtained by grouping into incremental ranges of fR decreased significantly (P < 0.05) with increasing fR up to 36 breaths.min-1 and the relationships of TI and TE to fR, TI to TE, and central inspiratory drive (VT/TI) to VE were the same for CYC and TM. Group average fR and fLEG were synchronized during TM, but individual subjects did not exhibit a high degree of entrainment. This study shows respiratory timing patterns to be independent of mode of exercise over the range of fR observed when describing patterns by grouping into incremental ranges of fR.     

From the Cover: Disentangling the role of environmental and human pressures on biological invasions across Europe

The accelerating rates of international trade, travel, and transport in the latter half of the twentieth century have led to the progressive mixing of biota from across the world and the number of species introduced to new regions continues to increase. The importance of biogeographic, climatic, economic, and demographic factors as drivers of this trend is increasingly being realized but as yet there is no consensus regarding their relative importance. Whereas little may be done to mitigate the effects of geography and climate on invasions, a wider range of options may exist to moderate the impacts of economic and demographic drivers. Here we use the most recent data available from Europe to partition between macroecological, economic, and demographic variables the variation in alien species richness of bryophytes, fungi, vascular plants, terrestrial insects, aquatic invertebrates, fish, amphibians, reptiles, birds, and mammals. Only national wealth and human population density were statistically significant predictors in the majority of models when analyzed jointly with climate, geography, and land cover. The economic and demographic variables reflect the intensity of human activities and integrate the effect of factors that directly determine the outcome of invasion such as propagule pressure, pathways of introduction, eutrophication, and the intensity of anthropogenic disturbance. The strong influence of economic and demographic variables on the levels of invasion by alien species demonstrates that future solutions to the problem of biological invasions at a national scale lie in mitigating the negative environmental consequences of human activities that generate wealth and by promoting more sustainable population growth.     

Increased C-reactive protein concentrations in never-treated hypertension: the role of systolic and pulse pressures

OBJECTIVE: To test whether the plasma concentration of C-reactive protein (CRP), a sensitive marker of systemic inflammation, is increased in patients with newly diagnosed, never-treated hypertension and whether blood pressure and its pulsatile component, pulse pressure, are correlated with plasma CRP concentration independently of a consistent number of cardiovascular risk factors. DESIGN: Cross-sectional study in a hospital outpatient hypertension clinic. METHODS: A total of 135 newly diagnosed, never-treated patients with hypertension and 40 healthy matched non-hypertensive controls underwent office and 24-h blood pressure measurement and blood sampling for determination of plasma CRP and serum lipid concentrations. RESULTS: Plasma CRP concentration was greater in hypertensive individuals (1.85 mg/l, interquartile range 0.74-3.64) than in control individuals (1.01 mg/l, interquartile range 0.67-1.88; P = 0.02). In the entire population, CRP had a significant direct association with office systolic blood pressure and pulse pressure, but not with diastolic blood pressure. Among hypertensive patients, plasma CRP was related to 24-h systolic blood pressure (r = 0.28, P < 0.01) and pulse pressure (r = 0.32, P < 0.01), but not to diastolic blood pressure (r = 0.12, P > 0.2). CRP was also directly associated with body mass index (r = 0.25, P < 0.01), serum low-density lipoprotein cholesterol (r = 0.21, P = 0.03) and serum triglycerides (r = 0.21, P = 0.03). In the multivariate analysis, systolic blood pressure and pulse pressure, but not diastolic blood pressure, were significant predictors of plasma CRP concentration when a consistent number of cardiovascular risk factors was controlled for simultaneously. CONCLUSIONS: Systolic blood pressure and pulse pressure, but not diastolic blood pressure, are predictors of plasma C-reactive protein concentrations in patients with newly diagnosed, never-treated hypertension, irrespective of the potential proinflammatory action of traditional cardiovascular risk factors.