Accelerometry of Adductor Pollicis Muscle Predicts Recovery of Respiratory Function from Neuromuscular Blockade

Background: Residual paralysis increases the risk of pulmonary complications but is difficult to detect. To test the hypothesis that accelerometry predicts effects of residual paralysis on pulmonary and upper airway function, the authors related tests of pulmonary and pharyngeal function to accelerometry of adductor pollicis muscle in 12 partially paralyzed volunteers.

Methods: Rocuronium (0.01 mg/kg + 2-10 [mu]g [middle dot] kg-1 [middle dot] min-1) was administered to maintain train-of-four (TOF) ratios (assessed every 15 s) of approximately 0.5 and 0.8 over a period of more than 5 min. The authors evaluated pharyngeal and facial muscle functions during steady state relaxation and performed spirometric measurements every 5 min until recovery. Upper airway obstruction was defined as a mean ratio of expiratory and inspiratory flow at 50% of vital capacity of greater than 1. The TOF ratio associated with "acceptable" pulmonary recovery (forced vital capacity and forced inspiratory volume in 1 s of >=90% of baseline) was calculated using a linear regression model.

Results: At peak blockade (TOF ratio 0.5 +/- 0.16), forced inspiratory flow was impaired (53 +/- 19%) to a greater degree than forced expiratory flow (75 +/- 20%) with a mean ratio of expiratory and inspiratory flow at 50% of vital capacity of 1.18 +/- 0.6. Upper airway obstruction, observed in 8 of 12 volunteers, paralleled an impaired ability to swallow reported by 10 of 12 volunteers. In contrast, all volunteers except one could sustain a head lift for more than 5 s. The authors calculated that a mean TOF ratio of 0.56 (95% confidence interval, 0.22-0.71) predicts "acceptable" recovery of forced vital capacity, whereas forced inspiratory volume in 1 s was impaired until a TOF ratio of 0.95 (0.82-1.18) was reached. A 100% recovery of TOF ratio predicts an acceptable recovery of forced vital capacity, forced inspiratory volume in 1 s, and mean ratio of expiratory and inspiratory flow at 50% of vital capacity in 93%, 73%, and 88% of measurements (calculated negative predictive values), respectively.     

Postoperative upper airway obstruction after recovery of the train of four ratio of the adductor pollicis muscle from neuromuscular blockade

Anesthetics, and even minimal residual neuromuscular blockade, may lead to upper airway obstruction (UAO). In this study we assessed by spirometry in patients with a train-of-four (TOF) ratio >0.9 the incidence of UAO (i.e., the ratio of maximal expiratory flow and maximal inspiratory flow at 50% of vital capacity [MEF50/MIF50] >1) and determined if UAO is induced by neuromuscular blockade (defined by a forced vital capacity [FVC] fade, i.e., a decrease in values of FVC from the first to the second consecutive spirometric maneuver of > or =10%). Patients received propofol and opioids for anesthesia. Spirometry was performed by a series of 3 repetitive spirometric maneuvers: the first before induction (under midazolam premedication), the second after tracheal extubation (TOF ratio: 0.9 or more), and the third 30 min later. Immediately after tracheal extubation and 30 min later, 48 and 6 of 130 patients, respectively, were not able to perform spirometry appropriately because of sedation. The incidence of UAO increased significantly (P < 0.01) from 82 of 130 patients (63%) at preinduction baseline to 70 of 82 patients (85%) after extubation, and subsequently decreased within 30 min to values observed at baseline (80 of 124 patients, 65%). The mean maximal expiratory flow and maximal inspiratory flow at 50% of vital capacity ratio after tracheal extubation was significantly increased from baseline (by 20%; 1.39 +/- 1.01 versus 1.73 +/- 1.02; P < 0.01), and subsequently decreased significantly to values observed at baseline (1.49 +/- 0.93). A statistically significant FVC fade was not present, and a FVC fade of > or =10% was observed in only 2 patients after extubation. Thus, recovery of the TOF ratio to 0.9 predicts with high probability an absence of neuromuscular blocking drug-induced UAO, but outliers, i.e., persistent effects of neuromuscular blockade on upper airway integrity despite recovery of the TOF ratio, may still occur.     

Predictive value of mechanomyography and accelerometry for pulmonary function in partially paralyzed volunteers

BACKGROUND: Accelerometry (ACM) of adductor pollicis muscle has been used for monitoring of neuromuscular blockade but its validity compared with the gold standard, mechanomyography (MMG), has been questioned. During neuromuscular blockade we compared these methods and we assessed pulmonary function. METHODS: In awake partially paralyzed volunteers we spirometrically assessed pulmonary function every 5 min until recovery. Rocuronium (0.01 mg kg(-1) + 2-10 microg kg(-1) min(-1)) was administered to maintain train-of-four (TOF)-ratios (assessed every 15 s) of approximately 0.5 and 0.8 over a period of more than 5 min. The TOF-ratio associated with 'acceptable' pulmonary recovery [forced vital capacity (FVC) and forced inspiratory volume in 1 s (FIV1) of > or =90% of baseline] was calculated using a linear regression model. During 5-min periods of repetitive nerve stimulation we compared the squared residuals of the FVC and FIV1 estimates from TOFACM vs. TOFMMG, and compared variance of values derived from ACM and MMG using Wilcoxon's test. RESULTS: Limits of agreement of TOF-ratio derived from ACM and MMG were wide [0.15+/-0.016 (SD)], and variability of TOFACM exceeded that of TOFMMG[variance: 77+/-105 vs. 51+/-55% (P<0.01)]. Calculated TOF(ACM) and TOFMMG ratios of 0.56 (0.22-0.71) [mean (95%CI) and 0.6 (0.28-0.74)], respectively, predict 'acceptable' (90%) recovery of FVC while FIV1 remains impaired until TOF-ratios of 0.91 (0.82-1.07) and 0.95 (0.82-1.18), respectively. In turn, TOFMMG (TOFACM) of unity predicted 'acceptable' recovery of FVC and FIV1 in 94 (93) % and 68 (73) % of measurements, respectively. CONCLUSIONS: Accelerometry predicts effects of relaxation on pulmonary function as valid as the gold standard mechanomyography. We recommend that recovery of TOF ratio to 0.9-1.0 should be used as an indication of sufficient neuromuscular recovery in daily practice.     

Airflow in unilateral vocal cord paralysis before and after Teflon injection.

The effect of unilateral vocal cord paralysis and intracordal Teflon injection on maximum expiratory and inspiratory flows was studied in 15 consecutive patients. Ten patients had a ratio of forced expiratory flow to forced inspiratory flow at 50% vital capacity (Ve50/Vi50) more than one. Of the remaining five, four had low Ve50 consistent with underlying bronchial disease. Repeat studies were obtained in 10 patients two or more weeks after Teflon injection into a vocal cord for voice therapy. Maximum expiratory flow rates did not change (means 6.64 +/- 0.881/sec before and 6.47 +/- 1.101/s after injection). Inspiratory flow at 50% vital capacity improved in all six patients with a forced expiratory volume in one second (FEV1) greater than 75% of the forced vital capacity (FVC). In patients with an FEV1 less than 75% FVC, no consistent changes could be seen. We conclude that a high Ve50/Vi50 suggestive of variable extrathoracic airways obstruction is a frequent finding in the presence of unilateral vocal cord paralysis. Teflon injection does not cause a significant reduction in forced expiratory flows and improves inspiratory flows in subjects without evidence of underlying bronchial disease.     

Airway Obstruction and Perioperative Complications in Smokers Undergoing Abdominal Surgery

Background: The goal of this study was to determine whether airway obstruction determined by preoperative spirometry predicts perioperative complications in smokers undergoing abdominal surgery whose treatment is managed according to current clinical practice.

Methods: A pulmonary function database identified patients undergoing abdominal surgery who met the following criteria for airway obstruction (n = 135): a forced expiratory volume less than 40% of predicted normal value, a forced expiratory volume:forced vital capacity ratio less than the lower limit of predicted normal, a smoking history of more than 20 pack-years, and an age older than 35 yr. A group of patients without airway obstruction (n = 135) was matched for gender, surgical site (upper vs. lower abdominal), smoking history, and age. Medical records were reviewed by an abstractor to identify perioperative complications that occurred within 30 days after surgery.

Results: The forced expiratory volume values were 0.9 +/- 0.2 l (mean +/- SD) and 2.9 +/- 0.6 l in patients with and without airway obstruction, respectively. When analyzed by conditional logistic regression using the 1:1 matched-pairs feature, including age, pack-year smoking history, site of incision, and current smoking status as covariates, in patients with airway obstruction bronchospasm was more likely to develop (odds ratio, 6.9 [95% confidence interval, 1.2 to 38.4]) but the patients were not more likely to need prolonged endotracheal intubation (odds ratio, 1.1 [95% confidence interval, 0.4 to 3.2]). They were also no more likely to need prolonged intensive care admission or readmission. The frequency of other complications was less than 5%.     

Effect of helium and oxygen on airflow in a narrowed airway.

A mixture of 80% helium and 20% oxygen has physical properties that increase airflow and decrease resistance in the airway when used as a portion of inspired gas. This study was designed to demonstrate and quantify the effects of a helium-oxygen mixture in a normal airway and when airway resistance is increased. Thirty healthy volunteers were studied breathing room air and the helium-oxygen mixture through a normal airway and an airway that included a resistor. Pulmonary function tests, directed by a registered respiratory therapist, were performed on all subjects using a computerized spirometer. The functional vital capacity, one-second forced expiratory volume, half-second forced expiratory volume, and peak inspiratory flow rate were analyzed. There was a statistically significant increase in 1-second forced expiratory volume using a helium-oxygen mixture in a normal airway. All pulmonary function test scores statistically improved when volunteers inspired helium and oxygen through the restricted airway, demonstrating that helium and oxygen can increase airflow in the presence of an increased airway resistance. This substantiates a role for helium and oxygen in treating conditions associated with decreased airway size and increased airway resistance.     

Physiological effect of endobronchial radiotherapy in patients with major airway occlusion by carcinoma.

BACKGROUND: Endobronchial radiotherapy by a high dose rate remote after-loading technique (high dose rate brachytherapy) has become an established treatment for major airway occlusion by inoperable carcinoma of the bronchus. Only limited objective data on its effect on pulmonary physiology and on radiographic and bronchoscopic appearances are available. The aim of this study was to make a detailed assessment of patients before and after high dose rate brachytherapy to determine which investigations were useful and to generate data for comparing this with other methods of treatment. METHODS: Twenty patients with major airway obstruction by inoperable lung cancer underwent a detailed assessment before receiving endobronchial radiotherapy (15 Gy at 1 cm in a single fraction) and six weeks after treatment. This included chest radiography, computed tomography of the thorax, bronchoscopy including an obstruction index, five minute walking tests, isotope ventilation and perfusion lung scanning, and full lung function tests with maximum inspiratory and expiratory flow-volume loops. RESULTS: Nineteen patients (mean age 69 years) completed the study. Symptomatic improvement occurred in 17 patients. A collapsed lobe or lung, seen on the chest radiograph in 13, reexpanded in nine. Bronchoscopic appearances improved in 18, the mean obstruction index decreasing from 6.2 to 2.8. The isotope scans showed significant increases in the percentage of total lung ventilation (V) and perfusion (Q) measured over the abnormal lung (V 17.7% to 27.7%, Q 15.1 to 21.9%). Five minute walking distance (305 to 329 m), forced expiratory volume in one second (FEV1 1.45 to 1.61 l), forced vital capacity (FVC 2.17 to 2.48 l) and ratio of forced expiratory to forced inspiratory flow rate at 50% vital capacity (FEF50/FIF50 0.58 to 0.88) all increased significantly. CONCLUSIONS: Endobronchial radiotherapy led to subjective benefit in most cases in terms of symptoms and bronchoscopic and radiological appearances. There was objective improvement in spirometric indices and in exercise tolerance with increased pulmonary ventilation and perfusion and evidence of decreased intrathoracic airway obstruction.     

Higher prevalence of obstructive airway disease in patients with thoracic or abdominal aortic aneurysm

BACKGROUND AND AIM: The risk factors of aortic aneurysm (AA) are comparable with those described for chronic obstructive pulmonary disease. This study was performed to determine whether patients with AA have a higher than average prevalence of obstructive airway disease. METHODS: We performed pulmonary function tests in 240 consecutive patients (182 men and 58 women; age, 70 +/- 10 years) with thoracic or abdominal AA. The results were compared with those in individuals without obvious cardiovascular disease (control) and in patients with coronary artery disease who were matched for age, gender, smoking status, and other atherosclerotic risk factors. RESULTS: Patients in the AA group had a lower forced expiratory volume in 1 second/forced vital capacity (%) and carbon monoxide diffusing capacity (%/predicted value) than did the control group (P <.01). The proportion of patients with airway obstruction, defined as forced expiratory volume in 1 second/forced vital capacity of 70% or less, was higher in the AA group (100/240; 42%) than in the control (51/223; 23%) and coronary artery disease (43/238; 18%) groups. Multiple logistic regression analysis results revealed that the presence of an AA and male gender were associated with a higher risk of airway obstruction (odds ratio, 2.928; 95% CI, 1.722 to 4.979; and odds ratio, 1.622; 95% CI, 1.055 to 2.493, respectively). CONCLUSION: These data suggest that AA may be a risk factor indicative of the presence of chronic obstructive pulmonary disease. A higher prevalence of depressed pulmonary function should be suspected as a preoperative risk in presence of thoracic or abdominal AA as compared with other types of cardiovascular disorders.     

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.     

Pulmonary function and head lift during spontaneous recovery from pipecuronium neuromuscular block

We have studied in seven healthy conscious volunteers the correlationbetween the electro-myographic (EMG) and clinical criteria usedto identify adequate recovery from sub-paralysing doses of pipecuronium.Pipecuronium (mean dose 1.88 (range 0.92–3.16) mg) wasadministered to reach a T4/T1 ratio of 0.5; full recovery to1.0 was produced in a mean time of 25.3 (14–39) min. Duringrecovery from neuromuscular block, we measured tidal volume,forced vital capacity (FVC), forced expiratory volume in 1 s(FEV₁) negative inspiratory pressure (NIP), peak expiratoryflow rate (PEFR), mid-expiratory flow rate (MEFR) and 5-s headlift. The assessments were started when the train-of-four (TOF)ratio reached 0.5 ± 0.001 and repeated at each 0.1 ±0.001 increase up to a ratio of 1.0. All volunteers showed ptosisand diplopia after the first dose and difficulty in swallowingwith subsequent doses. They also experienced a pleasant, relaxingsedative sensation. All could sustain head lift for 5 s at aTOF ratio of 0.5 and higher, except for one subject who couldnot lift his head only at a ratio of 0.5. There was a statisticallysignificant decrease in FVC, FEV, and PEFR with a nonsignificantdecrease in other pulmonary measurements, except for NIP whichonly decreased significantly at a ratio of 0.5. These changesare probably of no clinical importance. All the measured respiratoryvariables returned to control values at a TOF ratio of 0.9.(Br.J. Anaesth. 1995; 74: 16–19)     

Effects of posture on flow-volume curves during normocapnia and hypercapnia in patients with obstructive sleep apnoea.

BACKGROUND: A high ratio of forced expiratory to forced inspiratory maximal flow at 50% of vital capacity (FEF50/FIF50) may identify upper airway dysfunction. Since hypercapnia increases the motor activity of airway dilating muscles its effects on the maximum expiratory and inspiratory flow-volume curves (MEIFV) in patients with obstructive sleep apnoea and in normal subjects in different postures was studied. METHODS: The effects of posture on the maximum expiratory and inspiratory flow-volume curves during the breathing of air and 7% carbon dioxide in 11 patients with obstructive sleep apnoea were compared with those in nine normal subjects. Measurements were made in the sitting, supine, and right lateral recumbent positions. Forced expiratory flow at 50% vital capacity (FEF50), forced inspiratory flow at 50% vital capacity (FIF50) and FEF50/FIF50 were determined. RESULTS: In the normal subjects FEF50, FIF50, and FEF50/FIF50 were not affected by change in posture or by breathing carbon dioxide. In the patients there was a fall in FIF50 and an increase in FEF50/FIF50 when breathing air in the supine position compared with values in the seated and lateral position. While they were breathing carbon dioxide there was a slight increase in FEF50 when patients were seated or in the lateral position compared with values during air breathing. Hypercapnia abolished the effects of posture on FEF50/FIF50. Values for FEF50/FIF50 in the supine position while they were breathing air correlated with the apnoeic index but not with other polysomnographic data. CONCLUSION: In patients with obstructive sleep apnoea the upper airway is prone to collapse during inspiration when the patient is supine, even when awake; this tendency can be reversed by breathing carbon dioxide.     

Dynamic airflow limitation after topical anaesthesia of the upper airway

This prospective before-and-after observational study investigated the effect of upper airway anaesthesia on dynamic airflow. Six consenting ASA 1 adults, all authors of this study, underwent a series of spirometric measurements before and after topical anaesthesia of the upper airway using lignocaine. Peak inspiratory flow rate, forced inspiratory flow between 25% and 75% of the maximum inhaled volume, forced expiratory volume at 1 second, and forced vital capacity in the supine and sitting positions were measured. The measured inspiratory parameters were significantly reduced after lignocaine topical anaesthesia of the upper airway. Expiratory flow parameters were not affected. We conclude that topical anaesthesia of the upper airway leads to dynamic inspiratory airflow limitation.     

Ministernotomy versus complete sternotomy for coronary bypass operations: no difference in postoperative pulmonary function

OBJECTIVES: Less-invasive approaches in cardiac operations offer certain cosmetic advantages, but it is unclear whether there are additional positive effects with regard to the postoperative recovery of patients. The aim of this prospective and randomized study was to ascertain whether partial inferior midline sternotomy can improve pulmonary function, one of the best quantifiable parameters of postoperative recovery, after coronary artery bypass operations when compared with the standard full midline approach. METHODS: One hundred patients scheduled for elective coronary artery bypass grafting were randomized either for a full median sternotomy (standard sternotomy group, n = 50) or for a partial inferior sternotomy (ministernotomy group, n = 50). The following pulmonary features were assessed: vital capacity, forced expiratory volume, percentage of forced expiratory volume from vital capacity, total lung capacity, residual volume, maximum inspiratory pressure, and maximum expiratory pressure. Tests were performed preoperatively and on the fourth and tenth postoperative days. RESULTS: On the fourth postoperative day, both groups had a significant decrease in vital capacity (percentage of predicted values) when compared with preoperative values (preoperative vs fourth day: standard sternotomy group, 87.8% +/- 14.3% vs 42.1% +/- 10.2% [P <.0001]; ministernotomy group, 84.5% +/- 14.3% vs 41.5% +/- 11.8% [P <.0001]), with a significant tendency for recovery from the fourth to the tenth postoperative day (fourth vs tenth postoperative day: standard sternotomy group, 42.1% +/- 10.2% vs 66.3% +/- 12.3% [P =.001]; ministernotomy group, 41.5% +/- 11.8% vs 61.3% +/- 13.1 % [P =.002]). There were no differences in any test results between the groups on either the fourth or the tenth postoperative day. CONCLUSION: A less-invasive approach for coronary artery bypass operations with a partial inferior sternotomy does not improve early postoperative pulmonary function when compared with the conventional approach with a full sternotomy.     

Correlation between tests of small airway function

Cochrane, G. M., Benatar, S. R., Davis, J., Collins, J. V., and Clark, T. J. H. (1974.)Thorax,29, 172-178. Correlation between tests of small airway function. To compare and correlate tests of small airway function we have measured residual volume, frequency dependence of compliance, `closing volume', maximal expiratory flow rate at 50% and 25% of vital capacity, maximal expiratory flow rate at 50% of total lung capacity, and forced expired time in 10 health non-smoking male subjects and 10 non-smoking asthmatics who on the day of the study had no symptoms of airway obstruction. There was no evidence to suggest that any one particular test was more sensitive than others in detecting the presence of small airways obstruction. The closest correlation was between maximal expiratory flow rate at both 25% of vital capacity and 50% of total lung capacity and the forced expired time. It is argued that a prolonged forced expired time in the presence of normal dynamic lung volumes may be the most easily applicable screening test for early small airways obstruction.     

Measurement of physiological recovery from exacerbation of chronic obstructive pulmonary disease using within-breath forced oscillometry

BACKGROUND: Within-breath reactance from forced oscillometry estimates resistance via its inspiratory component (X(rs,insp)) and flow limitation via its expiratory component (X(rs,exp)). AIM: To assess whether reactance can detect recovery from an exacerbation of chronic obstructive pulmonary disease (COPD). METHOD: 39 subjects with a COPD exacerbation were assessed on three occasions over 6 weeks using post-bronchodilator forced oscillometry, arterial blood gases, spirometry including inspiratory capacity, symptoms and health-related quality of life (HRQOL). RESULTS: Significant improvements were seen in all spirometric variables except the ratio of forced expiratory volume in 1 s (FEV(1)) to vital capacity, ranging in mean (SEM) size from 11.0 (2.2)% predicted for peak expiratory flow to 12.1 (2.3)% predicted for vital capacity at 6 weeks. There was an associated increase in arterial partial pressure of oxygen (PaO(2)). There were significant mean (SEM) increases in both X(rs,insp) and X(rs,exp) (27.4 (6.7)% and 37.1 (10.0)%, respectively) but no change in oscillometry resistance (R(rs)) values. Symptom scales and HRQOL scores improved. For most variables, the largest improvement occurred within the first week with spirometry having the best signal-to-noise ratio. Changes in symptoms and HRQOL correlated best with changes in FEV(1), PaO(2) and X(rs,insp). CONCLUSIONS: The physiological changes seen following an exacerbation of COPD comprised both an improvement in operating lung volumes and a reduction in airway resistance. Given the ease with which forced oscillometry can be performed in these subjects, measurements of X(rs,insp) and X(rs,exp) could be useful for tracking recovery.     

Pulmonary function for pectus excavatum at long-term follow-up

PURPOSE: The aim of this article was to assess whether and to what extent pulmonary function recovered to normal degree postoperatively and to investigate the changes in pulmonary function after surgical correction and the value of surgical correction. METHODS: A total of 27 patients who could be questioned and examined in person at the outpatient department of our hospital were included in this study. Of these patents, 24 were boys and 3 were girls. Their ages ranged from 3 to 16 years (mean, 8.67) at follow-up. The mean age at surgery was 4 years, and mean years of follow-up was 6.8. Pulmonary functional measurements included in vital capacity (VC), total lung capacity (TLC), residual volume (RV), functional residual capacity (FRC), RV-TLC ratio, maximal voluntary ventilation (MVV), force ventilatory capacity (FVC), forced expiratory volume in one second (FEV1), maximal midexpiratory flow curve (MMEF), maximal expiratory flow in 75% vital capacity (V75), maximal expiratory flow in 50% vital capacity (V50), maximal expiratory flow in 25% vital capacity (V25), and breathing reserve ratio (BR). RESULTS: TLC, FRC, MVV, MMEF, V75, and V50 values were not different from the normal values. IVC, FVC, FEV1, and V25 values were decreased significantly compared with the normal values. The RV and RV-TLC were high in 87.5% cases. CONCLUSIONS: Preoperative symptoms obviously improved after operation. There was little airway obstruction in the patients postoperatively. The patients with pectus excavatum should be operated on as soon as possible.     

Lung function under high thoracic segmental epidural anesthesia with ropivacaine or bupivacaine in patients with severe obstructive pulmonary disease undergoing breast surgery

BACKGROUND: Because general anesthesia with tracheal intubation can elicit life-threatening bronchospasm in patients with bronchial hyperreactivity, epidural anesthesia is often preferred. However, segmental high thoracic epidural anesthesia (sTEA) causes pulmonary sympathetic and respiratory motor blockade. Whether it can be safely used for chest wall surgery as a primary anesthetic technique in patients with chronic obstructive pulmonary disease or asthma is unclear. Furthermore, ropivacaine supposedly evokes less motor blockade than bupivacaine and might minimize side effects. To test the feasibility of the technique and the hypotheses that (1) sTEA with ropivacaine or bupivacaine does not change lung function and (2) there is no difference between sTEA with ropivacaine or bupivacaine, the authors studied 20 patients with severe chronic obstructive pulmonary disease (forced expiratory volume in 1 s [FEV1] = 52.1 +/- 17.3% of predicted [mean +/- SD]) or asthma who were undergoing breast surgery. METHODS: In a double-blind, randomized fashion, sTEA was performed with 6.6 +/- 0.5 ml of either ropivacaine, 0.75% (n = 10), or bupivacaine, 0.75% (n = 10). FEV1, vital capacity, FEV1 over vital capacity, spread of analgesia (pin prick), hand and foot skin temperatures, mean arterial pressure, heart rate, and local anesthetic plasma concentrations were measured with patients in the sitting and supine positions before and during sTEA. RESULTS: Segmental high thoracic epidural anesthesia (segmental spread C4-T8 [bupivacaine] and C5-T9 [ropivacaine]) significantly decreased FEV1 from 1.22 +/- 0.54 l (supine) to 1.09 +/- 0.56 l (ropivacaine) and from 1.23 +/- 0.49 l to 1.12 +/- 0.46 l (bupivacaine). In contrast, FEV1 over vital capacity increased from 64.6 +/- 13.5 to 68.2 +/- 14.5% (ropivacaine) and from 62.8 +/- 12.4 to 66.5 +/- 13.6% (bupivacaine). There was no difference between ropivacaine and bupivacaine. Skin temperatures increased significantly, whereas arterial pressure and heart rate significantly decreased indicating widespread sympathetic blockade. All 20 patients tolerated surgery well. CONCLUSIONS: Despite sympathetic blockade, sTEA does not increase airway obstruction and evokes only a small decrease in FEV1 as a sign of mild respiratory motor blockade with no difference between ropivacaine and bupivacaine. Therefore, sTEA can be used in patients with severe chronic obstructive pulmonary disease and asthma undergoing chest wall surgery as an alternative technique to general anesthesia.     

Tidal expiratory flow patterns in airflow obstruction.

Tidal expiratory flow pattern was analysed in 99 subjects with a view to assessing it as a quantitative measurement of airflow obstruction. Fifteen normal volunteers, nine patients with dyspnoea referred for investigation in whom airway resistance was within normal limits, 24 patients with restrictive lung disorders, and 51 patients with airway obstruction were studied. The expiratory flow pattern against time had a quadrilateral configuration in airway obstruction, which differed from the more sinusoidal form that is seen in subjects without airflow obstruction. The rapid rise to tidal peak flow was analysed in two ways, percentage of volume expired at tidal peak flow (delta V/V) and percentage of expiratory time to tidal peak flow (delta t/t). Both these indices correlated significantly with conventional measurements of airway obstruction. The pattern of expiratory flow in airflow obstruction during quiet breathing resembles that of a forced expiratory maneuver at similar lung volumes. In some cases this may be caused by dynamic compression occurring during tidal breathing. In others, the pattern may result from the static recoil of the lung being permitted to drive flow freely in expiration, rather than being braked by postinspiratory contraction of inspiratory musculature.     

Effects of an external resistance on maximum flow in chronic obstructive lung disease: implications for recognition of coincident upper airway obstruction.

To determine how the presence of generalised airflow limitation due to chronic obstructive lung disease affects the recognition of simulated upper airway obstruction, a study was carried out in 12 patients (mean (SD) age 57 (7) years) with chronic obstructive lung disease (FEV1% predicted 53 (22), range 21-70) and 12 matched control subjects. Patients and control subjects performed maximal inspiratory and expiratory flow-volume curves in a variable volume plethysmograph with and without upper airway obstruction simulated at the mouth with a series of polythene washers of internal diameter 4, 6, 8, 10, and 12 mm. In patients, as in normal subjects, peak expiratory flow (PEF) and maximum inspiratory flow at 50% of vital capacity (Vmax50) were more sensitive to upper airway obstruction than were FEV1 or maximum expiratory flow at 50% VC (VEmax50); but the reductions in all indices caused by simulated upper airway obstruction were smaller in the patients than in the controls. The fall in PEF (whether expressed in absolute units or as a percentages) consequent on severe (4 mm) upper airway obstruction became smaller with increasing severity of chronic obstructive lung disease. The subjects also produced flow-volume curves with and without 6 mm upper airway obstruction while breathing helium and oxygen (heliox). In both groups the effects of heliox on PEF and Vmax50 were increased when upper airway obstruction was simulated. It was confirmed that the functional recognition of upper airway obstruction is more difficult in patients with chronic obstructive lung disease than in normal subjects and this difficulty increases with severity of disease; an unusually large increase in PEF or Vmax50 while the patient is breathing heliox should raise the suspicion of coexisting upper airway obstruction, but such a pattern is not specific.     

Neuromuskuläre Restblockaden

Even after administration in routine clinical dosages, muscle relaxants can lead to long-lasting residual blockades which increase the risk of severe postoperative pulmonary complications. Even without the additional effects from analgetics, sedatives or anaesthetics, a partial neuromuscular blockade, which cannot reliably be avoided either by the anaesthetist alone or by the additional use of nerve stimulators (train-of-four [TOF] ratio 0.5-0.9), can cause reductions in the vital capacity and the hypoxic breathing response, as well as obstruction of the upper airway and disruption of pharangeal function. The extent of neuromuscular recovery after an operation depends on the muscle relaxant used, the duration of administration, the anaesthetic technique and possible accompanying illnesses of the patient. It must basically be assumed that residual neuromuscular blockades are more frequent after administration of slow acting muscle relaxants such as pancuronium, than after the use of medium or rapid acting substances. If the course of a neuromuscular blockade is continually monitored during the whole anaesthetic procedure using the TOF ratio and not only occasionally at the end, a TOF ratio of 1 measured with an acceleromyograph (e.g. TOF-watch) promises an adequate neuromuscular recovery from the effects of muscle relaxants.