Katharine J. Desmond

Immediate and long-term effects of chest physiotherapy in patients with cystic fibrosis

Both the immediate and long-term effects of chest physical therapy administered by a parent were evaluated in eight children with cystic fibrosis. Spirometric and plethysmographic evaluations were performed pre-CPT and at 5 and 30 minutes post-CPT. The pre-CPT measurements after a three-week period with no CPT were compared with the values while receiving CPT on a regular twice daily basis. There was a significant decrease after three weeks without CPT for FVC (P less than 0.025), FEV1 (P less than 0.005), FEF25-75 (P less than 0.005), and Vmax60TLC (P less than 0.025). When the patients had been receiving CPT on a regular basis, the only immediate effect was an increase in PEFR after 30 minutes post-CPT (P less than 0.05). After three weeks without CPT, there were increases at 30 minutes post-CPI for FVC (P less than 0.005) and Vmax60TLC (P less than 0.05). These findings indicate that although there may be little immediate functional improvement when CPT is received on a regular basis, a three-week period without CPT leads to a worsening of the functional status, which is reversed with renewal of regular CPT.

Is anti-Pseudomonas therapy warranted in acute respiratory exacerbations in children with cystic fibrosis?

A controlled study was designed to clarify the indications for antibiotic therapy in children with advanced cystic fibrosis hospitalized with respiratory exacerbations. Twenty-two children with severe CF and signs of acute lower respiratory infection were randomly assigned to receive either cloxacillin or carbenicillin plus gentamicin administered intravenously for ten days. Other aspects of therapy were constant. The groups were comparable in all respects and Pseudomonas aeruginosa was the predominant sputum pathogen in most patients. Clinical improvement, chest radiograph changes, evidence of airway obstruction, and bacteriologic flora of sputum were no different regardless of the regimen used. These results suggest that the use of anti-Pseudomonas medication in these children may not always be necessary. These observations need to be confirmed by blind-controlled studies in larger numbers of patients with mild as well as severe respiratory involvement.

Long-term pulmonary sequelae of premature birthwith and without idiopathic respiratory distress syndrome

Seven children born prematurely who survived the respiratory distress syndrome, seven children born prematurely who had no neonatal lung disease, and seven normal children born at term were studied by comparison of flow volume curves obtained while breathing air to those obtained while breathing 80% helium and 20% oxygen. Expiratory flow rates in air both groups of prematurely born children were lower than flow rates of the children born at term, and the volumes of iso-flow were higher in the survivors of RDS than those of the children born at term. The differences in flow rates in air suggest an increase in large airway resistance in both groups of prematurely born children. It is speculated that this may be secondary to growth retardation related to prematurity. The elevated Viso V in the RDS group suggests an increase in small airway resistance secondary to the disease or to its therapy.

Measuring the oxygen cost of breathing in normal adults and patients with cystic fibrosis

It has been suggested that the oxygen consumption of the respiratory muscles (VO2 resp) may play a role in limiting exercise performance in both healthy subjects and those with chronic airflow limitation (CAL). In order to measure VO2 resp reproducibly at both rest and on exercise, ventilation (VE) and total oxygen consumption (VO2) in 3 normal subjects and in 3 patients with cystic fibrosis were measured while breathing air and again when VE was stimulated by the addition of CO2 to the inspired gas. Since external work was the same it was assumed that any changes in VO2 would be due to the increase in VO2 resp during stimulated breathing allowing for the calculation of VO2 resp. The oxygen cost of breathing was higher in the patients with the increasing ventilation of exercise. These values were reproducible on repetitive measurements. It is concluded that the method employed is applicable in normal subjects and in patients with CAL, and that the O2 cost of breathing is higher in patients with CAL. The O2 cost of breathing increases as VE increases but even during exercise the VO2 resp is only a small fraction of the total VO2 and is unlikely to be a determining factor limiting exercise performance in either normal subjects or those with CAL.

Long-term pulmonary sequelae of theWilson-Mikity syndrome

Five children born prematurely, eight to ten years ago, who survived the Wilson-Mikity syndrome were compared with six apparently normal prematurely born children and eight normal children born at term, by means of flow volume curves obtained while breathing air and while breathing a mixture of 80% helium and 20% oxygen. The flow rates in air of the group who survived the Wilson-Mikity syndrome were significantly lower than those of the prematurely born normal children (P less than 0.01), and than those of the eight normal children (P less than 0.001). The volume of isoflow while breathing air compared to that while breathing HeO2 was highly variable, but not significantly different in the three groups. Three of the five survivors of the Wilson-Mikity syndrome had a marked concavity in the shape of their flow volume curves. It is concluded that these abnormalities are due to focal increases of compliance or resistances or both of terminal lung units and result in adjacent areas of the lung emptying at different rates. The relationship between physiologic and anatomic abnormalities seen at autopsy in those who die to the disease suggests that they are due to the same pathologic process. Whether or not these abnormalities will disappear with future lung growth remains to be seen.

1637 VENTILATION, RESPIRATORY CENTER OUTPUT AND CONTRIBUTION OF THE RIB CAGE AND ABDOMINAL COMPONENTS TO VENTILATION DURING CO2 REBREATHING IN CHILDREN WITH CYSTIC FIBROSIS (CF)

We investigated the respiratory response of CF patients to CO2 under hyperoxic conditions. Using a standard CO2 Read rebreathe technique, we studied 14 CF patients with mild to severe degrees of airway obstruction. We evaluated their response to CO2 in terms of their ventilation (VE), mean inspiratory flow rates (VT/Ti) and their occlusion pressures (P.1). In order to understand the contributions of the rib cage and abdominal components to ventilation (Vrc and Vab) we assessed the volume change in each compartment by the use of magnetometers. We found that, when normalized for the height of the child,the slope of VE vs end tidal CO2 (PETCO2),as well as the slope of VT/Ti vs PETCO2 correlated significantly with the forced expiratory flow between 25 and 75% of vital capacity (FEF25-75)(r=.78,p <.001 and r=.74, p<.01 respectively).The values for P.1 were within the normal range and did not correlate with the FEF25-75. The contribution of Vrc to the increases in VT with increasing VE was double that of Vab.The increasing Vrc correlated with the increasing VT (r=.88,p<.001).This predominance of Vrc is similar to that seen in normals. In conclusion, we have shown that tests involving a mechanical response to CO2 correlate with the FEF25-75. There is no evidence of abnormalities in the control of breathing.