Noninvasive Pressure Support Ventilation Research Articles

Effects of Different Ventilator Settings on Sleep and Inspiratory Effort in Patients with Neuromuscular Disease

Patients with neuromuscular disease (NMD) who require long-term ventilation normally have the ventilation set using empirical daytime parameters. We evaluated arterial blood gases (ABG), breathing pattern, respiratory muscle function, and sleep architecture during ventilation with two noninvasive Pressure Support Ventilation (nPSV) settings in nine patients with NMD. The two settings were randomly applied: the usual (US), with the nPSV setting titrated on simple clinical parameters, and the physiological (PHYS), tailored to the patient's respiratory effort. During wakefulness, nPSV significantly improved ABG and minute ventilation and reduced the diaphragmatic pressure-time product (PTPdi/breath), independently of the type of setting (PTPdi/breath spontaneous breathing 5.7 +/- 2.4, US 3.2 +/- 2, PHYS 3.6 +/- 1.6 cm H2O . seconds(-1), p < 0.001). However, during sleep, PHY nPSV resulted in a significant improvement of gas exchange, sleep efficiency (71.7% +/- 14 US vs. 80.6% +/- 8.3 PHYS, p < 0.01) and % of REM sleep (9.1% +/- 7 US vs. 17.3% +/- 5.4 PHYS, p < 0.01). This improvement was significantly correlated with the reduction in ineffective efforts. In NMD, nPSV is effective in improving daytime ABG and in unloading inspiratory muscles independently of whether it is set on the basis of the patient's comfort or the patient's respiratory mechanics. However, PHYS was associated with better sleep architecture and nighttime gas exchange.

Noninvasive pressure support ventilation vs. continuous positive airway pressure in acute hypercapnic pulmonary edema

This study compared noninvasive pressure support ventilation (NIPSV) and continuous positive airway pressure (CPAP) in patients with acute hypercapnic pulmonary edema with regard to resolution time. Randomized prospective study in an emergency department. We randomly assigned 36 patients with respiratory failure due to acute pulmonary edema and arterial hypercapnia (PaCO(2) >45 mmHg) to NIPSV (n=18) or CPAP through a face mask (n=18). Electrocardiographic and physiological measurements were made over 36 h. There was no difference in resolution time defined as clinical improvement with a respiratory rate of fewer than 30 breaths/min and SpO(2)of 96% or more between CPAP and NIPSV groups. Arterial carbon dioxide tension was significantly decreased after 1 h of ventilation (CPAP, 60.5+/-13.6 to 42.8+/-4.9 mmHg; NIPSV, 65.7+/-13.6 to 44.0+/-5.5 mmHg); respective improvements were seen in pH (CPAP, 7.22+/-0.11 to 7.37+/-0.04; NIPSV, 7.19+/-0.11 to 7.38+/-0.04), SpO(2) (CPAP, 86.9+/-3.7% to 95.1+/-2.6%; NIPSV, 83.7+/-6.6% to 96.0+/-2.9%), and respiratory rate (CPAP, 37.9+/-4.5 to 21.3+/-5.1 breaths/min; NIPSV, 39.8+/-4.4 to 21.2+/-4.6 breaths/min). No significant differences were seen with regards to endotracheal intubation and in-hospital mortality. NIPSV proved as effective as CPAP in the treatment of patients with acute pulmonary edema and hypercapnia but did not improve resolution time.

Inspiratory muscle workload due to dynamic intrinsic PEEP in stable COPD patients: effects of two different settings of non-invasive pressure-support ventilation

In severe stable hypercapnic COPD patients the amount of pressure time product (PTP) spent to counterbalance their dynamic intrinsic positive end expiratory pressure (PEEPi,dyn) is high: no data are available on the best setting of non invasive pressure support ventilation (NPSV) to reduce the inspiratory muscle workload due to PEEPi,dyn. The objectives of this randomised controlled physiological study were: 1. To measure the inspiratory muscle workload due to PEEPi,dyn 2. To measure the effects on this parameter of two settings of NPSV in stable COPD patients with chronic hypercapnia admitted in a Pulmonary Division of two Rehabilitation Centers. Twenty-three stable COPD patients with chronic hypercapnia on domiciliary nocturnal NPSV for 30 +/- 20 months were submitted to an evaluation of breathing pattern, PEEPi,dyn, inspiratory muscle workload and its partitioning during both assisted and unassisted ventilation. Two settings of NPSV were randomly applied for 30 minutes each: i- "at patient's comfort" (C): Inspiratory pressure support (IPS) was the maximal tolerated pressure able to reduce awake PaCO2 with the addition of a pre-set level of external PEEP (PEEPe); ii- "physiological setting" (PH): the level of IPS able to achieve a > 40% and < 90% decrease in transdiaphragmatic pressure in comparison to spontaneous breathing (SB). A PEEPe level able to reduce PEEPi,dyn by at least 50% was added. During SB the tidal diaphragmatic pressure-time product (PTPdi/b) was 17.62 +/- 7.22 cmH2O*sec, the component due to PEEPi,dyn (PTPdiPEEPi,dyn) being 38 +/- 17% (range: 16-65%). Compared to SB,PTPdiPEEPi,dyn was reduced significantly with both settings, the reduction being greater with PH compared to C. In conclusion in severe COPD patients with chronic hypercapnia the inspiratory muscle workload due to PEEPidyn is high and is reduced by NPSV at a greater extent when ventilator setting is tailored to patient's mechanics.

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 ≤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.

Short-term Noninvasive Pressure Support Ventilation Prevents ICU Admittance in Patients With Acute Cardiogenic Pulmonary Edema

Noninvasive ventilation, although effective as treatment for patients with acute cardiogenic pulmonary edema when prolonged for hours, is of limited use in the emergency department (ED). The aim of the study was to determine whether a short attempt at noninvasive pressure support ventilation avoids ICU admittance and to identify lack of response prediction variables. Prospective inception cohort study. ED of a university hospital. Fifty-eight consecutive patients with cardiogenic pulmonary edema who had been unresponsive to medical treatment and were admitted between January 1999 and December 2000. Pressure support ventilation was instituted through a full-face mask until the resolution of respiratory failure. A 15-min "weaning test" was performed to evaluate clinical stability. Responder patients were transferred to a medical ward. Nonresponding patients were intubated and were admitted to the ICU. The included optimal length of intervention, the avoidance of ICU admittance, the incidence of myocardial infarction, and predictive lack of response criteria. Patients completed the trial (mean [+/- SD] duration, 96 +/- 40 min). None of the responders (43 patients; 74%) was subsequently ventilated or was admitted to the ICU. Two new episodes of myocardial infarction were observed. Thirteen of 58 patients died. A mean arterial pressure of < 95 mm Hg (odds ratio [OR], 10.6; 95% confidence interval [CI], 1.8 to 60.8; p < 0.01) and COPD (OR, 9.4; 95% CI, 1.6 to 54.0; p < 0.05) at baseline predicted the lack of response to noninvasive ventilation. A short attempt at noninvasive ventilation is effective in preventing invasive assistance. A 15-min weaning test can identify patients who will not need further invasive ventilatory support. COPD and hypotension at baseline are negative predictive criteria.

Influence of Respiratory Behavior on Ventilation, Respiratory Work and Intrinsic PEEP during Noninvasive Nasal Pressure Support Ventilation in Normal Subjects

Background: In clinical practice, patients have different inspiratory behaviors during noninvasive pressure support ventilation (PSV): some breathe quietly, others actively help PSV by an additional effort, and others even resist the inspiratory pressure of PSV. Objective: What is the influence of patient collaboration (inspiratory behavior) on the efficiency of PSV? Methods: We ventilated 10 normal subjects with nasal PSV (inspiratory/expiratory: 10/0 and 15/5 cm H₂O) and measured their flow and volume with a pneumotachograph and their esophageal and gastric pressures during three different respiratory voluntary behaviors: relaxed inspiration, active inspiratory work and resisted inspiration. Results: When compared with relaxed inspiration with 10/0 cm H₂O PSV: (1) an active inspiratory effort increased tidal volume (from 789 ± 356 to 1,046 ± 586 ml; p = 0.006), minute ventilation (from 10.40 ± 4.45 to 15.77 ± 7.69 liters/min; p < 0.001), transdiaphragmatic work per cycle (from 0.55 ± 0.33 to 1.72 ± 1.40 J/cycle; p = 0.002) and inspiratory work per cycle (from 0.14 ± 0.20 to 1.26 ± 1.01 J/cycle; p = 0.003); intrinsic positive end-expiratory pressure (PEEP_i) increased from 1.23 ± 1.02 to 3.17 ± 2.30 cm H₂O; p = 0.002); (2) a resisted inspiration decreased tidal volume (to 457 ± 230 ml; p = 0.007), minute ventilation (to 6.93 ± 3.04 liters/min; p = 0.028) along with a decrease in transdiaphragmatic work but no change in PEEP_i. Data obtained during a bilevel PSV of 15/5 cm H₂O were similar to those obtained with the 10/0 cm H₂O settings. Conclusions: Active inspiratory effort increases ventilation during PSV at the expense of an increased breathing work and PEEP_i. Resisted inspiration inversely decreases inspiratory work and ventilation with no air trapping. These differences between inspiratory behaviors could affect the expected beneficial effects of PSV in acutely ill patients.

Linear and nonlinear mathematical models for noninvasive ventilation

Two mathematical models are proposed for passive, noninvasive ventilation. Both models take the form of coupled ordinary differential equations that describe the volume in a single compartment lung. One model is linear and the other nonlinear; both models are derived from basic pressure balances in the lung-ventilator system. These models are also compared to a physical model using a test lung. Both the physical and mathematical models exhibit instabilities that appear to have important clinical implications. The simulations from these models, and the forms of their governing equations, suggest that the presence of an airway leak proximal to the airway opening during pressure support noninvasive ventilation may render this mode of ventilation dynamically unstable. The mathematical models are extended to incorporate a special type of nonpassive ventilation where the total cycle times of the ventilator depend on the inspiratory phases of these cycles.

Mask mechanics and leak dynamics during noninvasive pressure support ventilation: a bench study.

To study the mask mechanics and air leak dynamics during noninvasive pressure support ventilation. Laboratory of a university hospital. A facial mask was connected to a mannequin head that was part of a mechanical respiratory system model. The mask fit pressure (P(mask-fit)) measured inside the mask's pneumatic cushion was adjusted to 25 cmH(2)O using elastic straps. Pressure support (PS) was set to ensure a maximal tidal volume distal to the mask (VT(distal)) but avoiding failure to cycle to exhalation. Airway pressure (P(aw)), P(mask-fit), mask occlusion pressure (P(mask-occl)=P(mask-fit)-P(aw)), VT proximal (VT(prox)), distal to the mask (VT(distal)), air leak volume ( Leak=VT(prox)-VT(distal)), and inspiratory air leak flow rate (difference between inspiratory flow proximal and distal to the mask) were recorded. PS 15 cmH(2)O was the highest level that could be used without failure to cycle to exhalation (VT(distal) of 585+/-4 ml, leak of 32+/-1 ml or 5.2+/-0.2% of VT(prox), and a minimum P(mask-occl) of 1.7+/-0.1 cmH(2)O). During PS 16 cmH(2)O the P(mask-occl) dropped to 1.1+/-0.1 cmH(2)O, and at this point all flow delivered by the ventilator leaked around the mask, preventing the inspiratory flow delivered by the ventilator from reaching the expiratory trigger threshold. P(mask-fit) and P(mask-occl) can be easily measured in pneumatic cushioned masks and the data obtained may be useful to guide mask fit and inspiratory pressure set during noninvasive positive pressure ventilation.

Non-invasive pressure support ventilation in patients with acute respiratory failure after bilateral lung transplantation

To evaluate non-invasive ventilation (NIV) prospectively in a group of patients developing acute respiratory failure (ARF) after bilateral lung transplantation (BLT). General intensive care unit (ICU) of Rome "La Sapienza" University. Twenty-one patients (18 with cystic fibrosis) undergoing BLT. All consecutive patients developing ARF (according to predefined criteria) and requiring ventilatory support, received non-invasive pressure support ventilation through a face-mask (PEEP 5 cmH2O, PSV 14+/-2 cmH2O) for a mean period of 5+/-4 days. Eighteen out of 21 patients avoided intubation and were discharged from the ICU; 3 patients required intubation: 1 of them survived while 2 developed septic shock and died. NIV administration was well tolerated and avoided intubation in the large majority of patients (86%); in NIV responders the rate of complications was low and ICU mortality nil. NIV should be considered as an interesting alternative to conventional ventilation in patients who require ventilatory support after BLT.

Non-invasive pressure support ventilation in severe community-acquired pneumonia.

Objective: To explore three aspects of non-invasive pressure support ventilation (NIPSV) applied by face mask to patients with acute respiratory failure (ARF) due to severe community-acquired pneumonia (CAP): (1) the initial acute effects on respiratory rate, gas exchange and hemodynamics, (2) the clinical course and outcome during ICU and hospital stay, (3) the nursing workload as measured by the daily PRN 87 (Project Research in Nursing) score. Setting: Medical ICU, University Hospital. Design: Prospective, observational study. Patients: Patients without any prior history of chronic lung disease, consecutively admitted to the ICU to receive NIPSV for ARF due to severe CAP. Measurements and results (means ± SD): Twenty-four patients aged 49±17 years, admission APACHE II 13±5, were included. Admission PaO2/FIO2, alveolar-arterial oxygen difference (DA-aO2) and PaCO2 were 104±48, 447±120 and 40±10 mmHg, respectively. All patients were normotensive. During the initial NIPSV trial respiratory rate decreased from 34±8 to 28±10 breaths/min (p<0.001) and arterial oxygenation improved (PaO2/FIO2 104±48 vs 153±49, DA-aO2 447±120 vs 370±180 mmHg, p<0.001) while PaCO2 remained unchanged. There were no hemodynamic effects. Subsequently, a total of 133 NIPSV trials were performed (median duration 55 min, range 30–540 min) over 1–7 days. No complication occurred during NIPSV. Sixteen patients were intubated (66%) 1.3±1 days after inclusion. Upon inclusion, the patients who were subsequently intubated were older (55±15 vs 37±12 years) and more severely hypoxemic (63±11 vs 80±15 mmHg, p<0.05) than those not requiring intubation. Eight patients died (33%), all in the intubated group. Median lengths of stay in the ICU and hospital were longer in intubated patients (ICU 16 days, range 3–64 vs 6 days, range 3–7, p<0.05; hospital 23 days, range 9–77 vs 9.5 days, range 4–42, p<0.05). Mean daily total PRN points were stable throughout the NIPSV period and were not different between the groups. Only 14% of PRN points resulted from respiratory therapy interventions. PRN score was higher during the first 24 h following intubation than during the first 24 h of NIPSV (278±55 vs 228±24 points, p<0.05). Conclusion: Despite initial improvement in arterial oxygenation with NIPSV in patients with ARF due to severe CAP, the intubation rate is high. However, the more favorable outcome and shorter ICU and hospital stays when intubation is avoided, as well as the short delay required to assess the success or failure of NIPSV warrants a trial of NIPSV in this setting. The nursing workload remains stable during NIPSV and does not result predominantly from respiratory therapy interventions.

Patient-ventilator interaction during noninvasive pressure supported spontaneous respiration in patients with hypercapnic COPD

Noninvasive pressure support ventilation (NPSV) demands triggering with each breath. This study investigates the effects of NPSV via face mask on breathing pattern, ventilation and respiratory muscle loading in patients with hypercapnic stable COPD. 7 patients (age 66 +/- 9 years; FEV1 43 +/- 13% predicted; PaO2 52 +/- 19 mmHg; PaCO2 58 +/- 12 mmHg) were included. The physiologic variables were evaluated during spontaneous breathing and at the end of a 60 minutes period with NPSV. Inspiratory positive airway pressure (IPAP) and expiratory positive airway pressure (EPAP) were adjusted to 12-14 cm H2O and 3 cm H2O, respectively. Respiratory muscle activity was measured as esophageal and transdiaphragmatic pressure time product (PTPes and PTPdi). Non-triggering was observed only occasionally. Compared to unsupported spontaneous breathing NPSV improved ventilation: PaCO2 was reduced from 58 +/- 11 mmHg to 50 +/- 14 mmHg (p +/- 0.05). Respiratory muscles were unloaded by 30% (p +/- 0.05). Breathing frequency and breathing pattern did not change. In patients with hypercapnic stable COPD NPSV effectively recognizes and supports breathing efforts. As a result ventilation is improved and respiratory muscles are unloaded.

Non-invasive pressure support ventilation versus conventional oxygen therapy in acute cardiogenic pulmonary oedema: a randomised trial

Non-invasive pressure support ventilation (NIPSV) is an effective treatment for acute respiratory failure in patients with chronic obstructive pulmonary disease. We assessed the efficacy of this therapy in acute cardiogenic pulmonary oedema in a randomised comparison with conventional oxygen therapy. 40 patients were randomly assigned conventional oxygen therapy or NIPSV supplied by a standard ventilator through a face mask, with adjustment of tidal volume and pressure support in addition to a positive end-expiratory pressure of 5 cm water. Physiological measurements were obtained in the first 2 h and at 3 h, 4 h, and 10 h. The main endpoints were intubation rate and resolution time. Analyses were by intention to treat. Three patients were withdrawn on the basis of clinical and chest radiography results. Endotracheal intubation was required in one (5%) of 19 patients assigned NIPSV and in six (33%) of 18 assigned conventional oxygen therapy (p=0.037). Resolution time (defined as a clinical improvement with oxygen saturation of 96% or more and respiratory rate less than 30 breaths/min) was significantly shorter in the NIPSV group (median 30 [IQR 15-53] vs 105 [50-230] min, p=0.002). NIPSV led to a rapid improvement in oxygenation in the first 2 h. There were no differences in hospital length of stay or mortality. In this study of acute cardiogenic pulmonary oedema, NIPSV was superior to conventional oxygen therapy. Further studies should compare NIPSV with continuous positive airway pressure.

The Appropriate Setting of Noninvasive Pressure Support Ventilation in Stable COPD Patients

To evaluate the short-term physiologic effects of two settings of nasal pressure-support ventilation (NPSV) in stable COPD patients with chronic hypercapnia. Randomized controlled physiologic study. Lung function units and outpatient clinic of two affiliated pulmonary rehabilitation centers. Twenty-three patients receiving domiciliary nocturnal NPSV for a mean (+/- SD) duration of 31 +/- 20 months. Evaluation of arterial blood gases, breathing pattern, respiratory muscles, and dynamic intrinsic positive end-expiratory pressure (PEEPi,dyn) during both unassisted and assisted ventilation. Two settings of NPSV were randomly applied for 30 min each: (1) usual setting (U), the setting of NPSV actually used by the individual patient at home; and (2) physiologic setting (PHY), the level of inspiratory pressure support (IPS) and external positive end-expiratory pressure (PEEPe) tailored to patient according to invasive evaluation of respiratory muscular function and mechanics. All patients tolerated NPSV well throughout the procedure. Mean U was IPS, 16 +/- 3 cm H(2)O and PEEPe, 3.6 +/- 1.4 cm H(2)O; mean PHY was IPS, 15 +/- 3 cm H(2)O and PEEPe, 3.1 +/- 1.6 cm H(2)O. NPSV was able to significantly (p < 0.01) improve arterial blood gases independent of the setting applied. When compared with spontaneous breathing, both settings induced a significant increase in minute ventilation (p < 0.01). Both settings were able to reduce the diaphragmatic pressure-time product, but the reduction was significantly greater with PHY (by 64%; p < 0.01) than with U (56%; p < 0.05). Eleven of 23 patients (48%) with U and 7 of 23 patients (30%) with PHY showed ineffective efforts (IE); the prevalence of IE (20 +/- 39% vs 6 +/- 11% of their respiratory rate with U and PHY, respectively) was statistically different (p < 0.05). In COPD patients with chronic hypercapnia, NPSV is effective in improving arterial blood gases and in unloading inspiratory muscles independent of whether it is set on the basis of patient comfort and improvement in arterial blood gases or tailored to a patient's respiratory muscle effort and mechanics. However, setting of inspiratory assistance and PEEPe by the invasive evaluation of lung mechanics and respiratory muscle function may result in reduction in ineffective inspiratory efforts. These short-term results must be confirmed in the long-term clinical setting.

Noninvasive ventilation for acute respiratory failure. Quite low time consumption for nurses.

Methods of noninvasive pressure support ventilation (NIPSV) are not always easy to apply in patients with acute exacerbations of chronic obstructive pulmonary disease (COPD). The assistance time spent by nurses in relation to ventilatory time was prospectively studied, when NIPSV was used, in a sequential mode, in COPD patients with either acute exacerbations (58 patients, group I) or postextubation hypercapnic respiratory insufficiency (42 patients, group II) in a medical intensive care unit. During the first 24 h after enrolment, NIPSV was used for 6.7+/-3.2 h (mean+/-SD) in group I and 5.6+/-3.1 h in group II; the duration of NIPSV sessions and the nurse time consumption per session were respectively 47+/-12 and 11+/-7 min in group 1, and 46+/-12 and 11+/-6 min in group II. After the first 24 h of the study, the duration of NIPSV was 4.7+/-3.2 h x day(-1) in group I and 4.9+/-3.5 h x day(-1) in group II, and the nurse time consumption dropped significantly: the duration of NIPSV sessions and the nurse time consumption per session were respectively 44+/-10 and 7+/-4 min in group I, and 47+/-14 and 7+/-3 min in group II. Between the first 24 h and the subsequent period of 24 h, the nursing time dropped significantly (98 versus 59 min in group I (p<0.05), and 85 versus 52 min in group II (p<0.05)). There was no difference in the duration of NIPSV sessions, or in the overall assistance time per session, between the two groups of patients. In conclusion, the study seems to favour a quite low assistance time spent by nurses in relation to ventilatory time when noninvasive pressure support ventilation is used in chronic obstructive pulmonary disease patients with either acute exacerbations or postextubation hypercapnic respiratory insufficiency.

Effect of ED management on ICU use in acute pulmonary edema

Acute pulmonary edema (APE) is a common Emergency Department (ED) presentation requiring admission to an intensive care unit (ICU). This study was undertaken to examine the effect of ED management on the need for ICU admission in patients with APE. ED records of APE patients were abstracted for patient age, prehospital and ED pharmacological treatment, diagnoses, airway interventions, and ICU length of stay (LOS). Statistical analysis was through multiple regression, logistic regression, chi-square, and ANOVA. One hundred eighty-one patients composed the study group. Pharmacological treatment included nitroglycerin (NTG), 147 patients (81%); morphine sulfate (MS), 88 (49%); loop diuretics (LD), 133 (73%); and captopril sublingual (CSL), 47 (26%). Use of CSL and MS were associated with opposing needs for ICU admission. MS use was associated with increased ICU admissions (odds ratio, 3.08; P = .002), whereas CSL use was associated with decreased ICU admissions (odds ratio, 0.29; P = .002). Morphine sulfate use also demonstrated an increased need for endotracheal intubation (ETI) (odds ratio, 5.04; P = .001), whereas CSL demonstrated a decreased need for ETI (odds ratio, 0.16; P = .008). Ninety-three patients required some form of respiratory support. Forty received noninvasive pressure support ventilation (NPSV) from a bilevel positive airway pressure system (BiPAP), and 60 received endotracheal intubation. Some patients received more than 1 form of respiratory support; all other patients received supplemental oxygen only. The ICU-LOS associated with different airway interventions were supplemental oxygen, 0.72 days; BiPAP, 1.48 days; and ETI, 3.70 days ( P < .001). Specific ED pharmacological interventions are associated with a decreased need for ICU admission and endotracheal intubation in acute pulmonary edema patients, whereas use of noninvasive pressure support ventilation correlates with a reduction in the ICU length of stay for patients who do require critical care admission.

ED hemodialysis for treatment of renal failure emergencies

Patients with chronic renal failure (CRF) are at risk for unique medical emergencies, many of which require hemodialysis for their definitive treatment. This study describes the use of emergency department (ED) hemodialysis in the management of CRF patients. A retrospective chart review was conducted of patients who underwent ED hemodialysis at a regional dialysis center between April 1994 and September 1996. Data were collected on presenting complaint, ED diagnosis, indication for hemodialysis, ED pharmacologic treatment, ED airway management, cardiovascular stability, and disposition. Fifty episodes of ED hemodialysis were identified in 37 different patients. Presenting complaints included: shortness of breath, 38 (69%); weakness, 8 (15%); chest pain, 3 (5%); and other, 6 (11%). ED diagnoses included: congestive heart failure, 36 (65%); hyperkalemia, 13 (24%); and other, 6 (11%). Indications for hemodialysis included: cardiovascular instability, 33 (38%); respiratory distress, 22 (26%); cardiac monitoring, 16 (19%), timing, 13 (15%); and other, 2 (2%). Predialysis stabilization included: nitroglycerin, 29 (26%); sublingual captopril, 17 (15%); calcium chloride, 13 (11%); sodium bicarbonate, 12 (11%); insulin/dextrose, 11 (10%); none, 12 (11%); and other, 18 (16%). Airway support included: noninvasive pressure support ventilation (NPSV), 9 (18%); and endotracheal intubation, 6 (12%). NPSV was provided with a bilevel positive airway pressure system. Three of the endotracheal intubation patients were weaned to NPSV during dialysis, and all NPSV patients were weaned from respiratory support during their hemodialysis in the ED. Some patients had more than one problem. Sixteen patients (32%) were admitted, while 34 (68%) were discharged, including 3 NPSV patients and 22 initially unstable patients. ED hemodialysis in conjunction with additional medical care is a useful emergency medicine technique that can prevent hospital admission in patients with acute renal emergencies.

The use of noninvasive pressure support ventilation for severe respiratory insufficiency due to pulmonary oedema.

Experimental use of noninvasive pressure support ventilation (NIPSV) in patients with severe pulmonary oedema who would have been intubated if noninvasive ventilation were not available. Open, prospective, within patients non comparative study. Internal intensive care unit (11 beds) at a university hospital. 29 patients with severe respiratory distress and confirmed pulmonary oedema. NIPSV was applied via a tight fitting face mask delivering between 13 and 24 cm H2O inspiratory airway pressure and 2 to 8 cm H2O expiratory airway pressure. One patient required endotracheal intubation. Mean plethysmographic oxygen saturation rose significantly within 30 min from 73.8+/-11 to 90.3+/-5%, while the oxygen supply was reduced from 7.3+/-3.7 to 5.1+/-3 l/min. Mean pH increased significantly (p<0.01) from 7.22+/-0.1 before NIPSV to 7.31+/-0.07 after 60 min of NIPSV. Partial pressure of carbon dioxide was 62+/-18.5 mmHg but decreased significantly within 60 min to 48.4+/-11.5 mm Hg. Heart rate and-blood pressure stabilised continuously during the observation time. Mean duration of NIPSV was 6 h 9 min (range 60 min to 24 h). There were no serious side effects. Four patients died from underlying diseases between 1 and 28 days after NIPSV. NIPSV is a highly effective technique with which to treat patients with severe cardiogenic pulmonary oedema.

Noninvasive pressure support ventilation (NIPSV) with face mask in patients with acute cardiogenic pulmonary edema (ACPE)

To assess (1) the short-term hemodynamic, respiratory and arterial blood gas effects of NIPSV in patients with ACPE who were likely to require endotracheal intubation, (2) the initial causes of failure and (3) the side effects and the difficulties of this technique. Uncontrolled, prospective clinical study. Teaching hospital intensive care unit. 26 consecutive patients with severe ACPE. Noninvasive ventilation via a face mask, using a pressure support mode (20.5+/-4.7 cm H2O), with an initial fractional inspired oxygen of 93.0+/-16% and a positive end-expiratory pressure of 3.5+/-2.3 cm H2O. The need to intubate the patients within 48 h was considered as a criterion of failure of the procedure. Clinical and biological parameters were measured at 15 and 30 minutes, 1 h and 2 h and at 1 h and 2 h, respectively. There were 5 (21%) failures and 21 (79%) successes. In both the success and the failure groups, clinical and blood gas parameters improved at the first measure. In the success group, within 15 min of the start of NIPSV, pulse oximetry saturation (SpO2) had increased from 84+/-12 to 96+/-4% (p<0.001), the respiratory rate (RR) had decreased from 36+/-5.3 to 22.4+/-4.9 breaths/ min (p<0.0001) and within 1 h the arterial oxygen tension and pH, respectively, had increased from 61+/-14 to 270+/-126 mm Hg (p<0.0001) and from 7.25+/-0.11 to 7.34+/-0.07 (p<0.01) and the arterial carbon dioxide tension (PaCO2) had decreased from 54.2+/-15 to 43.4+/-6.4 mm Hg (p<0.01). There were no statistical differences between the success and failure groups for the initial clinical parameters: SpO2, RR, heart rate, mean arterial pressure. The only differences between the success and failure groups were in the PaCO2 (54.2+/-15 vs. 32+/-2.1 mm Hg, p<0.001) and the creatine kinase (CPK) (176+/-149 vs. 1282+/-2080 IU/l, p<0.05); this difference in CPK activity was related to the number of patients who had an acute myocardial infarction (AMI) (4/5 in the failure group vs. 2/21 in the success group, p<0.05). All patients with AMI in the failure group died. Among patients in acute respiratory failure, those with severe ACPE could benefit from NIPSV if they are hypercapnic, but NIPSV should be avoided in those with AMI.

Noninvasive pressure support ventilation in COPD patients with postextubation hypercapnic respiratory insufficiency.

Patients with chronic obstructive pulmonary disease (COPD) who have been intubated and mechanically ventilated may prove difficult to wean. Noninvasive ventilation may be used in an attempt to avoid new endotracheal intubation. The efficacy of administration of noninvasive pressure support ventilation was evaluated in 30 COPD patients with postextubation hypercapnic respiratory insufficiency, compared with 30 historically matched control patients who were treated conventionally. Patients were included in the study if, within 72 h postextubation, they presented with respiratory distress, defined as the combination of a respiratory frequency >25 breaths x min(-1), an increase in the arterial carbon dioxide tension (Pa,CO2) of at least 20% compared with the value measured after extubation, and a pH <7.35. Noninvasive pressure support ventilation was effective in correcting gas exchange abnormalities. The use of noninvasive ventilation significantly reduced the need for endotracheal intubation: 20 of the 30 patients (67%) in the control group required endotracheal intubation, compared with only six of the 30 patients (20%) in the noninvasive-ventilation group (p<0.001). In-hospital mortality was not significantly different between the two groups, but the mean duration of ventilatory assistance for the treatment of the postextubation distress, and the length of intensive care unit stay related to this event, were both significantly shortened by noninvasive ventilation (p<0.01). In conclusion, noninvasive ventilation may be used in the management of patients with chronic obstructive pulmonary disease and postextubation hypercapnic respiratory insufficiency.

Noninvasive ventilation via bilevel positive airway pressure support in pediatric practice.

To evaluate the efficacy of bilevel positive airway pressure support in critically ill children with underlying medical conditions. Prospective, clinical study. Pediatric intensive care unit (ICU). Thirty-four patients (6 mos to 20 yrs, mean 11.06 +/- 0.9 yrs) with impending respiratory failure were enrolled in the study. All patients required airway or oxygenation/ventilation support (awake or asleep) and required admission to our pediatric ICU. Each patient served as his or her own control. Exclusion criteria were absent cough or gag reflex, multiple organ system failure, age of <6 mos, vocal cord paralysis, and noncooperation with nasal mask. Bilevel positive airway pressure support ventilation. Thirty-four patients with 35 episodes of respiratory insufficiency requiring airway support or oxygenation/ventilatory support were treated with bilevel positive airway pressure support ventilation. Dyspnea score decreased at least two deviations in all patients; dyspnea score decreased five deviations in 67% of patients. Resting heart rate decreased from 126 +/- 3.2 to 102 +/- 3.2 beats/min (p < .001), respiratory rate decreased from 39 +/- 3 to 25 +/- 1 breaths/min (p < .004), bicarbonate concentrations decreased from 30.0 +/- 1.0 to 24.0 +/- 0.7 mmol/L (p < .01), and room air saturation increased from 85 +/- 2% to 97 +/- 1%. Bilevel positive airway pressure support ventilation failure was characterized by an inability to stabilize progression of respiratory failure and the subsequent placement of an artificial airway. Three patients required placement of an artificial airway. A decrease in respiratory rate, heart rate, and dyspnea score and an improvement in oxygenation were noted in >90% of patients studied, resulting in only an 8% frequency of intubation. The efficacy of bilevel positive airway pressure support ventilation in selected groups of patients indicates the need to include this form of noninvasive pressure support ventilation in the care offered by pediatric ICUs.