Original Article
Reversal of Acute Exacerbations of Chronic Obstructive Lung Disease by Inspiratory Assistance with a Face Mask
N Engl J Med 1990; 323:1523-1530November 29, 1990
- Abstract
- Abstract
Background.
Patients with acute exacerbations of chronic obstructive pulmonary disease may require endotracheal intubation with mechanical ventilation. We designed, and here report on the efficacy of, a noninvasive ventilatory-assistance apparatus to provide inspiratory-pressure support by means of a face mask.
Methods.
We assessed the short-term (45-minute) physiologic effects of the apparatus in 11 patients with acute exacerbations of chronic obstructive pulmonary disease and evaluated its therapeutic efficacy in 13 such patients (including 3 of the 11 in the physiologic study) who were treated for several days and compared with 13 matched historical-control patients.
Results.
In the physiologic study, after 45 minutes of inspiratory positive airway pressure by face mask, the mean (±SD) arterial pH rose from 7.31±0.08 to 7.38±0.07 (P<0.01), the partial pressure of carbon dioxide fell from 68±17 mm Hg to 55±15 mm Hg (P<0.01), and the partial pressure of oxygen rose from 52±12 mm Hg to 69±16 mm Hg (P<0.05). These changes were accompanied by marked reductions in respiratory rate (from 31±7 to 21±9 breaths per minute, P<0.01).
Only 1 of the 13 patients treated with inspiratory positive airway pressure needed tracheal intubation and mechanical ventilation, as compared with 11 of the 13 historical controls (P<0.001). Two patients in each group died. As compared with the controls, the treated patients had a more transient need for ventilatory assistance (3±1 vs. 12±11 days, P<0.01) and a shorter stay in the intensive care unit (7±3 vs. 19±13 days, P<0.01).
Conclusions.
Inspiratory positive airway pressure delivered by a face mask can obviate the need for conventional mechanical ventilation in patients with acute exacerbations of chronic obstructive pulmonary disease. (N Engl J Med 1990; 323:1523–30.)
Media in This Article
Figure 1
Schematic Representation of the Circuit Used to Deliver Inspiratory Assistance.Figure 2
Values for Arterial pH, Partial Pressure of Carbon Dioxide (PaCO2), and Partial Pressure of Oxygen (PaO2) in 11 Patients with Acute Exacerbations of Chronic Obstructive Pulmonary Disease, at Base Line and after 45 Minutes of Treatment with Inspiratory Positive Airway Pressure at either 12 (■) or 20 (□) cm of Water.Article Activity
- Article
PATIENTS in respiratory distress from acute exacerbations of chronic obstructive pulmonary disease often require endotracheal intubation and mechanical ventilation, both to restore adequate gas exchange and to alleviate respiratory-muscle fatigue.1 Both endotracheal intubation and mechanical ventilation have numerous complications,2 , 3 however, including nosocomial pneumonia, barotrauma, and tracheal injury. There is a need for methods of ventilatory assistance that could obviate the necessity for intubation in patients with acute respiratory failure. In chronic respiratory insufficiency, ventilation has been assisted noninvasively by means of external negative pressure,4 chest-wall oscillations,5 and positive-pressure ventilation administered through a mouthpiece6 or through the nose.7 , 8 Intermittent positive pressure through a nasal mask has also been used to treat some patients with acute respiratory failure.9 , 10 All these techniques are difficult to use routinely in patients with acute respiratory failure, however, and they require cooperation from the patient to decrease respiratory-muscle activity.
Inspiratory-pressure support is a new method of partial ventilatory assistance in which constant positive pressure is applied during the patient's spontaneous inspiration. This mode of support improves gas exchange and reduces respiratory-muscle work in intubated patients who are being weaned from mechanical ventilation.11 , 12 To introduce this technique into therapeutic use in nonintubated patients, we designed a simple device able to deliver inspiratory positive airway pressure through a face mask. This report describes the short-term physiologic effects of inspiratory positive airway pressure on gas exchange and respiratory-muscle work in 11 patients with chronic obstructive pulmonary disease and the therapeutic use of the technique and its effects on morbidity and mortality in 13 patients with chronic obstructive pulmonary disease who had acute respiratory distress. We compared the results in the latter group with the results of conventional treatment in 13 matched historical-control patients.
Methods
The study protocols were approved by the ethical research committee of our hospital. Informed consent was given by all the patients participating in either the physiologic or the clinical study of inspiratory positive airway pressure, or by their next of kin.
Inspiratory Positive Airway Pressure
The inspiratory-assistance device functions on the basis of three principles (Fig. 1Figure 1
Schematic Representation of the Circuit Used to Deliver Inspiratory Assistance.). First, during the patient's spontaneous inspiration, positive pressure is generated by a jet of compressed air. The injection of gas through a tube open to the atmosphere generates a positive pressure in the circuit because of the entrainment of air.13 Therefore, the patient inspires from the pressurized circuit. The airway pressure remains roughly constant over a widely ranging flow of inspired air (for instance, it varies only from 15 to 12 cm of water when the inspired flow increases from 0 to 1.5 liters per second). Second, the beginning and end of the patient's inspiration are sensed by a hot wire—calibrated pneumotachygraph placed on the inspiratory limb of the circuit. An inspiratory flow of 30 ml per second triggers the positive-pressure assistance, which is driven by an electronic valve. The pressure assistance stops when the inspired flow falls below a threshold level that can be adjusted. Third, expiration is not assisted and takes place through an expiratory tube that is separated from the inspiratory line by a pneumatic valve.The inspiratory assistance was delivered to the patients through a face mask (Bird, Palm Springs, Calif.) that was filled with silicon to minimize dead space. Special care was taken to avoid air leaks, and for some patients thin pieces of foam rubber were used to adjust the face mask for a tighter fit. Even when air leakage occurred, however, we found that the inspiratory assistance was delivered correctly, for two reasons: first, it is triggered at a time when the pressure of the mouth is low, and therefore no air leaks occur; second, the airway pressure remains constant despite substantial leakage throughout inspiration due to the intrinsic characteristics of the air-entrainment process.13
Throughout the study, oxygen was delivered to all the patients at a flow rate of 1 liter per minute through a standard nasal oxygen catheter; during the delivery of inspiratory positive airway pressure, the flow of supplemental oxygen was maintained by passing the catheter through a special adapter in the mask. Positioning and setting up the device required less than five minutes.
Physiologic Effects of Inspiratory Positive Airway Pressure
Eleven patients were selected for the physiologic study. All had a previously documented diagnosis of chronic obstructive pulmonary disease or a history of smoking and chronic bronchitis (Table 1Table 1
Characteristics of the Patients with Chronic Obstructive Pulmonary Disease Who Participated in the Physiologic Study.*) in addition to acute exacerbations of their lung disease as defined by the presence of at least three of the following: a recent and rapid worsening of dyspnea, a respiratory rate of 30 or more breaths per minute, an arterial pH of 7.38 or less, and an arterial partial pressure of oxygen below 55 mm Hg when the patient breathed room air. Five of the 11 patients had been treated for two to four days with bronchodilators and antibiotics.The patients were each asked to choose the most comfortable position with regard to minimizing their breathlessness; five patients adopted a semirecumbent position, three sat on their beds, and three sat in armchairs with their arms resting on a table. After the application of topical anesthesia, a double-lumen esophageal catheter with two thin latex balloons was inserted through the nose and advanced until the distal balloon was in the stomach and the proximal balloon was in the middle portion of the esophagus. In four patients, diaphragmatic electromyographic activity was also recorded by an esophageal electrode. Two patients were unable to swallow the catheter.
An arterial line was inserted in all patients, and a 30-minute period of spontaneous breathing was allowed to elapse. The basal respiratory rate and diaphragmatic activity were measured during this period, and two samples of arterial blood were taken for blood gas analysis. At the end of this 30-minute period, the face mask was applied and connected to a heated and calibrated pneumotachygraph (Fleisch number 1, Zurich, Switzerland) for 3 minutes for the measurement of resting tidal volume, respiratory rate, and minute ventilation. Inspiratory positive airway pressure was then delivered to the patient for 45 minutes. The pressure was set at 12 cm of water for five patients (Patients 4, 6, 7, 8, and 10; see Table 1) and at 20 cm of water for the other six patients (Patients 1, 2, 3, 5, 9, and 11). The patients were not asked to breathe in a specific pattern but were told that the positive-pressure assistance could be stopped at any moment on request. The clinical status of the patients was monitored carefully throughout the delivery of the pressure. The recordings of pneumotachygraphic and diaphragmatic activity were started again after 20 and 40 minutes for 5 minutes for subsequent analysis, and a sample of arterial blood was taken after 45 minutes for blood gas analysis.
Measurements
When the elastic equilibrium point of the respiratory system is not reached at the end of an expiration, the alveolar pressure remains positive, and inspiration cannot start until the inspiratory muscles have counteracted this positive pressure, which is referred to as the auto-positive end-expiratory pressure14 or the intrinsic positive end-expiratory pressure.15 We calculated this value from esophageal pressure tracings made during both the control period and the period of treatment with inspiratory positive airway pressure, as the amount of negative deflection that occurred before the beginning of inspiration.12
Diaphragmatic function was assessed by two measurements: those of transdiaphragmatic pressure and electromyographic activity. To measure transdiaphragmatic pressure, the esophageal and gastric pressures were used to estimate the pleural and abdominal pressures, respectively. The esophageal and gastric balloons were connected to a differential pressure transducer (MP45, Validyne, Northridge, Calif.; range, ±70 cm of water) after adequate positioning of the esophageal balloon had been verified by an occlusion test.16 , 17 The difference between the esophageal and the gastric pressure was considered to represent the transdiaphragmatic pressure. Variations in transdiaphragmatic pressure were calculated as the difference between the end-inspiratory and the peak expiratory values. The catheters recording gastric and esophageal pressure were also connected separately to a differential pressure transducer (SDX001, Sensym, Santa Clara, Calif.; range, ±70 cm of water), and the pressure tracings were recorded on a strip-chart recorder (Brush 260, Gould, Cleveland).
The pressure—time product for the diaphragm was calculated as the product of the mean transdiaphragmatic pressure and the duration of diaphragmatic inspiratory activity — i.e., the period during which the transdiaphragmatic pressure remained above the base line.18 The mean transdiaphragmatic pressure was calculated by averaging the values for pressure obtained every 200 msec during the inspiratory phase. The pressure—time product was used as an index of inspiratory-muscle activity, since it has been shown to be correlated with the oxygen consumption of respiratory muscle.19
The electromyographic activity of the diaphragm was recorded with a DISA 13K63 bipolar esophageal electrode (DISA, Copenhagen, Denmark) tapered at the nose.20 The signal was band-pass filtered between 20 Hz and 1 MHz, rectified, and electronically integrated with a leaky integrator with a time constant of 0.1 second (Gould). Diaphragmatic electromyographic amplitude was expressed in arbitrary units. The value for each variable was the average of the values recorded for at least 10 breaths.
Clinical Study
The therapeutic efficacy of inspiratory positive airway pressure was assessed by comparing the outcomes in 13 patients receiving this treatment with the outcomes in 13 matched historical-control patients receiving conventional therapy, including mechanical ventilation.
Study and Control Groups
Thirteen patients admitted for acute exacerbations of chronic obstructive pulmonary disease and for whom the device was available continuously during their hospitalizations were treated with inspiratory positive airway pressure for several days with the aim of providing sufficient ventilatory support to avoid the need for endotracheal intubation. Three of these patients had participated beforehand in the physiologic study. The attending physicians in the intensive care unit considered all these patients likely to require intubation and mechanical ventilation either immediately or after a short period of observation if no clinical improvement occurred. The indications for mechanical ventilation included clinical deterioration (with encephalopathy in five patients) and gradual worsening of gas exchange, leading to severe hypercapnia and respiratory acidosis, despite adequate therapy with bronchodilators and oxygen. Ten of these patients had paradoxical abdominal motion, and all 13 used the accessory respiratory muscles of the neck during inspiration.
The control patients were selected from among a group of 47 patients admitted to the intensive care unit in the two preceding years with a diagnosis of acute respiratory failure in addition to that of chronic obstructive pulmonary disease, no other diagnosis, and no history of use of mechanical ventilation at home.
For each patient treated with inspiratory-pressure support, a matching control patient was selected according to the following criteria: arterial pH on admission within 0.03 of the value for the treated patient; severity of illness on admission within two points, as assessed by the simplified acute physiologic score21; arterial partial pressure of carbon dioxide on admission within 5 mm Hg of the value for the treated patient when that value was <70 mm Hg and within 10 mm Hg when the value was ≥70 mm Hg; and age within 10 years of that of the treated patient. In matching each patient, we gave priority to pH and the simplified acute physiologic score, since the decision to undertake endotracheal intubation was generally made very early and was dependent on the initial severity of illness. The 13 control patients were all exactly matched to the treated patients with respect to pH, simplified acute physiologic score, and partial pressure of carbon dioxide. Ten patients were matched exactly with respect to age. For the three remaining patients such matching was not possible, and thus we selected three control patients who were younger than the patients receiving inspiratory positive airway pressure (74 as compared with 86 years, 58 as compared with 77, and 51 as compared with 70).
The comparability of the two groups was assessed on the basis of the ratio of the partial pressure of oxygen to the inspired fraction of oxygen (the PaO2/FiO2 ratio), the plasma bicarbonate level on admission, the sex ratio, and the number of previous hospitalizations in the intensive care unit. Arterial blood gas values at the time of discharge from the intensive care unit were also analyzed to ensure that the patients were similar. The use of drugs, including bronchodilators, antibiotics, corticosteroids, and diuretics, was also compared in the two groups.
Statistical Analysis
In the physiologic study, the values at base line and after treatment with inspiratory positive airway pressure were compared by a paired two-tailed t-test, or a Wilcoxon test in the case of small samples.
In the therapeutic study, the number of patients requiring intubation and mechanical ventilation, the mean duration of ventilatory assistance, the length of stay in the intensive care unit, and the mortality were compared between the two groups. A standard two-tailed t-test and a chi-square test with Yates' correction were used to compare the two groups.
Results
Physiologic Effects of Inspiratory Positive Airway Pressure
All the patients tolerated the delivery of inspiratory positive airway pressure with the device and completed the short-term study. During treatment, most of the patients had similar responses with respect to breathing pattern, gas exchange, and diaphragmatic activity, as shown in Figures 2Figure 2
Values for Arterial pH, Partial Pressure of Carbon Dioxide (PaCO2), and Partial Pressure of Oxygen (PaO2) in 11 Patients with Acute Exacerbations of Chronic Obstructive Pulmonary Disease, at Base Line and after 45 Minutes of Treatment with Inspiratory Positive Airway Pressure at either 12 (■) or 20 (□) cm of Water. and 3Figure 3
Values for Respiratory Rate, Tidal Volume, Minute Ventilation, and Transdiaphragmatic Pressure in 11 Patients with Acute Exacerbations of Chronic Obstructive Pulmonary Disease, at Base Line and after 45 Minutes of Treatment with Inspiratory Positive Airway Pressure at either 12 (■) or 20 (□) cm of Water.. Since the results were similar after 20 and 40 minutes of treatment, we averaged the values for the two periods. After 45 minutes of treatment with the pressure set at 12 or 20 cm of water, the mean (±SD) arterial pH rose from 7.31±0.08 to 7.38±0.07 (P<0.01), the partial pressure of carbon dioxide fell from 68±17 to 55±15 mm Hg (P<0.01), and the partial pressure of oxygen rose from 52±12 to 69±16 mm Hg (P<0.05) (Fig. 2). The respiratory rate decreased (from 31±7 to 21±9 breaths per minute, P<0.01), and the expired tidal volume increased from 289±93 to 596±210 ml (mean increase, 106 percent; range, 45 to 332 percent; P<0.01). Despite the decrease in respiratory rate, minute ventilation increased significantly during treatment in the seven patients in whom it could be measured without detectable leakage from the face mask. Diaphragmatic activity as measured by the transdiaphragmatic pressure decreased markedly during treatment with inspiratory positive airway pressure (Fig. 3) in the nine patients in whom it could be assessed (from 19.1±5.4 to 10.1±5.5 cm of water, P<0.01) (Fig. 3), and the pressure—time product for the diaphragm decreased by a mean of 36 percent. The individual values for pressure—time product and intrinsic positive end-expiratory pressure are shown in Table 2Table 2
Intrinsic Positive End-Expiratory Pressure (PEEP) and Pressure—Time Index in Nine Patients with Chronic Obstructive Pulmonary Disease, at Base Line and after 45 Minutes of Treatment with Inspiratory Positive Airway Pressure.. The mean amplitude of the averaged diaphragmatic electromyographic signal decreased by 50, 32, 53, and 38 percent in the four patients in whom it was measured, whereas the transdiaphragmatic pressure fell concomitantly by 39, 54, 40, and 50 percent, respectively. The recordings for a representative patient are shown in Figure 4Figure 4
Recordings for a Representative Patient during the Control Period and after 45 Minutes of Treatment with Inspiratory Positive Airway Pressure..The effects of setting the inspiratory positive airway pressure at 12 or 20 cm of water were quantitatively different. The decreases in respiratory rate (16±9 vs. 3±2 fewer breaths per minute, P<0.05) and in partial pressure of carbon dioxide (a decrease of 21±10 vs. 4±3 mm Hg, P<0.05) were larger when a pressure of 20 cm of water was used than with a pressure of 12 cm of water. The decrease in transdiaphragmatic pressure also tended to be larger with a pressure of 20 cm of water (11.2±1.9 vs. 7.2±2.2 cm of water, P = 0.08). Therefore, at 20 cm of water both respiratory-muscle activity and gas exchange were considerably improved. The fall in respiratory rate correlated with the fall in partial pressure of carbon dioxide.
One of the five patients receiving treatment at a pressure of 12 cm of water felt more comfortable during the treatment period than during the control period, whereas for the four others the level of comfort was similar during both periods. Of the six patients receiving treatment at a pressure of 20 cm of water, four patients with a normal state of consciousness felt more comfortable during the treatment period than during the control period.
Clinical Study
Intermittent treatment with inspiratory positive airway pressure was instituted at a level of pressure of 20 cm of water in the 13 patients. The periods of treatment were repeated for as many days as the number of days on which intubation would have been clinically necessary if no assistance with inspiratory positive airway pressure had been available. The number of days during which treatment was administered ranged from two to eight, and the mean number of hours of treatment per day for each patient was 7.6±3.9. Improvements in the design of the mask (the provision of an external solid surface and an internal foam-rubber surface, and a reduction in the amount of dead space) allowed us to increase the duration of the treatment periods from 3 to 6 hours for the first five patients to 8 to 12 hours for the remaining eight patients. The treatment was interrupted for a few minutes as required to allow the patient to expectorate or drink. The mask initially used tended to cause skin lesions due to pressure, but the modified mask was tolerated well by the eight patients who used it, and they were often able to sleep for short periods during treatment. The periods of spontaneous breathing without assistance lasted from three to six hours. The usual treatment was administered, including bronchodilators, antibiotics, steroids, and continuous oxygen therapy, but no treatment was given in aerosolized form.
The treatment patients and the control patients were similar with regard to the measures used for matching, their initial PaO2/FiO2 ratios and plasma bicarbonate concentrations, and their arterial blood gas values at discharge from the intensive care unit (Tables 3Table 3
Characteristics of and Outcomes in the 13 Patients with Chronic Obstructive Pulmonary Disease Treated with Inspiratory Positive Airway Pressure and the 13 Control Patients Receiving Conventional Treatment.* and 4Table 4
Physiologic Measurements on Admission and at Discharge in the 13 Patients with Chronic Obstructive Pulmonary Disease Treated with Inspiratory Positive Airway Pressure and the 13 Control Patients Receiving Conventional Treatment.*). Six patients in each group had been hospitalized previously in an intensive care unit for acute respiratory distress. In the treatment group, 8 patients received antibiotics, 12 received bronchodilators, 2 received corticosteroids, and 5 received diuretics. In the control group, 11 patients received antibiotics, 11 received bronchodilators, 3 received corticosteroids, and 6 received diuretics (P not significant).One patient underwent intubation and treatment with mechanical ventilation on day 3 because of the apparent lack of efficacy of inspiratory positive airway pressure. During intubation he had transient ventricular arrhythmia, and a second episode occurred a few hours later that led to cardiac arrest and death. Another patient in the treatment group had a cardiac arrest after 10 days of hospitalization, when she was considered to be clinically improved. All the other patients were treated successfully with inspiratory positive airway pressure and were discharged from the intensive care unit. Thus, only one patient in the treatment group received mechanical ventilation, whereas 11 of the 13 patients receiving conventional therapy underwent intubation and mechanical ventilation (P<0.001) (Table 3). The mean duration of assistance was 3±1 days (range, 2 to 8) in the 11 patients in the treatment group who had favorable outcomes, as compared with 13±11 days (range, 16 to 35) in the 11 patients in the control group who had favorable outcomes, including 2 nonintubated patients and 2 patients who were discharged to receive mechanical ventilation at home (P<0.01). Mortality was similar in the two groups. The length of stay in the intensive care unit was substantially shorter in the treatment group (7±3 vs. 19±12 days, P<0.01).
Discussion
This study demonstrates that an external inspiratory-assistance device can improve gas exchange efficiently and reduce respiratory-muscle work in patients with acute exacerbations of chronic obstructive pulmonary disease. It also suggests that the treatment with inspiratory positive airway pressure can prevent endotracheal intubation in many patients and reduce the length of stays in the intensive care unit.
Mechanical ventilation is often required in patients with chronic obstructive pulmonary disease who have acute respiratory failure. It is usually delivered through an endotracheal tube or a tracheostomy cannula, but the morbidity associated with these techniques3 has led to the development of noninvasive devices to improve ventilation.4 5 6 7 8 9 10 Positive-pressure ventilation with a nasal mask has proved successful in selected cases of acute respiratory insufficiency.9 , 10 During periods of acute respiratory distress, however, patients with chronic obstructive pulmonary disease generally breathe through their mouths, and initial attempts to deliver assistance to such patients through a nasal mask resulted in massive leaks of insufflated air from the mouth. Conversely, the use of a mouthpiece requires the patient's cooperation, which limits its usefulness in patients with respiratory distress.
Inspiratory-pressure support is a new method of ventilatory assistance designed to deliver an even level of positive pressure during spontaneous inspiration by intubated patients.11 , 12 This type of assistance reduces both the effort of breathing and the cost in oxygen in proportion to the level of pressure used, whereas gas exchange is improved by the increased alveolar ventilation.11 , 12 , 22 The patient's spontaneous inspiratory activity regulates the frequency and duration of the inspiratory assistance.11 , 12 , 22 In nonintubated patients, we found that the ventilators in current use had serious limitations, because of poor sensitivity of the demand valve, inability to maintain an even pressure, and high expiratory resistance; furthermore, such ventilators are very costly. This prompted us to design an inexpensive, easily handled apparatus with a high triggering sensitivity, the ability to deliver a constant positive pressure during inspiration, and a low level of expiratory resistance. All these features are apparent in the tracings in Figure 4.
It is important to stress the differences between inspiratory positive airway pressure and intermittent positive-pressure breathing, which is similar in some ways.23 First, airway pressure mostly depends on the patient's demand for air during intermittent positive-pressure breathing, and its effects are therefore very different in relaxed patients and those breathing actively.24 25 26 We demonstrated previously that under conditions of high inspiratory effort, only inspiratory positive airway pressure, not intermittent positive-pressure breathing, could reduce the effort of breathing.27 A second feature of intermittent positive-pressure breathing is that inspiration stops when a preset airway pressure is reached; this characteristic can induce active expiratory effort by the patient that can be deleterious.28 Conversely, during inspiratory positive airway pressure, the assistance is cycled according to the inspiratory flow and stops before the flow drops to zero. Therefore, no expiratory effort is required from the patient.
During treatment with inspiratory positive airway pressure, alveolar ventilation improved, whereas respiratory-muscle activity decreased. Several factors, including variations in lung volume, may affect the measurement of transdiaphragmatic pressure.29 , 30 We found no significant changes in values for intrinsic positive end-expiratory pressure, which serve to quantify dynamic hyperinflation. During the delivery of inspiratory positive airway pressure, we also found a marked drop in the pressure—time product for the diaphragm — probably an accurate reflection of its energy expenditure.19 , 31 In addition, recordings of diaphragmatic electromyographic activity in four patients showed concomitant decreases in transdiaphragmatic pressure and electromyographic activity. This demonstrates that there is a reduction in the central respiratory drive during treatment with inspiratory positive airway pressure that allows the respiratory muscles to rest.
When inspiratory positive airway pressure was used as a therapeutic measure, we found that intubation and mechanical ventilation could be avoided in most patients, whereas 11 of 13 matched historical-control patients with chronic obstructive pulmonary disease who were comparably ill on admission required intubation and mechanical ventilation. The patients in the two groups were well matched, especially in regard to severity scores and two measures of respiratory failure — arterial pH and partial pressure of carbon dioxide.32 Furthermore, the PaO2/FiO2 ratio, the number of previous hospitalizations in the intensive care unit for decompensation of chronic obstructive pulmonary disease, and the plasma bicarbonate concentration on admission (a reflection of the degree of chronic hypercapnia) were similar in the two groups. We thus assume that the patients in the two groups were comparable with regard to the severity of both their underlying respiratory disease and the short-term decompensation.
The inspiratory-assistance device was well accepted by the patients, and its use was limited only by the ability to tolerate the face mask. No side effects were noted during this study, and with the pressure below a level of 25 cm of water we did not observe inflation of the stomach. Because the mask was tolerated well, treatment could be continued for several days until the patient's condition improved. The use of inspiratory positive airway pressure was associated with a significantly reduced duration of ventilatory assistance and length of stay in the intensive care unit, as compared with those observed with conventional therapy. The process of weaning from mechanical ventilation is often slow and difficult in patients recovering from acute exacerbations of chronic obstructive pulmonary disease.33 Avoiding tracheal intubation and mechanical ventilation in our treatment group spared the patients such prolonged periods of weaning, probably explaining our results.
The mechanical, gasometric, and clinical effects of inspiratory positive airway pressure delivered by a face mask warrant further trials, because this treatment may eliminate the need for intubation in many patients with chronic obstructive pulmonary disease who have acute respiratory distress.
Presented in part at the annual meeting of the American Thoracic Society, May 8–11, 1988, Us Vegas.
We are indebted to Mr. Daniel Zalkin and Air Liquide Industrie for their technical assistance in the development of the inspiratory-assistance device and to Mrs. Nadine Bedfert for assistance in the preparation of the manuscript.
Source Information
From the Medical Intensive Care Unit, Department of Physiology and INSERM Unité 296, University of Paris XII, Henri Mondor Hospital, Créteil, France. Address reprint requests to Dr. Brochard at the Service de Réanimation Médicale, Hôpital Henri Mondor, 94010 Créteil Cédex, France.
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Saoussen Dimassi, Frédéric Vargas, Aissam Lyazidi, Ferran Roche-Campo, Jean Dellamonica, Laurent Brochard. (2011) Intrapulmonary percussive ventilation superimposed on spontaneous breathing: a physiological study in patients at risk for extubation failure. Intensive Care Medicine 37:8, 1269-1276
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Mostafa Ghanei, Mohsen Rajaeinejad, Rouzbeh Motiei-Langroudi, Farshid Alaeddini, Jafar Aslani. (2011) Helium:oxygen versus air:oxygen noninvasive positive-pressure ventilation in patients exposed to sulfur mustard. Heart & Lung: The Journal of Acute and Critical Care 40:3, e84-e89
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