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High Frequency, High Volume Ventilation for Right Ventricular Assist
High Frequency, High Volume Ventilation for Right Ventricular Assist* Jorge Serra, M.D.; Kathleen W McNicholas, M.D., F.C.C.P.; Roger Moore, M.D.; and Gerald M. Lemole, M.D., F.C.C.P.
During ventilation, the lungs may serve as accessory pumps for forward blood Bow 1,1 We have noted signi6cant hemodynamic improvement in several patients during short periods of vigorous hand ventilation with the Ambo bag and tried to reproduce the hemodynamic improvement in the management of four patients with profound low cardiac output syndrome secondary to right ventricular (RV)failure
following open heart surge~ High frequency, high volume (HFHV) ventilation resulted in improved hemodynamics in these patients, as evidenced by pulsatile pulmonary blood 80w and increased cardiac output. Right-sided stroke work was present and there was a faD in mean central venous pressure (CVP)and rise in mean pulmonary artery pressure
Management of the patient with profound low
Peripheral and core temperatures were measured. All patients were successfully weaned from cardiopulmonary bypass but had early (within 12 hours) postoperative low cardiac output despite the administration of inotropes and volume replacement Using a Bennett MAl ventilator, HFHV mechanical ventilation was instituted with tidal volumes of 20 to 30 mllkg with peak respiratory pressure not exceeding 40 em of water. Respiratory rate was determined as a submultiple of the heart rate (usually 30 to 60 per min), in an attempt to synchronize the inspiratory phase with ventricular systole as closely as possible. Maximum augmentation obtained in arterial wave form was used as a guide. Dead space was added to maintain PCOtat 30 to 40 torr. Pavulon was administered to all patients during HFHV ventilation.
cardiac output syndrome secondary to postoperative RV failure remains a challenge. Right ventricular dysfunction can be readily reversible if circulation is supported to provide time for recovery Few modalities are, however, currently available for clinical use. Early in our experience we cared for a child transported to the intensive care unit on partial bypass with the chest closed. In this patient we noted pulsatile arterial pressure tracing during periods ofHFHV hand ventilation. On normal ventilator settings the arterial How was linear. Mechanically ventilated lungs appear to function in this case as auxiliary pumps for forward blood How Encouraged by this experience and with an increasing understanding of cardiovascular pulmonary interaction in the normal state in Fontan circulation, and utilizing concepts of the new cardiopulmonary resuscitation, we further considered potential use of mechanical ventilation as a pump for pulmonary circulation. A technique of HFHV mechanical ventilation was used to manage patients with low cardiac output secondary to postoperative right ventricular failure. MATERIALS AND METHODS
The patients included four boys between the ages of three and five years and weighing 10.8 to 14.9 kg. One patient with double outlet right ventricle (DORV) and pulmonary stenosis underwent repair using a valveless conduit The other three patients with severe tetralogy of Fallot had extensive right ventricular outflow tract reconstruction with the use of transannular patches. Radial and femoral artery lines were placed and left atrial pressure was monitored. Cardiac output was determined by the thermodilution technique with catheters in the right atrium and pulmonary arter}'
*From the Medical College of Pennsylvania, Philadelphia. Manuscript received August 17; revision accepted December 4.
(pAP).
CASE
1
A four-year-old, 14.9 kg boy underwent repair of double outlet right ventricle with use of a valveless conduit Following surgery in spite of inotrope therapy (dopamine 15 glkWmin, epinephrine 0.05 glkWmin and isoproterenol 0.2 glkglmin) and adequate volume replacement, the patients cardiac index was only 1.6 UminlMl • Systolic blood pressure was 60 torr and mean CVP 20 torr. High frequency high volume ventilation was started at a rate of 60 breaths per minute with a tidal volume of 22 mllkg. Within an hour systolic blood pressure was 90 to 100 ton; cardiac index was 2.2 UminlM l and mean CVP 17 torr. After several hours of HRHV ventilation, the patient was returned to standard ventilation but shortly thereafter clinically deteriorated and suffered cardiac arrest. Though resuscitation was successful and the patient was maintained on HFHV ventilation with a return of hemodynamic stabili~ electroencephalogram showed cerebral silence. CASE 2
A 6ve-year-old, 13 kg boy underwent total correction of tetralogy of Fallot with transannular patch enlargement of the right ventricular outflow tract. Despite inotrope therapy (dopamine 10 glkWmin and isoproterenol 0.2 glkWmin) and adequate volume replacement, the patients systemic blood pressure was 70 torr, mean CVP 15 torr and cardiac index 1.7 Uminlml • The patient was placed on HVHF ventilation with a tidal volume of 20 mlIkg and a respiratory rate of 50 breaths per minute (one-third of the heart rate), There was an immediate hemodynamic improvement with an increase in systolic blood pressure to 94 torr and a fall in mean CVP to 12 torr. During the next three days, the patient progressively improved but all CHEST I 93 I 5 I MAY, 1988
1035
A
B
C D FIGURE 1. A = Electrocardiogram; B =systemic arterial tracing; C = pulmonary artery tracing; D =airway pressure. Demonstration of optimal pulmonary artery pressure augmentation with synchronization of the inspiratory phase of ventilation with cardiac systole (arrows ~ attempts to return to conventional ventilatory techniques were followed by deterioration in hemodynamics. On the fourth postoperative ~ the patient was weaned back to a ventilatory rate of 20 breaths per minute and a tidal volume of 10 mllkg. The patient was extubated on the seventh post-operative day. CASE 3
A three-year-old, 10.8 kg boy underwent repair of tetralogy of Fallot which included a transannular right ventricular outflow tract patch. In spite of inotrope therapy (including isoproterenol and dopamine) the patient continued to have poor right ventricular function with mean CVP pressures exceeding mean pulmonary artery pressures. Cardiac index was 2 Uminlml . There was increasing ascites, hepatomegaly and pleural effusions. HFHV ventilation was instituted with a tidal volume of30 mllkg at a rate of50 breaths per minute. Within four hours, cardiac index had increased to 4 Uminlml and the central venous pressure had fallen to 17 torr. Again, attempts to wean from this form of ventilation led to hemodynamic deterioration. Four days postoperatively the patient was weaned from HFHV ventilation and by the ninth postoperative day the patient was extubated. CASE 4
A fouJ'oyear-old, 14 kg boy underwent repair oftetralogy of Fallot which included a transannular right ventricular outflow tract patch. Postoperatively he required inotropic support with dopamine , dobutamine and isoproterenol, as well as volume replacement Despite these efIOrts, the patient had a low output state with increasing ascites and hepatomegaly. The patient was placed on HFHV ventilation with a tidal volume of 20 mllkg at a rate of 40 breaths per minute (one-third his heart rate) With this technique the patient had marked hemodynamic improvement with increase in urine output and fall in mean central venous pressure. His cardiac index increase to greater than 2.5 Uminlml • On the fourth postoperative day the patient was weaned from HFHV ventilation and was extubated on the ninth postoperative day. DISCUSSION
All patients had low output states secondary to right ventricular failure. Effective stroke work is defined as SVx (mean PA-mean CVP) x 0.0144 g-m." In our patients, PAP tracings were non-pulsatile and mean CVP exceeded mean pulmonary artery mean pressure; 1038
therefore, the RV work was zero to a negative value. The right ventricle functioned as a resistance rather than as an effective pump. If, as in our patients, mean CVP far exceeds mean PAp, the right ventricle may consume more work than it can produce. The concept of ventilation as a pump mechanism for pulmonary blood flow is not new. The inflationdeflation cycle of the lungs produces variations in pulmonary blood flow. In 1760, VonHaller described variation in pulmonary blood flow during inflation of the lungs.4 Yus postulated that vascular volume changes induced by respiration could result in a pumping action capable of contributing to forward pulmonary blood flow. In 1945, Macklin" demonstrated that the volume of blood in the pulmonary vasculature varies during inflation and recoil of the lungs. Larger pulmonary vessels (extraalveolar arteries and veins) undergo axial and transverse stretching with lung inflation, which increases their capacity. The capillaries, arterioles and venules (alveolar vessels) are flattened with inflation, which increases their capacity. Inspiration results in vascular diastole while expiration results in vascular systole. Pulmonary blood flow can be assisted and enhanced by the inspiratory-expiratory sequence of ventilation." Work contributed by ventilation may be significant when compared with the work of the normal or impaired right ventricle. Pressure-volume work in the normal right ventricle is small. The role of the right ventricle in maintaining circulatory adequacy remains in question as does its inclusion or exclusion.7 The concept of the dispensable right ventricle has led to the development of the Fontan type operation. In the Fontan procedure, venous return is directed into the pulmonary artery via a conduit or direct connection. There is no minimal early right ventricular contribution or right ventricular work. The right atrium is thought to contribute a High FI1lQU8!ICY, High Volume ventilation (SerrrJ et aI)
major portion of the work, as stated in the Fontan principle." Little propulsion of blood is necessary in this low-resistance circuit. In the Fontan circulation, pulmonary blood How is also dependent upon the L~ RA, SPVC and respiration. In an experimental model of right heart bypass,2 the inspiratory phase resulted in increased conduit How while during the expiratory phase there was a decrease in conduit How TIdal conduit How correlated with increasing tidal volume. Using an isolated lung preparation, Sade demonstrated that forward PBF occurred with ventilator variation with PA= LA. Thus, the Huctuation and pulmonary blood How volume during normal ventilation may act as an auxiliary pump in patients with atrioventricular bypass for the Fontan circulation. In the Fontan circulation, the right ventricle is replaced by a conduit During ventricular fibrillation, the entire heart functions as a conduit The work of circulation in a fibrillating heart can be maintained by CPR.9 During periods of low intrathoracic pressure, blood passes into the pulmonary circuit; during periods of high intrathoracic pressure, it passes through the left side. I Resuscitation techniques that exploit the thoracic pump mechanism are capable of maintaining circulation in the dog model. Mechanical ventilation with resultant changes in intrapleural pressure and intrapulmonary blood volume may permit the lungs to function as a type of pump which contributes and augments PBF and may assist the right heart. I The thoracic pump also provides unidirectional blood How after tricuspid valve closure. The auxiliary pump functions with Huctuations in pulmonary blood volume. Earlier in our experience we noticed this beneficial effect only with the chest closed. This encouraged us to use this technique in the postoperative period. In our patients, there is marked improvement in hemodynamic parameters shortly after institution of HFHV ventilation. In all of them there was an early clinical improvement and mean CVP became less than mean PAP. Early attempts to stop HFHV ventilation resulted in rapid clinical deterioration in all patients and cardiac arrest in one. All patients were therefore maintained on HFHV ventilation for three to four days until there was evidence of right ventricular function. Weaning was then successfully accomplished and all did well hemodynamically Synchronization with the heart beat
and ventricular systole appeared in our patients to augment pulmonary blood How (PVF) (Fig 1) and supported previous work of Carlon et allO and Birtwell. I At this point we used a submultiple of the heart rate as the ventilatory frequency and we "eyeball" the arterial wave" forms in order to obtain maximum augmentation. We are considering the addition of a solonoid circuit which will trigger the ventilator from the ECG. This alteration will require Food and Drug Administration approval. CONCLUSIONS
HFHV mechanical ventilation in our patients resulted in pulsatile PBF and improved hemodynamics, perhaps secondary to a pump effect supporting the right ventricle. HVHF ventilation is an important tool that may benefit patients with right heart failure resistant to conventional therapy A trial period of hand bag ventilation may help to identify the patients that could benefit from the use of this technique. REFERENCES
1 Birtwell WC, Soroff HS, Sachs BF: Levine HJ, Deterling R. Assisted circulation: the use of the lungs as a pump. A method tor assisting pulmonary blood flow by varying airway pressure synchronously with EKG. 'Irans Soc Art Intern Organs 1963; 9:192-201 2 Sade RM, Lubbe JJ, Simpser MD, Streider OJ. Mechanical ventilation as a pump tor the pulmonary circulation. Eur Surg Res 1981; 13:414-26 3 Bull C, deLeval MR, Stark J, 11lylor JF, Macartney FJ. Use of a subpulmonary ventricular chamber in the Fontan circulation. J Thorac Cardiovasc Surg 1983; 85:21-31 4 \bnHaller A Elements physiologia humani, vol 3, Lusanne Bousquet, 1760. Cited by: Cournand A. Air and blood. In: Fishman ~ Richards D~ eels. Circulation of the blood: men and ideas. New York: Oxford Univenity Press, 1964; 3-70 5 Yu PN. Pulmonary blood volume in health and disease. Philadelphia: Lea ~ Febiger, 1969; 126-27 6 Macklin CC. Evidences of increase in the capacity of the pulmonary arteries and veins of dogs, cats and rabbits during inflation of the freshly excised lung. Rev Canad BioI 1946; 5:199 7 Sade RM, Castenada AR. The dispensable right ventricle. Surgery 1975; 77:624-31 8 Fontan F, Baudet E. Surgical repair of tricuspid atresia. Thorax 1971; 26:240-48 9 Babbs CIt: New Versus old theories of blood flow during CPR. Crit Care Med 1980; 8:191-96 10 Carlon GS, Ray C, Pierri MK, Groeger J, Howland WS. High frequency jet ventilation-theoretical considerations and clinical observations. Chest 1982; 81:350-54
CHEST I 93 I 5 I MAY. 1988
1037
During ventilation, the lungs may serve as accessory pumps for forward blood Bow 1,1 We have noted signi6cant hemodynamic improvement in several patients during short periods of vigorous hand ventilation with the Ambo bag and tried to reproduce the hemodynamic improvement in the management of four patients with profound low cardiac output syndrome secondary to right ventricular (RV)failure
following open heart surge~ High frequency, high volume (HFHV) ventilation resulted in improved hemodynamics in these patients, as evidenced by pulsatile pulmonary blood 80w and increased cardiac output. Right-sided stroke work was present and there was a faD in mean central venous pressure (CVP)and rise in mean pulmonary artery pressure
Management of the patient with profound low
Peripheral and core temperatures were measured. All patients were successfully weaned from cardiopulmonary bypass but had early (within 12 hours) postoperative low cardiac output despite the administration of inotropes and volume replacement Using a Bennett MAl ventilator, HFHV mechanical ventilation was instituted with tidal volumes of 20 to 30 mllkg with peak respiratory pressure not exceeding 40 em of water. Respiratory rate was determined as a submultiple of the heart rate (usually 30 to 60 per min), in an attempt to synchronize the inspiratory phase with ventricular systole as closely as possible. Maximum augmentation obtained in arterial wave form was used as a guide. Dead space was added to maintain PCOtat 30 to 40 torr. Pavulon was administered to all patients during HFHV ventilation.
cardiac output syndrome secondary to postoperative RV failure remains a challenge. Right ventricular dysfunction can be readily reversible if circulation is supported to provide time for recovery Few modalities are, however, currently available for clinical use. Early in our experience we cared for a child transported to the intensive care unit on partial bypass with the chest closed. In this patient we noted pulsatile arterial pressure tracing during periods ofHFHV hand ventilation. On normal ventilator settings the arterial How was linear. Mechanically ventilated lungs appear to function in this case as auxiliary pumps for forward blood How Encouraged by this experience and with an increasing understanding of cardiovascular pulmonary interaction in the normal state in Fontan circulation, and utilizing concepts of the new cardiopulmonary resuscitation, we further considered potential use of mechanical ventilation as a pump for pulmonary circulation. A technique of HFHV mechanical ventilation was used to manage patients with low cardiac output secondary to postoperative right ventricular failure. MATERIALS AND METHODS
The patients included four boys between the ages of three and five years and weighing 10.8 to 14.9 kg. One patient with double outlet right ventricle (DORV) and pulmonary stenosis underwent repair using a valveless conduit The other three patients with severe tetralogy of Fallot had extensive right ventricular outflow tract reconstruction with the use of transannular patches. Radial and femoral artery lines were placed and left atrial pressure was monitored. Cardiac output was determined by the thermodilution technique with catheters in the right atrium and pulmonary arter}'
*From the Medical College of Pennsylvania, Philadelphia. Manuscript received August 17; revision accepted December 4.
(pAP).
CASE
1
A four-year-old, 14.9 kg boy underwent repair of double outlet right ventricle with use of a valveless conduit Following surgery in spite of inotrope therapy (dopamine 15 glkWmin, epinephrine 0.05 glkWmin and isoproterenol 0.2 glkglmin) and adequate volume replacement, the patients cardiac index was only 1.6 UminlMl • Systolic blood pressure was 60 torr and mean CVP 20 torr. High frequency high volume ventilation was started at a rate of 60 breaths per minute with a tidal volume of 22 mllkg. Within an hour systolic blood pressure was 90 to 100 ton; cardiac index was 2.2 UminlM l and mean CVP 17 torr. After several hours of HRHV ventilation, the patient was returned to standard ventilation but shortly thereafter clinically deteriorated and suffered cardiac arrest. Though resuscitation was successful and the patient was maintained on HFHV ventilation with a return of hemodynamic stabili~ electroencephalogram showed cerebral silence. CASE 2
A 6ve-year-old, 13 kg boy underwent total correction of tetralogy of Fallot with transannular patch enlargement of the right ventricular outflow tract. Despite inotrope therapy (dopamine 10 glkWmin and isoproterenol 0.2 glkWmin) and adequate volume replacement, the patients systemic blood pressure was 70 torr, mean CVP 15 torr and cardiac index 1.7 Uminlml • The patient was placed on HVHF ventilation with a tidal volume of 20 mlIkg and a respiratory rate of 50 breaths per minute (one-third of the heart rate), There was an immediate hemodynamic improvement with an increase in systolic blood pressure to 94 torr and a fall in mean CVP to 12 torr. During the next three days, the patient progressively improved but all CHEST I 93 I 5 I MAY, 1988
1035
A
B
C D FIGURE 1. A = Electrocardiogram; B =systemic arterial tracing; C = pulmonary artery tracing; D =airway pressure. Demonstration of optimal pulmonary artery pressure augmentation with synchronization of the inspiratory phase of ventilation with cardiac systole (arrows ~ attempts to return to conventional ventilatory techniques were followed by deterioration in hemodynamics. On the fourth postoperative ~ the patient was weaned back to a ventilatory rate of 20 breaths per minute and a tidal volume of 10 mllkg. The patient was extubated on the seventh post-operative day. CASE 3
A three-year-old, 10.8 kg boy underwent repair of tetralogy of Fallot which included a transannular right ventricular outflow tract patch. In spite of inotrope therapy (including isoproterenol and dopamine) the patient continued to have poor right ventricular function with mean CVP pressures exceeding mean pulmonary artery pressures. Cardiac index was 2 Uminlml . There was increasing ascites, hepatomegaly and pleural effusions. HFHV ventilation was instituted with a tidal volume of30 mllkg at a rate of50 breaths per minute. Within four hours, cardiac index had increased to 4 Uminlml and the central venous pressure had fallen to 17 torr. Again, attempts to wean from this form of ventilation led to hemodynamic deterioration. Four days postoperatively the patient was weaned from HFHV ventilation and by the ninth postoperative day the patient was extubated. CASE 4
A fouJ'oyear-old, 14 kg boy underwent repair oftetralogy of Fallot which included a transannular right ventricular outflow tract patch. Postoperatively he required inotropic support with dopamine , dobutamine and isoproterenol, as well as volume replacement Despite these efIOrts, the patient had a low output state with increasing ascites and hepatomegaly. The patient was placed on HFHV ventilation with a tidal volume of 20 mllkg at a rate of 40 breaths per minute (one-third his heart rate) With this technique the patient had marked hemodynamic improvement with increase in urine output and fall in mean central venous pressure. His cardiac index increase to greater than 2.5 Uminlml • On the fourth postoperative day the patient was weaned from HFHV ventilation and was extubated on the ninth postoperative day. DISCUSSION
All patients had low output states secondary to right ventricular failure. Effective stroke work is defined as SVx (mean PA-mean CVP) x 0.0144 g-m." In our patients, PAP tracings were non-pulsatile and mean CVP exceeded mean pulmonary artery mean pressure; 1038
therefore, the RV work was zero to a negative value. The right ventricle functioned as a resistance rather than as an effective pump. If, as in our patients, mean CVP far exceeds mean PAp, the right ventricle may consume more work than it can produce. The concept of ventilation as a pump mechanism for pulmonary blood flow is not new. The inflationdeflation cycle of the lungs produces variations in pulmonary blood flow. In 1760, VonHaller described variation in pulmonary blood flow during inflation of the lungs.4 Yus postulated that vascular volume changes induced by respiration could result in a pumping action capable of contributing to forward pulmonary blood flow. In 1945, Macklin" demonstrated that the volume of blood in the pulmonary vasculature varies during inflation and recoil of the lungs. Larger pulmonary vessels (extraalveolar arteries and veins) undergo axial and transverse stretching with lung inflation, which increases their capacity. The capillaries, arterioles and venules (alveolar vessels) are flattened with inflation, which increases their capacity. Inspiration results in vascular diastole while expiration results in vascular systole. Pulmonary blood flow can be assisted and enhanced by the inspiratory-expiratory sequence of ventilation." Work contributed by ventilation may be significant when compared with the work of the normal or impaired right ventricle. Pressure-volume work in the normal right ventricle is small. The role of the right ventricle in maintaining circulatory adequacy remains in question as does its inclusion or exclusion.7 The concept of the dispensable right ventricle has led to the development of the Fontan type operation. In the Fontan procedure, venous return is directed into the pulmonary artery via a conduit or direct connection. There is no minimal early right ventricular contribution or right ventricular work. The right atrium is thought to contribute a High FI1lQU8!ICY, High Volume ventilation (SerrrJ et aI)
major portion of the work, as stated in the Fontan principle." Little propulsion of blood is necessary in this low-resistance circuit. In the Fontan circulation, pulmonary blood How is also dependent upon the L~ RA, SPVC and respiration. In an experimental model of right heart bypass,2 the inspiratory phase resulted in increased conduit How while during the expiratory phase there was a decrease in conduit How TIdal conduit How correlated with increasing tidal volume. Using an isolated lung preparation, Sade demonstrated that forward PBF occurred with ventilator variation with PA= LA. Thus, the Huctuation and pulmonary blood How volume during normal ventilation may act as an auxiliary pump in patients with atrioventricular bypass for the Fontan circulation. In the Fontan circulation, the right ventricle is replaced by a conduit During ventricular fibrillation, the entire heart functions as a conduit The work of circulation in a fibrillating heart can be maintained by CPR.9 During periods of low intrathoracic pressure, blood passes into the pulmonary circuit; during periods of high intrathoracic pressure, it passes through the left side. I Resuscitation techniques that exploit the thoracic pump mechanism are capable of maintaining circulation in the dog model. Mechanical ventilation with resultant changes in intrapleural pressure and intrapulmonary blood volume may permit the lungs to function as a type of pump which contributes and augments PBF and may assist the right heart. I The thoracic pump also provides unidirectional blood How after tricuspid valve closure. The auxiliary pump functions with Huctuations in pulmonary blood volume. Earlier in our experience we noticed this beneficial effect only with the chest closed. This encouraged us to use this technique in the postoperative period. In our patients, there is marked improvement in hemodynamic parameters shortly after institution of HFHV ventilation. In all of them there was an early clinical improvement and mean CVP became less than mean PAP. Early attempts to stop HFHV ventilation resulted in rapid clinical deterioration in all patients and cardiac arrest in one. All patients were therefore maintained on HFHV ventilation for three to four days until there was evidence of right ventricular function. Weaning was then successfully accomplished and all did well hemodynamically Synchronization with the heart beat
and ventricular systole appeared in our patients to augment pulmonary blood How (PVF) (Fig 1) and supported previous work of Carlon et allO and Birtwell. I At this point we used a submultiple of the heart rate as the ventilatory frequency and we "eyeball" the arterial wave" forms in order to obtain maximum augmentation. We are considering the addition of a solonoid circuit which will trigger the ventilator from the ECG. This alteration will require Food and Drug Administration approval. CONCLUSIONS
HFHV mechanical ventilation in our patients resulted in pulsatile PBF and improved hemodynamics, perhaps secondary to a pump effect supporting the right ventricle. HVHF ventilation is an important tool that may benefit patients with right heart failure resistant to conventional therapy A trial period of hand bag ventilation may help to identify the patients that could benefit from the use of this technique. REFERENCES
1 Birtwell WC, Soroff HS, Sachs BF: Levine HJ, Deterling R. Assisted circulation: the use of the lungs as a pump. A method tor assisting pulmonary blood flow by varying airway pressure synchronously with EKG. 'Irans Soc Art Intern Organs 1963; 9:192-201 2 Sade RM, Lubbe JJ, Simpser MD, Streider OJ. Mechanical ventilation as a pump tor the pulmonary circulation. Eur Surg Res 1981; 13:414-26 3 Bull C, deLeval MR, Stark J, 11lylor JF, Macartney FJ. Use of a subpulmonary ventricular chamber in the Fontan circulation. J Thorac Cardiovasc Surg 1983; 85:21-31 4 \bnHaller A Elements physiologia humani, vol 3, Lusanne Bousquet, 1760. Cited by: Cournand A. Air and blood. In: Fishman ~ Richards D~ eels. Circulation of the blood: men and ideas. New York: Oxford Univenity Press, 1964; 3-70 5 Yu PN. Pulmonary blood volume in health and disease. Philadelphia: Lea ~ Febiger, 1969; 126-27 6 Macklin CC. Evidences of increase in the capacity of the pulmonary arteries and veins of dogs, cats and rabbits during inflation of the freshly excised lung. Rev Canad BioI 1946; 5:199 7 Sade RM, Castenada AR. The dispensable right ventricle. Surgery 1975; 77:624-31 8 Fontan F, Baudet E. Surgical repair of tricuspid atresia. Thorax 1971; 26:240-48 9 Babbs CIt: New Versus old theories of blood flow during CPR. Crit Care Med 1980; 8:191-96 10 Carlon GS, Ray C, Pierri MK, Groeger J, Howland WS. High frequency jet ventilation-theoretical considerations and clinical observations. Chest 1982; 81:350-54
CHEST I 93 I 5 I MAY. 1988
1037