潮气流速容量曲线测定在毛细支气管炎患儿中的意义

目的通过对240例毛细支气管炎患儿的潮气流速容量曲线的测定,以探讨毛细支气管炎患儿气道阻力的变化规律。方法采用美国Sensor Medics公司生产的2600型全自动小儿肺功能测定仪,在潮气状态下对毛细支气管炎患儿进行肺功能测定,连续记录潮气呼气流速容量曲线。结果所有毛细支气管炎患儿都有不同程度的气道阻力增高,尤以小气道阻力增高为主,其增高程度与患儿病情的轻重呈正相关。结论毛细支气管炎患儿应尽早进行潮气流速容量曲线的测定,以判断患儿病情,为其治疗和护理提供客观依据;潮气流速容量曲线的测定操作简单易行,并且无创,在临床上应广泛应用。     

Effects of tidal volume on work of breathing during lung-protective ventilation in patients with acute lung injury and acute respiratory distress syndrome

OBJECTIVE: To assess the effects of step-changes in tidal volume on work of breathing during lung-protective ventilation in patients with acute lung injury (ALI) or the acute respiratory distress syndrome (ARDS). DESIGN: Prospective, nonconsecutive patients with ALI/ARDS. SETTING: Adult surgical, trauma, and medical intensive care units at a major inner-city, university-affiliated hospital. PATIENTS: Ten patients with ALI/ARDS managed clinically with lung-protective ventilation. INTERVENTIONS: Five patients were ventilated at a progressively smaller tidal volume in 1 mL/kg steps between 8 and 5 mL/kg; five other patients were ventilated at a progressively larger tidal volume from 5 to 8 mL/kg. The volume mode was used with a flow rate of 75 L/min. Minute ventilation was maintained constant at each tidal volume setting. Afterward, patients were placed on continuous positive airway pressure for 1-2 mins to measure their spontaneous tidal volume. MEASUREMENTS AND MAIN RESULTS: Work of breathing and other variables were measured with a pulmonary mechanics monitor (Bicore CP-100). Work of breathing progressively increased (0.86 +/- 0.32, 1.05 +/- 0.40, 1.22 +/- 0.36, and 1.57 +/- 0.43 J/L) at a tidal volume of 8, 7, 6, and 5 mL/kg, respectively. In nine of ten patients there was a strong negative correlation between work of breathing and the ventilator-to-patient tidal volume difference (R = -.75 to -.998). CONCLUSIONS:: The ventilator-delivered tidal volume exerts an independent influence on work of breathing during lung-protective ventilation in patients with ALI/ARDS. Patient work of breathing is inversely related to the difference between the ventilator-delivered tidal volume and patient-generated tidal volume during a brief trial of unassisted breathing.     

Thoracocardiography: Noninvasive monitoring of left ventricular stroke volume

Thoracocardiography noninvasively monitors global stroke volume by inductive plethysmographic recording of ventricular volume curves as previously validated by thermodilution. Our purpose was to investigate the potential of thoracocardiography to individually assess stroke volume of the left ventricle. We hypothesized that curves predominantly reflecting left ventricular volume could be obtained by recording waveforms from thoracocardiographic transducers placed at various levels around the chest, and by identifying their origin as the left ventricle if mean expiratory exceeded mean respiratory stroke volumes during spontaneous breathing. Stroke volumes obtained by thoracocardiography in normal subjects were compared beat by beat with estimates derived from simultaneous measurements of left ventricular cavity stroke area by echocardiography with automatic boundary detection. Changes in respiratory variations of stroke volumes were analyzed during spontaneous breathing at fixed rate and tidal volume, during mechanical ventilation, and resistive loaded breathing. In 170 comparisons of beat-by-beat stroke volumes, 89% of thoracocardiographic fell within ±20% of echocardiographic estimates. Changes in tidal volume, resistive loaded breathing, and mechanical ventilation induced respiratory variations of thoracocardiographic derived stroke volumes consistent with the known effect of respiratory changes in intrapleural pressure on left ventricular stroke volumes. The results suggest that thoracocardiography noninvasively tracks changes in left ventricular stroke volumes. Their absolute value may also be monitored if an initial calibration by an independent technique, such as echocardiography, is performed.     

重度肥胖对肺功能及运动试验中呼吸模式的影响

目的：研究重度肥胖对肺胖对肺功能及运动试验中呼吸模式的影响。方法：４２名女性受试者,正常体重组２０名,重度肥胖组２２名,进行肺功能及功率车运动试验测定。结果：肥胖组补呼气量、功能残气量、残气量及肺总量均比对照组显著降低（Ｐ〈０．０５）。肥胖组静息状态、无氧阈状态和极量运动状态的氧耗量均比对照组显著增高（Ｐ〈０．０５）,而公斤氧耗量比对照组显著降低（Ｐ〈０．０１）。无氧阈状态和极量运动状态时,肥胖组     

Hypercapnia in late-phase ALI/ARDS: providing spontaneous breathing using pumpless extracorporeal lung assist

Objective  The fibroproliferative phase of late ALI/ARDS as described by Hudson and Hough (Clin Chest Med 27:671–677, 2006) is associated with pronounced reductions in pulmonary compliance and an accompanying hypercapnia complicating low tidal volume mechanical ventilation. We report the effects of extracorporeal CO₂ removal by means of a novel pumpless extracorporeal lung assist (p-ECLA) on tidal volumes, airway pressures, breathing patterns and sedation management in pneumonia patients during late-phase ARDS. Design  Retrospective analysis. Setting  Fourteen-bed university hospital ICU. Patients  Ten consecutive late-phase ALI/ARDS patients with low pulmonary compliance, and severe hypercapnia. Intervention  Gas exchange, tidal volumes, airway pressures, breathing patterns and sedation requirements before (baseline) and after (2–4 days) initiation of treatment with p-ECLA were analysed. Patients were ventilated in a pressure-controlled mode with PEEP adjusted to pre-defined oxygenation goals. Measurements and main results  Median reduction in pCO₂ was 50% following institution of p-ECLA. Extracorporeal CO₂ removal enabled significant reduction in tidal volumes (to below 4 ml/kg predicted body weight) and inspiratory plateau pressures [30 (28.5/32.3) cmH₂O, median 25, 75% percentiles]. Normalization of pCO₂ levels permitted significant reduction in the dosages of analgesics and sedatives. The proportion of assisted spontaneous breathing increased within 24 h of instituting p-ECLA. Conclusion  Elimination of CO₂ by p-ECLA therapy allowed reduction of ventilator-induced shear stress through ventilation with tidal volumes below 4 ml/kg predicted body weight in pneumonia patients with severely impaired pulmonary compliance during late-phase ARDS. p-ECLA treatment supported control of breathing pattern while sedation requirements were reduced and facilitated the implementation of assisted spontaneous breathing.     

Biofeedback training for reduced respiratory rate in chronic obstructive pulmonary disease: a preliminary study

The overall objective of this preliminary investigation was to determine whether breathing patterns of patients with chronic obstructive pulmonary disease could be altered by training patients to voluntarily change their breathing, using techniques of biofeedback training. The specific aims were (1) to develop a method of monitoring respiratory rate and tidal volume with a device that was both accurate and usable without discomfort or inconvenience to the patient; (2) to use the method with patients having chronic obstructive pulmonary disease to determine whether respiratory rate could be slowed by voluntary controls; and (3) to determine whether patients who could slow their breathing rate would increase their tidal volume and demonstrate other respiratory changes.     

Variations in tidal volume with portable transport ventilators

BACKGROUND: As intra- and interhospital transportation of ventilator-dependent patients has become more commonplace, the number of portable transport ventilators has increased. Transport ventilators should be capable of delivering consistent tidal volume (VT) from breath to breath following changes in lung-thorax compliance and airways resistance. We sought to determine the effect of changes in compliance (C) and resistance (R) on the VT delivered by eight commercially available, time-cycled transport ventilators. METHODS & MATERIALS: Each ventilator (PneuPAC Model 2, Autovent 3000, MAX, Bird Transport Mini-TXP, IC-2A, P7, E100i, and Logic 07a) was connected to a calibrated pneumotachograph and a test lung set for normal adult C (C = 100 mL/cm H2O [1.02 L/kPa]) and R (R = 2 cm H2O.s.L-1 [0.2 kPa.s.L-1]), with VT at 1,000 mL. RESULTS: As C and R were manipulated, VT varied widely. Tidal volume decreased least with the P7 and most with the Bird transport ventilator. CONCLUSION: Decreases in VT with a transport ventilator predispose patients to hypoventilation, hypercapnia, and acidemia. Tidal volume often is not monitored continuously during transport, yet large decreases in VT must not be allowed when pulmonary mechanics are unstable. Internal pressure-limiting valves, venturi flow-generating devices, and compression volume in the breathing circuit are at least three factors that affect VT with transport ventilators.     

体描箱评价脊柱侧弯幼儿的肺功能变化

背景：肺功能检查是脊柱侧弯矫正前评价手术风险的重要手段,寻找一种简便、有效的检测肺功能评估方法是低龄儿童脊柱侧弯手术时机选择及治疗效果评价的迫切要求.目的：应用体描箱评价脊柱侧弯幼儿的肺功能变化.方法：纳入脊柱侧弯患儿31例,健康对照幼儿50例.采用德国耶格公司生产的婴儿体描箱进行肺功能指标检测,包括潮气量、分钟通气量、达峰容积比、达峰时间比、潮气呼气峰流速、25%,50%,75%潮气量时的潮气呼气流速、呼吸频率、功能残气量及有效气道阻力.结果与结论：脊柱侧弯组患儿功能残气量明显低于健康组（P 〈 0.01）,有效气道阻力明显高于健康组（P 〈 0.01）,分钟通气量、潮气呼气峰流速及75%潮气量时的潮气呼气流速均明显低于健康组（P 〈 0.05）.提示功能残气量、有效气道阻力是体描箱测定的经典指标,脊柱侧弯患儿功能残气量明显减低,气道阻力明显增高.体描箱可作为检测低龄脊柱侧弯患儿肺功能的重要手段.     

Measurement of air trapping, intrinsic positive end-expiratory pressure, and dynamic hyperinflation in mechanically ventilated patients

Severe airflow obstruction is a common cause of acute respiratory failure. Dynamic hyperinflation affects tidal ventilation, increases airways resistance, and causes intrinsic positive end-expiratory pressure (auto-PEEP). Most patients with asthma and chronic obstructive pulmonary disease have dynamic hyperinflation and auto-PEEP during mechanical ventilation, which can cause hemodynamic compromise and barotrauma. Auto-PEEP can be identified in passively breathing patients by observation of real-time ventilator flow and pressure graphics. In spontaneously breathing patients, auto-PEEP is measured by simultaneous recordings of esophageal and flow waveforms. The ventilatory pattern should be directed toward minimizing dynamic hyperinflation and auto-PEEP by using small tidal volume and preserving expiratory time. With a spontaneously breathing patient, to reduce the work of breathing and improve patient-ventilator interaction, it is crucial to set an adequate inspiratory flow, inspiratory time, trigger sensitivity, and ventilator-applied PEEP. Ventilator graphics are invaluable for monitoring and treatment decisions at the bedside.     

Influence of an end inspiratory pause on pulmonary ventilation, gas distribution, and lung perfusion during artificial ventilation

Using a constant tidal volume and ventilatory frequency, anesthetized piglets were ventilated with a new tidal volume ventilator. A short inspiratory time without a pause (10% of breathing cycle) was compared with a longer inspiratory time with a pause (33%) both with and without bronchial obstruction. Mechanics of ventilation, pulmonary ventilation, gas exchange, gas distribution, and lung perfusion were measured. The longer inspiratory time with a pause resulted in lower peak airway and end inspiratory pressures and a higher total compliance. Dead space/tidal volume ratio was reduced and the RQ was increased. While the cranial pulmonary fields were less well ventilated, the right caudal field was better ventilated. In the presence of bronchial obstruction, better alveolar ventilation was achieved when an end inspiratory pause was added. The results emphasize the importance of static end inspiratory tracheal conditions although the tidal volumes were kept unchanged.     

A video-based optical system for rapid measurements of chest wall movement

We tested apparatus developed to measure the movement of the surface of the chest and abdomen, during breathing in the supine subject. A line of light is projected onto the chest wall. The line image from a video camera is analysed to estimate of the height of the surface profile, so that the shape and volume of the object can be derived. The data can provide direct or inferential volume estimates. We compared this system with the widely used inferential system of inductance bands in supine volunteers who breathed using patterns designed to emphasize variability in movements: normal and large breaths, and breathing through an expiratory resistance. We calculated the differences between a spirometer signal and continuous volume estimates using the linear regression method, obtained using signals from the two methods. The volume estimate differences obtained by the optical system and induction bands were not significantly different, but the optical system was more precise. Using the optical device, an acceptable interquartile range of differences from spirometric volume (50 ml) was significantly likely when the optical device was used. During resistive loaded breathing (mean tidal volume 390 ml) direct optical measurements of volume, and inductance band estimates, were compared with tidal volume. The optical system showed distortion of the shape of the abdomen during this breathing pattern. Mean error with the optical system was 64 ml and with the inductance band system was 108 ml (p < 0.05). The optical system gives accurate reproducible results in supine human subjects and additional valuable information on shape changes.     

A parametric model of the relationship between EIT and total lung volume

Spirometry and electrical impedance tomography (EIT) data from 26 healthy subjects (14 males, 12 females) were used to develop a model linking contrast variations in EIT difference images to lung volume changes. Eight recordings, each 64 s long, were made for each subject in four postures (standing, sitting, reclining at 45 degrees, supine) and two breathing modes (quiet tidal and deep breathing). Age, gender and five anthropometric variables were recorded. The database was divided into four subsets. The first subset, data from 22 subjects (12 males, 10 females) recorded in deep breathing mode, was used to create the model. Validation was done with the other subsets: data recorded during quiet tidal breathing in the same 22 subjects, and data recorded in both breathing modes for the other four subjects. A quadratic equation in DeltaV(P) (lung volume changes recorded by the spirometer) provided a very good fit to total contrast changes in the EIT images. The model coefficients were found to depend on posture, gender, thoracic circumference and scapular skin fold. To validate the model, the quadratic equation was inverted to estimate lung volume changes from the EIT images. The estimated changes were then compared to the measured volume changes. Validations with each data subset yielded mean standard errors ranging from 9.3% to 12.4%. The proposed model is a first step in enabling inter individual comparisons of EIT images since: (1) it provides a framework for incorporating the effects of anthropometric variables, gender and posture, and (2) it references the images to a physical quantity (volume) verifiable by spirometry.     

Effects of breathing exercises on breathing patterns in obese and non-obese subjects

Chest physiotherapy in connection with abdominal surgery includes different deep-breathing exercises to prevent post-operative pulmonary complications. The therapy is effective in preventing pulmonary complications, especially in high-risk patients such as obese persons. The mechanisms behind the effect is unclear, but part of the effect may be explained by the changes in breathing patterns. The aim of this study was therefore to describe and to analyse the breathing patterns in obese and non-obese subjects during three different breathing techniques frequently used in the treatment of post-operative patients. Twenty-one severely obese [body mass index (BMI) > 40] and 21 non-obese (BMI 19–25) subjects were studied. All persons denied having any lung disease and were non-smokers. The breathing techniques investigated were: deep breaths without any resistance (DB), positive expiratory pressure (PEP) with an airway resistance of approximately +15 cmH₂O (1·5 kPa) during expiration, inspiratory resistance positive expiratory pressure (IR-PEP) with a pressure of approximately –10 cmH₂O (–1·0 kPa) during inspiration. Expiratory resistance as for PEP. Volume against time was monitored while the subjects were sitting in a body plethysmograph. Variables for volume and flow during the breathing cycle were determined. Tidal volume and alveolar ventilation were highest during DB, and peak inspiratory volume was significantly higher than during PEP and IR-PEP in the group of obese subjects. The breathing cycles were prolonged in all techniques but were most prolonged in PEP and IR-PEP. The functional residual capacity (FRC) was significantly lower during DB than during PEP and IR-PEP in the group of obese subjects. FRC as determined within 2 min of finishing each breathing technique was identical to before the breathing manoeuvres.     

Comparative effects of proportional assist and variable pressure support ventilation on lung function and damage in experimental lung injury*

OBJECTIVE:: To investigate the effects of proportional assist ventilation, variable pressure support, and conventional pressure support ventilation on lung function and damage in experimental acute lung injury. DESIGN:: Randomized experimental study. SETTING:: University hospital research facility. SUBJECTS:: Twenty-four juvenile pigs. INTERVENTIONS:: Pigs were anesthetized, intubated, and mechanically ventilated. Acute lung injury was induced by saline lung lavage. After resuming of spontaneous breathing, animals were randomly assigned to 6 hrs of assisted ventilation with pressure support ventilation, proportional assist ventilation, or variable pressure support (n = 8 per group). Mean tidal volume was kept at ≈6 mL/kg in all modes. MEASUREMENTS AND MAIN RESULTS:: Lung functional parameters, distribution of ventilation by electrical impedance tomography, and breathing patterns were analyzed. Histological lung damage and pulmonary inflammatory response were determined postmortem. Variable -pressure support and proportional assist ventilation improved oxygenation and venous admixture compared with pressure support ventilation. Proportional assist ventilation led to higher esophageal pressure time product than variable pressure support and pressure support ventilation, and redistributed ventilation from central to dorsal lung regions compared to pressure support ventilation. Variable pressure support and proportional assist ventilation yielded higher tidal volume variability than pressure support ventilation. Such pattern was deterministic (self-organized) during proportional assist ventilation and stochastic (random) during variable pressure support. Subject-ventilator synchrony as well as pulmonary inflammatory response and damage did not differ among groups. CONCLUSIONS:: In a lung lavage model of acute lung injury, both variable pressure support and proportional assist ventilation increased the variability of tidal volume and improved oxygenation and venous admixture, without influencing subject-ventilator synchrony or affecting lung injury compared with pressure support ventilation. However, variable pressure support yielded less inspiratory effort than proportional assist ventilation at comparable mean tidal volumes of 6 mL/kg.     

Initial mechanical ventilator settings for pediatric patients: clinical judgement in selection of tidal volume

Guidelines for selection of initial mechanical ventilator settings for pediatric patients were evaluated. Protocols specifying tidal volume or peak inspiratory pressure are difficult to apply for infants and children because of leaks at uncuffed endotracheal tubes, compression loss in ventilators, and inaccuracy of settings for intended tidal volume. To avoid these difficulties, the selection of tidal volume was based on subjective clinical observations: visible chest excursion and audible air entry at least simulating normal breathing. In 76 consecutive patients, use of the guidelines resulted in satisfactory PaCO2 for 97% and PaO2 for 89% of infants and children with a wide variety of respiratory disorders. Adequacy of gas exchange was not related to the patient's age, type of ventilator, tightness of fit of the endotracheal tube, or presence of spontaneous breathing. These results support a simple, versatile method of teaching selection of initial mechanical ventilator settings, relying on clinical judgment for regulation of tidal volume.     

Breathing intolerance index: a new indicator for ventilator use

OBJECTIVES: The purpose was to study the efficacy of a proposed breathing intolerance index for justifying ventilator use by patients with pulmonary or chest wall diseases and to compare with values obtained from healthy controls. DESIGN: A total of 42 patients with lung/chest wall disease, including 11 ventilator users and 25 age-matched controls, were studied. The breathing intolerance index was defined as (Ti/Ttot) x (Vt/VC), where Ti = inspiratory time of one breath (in seconds), Ttot = total time of one breath (in seconds), Vt = tidal volume (in milliliters) at rest, and VC = vital capacity (in milliliters). A digital spirometer with custom computer software was used. RESULTS: The examinations were completed uneventfully. The mean breathing intolerance index values of the 25 healthy volunteers, the 31 nonventilator user patients, and the 11 users of nocturnal noninvasive positive-pressure ventilation were 0.050 +/- 0.009 (mean +/- standard deviation), 0.087 +/- 0.022, and 0.186 +/- 0.038, respectively. The breathing intolerance indices of the ventilator users were significantly greater (P < 0.0001) than those of the other nonventilator user groups, and there was no overlap in values. CONCLUSIONS: Ventilator users have a significantly higher breathing intolerance index than nonventilator users. The index may be useful for justifying ventilator use.     

Physiological effects of decannulation in tracheostomized patients

OBJECTIVE: To evaluate the physiological effects of decannulation on breathing patterns and respiratory mechanics by comparing mouth breathing (MB) to tracheal breathing (TB) in tracheostomized patients. DESIGN AND SETTING: Prospective cross-over study in a critical and neuromuscular care unit. PATIENTS AND METHODS: Nine consecutive neuromuscular tracheostomized patients. Flow, esophageal pressure, gastric pressure, expiratory gas, and arterial blood gases were measured during MB and TB. RESULTS: MB induced an increase in tidal volume (from 330+/-60 ml to 400+/-80 ml) without changing respiratory frequency, inspiratory time, or arterial CO(2) pressure. This ventilation increase was due to a significant increase in physiological dead space (from 156+/-67 to 230+/-82 ml) and was associated with significant increases in work of breathing (from 6.9+/-3.4 to 9.1+/-3.3 J/min), transdiaphragmatic pressure swing (from 10+/-4 to 12.5+/-7 cmH(2)O), diaphragmatic pressure-time product per minute (from 214+/-100 to 271+/-92 cmH(2)O s(-1) min(-1)), and oxygen uptake (from 206+/-30 to 229+/-34 ml/min). Upper airway resistance did not differ from in vitro tracheostomy tube resistance. In addition, total lung-airway resistance, dynamic pulmonary compliance, and intrinsic positive end-expiratory pressure were similar in both conditions. CONCLUSIONS: Decannulation resulted in a dead space increase with no other detectable additional loading. It increased work of breathing by more than 30%. Decannulation deserves special attention in patients with restrictive respiratory disease.     

Prediction of post-extubation work of breathing

OBJECTIVE: To evaluate which mode of preextubation ventilatory support most closely approximates the work of breathing performed by spontaneously breathing patients after extubation. DESIGN: Prospective observational design. SETTING: Medical, surgical, and coronary intensive care units in a university hospital. PATIENTS: A total of 22 intubated subjects were recruited when weaned and ready for extubation. INTERVENTIONS: Subjects were ventilated with continuous positive airway pressure at 5 cm H2O, spontaneous ventilation through an endotracheal tube (T piece), and pressure support ventilation at 5 cm H2O in randomized order for 15 mins each. At the end of each interval, we measured pulmonary mechanics including work of breathing reported as work per liter of ventilation, respiratory rate, tidal volume, negative change in esophageal pressure, pressure time product, and the airway occlusion pressure 100 msec after the onset of inspiratory flow, by using a microprocessor-based monitor. Subsequently, subjects were extubated, and measurements of pulmonary mechanics were repeated 15 and 60 mins after extubation. MEASUREMENTS AND MAIN RESULTS: There were no statistical differences between work per liter of ventilation measured during continuous positive airway pressure, T piece, or pressure support ventilation (1.17+/-0.67 joule/L, 1.11+/-0.57 joule/L, and 0.97+/-0.57 joule/L, respectively). However, work per liter of ventilation during all three preextubation modes was significantly lower than work measured 15 and 60 mins after extubation (p < .05). Tidal volume during pressure support ventilation and continuous positive airway pressure (0.46+/-0.11 L and 0.44+/-0.11 L, respectively) were significantly greater than tidal volume during both T-piece breathing and spontaneous breathing 15 mins after extubation (p < .05). Negative change in esophageal pressure, the airway occlusion pressure 100 msec after the onset of inspiratory flow, and pressure time product were significantly higher after extubation than during any of the three preextubation modes (p < .05). CONCLUSIONS: Work per liter of ventilation, negative change in esophageal pressure, the airway occlusion pressure 100 msec after the onset of inspiratory flow, and pressure time product all significantly increase postextubation. Tidal volume during continuous positive airway pressure or pressure support ventilation overestimates postextubation tidal volume.     

Ventilatory responses to exercise and to carbon dioxide in mitral stenosis before and after valvulotomy: causes of tachypnoea

1. The ventilation and cardiac frequency during progressive exercise and the respiratory responses to breathing carbon dioxide have been measured in 33 female patients with mitral stenosis and in 31 control subjects. Compared with the control subjects, the patients' exercise ventilation and cardiac frequency were increased; the exercise tidal volume at standard minute volume, the vital capacity and the ventilatory response to carbon dioxide were reduced. The extent to which the standardized tidal volume was lower during exercise than during breathing carbon dioxide was correlated with the severity of the stenosis, as gauged by the increase in exercise cardiac frequency above the level predicted from anthropometric measurements. 2. Twenty patients were studied postoperatively. In the 12 who showed clinical improvement the exercise ventilation and cardiac frequency were reduced and the exercise tidal volume at a given minute ventilation was increased. The latter change occurred despite a reduction in vital capacity, which was probably a residual effect of thoractomy. There was no significant change in the response to breathing carbon dioxide. No material change in function was observed in the patients whose condition was not improved by the operation. 3. It is suggested that in mitral stenosis the tachypnoea which occurs during exercise, whilst mainly a mechanical consequence of the reduced vital capacity, is also partly due to pulmonary congestion stimulating intrapulmonary receptors.     

Upper extremity muscle tone and response of tidal volume during manually assisted breathing for patients requiring prolonged mechanical ventilation

[Purpose] The aim of the present study was to examine, in patients requiring prolonged mechanical ventilation, if the response of tidal volume during manually assisted breathing is dependent upon both upper extremity muscle tone and the pressure intensity of manually assisted breathing. [Subjects] We recruited 13 patients on prolonged mechanical ventilation, and assessed their upper extremity muscle tone using the modified Ashworth scale (MAS). The subjects were assigned to either the low MAS group (MAS≤2, n=7) or the high MAS group (MAS≥3, n=6). [Methods] The manually assisted breathing technique was applied at a pressure of 2 kgf and 4 kgf. A split-plot ANOVA was performed to compare the tidal volume of each pressure during manually assisted breathing between the low and the high MAS groups. [Results] Statistical analysis showed there were main effects of the upper extremity muscle tone and the pressure intensity of the manually assisted breathing technique. There was no interaction between these factors. [Conclusion] Our findings reveal that the tidal volume during the manually assisted breathing technique for patients with prolonged mechanical ventilation depends upon the patient’s upper extremity muscle tone and the pressure intensity.Key words: Manually assisted breathing, Muscle tone, Prolonged mechanical ventilation