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The use of exsufflation with negative pressure in postoperative patients
The Use of Exsufflation with Negative Pressure in Postoperative Patients li.WILLIAMS, M.D.
EDWARD
AND
DUNCAN
From tbe Departments of Medicine and Anesthesiology, Columbia University, College of Physicians and Surgeons, and Tbe Presbvterian Hospital, New York, New York. These studies were supported by a grant from the National Foundation for Infantile Paralvsis and bv a medical research grant from the National Tubercul&is Association, tbrougb its Medical Section, tbe American Trudeau Society. ”
”
”
effects of exsufhation with negative pressure (EWNP) on patients with respiratory disease accompanied by retention of bronchial secretions have been described by Barach and his co-workers.‘,” After genera1 anesthesia and operation, retention of bronchial secretions and impaired ventiIation occur frequentIS. The present study was undertaken to determine the infIuence of EWNP upon these two factors. ArteriaI blood CO2 and 02 contents and pIasma pH were obtained in ten cases before, during and after EWNP. Seven of these patients had undergone abdomina1 operations and were studied as soon as possibIe after the termination of anesthesia, during the period when mixed respiratory and metabolic acidosis may exist. Three non-surgica1 patients with acidosis were studied; two suffered from advanced pulmonary emphysema and the third had miId, uncompensated metabolic acidosis of undetermined origin. Observations aIso were made on the effects of EWNP on the clinical course of fifteen surgical patients who required treatment for retained bronchial secretions one or more days after operation.
T
HE beneficial
METHODS
A portabIe exsuflator was used to deIiver room air to the subject through a Bennett face mask. The apparatus maintained positive pressure for 2.5 seconds; then, by means of a rapidIy acting vaIve, negative pressure was estabIished which suddenIy reversed the direction of air flow. During the positive pressure phase the mask pressure rose to 20 or 30 mm.
A. HOLADAY,
M.D.,New
York, New l'ork
Hg. Upon reversal of flow the mask pressure dropped within 0.02 second to minus 30 or 40 mm. Hg, causing peak expiratory flow rates as high as 8 to IO L. per second.’ The mask was heId over the subject’s nose and mouth while the Iower jaw was puIIed forward and upward by applying traction to the mandible with the finger tips in order to maintain an open airway. An oropharyngeal airway was used in severa patients who were sufficientIy anesthetized to tolerate it. The mask was applied in the usual manner to the face of one patient in whom an endotracheal tube was stiI1 in place. When the mask was properIy appIied to the seven unconscious patients, their respiratory patterns were soon replaced by the cycling of the apparatus. The unanesthetized subjects were instructed to keep the glottis open and to allow the exsufflator to inflate and defIate their lungs. Control measurements of arterial blood pH were made and a bIood sampIe was obtained immediately before application of EW’NP. Ten consecutive positive-negative pressure cycles were deIivered to each subject. The mask was then removed for thirty to ninet>- seconds, during which time secretions were removed from the mouth and pharynx with suction. The procedure was repeated until a tota of five effective series of ten exsufhations had been administered. During the last series, starting with the sixth cycle, the second blood sample and pH determination were obtained. Six to ten minutes later the final blood sample and pH determinations were obtained. No treatment was given between the second and third blood sampIes. ArteriaI bIood samples were drawn from the brachia1 artery through a Cournand needle into greased syringes containing heparin and mercury. The samples were refrigerated and mixed continuously by sIow rotation until analyzed. ArteriaI pIasma pH was measured by the method of HoIaday” immediateIv before
WiIIiams
and HoIadal
and after coIIection of each sampIe. BIood oxygen and carbon dioxide contents were determined manometricaIIy by the method of GoIdstein.4,5 Oxygen capacity was determined manometricaIIy on bIood sampIes equilibrated with room air. Carbon dioxide tension (pCOe)
coIumn as changes from the contro1 figures. Values obtained six to ten minutes after exsuflIation appear in the third coIumn, aIso as changes from the contro1 \-aIues. The control vaIues were typica of those usuaIIy seen after genera1 anesthesia.’ AI1 sub-
TABLE EFFECTS
OF
EWNP
ON
PH
I
PATIENTS
EMERGING
FROM
pCOz (mm. Hg)
I
BB+(mEq./L.)
Before EWNI’
Change during EWNP
Change after EWNP
Before EWNP
+0.01 0.00 So.04 +0.02 +0.03 +0.02 +0.01
46 45 48 46 61 48 43
(lhange
-
Change after EWNP
Before EWNP
- 7.2 -10.5 - 9.0 -18.9 - 4.rJ - 6.0
--0.5 +1.0 -5.5 -1.5 -4.4 0.0 0.0
41.4 39.3 37.3 38.5 42.8 41.7 42.0
-10.2
-1.1
27 5.4 * 2.0
f2.6 f1.0
during 1EWNP
-- 16.0
ANESTHESIA*
-
1
-
02 Saturation
Before EWNP
Change during EWNP
Change after EWNP
78.3 94.6 91.8 81.3 (!a; :Z’
+
8.0
+ +
7.2 2.2 5.2
i-3.4 -4.1 -1.1 -2.9
Change during EWNP
Change after EWNP
+I.2 +r.3 +0.8 +1.5 +1.6 +o.3 +3.4
+o. I +0.6 +a.8 +0.9 +0.5 +0.3 +o 1
+x.44 +I.27 ko.48
87.2 +0.47 Tto.32 zk 6.44 *0.12 i: 2.63
(
I %)
=
9x.2
‘-;;::I -
I.0
+
2.2
(-5. I) +z.9 -2.2
I-
+0.019 fO.013 +O.OOi
48.1 * j.9 + 2.2
JO.4 k 2.06 zk 0.78 -
i 5.58 + 2.28
-0.6: k3.12 +1.27
-
* Control values appear in the coIumns headed “before”; changes from the control values appear in the column headed “change durine” and “charwe after.” The mean of each column is listed with the standard deviations is.d.) and standard error of the mean (sm). The 02 saturation values of subject Y, listed in parentheses, are omitted from the calculation of the mean because this suhiect received oxygen by nasal catheter during the contro1 period and breathed air during the remainder of the experiment.
and whoIe bIood buffer base (BBf) were cakuIated from the nomogram of Singer and Hastings.6 The fifteen surgica1 patients received EWNP according to the foIIowing procedure, varied to suit the condition of the patient: EWNP was administered by face mask for six consecutive cycles. This was foIIowed by about thirty seconds of rest. During the rest period mucus, which had been raised into the mouth or pharynx, was expectorated or removed by suction. This procedure was repeated eight times and was referred to as a treatment. Such treatments were carried out at one- to fourhour intervaIs, depending upon the quantity of secretions and the patient’s abiIity to cough spontaneousIy. RESULTS
The aIterations in bIood chemica1 findings of seven patients having EWNP between twenty and 130 minutes after the termination of anesthesia (average fifty-three minutes) are summarized in Table I. In the first coIumn of each group of figures appear the control vaIues for arteria1 blood pH, pCO,, BB+, and O2 saturation obtained immediateIy before exsufFIation. VaIues obtained during the Iast period of EWNP are recorded in the second 638
jects were acidotic due to miId respiratory acidosis (average pCOz 48 mm. Hg) and moderateIy severe metaboIic acidosis (average BB+ 40.4 mEq./L.). Each case showed some degree of arteria1 oxygen unsaturation. There was more variabiIity of this function than of the others; the saturations ranged from 78 to 95 per cent. EWNP consistently improved a11 measured functions except oxygen saturation. ArteriaI pH was eIevated an average of 0.09 pH units, whiIe pCOZ was decreased an average of IO mm. Hg. The aIterations of bIood buffer base were probably of IittIe physioIogic significance, but a11 were in the same direction and of the same magnitude. The arteria1 oxygen saturation feI1 during EWNP in two subjects and rose from 2 to 8 per cent in four. The average oxygen saturation during EWNP in this group of patients was 89.4 per cent. The vaIues taken six to ten minutes after EWNP show a11 functions returning toward contro1 IeveIs, with pH and buffer base stiI1 remaining eIevated to a sIight but a statisticaIIy significant degree. Three unanesthetized subjects with chronic acidosis were studied. Two of these (W. G. and M. K.) suffered from advanced puImonary emphysema and chronic respiratory insuffIciency. The effects of EWNP upon the arteria1 blood pH, pCOZ, BB+, and 0, saturation of
Postoperative
ExsuffIation
with Negative
procedure depends on maintenance c~f a GdeIJ patent airway. The exsuffIator contains a valve which instantaneously reverses the fiow of air betiveen the apparatus and the lungs, resulting in an abrupt expulsion of air and retained secretions from the lungs. The iInpoSiti(Jn of an>
these subjects are shown in Table II. A fall in pCO2 took place during EWNP of approximately the same extent as in the group of postAlterations of pH and anesthesia patients. buffer base were more variable. All three subjects sho\ved gross oxygen unsaturation before T.\BLE EFFECTS
OF
EWNP
ON
PATIENTS
Pressure
II
WITH
CHRONIC
PLIAI~NARY
DISE.ISE”
nztrrrc EWNP
G. II.
(;har,fy during EWNI’
ctrangc dtcr EWNI’
w. k
J (:.
obstruction, such as a partialI\, closed glottis, retracted tongue or closed lips, impairs the effkiency of EWNP. Barach et al.’ resolved these diffkulties in most instances II>- obtaining the cooperation of the conscious patient. No diffwulty \vas encountered in administering EWNP effectiveI>- to conscious patients in the present study after the patients and the professional staff had received appropriate instructions. Indeed, most of the patients were able to carry out the procedure by themselves \\-hen the apparatus was Ieft at the bedside. In the patients emerging from anesthesia a certain amount of skill, acquired through practice, was necessary to obtain a free air\vay and air-tight mask fit. It is of considerable interest that patients with \\-ounds of the abdomen or chest reported less wound pain during E%‘NP than during spontaneous coughing. In no case nas there disruption of an)- recently sutured \\cJUnd of the chest or abdomen, nor \\as there an?- complication folIowing treatment \vhich could be attributed to EWNP. Sex-era1 patients showed evidence of bullous emphysema prior TO treatment; in none of these n-as there clinical or s-ray change after EWNP to suggest enlargement or rupture Ol‘ bullae. One patient \vith myasthenia grnvis was subjected to extensi7.e surgeq- in\ olving the chest wall. Postopcrativc treatment with EWNP 1~3s eft’cctcd u ithout harmful incident. Since the norI\ of this report was concluded, two patients sul>iected to lobectomy had E\VNP postoperativeI>, I\-ith inflationary pressures limited to 20 mm. Hg. If excessive Iung inflation is a\-oidcd and if reflck
treatment. Although the arterial O2 saturation of two subjects was increased approximateI> of onIy one (J. C.) I; per cent, the 0, saturation reached a normal level. In this instance a significant degree of sustained improvement was shown in the post-treatment vaIue. With this exception, al1 measured functions returned toward pretreatment Ievels. The number of cases in which we observed the clinical effect of EWNP during the postoperative period was too smaI1 to justify tabulation and statistical analysis, yet certain genera1 observations can be made concerning the results. The most obvious benefit derived from the procedure was seen in those patients n-ho couId not or would not cough up secretions because of \vound pain. It was generalI>- found that \I-ithin tw:o to three hours after the first treatment mucopurulent sputum appeared. Improved breath sounds, increased percussion resonance, reduced respirator>- rate and ciearing of+-anosis were some of the signs frequently noted within t\veIve hours after beginning E1YNP. One patient with massive right lower lobe collapse twenty-four hours after th>:roidectomy demonstrated definite clinical evrdence of improved aeration a few hours after the start of hourly EWNP; within five days both lung fieIds \verc almost compIeteIy clear to x--w\- csaniination.
-&
&kC!tiVt?IKSS
of
EWN
P
ill
IXlll~\-ing
retained bronchia secretions from patients \vith fresh operative \I-ounds was cIearIy demonstrated in the present study. The success of the 639
WiIIiams
and HoIaday
protective contraction of the expiratory muscIes of the chest and abdomen is not stimulated, the rapid, extreme pressure change during exsuffIation with negative pressure does not appear to be hazardous. Despite the Iarge tidal volumes obtained during EWNP in the present study the pCOZ did not faII beIow 30 mm. Hg, and the arteria1 oxygen saturation rose above 90 per cent in onIy three of ten patients. Several factors may operate to produce these discrepancies. Since pCOz throughout the body couId not reach equiIibrium during the brief period of EWNP empIoyed, the values observed may represent increased deIivery of CO, from tissue depots. The exsumation apparatus contributes a potentia1 dead air space of 300 cc. between the mask and the exhaIation vaIve. Maintenance of an air-tight mask fit during the fina phases of exsuflIation and during the initia1 phase of inffation of the lung would resuIt in deIivery into the aIveoIi of approximateIy 500 ml. of expended air. This may have contributed to minimize the alterations of the bIood tensions of both CO2 and OZ. Low oxygen saturations which have been observed in the immediate postanesthetic period have been ascribed by Fink* to diIution of aIveoIar air, with subsequent Iowering of aIveoIar pCOZ, by outward diffusion of anesthetic gases. However, in order to produce this effect a gas wouId have to possess certain specific soIubiIity characteristics and be present in high concentration. The onIy such gas used in our patients was nitrous oxide. It was used in the concentration range mentioned by Fink in onIy one case. Since EWNP was applied an average of fifty-three minutes after the termination of administration of anesthetic gases, it is doubtful in any event that concentrations of anesthetic gases wouId be high enough to reduce aIveoIar oxygen tensions significantIy. The rapid bIowing off of carbon dioxide couId not have interfered with oxygenation, since the alveolar concentration of CO2 remained in the norma range of 5 per cent during EWNP. Cherniaks observed incomplete saturation of arteriaI blood during exsufflation without the use of negative pressure. He suggested that it might be due to “an increased ventiIation of normal alveoli occuring at the expense of ventiIation of maIfunctioning parts of the lung.” It seems IikeIy that the rapid flow rates developed during EWNP would favor earIy
expansion of those portions of the lung which have the Iowest resistance to flow. Overdistention of such areas through distortion of adjacent areas would increase the tendency toward uneven ventiIation. Assuming the mixed venous bIood to be 70 per cent saturated and blood returning from ventiIated aIveoIi to be IOO per cent saturated, faiIure to ventilate 24 per cent of the perfused aIveoIi wouId result in a mean arterial saturation of 80 per cent, which was the average saturation obtained during EWNP. SUMMARY I. ExsuffIation with negative pressure was useful in clearing retained bronchial secretions in twenty-two postoperative patients with or without puImonary atelectasis. 2. During the active period of treatment EWNP decreased postanesthetic acidosis by increasing elimination of CO2 through hyperventiIation. The arteria1 oxygen saturation was increased slightly in some cases and decreased in others. Following the use of EWNP, arterial blood gas vaIues reverted toward pretreatment levels promptly. REFERENCES
L., BECK, G. J. and SMITH, W. H. Mechanical production of Aow rates surpassing the capacity of human coughing. Am. J. M. SC., 226: 241, 1953. BARACH, A. L., BECK, G. J. and SPENIEK, M. ExsufFIation with negative pressure; physioIogica1 and clinica studies in poliomyelitis, bronchial asthma, pulmonary emphysema and bronchiectasis. Arch. Int. Med., 93: 825, 1954. HOLADAY, D. A. An improved method for multiple rapid determinations of arteria1 blood pH. J. Lab. u Clin. Med., 44: 149, 1954. GOLDSTEIN, F., GIBBON, J. H., JR. ALLBKITTEK, F. F.,JR.and STAYMAN, J. W., JR. The combined manometric determination of oxygen and carbon dioxide in bIood, in the presence of Iow concentrations of ethyI ether. J. Biol. Cbem., 182: 815, 1950. HOLADAY, D. A. and VEKOSKY, M. The manometric anaIysis of respiratory gases in bIood containing voIatiIe anesthetic agents. I. A comparison of macro-methods. J. Lab. @ CZin. Med. (in press). SINGER, R. B. and HASTINGS,A. B. An improved clinica method for the estimation of disturbances of the acid-base baIance of human bIood. Medicine, 27: 223, 1948. HOLADAY, D. A., MA, D. and PAPPER, E. M. Acidbase baIance during anesthesia. Bull. New York Acad. Med., 28: 543, 1952. FINK, B. R. Diffusion anoxia. Anesthesiology (in press). CHERNIAK, R. M. The effect of mechanical exsuffIation on respiratory gas exchange in chronic pulmonary emphysema. J. Clin. Investigation, 32: I 192,
I. BAKACH, A.
2.
3.
4.
5.
6.
7.
8. g.
1953.
EDWARD
AND
DUNCAN
From tbe Departments of Medicine and Anesthesiology, Columbia University, College of Physicians and Surgeons, and Tbe Presbvterian Hospital, New York, New York. These studies were supported by a grant from the National Foundation for Infantile Paralvsis and bv a medical research grant from the National Tubercul&is Association, tbrougb its Medical Section, tbe American Trudeau Society. ”
”
”
effects of exsufhation with negative pressure (EWNP) on patients with respiratory disease accompanied by retention of bronchial secretions have been described by Barach and his co-workers.‘,” After genera1 anesthesia and operation, retention of bronchial secretions and impaired ventiIation occur frequentIS. The present study was undertaken to determine the infIuence of EWNP upon these two factors. ArteriaI blood CO2 and 02 contents and pIasma pH were obtained in ten cases before, during and after EWNP. Seven of these patients had undergone abdomina1 operations and were studied as soon as possibIe after the termination of anesthesia, during the period when mixed respiratory and metabolic acidosis may exist. Three non-surgica1 patients with acidosis were studied; two suffered from advanced pulmonary emphysema and the third had miId, uncompensated metabolic acidosis of undetermined origin. Observations aIso were made on the effects of EWNP on the clinical course of fifteen surgical patients who required treatment for retained bronchial secretions one or more days after operation.
T
HE beneficial
METHODS
A portabIe exsuflator was used to deIiver room air to the subject through a Bennett face mask. The apparatus maintained positive pressure for 2.5 seconds; then, by means of a rapidIy acting vaIve, negative pressure was estabIished which suddenIy reversed the direction of air flow. During the positive pressure phase the mask pressure rose to 20 or 30 mm.
A. HOLADAY,
M.D.,New
York, New l'ork
Hg. Upon reversal of flow the mask pressure dropped within 0.02 second to minus 30 or 40 mm. Hg, causing peak expiratory flow rates as high as 8 to IO L. per second.’ The mask was heId over the subject’s nose and mouth while the Iower jaw was puIIed forward and upward by applying traction to the mandible with the finger tips in order to maintain an open airway. An oropharyngeal airway was used in severa patients who were sufficientIy anesthetized to tolerate it. The mask was applied in the usual manner to the face of one patient in whom an endotracheal tube was stiI1 in place. When the mask was properIy appIied to the seven unconscious patients, their respiratory patterns were soon replaced by the cycling of the apparatus. The unanesthetized subjects were instructed to keep the glottis open and to allow the exsufflator to inflate and defIate their lungs. Control measurements of arterial blood pH were made and a bIood sampIe was obtained immediately before application of EW’NP. Ten consecutive positive-negative pressure cycles were deIivered to each subject. The mask was then removed for thirty to ninet>- seconds, during which time secretions were removed from the mouth and pharynx with suction. The procedure was repeated until a tota of five effective series of ten exsufhations had been administered. During the last series, starting with the sixth cycle, the second blood sample and pH determination were obtained. Six to ten minutes later the final blood sample and pH determinations were obtained. No treatment was given between the second and third blood sampIes. ArteriaI bIood samples were drawn from the brachia1 artery through a Cournand needle into greased syringes containing heparin and mercury. The samples were refrigerated and mixed continuously by sIow rotation until analyzed. ArteriaI pIasma pH was measured by the method of HoIaday” immediateIv before
WiIIiams
and HoIadal
and after coIIection of each sampIe. BIood oxygen and carbon dioxide contents were determined manometricaIIy by the method of GoIdstein.4,5 Oxygen capacity was determined manometricaIIy on bIood sampIes equilibrated with room air. Carbon dioxide tension (pCOe)
coIumn as changes from the contro1 figures. Values obtained six to ten minutes after exsuflIation appear in the third coIumn, aIso as changes from the contro1 \-aIues. The control vaIues were typica of those usuaIIy seen after genera1 anesthesia.’ AI1 sub-
TABLE EFFECTS
OF
EWNP
ON
PH
I
PATIENTS
EMERGING
FROM
pCOz (mm. Hg)
I
BB+(mEq./L.)
Before EWNI’
Change during EWNP
Change after EWNP
Before EWNP
+0.01 0.00 So.04 +0.02 +0.03 +0.02 +0.01
46 45 48 46 61 48 43
(lhange
-
Change after EWNP
Before EWNP
- 7.2 -10.5 - 9.0 -18.9 - 4.rJ - 6.0
--0.5 +1.0 -5.5 -1.5 -4.4 0.0 0.0
41.4 39.3 37.3 38.5 42.8 41.7 42.0
-10.2
-1.1
27 5.4 * 2.0
f2.6 f1.0
during 1EWNP
-- 16.0
ANESTHESIA*
-
1
-
02 Saturation
Before EWNP
Change during EWNP
Change after EWNP
78.3 94.6 91.8 81.3 (!a; :Z’
+
8.0
+ +
7.2 2.2 5.2
i-3.4 -4.1 -1.1 -2.9
Change during EWNP
Change after EWNP
+I.2 +r.3 +0.8 +1.5 +1.6 +o.3 +3.4
+o. I +0.6 +a.8 +0.9 +0.5 +0.3 +o 1
+x.44 +I.27 ko.48
87.2 +0.47 Tto.32 zk 6.44 *0.12 i: 2.63
(
I %)
=
9x.2
‘-;;::I -
I.0
+
2.2
(-5. I) +z.9 -2.2
I-
+0.019 fO.013 +O.OOi
48.1 * j.9 + 2.2
JO.4 k 2.06 zk 0.78 -
i 5.58 + 2.28
-0.6: k3.12 +1.27
-
* Control values appear in the coIumns headed “before”; changes from the control values appear in the column headed “change durine” and “charwe after.” The mean of each column is listed with the standard deviations is.d.) and standard error of the mean (sm). The 02 saturation values of subject Y, listed in parentheses, are omitted from the calculation of the mean because this suhiect received oxygen by nasal catheter during the contro1 period and breathed air during the remainder of the experiment.
and whoIe bIood buffer base (BBf) were cakuIated from the nomogram of Singer and Hastings.6 The fifteen surgica1 patients received EWNP according to the foIIowing procedure, varied to suit the condition of the patient: EWNP was administered by face mask for six consecutive cycles. This was foIIowed by about thirty seconds of rest. During the rest period mucus, which had been raised into the mouth or pharynx, was expectorated or removed by suction. This procedure was repeated eight times and was referred to as a treatment. Such treatments were carried out at one- to fourhour intervaIs, depending upon the quantity of secretions and the patient’s abiIity to cough spontaneousIy. RESULTS
The aIterations in bIood chemica1 findings of seven patients having EWNP between twenty and 130 minutes after the termination of anesthesia (average fifty-three minutes) are summarized in Table I. In the first coIumn of each group of figures appear the control vaIues for arteria1 blood pH, pCO,, BB+, and O2 saturation obtained immediateIy before exsufFIation. VaIues obtained during the Iast period of EWNP are recorded in the second 638
jects were acidotic due to miId respiratory acidosis (average pCOz 48 mm. Hg) and moderateIy severe metaboIic acidosis (average BB+ 40.4 mEq./L.). Each case showed some degree of arteria1 oxygen unsaturation. There was more variabiIity of this function than of the others; the saturations ranged from 78 to 95 per cent. EWNP consistently improved a11 measured functions except oxygen saturation. ArteriaI pH was eIevated an average of 0.09 pH units, whiIe pCOZ was decreased an average of IO mm. Hg. The aIterations of bIood buffer base were probably of IittIe physioIogic significance, but a11 were in the same direction and of the same magnitude. The arteria1 oxygen saturation feI1 during EWNP in two subjects and rose from 2 to 8 per cent in four. The average oxygen saturation during EWNP in this group of patients was 89.4 per cent. The vaIues taken six to ten minutes after EWNP show a11 functions returning toward contro1 IeveIs, with pH and buffer base stiI1 remaining eIevated to a sIight but a statisticaIIy significant degree. Three unanesthetized subjects with chronic acidosis were studied. Two of these (W. G. and M. K.) suffered from advanced puImonary emphysema and chronic respiratory insuffIciency. The effects of EWNP upon the arteria1 blood pH, pCOZ, BB+, and 0, saturation of
Postoperative
ExsuffIation
with Negative
procedure depends on maintenance c~f a GdeIJ patent airway. The exsuffIator contains a valve which instantaneously reverses the fiow of air betiveen the apparatus and the lungs, resulting in an abrupt expulsion of air and retained secretions from the lungs. The iInpoSiti(Jn of an>
these subjects are shown in Table II. A fall in pCO2 took place during EWNP of approximately the same extent as in the group of postAlterations of pH and anesthesia patients. buffer base were more variable. All three subjects sho\ved gross oxygen unsaturation before T.\BLE EFFECTS
OF
EWNP
ON
PATIENTS
Pressure
II
WITH
CHRONIC
PLIAI~NARY
DISE.ISE”
nztrrrc EWNP
G. II.
(;har,fy during EWNI’
ctrangc dtcr EWNI’
w. k
J (:.
obstruction, such as a partialI\, closed glottis, retracted tongue or closed lips, impairs the effkiency of EWNP. Barach et al.’ resolved these diffkulties in most instances II>- obtaining the cooperation of the conscious patient. No diffwulty \vas encountered in administering EWNP effectiveI>- to conscious patients in the present study after the patients and the professional staff had received appropriate instructions. Indeed, most of the patients were able to carry out the procedure by themselves \\-hen the apparatus was Ieft at the bedside. In the patients emerging from anesthesia a certain amount of skill, acquired through practice, was necessary to obtain a free air\vay and air-tight mask fit. It is of considerable interest that patients with \\-ounds of the abdomen or chest reported less wound pain during E%‘NP than during spontaneous coughing. In no case nas there disruption of an)- recently sutured \\cJUnd of the chest or abdomen, nor \\as there an?- complication folIowing treatment \vhich could be attributed to EWNP. Sex-era1 patients showed evidence of bullous emphysema prior TO treatment; in none of these n-as there clinical or s-ray change after EWNP to suggest enlargement or rupture Ol‘ bullae. One patient \vith myasthenia grnvis was subjected to extensi7.e surgeq- in\ olving the chest wall. Postopcrativc treatment with EWNP 1~3s eft’cctcd u ithout harmful incident. Since the norI\ of this report was concluded, two patients sul>iected to lobectomy had E\VNP postoperativeI>, I\-ith inflationary pressures limited to 20 mm. Hg. If excessive Iung inflation is a\-oidcd and if reflck
treatment. Although the arterial O2 saturation of two subjects was increased approximateI> of onIy one (J. C.) I; per cent, the 0, saturation reached a normal level. In this instance a significant degree of sustained improvement was shown in the post-treatment vaIue. With this exception, al1 measured functions returned toward pretreatment Ievels. The number of cases in which we observed the clinical effect of EWNP during the postoperative period was too smaI1 to justify tabulation and statistical analysis, yet certain genera1 observations can be made concerning the results. The most obvious benefit derived from the procedure was seen in those patients n-ho couId not or would not cough up secretions because of \vound pain. It was generalI>- found that \I-ithin tw:o to three hours after the first treatment mucopurulent sputum appeared. Improved breath sounds, increased percussion resonance, reduced respirator>- rate and ciearing of+-anosis were some of the signs frequently noted within t\veIve hours after beginning E1YNP. One patient with massive right lower lobe collapse twenty-four hours after th>:roidectomy demonstrated definite clinical evrdence of improved aeration a few hours after the start of hourly EWNP; within five days both lung fieIds \verc almost compIeteIy clear to x--w\- csaniination.
-&
&kC!tiVt?IKSS
of
EWN
P
ill
IXlll~\-ing
retained bronchia secretions from patients \vith fresh operative \I-ounds was cIearIy demonstrated in the present study. The success of the 639
WiIIiams
and HoIaday
protective contraction of the expiratory muscIes of the chest and abdomen is not stimulated, the rapid, extreme pressure change during exsuffIation with negative pressure does not appear to be hazardous. Despite the Iarge tidal volumes obtained during EWNP in the present study the pCOZ did not faII beIow 30 mm. Hg, and the arteria1 oxygen saturation rose above 90 per cent in onIy three of ten patients. Several factors may operate to produce these discrepancies. Since pCOz throughout the body couId not reach equiIibrium during the brief period of EWNP empIoyed, the values observed may represent increased deIivery of CO, from tissue depots. The exsumation apparatus contributes a potentia1 dead air space of 300 cc. between the mask and the exhaIation vaIve. Maintenance of an air-tight mask fit during the fina phases of exsuflIation and during the initia1 phase of inffation of the lung would resuIt in deIivery into the aIveoIi of approximateIy 500 ml. of expended air. This may have contributed to minimize the alterations of the bIood tensions of both CO2 and OZ. Low oxygen saturations which have been observed in the immediate postanesthetic period have been ascribed by Fink* to diIution of aIveoIar air, with subsequent Iowering of aIveoIar pCOZ, by outward diffusion of anesthetic gases. However, in order to produce this effect a gas wouId have to possess certain specific soIubiIity characteristics and be present in high concentration. The onIy such gas used in our patients was nitrous oxide. It was used in the concentration range mentioned by Fink in onIy one case. Since EWNP was applied an average of fifty-three minutes after the termination of administration of anesthetic gases, it is doubtful in any event that concentrations of anesthetic gases wouId be high enough to reduce aIveoIar oxygen tensions significantIy. The rapid bIowing off of carbon dioxide couId not have interfered with oxygenation, since the alveolar concentration of CO2 remained in the norma range of 5 per cent during EWNP. Cherniaks observed incomplete saturation of arteriaI blood during exsufflation without the use of negative pressure. He suggested that it might be due to “an increased ventiIation of normal alveoli occuring at the expense of ventiIation of maIfunctioning parts of the lung.” It seems IikeIy that the rapid flow rates developed during EWNP would favor earIy
expansion of those portions of the lung which have the Iowest resistance to flow. Overdistention of such areas through distortion of adjacent areas would increase the tendency toward uneven ventiIation. Assuming the mixed venous bIood to be 70 per cent saturated and blood returning from ventiIated aIveoIi to be IOO per cent saturated, faiIure to ventilate 24 per cent of the perfused aIveoIi wouId result in a mean arterial saturation of 80 per cent, which was the average saturation obtained during EWNP. SUMMARY I. ExsuffIation with negative pressure was useful in clearing retained bronchial secretions in twenty-two postoperative patients with or without puImonary atelectasis. 2. During the active period of treatment EWNP decreased postanesthetic acidosis by increasing elimination of CO2 through hyperventiIation. The arteria1 oxygen saturation was increased slightly in some cases and decreased in others. Following the use of EWNP, arterial blood gas vaIues reverted toward pretreatment levels promptly. REFERENCES
L., BECK, G. J. and SMITH, W. H. Mechanical production of Aow rates surpassing the capacity of human coughing. Am. J. M. SC., 226: 241, 1953. BARACH, A. L., BECK, G. J. and SPENIEK, M. ExsufFIation with negative pressure; physioIogica1 and clinica studies in poliomyelitis, bronchial asthma, pulmonary emphysema and bronchiectasis. Arch. Int. Med., 93: 825, 1954. HOLADAY, D. A. An improved method for multiple rapid determinations of arteria1 blood pH. J. Lab. u Clin. Med., 44: 149, 1954. GOLDSTEIN, F., GIBBON, J. H., JR. ALLBKITTEK, F. F.,JR.and STAYMAN, J. W., JR. The combined manometric determination of oxygen and carbon dioxide in bIood, in the presence of Iow concentrations of ethyI ether. J. Biol. Cbem., 182: 815, 1950. HOLADAY, D. A. and VEKOSKY, M. The manometric anaIysis of respiratory gases in bIood containing voIatiIe anesthetic agents. I. A comparison of macro-methods. J. Lab. @ CZin. Med. (in press). SINGER, R. B. and HASTINGS,A. B. An improved clinica method for the estimation of disturbances of the acid-base baIance of human bIood. Medicine, 27: 223, 1948. HOLADAY, D. A., MA, D. and PAPPER, E. M. Acidbase baIance during anesthesia. Bull. New York Acad. Med., 28: 543, 1952. FINK, B. R. Diffusion anoxia. Anesthesiology (in press). CHERNIAK, R. M. The effect of mechanical exsuffIation on respiratory gas exchange in chronic pulmonary emphysema. J. Clin. Investigation, 32: I 192,
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