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 181 records · Page 10Linked to original sources
PubMedDate not supplied

Respiratory mechanics after 180 days space mission (EUROMIR'95).

The present study reports data on respiratory function of lung and chest wall following the 180 days long European - Russian EuroMir '95 space mission. Data reported refer to two subjects studied before the mission, on day 9 and 175 in flight and on days 1, 10, 12, 27 and 120 after return. In-flight vital capacity (VC) and expiratory reserve volume (ERV) were similar to those in supine posture, namely approximately 5% and approximately 30% less than in sitting posture. On day 1 after return, VC was reduced by approximately 30% in both postures. This reflected a decrease in ERV (approximately 0.5 L) and in IC (inspiratory capacity, approximately 1.7 L) that could be attributed to a marked weakening of the respiratory muscles. Regain of normal preflight values barely occurred 120 days after return. Post-flight pressure-volume curves of the lung, chest wall and total respiratory system are equal to preflight ones. The pressure-volume curve of the lung in supine posture is displaced to the right relative to sitting posture and shows a lower compliance. As far as the lung in-flight condition resembles that occurring in supine posture, this implies a lower compliance, a greater amount of blood in the pulmonary microvascular bed, a more homogeneous lung perfusion and therefore a greater microvascular filtration rate towards lung interstitium.

Adult↗
PubMed1986

Involuntary breath-stacking. An alternative method for vital capacity estimation in poorly cooperative subjects.

Performed correctly, the vital capacity (VC) is a useful indicator of the mechanical properties of the thorax and of neuromuscular performance. Unfortunately, its use is often limited by impaired comprehension, altered mental status, or inability to sustain forceful effort. Our purpose was to develop a measure of VC independent of subject cooperation. We estimated the subcomponents of VC (inspiratory capacity (IC) and expiratory reserve volume (ERV], using one-way valving of an external circuit to enforce cumulation or elimination of the tidal breaths stimulated by endogenous ventilatory drive. When configured to measure IC, gas entered the chest incrementally, until tidal effort became insufficient to overcome thoracic recoil. Valve rearrangement permitted analogous estimation of ERV. We tested the validity of this method in cooperative but naive subjects by comparing the VC measured in standard fashion (VCC) to the breath-stacked estimate (VCS). Thirty normal subjects and 20 ambulatory patients with diverse causes for respiratory impairment were studied. Peak and mean values of VCS correlated strongly with the corresponding values of VCC (r greater than or equal to 0.91). The coefficient of variation for sequential V VCS determinations (approximately equal to 5.5%) was comparable to that observed for VCC (approximately equal to 3.5%) in both subject groups, indicating acceptable reproducibility of the involuntary VCS measurement. VCS maneuvers were quickly completed and well tolerated. Involuntary breath-stacking may provide a useful estimate of VC in clinical settings where conventional methodology cannot be confidently applied.

Adult↗
PubMedDate not supplied

Lung function in children and adolescents with idiopathic interstitial pulmonary fibrosis.

Lung function of 65 patients who had idiopathic interstitial pulmonary fibrosis (IIPF) that had been treated with prednisone was evaluated by tests of ventilatory function, lung mechanics, and gas exchange at rest and during exercise. Ages on initial investigation ranged from 5 to 20 years. In 35 of 65 patients the studies were repeated an average of four times over a period of 1 to 9 years. Results of the first testing were as follows: vital capacity (VC)-significantly reduced in all patients; inspiratory capacity (IC)-significantly reduced in all patients; total lung capacity (TLC)-reduced in 91%; functional residual capacity (FRC)-reduced in 31%; residual volume (RV)-reduced in 6%; elastic recoil of the lungs (Pstl)-significantly increased in 97% at 100% TLC, significantly increased in 52% at 90% TLC, reduced in 68% at 60% TLC; 7) static compliance (Cst)-reduced in 83%; 8) dynamic compliance (Cdyn)-reduced in 88%; 9) specific airway conductance at FRC level (Gaw/TGVex)-significantly increased in 50%; 10) maximum expiratory flow rates at 60% TLC (Vmax 60% TLC, in TLC/s)-significantly reduced in 33%; 11) upstream airway conductance (Gus 60% TLC, in TLC/s/cm H2O)-reduced in 32%; 12) diffusing capacity of the lungs for carbon monoxide (DLco) related to body-surface area-abnormal in 58% (when corrected for lung size, i.e., DLco/TLC, abnormal in only 8%); 13) PaO2 at rest and after 6 minutes submaximal exercise-reduced in 25% and 63%, respectively. Changes in lung function that occurred with growth were assessed in terms of percentages of predicted values. Results showed that the VC and IC remained significantly reduced. An actual reduction of TLC, FRC, RV, breathing frequency, DLCO, and Pstl at 100% and 90% TLC was observed. Increases were seen in Pstl at 60% TLC, Gaw/TGVex, Vmax, and Cst. Indices of lung elasticity suggested that regions of fibrosis and emphysema had become present. Smaller patients were also noted to have stiffer lungs.

Adolescent↗
PubMed1994

Three-dimensional reconstruction of the in vivo human diaphragm shape at different lung volumes.

The ability of the diaphragm to generate pressures at different lung volumes (VLs) in humans may be determined by the following factors: 1) its in vivo three-dimensional shape, radius of curvature, and tension according to Laplace law; 2) the relative degree to which it is apposed to the rib cage (i.e., zone of apposition) and lungs (i.e., diaphragm dome); and 3) its length-force properties. To gain more insight into these factors we have reconstructed from nuclear magnetic images the three-dimensional shape of the diaphragm of four normal subjects under supine relaxed conditions at four different VLs: residual volume, functional residual capacity, functional residual capacity plus one-half of the inspiratory capacity, and total lung capacity. Under our experimental conditions the shape of the diaphragm changes substantially in the anteroposterior plane but not in the coronal one. Multivariate regression analysis indicates that the zone of apposition is dependent on both diaphragm shortening and lower rib cage widening with lung inflation, although much more on the first of these two factors. Because of the changes in anteroposterior shape and expansion of the insertional origin at the costal margin with lung inflation, the data therefore suggest that the diaphragm may be more accurately modeled by a "widening piston" (Petroll's model) than a simple "piston in a cylinder" model. A significant portion of the muscular surface is lung apposed, suggesting that diaphragmatic force has radial vectors in the dome and vectors along the body axis in the zone of apposition. The muscular surface area of the diaphragm decreased linearly by approximately 41% with VL from residual volume to total lung capacity. Diaphragmatic fibers may shorten under physiological conditions more than any other skeletal muscle. The large changes in fiber length combined with limited shape changes with lung inflation suggest that the length-twitch force properties of the diaphragm may be the most important factor for the pressure-generating function of this respiratory muscle in response to bilateral phrenic shocks at different VLs.

Diaphragm↗
PubMed1996

Zone of apposition in the passive diaphragm of the dog.

We determined the regional area of the diaphragmatic zone of apposition (ZAP) as well as the regional craniocaudal extent of the ZAP (ZAPht) of the passive diaphragm in six paralyzed anesthetized beagle dogs (8-12 kg) at residual lung volume (RV), functional residual capacity (FRC), FRC + 0.25 and FRC + 0.5 inspiratory capacity, and total lung capacity (TLC) in prone and supine postures. To identify the caudal boundary of the ZAP, 17 lead markers (1 mm) were sutured to the abdominal side of the costal and crural diaphragms around the diaphragm insertion on the chest wall. Two weeks later, the dogs' caudal thoraces were scanned by the use of the dynamic spatial reconstructor (DSR), a prototype fast volumetric X-ray computer tomographic scanner, developed at the Mayo Clinic. The three-dimensional spatial coordinates of the markers were identified (+/- 1.4 mm), and the cranial boundary of the ZAP was determined from 30-40 1.4-mm-thick sagittal and coronal slices in each DSR image. We interpolated the DSR data to find the position of the cranial and caudal boundaries of the ZAP every 5 degrees around the thorax and computed the distribution of regional variation of area of the ZAP and ZAPht as well as the total area of ZAP. The ZAPht and area of ZAP increased as lung volume decreased and were largest near the lateral extremes of the rib cage. We measured the surface area of the rib cage cephaled to the ZAP (AL) in both postures in another six beagle dogs (12-16 kg) of similar stature, scanned previously in the DSR. We estimated the entire rib cage surface area (Arc = AZAP + AL). The AZAP as a percentage of Arc increased more than threefold as lung volume decreased from TLC to RV, from approximately 9 to 29% of Arc.

Anesthesia, General↗
PubMed2003

The pattern and timing of breathing during incremental exercise: a normative study.

Clinical evaluation of the pattern and timing of breathing during submaximal exercise can be valuable for the identification of the mechanical ventilatory consequences of different disease processes and for assessing the efficacy of certain interventions. Sedentary individuals (60 male/60 female, aged 20-80 yrs) were randomly selected from >8,000 subjects and submitted to ramp incremental cycle ergometry. Tidal volume (VT)/resting inspiratory capacity, respiratory frequency, total respiratory time (Ttot), inspiratory time (TI), expiratory time (TE), duty cycle (TI/Ttot) and mean inspiratory flow (VT/TI) were analysed at selected submaximal ventilatory intensities. Senescence and female sex were associated with a more tachypnoeic breathing pattern during isoventilation. The decline in Ttot was proportional to the TI and TE reductions, i.e. TI/Ttot was remarkably constant across age strata, independent of sex. The pattern, but not timing, of breathing was also influenced by weight and height; a set of demographically and anthropometrically based prediction equations are therefore presented. These data provide a frame of reference for assessing the normality of some clinically useful indices of the pattern and timing of breathing during incremental cycle ergometry in sedentary males and females aged 20-80 yrs.

Adult↗
PubMed1998

Effect of salbutamol on dynamic hyperinflation in chronic obstructive pulmonary disease patients.

Expiratory flow limitation (EFL), which promotes dynamic hyperinflation and increased work of breathing, often occurs in chronic obstructive pulmonary disease (COPD). The purpose of this study was to assess the effect of bronchodilators on EFL and end-expiratory lung volume in patients with moderate-to-severe COPD. EFL was assessed by applying negative expiratory pressure (NEP) at the mouth during tidal expiration. EFL was present when expiratory flow did not increase or increased only in the early phase of expiration with NEP. In 18 patients (age 65+/-2 yrs; forced expiratory volume in one second (FEV1)=45+/-4% predicted) pulmonary function tests and a series of NEP (-3.5 cmH2O) test breaths were performed at rest in a sitting position before and 20 min after inhalation of 400 microg of salbutamol. EFL was detected in 11 patients and persisted after salbutamol in all of these flow-limited (FL) patients. After bronchodilator administration FL patients exhibited a significant decrease in functional residual capacity (FRC) associated with an increase in inspiratory capacity (IC). In contrast, no changes in FRC and IC were observed in the seven non flow-limited (NFL) patients after administration of salbutamol. Except for one NFL patient, the other 17 patients (six NFL and 11 FL) had no reversibility of their bronchial obstruction (delta FEV1 <10% pred). In conclusion, patients with chronic obstructive pulmonary disease and expiratory flow limitation, even if nonresponders in terms of forced expiratory volume in one second, may benefit from bronchodilators because they can breathe, still in a flow-limited manner, at a lower lung volume.

Administration, Inhalation↗
PubMed1975

The effect of tubocurarine on indirectly elicited train-of-four muscle response and respiratory measurements in humans.

The effect of tubocurarine on the respiratory function of conscious, non-medicated volunteers was correlated with the degree of neuromuscular blockade measured with the train-of-four technique (the evoked response of the adductor pollicis brevis muscle to trains of four supramaximal ulnar nerve stimuli at 2 Hz, repeated once every 10 sec). Respiratory frequency, tidal volume, vital capacity, inspiratory force and peak expiratory flow rate were measured, (a) before administration of tubocurarine, (b) when the ratio of the amplitude of the fourth response to the amplitude of the first response of the train-of-four reached 60%, and (c) during recovery of the ratio until the control (100%) value was reached. Respiratory frequency, tidal volume and peak expiratory flow rate were not altered. Vital capacity and inspiratory force were both reduced significantly at the 60% level and the former also at the 70% level when compared with the control. The magnitude of change in all variables is of minor clinical importance, however, since the lowest measured values are well above acceptable minimum limits required for adequate respiratory function.

Dose-Response Relationship, Drug↗
PubMed1999

Spirometric correlates of improvement in exercise performance after anticholinergic therapy in chronic obstructive pulmonary disease.

We wished to determine which resting spirometric parameters best reflect improvements in exercise tolerance and exertional dyspnea in response to acute high-dose anticholinergic therapy in advanced COPD. We studied 29 patients with stable COPD (FEV(1) = 40 +/- 2% predicted [%pred]; mean +/- SEM) and moderate to severe chronic dyspnea. In a double-blind placebo-controlled cross-over study, patients performed spirometry and symptom-limited constant-load cycle exercise before and 1 h after receiving 500 micrograms of nebulized ipratropium bromide (IB) or saline placebo. There were no significant changes in spirometry, exercise endurance, or exertional dyspnea after receiving placebo. In response to IB (n = 58): FEV(1), FVC, and inspiratory capacity (IC) increased by 7 +/- 1%pred, 10 +/- 1%pred, and 14 +/- 2%pred, respectively (p < 0.001), with no change in the FEV(1)/FVC ratio. After receiving IB, exercise endurance time (Tlim) increased by 32 +/- 9% (p < 0.001) and slopes of Borg dyspnea ratings over time decreased by 11 +/- 6% (p < 0.05). Percent change (%Delta) in Tlim correlated best with DeltaIC%pred (p = 0.020) and change in inspiratory reserve volume (DeltaTLC%pred) (p = 0.014), but not with DeltaFVC%pred, DeltaPEFR%pred, or DeltaFEV(1)%pred. Change in Borg dyspnea ratings at isotime near end exercise also correlated with DeltaIC%pred (p = 0.04), but not with any other resting parameter. Changes in spirometric measurements are generally poor predictors of clinical improvement in response to bronchodilators in COPD. Of the available parameters, increased IC, which is an index of reduced resting lung hyperinflation, best reflected the improvements in exercise endurance and dyspnea after IB. IC should be used in conjunction with FEV(1) when evaluating therapeutic responses in COPD.

Administration, Inhalation↗
PubMed1999

The feasibility of high dose iodine 131 treatment as an alternative to surgery in patients with a very large goiter: effect on thyroid function and size and pulmonary function.

Some patients with very large goiters (>150 mL) are not candidates for surgery. We evaluated the feasibility of high dose 131I in such patients. Twenty-three patients (2 men and 21 women; median age, 67 yr; range, 42-86 yr) with very large goiter (8 toxic) were treated with calculated high dose 131I [median, 2281 megabecquerels (61.6 mCi); range, 988-4620 megabecquerels (26.7-124.9 mCi)]. During the 12-month observation period, goiter reduction and tracheal anatomy were monitored by magnetic resonance imaging, and the respiratory capacity was monitored by pulmonary function tests. Five patients (22%) developed hypothyroidism. Thyroid volumes were at baseline, after 1 week, and after 1 yr [mean +/- SEM, 311 +/- 28, 314 +/- 26 (P = NS), and 215 +/- 26 (P < 0.01) mL]. The relative changes 1 week after therapy ranged from -14.1% to 15.3%. After 1 yr the mean size was reduced by 33.9% (range, 13.5-61.4%). Only the initial goiter size showed a significant negative correlation to the percent reduction. The smallest cross-sectional area of the trachea decreased 9.2% within 1 week after treatment, but eventually emerged with a 17.9% larger area [mean +/- SEM, 84.3 +/- 4.8, 75.5 +/- 5.1 (P < 0.01), and 98.2 +/- 6.0 (P < 0.01) mm2]. The inspiratory parameter, FIF50%, improved after an initial insignificant decline [baseline therapy, after 1 week, after 3 months, and after 1 yr (mean +/- SEM), 2.37 +/- 0.24, 2.20 +/- 0.21 (P = NS), 2.51 +/- 0.23 (P = NS), and 2.76 +/- 0.25 (P = 0.01) L/s]. FIF50% correlated significantly with the smallest cross-sectional tracheal area (baseline, 1 week, and 1 yr: r = 0.74; P < 0.001, r = 0.63; P < 0.005, and r = 0.46; P < 0.05). Changes in tracheal anatomy did not correlate with changes in either lung dynamics or goiter size. In conclusion, very large goiters can be reduced by a third, on the average, with high dose 131I therapy without any initial clinically significant tracheal compression. Tracheal cross-sectional area as well as pulmonary inspiratory capacity improve. No serious adverse effects are seen.

Adult↗
PubMed1997

[Effect of methylphenidatum on inspiratory muscles function in patients with chronic obstructive pulmonary disease and its mechanism].

To have a better understanding of the effect of methylphenidatum on inspiratory muscles function, we studied the respiratory force parameters of 70 patients with chronic obstructive pulmonary disease by intravenous infusion methylphenidatum in a randomized controlled clinical trial. The indices of respiratory force parameter included maximal inspiratory mouth pressure (MIP), maximal midinspiratory flow (MMIF), forced inspiratory capacity (FIC), maximal works of inspiration (Wimax) and airway occlusion pressure (P0.1), etc. Aminophylline and Nikethamidi were chosen as controls. The results showed that MIP, MMIF, FIC, Wimax, P0.1 and minute ventilation (Vr) were significantly increased after administration of methylphenidatum and aminophylline. There were no significant differences in MIP, MMIF, FIC and Wimax after administration of Nikethamidi, but P0.1 was significantly increased and the increase was higher than that after administration of methylphenidatum and aminophylline groups. We conclude that methylphenidatum can significantly improve the function of inspiratory muscles as aminophylline can do.

Female↗
PubMed1991

Lung volumes during low-intensity steady-state cycling.

The use of inspiratory capacity (IC) to estimate end-expiratory lung volume (EELV) during exercise has been questioned because of the assumption of constant total lung capacity (TLC). To investigate lung volumes during low-intensity steady-state cycling, we measured EELV by the open-circuit N2 washout method (MR-1, currently Sensormedics 2100) in eight healthy men while at rest and during unloaded and 60-W cycling. TLC was calculated by adding EELV and IC. Measurement variation of TLC was 142 ml at rest, 121 ml during unloaded cycling, and 158 ml during 60-W cycling. TLC did not differ significantly among the three conditions studied. EELV decreased during unloaded (P less than 0.002) and 60-W cycling (P less than 0.001) compared with rest. End-inspiratory lung volume increased only during 60-W cycling (P = 0.03). The decrease in EELV accounted for 100% of the increase in tidal volume during unloaded cycling. Although minute ventilation was similar in the subjects during unloaded cycling, we noted that breathing patterns varied among the subjects. The increase in respiratory frequency was negatively correlated to the change in tidal volume (R2 = 0.54, P = 0.038) and to the change in end-inspiratory lung volume (R2 = 0.68, P = 0.012). We conclude that TLC does not differ significantly during low-intensity steady-state cycling and that use of IC to estimate changes in EELV is appropriate.

Adult↗
PubMed2003

Acute effects of hyperoxia on dyspnea in hypoxemia patients with chronic airway obstruction at rest.

STUDY OBJECTIVES: Supplemental oxygen is used in hypoxemic patients with chronic airways obstruction (CAO) because it reduces pulmonary artery pressure and prolongs life. The purpose of this study was to assess at rest the effects of 30% oxygen inhalation on dyspnea, breathing pattern, neuromuscular inspiratory drive based on measurement of mouth occlusion pressure (P(0.1)), and dynamic hyperinflation (DH), as reflected by changes in inspiratory capacity (IC). METHODS: Ten patients with stable CAO receiving long-term oxygen were studied at rest, before and after 5, 15, and 25 min of oxygen administration. Severity of dyspnea was rated using the visual analog scale (VAS). Breathing pattern parameters, P(0.1), IC, and tidal expiratory flow limitation (EFL), were measured sequentially. RESULTS: Eight patients exhibited EFL under baseline condition. During 30% oxygen breathing, the VAS score significantly decreased, associated with a concurrent increase of IC (11%). There was also a significant reduction of minute ventilation and tidal volume (11% and 12%, respectively), which was due to a significant decrease of mean inspiratory flow. Although not significantly, P(0.1) decreased by 13%. Finally, two patients reverted from EFL to no EFL. CONCLUSION: Patients with CAO receiving long-term oxygen may benefit from hyperoxic breathing at rest, since it decreases the ventilation and the degree of DH, with concurrent improvement of dyspnea sensation.

Aged↗
PubMed1976

Relationships between eupnoeic pattern of breathing and ventilatory control in man: I. Response to airways occlusion during active lung inflation.

The apnoeic response following interruption of the air flow at different levels of the inspiratory capacity (deltaVL) was studied in conscious children and adults. Changes in mouth pressure were used to measured the duration of the apnoe. The total duration of the interrupted breath (T1) was compared to mean value of the ventilatory period of the five preceding breaths (T0). A monoexponential regression could be fitted to the relationship between T1/T0 ratio and change in lung volume (deltaVL) measured at the onset of interruption: T1/T0=k-exp (S-deltaVL), S begin the sensitivity of the response to lung inflation. When T1/T0=1, the intrathoracic lung volume was called threshold volume (VTh.L.). The parameters S and VTh.L. were used for characterization of the individual importance of the Breuer-Hering inspiratory-inhibitory reflex (B.H. reflex). The high reproducibility of the T1/T0 vs. deltaVL relationship in many subjects showed the light influence of voluntary control on apnoea's duration. In each subject, S and VTh.L. were compared with ventilatory variables measured during eupnoea. A fast pattern of breathing (i.e. small inspired volume and short inspiratory duration) was associated with high value of S and low VTh.L. Moreover VTh.L. was near the tidal volume range in subjects where the B.H. reflex was the more potent. Thus, vagal afferents relating to this reflex could modulate the eupnoeic pattern of some subjects.

Adolescent↗
PubMed2005

Effect of increased diaphragm activation on diaphragm power spectrum center frequency.

Increased transdiaphragmatic pressure, reduced muscle blood flow, and increased duty cycle have all been associated with a reduction in the center frequency (CFdi) of the diaphragm's electrical activity (EAdi). However, the specific influence of diaphragm activation on CFdi is unknown. We evaluated whether increased diaphragm activation would result in a greater decline in the CFdi when pressure-time product (PTPdi) was kept constant. Five healthy subjects performed periods of intermittent quasi-static diaphragmatic contractions with a fixed duty cycle. In separate runs, subjects targeted transdiaphragmatic pressures (Pdi) by performing end-inspiratory holds with the glottis open and expulsive maneuvers at end-expiratory lung volume (EELV). Diaphragm activation and pressures were measured with an electrode array and balloons mounted on an esophago-gastric catheter, respectively. The EAdi, which was 25+/-8%(S.D.) of maximum at EELV, increased to 61+/-8% (P<0.001) when an identical Pdi (averaging 31+/-13 cmH2O) was generated at a higher lung volume (77% of inspiratory capacity). The latter was associated with a 17% greater decline in CFdi (P=0.012). In order to reproduce at EELV, the decrease in CFdi observed at the increased lung volume, a two-fold increase in PTPdi was required. We conclude that CFdi responds specifically to increased diaphragm activation when pressure-time product remains constant.

Action Potentials↗
PubMed2002

Does radioiodine therapy have an equal effect on substernal and cervical goiter volumes? Evaluation by magnetic resonance imaging.

Most often thyroidectomy is recommended in patients with large goiters. However, high-dose (131)I therapy may be used in case of contraindications to surgery. Large goiters are often partially located in the mediastinum. The aim of this study was to evaluate the impact of (131)I therapy on the cervical and the substernal goiter volume, separately. Fourteen patients (median age, 69 years; range, 52-86 years) with a large multinodular goiter (three hyperthyroid) and with a substernal extension greater than 15 mL were included. T1-weighted magnetic resonance (MR) estimates of the thyroid volume in the cervical and substernal compartments were obtained before and 1 year after high-dose (131)I therapy. The total goiter volumes ranged from 182 to 685 mL. The median substernal volume was 66 mL (fraction of total volume, 17.6%; range, 8.0%-78.9%). One year after treatment, the median substernal goiter volume was reduced by 29.2% (range, -6.1%-59.4%, mean: 26.1% +/- 6.0%), and the cervical goiter volume by 30.3% (range, 6.0%-75.4%, mean, 35.6 +/- 5.6%) compared to baseline values; p = 0.25 for difference in a regional effect. The volume reduction was unrelated to initial substernal goiter size. Likewise, deterioration of the inspiratory capacity did not correlate with the magnitude of the substernal goiter extension. In conclusion, high-dose (131)I therapy seems as effective in reducing the substernal as the cervical goiter volume. However, because the overall effect is modest, this therapy should primarily be considered for the patient with a high surgical risk.

Aged↗
PubMed1984

Respiratory muscle weakness in uremic patients under continuous ambulatory peritoneal dialysis.

The increasingly frequent use of continuous ambulatory peritoneal dialysis (CAPD) as substitutive therapy in terminal renal failure has induced the investigation of the advantages and disadvantages of this therapeutic modality. The effects of CAPD on pulmonary function are one of the aspects currently under study. Based on previous data suggesting the existence of extrapulmonary ventilatory restriction in uremic patients under CAPD, we have studied in these patients the respiratory muscle function as expressed in the maximal inspiratory pressure (MIP) and assessed the impact of the infusion of 2 liters of dialysis fluid into the peritoneal cavity on both MIP and the pulmonary volumes. Uremic patients evidenced significantly lower MIP values as compared with healthy controls. The filling of the peritoneal cavity induced, both in the supine and in the sitting position, a restrictive effect and an increase in the inspiratory capacity. We conclude that uremic patients under CAPD evidence a respiratory muscle dysfunction of as yet unclear cause. Our findings further suggest that the infusion of 2 liters of dialysis fluid into the peritoneal cavity induces not only a restrictive effect, but also an increase in the strength of the respiratory muscles, the latter effect being probably due to increased diaphragmatic contractility.

Adult↗
PubMed1985

Effects of breathing pattern and oxygen upon the alveolar arterial oxygen pressure difference in lung disease.

It was suggested by analysis of theoretical lung models that low V/Q units are unstable and can be converted into shunt by breathing O2. We tested this theory in 21 subjects with various lung diseases (mostly chronic obstructive pulmonary disease) by having them breathe O2. We also increased the tidal volumes in these patients to see whether this maneuver could prevent the development of shunt. We found that mean P(A-a)O2 increased from 30 +/- 2.8 (mean +/- SEM) Torr breathing room air to 135 +/- 20.7 Torr breathing O2 for 10 min (p less than 0.0001), to 124 +/- 20.4 Torr breathing O2 for 20 min (p less than 0.0001), and to 125 +/- 19.0 Torr breathing oxygen with inspiratory capacity breaths (p less than 0.0001). The corresponding shunt increased from about 2.8% of the cardiac output to 7.9 +/- 1.01, 7.3 +/- 1.03 and 7.3 +/- 0.98%, respectively. We conclude that: (1) breathing pure oxygen can convert low V/Q units to shunt, hence measurement of P(A-a)O2 and shunt by oxygen technique will overestimate the actual values; (2) 10 min of oxygen breathing will cause complete atelectasis of low V/Q units, and (3) increased tidal volume does not prevent absorptive atelectasis.

Adult↗