PubMed · 10418529
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P Carroll. 1999. Revolutions. Continuous spirometry.. https://pubmed.ncbi.nlm.nih.gov/10418529/
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This study investigated changes in lung function, hydroxyproline (OH-pro) content of lung tissue and histopathology in anesthetized, spontaneously breathing rats after a single, selective irradiation of the right hemithorax with a single dose of 20 Gy. The objective of this animal model was to examine as to whether non-invasive lung function measurements (LFM) could be used to analyze the magnitude of the irradiation-related pneumonitis and its long-term sequel occurring in the right lung in the presence of a normal left lung. Four months after irradiation, the OH-pro content in the irradiated right lung was determined and compared with the non-irradiated contralateral left lung, as well as lungs from non-irradiated sham controls. LFM revealed significantly depressed flow-volume curves and reduced quasistatic compliance, suggesting a marked diminution of elastic recoil of the lung. Total lung capacity (TLC) was significantly decreased, while the residual volume (RV) and functional residual capacity (FRC) remained almost unchanged. One of the most predominant dysfunction of the lung was a severe maldistribution of ventilation shown by the single-breath N(2)-wash-out test. Single-breath carbon monoxide diffusing capacity (Dlco) was significantly decreased. The content of OH-pro, a marker of increased collagen, was significantly increased in the irradiated right lung but was indistinguishable from sham controls in the non-irradiated left lung. Histopathological examinations provided evidence of both inflammatory and fibrotic lesions in the irradiated lobes, including bronchiolo-alveolar hyperplasia. No changes were observed in the non-irradiated left lung. In summary, effects observed in the irradiated right lung were largely consistent with effects described in other animal models of human interstitial pulmonary fibrosis. Non-invasive LFM were considered to be particularly sensitive to study the overall extent of changes, however, the interpretation of findings appears to be complicated by the lobar heterogeneity of tissue- and flow-related functional end points.
SUMMARY. Recent introduction of the raised lung volume rapid thoraco-abdominal compression (RVRTC) technique for measuring forced expiratory maneuvers in infants provides the potential opportunity to assess respiratory mechanics simultaneously by using multiple linear regression (MLR) of the relaxed breaths preceding jacket inflation to force expiration. This study was undertaken to investigate whether data obtained from raised lung volume are influenced by placement of the rapid thoraco-abdominal compression (RTC) squeeze jacket. Paired measurements of tidal volume (V(T)) and respiratory rate (RR) during tidal breathing, and of inflation volume (V(inf)), respiratory system compliance (C(rs)), and resistance (R(rs)) during passive lung inflations were made in 60 (30 male) healthy term infants with and without a fastened, but uninflated RTC jacket in place. Jacket placement was associated with a significant reduction (P < 0.0001) in weight-corrected V(inf) [-1.86 (95% confidence interval, -2.46, -1.27) mL.kg(-1)] and C(rs) [-0.77 (-1.04, -0.49) mL.kPa(-1).kg(-1)]. This represented a reduction in weight-corrected C(rs) from 9.00 to 8.24 mL.kPa(-1).kg(-1), with the fall being >10% in 42% of infants studied. There was no significant change in R(rs) or weight-corrected V(T). If passive respiratory mechanics are to be measured during raised lung volume maneuvers, they should be performed prior to the jacket being fastened, unless considerable care is taken with each infant to ensure that the jacket does not restrict chest wall movement during maximum inflation.
Measurement of bronchial airway responsiveness requires noninvasive techniques in young children. The study was designed to examine the changes in resistance as measured using the interrupter technique (Rint) at the dose of methacholine (M) that induced a fall in transcutaneous partial pressure in O2 (P(tc)O2) > or = 20% (PD(20)P(tc)O2) in young children. Rint was calculated using the linear back-extrapolation method (Rint(L)) and the end-interrupter method (Rint(EI)). Twenty-two children (mean age, 5.2 +/- 1.1 years; range, 3.4 - 7.1 years) with nonspecific respiratory symptoms (mainly chronic cough, n = 17) were tested. P(tc)O2, Rint(L), and Rint(EI) were measured before the test, after saline challenge (baseline (B)), after each dose of M delivered by a dosimeter, and after bronchodilator (BD) inhalation. P(tc)O2 decreased significantly during M challenge, from 85 +/- 6 mmHg (B) to 62 +/- 9 mmHg (P < 0.05), and increased after BD inhalation, to 82 +/- 8 mmHg. Rint(L) and Rint(EI) increased significantly during M challenge, from 0.94 +/- 0.2 KPa/L/s and 1.11 +/- 0.19 KPa/L/s (B) to 1.27 +/- 0.35 KPa/L/s and 1.47 +/- 0.37 KPa/L/s, respectively (P < 0.05), and decreased after BD inhalation to 0.80 +/- 0.17 KPa/L/s and 0.95 +/- 0.18 KPa/L/s, respectively. Nineteen of 22 children reached the PD(20)P(tc)O2 at a dose of M ranging from 50-400 microg. At the PD(20)P(tc)O2, significant changes in Rint(L) and Rint(EI) (sensitivity index (SI) > or = 2) were found in 79% and 63% of children, respectively. We conclude that: 1) M challenge using P(tc)O2 is safe in young children; and 2) our findings are not in favor of the use of Rint as the only indicator of bronchial reaction in young children during M challenge.