Intermittent Negative Pressure Ventilation Research Articles

Historical Perspectives

Historical Perspectives

Feedback-Controlled Negative Pressure Ventilation in Patients with Stable Severe Hypercapnic Chronic Obstructive Pulmonary Disease

Background: In recent studies, the efficacy of intermittent rest of the inspiratory muscles as an option of treating patients with severe chronic obstructive pulmonary disease (COPD) has become questionable. Objective: The aim of our study was to analyze the effects of feedback-controlled intermittent negative pressure ventilation (INPV) on stable, but severely hypercapnic COPD patients. Methods: 21 clinically stable, hypercapnic patients with severe COPD underwent INPV with chest shells for 3 weeks, 6 h a day. The INPV sessions were optimized by a visual biofeedback system, which enabled control over the decrease in diaphragmatic activity. Respiratory muscle (RM) function parameters, lung function parameters, blood gases and exercise capacity were analyzed. Results: In the end, 19 patients concluded INPV treatment. They had PaO₂ of 56.5 ± 11.8 mm Hg, PaCO₂ of 50.2±2.7 mm Hg (mean ± SD) and FEV₁ of 27.8 ± 4.3% predicted before treatment. There was no statistically significant change in lung function parameters, RM function parameters, physical performance and level of dyspnea after 3 weeks of INPV. Conclusion: We conclude that intermittent RM rest induced by INPV can relax inspiratory muscles in most patients with stable severe COPD, but fails to improve RM function and exercise capacity.

Negative Pressure Ventilation vs External High-Frequency Oscillation During Rigid Bronchoscopy: A Controlled Randomized Trial

To compare the effectiveness of two modalities of external ventilation during rigid bronchoscopy: intermittent negative pressure ventilation (INPV) and external high-frequency oscillation (EHFO). Prospective, controlled, randomized, nonblinded study. University-affiliated hospital. Seventy patients undergoing interventional rigid bronchoscopy for tracheobronchial lesions were enrolled into the study. Mechanical ventilation was performed by INPV or EHFO. When pulse oximetry was < 90%, manually assisted ventilation was delivered. Arterial blood gases were sampled preoperatively and intraoperatively. Most patients in both groups had normal intraoperative PaCO(2) (mean, 43. 6 +/- 11.8 mm Hg under EHFO and 37.4 +/- 8.2 mm Hg under INPV; p = 0.012), and acidemia occurred in 9 of 35 patients of EHFO group and in 2 of 35 patients of INPV group (p = 0.049). Hypercapnia (PaCO(2) > 50 mm Hg) was observed in 10 patients under EHFO and in 2 with INPV (p = 0.026). Intraoperative mean PaO(2) was similar (101.4 +/- 52.9 mm Hg with EHFO and 124.2 +/- 50.3 mm Hg with INPV; p = 0.07), but O(2) supply was different (3.5 +/- 2.3 L/min during INPV and 8.5 +/- 6.2 L/min during EHFO; p < 0.001). Intraoperative hypoxemia (PaO(2) < 60 mm Hg) occurred in five patients with EHFO and two with INPV (p = 0.426). Three EHFO patients required manually assisted ventilation (mean, 0.2 +/- 0.9), but no INPV patient did (p = 0.142). External negative pressure ventilation appears to be a suitable choice during rigid bronchoscopy: both EHFO and INPV ensure effective ventilation and comfortable operating conditions in the majority of patients. Some patients may receive inadequate ventilation with EHFO, developing respiratory acidosis and requiring manually assisted ventilation. In comparison with INPV, EHFO requires a higher fraction of inspired oxygen.

Intermittent negative pressure ventilation in the treatment of hypoxic hypercapnic coma in chronic respiratory insufficiency.

In recent years non-invasive ventilatory techniques have been used successfully in the treatment of acute on chronic respiratory failure (ACRF), but careful selection of patients is essential and a comatose state may represent an exclusion criterion. The aim of this retrospective and uncontrolled study was to evaluate whether a non-invasive ventilatory technique such as the iron lung could also be used successfully in patients with hypoxic hypercapnic coma, thus widening the range for application of non-invasive ventilatory techniques. A series of 150 consecutive patients with ACRF and hypoxic hypercapnic coma admitted to our respiratory intensive care unit were evaluated retrospectively. The most common underlying condition was chronic obstructive pulmonary disease (79%). On admission a severe hypoxaemia (Pao2 5.81 (3.01) kPa) and hypercapnia (Paco2 14.88 (2.78) kPa) associated with a decompensated acidosis (pH 7.13 (0.13)) were present, the Glasgow coma score ranged from 3 to 8, and the mean APACHE II score was 31.6 (5.3). All patients underwent intermittent negative pressure ventilation with the iron lung. The study end point was based on a dichotomous classification of treatment failure (defined as death or need for endotracheal intubation) versus therapeutic success. There were 45 treatment failures (30%) and 36 deaths (24%). Nine patients (6%) required intubation because of lack of airway control. The median total duration of ventilation was 27 hours per patient (range 2-274). The 105 successfully treated cases recovered consciousness after a median of four hours (range 1-90) of continuous ventilatory treatment and were discharged after 12.1 (9.0) days. These results show that, in patients with acute on chronic respiratory failure and hypoxic hypercapnic coma, the iron lung resulted in a high rate of success. As this study has the typical limitations of all retrospective and uncontrolled studies, the results need to be formally confirmed by controlled prospective studies. Confirmation of these results could widen the range of application of non-invasive ventilatory techniques.

Intermittent negative pressure ventilation may increase urine flow in normal subjects.

In order to analyze the effect of intermittent negative pressure ventilation (NPV) on renal function, we studied 20 healthy male volunteers (mean age 29 +/- 4.1 years). NPV was performed with an "Emerson Chest Respirator Pump", adjusted to a breathing frequency of 10 respirations per minute, with inspiratory time/total respiratory time ratio of 0.4 and negative pressure of 25 cmH2O. The experimental protocol was carried out in two phases of two hours each--spontaneous breathing and NPV breathing. At the end of each phase, urine volume of the whole period was collected as well as venous blood sample for biochemical determinations. During NPV there was significant increase (P < 0.05) in urine flow rate (1.43 +/- 0.81 to 2.76 +/- 1.95 ml/min) as well as in natriuresis (258 +/- 201 to 389 +/- 175 mcEq/min), kaliuresis (61 +/- 45 to 98 +/- 49 mcEq/min), fractional sodium excretion (1.38 +/- 0.88 to (1.96 +/- 0.98%), osmolar clearance (3.13 +/- 1.82 to 4.32 +/- 1.24 ml/min) and pH (7.37 +/- 0.04 to 7.41 +/- 0.07) with unchanged creatinine and free water clearances. We concluded that NPV increases urine flow rate, kaliuresis and natriuresis but the data we have do not allow us to explain the mechanisms underlying such a phenomenon.

Negative extrathoracic pressure ventilation for phrenic nerve palsy after paediatric cardiac surgery.

To investigate the feasibility of negative extrathoracic pressure ventilation as a respiratory support following phrenic nerve palsy after cardiac surgery. An uncontrolled pilot study. 14 patients aged one week to 30 months (median 5.3 months) with phrenic nerve palsy diagnosed by phrenic nerve conduction tests and diaphragmatic electromyograms. Four had bilateral and 10 unilateral palsy. Before treatment all required oxygen and 10 were receiving positive pressure ventilation. One of the patients with bilateral and four of the patients with unilateral palsies had undergone a plication before negative pressure ventilation was started. Treatment was started 6-65 days (median 23) after operation with a newly designed system which included a Perspex chamber, which gave easy access to the child, and an elastic latex neck seal. Continuous negative pressure was used in conjunction with intermittent positive pressure ventilation while continuous or intermittent negative pressure ventilation was used in extubated infants. All four patients with bilateral palsy survived with long-term intermittent negative pressure ventilation and did not require further surgery. Of the 10 with unilateral lesions, seven required no further surgery, two underwent plication, and one had a re-plication. Three patients with unilateral palsy died of non-respiratory causes. The duration of positive pressure ventilation after starting negative pressure ranged from 0 to 23 days (median 6). Treatment with negative pressure lasted for 3-241 days (median 32) and was predominantly administered off the intensive care unit, including at home. Negative pressure ventilation may be an alternative to positive airway pressure ventilation in the management of phrenic nerve palsy. A multicentre randomised controlled trial is now required to assess further the role of negative pressure ventilation in phrenic nerve palsy.

Iron Lung Treatment of Subjects with COPD in Acute Respiratory Failure: Evaluation of Short- and Long-term Prognosis

We evaluated retrospectively the short-term and the long-term prognosis of 105 patients with COPD and prolonged respiratory insufficiency admitted to our respiratory intensive care unit from 1976 to 1980 for acute respiratory failure. All subjects underwent intermittent negative pressure ventilation by means of an iron lung to overcome the acute episode. Twelve patients died during hospitalization, six were lost after discharge, while 87 were successfully weaned and were included in a follow-up lasting five years. All relapses of ARF were treated by INPV. The survival rates after one and five years were 82 percent and 37 percent, respectively and were significantly influenced by factors such as age, chronic cor pulmonale, FEV1/VC, PaCO2 on admission. The survival rate observed in our patients was better than that reported previously by other authors in COPD patients with ARF submitted to mechanical ventilation after intubation. These results suggest that INPV can improve survival in this category of patients, but a controlled clinical trial will be needed to address this issue.

Intermittent Short-term Negative Pressure Ventilation and Increased Oxygenation in COPD Patients with Severe Hypercapnic Respiratory Failure

With the aim of testing a method that allows increasing concentrations of oxygen to be administered to patients with severe hypoxemia and hypercapnia while avoiding the risk of increasing respiratory acidosis, we studied 17 male patients with advanced chronic obstructive pulmonary disease (COPD) and severe hypercapnic respiratory failure. During 6 h and on one day only, all patients were given intermittent negative pressure ventilation (INPV) together with oxygenation starting at a concentration of 24 percent and increasing to 30 percent. Using this procedure, it was possible to raise arterial PaO2 to safe levels (from 47.2 +/- 3 mm Hg to 61.5 +/- 6 mm Hg, p less than 0.001) without increasing hypercapnia, and a significant drop in PaCO2 levels (from 74.4 +/- 9 mm Hg to 65.6 +/- 12 mm Hg, p less than 0.005) was even observed. One hour after INPV ended, the mean values of PaO2, PaCO2, oxygen saturation, and pH were also significantly better than prestudy values. We conclude that INPV and oxygen therapy with increasing oxygen flow could constitute an alternative option to intubation and mechanical ventilation in cases of severe hypercapnic respiratory failure due to advanced COPD.

Effect of negative pressure ventilation on arterial blood gas pressures and inspiratory muscle strength during an exacerbation of chronic obstructive lung disease.

The effects of intermittent negative pressure ventilation have been studied in 20 patients with chronic obstructive pulmonary disease during an exacerbation of their disease. Measurements of arterial blood gas tensions and maximal inspiratory pressure (MIP) were performed before and after six hours of negative pressure ventilation or standard treatment (control day) given in random order on two consecutive days. After negative pressure ventilation the mean (SD) value of MIP increased from 68.1 (21.5) to 74.8 (20) cm H2O;* arterial oxygen tension (PaCO2) fell from 60.6 (12.2) to 50.9 (8.9) mm Hg* but PaO2 changed little (from 48.4 (7.4) to 47.6 (8.2) mm Hg). There were no significant changes on the control day in arterial blood gas tensions (PaO2 47.8 (8.1) and 48.9 (9.4) and Paco2 59.8 (10.9) and 57.5 (8.06) mm Hg) or in MIP (69.4 (22.4) and 70.9 (22.9) cm H2O). Six patients tolerated negative pressure ventilation poorly and these patients showed less improvement after negative pressure ventilation. Our results suggest that intermittent negative pressure ventilation can increase alveolar ventilation in patients with an exacerbation of chronic obstructive lung disease, particularly in those who tolerate the procedure well. Most subjects showed a fall in PaCO2 and an increase in MIP. The fact that PaO2 was unchanged despite the fall in PaCO2 suggests that gas exchange may deteriorate with negative pressure ventilation in these patients.

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

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

Short term effect of intermittent negative pressure ventilation in COPD patients with respiratory failure

Ten patients with stable chronic obstructive pulmonary disease (COPD) and hypercapnic respiratory failure were randomly submitted to intermittent negative pressure ventilation (INPV) 6 h per day for 5 consecutive days by either a cuirass or pneumo wrap ventilator. The effects were assessed by measurements of spirometry, blood gases, maximal inspiratory (MIP) and expiratory (MEP) pressures, 12 minutes walking distance test (12 mwd), sensation of dyspnoea by a visual analogue scale (VAS) and diaphragmatic electromyographic activity (Edi). Edi was recorded during INPV sessions in only 7 patients. The same measurements apart from Edi were also performed in 8 matched control patients randomly submitted to conventional physiotherapy. During INPV, Edi activity was reduced, at least temporarily down to 50% of baseline values. Comparison of baseline with post INPV values showed no changes in thoracic gas volume (TGV), forced expiratory volume in one second (FEV1), FEV1/forced vital capacity (FVC), arterial oxygen partial pressure (Pao2) and MEP; significant improvements were seen in MIP, vital capacity (VC), VAS, and 12 mwd only in patients submitted to INPV. A significant improvement in PaCO2 was observed in both groups of patients. We conclude that INPV may be effective in improving the functional reserve of the inspiratory muscles in selected COPD patients with hypercapnic respiratory failure and signs of inspiratory muscle dysfunction.

Negative-Pressure Ventilation Improves Respiratory Center Drive in Patients with Chronic Obstructive Pulmonary Disease (COPD)

We have previously demonstrated that intermittent negative pressure ventilation (NPV) for 8 h/day for 2 consecutive days results in sustained improvement in gas exchange for 3 subsequent days in patients with COPD and carbon dioxide retention. We tested the hypothesis that this improvement was associated with an alteration of respiratory center drive and ventilatory response to hypoxemia and hypercapnia in 5 patients with COPD (FEV1: 22.6 ± 3.0% pred; TGV: 208 ±17.7% pred; PaO2 [FIO2 0.28]: 64.2 ± 6.5 mm Hg; PaCO2: 52 ± 35 mm Hg).

Respiratory effect on the blood volume of pulmonary capillaries.

We measured the density variations of aortic blood from rabbits ventilated by a positive end inspiratory pressure of 6 mmHg or a negative box pressure of the same magnitude. When calculated from the density variations, the fluctuations in blood volume of the pulmonary capillaries within one cycle as induced by an intermittent positive pressure ventilation were found to be similar to the ones induced by an intermittent negative pressure ventilation. Using these volumetric fluctuations as a means to assess the transpulmonary pressure and the transmural pressure across the pulmonary capillaries, we conclude that the switching of the ventilation method did not alter the cyclic fluctuations of these pressures.

Intermittent negative pressure ventilation in the treatment of respiratory failure in progressive neuromuscular disease.

Five men with degenerative neuromuscular diseases (three with amyotrophic lateral sclerosis [ALS] and two with Duchenne's muscular dystrophy [DMD]) who had respiratory failure were treated with intermittent negative pressure ventilation (NPV). One patient with ALS in severe acute respiratory failure was successfully treated with NPV alone. This patient and two other ALS patients in chronic respiratory failure with PaCO2 elevation stabilized or improved their vital capacity (VC) and lowered their PaCO2 after 5 to 11 weeks of therapy. Finally, intermittent NPV was used to replace 24-hour positive pressure ventilation in two patients with DMD. It is concluded that intermittent NPV may stabilize or temporarily improve the respiratory status in patients with progressive neuromuscular diseases.

Respiratory failure after thoracoplasty: treatment by intermittent negative-pressure ventilation.

Ten patients with severe respiratory failure secondary to extensive pulmonary tuberculosis and thoracoplasty have been treated with intermittent negative-pressure ventilation. All recovered and have been followed up for from six months to eight years. Two have died from unrelated causes and six have used some form of breathing aid at home. Negative-pressure ventilation, which is a non-invasive form of respiratory support, offers important benefits in selected cases.

Sinus Arrhythmia in Man: Influence of Tidal Volume and Oesophageal Pressure

The effect of tidal volume (VT) and of the intrathoracic pressure (Poes) on the respiratory sinus arrhythmia (RSA) was studied in healthy subjects. They breathed into a spirometer with a VT of 1, 1.5, and 2 1, at a standardized, slow respiratory rate, 6-min-1 (A). Poes was varied by (B) adding a negative inspiratory pressure (NIP) of 5 cm of water and by (C) intermittent positive pressure ventilation (IPPV) at identical VT and respiratory frequency. In separate study (D), intermittent negative pressure ventilation (INPV) was induced by applying negative pressure on the thorax. In A, increasing VT provoked an augmented RSA by a more marked tachycardia as well as bradycardia. On increasing the amplitude of Poes in B, RSA was somewhat more marked due to a lower minimum heart rate. Whem comparing respiratory cycles that had similar Poes but a different VT, the larger VT caused a slight increase in the RSA amplitude due to a more marked deceleration of the heart rate. IPPV almost abolished RSA, whereas INPV did not reduce the arrhythmia. It is concluded that pulmonary stretch reflexes to a minor extent contribute to RSA, whereas the hypothesis of a central nervous origin does not gain support. Cardiovascular reflexes remain the main possible cause of RSA.

The Negative-Pressure Respirator: An Improved Design

Modification of the standard negative-pressure respirator, which easily permits application of intermittent negative-pressure ventilation to the infant of less than 1,000 gm, has been described. Previously encountered problems of fixation of the infant, of maintenance of oxygen concentrations, and of inability to obtain chest films of the infant while in the device have been overcome.

Sinus Arrhythmia in Man: Influence of Tidal Volume and Oesophageal Pressure

The effect of tidal volume (VT) and of the intrathoracic pressure (Poes) on the respiratory sinus arrhythmia (RSA) was studied in healthy subjects. They breathed into a spirometer with a VT of 1, 1.5, and 2 1, at a standardized, slow respiratory rate, 6-min-1 (A). Poes was varied by (B) adding a negative inspiratory pressure (NIP) of 5 cm of water and by (C) intermittent positive pressure ventilation (IPPV) at identical VT and respiratory frequency. In a separate study (D), intermittent negative pressure ventilation (INPV) was induced by applying negative pressure on the thorax. In A, increasing VT provoked an augmented RSA by a more marked tachycardia as well as bradycardia. On increasing the amplitude of Poes in B, RSA was somewhat more marked due to a lower minimum heart rate. When comparing respiratory cycles that had similar Poes but a different VT, the larger VT caused a slight increase in the RSA amplitude due to a more marked deceleration of the heart rate. IPPV almost abolished RSA, whereas INPV did not reduce the arrhythmia. It is concluded that pulmonary stretch reflexes to a minor extent contribute to RSA, whereas the hypothesis of a central nervous origin does not gain support. Cardiovascular reflexes remain the main possible cause of RSA.

Combined positive and negative pressure ventilation in the management of severe respiratory distress syndrome in newborn infants.

Eleven newborn infants with severe respiratory distress syndrome (RDS) were artificially ventilated with an intermittent positive pressure respirator while a continuous negative pressure of ––4 to ––8 cm H&lt;sub&gt;2&lt;/sub&gt;O was maintained about the chest; thereby achieving the equivalent positive of pressure ventilation. Although only two infants ultimately survived, arterial oxygen tension was improved in all patients, with a mean rise of 69.8 ± 17.3 mm Hg. Simultaneously, the alveolar-arterial oxygen difference fell·by a mean of 63.7 ± 18.4 mm Hg, even though the infants had not improved on preceding trials of both intermittent negative and intermittent positive pressure ventilation alone. These changes are significant at a level of p &lt; 0.01. The maintenance of a continuous transpulmonary pressure gradient is an effective method for improving arterial oxygenation in infants requiring mechanical ventilation for the respiratory failure of RDS.