Continuous positive airway pressure ventilation for respiratory failure associated with Pneumocystis carinii pneumonia

The value of continuous positive airway pressure (CPAP) ventilation via a tight fitting face mask was assessed in eight HIV-1 antibody-positive patients with Pneumocystis carinii pneumonia who were in hypoxaemic respiratory failure. All patients were conscious, able to protect their airway and not hypercapnic. Treatment was effective in seven patients. Prior to CPAP, mean (range) arterial oxygen tension was 6.7 (4.7-10.5) kPa in seven patients breathing oxygen via a face mask (FiO2 = 0.6), 6.1 kPa in one patient breathing room air and rose to 9.9 (6.8-12.8) kPa with CPAP (FiO2 = 0.6 and PEEP = 1.3 kPa in six patients and 2.6 kPa in one patient); the mean increase in PaO2 was 3.1 kPa (P less than 0.02). These seven patients experienced a rapid reduction in dyspnoea and their respiratory rate fell from a mean of 40 breaths min-1 to 32 breaths min-1 (P less than 0.001). One patient deteriorated rapidly on CPAP and died: no other complications were seen with this technique. CPAP was continued for a mean of 4.5 days and the seven responders all survived the episode of P. carinii pneumonia. We conclude that mask CPAP provides an effective means of improving oxygenation in severely hypoxaemic patients with P. carinii pneumonia.     

Continuous positive airway pressure and supplemental oxygen in the treatment of cardiogenic pulmonary edema

The efficacy of continuous positive airway pressure (CPAP) administered with a face mask was compared to oxygen supplementation in 40 patients with acute cardiogenic pulmonary edema. Baseline arterial blood gas values and pH, heart rate, respiratory rate, and blood pressure were recorded after patients breathed 28 percent oxygen with an ambient airway pressure for ten minutes. Thereafter, inspired oxygen concentration (FIO2) was increased by 0.10 and airway pressure was increased by 10 cm H2O in random sequence. Cardiopulmonary function was reassessed after a five-minute stabilization period at each level of oxygen supplementation and airway pressure. An increase in FIO2 and the application of CPAP both produced significant elevation in arterial blood oxygen tension. Use of CPAP was consistently associated with a decrease in respiratory rate, blood pressure, and rate pressure product, which were not observed with a mere enhancement of oxygen therapy. The improvement in the measured cardiopulmonary variables associated with CPAP therapy cannot be achieved by reversing hypoxemia with supplemental oxygen only.     

Non-invasive pressure support ventilation in patients with respiratory failure due to severe acute cardiogenic pulmonary edema

BACKGROUND: Recent studies suggest the use of non-invasive pressure support ventilation (NIPSV) in patients with acute cardiogenic pulmonary edema (ACPE). However, it remains unclear whether all patients with ACPE benefit from NIPSV. OBJECTIVES: To investigate short-term effects of NIPSV on respiratory, hemodynamic and oxygenation parameters in patients with respiratory failure due to severe ACPE and to identify factors predicting the need for intubation and in-hospital mortality. METHODS: In a prospective, uncontrolled, open study, 28 patients admitted with signs and symptoms of severe respiratory distress due to ACPE were given NIPSV in addition to standardized pharmacological treatment. Physiological parameters were obtained before and after NIPSV, and intubation rate and in-hospital mortality were recorded. RESULTS: NIPSV increased arterial oxygenation from paO2 54.2 +/- 12.4 to 76.9 +/- 12.6 mm Hg (p = 0.0001) and decreased respiratory frequency from 40.1 +/- 8.2 to 22.4 +/- 4.9 breaths/min (p = 0.0001). Significant improvements were also noted for heart rate, blood pressure and the paO2/FiO2 ratio. Four patients (14%) required intubation despite NIPSV. Patients who required intubation had lower paCO2 levels (p = 0.0002), lower serum bicarbonate concentrations (p = 0.04) and lower systolic blood pressure (p = 0.045) than patients who were successfully treated with NIPSV. Eight patients (28.5%) died during hospitalization. In patients with a paCO2 < or =35 mm Hg on admission, the in-hospital mortality was 87%, but in patients with a paCO2 >35 mm Hg the in-hospital mortality was 6%. CONCLUSIONS: NIPSV improves oxygenation and alleviates respiratory distress in patients with respiratory failure due to severe ACPE. However, a subgroup of patients with hypocapnia on admission might have a poor prognosis, with a higher risk of intubation and in-hospital mortality.     

Does continuous positive airway pressure by face mask improve patients with acute cardiogenic pulmonary edema due to left ventricular diastolic dysfunction?

OBJECTIVE: Continuous positive airway pressure (CPAP) by face mask is an effective method of treating severe cardiogenic pulmonary edema (CPE). However, to our knowledge, no study has provided a precise evaluation of the effects of CPAP on cardiac function in patients presenting with CPE and preserved left ventricular (LV) function. DESIGN: Prospective observational clinical study. SETTING: A 14-bed, medical ICU at a university hospital. PATIENTS: Nine consecutive patients presenting with hypoxemic acute CPE. INTERVENTIONS: All patients were selected for 30 min of CPAP with 10 cm H(2)O by mask with fraction of inspired oxygen adjusted for a cutaneous saturation > 90%. Doppler echocardiography was performed before CPAP application and during the last 10 min of breathing with CPAP. Two-tailed, paired t-tests were used to compare data recorded at baseline (oxygen alone) and after CPAP. MEASUREMENTS AND RESULTS: Four patients presented CPE with preserved left ventricular (LV) function (a preserved LV ejection fraction [LVEF] > 45%, and/or aortic velocity time integral > 17 cm in the absence of aortic stenosis or hypertrophic cardiomyopathy). Oxygenation and ventilatory parameters were improved by CPAP in all patients. Hemodynamic monitoring and Doppler echocardiographic analysis demonstrated that in patients with preserved LV systolic function, mean arterial pressure and LV end-diastolic volume were decreased significantly by CPAP (p < 0.04). In patients with LV systolic dysfunction, CPAP improved LVEF (p < 0.05) and decreased LV end-diastolic volume (p = 0.001) significantly. CONCLUSION: CPAP improves oxygenation and ventilatory parameters in all kinds of CPE. In patients with preserved LV contractility, the hemodynamic benefit of CPAP results from a decrease in LV end-diastolic volume (preload).     

无创正压机械通气辅助治疗急性心源性肺水肿的效果

目的评价无创正压机械通气辅助治疗急性心源性肺水肿的疗效。方法选择27例急性心源性肺水肿患者．在高流量吸氧及常规药物治疗不能纠正缺氧时,经面罩给予无创正压通气,观察使用无创正压机械通气治疗前、治疗后其临床症状、心率、呼吸、血氧饱和度和动脉血气分析的变化。结果经面罩无创正压通气治疗后,27例患者中20例（74．07％）临床症状、体征明显改善,血气分析中氧气分压明显升高,与通气前比较,差异有统计学意义[（90．08±15．39）mmHg＇US．（53．12±17．65）mmHg,P〈0．05];二氧化碳分压下降,与通气前比较,差异有统计学意义[（14．52±20．52）mmHgVS．（55．47±23．82）mmHg,P〈0．05]。7例（25．93％）经无创正压通气治疗无效,改为经口气管插管机械通气,2例死亡。结论应用无创正压通气可明显改善急性心源性肺水肿患者的症状、体征和血气分析结果,可作为急性心源性肺水肿安全、快速、有效的辅助治疗手段之一。     

Acute myocardial infarction complicated by left ventricular dysfunction and respiratory failure. The effects of continuous positive airway pressure

The cardiopulmonary effects of continuous positive airway pressure (CPAP) were studied in 14 patients with acute myocardial infarction complicated by circulatory and respiratory failure. Cardiac performance, lung mechanics, and gas exchange were assessed during 50 percent mechanical ventilatory support at end-expiratory airway pressure levels of 0, 5, 10, and 15 mm Hg. The increase in airway pressure resulted in significantly improved arterial blood oxygenation (p less than 0.001) and in a substantial reduction in the spontaneous respiratory effort (p less than 0.001). We observed a slight decrease in stroke volume index (p less than 0.05) with increasing airway pressure in patients who had moderate left ventricular dysfunction, and a trend of improvement (NS) in those who had severe pump failure. Relatively high levels of CPAP can be used to improve pulmonary function in patients with acute myocardial infarction and left ventricular failure. In fact, circulatory depression is less likely to occur when cardiac performance is poor.     

Effects of periodic positive airway pressure by mask on postoperative pulmonary function

Postoperative pulmonary complications, alveolar-arteriolar oxygen difference ([A-a]O2-diff), peak expiratory flow (PEF) and forced vital capacity (FVC) were compared in patients using continuous positive airway pressure (CPAP) and positive expiratory pressure (PEP) administered by face mask against those of a control group using a deep-breathing device (Triflo). Forty-three consecutive, randomized patients undergoing elective upper abdominal surgery were included. CPAP, PEP and Triflo were administered for 30 consecutive breaths in every waking hour for three days postoperatively. The (A-a)O2-difference increased equally and significantly in the three groups after surgery, reaching a maximum on the first postoperative day. After this day, however, (A-a)O2-diff decreased in the CPAP and PEP groups, being significantly lower in the PEP group compared to the control group, two days postoperatively (p less than 0.05) and significantly lower in both the PEP and CPAP groups three days postoperatively (p less than 0.001 and p less than 0.05, respectively.) PEF did not differ significantly between the groups before or after surgery, while FVC was significantly higher in the PEP and CPAP groups, compared to control, on the third postoperative day (p less than 0.05). Atelectatic consolidation was observed in six of 15 patients in the control group three days postoperatively, the incidence being significantly lower in both the PEP group (0 of 15, p less than 0.001) and the CPAP group (one of 13, p less than 0.05). We concluded that periodic face mask administration of CPAP and PEP are superior to deep breathing exercises with respect to gas exchange, preservation of lung volumes and development of atelectasis after upper abdominal surgery. We also conclude that the simple and commercially available PEP mask is as effective as the more complicated CPAP system.     

持续气道正压通气对急性心源性肺水肿犬呼吸及循环功能的影响

目的研究持续气道正压(CPAP)通气对急性心源性肺水肿(ACPE)犬呼吸及循环功能的影响。方法分别监测10条犬健康状态及ACPE发生后自主呼吸、5cmH2O(1cmH2O=0.098kPa)、10cmH2O、15cmH2OCPAP时的胸腔负压(Pt)、中心静脉压(CVP)、心输出量(CO)、平均动脉压(BPm)、肺动脉楔压(PAWP)。结果与健康状态相比,ACPE犬呼吸增强、增快,Pt由-(4.90±0.09)cmH2O上升至-(10.90±0.75)cmH2O,CVP由(10.1±0.4)mmHg下降至(8.0±0.7)mmHg,CO由(1.52±0.13)L/min下降至(0.85±0.09)L/min,PAWP升高(P均<0.05)。CVP与Pt变化呈正相关(r=0.78,P<0.01)。5及10cmH2OCPAP时Pt值恢复至-(6.53±0.11)cmH2O和-(5.14±0.25)cmH2O,呼吸形式基本恢复正常,CVP升至(11.6±0.7)mmHg和(14.2±0.2)mmHg,CO增加至(1.45±0.11)L/min和(1.24±0.11)L/min,其中5cmH2OCPAP组PAWP下降(P均<0.05)。15cmH2OCPAP时,呼吸浅快,Pt为-(0.82±0.37)cmH2O,CO为(0.82±0.07)L/min,其他血流动力学指标皆恶化(P均<0.05)。结论犬ACPE发生时,呼吸运动显著增强,Pt升高,并导致CVP和CO的下降;适当CPAP通过改善呼吸功能,调节Pt改善ACPE犬的心功能。     

经鼻(面)罩通气治疗急性呼吸窘迫综合征

目的评价经鼻（面）罩机械通气治疗急性呼吸窘迫综合征（ABDS）的疗效。方法16例ARDS患者分为感染组（7例）和非感染组（9例）,前者呼吸频率（RR）（46±5）次／分,动脉血pH、二氧化碳分压（PaCO2）、氧合指数（OI）分别为7．49±0．05、（32±4）mmHg、（144±23）mmHg;后者为（41±6）次／分、7．49±0．13、（32±5）mmHg、（156±51）mmHg,经鼻（面）罩选择压力支持通气（PSV）＋呼气末正压（PEEP）。结果通气2－8h,与通气前比较感染组RR为（45±7）次／分,P＞0．05,OI升至（195±30）mmHg,P＜0．05;非感染组相应为（35±4）次／分和（228±90）mmHg（P＜0．05）。10例治愈,治愈率分别有29％（2／7）和89％（8／9）。结论　经鼻罩机械通气可作为治疗非感染性因素诱发的ARDS　的首选通气方式,而在感染患者应及早建立人工气道。     

Assisted ventilation in patients with preexisting cardiopulmonary disease. The effect on systemic oxygen consumption, oxygen transport, and tissue perfusion variables

We have evaluated systemic oxygen consumption (VO2), systemic oxygen transport, and tissue perfusion variables in 30 patients with preexisting cardiac and underlying pulmonary disease during continuous positive-pressure ventilation and positive end-expiratory pressure [PEEP], during intermittent mandatory ventilation (IMV and PEEP), and during spontaneous ventilation (continuous positive airway pressure [CPAP]), with end-expiratory pressure held constant during all ventilatory modes. Using radionuclide angiography together with invasive determinations of pressure and flow, we also measured left and right ventricular ejection fractions and calculated the end-systolic (ESVI) and end-diastolic (EDVI) volume indices of both ventricles. We found that oxygen transport was significantly greater during CPAP (583 +/- 172 ml/min/M2)(mean +/- SD) than during either IMV and PEEP (543 +/- 151 ml/min/sq; p less than 0.01) or CPPV and PEEP (526 +/- 159 ml/min/M2; p less than 0.01); however, we found no significant change in systemic VO2 with conversion from CPPV and PEEP to CPAP. The increase in oxygen transport was related to a greater cardiac index and, more specifically, to a higher heart rate during CPAP (CPAP, 106 +/- 16 beats per minute; CPPV and PEEP, 97 +/- 14 beats per minute) (p less than 0.01). Enhanced oxygen transport during CPAP was also associated with an increase in mixed venous oxygenation and a decrease in arterial lactate. Although neither the mean left ventricular EDVI nor ESVI changed from CPPV and PEEP to CPAP, the mean pulmonary capillary wedge pressure increased (CPPV and PEEP, 12 +/- 5 mm Hg; CPAP, 14 +/- 7 mm Hg) (p less than 0.01), suggesting the possibility of a decrease in left ventricular compliance with the spontaneous ventilatory mode. This study suggests that in the absence of ventilatory failure, spontaneous ventilation provides for better systemic oxygen transport and overall tissue perfusion than either controlled ventilation or IMV; however, this benefit of enhanced oxygen delivery with spontaneous ventilation may potentially be offset by a decrease in left ventricular compliance.     

Use of an ultra short-acting beta-blocker in patients with acute myocardial ischemia

Esmolol is a new ultra short-acting (half-life [t1/2] beta 9 min) beta 1-adrenergic-receptor antagonist reported to have no intrinsic sympathomimetic activity. The safety and efficacy of esmolol in lowering the ventricular rate and rate-pressure product in patients with acute myocardial infarction (n = 5), postmyocardial infarction angina (n = 10), or acute unstable angina (n = 4), and without cardiogenic shock were studied. After a 30 min observation period, esmolol was titrated to a maximum dose of 300 micrograms/kg/min and infused for up to 420 min. The ventricular rate fell from 92 +/- 11 (mean +/- SD) to 77 +/- 13 beats/min (p less than .01) and the systolic arterial pressure decreased from 120 +/- 13 to 97 +/- 11 mm Hg (p less than .01) during the initial 30 min titration period. There was no significant change during the maintenance phase, and both the ventricular rate and arterial pressure returned rapidly toward baseline values within 30 min of termination of the infusion. The cardiac index fell from 2.8 +/- 0.6 to 2.2 +/- 0.6 liters/min/m2 (p less than .01) during the same period, and also returned to the baseline level 30 min after termination of the infusion. There was no significant change in the pulmonary capillary wedge pressure, respiratory rate, or PR interval. Five patients required termination of infusion because of hypotension and all recovered uneventfully within 30 min of stopping the esmolol. One patient required a brief infusion of dopamine to restore hemodynamic stability.(ABSTRACT TRUNCATED AT 250 WORDS)     

Acute effects of automated continuous positive airway pressure on blood pressure in patients with sleep apnea and hypertension

BACKGROUND: The obstructive sleep apnea-hypopnea syndrome (OSAHS) is characterized by repetitive upper airway obstructions during sleep, and it might cause cardiovascular complications such as myocardial infarction, arrhythmias, and systemic and pulmonary hypertension. Objectives: We investigated the acute effects of automatic continuous positive airway pressure (automated CPAP) on blood pressure in patients with OSAHS and hypertension. METHODS: Polysomnography was used and ambulatory blood pressure measurements were done in 12 patients with OSAHS. Blood pressure and heart rate were measured at night (10 p.m. to 6 a.m.) and during the day (6 a.m. to 10 p.m.). During these periods systolic, diastolic and mean blood pressure and heart rate of the patients on the diagnostic day were compared with those on the treatment day. RESULTS: Patients had moderate or severe OSAHS; their mean age was 52.8+/-4.2 years. Systolic, diastolic and mean blood pressure and heart rate between the diagnostic and treatment day were not significantly different. Standard deviations of all these parameters during the night of the treatment day (9.1+/-4.5, 7.5+/-3.3, 8.0+/-3.0 mm Hg, and 4.8+/-1.5 beats/min, respectively) were significantly lower than during the night of the diagnostic day (12.6+/-4.9 mm Hg, p=0.023, 10.8+/-3.5 mm Hg, p=0.004, 11.6+/-4.4 mm Hg, p=0.006 and 6.9+/-1.6 beats/min, p=0.003, respectively). We did not find similar results during daytime periods. CONCLUSIONS: Automated CPAP therapy in patients with sleep apnea and hypertension did not decrease systolic and diastolic blood pressures and heart rates acutely. However, it might reduce the variability of these parameters during sleep in patients, but not during the day. It might be suggested that automated CPAP reduces cardiovascular morbidity of OSAHS via stabilizing heart rate and blood pressure during sleep.     

机械通气在抢救急性肺水肿时的临床疗效

目的:探讨机械通气在抢救急性肺水肿时的方法和临床疗效。方法:通过分析我院20例急性肺水肿患者机械通气前后体征(血压、心率、呼吸频率)、血气分析(pH、PaO2、SaO2、PaCO2、HCO3-)、X线胸片的变化,并参考相关文献总结机械通气治疗急性肺水肿的方法和效果。有效的机械通气方法包括:高频通气和呼气末正压通气(PEEP)。结果:急性肺水肿并发呼吸衰竭患者机械通气之后1、12h较通气之前的平均血压有所下降,[分别为123.0/74.0、118.0/67.0、129.0/75.5mmHg(1mmHg=0.133kPa),通气后12h与通气前比较,P<0.05]平均心率减慢(分别为98、89、105次/min,通气后12h与通气前比较,P<0.05),平均呼吸频率减慢(分别为22.0、21.0、27.4次/min,均P<0.05),平均SaO2显著改善(分别为91.2%、95.1%、76.2%,均P<0.01)。患者机械通气之后较通气之前PaO2明显增高(从48.8mmHg增加至85.1mmHg),具有统计学意义(P<0.05),其他动脉血气分析指标无明显变化。治疗前后X线胸片提示肺水肿明显改善。结论:正压机械通气是治疗各种原因(包括冠心病急性心肌梗死)引起急性严重左心功能不全的重要辅助措施,严格掌握适应证、密切观察病情、选择合适的通气方法、设置合适的参数,可在短期内使急性肺水肿患者病情改善。     

Administration of enoximone in cardiogenic shock

Thirteen patients in severe cardiogenic shock, persisting despite the use of adrenergic agents, were treated with enoximone, a recently available phosphodiesterase inhibitor. Cardiogenic shock was characterized by low cardiac output (less than 2.5 liter.min-1.m-2), elevated pulmonary artery balloon-occluded pressure (greater than or equal to 15 mm Hg), decreased urine output (less than 20 ml.hour-1) and increased blood lactate (greater than or equal to 2.0 mEq.liter-1). Ten patients were mechanically ventilated. A short-term intravenous infusion of 0.5 mg.kg-1 in 20 minutes of enoximone resulted in significant increases in cardiac index (from 1.8 +/- 0.3 to 2.9 +/- 0.3 liter.min-1.m-2, p less than 0.001) and stroke index (from 17.8 +/- 3.3 to 21.9 +/- 5.1 ml.m-2, p less than 0.001) and significant decrease in pulmonary artery balloon-occluded pressure (from 21.7 +/- 5.8 to 19.8 +/- 6.0 mm Hg, p less than 0.01) without a consistent change in mean arterial pressure (from 79 +/- 8 to 76 +/- 9 mm Hg, difference not significant). Enoximone administration decreased arterial oxygen tension (from 108 +/- 42 to 94 +/- 36 mm Hg, p less than 0.01) and increased venous admixture (from 12.8 +/- 6.5 to 16.0 +/- 8.0%, p less than 0.01). In 8 patients, a second infusion of 0.5 mg.kg-1 immediately thereafter amplified these changes. All patients but one survived the episode of cardiogenic shock and 5 patients left the hospital alive. These results indicate that the addition of enoximone to adrenergic agents in the treatment of cardiogenic shock can markedly increase cardiac output and stroke volume without substantial effects on arterial pressure.     

Proportional positive airway pressure: a new concept to treat obstructive sleep apnoea.

Proportional positive airway pressure (PPAP) was designed to optimize airway pressure for the therapy of obstructive sleep apnoea (OSA). In a randomized crossover prospective study, the clinical feasibility of PPAP and its immediate effects on the breathing disorder and sleep in comparison with continuous positive airway pressure (CPAP) was evaluated. Twelve patients requiring CPAP therapy underwent CPAP and PPAP titration in a random order. Obstructive and mixed respiratory events could be completely abolished with both forms of treatment. This efficacy could be achieved at a significantly lower mean mask pressure during PPAP titration (8.45+/-2.42 cmH2O) compared to CPAP (9.96+/-2.7 cmH2O) (p=0.002). The mean minimal arterial oxygen saturation (Sa,O2) (82.8+/-6.5%) on the diagnostic night increased significantly (p<0.001) to an average Sa,O2 of 93.35+/-1.71% and 93.19+/-2.9% during CPAP and PPAP titration. Total sleep time, slow wave sleep and rapid eye movement (REM) sleep increased significantly by the same amount during both CPAP and PPAP titration (p<0.001), while sleep stage nonrapid eye movement (NREM) 1 and 2 decreased. Six patients preferred the PPAP titration night, four patients did not have a preference, and two patients preferred CPAP. The present data show that proportional positive airway pressure is as effective as continuous positive airway pressure in eliminating obstructive events and has the same immediate effect on sleep. The lower average mask pressure during proportional positive airway pressure implies potential advantages compared to continuous positive airway pressure. Proportional positive airway pressure presents a new effective therapeutic approach to obstructive sleep apnoea.     

Hemodynamic and oxygen transport variables in cardiogenic shock secondary to acute myocardial infarction, and response to treatment

There are few data on oxygen transport in cardiogenic shock after acute myocardial infarction. This prospective study examined oxygen transport variables in 19 such patients and assessed their responses to treatment. Femoral and pulmonary arterial catheters were inserted before any therapy except correction of hypoxemia by mechanical ventilation in 8 patients, defibrillation (3 patients) or pacing (5 patients). In 3 patients mean arterial pressure was greater than 80 mm Hg and cardiac index greater than 2.1 liters/min/m2 with normal mixed venous oxygen saturation despite simultaneous clinical shock. They recovered with no further treatment. Sixteen patients were treated with varying combinations of intravenous fluids and dobutamine (37 +/- 25 mu/kg/min) and 14 survived long enough for a second set of measurements to be completed. Mean heart rate increased from 83 +/- 22 to 101 +/- 20 beats/min and mean cardiac index from 1.4 +/- 0.5 to 2.5 +/- 0.4 liters/min/m2 (p less than 0.001). Oxygen consumption (VO2) was maintained even when oxygen delivery (DO2) was less than 330 ml/min/m2. After treatment DO2 increased from 230 +/- 69 to 397 +/- 60 ml/min/m2 (p less than 0.001) and VO2 from 103 +/- 31 to 124 +/- 27 ml/min/m2 (p less than 0.05). Mean mixed venous oxygen saturation increased from 54 +/- 16 to 69 +/- 8% (p less than 0.001) and mean oxygen extraction ratio decreased from 48 +/- 16 to 31 +/- 6% (p less than 0.001). There was no correlation between cuff systolic blood pressure and mean arterial pressure before or after resuscitation. Thirteen patients survived to hospital discharge. When cardiogenic shock responds to treatment, large increases in DO2 lead to small increases in VO2 but large increases in mixed venous oxygen saturation, reflecting improved tissue oxygen availability.     

Inter-machine variability in the stability of continuous positive airway pressure.

Two studies were performed to investigate the differences in pressure stability performance of the continuous positive airway pressure (CPAP) machines used by our patients. The variations of mask pressures during each respiratory cycle were measured during overnight studies of two groups of patients with obstructive sleep apnoea, who were using either a Sleep-Easy III CPAP machine or a Si-Plan CPAP unit. The patients were well-matched for age, weight and neck circumference. The group using the Si-Plan unit had more constant mask pressures and were using lower CPAP pressures (mean 10.6 cmH2O) than those using the Sleep-Easy III machine (mean 13.8 cmH2O) (p less than 0.02). The pressure stability performance of five CPAP machines used by our patients was also compared using standardized simulated patient breaths produced by a negative pressure cuirass pump. There were large differences between the machines in ability to maintain a constant pressure. Using a tidal volume of 0.5 l and peak flow rates of between 20-40 l.min-1 the pressure variation ranged from 0-67% of the minimum inspiratory pressure. The maintenance of a constant pressure during inspiration and expiration lowers the mean pressure required to eliminate obstructive sleep apnoeas and reduces the likelihood of pressure related side-effects.     

Comparison of nalbuphine hydrochloride versus morphine sulfate for acute myocardial infarction with elevated pulmonary artery wedge pressure

The hemodynamic and respiratory effects of intravenous nalbuphine hydrochloride and morphine sulfate were compared in a randomized fashion in 20 patients (age 65 +/- 11 years) with acute myocardial infarction and elevated pulmonary artery wedge pressure. Titration of the nalbuphine dose to lower pulmonary artery wedge pressure by greater than or equal to 25% resulted in a decrease of this parameter from 22 +/- 3 to 15 +/- 4 mm Hg, and was associated with a reduction in heart rate from 106 +/- 20 to 96 +/- 19 beats/min (p less than 0.05) and decreases in mean blood pressure (78 +/- 8 to 70 +/- 12 mm Hg, p less than 0.05) and mean pulmonary artery pressure (31 +/- 4 to 22 +/- 5 mm Hg, p less than 0.05), without any remarkable change seen in cardiac index (2.21 +/- 0.43 to 2.22 +/- 0.50 liter/min/m2, difference not significant), stroke volume index (22 +/- 7 to 23 +/- 4 ml/m2, difference not significant), stroke work index (17 +/- 7 to 18 +/- 7 g.m/m2), or systemic and pulmonary vascular resistances (1,675 +/- 333 to 1,513 +/- 508 and 191 +/- 78 to 170 +/- 109 dynes.s.cm-5 respectively, all differences not significant). Nalbuphine also significantly reduced respiratory rate (32 +/- 8 to 26 +/- 8 resp/min, p less than 0.05) and pH (7.45 +/- 0.04 to 7.41 +/- 0.03, p less than 0.05) and increased arterial PCO2 (32 +/- 6 to 35 +/- 6 mm Hg, p less than 0.05) without any major change in arterial PO2 (63 +/- 13 to 66 +/- 17 mm Hg, difference not significant).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of therapeutic paracentesis on systemic and hepatic hemodynamics and on renal and hormonal function

Thirteen patients with cirrhosis and tense ascites (six with and seven without peripheral edema) underwent 4- to 15-liter paracentesis without intravenous "colloid" replacement. Cardiac output increased from 6.6 +/- 0.7 liters per min at baseline to 8.2 +/- 0.7 liters per min (p less than 0.003) 1 hr after large-volume paracentesis completion and fell to 7.5 +/- 0.69 liters per min (p less than 0.05 vs. baseline, p less than 0.02 vs. 1 hr) 24 hr after large-volume paracentesis completion. There was no change in mean arterial pressure or mean pulmonary artery pressure. Central venous pressure fell from 9.1 +/- 0.8 mm Hg at baseline to 8.6 +/- 1.4 mm Hg 1 hr post-large-volume paracentesis to 6.8 +/- 1.0 mm Hg (p less than 0.005 vs. baseline, p less than 0.02 vs. 1 hr value) at 24 hr, and pulmonary capillary wedge pressure fell from 13.1 +/- 0.9 to 11.1 +/- 1.3 mm Hg 1 hr after large-volume paracentesis and to 9.89 +/- 1.2 (p less than 0.01 vs. baseline, p less than 0.03 vs. 1 hr after large-volume paracentesis) at 24 hr. Heart rate fell from 90 +/- 3.0 to 85 +/- 2.9 beats per min (p less than 0.01) 1 hr after large-volume paracentesis completion, but increased to 89 +/- 2.5 beats per min (p less than 0.02 vs. 1 hr after large-volume paracentesis) at 24 hr.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of continuous positive airway pressure and placebo treatment on sympathetic nervous activity in patients with obstructive sleep apnea

STUDY OBJECTIVES: We studied the effect of continuous positive airway pressure (CPAP) treatment on sympathetic nervous activity in 38 patients with obstructive sleep apnea. DESIGN: Randomized, placebo-controlled trial. SETTING: Patients underwent polysomnography on three occasions in a clinical research center, and had BP monitored over 24 h at home. All of the patients had sleep apnea with a respiratory disturbance index (RDI) > 15. INTERVENTIONS: The patients were randomized blindly to CPAP or placebo (CPAP at ineffective pressure) treatment. Measurements and results: Prior to therapy, the number of apneas and the severity of nocturnal hypoxia correlated significantly with daytime urinary norepinephrine (NE) levels, but not nighttime urinary NE levels. CPAP treatment lowered daytime BP from 99 +/- 2 mm Hg to 95 +/- 3 mm Hg (mean +/- SEM) and nighttime BP from 93 +/- 3 mm Hg to 88 +/- 3 mm Hg. Placebo CPAP treatment decreased both day and night mean BP only 2 mm Hg. CPAP, but not placebo, treatment lowered daytime plasma NE levels by 23%, daytime urine NE levels by 36%, daytime heart rate by 2.6 beats/min, and increased lymphocyte beta(2)-adrenergic receptor sensitivity (all p < 0.05). The effect of CPAP treatment on nighttime urine NE levels and heart rate did not differ from placebo treatment. There was a suggestion of an effect of placebo CPAP treatment on nighttime measures, but not on daytime measures. CONCLUSION: We conclude that daytime sympathetic nervous activation is greater with more severe sleep apnea. CPAP treatment diminished the daytime sympathetic activation; the potential nighttime effect of CPAP treatment was obscured by a small placebo effect.