Physiologic Evaluati~n of Pressure Support Ventilation .by Nasal Mask in Patients with Stable COPO* N. Ambrosino , M.D .; S. Naoa, M.D. ; P. Bertone, P.T.; C. Eracchia, M.D .; and C. Rampulla, M.D.
We evaluated the physiologic effects of pressure support ventilation by nasal route (NPSV) in eight patients with severe stable COPD and chronic hypercapnia who were randomly submitted to 2-h sessions of NPSV both with a portable ventilator (Respironics BIPAP device) and with a standard ventilator (Bird 6400ST device) at an inspiratory airway pressure of 22 cm Two sessions with each ventilator were performed using an FIs of 0.21 in each patient on two consecutive days. One patient did not tolerate either form of ventilation. Comparison of spontaneous with BIPAP ventilation showed a significant improvement in pH, PaCO., and PaO •• Ventilatory pattern assessed by a respiratory inductive plethysmograph showed a significant increase in minute ventilation (VE), VT, and Ttot. Integrated surface diaphragmatic EMG activity measured only during BIPAP device ventilation decreased from that measured during spontaneous breathing. Similar changes in blood gases and ventilatory pattern were observed during venti-
lation by the Bird 6400ST except for VTffi ratio, which significantly increased. Comparison of baseline with measurements performed 12 h after the whole cycle of treatment showed a significant increase in pH and VE and a decrease in PaCO.. We conclude that short-term NPSV may be usefUl in improving respiratory pattern and blood gases in stable COPD patientS with chronic hyperCapnia. (Chest 1992; 101:385-91)
Intermittent positive pressure ventilation applied through a nasal mask (NPPV) has been showiJ. to be useful in the treatment of chronic respiratory failure resulting from neuromuscular, chest wall, and chronic obstructive pulmonary diseases. It is usually delivered by standard volume-cycled ventilators in assisted or controlled mode. I~ Pressure support ventilation (PSV) is an assisted mode of ventilation that supplies a constant set level of positive airway pressure during spontaneous inspiratory efforts. PSV allows the patient to maintain Control of inspiratory time (1i) and expiratory time (Te)and to interact with set pressure to determine the ultimate flow and tidal volume (VT).7.8 PSV has been used during weaning from mechanical ventilationv'" and in the immediate period after cardiac surgery, 11 and it is being more and more frequently applied in acute respiratory failure, also by facial mask I2• 1• To our knowledge, no report has been given on the use of nasal PSV (NPSV) in stable COPD patients with chronic hypercapnic respiratory failure. The aim of
this study was to evaluate the acute physiologic effects of NPSV delivered by a portable device specifically conceived for NPPV in stable COPD patients with chronic hypercapnia.
u.0.
*From the Fondazione Clinica del Lavoro IRCCS and the Centro Medico di Riabilitazione di Montescano, Pavia, Italy. Manuscript received January 14; revision accepted June 4. Reprint requests:Dr. Ambrosino,Centro MediCo, 27040Montescano
(lbt>la), Italy
ABD = abdomen; APRV= airway pressure-release ventilation; CPAP=cOntinuous positive airway pressure; Edi=integrated electromyogram .of the diaphragm; INPV = intermittent negative-pressure ventilation; IPPB = intermittent positive-pressure breething; NPPV = intermittent positive-pressure ventilation applied through a nasal mask; NPSV= misal pressure support ventilation· PIP = peak inBatioo pressure; PSV=pressure support ven~ I\C=rib cage; RIP = respiratory inductive plethysmography; Te=expiratory time; Ti=inspiratory titne; Ttot = total respiratory time; VE= minute ventilation; VT= tidal volume
METHODS
Subjects Studies were carried out on eight male patients (mean age; 64.6±11.6 [SO) years; weight , 64.0±8.5 kg; height , 162±9 em), all of whom were smokers or exsmokers with chronic hypercapnia. The physiologic characteristics of the studied population are shown in 'DIble 1. Patient 5 also suffered from a fibrothorax. During the study, the patients were in a stable condition, without exacerbations of respiratory symptoms or any relevant acute disease . All of the patients received long-term oxygen therapy, oral long-acting aminophylline , and inhaled bronchodilators. No change in medical and oxygen therapy had been made the week preceding the study. No patient had ever been submitted to any form of mechanical ventilation before the study. All of the patients gave their informed consent to participate in the study. Dynamic lung volumes were evaluated by means of a water spirometer (Biomedin, Padua, Italy) with the patient in the seated posture, and static lung volumes were assessed by means of helium dilution method . The predicted values were according to Quanier.IS An automated analyzer (Radiometer ABL 30, Copenhagen) was used to measure blood gases in arterialized blood from the ear lobe. Airflow was measured by a pneumotachograph (Screen mate , Jaeger, Hachburg, Germany) connected between the inlet tube and CHEST I 101 12 I FEBRUARY, 1992
385
Table I-Pull7WflQry Function Values· Patient
VC, %prd
FEV" L
FEV" %prd
FEV,IFVC , %
RV, %prd
PaD" mm H~
PaCO" mm H~
pH
1 2 3 4 5 6
38 29 45 21 30 36 35 15 31 10
0.63 0.45 0 .95 0 .39 0 .82 0 .63 0.47 0 .33 0.58 0 .21
20 15 40 14 26 22 23 II 21
38 34 63 45 60 43
276 119 168 124
66 54
45
I>
10
162 319 164 90
45 55 47 56 60 49 48 42 50 6
7.34 7.34 7.38 7.32 7.35 7.37 7.35 7.41 7.36 0.03
t
I> Mean SO
38 46
*%prd = percentage of predicted value . the nose mask . Ventilatory pattern and separate contribution of rib cage (RC) and abdomen (ABO), VT, and respiratory frequency were obtained by respiratory inductive plethysmography (RIP) (Ambulatory Monitoring Inc, Ardsley, NY) in the DC mode . The two recording bands were placed on the middle RC about 10 em above the xiphoid process of the sternum and on the ABO just above the umbilical line, respectively. The calibration was performed with the isovolume maneuver and the patient in a sitting posture .!" Integrated electromyogram (EMG) of the diaphragm (Edi) was recorded via bipolar surface electrodes placed on the sixth and seventh intercostal spaces, close to the anterior costal border. The EMG signals were filtered (0.2 to 1.6 kHz), full-wave rectified, and integrated by means of a leaky integrator with a time constant of 0 .03 s." The pressures developed by the ventilators at the mask were measured by a 7o-cm-long catheter connected to a pressure transducer (:!: 300 ern 11,0) (Honeywell, Freeport, III). RC and ABO displacement , VT, Edi, airflow, and the pressure developed at the mask by the ventilator were recorded on a six-channel strip chart recorder (Battaglia Hangoni , Casaleechio di Reno , Italy). Stuefy Protocol
After baseline measurements, performed during I h of spontaneous breathing with the mask on, each patient underwent two sessions of NPSV with a portable ventilator (BIPAP, Respironics, Monroeville, Pal while in a sitting posture. The BIPAP device is a nasal continuous positive airway pressure (CPAP) blower modified with a solenoid system that allows delivery of positive airway pressure at two different levels in both "spontaneous" (assisted) and " timed" (controlled) mode, which has been extensively described
46
lOS
53
71 63 57 63 57 61 6
elsewhere" and is depicted in Figure 1. In the timed mode, the principles ofBIPAP ventilation are similar to those seen with airway pressure-release ventilation (APRV)." .,. In the spontaneous mode, inspiratory positive peak inflation pressure (PIP), up to a maximum of 22 cm H,O, and expiratory positive airway pressure can be set by a care-giver, but it is the patient who triggers inspiration and expiration in a manner similar to that used in PSv.· ·I • Once pneumotachograph , RIP bands, and EMG electrodes had been positioned and baseline measurements performed, NPSV was applied through a comfortable, tightly fitted nasal mask (Respironics Inc). The BIPAP device was set in the spontaneous mode with the maximal PIP value tolerated by the patients that was able to induce a VT ranging from 10 to 15 rnl/kg, Expiratory positive airway pressure was set to zero on the ventilator, which , due to the fact that the flow of the machine is continuous, means a negligible positive pressure at the mask (I cm H,O) . Ventilatory sessions were performed using an Flo, of 0.21. To validate the effectiveness of BIPAP as a device able to effectively deliver NPSV, changes in blood gases and in respiratory pattern were assessed in the same patients also randomly undergoing two sessions of NPSV by means of a standard ventilator (Bird 6400 S1') set in PSV mode at the same PIP as with BIPAP device. Efforts were made to reduce unnecessary noise and distractions and to encourage maximal relaxation. Instructions were given to keep the mouth closed. Each session lasted about 2 h over two consecutive days .
Data Analysis Edi was measured as millimeters of deflection from baseline and then expressed as a percentage of control deflections. Edi and respiratory pattern were analyzed on a breath-by-breath basis for 15 consecutive breaths during spontaneous breathing and during
FIGlJRE 1. BIPAP device used to deliver NPSV.
386
Pressure Support Ventilation by Nasal Mask (Ambrosino et 81)
Table 2-Changes in Ventilatory Pattern during BIPAP Device and Bird 6400ST Ventilation BaselineBIPAP Device 8.2 (1.8) VE. Umin Vr v ml 408 (119) Respiratory freque ncy. bpm 21 (4) Ttot , s 3.0 (0.6) Ll (0.6) 11. s 37 (2) TJII'tot. % VTITI. ml/s 363 . (83) Bird6400ST VE. Umin 9.2 (1.5) vrml 443 (61) Respirat ory frequency. bpm 21 (4) Ttot , s 2.9 (0.5) Ll (0.2) 11. sec TJII'tot. % 38 (3) VTITI. ml/s 400 (62)
p Value
Ventilation" , '
We evaluated the physiologic effects of pressure support ventilation by nasal route (NPSV) in eight patients with severe stable COPD and chronic hypercapnia who were randomly submitted to 2-h sessions of NPSV both with a portable ventilator (Respironics BIPAP device) and with a standard ventilator (Bird 6400ST device) at an inspiratory airway pressure of 22 cm Two sessions with each ventilator were performed using an FIs of 0.21 in each patient on two consecutive days. One patient did not tolerate either form of ventilation. Comparison of spontaneous with BIPAP ventilation showed a significant improvement in pH, PaCO., and PaO •• Ventilatory pattern assessed by a respiratory inductive plethysmograph showed a significant increase in minute ventilation (VE), VT, and Ttot. Integrated surface diaphragmatic EMG activity measured only during BIPAP device ventilation decreased from that measured during spontaneous breathing. Similar changes in blood gases and ventilatory pattern were observed during venti-
lation by the Bird 6400ST except for VTffi ratio, which significantly increased. Comparison of baseline with measurements performed 12 h after the whole cycle of treatment showed a significant increase in pH and VE and a decrease in PaCO.. We conclude that short-term NPSV may be usefUl in improving respiratory pattern and blood gases in stable COPD patientS with chronic hyperCapnia. (Chest 1992; 101:385-91)
Intermittent positive pressure ventilation applied through a nasal mask (NPPV) has been showiJ. to be useful in the treatment of chronic respiratory failure resulting from neuromuscular, chest wall, and chronic obstructive pulmonary diseases. It is usually delivered by standard volume-cycled ventilators in assisted or controlled mode. I~ Pressure support ventilation (PSV) is an assisted mode of ventilation that supplies a constant set level of positive airway pressure during spontaneous inspiratory efforts. PSV allows the patient to maintain Control of inspiratory time (1i) and expiratory time (Te)and to interact with set pressure to determine the ultimate flow and tidal volume (VT).7.8 PSV has been used during weaning from mechanical ventilationv'" and in the immediate period after cardiac surgery, 11 and it is being more and more frequently applied in acute respiratory failure, also by facial mask I2• 1• To our knowledge, no report has been given on the use of nasal PSV (NPSV) in stable COPD patients with chronic hypercapnic respiratory failure. The aim of
this study was to evaluate the acute physiologic effects of NPSV delivered by a portable device specifically conceived for NPPV in stable COPD patients with chronic hypercapnia.
u.0.
*From the Fondazione Clinica del Lavoro IRCCS and the Centro Medico di Riabilitazione di Montescano, Pavia, Italy. Manuscript received January 14; revision accepted June 4. Reprint requests:Dr. Ambrosino,Centro MediCo, 27040Montescano
(lbt>la), Italy
ABD = abdomen; APRV= airway pressure-release ventilation; CPAP=cOntinuous positive airway pressure; Edi=integrated electromyogram .of the diaphragm; INPV = intermittent negative-pressure ventilation; IPPB = intermittent positive-pressure breething; NPPV = intermittent positive-pressure ventilation applied through a nasal mask; NPSV= misal pressure support ventilation· PIP = peak inBatioo pressure; PSV=pressure support ven~ I\C=rib cage; RIP = respiratory inductive plethysmography; Te=expiratory time; Ti=inspiratory titne; Ttot = total respiratory time; VE= minute ventilation; VT= tidal volume
METHODS
Subjects Studies were carried out on eight male patients (mean age; 64.6±11.6 [SO) years; weight , 64.0±8.5 kg; height , 162±9 em), all of whom were smokers or exsmokers with chronic hypercapnia. The physiologic characteristics of the studied population are shown in 'DIble 1. Patient 5 also suffered from a fibrothorax. During the study, the patients were in a stable condition, without exacerbations of respiratory symptoms or any relevant acute disease . All of the patients received long-term oxygen therapy, oral long-acting aminophylline , and inhaled bronchodilators. No change in medical and oxygen therapy had been made the week preceding the study. No patient had ever been submitted to any form of mechanical ventilation before the study. All of the patients gave their informed consent to participate in the study. Dynamic lung volumes were evaluated by means of a water spirometer (Biomedin, Padua, Italy) with the patient in the seated posture, and static lung volumes were assessed by means of helium dilution method . The predicted values were according to Quanier.IS An automated analyzer (Radiometer ABL 30, Copenhagen) was used to measure blood gases in arterialized blood from the ear lobe. Airflow was measured by a pneumotachograph (Screen mate , Jaeger, Hachburg, Germany) connected between the inlet tube and CHEST I 101 12 I FEBRUARY, 1992
385
Table I-Pull7WflQry Function Values· Patient
VC, %prd
FEV" L
FEV" %prd
FEV,IFVC , %
RV, %prd
PaD" mm H~
PaCO" mm H~
pH
1 2 3 4 5 6
38 29 45 21 30 36 35 15 31 10
0.63 0.45 0 .95 0 .39 0 .82 0 .63 0.47 0 .33 0.58 0 .21
20 15 40 14 26 22 23 II 21
38 34 63 45 60 43
276 119 168 124
66 54
45
I>
10
162 319 164 90
45 55 47 56 60 49 48 42 50 6
7.34 7.34 7.38 7.32 7.35 7.37 7.35 7.41 7.36 0.03
t
I> Mean SO
38 46
*%prd = percentage of predicted value . the nose mask . Ventilatory pattern and separate contribution of rib cage (RC) and abdomen (ABO), VT, and respiratory frequency were obtained by respiratory inductive plethysmography (RIP) (Ambulatory Monitoring Inc, Ardsley, NY) in the DC mode . The two recording bands were placed on the middle RC about 10 em above the xiphoid process of the sternum and on the ABO just above the umbilical line, respectively. The calibration was performed with the isovolume maneuver and the patient in a sitting posture .!" Integrated electromyogram (EMG) of the diaphragm (Edi) was recorded via bipolar surface electrodes placed on the sixth and seventh intercostal spaces, close to the anterior costal border. The EMG signals were filtered (0.2 to 1.6 kHz), full-wave rectified, and integrated by means of a leaky integrator with a time constant of 0 .03 s." The pressures developed by the ventilators at the mask were measured by a 7o-cm-long catheter connected to a pressure transducer (:!: 300 ern 11,0) (Honeywell, Freeport, III). RC and ABO displacement , VT, Edi, airflow, and the pressure developed at the mask by the ventilator were recorded on a six-channel strip chart recorder (Battaglia Hangoni , Casaleechio di Reno , Italy). Stuefy Protocol
After baseline measurements, performed during I h of spontaneous breathing with the mask on, each patient underwent two sessions of NPSV with a portable ventilator (BIPAP, Respironics, Monroeville, Pal while in a sitting posture. The BIPAP device is a nasal continuous positive airway pressure (CPAP) blower modified with a solenoid system that allows delivery of positive airway pressure at two different levels in both "spontaneous" (assisted) and " timed" (controlled) mode, which has been extensively described
46
lOS
53
71 63 57 63 57 61 6
elsewhere" and is depicted in Figure 1. In the timed mode, the principles ofBIPAP ventilation are similar to those seen with airway pressure-release ventilation (APRV)." .,. In the spontaneous mode, inspiratory positive peak inflation pressure (PIP), up to a maximum of 22 cm H,O, and expiratory positive airway pressure can be set by a care-giver, but it is the patient who triggers inspiration and expiration in a manner similar to that used in PSv.· ·I • Once pneumotachograph , RIP bands, and EMG electrodes had been positioned and baseline measurements performed, NPSV was applied through a comfortable, tightly fitted nasal mask (Respironics Inc). The BIPAP device was set in the spontaneous mode with the maximal PIP value tolerated by the patients that was able to induce a VT ranging from 10 to 15 rnl/kg, Expiratory positive airway pressure was set to zero on the ventilator, which , due to the fact that the flow of the machine is continuous, means a negligible positive pressure at the mask (I cm H,O) . Ventilatory sessions were performed using an Flo, of 0.21. To validate the effectiveness of BIPAP as a device able to effectively deliver NPSV, changes in blood gases and in respiratory pattern were assessed in the same patients also randomly undergoing two sessions of NPSV by means of a standard ventilator (Bird 6400 S1') set in PSV mode at the same PIP as with BIPAP device. Efforts were made to reduce unnecessary noise and distractions and to encourage maximal relaxation. Instructions were given to keep the mouth closed. Each session lasted about 2 h over two consecutive days .
Data Analysis Edi was measured as millimeters of deflection from baseline and then expressed as a percentage of control deflections. Edi and respiratory pattern were analyzed on a breath-by-breath basis for 15 consecutive breaths during spontaneous breathing and during
FIGlJRE 1. BIPAP device used to deliver NPSV.
386
Pressure Support Ventilation by Nasal Mask (Ambrosino et 81)
Table 2-Changes in Ventilatory Pattern during BIPAP Device and Bird 6400ST Ventilation BaselineBIPAP Device 8.2 (1.8) VE. Umin Vr v ml 408 (119) Respiratory freque ncy. bpm 21 (4) Ttot , s 3.0 (0.6) Ll (0.6) 11. s 37 (2) TJII'tot. % VTITI. ml/s 363 . (83) Bird6400ST VE. Umin 9.2 (1.5) vrml 443 (61) Respirat ory frequency. bpm 21 (4) Ttot , s 2.9 (0.5) Ll (0.2) 11. sec TJII'tot. % 38 (3) VTITI. ml/s 400 (62)
p Value
Ventilation" , '
