Management of Chronic Alveolar Hypoventilation with Nasal Positive Pressure Breathing

function, flow should be redirected to the low-pressure, lowimpedance puhnonary circulation and the shunt should reverse from left-to-right or resolve. Right ventricular performance improves more rapidly than that of the left ventricle following acute ischemic injury, with reversal of depressed right ventricular ejection fraction within 72 hours of injury in 10 of 11 patients (91 percent). 17 Once hemodynamic stability has been achieved, the primary problem created by atrial septostomy is that of arterial hypoxemia. Efforts to improve oxygenation should be directed toward improving right ventricular function and decreasing pulmonary vascular resistance. A flow-directed pulmonary artery catheter may optimize hemodynamic management. Positive end-expiratory pressure may increase functional residual capacity and improve gas exchange; however, these benefits may occur at the expense of worsening hypoxemia as the degree of right-to-left shunting may increase with elevated pulmonary vascular resistance. Evaluation of the shunt by measuring the pulmonary vein (left atrial) to systemic artery oxygen stepdown excludes any puhnonary source of shunt or desaturation, and resolution of the stepdown in oxygen saturation is consistent with decreased right-to-Ieft shunting and improved right ventricular function. The potential problems of a residual atrial septal defect and paradoxic emboli are significant, but should be considered within the larger risk/benefit framework of right ventricular failure. ACKNOWLEDGMENT: Special thanks to Steven J. R. Phillips, M. D. for his encouragement in publishing this report, and to my wife Deborah for her support and assistance. REFERENCES

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Spence PA, Weisel RD, Salerno TA. Right ventricular failure: pathophysiology and treatment. Surgical Clinics of NA 1985; 65:689-97 Gonzalez AC, Brandon TA, Fortune RL, Casano SF, Martin M, Benneson DL, et al. Acute right ventricular failure is caused by inadequate right ventricular hypothermia. J Thorac Cardiovasc Surg 1985; 39:16-26 Christakis cr; Fremes SE, Weisel RD, Ivanov J, Madonik M, Seawright SJ, et al. Right ventricular dysfunction following cold potassium cardioplegia. J Thorac Cardiovasc Surg 1985; 90:243-50 Starr I. The absence of conspicuous increments of venous pressure after severe damage to the right ventricle of the dog, with a discussion of the relation between clinical congestive failure and heart disease. Am Heart J 1943; 26:291-301 Farrar OJ, Compton PG, Hershon JJ, Fonger JD, Hill JD. Right heart interaction with the mechanically assisted left heart. World J Surg, 1985; 9:89-102 Murphy DA, Marble AE, Landymore R, Dajee H. Assessment of the isolated right atrium as a pump. J Thorac Cardiovasc Surg 1978; 76:485-88 Vlahakes GJ, Turley K, Hoffman JI. The pathophysiology of failure in acute right ventricular hypertension: hemodynamic and biochemical correlations. Circulation 1981; 63:87-95 Cohn JR, Guha NH, Broder MI, Limas CJ. Right ventricular infarction. Am J Cardio11974; 33:209-14 Agarwal JB, Yamazaki H, Bodenheimer MM, Banka VS, Helfant RH. Effects of isolated interventricular septal ischemia on global and segmental function of the right and left ventricle. Am Heart J 1981; 102:654-63 Huyghens L, Dupont A, DeWilde PL, Defoer F: Transient tricuspid valve insufficiency following acute inferior myocardial infarction. Acta Cardiol 1986; 41:63-7

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11 D'Ambra MN, LaRaia PJ, Philbin OM, \Vatkins WD, Hilgenberg AD, Buckley MJ. Prostaglandin E 1, a new therapy for refractory right heart failure and pulmonary hypertension after mitral valve replacement. J Thorac Cardiovasc Surg 1985; 89:567-72 12 Hasselstrern LJ, Eliasen K, Mogensen T, Anderson JB. Lowering pulmonary artery pressure in a patient with severe acute respiratory failure. Inten Care Med 1985; 11:48-50 13 Opravil M, Gorman AJ, Krejcie TC, Michaelis LL, Moran JM. Pulmonary artery balloon counterpulsation for right ventricular failure: Experimental results. Ann Thorac Surg 1984; 38:242-53 14 Dembitsky W~ Daily PO, Raney AA, Moores WY, [oyo C'f Temporary extracorporeal support of the right ventricle. J Thorac Cardiovasc Surg 1986; 91:518-25 15 Brecher GA, Opdyke DF: The relief of acute right ventricular strain by the production of an interatrial septal defect. Circulation 1951; 4:496-502 16 Aris A. Commentary on: Pulmonary circulatory support. A quantitive comparison offour methods. J Thorac Cardiovasc Surg 1984; 88:963 17 Steele ~ Kirch D, Ellis J, Vogel R. Battock D. Prompt return to normal of depressed right ventricular ejection fraction in acute inferior infarction. Br Heart J 1977; 39:1319-23

Management of Chronic Alveolar Hypoventilation with Nasal Positive Pressure Breathing* Anthony F. DiMarco, M.D., F.C.C.P.; Alfred F. Connors, M.D., F.C.C.P.; and Murray D. Altose, M.D., F.C.C.P.

Negative pressure ventilation is the most common method of providing assisted ventilation without a tracheostomy. Unfortunately, negative pressure devices have several disadvantages and are not well tolerated by all patients. We present a patient in whom intermittent assisted ventilation was applied successfully by using a nasal mask to provide positive pressure ventilatory support.

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atients suffering from chronic respiratory failure secondary to neuromuscular disease or idiopathic hypoventilation may require intermittent assisted ventilation to sustain adequate spontaneous ventilation.!" The most common method of providing assisted ventilation without tracheostomy is by means of negative pressure ventilation using either a tank, cuirass, or body wrap ventilator. Unfortunately, these devices restrict patient mobility," can produce upper airway obstruction and, in the case of the cuirass or body wrap, produce only limited inspired volumes. 5 In the present report, we describe the successful use of a nasal mask to provide intermittent positive pressure ventilation for a patient with chronic respiratory failure in whom negative pressure ventilatory support was unsuccessful. CASE REPORT

A 25-year-old woman first presented to Cleveland Metropolitan *From the Department of Medicine, Cleveland Metropolitan General Hospital and Case Western Reserve University, Cleveland. Reprint requests: Dr. Di Marco, 3395 Scranton Road, Cleveland

44109

Management of Chronic Alveolar Hypoventilation (DiMarco, Connors, A/tose)

General Hospital in 1982 with idiopathic hypoventilation syndrome and a restrictive ventilatory defect secondary to kyphoscoliosis. Arterial blood gas determination demonstrated: PaOz, 84 mm Hg; PaCO z, 57 mm Hg and pH, 7.37 while breathing 1 L of oxygen by nasal cannula. Over several months , she developed progressive respiratory failure and eventually required intubation and positive pressure ventilatory support for a one-week period. She was subsequently supported with intermittent nasal oxygen and required a cuirass ventilator at night for a 14-month period . Over the next several years, she remained stable using only intermittent nasal oxygen. Arterial carbon dioxide tension levels during this period ranged between 52 and 65 mm Hg. In the eight weeks prior to admission in September, 1986, she noted the gradual onset of malaise, generalized weakness and dyspnea on exertion. Arterial blood gases drawn four weeks and one week prior to admission revealed Pco, values of68 and 74 mm Hg, respectively. The maximum inspiratory pressure was 100cmHzO and maximum expirator y pressure was 130 cmHzO. On September 19, 1986 she was admitted to the intensive care unit after arterial blood gases drawn in her physicians office showed : pH , 7.27; Pco ., 86 mm Hg, and Paz, 63 mm Hg on 1 L of oxygen by nasal cannula. On physical examination , she appeared chronically ill, but was in no acute distress . Her temperature was 37.3°C, blood pre ssure was 140/80 mm Hg, and respirations were 24/min and unlabored. She was alert and oriented. Examination of her head , eyes, ears , nose and throat revealed no abnormality. Lung fields were clear to auscultation and percussion. Cardi ac examination revealed normal heart sounds with no murmur or gallop. There was no peripheral cyanosis or edema. Hematocrit was 39.4 percent. Serum bicarbonate was elevated with a reciprocal decrease in serum chloride. The chest roentgenogram demonstrated moderate thoracolumbar scoliosis. The diagnostic impression was that of idiopathic hypoventilation syndrome and restrictive ventilatory defect se condary to kyphoscoliosis. She was placed in a tank ventilator, but tolerated it poorly. After one hour she became unresponsive and was noted to have clinical signs of upper airway obstruction. Arteri al blood gas levels revealed worsening respiratory acidosis. Since the patient steadfastly refused intubation, a body wrap ventilator was emplo yed, again causing marked hypoventilation. She eventuall y consented to intubation and mechanical ventilation. She was maintained on continuous ventilator y support for the next five days. On the sixth day, she was rapidly weaned to a T-piece. Arterial Pco, gradually rose and stabilized in the 55-59 mm Hg range over the first 24 hours . She was then extubated and treated with intermittent positive pressure breathing for 15 minutes every two hours during the day and continuous ventilation with a body wrap (Emerson) at night. On the second night , her Pco, rose to 95 mm Hg and the body wrap was discontinued. The average nighttime arterial Pco, rose as high as 102 mm Hg over the next few days. A formal sleep study demonstrated central depression of both upper airway and chest wall electrom yographic activity, particularly during REM sleep, without evidence of obstructive apnea. The patient refused tracheostomy and nighttime ventilatory support as a form of therapy. Therefore, an attempt was made to ventilate the patient by providing intermittent positive pressure ventilation through a tight fitting mask applied over the nose (Fig 1). The mask (Respironics model 302032) consisted of flexible, lightweight, form fitting plastic. Adjustable head bands were used to secure the mask firmly in place . This resulted in a nearly airtight seal of the mask to a Bennett PR2 pressure-cycled ventilator. The patient triggered her own breaths and therefore set her own respiratory rate. She received nasal positive pressure ventilation each night from U:OO PM to 7:00 A~ through the rest of her hospital stay. The resultant change in oxygen saturation and arterial Pco., both in the awake and sleeping state , are shown in Figure 2. Prior to nasal positive pressure ventilation, daytime and nighttime arterial Pco,

FIGURE 1. Nasal mask used to provide positive pressure ventilation . Straps around the head were used to secure the mask in place .

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FIGURE 2. Effect of nasal intermittent positive pressure breathing (NIPPB) on oxygen saturation and arterial Paz. Oxygen saturation values are represented by square symbols and are shown in the upper panel; arterial Pco, values are represented by circles and are shown in the lower panel. The open and closed symbols represent daytime and nighttime values, respectively. See text for further detail. CHEST I 92 I 5 I NOVEMBER, 1987

953

over a six-day period ranged from 71 to 81 and 86 to 102 mm Hg, respectively. Oxygen saturation remained above 85 percent during most of this time. With the use of nasal ventilation the average arterial Pco, fell progressively and stabilized at 59 mm Hg during the day and 62 to 64 mm Hg while asleep at night. Oxygen saturation remained consistently above 90 percent. Following discharge from the hospital, she continued nighttime nasal ventilation. Arterial blood gas measurements obtained 14 and 21 days after discharge, revealed an arterial Poo, of 51 mm Hg on both occasions. The patient was aware of increased mental alertness, increased strength and improved exercise tolerance. DISCUSSION

Chronic respiratory failure is a complication of end-stage chronic obstructive pulmonary disease and a frequent manifestation of severe neuromuscular diseases and idiopathic alveolar hypoventilation. Unlike acute respiratory failure, chronic stable alveolar hypoventilation of mild to moderate severity is generally not treated by mechanical ventilation with a positive pressure respirator, primarily because of the necessity for endotracheal intubation of tracheostomy. In recent years, however, there has been increasing use of negative pressure ventilation using tank, cuirass or bodywrap respirators to better regulate blood gas tension, to relieve respiratory muscle fatigue, and to avoid complications of alveolar hypoventilation such as cor pulmonale and polycythemia. The beneficial effects of intermittent negative pressure ventilation in certain patient populations has been well documented.!" Garay et al.' for example, described several patients with chronic alveolar hypoventilation secondary to a variety of neuromuscular disorders who were maintained for an average of ten years with nocturnal negative pressure ventilation. Unfortunately, negative pressure ventilators have several disadvantages. The iron lung is very bulky, extremely restrictive, and requires an attendant to assist the patient during its use. The cuirass and body wrap ventilators, while allowing patients considerably more mobility, are much less effective in generating adequate inspired volumes.?" This is particularly so in patients with marked derangements of respiratory system impedance. The most serious potential disadvantage of these devices is the occurrence of upper airway obstruction. While negative pressure applied to the chest wall results in negative intrathoracic pressure producing inspiratory airflow, it also produces negative pressure within the upper airway. If unopposed by the synchronous dilating action of upper airway muscle contraction, this negative pressure can result in collapse of the upper airway and obstructive apnea. This phenomenon has been described with negative pressure ventilation provided by phrenic nerve stimulation in patients with spinal cord injury," We believe this complication occurred in the patient under discussion and resulted in severe hypoventilation during her use of the tank and body wrap ventilators. This complication can be avoided by positive pressure ventilation. Positive airway pressure is thought to have a splinting action on the structures of the upper airway, thereby maintaining airway patency independent of upper airway muscle contraction. 8 Other potential problems of nasal positive pressure breathing are those inherent to positive pressure ventilation in general. These include barotrauma and possible hemo954

dynamic compromise, particularly in patients who may also have parenchymal lung disease. Supplemental oxygen and humidification may be necessary in some patients. Nasal positive pressure breathing may not be useful in all patients with chronic respiratory failure. In patients with partially obstructed nasal passages or excessive airway secretions, nasal breathing may prove unsuccessful. In addition, many patients may find the application of positive pressure to the nasal region or the requirement of a tight fitting mask very uncomfortable, precluding its successful use. Nasal positive pressure ventilation, however, may prove to be a useful means of ventilating selected patients who require intermittent support. Based upon our successful use of this method, we recommend a trial of nasal ventilation in patients who require intermittent ventilatory support but who cannot be adequately supported using negative pressure devices. ADDENDU~I

Since submission of the manuscript, repeated daytime arterial blood gas determinations at two months and five months following discharge revealed Pco, values of 57 and 60 mm Hg, respectively, and P0 2 values of 66 and 65 mm Hg, respectively. REFERENCES

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Garay S, Turino G, Goldring R. Sustained reversal of chronic hypercapnia in patients with alveolar hypoventilation syndromes; long term maintenance with non-invasive nocturnal mechanical ventilation. Am J Med 1981; 70:269-74 Weirs PWWJ, LeLoultre R, Dallinga 0'1: Van Dijil \V, Meinesa AF, Sluiter HJ. Cuirass respiratory treatment of chronic respiratory failure in scoliotic patients. Thorax 1977; 32:221-28 Cuiran FJ. Night ventilator by body respirators for patients in chronic respiratory failure due to late stage Duchenne muscular dystrophy. Arch Phys Med Rehabil1981; 62:270-74 Hill HS. Clinical applications of body ventilators. Chest 1986; 90:897-905 Collier CR, Offeldt JE. Ventilatory efficiency of the cuirass respirator in totally paralyzed chronic poliomyelitis patients. J Appl Physiol 1954; 6:532-38 Plum F, Lukas DS. An evaluation of the cuirass respirator in acute poliomyelitis patients with respiratory insufficiency. Am JMed Sci 1951; 221:417-24 Hyland RH, Hutcheon MA, Perl A, Bowes G, Anthonisen NR, Zamel N, et al. Upper airway obstruction induced by diaphragm pacing for primary alveolar hypoventilation: implications for the pathogenesis of obstructive sleep apnea. Am Rev Respir Dis 1981; 124:180-85 Strohl KE Cherniack NS, Gothe B. Physiologic basis of therapy for sleep apnea. Am Rev Respir Dis 1986; 134:791-802

Management of Familial Aortic Dissection* Thomas H. Marwick, M.B., B.S.; Stanley P. Woodhouse, M.B., Ch.S.; 1. Neil Birchley, M.B., B.S.; and Russell W Strong, M.B., B.S.

*From

the Departments of Cardiology and Surgery, Princess Alexandra Hospital, Woolloongabba, Queensland, Australia. Management of Familial Aortic Dissection (Marwick at all