Lung and chest wall mechanics in ventilated patients with end stage idiopathic pulmonary fibrosis

BACKGROUND Idiopathic pulmonary fibrosis is an inflammatory disease which leads to chronic ventilatory insufficiency and is characterised by a reduction in pulmonary static and dynamic volumes. It has been suggested that lung elastance may also be abnormally increased, particularly in end stage disease, but this has not been systematically tested. The aim of this study was to assess the respiratory mechanics during mechanical ventilation in patients affected by end stage disease. METHODS Respiratory mechanics were monitored in seven patients with idiopathic pulmonary fibrosis being ventilated for acute respiratory failure (Pao 2/Fio 2 5.8 (0.3); pH 7.28 (0.02); Paco 2 8.44 (0.82) kPa; tidal volume 3.4 (0.2) ml/kg; respiratory rate 35.1 (8.8) breaths/min) using an oesophageal balloon and airway occlusion during constant flow inflation. The total respiratory system mechanics (rs) was partitioned into lung (L) and chest wall (w) mechanics to measure static intrinsic positive end expiratory pressure (PEEPi), static (Est) and dynamic (Edyn) elastances, total respiratory resistance (Rrs), interrupter respiratory resistance (Rint,rs), and additional respiratory resistance (ΔRrs). RESULTS PEEPi was negligible in all patients. Edyn,rs and Est,rs were markedly increased (60.9 (7.3) and 51.9 (8.0) cm H2O/l, respectively), and this was due to abnormal lung elastance (dynamic 53.9 (8.0) cm H2O/l, static 46.1 (8.1) cm H2O/l) while chest wall elastance was only slightly increased. Rrs and Rint,rs were also increased above the normal range (16.7 (4.5) and 13.7 (3.5) cm H2O/l/s, respectively). RL and Rint,L contributed 88% and 89%, on average, to the total. Edyn,rs, Est,rs, Rrs and Rint,rs were significantly correlated with the degree of hypercapnia (r = 0.64 (p<0.01),r = 0.54 (p<0.05),r = 0.84 (p<0.001), andr = 0.72 (p<0.001), respectively). CONCLUSIONS The elastances and resistances of the respiratory system are significantly altered in ventilated patients with end stage idiopathic pulmonary fibrosis. These features are almost totally due to abnormalities in lung mechanics. These profound alterations in elastic and resistive mechanical properties at this stage of the disease may be responsible for the onset of hypercapnia.

[1]  S. Nava,et al.  Passive mechanics of lung and chest wall in patients who failed or succeeded in trials of weaning. , 1997, American journal of respiratory and critical care medicine.

[2]  J. R. West,et al.  Studies on respiratory mechanics and the work of breathing in pulmonary fibrosis. , 1959, The American journal of medicine.

[3]  J. Milic-Emili,et al.  Respiratory mechanics in anesthetized paralyzed humans: effects of flow, volume, and time. , 1989, Journal of applied physiology.

[4]  W A Zin,et al.  Respiratory mechanics during halothane anesthesia and anesthesia-paralysis in humans. , 1983, Journal of applied physiology: respiratory, environmental and exercise physiology.

[5]  R. Rudd,et al.  Cryptogenic fibrosing alveolitis. Relationships of pulmonary physiology and bronchoalveolar lavage to response to treatment and prognosis. , 1981, The American review of respiratory disease.

[6]  J. Myers,et al.  Idiopathic pulmonary fibrosis: clinical relevance of pathologic classification. , 1998, American journal of respiratory and critical care medicine.

[7]  A. Rossi,et al.  Respiratory mechanics during the first day of mechanical ventilation in patients with pulmonary edema and chronic airway obstruction. , 1988, The American review of respiratory disease.

[8]  J D Fulmer,et al.  Morphologic-physiologic correlates of the severity of fibrosis and degree of cellularity in idiopathic pulmonary fibrosis. , 1979, The Journal of clinical investigation.

[9]  N. Lapp,et al.  The effect of diffuse pulmonary fibrosis on lung mechanics. , 1981, Bulletin europeen de physiopathologie respiratoire.

[10]  E. Taskinen,et al.  Prognosis of cryptogenic fibrosing alveolitis. , 1983, Thorax.

[11]  W. Zin,et al.  Flow and volume dependence of pulmonary mechanics in anesthetized cats. , 1988, Journal of applied physiology.

[12]  W A Zin,et al.  A simple method for assessing the validity of the esophageal balloon technique. , 2015, The American review of respiratory disease.

[13]  M. Tavola,et al.  Pulmonary and chest wall mechanics in anesthetized paralyzed humans. , 1991, Journal of applied physiology.

[14]  J. Desmonts,et al.  Effects of tracheal suctioning on respiratory resistances in mechanically ventilated patients. , 1998, Chest.

[15]  A Rossi,et al.  Analysis of the behavior of the respiratory system with constant inspiratory flow. , 1985, Journal of applied physiology.

[16]  T. King,et al.  Idiopathic pulmonary fibrosis. Abnormalities in bronchoalveolar lavage fluid phospholipids. , 1988, The American review of respiratory disease.

[17]  R. Hyatt,et al.  Effects of anesthesia and muscle paralysis on respiratory mechanics in normal man. , 1973, Journal of applied physiology.

[18]  E. d’Angelo,et al.  Lung and chest wall mechanics in patients with acquired immunodeficiency syndrome and severe Pneumocystis carinii pneumonia. , 1997, The European respiratory journal.

[19]  N. Müller,et al.  Cryptogenic fibrosing alveolitis , 1997, The Lancet.

[20]  J. Bates,et al.  Partitioning of respiratory mechanics in mechanically ventilated patients undergoing pneumoperitoneum for laparoscopic surgery , 2000 .

[21]  V. Ranieri,et al.  Analysis of behavior of the respiratory system in ARDS patients: effects of flow, volume, and time. , 1991, Journal of applied physiology.

[22]  B. Heard,et al.  The prognosis of cryptogenic fibrosing alveolitis , 1972, British medical journal.

[23]  S. Nava,et al.  Patient-ventilator interaction and inspiratory effort during pressure support ventilation in patients with different pathologies. , 1997, The European respiratory journal.

[24]  J. Allen,et al.  Diffuse interstitial pneumonitis. Clinicopathologic correlations in 20 patients treated with prednisone/azathioprine. , 1978, The American journal of medicine.