Browsing by Author "Maree, D."

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Compliance of the respiratory system as a predictor for successful extubation in very-low-birth-weight infants recovering from respiratory distress syndrome
    (Health & Medical Publishing Group, 1999) Smith, J.; Pieper, C. H.; Maree, D.; Gie, R. P.
    Objective. To develop additional criteria to predict for successful extubation of very-low-birth-weight infants recovering from respiratory distress syndrome. Design. Prospective study. Setting. Neonatal intensive care unit at a university teaching hospital. Interventions. Infants ready for extubation according to clinical, ventilatory and blood gas criteria were studied. Before extubation, tidal volume (Vt), minute ventilation, respiratory rate/Vt and mean inspiratory flow were measured during two different ventilatory settings: (i) during intermittent mandatory ventilation (IMV); and (ii) while breathing spontaneously with endotracheal continuous positive airway pressure (CPAP). Tidal volume was obtained through electronically integrated flow measured by a hot-wire anemometer. Total respiratory compliance (Crs) was determined during IMV and was derived from the formula Vt/PIP-PEEP, where the difference between peak inspiratory pressure (PIP) and positive end-expiratory pressure (PEEP) represented the ventilator inflation pressure. Measurements and main results. Each of 49 infants was studied once before extubation. 33 infants (67%) were successfully extubated and 16 (32.6%) required reintubation. Infants in the success and failure groups were matched for gestation, post-conceptional age, study weight and methylxanthine therapy at the time of study. Successful extubation was associated with a higher mean absolute Crs value (ml/cm H2O) specific Crs value (standardised for body length; ml/cm H2O/cm) compared with infants in whom extubation failed (0.67 v. 0.46; P = 0.01 and 0.018 v. 0.014; P = 0.03, respectively). Analysis of ROC curves detected thresholds for Crs (0.5 ml/cm H2O) and Vt (7 ml) for predicting successful extubation. An absolute Crs value 0.5 ml/cm H2O or more improved the likelihood of successful extubation when compared with clinical/ventilator and blood gas criteria. The likelihood of successful extubation was 81% if the Crs value was ≥ 0.5 ml/cm H2O. A tidal volume of 7 ml or more was less sensitive in contributing to successful extubation (sensitivity 69%). The major causes for extubation failure included atelectasis (diffuse and/or localised) and the presence of a patent ductus arteriosus. Conclusions. In addition to following very precise ventilatory criteria for extubation, we found that bedside measurement of total respiratory system compliance added to the likelihood of extubation success in infants recovering from respiratory distress syndrome. Prospective studies are needed to validate the findings of this study.
  • Thumbnail Image
    Item
    High-frequency oscillatory ventilation - rescue treatment for infants with severe respiratory failure
    (Health & Medical Publishing Group, 1998) Smith, J.; Pieper, C. H.; Kirsten, G. F.; Maree, D.; Van Zyl, J.; Pretorius, M. L.
    Objective. To assess the efficacy of high-frequency oscillatory ventilation (HFOV) as a rescue mode of therapy in newborn infants with severe respiratory failure poorly responsive or unresponsive to conventional ventilation and supportive management. Design. Prospective, descriptive clinical study. Setting. Tertiary care neonatal intensive care unit. Patients and methods. All infants with radiographic evidence of diffuse bilateral lung disease and failure to maintain adequate blood gas values while receiving conventional support were offered HFOV. Intervention. HFOV, utilising a high-pressure/volume strategy. Outcome variables. Improvement in arterial/alveolar oxygen tension ratio (a/APO2) of the infants subsequent to their transferral to HFOV; survival rate; and outcome of infants weighing more than 2 000 g who met criteria for extracorporeal membrane oxygenation (ECMO). Identifying the infants who met ECMO entry criteria allowed the success of HFOV to be compared with that of ECMO, the 'standard' treatment for infants considered unventilatable. Neonatal complications such as bronchopulmonary dysplasia, intraventricular haemorrhage and air leaks were documented. Results. Conventional support failed in 34 consecutive infants; they were transferred to HFOV at a mean postnatal age of 30 hours. Their respiratory diagnoses included respiratory distress syndrome (RDS) (N = 19), neonatal 'adult respiratory distress syndrome' (ARDS) (N = 3) and meconium aspiration syndrome (MAS) (N = 12). Owing to similarities in the underlying pathophysiology, RDS and ARDS were grouped together for the purposes of analysis. After starting HFOV the a/APO2 had significantly improved (P < 0.05) by 6 hours in the RDS group and by 12 hours in the infants with MAS. This improvement was sustained throughout the first 48 hours of HFOV. Twenty-six (76%) of the infants ultimately survived. Among those who met the criteria for ECMO (N = 13), the survival rate was 92%. Air leaks occurred on HFOV in 6 infants, 3 each in the MAS and RDS groups. Bronchopulmonary dysplasia was diagnosed in 6 (40%) of the 15 RDS infants and in 2 (18%) of the 11 infants with MAS. Eight infants died, 3 following nosocomial sepsis (Pseudomonas sp.), 3 due to extensive air leaks, 1 due to irreversible shock (unproven sepsis), and 1 due to ARDS. At a median age of 13.5 months the neurological development of 11 (5%) of 17 infants was normal; in 3 (18%) it was suspect and in 3 abnormal. Conclusions. The study demonstrates that a high-pressure/volume approach to HFOV is an effective mode of rescue ventilation for infants who present with severe respiratory failure caused by a variety of lung conditions during the neonatal period.
  • Thumbnail Image
    Item
    The utility of hand-held mobile spirometer technology in a resource-constrained setting
    (Health & Medical Publishing Group, 2019) Du Plessis, E.; Swart, F.; Maree, D.; Heydenreich, J.; Van Heerden, J.; Esterhuizen, T. M.; Irusen, E. M.; Koegelenberg, C. F. N.
    Background. Mobile phone-linked spirometry technology has been designed specifically for evaluating lung function at primary care level. The Air-Smart Spirometer is the first mobile spirometer accepted in Europe for the screening of patients with chronic respiratory diseases. Objectives. To prospectively assess the accuracy of the device in measuring forced expiratory volume in the first second (FEV1) and forced vital capacity (FVC) in a South African population, and to investigate the ability of the device to detect obstructive ventilatory impairment. Methods. A total of 200 participants were randomly assigned to perform spirometry with either the mobile spirometer connected to a smartphone or the desktop spirometer first, followed by the other. The FEV1/FVC ratio as well as the absolute FEV1 and FVC measurements were compared, using each participant as their own control. A Pearson correlation and Bland-Altman analysis were performed to measure the agreement between the two devices. We defined obstructive ventilatory impairment as FEV1/FVC <0.7 measured by desktop spirometry in order to calculate the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the Air-Smart Spirometer. Results. There was a strong correlation between the absolute FEV1 and FVC values and FEV1/FVC ratio measured with the mobile Air-Smart Spirometer and more conventional pulmonary function testing, with r=0.951, r=0.955 and r=0.898, respectively. The Air-Smart Spirometer had a sensitivity of 97.6%, specificity of 74.4%, PPV of 73.0% and NPV of 97.8% for obstructive ventilatory impairment. Conclusions. The mobile Air-Smart Spirometer compared well with conventional spirometry, making it an attractive and potentially affordable tool for screening purposes in a primary care setting. Moreover, it had a high sensitivity and NPV for obstructive ventilatory impairment.