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 1,441 records · Page 80Linked to original sources
PubMed2003

Limitations of sniff nasal pressure in patients with severe neuromuscular weakness.

BACKGROUND: Inspiratory muscle strength in patients with neuromuscular disorders can be assessed using sniff inspiratory nasal pressure (Pn(sn)) and maximum inspiratory mouth pressure (PI(max)). However, the relative merits of Pn(sn) against PI(max) are not known in patients with severe neuromuscular disease. OBJECTIVE: To investigate whether severity of disease modifies the relation between Pn(sn) and PI(max). METHODS: Vital capacity (VC), Pn(sn), and PI(max) were measured in 258 patients with neuromuscular disorders. RESULTS: Data were analysed from 241 patients, 17 being unable to perform PI(max) or Pn(sn) manoeuvres. The correlation between Pn(sn) and PI(max) was +0.94 (p<0.0001), with a mean (SD) difference between Pn(sn) and PI(max) of -4.8 (21.2) cm H(2)O (the limits of agreement were 37.6 and -47.2 cm H(2)O). VC (% predicted) was positively correlated with Pn(sn)/PI(max) (r = +0.86; p<0.0001), with a lower Pn(sn)/PI(max) value in patients with a VC <40% of predicted than in those with a VC >40% (0.80 (0.35) v 1.04 (0.41); p<0.0001). CONCLUSIONS: PI(max) is greater than Pn(sn) in patients with a severe restrictive ventilatory defect caused by neuromuscular disease. Pn(sn) may not accurately reflect inspiratory muscle strength in such patients and it is thus advisable to use both tests.

Adult↗
PubMed1996

Lung volumes and respiratory muscle strength in adult patients with childhood- or adult-onset growth hormone deficiency: effect of 12 months' growth hormone replacement therapy.

We have described impairment of the respiratory function in adult patients with childhood-onset growth hormone (GH) deficiency. The aim of the present study was to evaluate lung volumes and respiratory muscle strength in patients diagnosed as GH deficient before and after 6 and 12 months of recombinant GH treatment. Ten adults diagnosed as GH deficient in childhood, ten adults diagnosed as GH deficient in adulthood and ten healthy subjects entered the study. For each subject, evaluation of respiratory function followed the same standard approach, consisting of respiratory muscle strength assessment, record of flow-volume curves, measurement of static lung volumes and lung diffusing capacity. Childhood-onset GH-deficient patients had a significant reduction of maximal inspiratory (p < 0.01) and maximal expiratory (p < 0.05) mouth pressures. Total lung capacity, vital capacity and functional residual capacity were significantly reduced compared to healthy subjects (p < 0.05). Conversely, residual volume and diffusing lung capacity did not show any significant change. No significant change of the ratio between the percentage forced expiratory volume in 1 s and the forced vital capacity was observed. The decrease of respiratory mouth pressures was not correlated to the decrease of lung volumes. Adult-onset GH-deficient patients had only a significant reduction of maximal expiratory pressure compared to healthy subjects (p < 0.05). After 6 months of treatment no significant differences in any of the evaluated parameters were found. After 12 months of treatment patients with childhood-onset GH deficiency show a significant improvement of lung volumes (p < 0.01) and maximal respiratory mouth pressures (p < 0.005), whereas adult-onset GH-deficient patients show a significant improvement of maximal expiratory pressure (p < 0.05). In conclusion, the results of this study showed that adult patients affected with childhood-onset GH deficiency suffer from an impairment of the ventilatory function due to a reduction of lung volumes and a decrease of respiratory pressures probably due to a reduction of respiratory muscle strength. This impairment was reversed after 12 months of treatment with recombinant GH. Conversely, adult-onset GH-deficient patients had only an impairment of the maximal expiratory pressure, probably due to respiratory muscle weakness re-established after 12 months of GH therapy.

Adult↗
PubMed1997

Clinical implications of maximal respiratory pressure determinations for individuals with Duchenne muscular dystrophy.

OBJECTIVE: To analyze the relationship between disease progression, pulmonary volumes, respiratory muscle strength (maximum inspiratory [MIP] and expiratory [MEP] pressure), and arterial blood gases for patients with Duchenne muscular dystrophy (DMD). DESIGN: An inception cohort study of pulmonary volumes, MIPs, and MEPs, correlated with age and PaCO2 levels and with each other using linear and nonlinear regression analyses. SETTING: Outpatient clinic. PATIENTS: Fifty-two consecutive DMD patients who presented for regular evaluations at a regional DMD center. RESULTS: Maximum expiratory pressures were 47.7% +/- 10.9% of normal in the 167- to 14-year-old patients and decreased linearly thereafter (MEP% = -2.7 x age +73.8; p < .001). Declines in MEP also correlated linearly with expiratory reserve volume (p < .001) and inversely with residual volume (p < .001). By contrast, MIP was 66.3% +/- 19.0% in the 357- to 14-year-old patients and then declined to 30.2% +/- 19.5% after age 14. No linear relationships were found with age but declines did correlate linearly with inspiratory reserve volume (p < .001) and total lung capacity (p < .001). PaCO2 elevations correlated best with decreases in MIP (p < .0001) and appeared when MIP was below 30cmH2O. CONCLUSIONS: Lung volume changes in DMD patients correlate with respiratory muscle weakness, and although inspiratory muscle dysfunction plays a key role in the development of chronic ventilatory insufficiency, reductions in expiratory muscle strength are the first signs of dysfunction and lead to the first episodes of respiratory failure.

Adolescent↗
PubMed1985

Influence of vagal activity on the neonatal ventilatory response to hypoxemia.

The sustained increase in ventilation (V1) that occurs during acute hypoxemia in adults is not characteristic of the neonate as V1 falls to or below baseline values soon after onset of the hypoxic stimulus. Associated with this decline in V1 is a decrease in tidal volume, lung compliance, inspiratory duration, and an increase in functional residual capacity and respiratory frequency. We hypothesized that hypoxemia induced small airway constriction and pulmonary time constant inequalities resulting in a frequency dependent fall in lung compliance and tidal volume and retention of lung volume. In seven newborn subhuman primates, responses to acute hypoxemia were measured prior to and after administration of atropine methyl bromide to prevent vagally mediated narrowing of peripheral airways. The increase in frequency and fall in inspiratory duration characteristic of the ventilatory decline during hypoxemia was eliminated by the drug but functional residual capacity and lung compliance were unaffected. Also, the initial rise in V1 was blunted or blocked in all subjects. Bilateral vagotomy caused V1 to fall significantly requiring oxygen supplementation but responses to hypoxemia were still biphasic in nature. These findings suggest that cholinergically mediated mechanisms in the airways do not alter effective lung distensibility related to respiratory rate. Acetylcholine may be important at the peripheral chemosensor since cholinergic blockade eliminated the initial ventilatory increase.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1998

Rehabilitation of patients admitted to a respiratory intensive care unit.

OBJECTIVE: Pulmonary rehabilitation has been shown to be of benefit to clinically stable patients with chronic obstructive pulmonary disease (COPD). This study examined the effect of pulmonary rehabilitation on some physiologic variables in COPD patients recovering from an episode of acute respiratory failure. DESIGN: A prospective, randomized study. SETTING: A respiratory intensive care unit (RICU). PATIENTS: Eighty COPD patients recovering from an episode of acute respiratory failure were randomized in a 3:1 fashion to receive stepwise pulmonary rehabilitation (group A, n=60 patients) or standard medical therapy (group B, n=20 patients). MAIN OUTCOME MEASURES: Improvements in exercise tolerance, sense of breathlessness, respiratory muscle function, and pulmonary function test values were measured, respectively, by exercise capacity (6-minute walking distance [6MWD]), dyspnea score (Visual Analog Scale [VAS]), maximal inspiratory pressure (MIP), forced expiratory volume in 1 second (FEV1), and forced vital capacity (FVC). INTERVENTIONS: Group A received pulmonary rehabilitation that consisted of passive mobilization (step I), early deambulation (step II), respiratory and lower skeletal muscle training (step III), and if the patients were able, complete lower extremity training on a treadmill (step IV). Group B received standard medical therapy plus a basic deambulation program. RESULTS: Sixty-one of 80 patients were mechanically ventilated at admission to the unit and most of them were bedridden. Twelve of the 60 group A patients and 4 of the 20 group B patients died during their RICU stay, and 9 patients required invasive mechanical ventilation at home after their discharge. The total length of RICU stay was 38+/-14 days for patients in group A versus 33.2+/-11 days for those in group B. Most patients from both groups regained the ability to walk, either unaided or aided. At discharge, 6 MWD results were significantly improved (p < .001) in Group A only. MIP improved in Group A only (p < .05), while VAS scores improved in both groups, but the improvement was more marked in group A (p < .001) than in group B (p < .05). CONCLUSIONS: COPD patients who were admitted to a RICU in critical condition after an episode of acute respiratory failure and who, in most cases, required mechanical ventilation benefited from comprehensive early pulmonary rehabilitation, compared with patients who received standard medical therapy and progressive ambulation.

Aged↗
PubMed1996

Obstructive and restrictive pulmonary dysfunctions in Parkinson's disease.

Pulmonary dysfunction was investigated in fifty-eight Parkinson's patients. Clinical disability was assessed by the Unified Parkinson's Disease Rating Scale. Pulmonary dysfunction was studied by spirometry with flow-volume loops, body plethysmography with lung volumes computation and maximal inspiratory and expiratory static mouth pressures. Forced vital capacity (FVC), forced expiratory volume in 1 min (FEV1), FEV1/FVC% and arterial PO2 and PCO2 were significantly below normal values. Residual volume (RV) and total rows were above normal values. Thirty-six had upper airway obstruction as judged by inspiratory flow peaks (PIF) < 3 l/s and FEV1/PEF (expiratory flow peak) > 8.5 l/min and MEF50/MIF50 > 1. Eighteen patients had a central (FEV1 < 80% and FEV1/FVC% < 80% of normal values) or peripheral (maximal expiratory flow between 75% and 25% of FVC and maximal expiratory flow after expiration of 50% below 70% of normal values) obstructive pattern. Sixteen patients had a restrictive dysfunction as judged by a total lung capacity < 85% or FVC < 80% with FEV1/FVC% > 80%. Sixteen patients had air trapping (RV > 120% and RV/TLC > 40%) and seven patients had lung insufflation (TLC > 120%). Rigidity, Rx signs of cervical arthrosis and limitations for passive movement of neck were higher in patients with central or peripheral airway obstruction. Bradykinesia and Rx signs of dorsal arthrosis was higher in patients with upper airway obstruction. Restrictive dysfunction was not related to tremor, rigidity or bradykinesia. The present data support the hypothesis that Parkinson patients present a high risk for pneumologic disturbances. These pulmonary dysfunctions are induced by the simultaneous action of a group of factors including the degree of bradykinesia or rigidity and the musculoskeletal limitations of vertebral column probably induced by chronic anomalous posture.

Humans↗
PubMed1986

Effect of abdominal binders on breathing in tetraplegic patients.

We studied the effect on breathing of a conventional and a newly designed abdominal binder in seven patients with complete tetraplegia. The indices of respiratory ability used were the transdiaphragmatic pressure on maximal sniff (sniff Pdi), the maximum static inspiratory mouth pressure (PImax), and the vital capacity (VC). These were measured in patients with and without binders, in the supine position, raised up to 70 degrees on a tilt table, and seated upright. When patients were raised from the supine to the 70 degrees tilt and to the seated posture, sniff Pdi and VC decreased. Both binders improved VC in the seated position and at 70 degrees tilt, and sniff Pdi at 70 degrees tilt. The new binder was as effective as but no better than the conventional binder. PImax was too variable to be a valuable index of inspiratory power. These findings support the view that abdominal binders assist breathing in tetraplegic patients who are seated or raised to near vertical positions.

Abdominal Muscles↗
PubMed1999

Emerging concepts in the evaluation of ventilatory limitation during exercise: the exercise tidal flow-volume loop.

Traditionally, ventilatory limitation (constraint) during exercise has been determined by measuring the ventilatory reserve or how close the minute ventilation (VE) achieved during exercise (i.e., ventilatory demand) approaches the maximal voluntary ventilation (MVV) or some estimate of the MVV (i.e., ventilatory capacity). More recently, it has become clear that rarely is the MVV breathing pattern adopted during exercise and that the VE/MVV relationship tells little about the specific reason(s) for ventilatory constraint. Although it is not a new concept, by measuring the tidal exercise flow-volume (FV) loops (extFVLs) obtained during exercise and plotting them according to a measured end-expiratory lung volume (EELV) within the maximal FV envelope (MFVL), more specific information is provided on the sources (and degree) of ventilatory constraint. This includes the extent of expiratory flow limitation, inspiratory flow reserve, alterations in the regulation of EELV (dynamic hyperinflation), end-inspiratory lung volume relative to total lung capacity (or tidal volume/inspiratory capacity), and a proposed estimate of ventilatory capacity based on the shape of the MFVL and the breathing pattern adopted during exercise. By assessing these types of changes, the degree of ventilatory constraint can be quantified and a more thorough interpretation of the cardiopulmonary exercise response is possible. This review will focus on the potential role of plotting the extFVL within the MFVL for determination of ventilatory constraint during exercise in the clinical setting. Important physiologic concepts, measurements, and limitations obtained from this type of analysis will be defined and discussed.

Exercise↗
PubMed1987

Response to resistive loading in the newborn piglet.

The diaphragmatic force generation and electromyographic response to long-term (1 h) inspiratory resistive loading was examined in the newborn piglet during the 3rd postnatal wk of life. Minute ventilation decreased to approximately 50% of baseline level within 5 min of imposition of a severe resistive load and remained at this level for the duration of loading. The decrease in ventilation was secondary to a fall in tidal volume at a constant frequency. There was a significant increase in central nervous system output to the diaphragm as manifested by integrated diaphragmatic electromyogram. Progressive augmentation of this index of central drive continued throughout the period of loading. Functional residual capacity fell significantly by 60 min of inspiratory resistive loading. This strategy should allow greater force generation by placing the diaphragm at a more optimal length-tension relationship. However, the force generating capability of the diaphragm was compromised as assessed by force-frequency curve analysis. These results suggest that the diaphragm of the neonatal piglet fatigues during prolonged inspiratory resistive loading.

Airway Resistance↗
PubMed1995

[Non-invasive intermittent mechanical ventilation: usefulness in treatment of chronic severe heart failure].

BACKGROUND: The higher respiratory work and less inspiratory muscle strength of patients with cardiac failure may contribute to decrease their functional capacity. AIM: To assess the effects of non invasive intermittent mechanical ventilation on clinical parameters, peripheral perfusion, cardiac and inspiratory muscle function. PATIENTS AND METHODS: Patients with chronic cardiac failure, functional capacity III-IV were subjected to 6 sessions of nasal non invasive intermittent ventilation during 4 hours or to simulated ventilation (controls). RESULTS: Fifteen ventilated patients and six controls completed the protocol. Ventilated patients improved the Mahler transition score for dyspnea by 4 +/- 1.6 points. They also improved their aerobic capacity, increasing the exercise duration from 10.9 +/- 4 to 12.7 +/- 5 min and their maximal oxygen consumption from 14.6 +/- 4 to 16.4 +/- 5.7 ml/kg/min. These patients also decreased their O2 and CO2 ventilatory equivalents. Maximal inspiratory pressure increased from 67.9 +/- 23.6 to 80.19 +/- 21.4 cm H2O, sustained maximal inspiratory pressure increased from 101.4 +/- 48 to 133 +/- 53 cm H2O and maximal endurance increased from 132 +/- 52 to 162 +/- 58 g in ventilated patients. None of these variables was modified in control patients. No changes were observed in renal function, blood volume, arterial gases, spirometry or plasma catecholamine levels in any group. CONCLUSIONS: Intermittent nasal ventilation or other measures to improve inspiratory muscle function may be beneficial for patients with severe cardiac failure.

Adult↗
PubMed1991

[Maximal ventilatory pressure through the mouth in adults: normal values and explanatory variables].

Mouth pressure measured during maximal inspiratory or expiratory efforts depends on the force exerted by ventilatory muscles. Normal values and anthropometric factors accounting for maximal inspiratory and expiratory pressures (MIP, MEP) are not fully agreed upon to date. We measured MIP and MEP in 253 normal subjects (135 females and 118 males, age 15-59 years) using a digital transducer (163 Sibelmed). All subjects had normal forced vital capacity (FVC) and one second forced expiratory volume (FEV1). Sex, age, height and weight were recorded for all subjects and were entered as independent variables in computation of linear multiple regressions with MEP or MIP the dependent variables. MEP and MIP were greater in males than in females (p less than 0.01) with MIP lower than MEP in both sexes (p less than 0.01). In both males and females, FVC and FEV1 depend on age and height (p less than 0.01). In the entire group, we found a correlation of MIP in females and MEP in males with age (p less than 0.01) and of both MIP and MEP in females with weight (p less than 0.01). However, in subjects aged 20-59 years, there was no significant dependence of MIP and MEP on age, and when the weight of subjects was normal (n = 170), MIP and MEP were independent of weight. We conclude that in adults aged 20-59 years and with normal weight, maximal ventilatory pressures depend solely on sex. In this subgroup mean (+/- SD) values of MEP and MIP were 111 +/- 25 cmH2O and 79 +/- 19 cmH2O respectively in females and 192 +/- 42 cmH2O and 117 +/- 25 cmH2O in males.

Adolescent↗
PubMed1986

Effect of varying inspiratory and expiratory times during high-frequency jet ventilation.

Although high-frequency jet ventilation may reduce barotrauma, the optimal ventilator settings at which complications are minimized have not been determined. To develop ventilator strategies applicable to the human infant, we studied six New Zealand rabbits before and after saline lung lavage. Changes in functional residual capacity (delta FRC) and airway pressure gradient (peak inspiratory pressure minus positive end-expiratory pressure) were measured while inspiratory time (TI) and expiratory time (TE) were varied. Frequencies of 120, 240, and 480 cycles per minute and inspiratory to expiratory ratios of 1:1, 1:3, 1:5, and 1:9 resulted in TI that varied from 12 to 250 msec, and TE from 62 to 450 msec. Analysis of variance demonstrated that as TI was shortened, a significantly higher airway pressure gradient was necessary to maintain a constant tidal volume. As TE was shortened, air trapping, as determined from both inadvertent positive end-expiratory pressure and delta FRC, significantly increased. Lung lavage increased the airway pressure gradient at each TI, but decreased air trapping at each TE. At no time did entrainment contribute to the delivered tidal volume. We conclude that a relatively narrow range of TI and TE may be necessary for optimal use of high-frequency jet ventilation to reduce airway pressures and minimize the risk of air trapping.

Animals↗
PubMed1998

Assessment of lung volumes using helical CT at inspiration and expiration: comparison with pulmonary function tests.

OBJECTIVE: This study was designed to determine lung volumes using inspiratory and expiratory helical CT with two-dimensional (2D) and three-dimensional (3D) postprocessing and to compare the accuracy of those measurements with pulmonary function test results. SUBJECTS AND METHODS: Seventy-two patients with suspected pulmonary disease underwent unenhanced helical CT (slice thickness, 8 mm; pitch, 2; increment, 8 mm) at deep inspiration and expiration. Lung volumes were determined using either a 2D approach (semiautomatic segmentation; thresholds, -1024 and -200 H) or a 3D technique (double-threshold seeded volumes of interest; thresholds, -1024 H [lower] and -900, -500, 400, -300, or -200 H [upper]). Pulmonary function tests were available for correlation in all cases. RESULTS: Using inspiratory helical CT, we underestimated total lung capacity by 12%, which had a good correlation (r = .89) with static lung volumes. Volume revealed by expiratory helical CT was equivalent to intrathoracic gas volume, which also exhibited a good correlation (r = .88). However, using expiratory helical CT, we overestimated residual volume by 850 ml with a rather good correlation (r = .77). An emphysema index revealed moderate correlation with the relative forced expiratory volume in 1 sec (inspiration, r = -.66; expiration, r = -.54), whereas the expired volume showed a moderate correlation with the absolute forced expiratory volume in 1 sec (r = .65). The 2D approach showed lower absolute volumes than the 3D technique (mean, 3.6%; r = .99). In the 3D technique, lower upper thresholds led to reduced volumes (170 ml/100 H). CONCLUSION: Inspiratory and expiratory helical CT show high correlation with static lung volumes. The 3D technique (-1024 to -200 H) is recommended for absolute estimation of lung volumes.

Female↗
PubMed1995

Structure of the latissimus dorsi muscle and respiratory function.

The aim of this study was to evaluate whether respiratory function influences the structure of the latissimus dorsi muscle (LD). Twelve patients (58 +/- 10 yr) undergoing thoracotomy were studied. Lung and respiratory muscle function were evaluated before surgery. Patients showed a forced expired volume in 1 s (FEV1) of 67 +/- 16% of the reference value, an FEV1-forced vital capacity ratio of 69 +/- 9%, a maximal inspiratory pressure of 101 +/- 21% of the reference value, and a tension-time index of the diaphragm (TTdi) of 0.04 +/- 0.02. When patients were exposed to 8% CO2 breathing, TTdi increased to 0.06 +/- 0.03 (P < 0.05). The structural analysis of LD showed that 51 +/- 5% of the fibers were type I. The diameter was 56 +/- 9 microns for type I fibers and 61 +/- 9 microns for type II fibers, whereas the hypertrophy factor was 87 +/- 94 and 172 +/- 208 for type I and II fibers, respectively. Interestingly, the histogram distribution of the LD fibers was unimodal in two of the three individuals with normal lung function and bimodal (additional mode of hypertrophic fibers) in seven of the nine patients with chronic obstructive pulmonary disease. An inverse relationship was found between the %FEV1-forced vital capacity ratio and both the diameter of the fibers (type I: r = -0.773, P < 0.005; type II: r = -0.590, P < 0.05) and the hypertrophy factors (type I: r = -0.647, P < 0.05; type II: r = -0.575, P = 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed2000

Pulmonary function and complications following chemotherapy and stem cell support in breast cancer.

Pulmonary complications are frequent in patients treated with high-dose chemotherapy and autologous bone marrow transplantation for breast cancer or other solid tumours. This study analyses the development of lung toxicity, changes in respiratory function and occurrence of clinical symptoms in a group of 24 patients (mean age 46+/-7 yrs) who underwent high-dose sequential chemotherapy (HDS) with autologous peripheral blood stem cell (PBSC) support for high risk breast cancer. Clinical examination, chest radiography and lung function tests were performed before the HDS and 1 and 3 months following transplantation. Only one patient developed acute interstitial pulmonary disease which resolved after prednisone therapy. No patients developed infectious complications after transplantation. Baseline respiratory function was normal for most of the parameters. Only lung diffusing capacity of the lung for carbon monoxide (TL,CO) and maximal inspiratory pressure were below the normal range. Following PBSC transplantation only one patient had an altered vital capacity while 72.3% of patients had reduced TL,CO values at 1 month and 54.5% at 3 months after transplantation. Maximal expiratory flow at 25% forced vital capacity, TL,CO and maximal expiratory pres-sure were significantly reduced after 1 month but recovered slightly by 3 months. Arterial oxygen tension between baseline and both follow-up evaluations declined significantly in patients seropositive for human cytomegalovirus. It is concluded that this high-dose sequential chemotherapy regimen is acceptably safe since no pulmonary related mortality or respiratory infectious complications were observed. The only lung function alteration induced was an isolated diffusing capacity of the lung for carbon monoxide impairment, clinically negligible and partially recovered within 3 months.

Adult↗
PubMed2001

[Strength of inspiratory muscles in chronic heart failure and chronic pulmonary obstructive disease].

BACKGROUND: The maximal pressure generated by inspiratory muscles (PIMax) is an index of their strength which is diminished in both chronic obstructive pulmonary disease (COPD) and chronic heart failure (CHF). Although inspiratory muscle power output (IMPO), which includes both strength and velocity of shortening, has been shown to be reduced in COPD, there is no information regarding IMPO in CHF. AIM: To measure IMPO in patients with CHF and COPD. PATIENTS AND METHODS: We studied 9 CHF patients with functional capacity II and III and 9 patients with severe COPD. Eight normal subjects of similar ages were included as controls. Power output was measured using the incremental threshold loading test. RESULTS: Maximal IMPO was significantly reduced in both groups of patients. Power output developed with each increasing load was also diminished, basically as a consequence of a reduction in Vinsp. The degree of dyspnea at the end of the test was greater in COPD than in CHF patients and normal subjects. For a given level of power, dyspnea was also greater in patients than in normals subjects. There was no decrease in SpO2 during the test. CONCLUSIONS: IMPO is equally reduced in COPD and CHF patients. Power output is better related to dyspnea than PIMax, probably because of the inclusion of shortening velocity.

Analysis of Variance↗
PubMed1991

Extubation after transsternal thymectomy for myasthenia gravis: a prospective analysis.

Recommendations concerning postoperative extubation after thymectomy for myasthenia gravis are presently based upon retrospective chart reviews. We present the results of a prospective investigation of time to extubation after thymectomy for 14 patients over a 12-month period based upon a protocol that included preoperative immunologic therapy, combined epidural and general anesthesia, postoperative epidural narcotic analgesia, and a standardized approach to discontinuation of ventilatory support. After a neurologist took measures to optimize preoperative neuromuscular function, all 14 patients received agents to produce lumbar epidural anesthesia and light general anesthesia. Muscle relaxants were avoided in all but one patient. Postoperative analgesia was initially maintained with epidural hydromorphone, then therapy was switched to patient-controlled intravenous morphine sulfate. Criteria for weaning from mechanical ventilation, first measured at the end of anesthesia, were partial pressure of oxygen (arterial) greater than or equal to 90 mm Hg (fraction of inspired oxygen = 0.40), partial pressure of carbon dioxide (arterial) less than or equal to 50 mm Hg, pH greater than or equal to 7.30, and respiratory rate less than or equal to 30 breaths/min. If these criteria were not met, ventilatory support was continued postoperatively with intermittent mandatory ventilation, and the patient was weaned gradually from this support. Criteria for extubation included meeting the criteria for weaning, vital capacity greater than or equal to 10 mL/kg, and inspiratory pressure better than -30 cm H2O. Criteria for reintubation included tachypnea (respiratory rate greater than 40 breaths/min), respiratory acidosis not due to narcotics, or vital capacity less than or equal to 8 mL/kg. The mean time to extubation was 9 hours (range, 0.75 to 25 hours). Mean preoperative vital capacity was 2.59 +/- 0.64 L (range, 1.90 to 4.20), which decreased approximately 50% to 1.19 +/- 0.39 L (range, 0.70 to 2.0) at the time of extubation. No patient required reintubation. Half of the patients required postoperative anticholinesterase therapy based upon serial neurologic examinations; there were no instances of cholinergic crisis. Thirteen patients returned to the ward on the first postoperative day, and one on the second day. Thirteen patients preferred epidural analgesia to patient-controlled analgesia. The time to extubation and average length of stay in an intensive care setting were markedly reduced compared to those reported in previous retrospective studies. We conclude that a multidisciplinary approach that optimizes neuromuscular function and decreases poststernotomy pulmonary insult will shorten the time to extubation and decrease the length of stay in the intensive care or recovery room after thymectomy.

Adolescent↗
PubMed1997

Size and strength of the respiratory and quadriceps muscles in patients with chronic asthma.

There have been few studies of respiratory and limb muscle size and function in middle-aged patients with asthma and persistent airways obstruction. We have compared the forces generated by the respiratory and thigh muscles with their dimensions assessed by ultrasound in nine middle-aged patients with chronic asthma (mean age 56 (SD 8) yrs; functional residual capacity/total lung capacity ratio (FRC/TLC) 60 (10)%), and in nine normal subjects (aged 53 (7) yrs; FRC/TLC 55 (5)%). Diaphragm thickness was measured at the zone of apposition by B-mode ultrasound during relaxation (DiTrelax) and during a maximum-effort inspiratory manoeuvre (DiTpI,max) at FRC. Cross-sectional area of the relaxed rectus femoris muscle (ARF) was determined by ultrasound at mid-thigh level. Isometric strength of the right quadriceps muscle group was measured during maximum voluntary contraction. Asthmatic patients had preserved quadriceps strength and ARF but moderately impaired maximum inspiratory pressure (PI,max) (-52 (18) cmH2O) and thicker DiTrelax (2.2 (0.4) mm), compared to normal subjects (-73 (21) cmH2O and 1.7 (0.3) mm, respectively). Middle-aged patients with chronic asthma and a small increase in functional residual capacity/total lung capacity ratio have preserved limb muscle force and dimensions, modestly impaired inspiratory muscle strength, and slightly increased thickness of the costal diaphragm. Future studies of respiratory muscle function in asthma should be aided by measurement of diaphragm thickness and of limb muscle strength and size. Such studies are required particularly in older patients with severe hyperinflation who are most likely to have impairment of muscle function.

Airway Obstruction↗