Nasal positive pressure ventilation in patients with acute respiratory failure. Difficult and time-consuming procedure for nurses

Intubation and mechanical ventilation are well-established techniques in the management of patients with acute respiratory failure; however, there are situations in which these procedures cannot be used safely for various reasons. A recently described noninvasive technique, nasal positive-pressure ventilation (NPPV), has been developed for home ventilation of certain patients with chronic ventilatory insufficiency. We hypothesized that NPPV could be used in selected patients in whom intubation and mechanical ventilation were clearly indicated, but not immediately possible, or even contraindicated. Six patients were treated with NPPV during an episode of acute respiratory failure and enrolled in a prospective study. We found that NPPV was successful in avoiding intubation, but only in the three patients suffering from a restrictive pulmonary disorder, whereas the procedure was unsuccessful in patients with obstructive disorders. Moreover, in every patient, acute NPPV was very time-consuming for the nursing staff: in patients with restrictive disorders, a nurse had to monitor a patient submitted to NPPV during 41 +/- 9 percent of the duration of ventilation and during 91 +/- 9 percent of the NPPV time in patients with obstructive disorders. We conclude that acute NPPV may be attempted in selected patients with acute respiratory failure, predominantly patients with restrictive respiratory disorders, but that this procedure is very time-consuming for nurses.     

无创正压通气不同呼气末正压水平对慢性阻塞性肺疾病急性加重患者呼吸做功的影响

目的 探讨无创正压通气(NPPV)不同呼气末正压水平对慢性阻塞性肺疾病急性加重(AECOPD)患者的呼吸做功影响.方法 12例AECOPD患者接受相同压力支持和不同呼气末正压水平的NPPV,观察患者吸气肌肉用力和呼吸方式的变化.结果 ①与自主呼吸(SB)相比,4 cm H2O(L-PEEP)、6 cm H2O(PEEP...     

慢性阻塞性肺疾病急性发作期患者对比例辅助通气的生理反应

目的　探讨比例辅助通气 (PAV)不同辅助水平对慢性阻塞性肺疾病 (COPD)急性发作期患者生理反应的影响。方法　 9例COPD急性发作期患者接受三个不同比例辅助水平的PAV通气 ,观察患者吸气肌肉用力情况和呼吸方式的变化。结果　 (1)与自主呼吸 (SB)相比 ,PAV各辅助水平时的潮气量 (VT)、分钟通气量 (V·E)和呼吸频率 (RR)均稍增高 (P >0 0 5 )。各比例辅助水平之间的VT、V·E 和RR比较差异无显著性 (P >0 0 5 )。 (2 )与SB相比 ,各比例辅助水平时的跨膈压 (Pdi)、压力时间乘积 (PTP)和患者呼吸做功均明显减少 (P >0 0 1) ,Pdi、PTP和患者呼吸做功分别平均减少 8 36cmH2 O、11 4 9cmH2 O·s-1·L-1和 0 5 3J/L。随比例辅助水平的升高 ,Pdi、PTP和患者呼吸功无明显变化(P >0 0 5 )。 (3)PAV可减轻患者呼吸困难 (P <0 0 5 )。结论　本试验证实了无创PAV在COPD急性发作期患者中应用的可行性。患者感觉最舒适的PAV辅助比例水平是 (5 7± 11) %。根据患者感觉舒适情况而设定比例辅助水平的无创PAV可减轻患者的呼吸肌肉负担 ,最舒适水平时呼吸功减少5 7% ,Pdi减少 72 % ,PTP减少 6 5 % ;并改善患者的呼吸方式和呼吸困难     

Respiratory muscle fatigue limiting physical exercise?

Inspiratory muscle fatigue has been documented during loaded breathing or acute respiratory failure, but its role in exercise limitation is still undetermined. Electromyographic (EMG) signs of diaphragmatic fatigue develop in normal subjects hyperventilating above 70% of maximal voluntary ventilation (MVV), a ventilatory level commonly attained at peak exercise. EMG signs of diaphragmatic fatigue also occur during high power cycling exercise in normal subjects and chronic obstructive pulmonary disease (COPD) patients. However, a loss of respiratory muscle strength has rarely been documented following strenuous physical exercise with techniques independent of the subjects' collaboration. Prior inspiratory muscle fatigue decreases exercise tolerance in normal subjects but its effect is largely unknown in COPD patients. Respiratory muscle rest by negative pressure ventilation was reported to improve exercise tolerance in COPD, but this beneficial effect was not confirmed by controlled studies. The effect of inspiratory muscle training on exercise tolerance is still undefined by existing data, in part because of differences in methods and selection criteria between studies. Although respiratory muscle fatigue may occur during exercise, it is not clearly established whether interventions directed at respiratory muscles may improve exercise tolerance in COPD.     

Update: Non-Invasive Positive Pressure Ventilation in Chronic Respiratory Failure Due to COPD

Long-term non-invasive positive pressure ventilation (NPPV) has widely been accepted to treat chronic hypercapnic respiratory failure arising from different etiologies. Although the survival benefits provided by long-term NPPV in individuals with restrictive thoracic disorders or stable, slowly-progressing neuromuscular disorders are overwhelming, the benefits provided by long-term NPPV in patients with chronic obstructive pulmonary disease (COPD) remain under question, due to a lack of convincing evidence in the literature. In addition, long-term NPPV reportedly failed in the classic trials to improve important physiological parameters such as arterial blood gases, which might serve as an explanation as to why long-term NPPV has not been shown to substantially impact on survival. However, high intensity NPPV (HI-NPPV) using controlled NPPV with the highest possible inspiratory pressures tolerated by the patient has recently been described as a new and promising approach that is well-tolerated and is also capable of improving important physiological parameters such as arterial blood gases and lung function. This clearly contrasts with the conventional approach of low-intensity NPPV (LI-NPPV) that uses considerably lower inspiratory pressures with assisted forms of NPPV. Importantly, HI-NPPV was very recently shown to be superior to LI-NPPV in terms of improved overnight blood gases, and was also better tolerated than LI-NPPV. Furthermore, HI-NPPV, but not LI-NPPV, improved dyspnea, lung function and disease-specific aspects of health-related quality of life. A recent study showed that long-term treatment with NPPV with increased ventilatory pressures that reduced hypercapnia was associated with significant and sustained improvements in overall mortality. Thus, long-term NPPV seems to offer important benefits in this patient group, but the treatment success might be dependent on effective ventilatory strategies.     

Influence of noninvasive positive pressure ventilation on inspiratory muscles

Intermittent positive pressure ventilation reduces inspiratory muscle electromyographic activity among patients with restrictive ventilatory failure. It has therefore been suggested that the reduction of energy expenditure at night could result in improved inspiratory muscle function during the day. Reported successes with nocturnal ventilation have not included measurements of inspiratory muscle endurance. We therefore electively ventilated six (five female, one male) patients (mean +/- SD) aged 36 +/- 13 years in whom respiratory failure (room air PaCO2, 60 +/- 13 mm Hg; PaO2, 44 +/- 11 mm Hg; SaO2, 75 +/- 12 percent) was consequent on restrictive ventilatory disease (vital capacity, 25 +/- 7 percent predicted; FEV1/FVC, 81 +/- 12 percent; total lung capacity, 40 +/- 5 percent predicted; MIPRV -42 +/- 10 cm H2O; MEP, 81 +/- 28 cm H2O). Positive pressure ventilation was administered with a customized closely fitting nasal mask attached to a volume-cycled pressure-limited ventilator. Full respiratory polysomnographic measurements as well as arterial blood gases, pulmonary function, distance walked in six minutes, and inspiratory muscle endurance were measured at baseline and after 3 and 14 months of ventilation. Ventilation improved saturation (baseline on O2; SWS 87 +/- 10, REM 79 +/- 14, ventilator on R/A; SWS 90 +/- 6, REM 89 +/- 5 percent) and transcutaneous Pco2 (baseline on O2; SWS 85 +/- 26, REM 94 +/- 39, ventilator on R/A; SWS 53 +/- 9, REM 58 +/- 9 mm Hg). During ventilation, the quantity and distribution of sleep was similar to that observed prior to ventilation. Daytime gas exchange improved as did the six-minute walking test (initial test = 429 +/- 120 m, three months after ventilation = 567 +/- 121 m), both of these improvements being sustained at 14 months. Inspiratory muscle endurance measured using a pressure threshold load (mean mouth pressure = 45 percent MIPRV) improved from 7.1 +/- 3.4 minutes at baseline to 14.8 +/- 7.6 minutes at 3 months, an improvement sustained at 14 months. There was no change in measured lung volumes or respiratory muscle strength. We conclude that the improvement in nocturnal gas exchange, daytime functioning, and arterial blood gases resulting from nocturnal positive pressure ventilation is associated with an increase in inspiratory muscle endurance sustained at 14 months.     

Weaning from mechanical ventilation by long-term nasal positive pressure ventilation in two patients with acute respiratory distress syndrome associated with pneumococcal sepsis

Only few data concerning weaning by nasal positive pressure ventilation (NPPV) are available, and successful weaning by using NPPV in patients with acute respiratory distress syndrome (ARDS) and severe complications has not yet been described. Two cases with ARDS and both preexisting thoracopulmonary disease (infundibulum abnormality and suspected COPD) and associated complications (recurrent sepsis, acute renal failure, need for lobectomy, severe malnutrition) could not be weaned by invasive ventilatory techniques. Both patients presented with rapid shallow breathing and PaCO(2) values >60 mm Hg during intermittent trials of spontaneous breathing, although the primary pathology and associated complications had been resolved. Patients were successfully adapted on NPPV in a stepwise approach after 93 days and 67 days of invasive ventilation. In one patient withdrawal from NPPV was possible after 2 months. In the other patient the duration of daily ventilation could be significantly reduced from 18 to 6 h/day after 9 months on NPPV. Therefore, patients with ARDS who cannot be weaned by invasive ventilatory strategies might be removed successfully from invasive mechanical ventilation by using NPPV even when there are preexisting thoracopulmonary disease and major complications during invasive ventilation.     

Respiratory muscle dysfunction secondary to chronic tracheostomy tube placement

In patients requiring periodic mechanical ventilation, a deflated, fenestrated tracheostomy tube may impair respiratory muscle performance during spontaneous breathing. We describe a patient with severe chronic airflow obstruction (CAO) whose respiratory muscle performance and exercise duration improved after tracheostomy tube removal. Duty cycle, Pdi/Pdi max, and the tension time index were all lower during exercise after tracheostomy tube removal. We conclude that a deflated and fenestrated tracheostomy tube significantly increases airways resistance and can further limit ventilatory muscle performance in patients with airflow obstruction. Patients requiring intermittent ventilatory support may benefit from permanent tracheostomy fistulas that allow for intermittent self cannulation. This would avoid loading of the respiratory muscles when breathing spontaneously.     

Short-term effect of nasal intermittent positive-pressure ventilation in patients with restrictive thoracic disease

BACKGROUND: The use of nasal intermittent positive pressure ventilation (NIPPV) would be expected to ameliorate dyspnea, ventilatory capacity and exercise tolerance durability in individuals with hypercapnic respiratory failure secondary to restrictive thoracic disease. OBJECTIVES: The purpose of this study was to determine the short-term effect of NIPPV on respiratory muscle endurance, exercise capacity and respiratory functions in patients with chronic respiratory failure due to restrictive thoracic disease. METHODS: Twelve patients with chronic ventilatory failure due to restrictive thoracic disease underwent nasal bilevel positive airway pressure (BiPAP) ventilation for 2 h a day during 15 consecutive days. The effects were assessed by spirometry, arterial blood gas analysis, 6-min walking test, sensation of dyspnea according to the American Thoracic Society dyspnea scoring scales (ATS) and surface electromyogram of the diaphragm (EMGdi) before and after the study (on day 15). RESULTS: Nasal BiPAP reduced the ATS dyspnea score from 2.5 +/- 0.9 to 1.6 +/- 0.4 (p < 0.01). Distances walked in 6 min increased from 320.66 +/- 93.56 to 382.41 +/- 121.20 m (p < 0.05). Comparison of baseline with levels after nasal BiPAP ventilation showed a statistically significant improvement in PaCO(2) (p < 0.05). Forced vital capacity increased from 35 to 50% of the predicted value (p < 0.01). There were no statistically significant reductions in the amplitude of EMGdi after the therapy. CONCLUSION: These results indicate that NIPPV delivered via nasal BiPAP improves respiratory functions, exercise capacity, and reduces dyspnea in the short term in patients with chronic respiratory failure due to restrictive thoracic disease. Whether such short-term improvements can be sustained merits further study.     

无创正压通气治疗慢性阻塞性肺疾病急性呼吸衰竭

无创正压通气已经广泛用于慢性阻塞性肺疾病急性加重期的治疗,主要适应证包括呼吸增快、动脉氧分压下降、二氧化碳分压升高和呼吸性酸中毒,颜面部畸形、严重意识障碍、呼吸心跳停止以及血流动力学不稳定是其主要禁忌证。无创正压通气能够减轻呼吸肌负荷、减轻呼吸肌疲劳,具有降低患者病死率和气管插管率的作用。无创正压通气治疗时给予足够的压力支持和治疗时间是取得治疗效果的重要保证。     

Normocapnia during nIPPV in chronic hypercapnic COPD reduces subsequent spontaneous PaCO2

Hypercapnia has been accepted during nasal intermittent positive pressure ventilation (nIPPV) and during subsequent spontaneous breathing in patients with chronic hypercapnic respiratory failure (HRF) due to COPD. We tested the hypothesis that nIPPV aimed at normalizing PaCO2 will reduce PaCO2 during subsequent spontaneous breathing. For that purpose 14 consecutive inpatients (age 61.4 +/- 9.9 years) with chronic HRF due to COPD were established on passive pressure-controlled nIPPV in a stepwise approach. Assisted ventilation with supplemental oxygen to reach normoxemia was started followed by passive ventilation with a stepwise increment in the inspiratory pressure and finally by a stepwise increase in the respiratory rate to establish normocapnia. Baseline pulmonary function parameters were: FEV1 0.97 +/- 0.43 l, PaCO2 59.5 +/- 8.4 mmHg, PaO2 49.9 +/- 7.8 mmHg, HCO3- 35.6 +/- 5.2 mmol/l, pH 7.39 +/- 0.04. Normoxemia as well as normocapnia was thus established by decreasing PaCO2 by 19.5 +/- 7.0 mmHg during nIPPV within 8.8 +/- 3.8 days (P < 0.001) (inspiratory pressure 29.8 +/- 3.8 mmHg, respiratory rate 22.9 +/- 1.9 BPM). Spontaneous PaCO2 measured 4 h after cessation of nIPPV decreased to 46.0 +/- 5.5 mmHg (P < 0.001), and HCO3- decreased to 27.2 +/- 3.0 mmol/l (P < 0.001). At 6 months of follow-up, II patients continued nIPPV with stable blood gases and with a decrease of P0.1/Plmax from 9.4 +/- 4.3% to 5.9 +/- 2.0% (P < 0.005). In conclusion, normalization of PaCO2 by passive nIPPV in patients with HRF due to COPD is possible and leads to a significant reduction of PaCO2 during subsequent spontaneous breathing and is associated with improved parameters of respiratory muscle function.     

Noninvasive Positive Pressure Ventilation in Acute Respiratory Failure of Chronic Obstructive Pulmonary Disease

Noninvasive positive pressure ventilation (NPPV) has reemerged as an effective strategy for reducing morbidity and mortality associated with acute exacerbations of chronic obstructive pulmonary disease (COPD). During acute respiratory failure, dynamic hyperinflation, intrinsic PEEP, and increased airway resistance result in a mechanical workload that exceeds inspiratory muscle capacity. NPPV provides augmentation of alveolar ventilation and respiratory muscle rest. Observational, cohort, and, more recently, randomized controlled trials have demonstrated the ability of NPPV to decrease the need for endotracheal intubation and decrease complications and mortality. NPPV performs better in COPD patients without significant comorbid illness. It should be initiated during COPD exacerbations if arterial pH is less than 7.35 or if the patient is severely distressed. Pressure support ventilation (10–20 cmH₂O) via face mask is likely the optimal technique and, when successful, results in rapid clinical improvement. Accepted for publication: 17 October 1996     

Impact of ventilation parameters and duration of ventilator use on non-invasive home ventilation in restrictive thoracic disorders

BACKGROUND: Non-invasive positive pressure ventilation (NPPV) is an accepted treatment option for chronic ventilatory failure due to restrictive thoracic disorders. OBJECTIVE: The impact of ventilation setting and the duration of ventilator use on changes in physiological and functional parameters has not yet been evaluated. METHODS: Effects of NPPV on body plethysmographic parameters, blood gas tension and inspiratory muscle function up to 12 months were analyzed in 44 patients with thoracic cage abnormalities in a clinical stable condition. Furthermore, the influence of ventilator parameters and the duration of ventilator use on these changes was determined. RESULTS: A significant improvement in blood gas parameters (PaCO(2), PaO(2) and base excess; p < 0.001), lung volumes (VC, TLC and FEV(1); p < 0.001) and inspiratory muscle function (PI(max), P(0.1); p < 0.01 and p < 0.05) was found after 3.8 +/- 0.8 months of treatment. As shown by a subgroup analysis, changes were already achieved within the first 3 months of NPPV and then remained stable over time. Improvements in VC were positively correlated with IPAP (r = 0.55; p < 0.001). Reduction in PaCO(2) was positively correlated with the quotient (IPAP - EPAP)/weight (r = 0.55; p < 0.001). No correlation could be detected between changes in functional parameters and the duration of ventilator use. CONCLUSIONS: NPPV can improve blood gas parameters, lung volume and inspiratory muscle function in thoracic restrictive disorders. To best utilize the potential of NPPV treatment, it seems to be more effective to optimize pressure levels than to extend the duration of ventilation.     

Long-term reduction of hyperinflation in stable COPD by non-invasive nocturnal home ventilation

OBJECTIVE: The role of non-invasive positive pressure ventilation (NPPV) in stable COPD with chronic ventilatory failure remains controversial. The impact of long-term home nocturnal NPPV treatment on deflation has not yet been evaluated in detail. METHODS: Retrospective explorative study of 46 patients with stable COPD undergoing NPPV treatment. Effects of NPPV on body plethysmographic parameters, blood gas tensions and inspiratory muscle function after 6.2 (+/-1.7) and 12.7 (+/-2.1) months of treatment. Further, evaluation of 1-year survival, compliance and ventilation parameters. RESULTS: One-year survival was 89.1%. The effectiveness of ventilation was proven by a significant reduction in nocturnal and daytime PaCO2. We observed a decrease in the ratio of residual volume (RV) to total lung capacity (TLC) on the average of 5.2+/-9.8% (or 15.2+/-29.7% pred.; P<0.01) at six and 3.9+/-9.0% (or 12.9+/-18.6% pred.; P<0.001) at 12 months. As a consequence, we found significant improvements in inspiratory capacity (IC), vital capacity (VC) and forced expiratory volume in one second (FEV1). For patients with the most severe hyperinflation (RV/TLC>75%), we found a significant positive correlation between inspiratory positive airway pressure (IPAP) and reductions in PaCO2 (r=0.56; P<0.05) and RV/TLC (r=0.50; P<0.05). CONCLUSIONS: In severe hypercapnic stable COPD long-term nocturnal NPPV can reduce hyperinflation with sustained improved daytime blood gas parameters.     

Respiratory muscle insufficiency in acute respiratory failure of subjects with severe COPD: treatment with intermittent negative pressure ventilation

Nine subjects with severe chronic obstructive pulmonary disease (COPD) in acute respiratory failure (ARF) and with marked weakness of the respiratory muscles (Group A) underwent intermittent negative pressure ventilation by means of an iron lung (8 h daily for 7 days). Seven subjects with COPD in stabilized chronic respiratory failure (Group B) were studied as controls and submitted to the same medical therapy without ventilator treatment. Functional respiratory tests were performed before and after 7 days of treatment. After ventilatory treatment, Group A showed an increase of maximum inspiratory pressure (PImax), maximum expiratory pressure (PEmax), vital capacity (VC), arterial oxygen tension (PaO2), pH and a decrease of residual volume (RV), total lung capacity of (TLC) and arterial carbon dioxide tension (PaCO2) (all statistically significant). No improvement was ascertained in the functional parameters of Group B. The expiratory muscles seem to play a determining role in ARF. We conclude that the iron lung is a useful therapeutic defence in removing muscular fatigue and in restoring a good level of respiratory compensation of ARF in severe COPD.     

Noninvasive ventilation for acute respiratory failure: a prospective randomised placebo-controlled trial.

The aim of the present study was to clarify whether the known effects of noninvasive positive-pressure ventilation (NPPV) in patients with respiratory failure are real or due to placebo effects and whether early application of NPPV in the emergency department leads to rapid improvement of the patients condition and outcome. A prospective randomised placebo-controlled study was conducted in 20 patients with severe acute respiratory failure (ARF) secondary to an acute exacerbation of chronic obstructive pulmonary disease (COPD) or acute pulmonary oedema, not improving under conventional medical therapy and on the edge of intubation. Patients received either conventional medical therapy plus two-level NPPV (hi-level NPPV) or conventional medical therapy plus "placebo" NPPV. The main outcome measures involved the need for endotracheal intubation in the bi-level NPPV arm and in the placebo arm after crossing over to active NPPV. Morbidity, length of stay, mortality and the effect of the ventilatory mode on clinical, arterial-blood gas parameters, and the sternocleidomastoid muscles electromyogram (EMG) activity were also measured. The 10 patients in the active NPPV group rapidly improved and none needed intubation. Placebo NPPV resulted in no change in the clinical condition of patients that continued to worsen and the 10 patients were crossed over to active NPPV. Three patients were intubated. No differences in terms of morbidity, length of stay or mortality between the two groups were observed. Active NPPV (but not placebo NPPV) led to a rapid and significant improvement in the clinical parameters, pH and the carbon dioxide tension in arterial blood and to a decrease in respiratory frequency and sternocleidomastoid EMG activity. Early application of bi-level noninvasive positive-pressure ventilation in patients with severe acute respiratory failure, due to chronic obstructive pulmonary disease and acute pulmonary oedema, leads to a rapid improvement in clinical status and blood gases. Noninvasive positive-pressure ventilation had no placebo effect.     

Respiratory sensation in chronic obstructive pulmonary disease

Previous work has demonstrated that the perception of added resistive loads is blunted in patients with chronic obstructive pulmonary disease (COPD). It is not clear, however, whether this is due to reduced levels of respiratory muscle force during loaded breathing or to a specific abnormality in respiratory sensation. In the present study, the psychophysical technique of magnitude scaling was used to evaluate the sensation of external resistive and elastic ventilatory loads as well as the perception of inspired volume and inspiratory muscle force in 14 patients with COPD and in 12 normal subjects of similar age. The exponents of the power function relationships between load magnitude and sensation intensity for both resistive and elastic loads were significantly reduced in the patients with COPD compared with those in the normal subjects. While breathing against any given ventilatory load, the peak inspiratory mouth pressure and inspiratory duration were comparable in the 2 groups. Thus, the exponents of the power function relationships between peak inspiratory mouth pressure and sensation intensity were significantly lower in the patients with COPD (0.92 +/- SE 0.17 and 0.96 +/- SE 0.17 for resistive and elastic loads, respectively) compared with those obtained in the normal subjects (1.47 +/- SE 0.12 for resistive loads and 1.52 +/- SE 0.17 for elastic loads) (p less than 0.05). In contrast, the perception of inspired volume and of respiratory muscle force during static inspiratory maneuvers as determined by magnitude estimation and production were no different in either group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Diaphragmatic energy expenditure in chronic respiratory failure. The effect of assisted ventilation with body respirators.

Patients with chronic respiratory failure secondary to disorders which increase the work of breathing often benefit from assisted ventilation with body respirators. To test the hypothesis that body respirator therapy works by relieving the respiratory muscles of an excessive load, we recorded diaphragmatic and/or accessory inspiratory muscle electrical activity before and during assisted ventilation in 11 patients. All patients had chronic hypercapnia; seven had advanced obstructive pulmonary disease and four had severe thoracic cage restriction.     

Effect of varying the pressurisation rate during noninvasive pressure support ventilation.

The aim of the study was to assess the effects of varying the pressurisation rate during noninvasive pressure support ventilation on patients' breathing pattern, inspiratory effort, arterial blood gases, tolerance to ventilation and amount of air leakage. A total of 15 chronic obstructive pulmonary disease patients recovering from an acute episode of hypercapnic acute respiratory failure were studied during four randomised trials with different levels of pressurisation rate. No significant changes were observed in breathing pattern and arterial blood gases between the different runs. The pressure time product of the diaphragm, an estimate of its metabolic consumption, was significantly lower with all pressurisation rates than with spontaneous breathing, but was significantly lowest with the fastest rate. However, air leak, assessed by the ratio between expired and inspired tidal volumes, increased and the patients' tolerance of ventilation, measured using a standardised scale, was significantly poorer with the fastest pressurisation rate. In chronic obstructive pulmonary disease patients recovering from an episode of acute hypercapnic respiratory failure and ventilated with noninvasive pressure support ventilation, different pressurisation rates resulted in different reductions in the pressure time product of the diaphragm; this reduction was greater with the fastest rate, but was accompanied by significant air leaks and poor tolerance.