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Communications to the Editor |

Pectus and Hypoventilation FREE TO VIEW

Philip Glassner, MD; John R. Bach, MD, FCCP
Author and Funding Information

Affiliations: University of Medicine & Dentistry of New Jersey Newark, NJ,  Seton Hall University South Orange, NJ

Correspondence to: John R. Bach, MD, FCCP, Department of Physical Medicine and Rehabilitation, University Hospital, B-403, 150 Bergen St, Newark, NJ 07103-2406; e-mail: bachjr@umdnj.edu



Chest. 2002;121(2):664-665. doi:10.1378/chest.121.2.664-b
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To the Editor:

We read with interest a recent article in CHEST (June 2001)1that considered pectus excavatum as the cause of hypercapnic respiratory failure. Patients with generalized neuromuscular weakness that results in scoliosis, such as those with Duchenne muscular dystrophy2and those with pectus due to the generalized weakness associated with spinal muscular atrophy type 1 (SMA1),3 develop hypercapnic respiratory failure. Also, even when not associated with generalized weakness, thoracic deformity from kyphoscoliosis, when severe enough, itself can result in hypoventilation. However, in the cases of patients with Duchenne muscular dystrophy and SMA1, the ultimate cause of the skeletal impairment is muscular. Likewise, idiopathic scoliosis may be due to paraspinal muscle weakness, just as the pectus in these patients may be due to, or at least may be associated with, intercostal muscular impairment. Although diaphragmatic function was tested in these patients with pectus, the values of the sniff test were not given. An assessment of maximum inspiratory pressures would reflect the strength of inspiratory muscles, including those of the rib cage. If the root cause of the problem is an underlying muscular impairment, then the hypercapnia may be due more to that condition, and the pectus deformity may be only secondary, just as it is for patients with SMA1. The fact that the patient had a history of being easily fatigued and frail as a child implies a possible neurologic or muscular disorder that worsened with time.

It is also unclear when the pectus began. Just as for SMA1 patients whose pectora resolve once they are placed on nocturnal high-span bilevel pressure ventilation, this patient’s pectus may have been milder had high-span bilevel ventilation been instituted much earlier. It is of concern that, despite the rigidity of the chest wall in this patient and the severity of the pectus, only low bilevel spans were used. We suspect that, had this patient been introduced to noninvasive ventilation at adequate levels long ago, hypercapnic respiratory failure would not have developed. We are also concerned about oxygen supplementation, and we suggest that the patient should use increasing periods of daytime ventilatory support via a mouthpiece to normalize alveolar ventilation rather than oxygen therapy, which entails a risk of developing increasingly severe hypercapnia.

References

Theerthakari, R, El-Halees, W, Jvadpoor, S, et al (2001) Severe pectus excavatum associated with cor pulmonale and chronic respiratory acidosis in a young woman.Chest119,1957-1961. [CrossRef]
 
Bach, JR, Ishikawa, Y, Kim, H Prevention of pulmonary morbidity for patients with Duchenne muscular dystrophy.Chest1997;112,1024-1028. [CrossRef]
 
Bach, JR, Niranjan, V Spinal muscular atrophy type 1: a noninvasive respiratory management approach.Chest2000;117,1100-1105. [CrossRef]
 
To the Editor:

We appreciate the comments about our case report.1 Regarding the possibility of a neuromuscular disease as the cause of our patient’s pectus deformity, there is no clinical evidence for any such disorder in our patient. Her neuromuscular system is entirely normal. Muscle power and deep tendon reflexes are within normal limits. She is able to generate a negative inspiratory force of 60 cm, and the sniff test has excluded the possibility of diaphragmatic weakness, as she could move both her diaphragms for at least one intercostal space. Advanced neuromuscular disease during childhood usually leads to considerable deformity of the spine and the trunk. Our patient is devoid of any other deformities except for severe pectus excavatum.

As regards the onset of pectus, our patient had been aware of this abnormality since approximately 12 years of age, but she denies having had any medical checkup or follow-up while in her native country. Since her immigration to the United States > 9 years ago, she had not had any medical evaluation until her hospitalization last year, when she came to our attention for the first time.

Employing noninvasive, bilevel pressure ventilation (inspiratory pressure of 12 cm) and low-flow oxygen, we were able to improve her hypercapnia and hypoxemia while maintaining a balanced arterial pH. Higher levels of inspiratory pressures may be appropriate if the result from lower pressures is unsatisfactory. Patients with acute-on-chronic respiratory acidosis develop posthypercapnic metabolic alkalosis if alveolar ventilation is increased by overzealous ventilatory support. Meticulous care was taken to prevent this complication. One goal of therapy is to correct hypoxemia and balance the arterial pH. Overcorrection of hypoxemia (Pao2 > 65 mm Hg), which is obviously the authors’ concern, was avoided by appropriate monitoring of gas exchange.

The authors are probably correct in the speculation that the patient would have benefited from earlier intervention with bilevel pressure ventilation. We successfully utilized an inspiratory pressure of 12 cm, which is within the range used in most cases of hypercapnic respiratory failure treated with noninvasive ventilation. Nevertheless, we feel that the recommendation to use high-span bilevel pressure ventilation is an excellent idea, which we intend to institute with this patient to see if it results in further improvement in hypercapnia without inducing significant metabolic alkalosis, and to see if the need for supplemental oxygen can be obviated.

References
Theerthakari, R, El-Halees, W, Javadpoor, S, et al Severe pectus excavatum associated with cor pulmonale and chronic respiratory acidosis in a young woman.Chest2001;119,1957-1961. [CrossRef]
 

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References

Theerthakari, R, El-Halees, W, Jvadpoor, S, et al (2001) Severe pectus excavatum associated with cor pulmonale and chronic respiratory acidosis in a young woman.Chest119,1957-1961. [CrossRef]
 
Bach, JR, Ishikawa, Y, Kim, H Prevention of pulmonary morbidity for patients with Duchenne muscular dystrophy.Chest1997;112,1024-1028. [CrossRef]
 
Bach, JR, Niranjan, V Spinal muscular atrophy type 1: a noninvasive respiratory management approach.Chest2000;117,1100-1105. [CrossRef]
 
Theerthakari, R, El-Halees, W, Javadpoor, S, et al Severe pectus excavatum associated with cor pulmonale and chronic respiratory acidosis in a young woman.Chest2001;119,1957-1961. [CrossRef]
 
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