Abdominal Ventilation Research Articles

Intermittent Abdominal Pressure Ventilation: An Alternative for Respiratory Support.

Intermittent abdominal pressure ventilation is a positive pressure ventilation technique that works with abdominal compressions. It has been known since 1938; however, for many years, it was out of production. In recent years, a new device has been produced that has captured the attention to this old respiratory support technique. We considered eight patients with respiratory failure secondary to a neuromuscular disease (congenital myopathy, Duchenne dystrophy, and amyotrophic lateral sclerosis) intolerant to daytime noninvasive ventilation (NIV). IAPV was proposed as an alternative to NIV. We performed baseline and post-IAPV respiratory function assessment. All patients, two years later, are still using intermittent abdominal ventilation. Intermittent positive abdominal mechanical ventilation can be a valid alternative to noninvasive mechanical ventilation with a nasal or face mask. It improves gas exchange, symptoms, and quality of life, decreases the incidence of pneumonia, and can avert the need for intubation and tracheotomy.

Feedforward discharges couple the singing central pattern generator and ventilation central pattern generator in the cricket abdominal central nervous system

We investigated the central nervous coordination between singing motor activity and abdominal ventilatory pumping in crickets. Fictive singing, with sensory feedback removed, was elicited by eserine-microinjection into the brain, and the motor activity underlying singing and abdominal ventilation was recorded with extracellular electrodes. During singing, expiratory abdominal muscle activity is tightly phase coupled to the chirping pattern. Occasional temporary desynchronization of the two motor patterns indicate discrete central pattern generator (CPG) networks that can operate independently. Intracellular recordings revealed a sub-threshold depolarization in phase with the ventilatory cycle in a singing-CPG interneuron, and in a ventilation-CPG interneuron an excitatory input in phase with each syllable of the chirps. Inhibitory synaptic inputs coupled to the syllables of the singing motor pattern were present in another ventilatory interneuron, which is not part of the ventilation-CPG. Our recordings suggest that the two centrally generated motor patterns are coordinated by reciprocal feedforward discharges from the singing-CPG to the ventilation-CPG and vice versa. Consequently, expiratory contraction of the abdomen usually occurs in phase with the chirps and ventilation accelerates during singing due to entrainment by the faster chirp cycle.

Which treatments for the hyperventilation syndrome in adults?

The hyperventilation syndrome is a complex entity whose management is poorly codified. A Cochrane review in 2013 [1] highlighted the lack of proof in the treatment of this disease. The aim of this presentation is to expose the different options used in hyperventilation syndrome and to discuss their efficacy. We performed a narrative review in Pubmed, Science direct and clinical trials, with the keyword “hyperventilation syndrome”, “Dysfunctional breathing”, “breathing exercise”, “physical therapy”, “rehabilitation”, “treatment”, without limitation of date. Fifteen articles were selected. Among them, three studies about drug treatment and the others about non-pharmacological approaches. Among the last ones, a re-educational approach based on abdominal ventilation and regulation of the ventilatory rate, and an educative approach seems to be the most effective. Methodological biases did not permit a conclusion on the efficacy of these treatments. No study was done to explore the efficacy of pulmonary rehabilitation. A recent study was proposed on clinical trials to explore the nasal ventilation as a therapeutic modality. Teaching abdominal ventilation and respiratory rate regulation, associated with a personalized therapeutic education, seems to be a pertinent management approach. Other clinical studies should explore this issue.

Intricate but tight coupling of spiracular activity and abdominal ventilation during locust discontinuous gas exchange cycles.

Discontinuous gas exchange (DGE) is the best studied among insect gas exchange patterns. DGE cycles comprise three phases, which are defined by their spiracular state: closed, flutter and open. However, spiracle status has rarely been monitored directly; rather, it is often assumed based on CO2 emission traces. In this study, we directly recorded electromyogram (EMG) signals from the closer muscle of the second thoracic spiracle and from abdominal ventilation muscles in a fully intact locust during DGE. Muscular activity was monitored simultaneously with CO2 emission, under normoxia and under various experimental oxic conditions. Our findings indicate that locust DGE does not correspond well with the commonly described three-phase cycle. We describe unique DGE-related ventilation motor patterns, coupled to spiracular activity. During the open phase, when CO2 emission rate is highest, the thoracic spiracles do not remain open; rather, they open and close rapidly. This fast spiracle activity coincides with in-phase abdominal ventilation, while alternating with the abdominal spiracle and thus facilitating a unidirectional air flow along the main trachea. A change in the frequency of rhythmic ventilation during the open phase suggests modulation by intra-tracheal CO2 levels. A second, slow ventilatory movement pattern probably serves to facilitate gas diffusion during spiracle closure. Two flutter-like patterns are described in association with the different types of ventilatory activity. We offer a modified mechanistic model for DGE in actively ventilating insects, incorporating ventilatory behavior and changes in spiracle state.

The transition from water to air in aeshnid dragonflies is associated with a change in ventilatory responses to hypoxia and hypercapnia

Dragonflies are amphibiotic, spending most of their lives as aquatic nymphs before metamorphosing into terrestrial, winged imagoes. Both the nymph and the adult use rhythmic abdominal pumping movements to ventilate their gas exchange systems: the nymph tidally ventilates its rectal gill with water, while the imago pumps air into its tracheal system through its abdominal spiracles. The transition from water to air is known to be associated with changes in both respiratory chemosensitivity and ventilatory control in vertebrates and crustaceans, but the changes experienced by amphibiotic insects have been poorly explored. In this study, dragonfly nymphs (Anax junius) and imagoes (Anax junius and Aeshna multicolor) were exposed to hypoxia and hypercapnia while their abdominal ventilation frequency and amplitude was recorded. Water-breathing nymphs showed a significant increase in abdominal pumping frequency when breathing hypoxic water (<10 kPa O2), but no strong response to CO2, even in severe hypercapnia (up to 10 kPa CO2). In contrast, both species of air-breathing imago increased their abdominal pumping amplitude when exposed to either hypoxia or hypercapnia, but did not show any significant increase in frequency. These results demonstrate that aquatic dragonfly nymphs possess a respiratory sensitivity that is more like other water breathing animals, being sensitive to hypoxia but not hypercapnia, while their air-breathing adult form responds to both respiratory challenges, like other terrestrial insects. Shifting from ventilating a rectal gill with water to ventilating a tracheal system with air is also associated with a change in how abdominal ventilation is controlled; nymphs regulate gas exchange by varying frequency while imagoes respond by varying amplitude.

Randomized controlled trial on minimally invasive versus open esophagectomy for esophageal cancer: short and long-term outcomes

The incidence of esophageal cancer has been increasing over the past two decades (1). Despite improvement in treatment options, such as chemotherapy and radiotherapy, esophagectomy with regional lymph node dissection remains the mainstay of curative modality for patients with localized thoracic esophageal cancer. Morbidity is a major concern during the follow-up period because of the invasive nature of esophagectomy and the complex operative procedures involved. Long thoracic and abdominal incisions and one-lung ventilation during esophagectomy are thought to be partly responsible for the high surgical invasiveness and subsequent respiratory complications of this procedure. On the other hand, a thoracoscopic approach, which could reduce the length of skin incision, has been attracting attention as a minimally invasive esophagectomy (MIE). By the late 1990s, several surgeons had performed and demonstrated the safety and feasibility of the technique (2,3). After these exploratory investigations, reports from large single-center studies began to reveal improvements in the surgical outcomes of MIE (4). Meta-analyses using individual institutional reports showed that compared with open esophagectomy (OE), MIE was associated with less operative blood loss, shorter length of intensive care unit and hospital stays, and reduced incidence of postoperative respiratory complications (5,6). On the other hand, results from several nationwide database analyses have been disappointing and demonstrated that MIE did not reduce postoperative respiratory complications and had higher reoperation or reintervention rates (7,8). However, these unexpected results of the nationwide database analyses may be attributable to the inclusion of a wide range of patients, surgeons, and hospitals. Therefore, we have recognized the necessity of a prospective study to determine the lower invasiveness and improved quality of life (QOL) associated with MIE, compared with OE.

Sublethal doses of imidacloprid decreased size of hypopharyngeal glands and respiratory rhythm of honeybees in vivo

Most studies that have shown negative sublethal effects of the pesticide imidacloprid on honeybees concern behavioral effects; only a few concern physiological effects. Therefore, we investigated sublethal effects of imidacloprid on the development of the hypopharyngeal glands (HPGs) and respiratory rhythm in honeybees fed under laboratory conditions. We introduced newly emerged honeybees into wooden mesh-sided cages and provided sugar solution and pollen pastry ad libitum. Imidacloprid was administered in the food: 2 μg/kg in the sugar solution and 3 μg/kg in the pollen pastry. The acini, the lobes of the HPGs of imidacloprid-treated honeybees, were 14.5 % smaller in diameter in 9-day-old honeybees and 16.3 % smaller in 14-day-old honeybees than in the same-aged untreated honeybees; the difference was significant for both age groups. Imidacloprid also significantly affected the bursting pattern of abdominal ventilation movements (AVM) by causing a 59.4 % increase in the inter-burst interval and a 56.99 % decrease in the mean duration of AVM bursts. At the same time, the quantity of food consumed (sugar solution and pollen pastry) per honeybee per day was the same for both treated and untreated honeybees.

Regulation of gas exchange and haemolymph pH in the cockroach Nauphoeta cinerea

Ventilatory control of internal CO(2) plays an important role in regulating extracellular acid-base balance in terrestrial animals. While this phenomenon is well understood among vertebrates, the role that respiration plays in the acid-base balance of insects is in need of much further study. To measure changes in insect haemolymph pH, we implanted micro pH optodes into the haemocoel of cockroaches (Nauphoeta cinerea). They were then exposed to normoxic, hypoxic, hyperoxic and hypercapnic atmospheres while their haemolymph pH, VCO(2) and abdominal ventilation frequency were measured simultaneously. Intratracheal O(2) levels were also measured in separate experiments. It was found that cockroaches breathing continuously control their ventilation to defend a haemolymph pH of 7.3, except under conditions where hypoxia (<10% O(2)) induces hyperventilation, or where ambient hypercapnia is in excess of haemolymph (>1% CO(2)). In contrast, intratracheal O(2) levels fluctuated widely, but on average remained above 15% in normoxic (21% O(2)) atmospheres. Decapitation caused the cockroaches to display discontinuous gas exchange cycles (DGCs). The alternating periods of ventilation and apnoea during DGCs caused haemolymph pH to fluctuate by 0.11 units. Exposure to hypoxia caused haemolymph pH to increase and initiated brief bouts of spiracular opening prior to the active ventilation phase. The spontaneous occurrence of DGCs in decapitated cockroaches indicates that central pattern generators in the thoracic and abdominal ganglia generate the periodic gas exchange pattern in the absence of control from the cephalic ganglion. This pattern continues to maintain gas exchange, but with less precision.

Respiration of resting honeybees

The relation between the respiratory activity of resting honeybees and ambient temperature ( T a) was investigated in the range of 5–40 °C. Bees were kept in a temperature controlled flow through respirometer chamber where their locomotor and endothermic activity, as well as abdominal ventilatory movements was recorded by infrared thermography. Surprisingly, true resting bees were often weakly endothermic (thorax surface up to 2.8 °C warmer than abdomen) at a T a of 14–30 °C. Above 33 °C many bees cooled their body via evaporation from their mouthparts. A novel mathematical model allows description of the relationship of resting (standard) metabolic rate and temperature across the entire functional temperature range of bees. In chill coma (<11 °C) bees were ectothermic and CO 2 release was mostly continuous. CO 2 release rate (nl s −1) decreased from 9.3 at 9.7 °C to 5.4 at 5 °C. At a T a of >11 °C CO 2 was released discontinuously. In the bees’ active temperature range mean CO 2 production rate (nl s −1) increased sigmoidally (10.6 at 14.1 °C, 24.1 at 26.5 °C, and 55.2 at 38.1 °C), coming to a halt towards the upper lethal temperature. This was primarily accomplished by an exponential increase in gas exchange frequency (0.54 and 3.1 breaths min −1 at 14.1 and 38.1 °C) but not in released CO 2 volume per respiratory cycle (1487 and 1083 nl cycle −1 at 14.1 and 38.1 °C). Emission of CO 2 bursts was mostly (98%) accompanied by abdominal ventilation movements even in small CO 2 bursts. Larger bursts coincided with a longer duration of active ventilation. An increased amount of CO 2 expelled per unit time of ventilation indicates a higher efficiency of ventilation at high ambient temperatures.

Audit of Intrathecal, Epidural and Intravenous Analgesia for Abdominal Surgery

Background: Many studies have compared epidural and intravenous postoperative analgesia. To date there are no studies comparing intrathecal with epidural and intravenous regimes. Aim: To audit standard postoperative intrathecal (incorporating midazolam), epidural and systemic intravenous analgesic regimes used at Monash Medical Centre. Method: This was a prospective nonblinded study conducted over 9 months. Data was collated for 15 patients of each of the following regimes, identified through the Acute Pain Service. • Intrathecal infusion of Morphine 10 mcg + Midazolam 100 mcg + Bupivacaine 0.5 mg per ml at 1–2 ml/hr • Epidural infusion of Fentanyl 2 mcg/ml + Bupivacaine 1.25 mg/ml at 6–12 ml/hr • Intravenous Morphine Patient Controlled Analgesia 1 mg boluses + /− background infusion and Ketamine infusion at 0.1–0.2 mg/kg/hr Inclusion criteria were: patients conversant in English and over 60 years of age, having open abdominal surgery and postoperative ventilation less than 24 hours. Results: Statistical data analysis showed a significant difference between the groups in the median number of calls to the pain service: Data on pain scores, postoperative haemodynamic stability and pyrexias were also notable: Conclusions: The intrathecal group trends towards better postoperative analgesia and less intervention required compared to epidural or intravenous regimes.

Monitoring of gas exchange cycles and ventilatory movements in the pine weevil Hylobius abietis: respiratory failures evoked by a botanical insecticide

AbstractThe large pine weevil, Hylobius abietis (L.) (Coleoptera: Curculionidae), is the most important insect pest of young coniferous plants. The implementation of new control methods requires not only a profound knowledge of the ecology and behaviour of the pest, but particularly of its physiology. Standard metabolic rate (SMR) and discontinuous gas exchange cycles (DGCs) were recorded in parallel with abdominal ventilation movements in adults of H. abietis using a differential electrolytic respirometer‐actograph. Quiescent weevils displayed DGCs of the constriction, flutter, and ventilation phases of the CFV type, while bursts of carbon dioxide were always accompanied by abdominal pumping movements, i.e., muscular ventilation in the closed subelytral cavity (SEC). In some beetles the C phase was absent and thus (C)FV cycles were recorded. In addition, at the beginning and often at the end of a burst, the SEC was rhythmically opened and closed by movements of the last abdominal segments. Continuous pumping movements and an absence of DGCs were signs of stress imposed by handling or by a new environment, even if the beetle was not moving. All individuals showed clear DGCs after recovering from handling and apparatus stress lasting 2–3 h. The results show that in the monitoring of DGCs, it is essential to determine whether they are of the constriction, flutter, and open phases (CFO), or the CFV subtype of the constriction, flutter, and burst (CFB) cycles. Use of our simple closed‐system respirometer enables non‐invasive simultaneous recording of SMR, oxygen uptake, DGCs, and active ventilation in H. abietis and other beetles.The topical application of adult H. abietis with sublethal doses of a botanical insecticide, NeemAzal T/S, caused essential respiratory failures: cyclic gas exchange was lost and irregular pumping movements appeared. In the treated beetles normal DGCs did not resume.

Accessory hemolymph pump in the mesothoracic legs of locusts, (Schistocerca gregaria forskal) (Orthoptera, Acrididae)

An accessory pulsatile organ located in the mesothoracic legs pumps hemolymph towards the tip of the leg ventrally and towards the body near the dorsal side. It consists of a muscle attached to the ventral side of the trochanter and to the central region of a transverse connective tissue diaphragm located at the trochanter-femur border. The diaphragm has a ventral outlet that permits efferent hemolymph flow through a narrow femoral sinus. A second dorsal outlet allows the afferent countercurrent back to the thorax through a separate hemolymph channel. During abdominal ventilation, the pumping rhythm of the leg fn2 fn2 heart muscle fibers, mn, main nerve of the leg, m104, leg–heart muscle, tr, trachea, N5, main leg nerve, 5B2a, terminal nerve to the leg–heart, m107b, tibial flexor muscle. heart is neurally synchronized with abdominal ventilation. Expiratory pressure expands tracheal air sacs in the ventral trochanter and helps driving hemolymph out of this space. In idle periods of resting ventilation, an autonomous myogenic rhythm of the leg–heart can maintain hemolymph circulation in the mesothoracic leg without neural control.

Current developments in c ar diopulmonary resuscitation

As veterinary surgeons, we must all deal, on occasion, with an animal who has suffered a cardiac arrest. This article reviews the recent literature concerning cardiopulmonary resuscitation (CPR) and examines the suggestions recently put forward by the American Heart Association in their improved resuscitation protocol. These protocol modifications have been shown experimentally and clinically to improve cerebral and myocardial haemodynamics during closed chest cardiac massage. The ultimate goal of CPR must be not merely to resuscitate the patient in the short term, but to promote complete neurological recovery in the longer term. Prompt recognition of cardiac arrest and the immediate initiation of resuscitative measures play a major contributing role in a favourable neurological outcome. In addition to the familiar ABC system of basic cardiac life support, the use of a high dose adrenaline (0–2 mg/kg) is proposed as the best first line drug treatment in the arrested patient. This can be accompanied by abdominal wrapping and synchronous ventilation and chest compressions to optimise cerebral and myocardial blood flow. Calcium chloride and sodium bicarbonate should no longer be included in the early resuscitative efforts.

Effets respiratoires du propofol mesurés par la spirométrie indirecte

The effects of a continuous steady rate infusion of propofol on spontaneous ventilation were studied in eight unpremedicated ASA 1 male patients. All were non smokers, aged 29 ± 8 years, and weighed 67 ± 9 kg. After an initial 1 mg · kg −1 bolus, they received 10 mg · kg −1 · h −1 propofol for 10 min, followed by 8 mg · kg −1 · h −1 for a further 10 min, and then 6 mg · kg −1 · h −1 during the whole study period. Endotracheal intubation was carried out using lidocaine for local anaesthesia. Spontaneous ventilation was assessed during three periods of five minutes : in the awake subject, using indirect spirometry (measurement of variations in chest circumference) and direct spirometry separately, and then, in the anaesthetized subject, using both methods simultaneously. This study aimed : a) to compare the results obtained with the two methods, b) to characterize the effects of propofol anaesthesia on chest wall mechanics using the partitioning of ventilation between rib cage and abdomen provided by the non-invasive method, and c) to assess abdominal compliance by means of a gastric balloon catheter. There was an increase in rib cage ventilation in the awake state, induced by the apparatus for direct spirometry (mouth piece, nose clip). This explained that the ventilatory depression induced by propofol anaesthesia was more pronounced when measured by the direct method. The major determinant of this depression was a shortened inspiratory time, and, to a lesser extent, a decreased mean inspiratory flow rate. By contrast to inhalational anaesthesia, rib cage ventilation was preserved during propofol anaesthesia. The decrease in abdominal ventilation was partly related to a lowered abdominal compliance, suggesting recruitment of the abdominal muscles.

A Temperature-Induced Switch From Diffusive to Convective Ventilation in the Honeybee

ABSTRACT It is known that many insects emit CO2 in widely spaced ‘bursts’ or discontinuous ventilation events, usually characterized by active abdominal ventilation. We describe the discontinuous CO2 emission characteristics of the honeybee (Apis mellifera ligustica Spinola), and utilize its ‘chill coma’ temperature threshold (12°C) to effect transitions from continuous, diffusive to discontinuous, convective ventilation regimes. Increasing temperature abruptly switched the dynamics of ventilation from diffusive and continuous (⩽11 °C) to convective and discontinuous (&amp;gt;12°C). The ventilation cycle frequency was 7.84 mHz and CO2 output per ventilation event (burst phase) was 1.56μl neither variable was temperaturedependent in the range 12–15 °C. The rate of CO2 emission did not change significantly in the range 7–15 °C, possibly owing to increased membrane leakiness at lower temperatures. At 15°C, honeybee metabolic rate (2.69 W kg−1, mean mass 0.094 g) is similar to that of other similarly sized insects capable of significant endothermy.

Gating of ventilatory activity in the cave‐cricket, Troglophilus cavicola

ABSTRACT. The rhythm of ‘abdominal respiratory movements’ (ARMs) in partly tethered cave‐crickets was recorded via correlated hindleg movements associated with abdominal ventilation, and analysed with respect to postural changes (cricket placed horizontally or vertically) under the following stimulus regimes: touch stimuli of constant duration but varying rates were presented to the hind legs independently of the ARM rhythm; touch stimuli with constant delays were triggered by the previous ARM; and light stimuli were presented, preceding the touch stimuli. With constantly spaced touch stimuli, on‐ and off‐effects are visible in the number of ARMs per time unit and this is more pronounced in the horizontal than in the vertical position. Continuous modulations of ARMs patterning (tonic effects) are revealed in free run cycles which are intercalated in rhythmic driving series: at intertouch lengths of 20 s such free run cycling is faster under vertical than under horizontal conditions. With the vertical stance it is delayed by additional light. Even the kind of vertical orientation causes tonic effects. Thus crickets that face downward exhibit a slower ARM rhythm than those facing upward. Under entrainment to constantly delayed touches, two parameters of ARM rhythm (‘basic period’ and ‘consecutive period’) were studied to elucidate the hypothetical cycling of the pacemaker under different stances. Under horizontal conditions the ‘basic periods’ are shortened if the delay of touch does not exceed 0.2 periods of free run cycling. However, in the vertical position, the ‘basic periods’ are prolonged. With delay times exceeding 0.5 periods of free run cycle, the ‘consecutive periods’ are lengthened if the cricket is oriented vertically, but remain unaffected under horizontal conditions. On the basis of these results, a model for resetting and sensory modulation of ARM control is presented.

Regional Relationship Between Changes of Electrical Impedance and Diameter of the Thorax During Ventilation

The relationship between the electrical impedance fluctuation (ΔZ) and the chest cage movement(ΔTD) associated with ventilation on either upper and lower zones of the hemithorax or the bilateral sides of the thorax were discussed in the range of the vital capacity which was measured by the conventional spirometry (ΔV) in fifteen normal adults. The ventilatory variation of the impedance in the two regions were smaller at the top and larger at the bottom. The dorso-ventral diameter changes, ΔZ/ΔV and ΔTD/ΔV had a similar tendency. Despite correlatibe change between ΔZ and ΔTD in the normal adults, the impedance fluctuated without evident TD change in the abdominal ventilation, and the chest cage moved without evident impedance change in the area under which thoracoplasty was carried out. These results suggest that the ventilatory impedance variation is evoked not by the chest wall movement but by distribution of the inspired air into the region under the electrode, and the impedance method may detect the regional ventilation evidently.

Rhythmic activity in the insect nervous system: Thoracic ventilation in non-flying beetles

Pumping movements of the head, prothorax, and metathorax in phase with abdominal ventilation are described in some Prionine beetles. Metathoracic ventilation is produced by a pleurosternal muscle which closes the pleurosternal hinge in phase with each abdominal expiratory stroke. Other thoracic muscles may be temporarily coupled to the ventilatory rhythm and this may improve the effectiveness of the ventilation.

The respiratory energetics of two species of stream caddis fly larvae in relation to water flow

1. 1. Water current caused increases in respiration and locomotor activity for Pycnopsyche guttifer and P. lepida which corresponded to their respective environmental current regimes. 2. 2. Ventilation rates increased as current speed decreased, suggesting that abdominal ventilation compensates for low stream velocities. 3. 3. The differences between active and inactive rates of oxygen consumption in relation to velocity allowed the amount of oxygen required for minimal and active metabolic needs to be determined.

The supply of oxygen to the active flight muscles of some large beetles.

ABSTRACT Measurements of the wing-beat frequency, wing-stroke amplitude and stroke plane and of abdominal ventilation have been made during the tethered flight of twenty-six species of beetles belonging to five families, mainly in Uganda. Abdominal ventilation is weak or absent in all species of Cerambycidae, Elateridae and Anthribidae examined in flight. The tracheal system in these families is characterized by the complete absence of air sacs, and in larger species by the presence of four giant trunks running through the metathorax between spiracles 2 and 3 and forming the primary supply to the flight muscles. Abdominal ventilation is strong during the flight of all species over o·6 g. in weight of the Scarabaeidae and Buprestidae which were examined. Their tracheal systems contain an abundance of air sacs while giant trunks are absent. Measurements of the thoracic volume changes which accompany each wing beat show that the amount of air which can be pumped in this way increases in larger Cerambycidae per second per gram as compared with small species. Large Cerambycidae pump more per gram than Scarabaeidae of comparable size. During the flight of the cerambycid Petrognatha the thoracic pump exchanges 540 μ1. air/sec./g. Its action is mainly on the compressible secondary tracheae. In a wind speed of 5 m./sec. 1050 μ1. air/sec./g. are driven through the four giant trunks, entering through spiracle 2 and leaving from spiracle 3. The trunks are stout-walled and probably unaffected by the thoracic pump.