Noninvasive ventilation in acute respiratory failure

Noninvasive PPV has been employed for decades in patients with chronic respiratory failure. Increasing use in patients with acute respiratory failure is a more recent phenomenon, mainly because of advances in noninvasive interfaces and ventilator modes. Noninvasive PPV delivered by nasal or oronasal mask has been demonstrated to reduce the need for endotracheal intubation, decrease lengths of stay in the ICU and hospital, and possibly reduce mortality. In the acute care setting, evidence now demonstrates the efficacy of noninvasive PPV for acute exacerbations of COPD, pulmonary edema, pulmonary contusions, and acute respiratory failure in patients who decline or who are not believed to be candidates for intubation. No firm conclusions can yet be made regarding patients with respiratory failure due to other causes, but studies suggest that noninvasive PPV may also be of benefit in patients with postoperative respiratory insufficiency, chest wall disease, and cystic fibrosis. Several factors are vital to the success of this therapy, including careful patient selection, properly timed intervention, a comfortable, well-fitting interface, patient coaching and encouragement, and careful monitoring. Noninvasive ventilation should be used as a way to avoid endotracheal intubation rather than as an alternative. Accordingly, a trial of noninvasive ventilation should be instituted in the course of acute respiratory failure before respiratory arrest is imminent, to provide ventilatory assistance while the factors responsible for the respiratory failure are aggressively treated. Moreover, the authors favor conservative management with expeditious intubation in patients who have other conditions that place them at risk during use of noninvasive ventilation or in patients failing to respond to noninvasive PPV. Noninvasive PPV clearly represents an important addition to the techniques available to manage patients with acute respiratory failure; however, because most studies have been retrospective and uncontrolled, many issues remain unresolved. Further controlled studies are needed to confirm the safety and efficacy of noninvasive PPV, evaluate the most appropriate selection of patients and timing of intervention, define the best type of interface, and assess the costs of noninvasive PPV in comparison with conventional therapy.     

Noninvasive ventilation in intensive care

Non-invasive ventilation has been in use for many years to provide long-term home ventilatory support to patients with chronic respiratory failure. In recent years, it has emerged on the intensive care scene as a means of avoiding intubation in acute respiratory failure. The results of several studies indicate that such an approach can lead to a reduction in mortality and duration of hospital stay compared to conventional mechanical ventilation with endotracheal intubation. The purpose of this article is to explore the various ventilatory techniques available, the choice of respirator and ventilatory mode in various clinical conditions, and to discuss some of the logistics involved in the optimal use of this technique.     

A comparison of noninvasive positive-pressure ventilation and conventional mechanical ventilation in patients with acute respiratory failure

BACKGROUND AND METHODS: The role of noninvasive positive-pressure ventilation delivered through a face mask in patients with acute respiratory failure is uncertain. We conducted a prospective, randomized trial of noninvasive positive-pressure ventilation as compared with endotracheal intubation with conventional mechanical ventilation in 64 patients with hypoxemic acute respiratory failure who required mechanical ventilation. RESULTS: Within the first hour of ventilation, 20 of 32 patients (62 percent) in the noninvasive-ventilation group and 15 of 32 (47 percent) in the conventional-ventilation group had an improved ratio of the partial pressure of arterial oxygen to the fraction of inspired oxygen (PaO2:FiO2) (P=0.21). Ten patients in the noninvasive-ventilation group subsequently required endotracheal intubation. Seventeen patients in the conventional-ventilation group (53 percent) and 23 in the noninvasive-ventilation group (72 percent) survived their stay in the intensive care unit (odds ratio, 0.4; 95 percent confidence interval, 0.1 to 1.4; P=0.19); 16 patients in the conventional-ventilation group and 22 patients in the noninvasive-ventilation group were discharged from the hospital. More patients in the conventional-ventilation group had serious complications (66 percent vs. 38 percent, P=0.02) and had pneumonia or sinusitis related to the endotracheal tube (31 percent vs. 3 percent, P=0.003). Among the survivors, patients in the noninvasive-ventilation group had shorter periods of ventilation (P=0.006) and shorter stays in the intensive care unit (P=0.002). CONCLUSIONS: In patients with acute respiratory failure, noninvasive ventilation was as effective as conventional ventilation in improving gas exchange and was associated with fewer serious complications and shorter stays in the intensive care unit.     

Outcomes of noninvasive positive-pressure ventilation in patients with acute hypercapnia complicating chronic respiratory failure]

We used noninvasive positive-pressure ventilation to treat hypercapnea due to acute exacerbations of chronic respiratory failure (21 episodes in 19 patients; COPD, 4; pulmonary tuberculosis sequelae, 4; silicosis, 3; silicotuberculosis, 3; bronchiectasis, 3; others, 2). All patients had acute onsets of severe hypercapnea (PaCO2 > 45 Torr), acute decreases in pH (< 7.35), and tachypnea, paradoxical breathing or both. During the first 2 to 4 hours of bi-level positive airway pressure, PaCO2 decreased from 72 to 61 Torr (p < 0.0005), pH increased from 7.26 to 7.31 (p < 0.001), and respiratory rate decreased from 30 to 25 breaths/min (p < 0.005). In three cases leakage of air through the mouth prevented improvement in the patients' conditions, but in two of those a face mask was then used successfully. In 17 of the 21 episodes (81%) gas exchange improved and intubation was not necessary. In those 17, the mean duration of noninvasive positive-pressure ventilation was 6.3 days. We conclude that noninvasive positive-pressure ventilation can improve gas exchange in patients with acute hypercapnea complicating chronic respiratory failure.     

Noninvasive positive pressure ventilation: what is its role in treating acute respiratory failure?

Noninvasive positive pressure ventilation (NIPPV) is a viable option in treating appropriately selected patients with acute respiratory failure. It is often well tolerated, and it avoids endotracheal intubation with its potential complications. Moreover, gas exchange is reportedly improved. Several issues relating to the use of NIPPV are unresolved, however. The optimal interface, best ventilator mode, and patient selection criteria have not been firmly established. Also, studies are needed to compare the efficacy, safety, and cost-effectiveness of NIPPV and standard endotracheal ventilation. Despite these unresolved issues, NIPPV clearly represents an important addition to the techniques available in managing acute respiratory failure. Except in situations in which immediate endotracheal intubation is required, it may become first-line therapy in elderly patients in whom resuscitation status is unsettled.     

Noninvasive mechanical ventilation in a patient with respiratory failure after hematopoietic progenitor transplantation

Respiratory failure requiring orotracheal intubation (OTI) and mechanical ventilation (MV) is almost always a fatal complication in patients who undergo hematopoietic progenitor transplantation (HPT). We present the case of a woman who suffered respiratory failure with bilateral infiltrates on a chest X-ray taken on day +14 following autologous bone marrow transplantation. We managed the patient satisfactorily with noninvasive ventilation, avoiding OTI. We believe that patients with non-progressive pulmonary lesions and without multiple system organ failure, may be correctly managed with noninvasive positive-pressure ventilation (NPPV).     

Rehabilitation of patients admitted to a respiratory intensive care unit

OBJECTIVE: Pulmonary rehabilitation has been shown to be of benefit to clinically stable patients with chronic obstructive pulmonary disease (COPD). This study examined the effect of pulmonary rehabilitation on some physiologic variables in COPD patients recovering from an episode of acute respiratory failure. DESIGN: A prospective, randomized study. SETTING: A respiratory intensive care unit (RICU). PATIENTS: Eighty COPD patients recovering from an episode of acute respiratory failure were randomized in a 3:1 fashion to receive stepwise pulmonary rehabilitation (group A, n=60 patients) or standard medical therapy (group B, n=20 patients). MAIN OUTCOME MEASURES: Improvements in exercise tolerance, sense of breathlessness, respiratory muscle function, and pulmonary function test values were measured, respectively, by exercise capacity (6-minute walking distance [6MWD]), dyspnea score (Visual Analog Scale [VAS]), maximal inspiratory pressure (MIP), forced expiratory volume in 1 second (FEV1), and forced vital capacity (FVC). INTERVENTIONS: Group A received pulmonary rehabilitation that consisted of passive mobilization (step I), early deambulation (step II), respiratory and lower skeletal muscle training (step III), and if the patients were able, complete lower extremity training on a treadmill (step IV). Group B received standard medical therapy plus a basic deambulation program. RESULTS: Sixty-one of 80 patients were mechanically ventilated at admission to the unit and most of them were bedridden. Twelve of the 60 group A patients and 4 of the 20 group B patients died during their RICU stay, and 9 patients required invasive mechanical ventilation at home after their discharge. The total length of RICU stay was 38+/-14 days for patients in group A versus 33.2+/-11 days for those in group B. Most patients from both groups regained the ability to walk, either unaided or aided. At discharge, 6 MWD results were significantly improved (p < .001) in Group A only. MIP improved in Group A only (p < .05), while VAS scores improved in both groups, but the improvement was more marked in group A (p < .001) than in group B (p < .05). CONCLUSIONS: COPD patients who were admitted to a RICU in critical condition after an episode of acute respiratory failure and who, in most cases, required mechanical ventilation benefited from comprehensive early pulmonary rehabilitation, compared with patients who received standard medical therapy and progressive ambulation.     

The microbiological profile of nosocomial infection in a respiratory intensive care unit

In 1987, in the Respiratory Intensive Care Unit of Santa Maria Hospital we developed a nosocomial surveillance program with specially created software that provides knowledge of NI in the ICU at any moment. The information gathered along the time is particularly useful in the correlation of the risk factors, the most frequent microorganisms and in the institution of empiric antibiotic therapy. Out of 2528 patients admitted in our ICU for the last 6 years (87/92), 10% had bacteriologically identified NI. Almost (93%) of them had occurred in mechanically ventilated patients, which corresponds to 20.7% NI in those patients. The gram-negative appeared in 63.37%, with the predominance of Enterobacteriaceae. From the gram-positives the most frequent were Staphylococcus spp. Their meticiline resistance was worrisome. NI patients had significantly higher severity and therapeutic intervention scores. Mechanical ventilation period was 4 fold higher and mortality 2.5 times higher in the patients with this complication.     

Expired gas monitoring by mass spectrometry in a respiratory intensive care unit

The application of a medical mass spectrometer for the monitoring of respired gases in the respiratory intensive care unit of a community hospital is reviewed. This monitoring system is routinely used with intubated patients for periodic monitoring of end-tidal CO2 tensions (PETCO2), FIO2, and PETO2 dead space to tidal volume ratios, and the determination of AaDO2; the value of these measurements is discussed. It is especially useful for continuous monitoring at critical points in the patient's course such as weaning from the ventilator, determining optimal ventilator settings, monitoring, unstable nonintubated patients, and in better defining the pathophysiological disturbances impeding patient progress, examples of which are presented. Preliminary observations suggest it may also provide a simple technique for determining optimal expiratory retard settings. The initial cost of such a system is justified by the benefit to the patient, i.e., reduction in the frequency of nonessential arterial blood gas determinations, shortened weaning period, and early detection of potentially dangerous trends. Technical problems encountered with this system and potential future uses are also discussed.     

Transesophageal echocardiography in patients treated with ventilation at a polyvalent intensive care unit

Transthoracic echocardiography (TTE) has a definite role in general ICUs where its indications are now generally accepted. Transesophageal echocardiography (TEE) has widened the diagnostic scope of ultrasonic and doppler technology, partly by resolving the physical limitations of TTE. In this article the authors comment on their series of TTEs and TEEs, pointing out advantages, the diagnostic and therapeutic implications, especially in artificially ventilated patients. They conclude by emphasising the need to establish TEE as a routine diagnostic tool in general ICUs.     

Comparison of noninvasive positive pressure ventilation with standard medical therapy in hypercapnic acute respiratory failure

STUDY OBJECTIVE: To compare the efficacy of standard medical therapy (ST) and noninvasive mechanical ventilation additional to standard medical therapy in hypercapnic acute respiratory failure (HARF). DESIGN: Single center, prospective, randomized, controlled study. SETTING: Pulmonary medicine directed critical care unit in a university hospital. PATIENTS: Between March 1993 and November 1996, 30 HARF patients were randomized to receive ST or noninvasive positive pressure ventilation (NPPV) in addition to ST. INTERVENTIONS: NPPV was given with an air-cushioned face via a mechanical ventilator (Puritan Bennett 7200) with initial setting of 5 cm H2O continuous positive airway pressure and 15 cm H2O pressure support. RESULTS: At the time of randomization, patients in the ST group had (mean+/-SD) PaO2 of 54+/-13 mm Hg, PaCO2 of 67+/-11 mm Hg, pH of 7.28+/-0.02, and respiratory rate of 35.0+/-5.8 breaths/min. Patients in the NPPV group had PaO2 of 55+/-14, PaCO2 of 69+/-15, pH of 7.27+/-0.07, and respiratory rate of 34.0+/-8.1 breaths/min. With ST, there was significant improvement of only respiratory rate (p < 0.05). However, with NPPV, PaO2 (p < 0.001), PaCO2 (p < 0.001), pH (p < 0.001), and respiratory rate (p < 0.001) improved significantly compared with baseline. Six hours after randomization, pH (p < 0.01) and respiratory rate (p < 0.01) in NPPV patients were significantly better than with ST. Hospital stay for NPPV vs ST patients was, respectively, 11.7+/-3.5 and 14.6+/-4.7 days (p < 0.05). One patient in the NPPV group required invasive mechanical ventilation. The conditions of six patients in the ST group deteriorated and they were switched to NPPV; this was successful in four patients, two failures were invasively ventilated. CONCLUSION: This study suggests that early application of NPPV in HARF patients facilitates improvement, decreases need for invasive mechanical ventilation, and decreases the duration of hospitalization.     

Noninvasive positive pressure ventilation via face mask. First-line intervention in patients with acute hypercapnic and hypoxemic respiratory failure

OBJECTIVES: We have previously reported our experience with noninvasive positive pressure ventilation (NPPV) via face mask in a small group of selected patients with acute respiratory failure (ARF). NPPV was frequently effective (70% success rate) in correcting gas exchange abnormalities and in avoiding endotracheal intubation (ETI); NPPV also had a low rate of complications. We have evaluated the clinical application of NPPV as first-line intervention in patients with hypercapnic and short-term hypoxemic ARF. A dedicated respiratory therapist conducted an educational program with physicians-in-training rotating through the medical ICUs of a university medical center and supervised implementation of a simplified management protocol. Over 24 months, 164 patients with heterogeneous forms of ARF received NPPV. We report on the effectiveness of NPPV in correcting gas exchange abnormalities, in avoiding ETI, and associated complications, in different conditions precipitating ARF. PATIENT POPULATION: One hundred fifty-eight patients completed the study. Forty-one had hypoxemic ARF, 52 had hypercapnic ARF, 22 had hypercapnic acute respiratory insufficiency (ARI), 17 had other forms of ARF, and 26 with advanced illness had ARF and refused intubation. Twenty-five percent of the patients developed ARF after extubation. INTERVENTION: Mechanical ventilation was delivered via a face mask. Initial ventilatory settings were continuous positive airway pressure (CPAP) mode, 5 cm H2O, with pressure support ventilation of 10 to 20 cm H2O titrated to achieve a respiratory rate less than 25 breaths/min and an exhaled tidal volume of 7 mL/kg or more. Ventilator settings were adjusted following arterial blood gases (ABG) results. RESULTS: The mean duration of NPPV was 25 +/- 24 h. When the 26 patients with advanced illness are excluded, NPPV was effective in improving or correcting gas exchange abnormalities in 105 patients (80%) and avoiding ETI in 86 (65%). Failure to improve ABG values was the reason for ETI in 20 of 46 (43%). The overall average predicted and actual mortality were 32% and 16%, respectively. Survival was 93% in non-intubated patients and 79% in intubated patients. NPPV was effective in lessening dyspnea throughout treatment in all but seven patients. Complications developed in 24 patients (16%). In patients with hypercapnic ARF, nonresponders had a higher PaCO2 at entrance (91.5 +/- 4.2 vs 80 +/- 1.5; p < 0.01). In patients with hypercapnic ARF and ARI, arterial blood gases response (pH and PaCO2) within 2 h of NPPV predicted success (p < 0.0001). None of the entrance parameters predicted need for ETI. CONCLUSIONS: We conclude that application of NPPV in clinical practice is an effective and safe alternative to ETI in many hemodynamically stable patients with hypercapnic ARF and in those with hypoxemic ARF in whom the clinical condition can be readily reversed in 48 to 72 h. An educational and supervision program is essential to successfully implement this form of therapy.     

Treatment costs in a medical intensive care unit: a comparison of 1992 and 1997

BACKGROUND AND OBJECTIVE: Treatment in an intensive care unit (ICU) is very expensive. Aim of this study was to determine the exact composition of costs and to analyse what factors are responsible for the rise in costs over the last 5 years. METHODS: In a prospective investigation all 790 patients who had been treated at the ICU of the Medical Department of Frankfurt University during 1992 were included, findings being compared with data on all 208 patients treated in the ICU in May and June 1997. All important diagnostic and therapeutic measures were quantitatively determined each day. RESULTS: The mean age of the ICU patients rose in the 5 years from 55 to 59 years (P < 0.001). Mean period of stay in the ICU remained unchanged (4.1 days), total duration of hospital stay (15 and 12 days, respectively), and treatment intensity (sum of points according to the "Therapeutic Intervention Scoring System" per ICU stay: 96 and 77, respectively). The mortality rate in the ICU fell from 16.3% to 10.6% (P = 0.02), hospital mortality rate from 23% to 14% (P = 0.01). Total cost rose from DM 797,860 to DM 1,148,945 per 100 patients (+44%). Of this total, personnel costs were DM 286,885 in 1992 and 356,091 in 1997 (+24%), costs for apparatus-based diagnostic and therapeutic tests were DM 169,743 and 245,156, respectively (+44%), DM 98,496 and 129,222 for drugs (+31%), and DM 60,399 and 186,671 (+209%) for blood and clotting products (in each category per 100 patients). Per case costs rose from DM 7970 to 11,489, per day costs from DM 1943 to 2831. 90% of cost increases were due to new strategies in the treatment of patients with myocardial infractions and those with severe clotting disorders and a rise in personnel costs. CONCLUSION: The costs of a stay in the ICU has greatly increased over the last 5 years, the main causes being a change to new forms of treatment, especially in patients with myocardial infarction and those with haemophilia.     

Nosocomial infections in a neurosurgical intensive care unit

The occurrence of nosocomial infections in 1017 consecutive patients seen in a neurosurgical intensive care unit (ICU), over a period of 18 months is reported. The frequency of infections is low, which may possibly be due partly to the short stay in the ICU. Close interdisciplinary cooperation is stressed as an important factor in limiting infections. BACKGROUND. The aim of this study was to analyse the nosocomial infections in a neurosurgical intensive care unit over a period of 18 months, emphasizing localization and cause of infection, in order to adapt treatment and to take preventive measures. From 15% to 27% of patients treated in ICUs acquire nosocomial infections. In Germany this means 500,000-800,000 patients a year, and the annual costs related to nosocomial infections are estimated at 1.7 billion Deutschmarks. PATIENTS AND METHODS. In all, 1017 consecutive patients were evaluated. The patients were divided into two groups, depending on the duration of treatment in the ICU: Patients who remained for less than 48 h (1017 patients) Patients who were treated for a period exceeding 48 h (314 patients) The evaluation was performed retrospectively from the medical documentation. Criteria for registration are those of the Centers for Disease Control (Atlanta 1988). When more than one infection was diagnosed, each was considered as a new infection, regardless of the bacteria involved. Among the 314 patients who were in the ICU for more than 48 h a total of 114 nosocomial infections were recorded. The frequency of infection referred to all patients treated during that time (n = 1017) was 11.2%, while the frequency among those who were treated for longer than 48 h was 36.3%. Most infections (38.6%) affected the respiratory tract, followed by infections of the urinary tract. Of the bacteria determined 56.7% were gram-negative. In this group E. coli was the most frequently found (29.8%). In the group of gram-positive bacteria, S. aureus was diagnosed in 56.3% of cases. Twelve (16%) of the infected patients died and lethality referred to all patients was 8.6%. DISCUSSION. Compared with other studies, this study revealed a low the infection rate, at 11.2%. This can be explained partly by the short stay in this ICU (mean 3.7 days) and partly by the retrospective method of registration and the particular medical characteristics of neurosurgical patients. The well-known general risk factors for infection, such as age, mechanical ventilation, continuous catheterization of the bladder, and long duration of stay, are also found in neurosurgical ICUs. It is quite difficult to determine to what extent nosocomial infections prolong the treatment necessitated by the primary neurosurgical disease. We were not able to extrapolate the influence of immunosuppressant treatment on the appearance of nosocomial infections, as almost all patients in this study were receiving steroids. This study underlines the necessity of interdisciplinary cooperation between neurosurgeons, anaesthesiologists, microbiologists and nurses in neurosurgical ICUs, where most patients staying longer than 48 h are immunosuppressed and ventilated and thereby particularly at risk of nosocomial infections.