Respiratory changes in parasternal intercostal intramuscular pressure

In an attempt to obtain insight in the forces developed by the parasternal intercostal muscles during breathing, changes in parasternal intramuscular pressure (PIP) were measured in 14 supine anesthetized dogs using a microtransducer method. In six animals, during bilateral parasternal stimulation a linear relationship between contractile force exerted on the rib and PIP was demonstrated (r greater than 0.95). In eight animals, during quiet active inspiration, substantial (55 +/- 11.5 cmH2O) PIP was developed. During inspiratory resistive loading and airway occlusion the inspiratory rise in PIP increased in proportion to the inspiratory fall in pleural pressure (r = 0.82). Phrenicotomy and vagotomy resulted in an increase in the inspiratory rise in PIP of 21% and 99%, respectively. During passive deflation, when the parasternal intercostals were passively lengthened, large rises (320 +/- 221 cmH2O) in intramuscular pressure were observed. During passive inflation intramuscular pressure remained constant or even decreased slightly (-8 +/- 25 cmH2O) as expected on the basis of the passive shortening of the muscles. PIP thus invariably increased when tension increased either actively or passively. From PIP it is clear that the parasternals exert significant forces on the ribs during respiratory maneuvers.     

Respiratory changes in parasternal intercostal length

In an attempt to understand the role of the parasternal intercostals in respiration, we measured the changes in length of these muscles during a variety of static and dynamic respiratory maneuvers. Studies were performed on 39 intercostal spaces from 10 anesthetized dogs, and changes in parasternal intercostal length were assessed with pairs of piezoelectric crystals (sonomicrometry). During static maneuvers (passive inflation-deflation, isovolume maneuvers, changes in body position), the parasternal intercostals shortened whenever the rib cage inflated, and they lengthened whenever the rib cage contracted. The changes in parasternal intercostal length, however, were much smaller than the changes in diaphragmatic length, averaging 9.2% of the resting length during inflation from residual volume to total lung capacity and 1.3% during tilting from supine to upright. During quiet breathing the parasternal intercostals always shortened during inspiration and lengthened during expiration. In the intact animals the inspiratory parasternal shortening was close to that seen for the same increase in lung volume during passive inflation and averaged 3.5%. After bilateral phrenicotomy, however, the parasternal intercostal shortening during inspiration markedly increased, whereas tidal volume diminished. These results indicate that 1) the parasternal intercostals in the dog are real agonists (as opposed to fixators) and actively contribute to expand the rib cage and the lung during quiet inspiration, 2) the relationship between lung volume and parasternal length is not unique but depends on the relative contribution of the various inspiratory muscles to tidal volume, and 3) the physiological range of operating length of the parasternal intercostals is considerably smaller than that of the diaphragm.(ABSTRACT TRUNCATED AT 250 WORDS)     

Respiratory and postural changes in intercostal muscle length in supine dogs

In an attempt to assess the physiological function(s) of the external (E) and internal interosseous (I) intercostal muscles, we measured the changes in intercostal muscle length during spontaneous breathing, during passive inflation, and during passive rotation of the trunk. Studies were performed on 46 muscles from 16 supine anesthetized dogs, and changes in muscle length were assessed by sonomicrometry. The changes were small during spontaneous breathing, whether before or after bilateral phrenicotomy, and the pattern was variable among animals and among interspaces. The E, however, particularly in the lower interspaces, often lengthened with inspiration, and the I, in particular in the upper interspaces, often shortened with inspiration. Only occasionally did the E and I in one interspace change in length in opposing directions. This was also true during passive inflation, where both E and I usually shortened in the upper interspaces and lengthened in the lower interspaces. By contrast, during passive rotation of the trunk, the E and I systematically changed in length in opposing directions, and either muscle could successively lengthen and shorten a substantial amount depending on the side of rotation. These results suggest that 1) the E and I in supine dogs do not behave as antagonistic muscles during moderate respiratory efforts; and 2) they do behave as antagonistic muscles during rotation of the trunk. A primary function of these muscles as rotators of the trunk, unlike breathing, may explain why two layers of intercostal muscles with different fiber orientation exist between the ribs.     

Voluntary hyperventilation changes recruitment order of parasternal intercostal motor units

The order of recruitment of single-motor units in parasternal intercostal muscles during inspiration was studied in normal human subjects during quiet breathing and voluntary hyperventilation. Electromyograms were recorded from the second and third intercostal spaces by means of bipolar fine wire electrodes. Flow at the mouth, volume, end-expired CO2, and rib cage and abdominal anterior-posterior diameters were monitored. Single-motor units were identified using criteria of amplitude and shape, and the time of first appearance of each unit in each inspiration was noted. Hyperventilation was performed with visual feedback of the display of rib cage and abdomen excursions, keeping the ratio of rib cage to abdominal expansion. Subjects were normocapnic in quiet breathing and developed hypocapnia during hyperventilation. Recruitment order was stable in quiet breathing, but in some cases was altered during voluntary hyperventilation. Some low threshold units that fired early in the breath in quiet breathing fired earlier at the beginning of a period of voluntary hyperventilation but progressively later in the breath as hyperventilation went on, whereas later firing units moved progressively toward the early part of inspiration. This suggests that different groups of motoneurons in the pool supplying parasternal intercostal muscles receive different patterns of synaptic input.     

The method for estimation of opsonic activity in sera of infants

Three methods for the estimation of opsonic activity in the sera of newborn children were tested. Two of them, based on the phagocytosis of opsonised bacteria labelled with radioactive phosphorus³²P as measured byin vivo blood clearance or uptake of bacteria in perfused isolated liver, were found to be unsuitable for long term dynamic study mainly because they do not permit the testing of series of samples. The third method (using isolated phagocytic cellsin vitro) permits the differentiation of the opsonic effect of complement and antibody and, furthermore, the firmness of the bond between microbes and phagocytes (which reflects the degree of opsonization) can be established. It was found that a 2-mercaptoethanol-resistant antibody, probably of the IgG type, was responsible for the opsonic activity of children's sera toEscherichia coli 083. Homologous antibody (toEscherichia coli 083) could be differentiated from beterologous antibody (toEscherichia coli 086) using the opsonic test only at low dilutions of sera. The combination of newborn piglet complement and antibody of children's sera yielded higher values of opsonic activity than either component separately.     

Interaction between left and right intercostal muscles in airway pressure generation.

The interactions between the different rib cage inspiratory muscles in the generation of pleural pressure remain largely unknown. In the present study, we have assessed in dogs the interactions between the parasternal intercostals and the interosseous intercostals situated on the right and left sides of the sternum. For each set of muscles, the changes in airway opening pressure (DeltaPao) obtained during separate right and left activation were added, and the calculated values (predicted DeltaPao) were then compared with the DeltaPao values obtained during symmetric, bilateral activation (measured DeltaPao). When the parasternal intercostals in one or two interspaces were activated, the measured DeltaPao was commonly greater than the predicted value. The difference, however, was only 10%. When the interosseous intercostals were activated, the measured DeltaPao was nearly equal to the predicted value. These observations strengthen our previous conclusion that the pressure changes produced by the rib cage inspiratory muscles are essentially additive. As a corollary, the rib cage can be considered as a linear elastic structure over a wide range of distortion.     

Lip pressure changes following lip repair in infants with unilateral clefts of the lip and palate

The present study was designed to quantitatively assess lip pressure changes following cleft lip repair in infants with unilateral cleft lip, alveolus, and palate. Lip pressure measurements were taken using an electronic transducer system developed especially for this study. Lip pressure was monitored from 3 months (preoperatively) through 2 years of age in cleft and normal control children. Findings from the present study confirm the hypothesis that lip repair in infants with unilateral cleft lip and palate significantly increases lip pressure and that increased lip pressure remains significantly higher than in normal control children for the 2-year duration of the study. Thus increased lip pressure when the palate is unrepaired has to be considered as a factor modulating subsequent craniofacial growth.     

Formula and scale for body surface area estimation in high-risk infants

Advances in medical technology and the health sciences have lead to a rapid increase in the prevalence and morbidity of high-risk infants with chronic or permanent sequels such as the birth of early preterm infants. A suitable formula is therefore needed for body surface area (BSA) estimation for high-risk infants to more accurately devise therapeutic regimes in clinical practice. A cohort study involving 5014 high-risk infants was conducted to develop a suitable formula for estimating BSA using four of the existing formulas in the literature. BSA of high-risk infants was calculated using the four BSA equations (Boyd-BSA, Dubois-BSA, Meban-BSA, Mosteller-BSA), from which a new calculation, Mean-BSA, was arithmetically derived as a reference BSA measure. Multiple-regression was performed using nonlinear least squares curve fitting corresponding to the trend line and the new equation, Neo-BSA, developed using Excel and SPSS 17.0. The Neo-BSA equation was constructed as follows: Neo-BSA = 5.520 x W(0.5526) x L(0.300). With the assumption of the least square root relation between weight and length, a BSA scale using only weight was fabricated specifically for clinical applications where weight is more available in high-risk infant populations than is length. The validity of Neo-BSA was evaluated against Meban-BSA, the best of the four equations for high-risk infants, as there is a similarity of subjects in the two studies. The other formulas revealed substantial variances in BSA compared to Neo-BSA. This study developed a new surface area equation, Neo-BSA, as the most suitable formula for BSA measurement of high-risk infants in modern-day societies, where an emerging population of newborns with shorten gestational ages are becoming more prevalent as a result of new advances in the health sciences and new development of reproductive technologies. In particular, a scale for 400-7000 g body weight babies derived from the Neo-BSA equation has the clinical advantage of using only weight as a measurement, since length is often not feasible as a measurement due to the newborn's body posture. Further studies are required to confirm our findings for the application of Neo-BSA and the BSA scale (based on weight) for various populations and ethnicities under different clinical conditions.